Publishing type：Research paper (scientific journal)   Publisher：Institute of Electronics, Information and Communications Engineers (IEICE)  

DOI： 10.1587/transele.2020oms0008

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Publishing type：Research paper (scientific journal)  

Three different silver nanoprisms (AgNPrs) were combined and used as light-trapping materials in organic solar cells (OSCs). These mixed AgNPrs (M-AgNPrs) increased the photocarrier generation in the OSCs due to the broadband absorption, which was attributed to mutual multiple plasmonic excitations covering the entire visible light region. The M-AgNPrs were incorporated into a poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) hole-transport layer in the OSCs. The UV–vis spectra, atomic force microscope images and current density versus voltage curves of the fabricated devices were recorded at different loading concentrations of the M-AgNPrs. Finite-difference time-domain simulation, impedance spectroscopy, and measurement of incident photon-to-current efficiency of the devices confirmed the effect of the multiple plasmonic excitations. The results suggest that, in an optimum condition, the efficiency of the OSCs loaded with M-AgNPrs was 7.9% higher than the reference OSC.

DOI： 10.1016/j.jsamd.2021.02.007

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC  

We studied the effect of gold quantum dots (AuQDs)/grating-coupled surface plasmon resonance (GC-SPR) in inverted organic solar cells (OSCs). AuQDs are located within a GC-SPR evanescent field in inverted OSCs, indicating an interaction between GC-SPR and AuQDs' quantum effects, subsequently giving rise to improvement in the performance of inverted OSCs. The fabricated solar cell device comprises an ITO/TiO2/P3HT : PCBM/PEDOT : PSS : AuQD/silver grating structure. The AuQDs were loaded into a hole transport layer (PEDOT : PSS) of the inverted OSCs to increase absorption in the near-ultraviolet (UV) light region and to emit visible light into the neighbouring photoactive layer, thereby achieving light-harvesting improvement of the device. The grating structures were fabricated on P3HT:PCBM layers using a nanoimprinting technique to induce GC-SPR within the inverted OSCs. The AuQDs incorporated within the strongly enhanced GC-SPR evanescent electric field on metallic nanostructures in the inverted OSCs improved the short-circuit current and the efficiency of photovoltaic devices. In comparison with the reference OSC and OSCs with only green AuQDs or only metallic grating, the developed device indicates enhancement of up to 16% power conversion efficiency. This indicates that our light management approach allows for greater light utilization of the OSCs because of the synergistic effect of G-AuQDs and GC-SPR.

DOI： 10.1098/rsos.210022

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

A practical technique for determining the length of a silicon nanowire (SiNW) array is reported by the analysis of reflected images from a smartphone camera. The SiNW array was prepared by electroless chemical etching and its length controlled by the etching time of a Si wafer. The average lengths for the SiNW array were characterized by scanning electron microscopy. The relationship between the reflection spectrum and the length of the SiNW array was investigated. The ratio of percent reflectance from 900 to 550 nm exponentially increased from 1.8 +/- 0.1 to 22.2 +/- 1.3 when the average length increased from 184 +/- 12 to 1237 +/- 23 nm. Optical sensing for characterization of the length of SiNW was further developed into a simple and practical technique using a smartphone camera as a detector. A 3D printed tool was assembled to the smartphone to control the light path and the reflected image of the SiNW array was acquired. The reflected intensity ratio obtained from the reflected images with long pass to short pass filters increased analogously to the spectroscopic results. This optical-sensing-based smartphone showed simple and rapid detection for determining the lengths of a SiNW array and a SiNW array coated with a polymer film. This platform is compact and capable of on-site detecting and is promising for the characterization of reflective materials.

DOI： 10.1080/10739149.2021.1887889

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

The method for fabricating a grating prism surface plasmon resonance (SPR) sensor chip was developed. The grating prism was 3D-printed by a stereolithography 3D printer and subsequently created a grating pattern by soft lithography. A gold film was thermally evaporated on the grating prism. Moreover, a liquid cell was 3D-printed and assembled into a gold-coated grating prism. To make the sensor chip compact and practical, a compatible prism holder was 3D-printed by a fused deposition model 3D printer. The SPR sensor chip was mounted on the rotation stage and the SPR spectrum was recorded by spectrometer. The SPR excitation of the sensor chip can be extended to the near-infrared region by creating a grating pattern on the prism surface. A gold-coated grating prism exhibited dual modes of SPR excitations, namely, prism-coupling SPR (PC-SPR) and grating-coupling SPR (GC-SPR). The dual-mode SPR excitation was observed at the incident angles of 45 degrees-80 degrees. When the incident angle increased, the SPR excitation of the PC-SPR mode exhibited a blue shift in the wavelength region of 480-690 nm, whereas the GC-SPR mode exhibited a red shift in the wavelength region of 670-770 nm. The surface plasmon (SP) dispersion obtained from the dual-mode SPR configuration confirmed observable PC-SPR (which corresponded to + SP0 of the gold-resin interface) and GC-SPR (which corresponded to -SP+1 of the gold-air interface), which could be excited from the developed substrate. The refractive index sensitivities of the PCSPR and GC-SPR modes were 2924.4 and 414.9 nm RIU-1, respectively. The SPR excitations of the sensor chip exhibited a simultaneous shift when the local refractive index of the materials adjacent to the gold-coated grating prism surface was changed, especially the material that had overlapping light absorption at the SPR excitation wavelength. Using this fabrication process, the prism is designed and then printed; moreover, the grating pattern on the prism surface can be employed to tune the SPR excitation wavelength of the sensor chip for the versatility and broad perspective of the optical sensing-based SPR. (C) 2020 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.aca.2020.12.027

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

In this work, we investigate surface plasmon field-enhanced fluorescence (SPF) emission from gold quantum dots (AuQDs) on a polyelectrolyte multilayer ultrathin film deposited onto an Al thin film. Polyelectrolyte layers of poly(diallyl dimethyl ammonium chloride) (PDADMAC) and poly(sodium 4-styrenesulfonate) (PSS) are deposited onto the Al surface using a layer-by-layer (LbL) adsorption technique. AuQDs are subsequently deposited onto the PDADMAC/PSS ultrathin films to study their fluorescence enhancement/quenching phenomenon, as monitored by SPF spectroscopy. The distance between the AuQDs and the Al thin film is controlled by the number of deposited PDADMAC/PSS LbL films. With increasing number of the PDADMAC/PSS bilayers, the fluorescence intensity of the AuQDs increases until the optimum distance between the AuQDs and Al layers is achieved. Moreover, silver nanoprisms (AgNPrs) are coated onto the AuQDs for H2O2 sensing. When the AgNPrs are present, a decrease in the fluorescence intensity of the AuQDs due to energy transfer from the AuQDs to the AgNPrs is observed. Recovery of the fluorescence intensity of the AuQDs is observed upon injection of a H2O2 solution, where the recovery of the intensity is proportional to the H2O2 concentration in the range from 1 pM to 100 nM and results from the oxidation reaction or etching of the AgNPrs. The fluorescence recovery is attributed to weakening of the quenching effect by a reduction in concentration of the AgNPrs. The proposed system exhibits strong potential for the development of H2O2 sensors.

DOI： 10.1007/s11468-021-01388-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

Several scientific works have reported the use of colloidal gold nanoparticle (AuNP) solutions as a colorimetric probe for creatinine detection. Nonetheless, urinary protein is one of the primary chemical components that can interfere with creatinine detection. In this work, we developed a colorimetric probe using AuNP colloidal solution to detect creatinine in the urine of proteinuria patients. A microchamber array was prepared to minimize the sample volume and was used to simultaneously perform spectral recording and image acquisition of several samples. The analyzed volume for each sample was 15 mu L. A camera coupled with liquid crystal tunable filters was used to record hyperspectral images, and the signals were then converted to localized surface plasmon resonance (LSPR) spectra. Color changes in the AuNP colloidal solution in the presence of varying concentrations of creatinine and human serum albumin (HSA) indicated different features and could be detected by a hyperspectral imaging technique. The relevant concentration ranges of creatinine and HSA were 5 - 200 and 50 - 250 mg dL(-1), respectively. Furthermore, a smartphone camera was adopted to record a color mapping image of the AuNP colloidal solution in the presence of creatinine and HSA at these concentration ranges. Contour plots of red and blue chromaticity levels from color mappings were produced, and 2D fitting equations obtained from these contour plots were adopted to determine the creatinine concentration in the urine of proteinuria patients. This practical technique can be used for screening and can be further developed as a household biosensing device for urinalysis.

DOI： 10.2116/analsci.20P235

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Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

DOI： 10.35848/1347-4065/abbfe6

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Other Link： https://iopscience.iop.org/article/10.35848/1347-4065/abbfe6/pdf

Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/15421406.2020.1741822

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The incorporation of metallic nanoobjects into devices allows to increase light harvesting, which increases the device performance. In this study, we used a combination of gold quantum dots and grating-coupled surface plasmon resonance (GCSPR) to improve the performance of organic solar cells (OSCs) with a poly(3-hexylthiophene-2,5-diyl) (P3HT):[6,6]-phenyl C-61 butyric acid methyl ester (PCBM) photoactive layer. Gold quantum dots with a green fluorescent color (green-AuQD) were loaded into a hole transport layer (HTL) aiming to harvest photons in the UV region and emit visible light into the neighboring photoactive layer. Meanwhile, plasmonic grating structures, which were created on the photoactive layer surfacesviathe nanoimprinting technique, provided an enhancement effect through light scattering and GCSPR. Thus, an excellent enhancement of OSC efficiency with a significant increase in short circuit photocurrent (J(SC)) and power conversion efficiency (PCE) in comparison to that of the reference cell was achieved. The fabricated device provides a J(SC) value as high as 8.41 mA cm(-2) (a 14.11% enhancement) and a PCE value of 3.91% (a 19.57% enhancement). The systematic study clearly reveals that the remarkable enhancement of OSC efficiency is achieved by incorporating both AuQD and plasmonic grating.

DOI： 10.1039/D0NA00169D

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DOI： 10.1039/C9NR07846K

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Publishing type：Research paper (international conference proceedings)  

Asia Communications and Photonics Conference (ACP) © OSA 2019 Hybrid sensors combining a quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) were developed. The simultaneous measurement of the QCM and SPR signals allowed evaluating the swelling of polymer film and liquid properties.

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Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

DOI： 10.7567/1347-4065/ab4a94

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Other Link： http://iopscience.iop.org/article/10.7567/1347-4065/ab4a94/pdf

Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

DOI： 10.7567/1347-4065/ab48c9

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Other Link： http://iopscience.iop.org/article/10.7567/1347-4065/ab48c9/pdf

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© 2019, © 2019 Taylor & Francis Group, LLC. In this study, the effect of periodic patterned micro/nanostructures on the active layers of thin-film organic photovoltaics (OPVs) was investigated to improve the device performance. The patterned active layer structures were fabricated by a nanoimprinting technique using different templates, including compact disc recordable (CD-R), Blu-ray disc recordable (BD-R), nanowell arrays, nanodot arrays, and honeycomb structures. The OPVs consisted of Al/nanostructured P3HT:PCBM/PEDOT:PSS/ITO. Compared with a flat reference OPV, all the micro/nanostructured OPVs exhibited higher performances, originating from enhanced light absorption due to light scattering and surface plasmon excitation at the patterned Al/P3HT:PCBM interfaces.

DOI： 10.1080/15421406.2019.1651073

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.29026/oea.2019.190010

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Publishing type：Research paper (international conference proceedings)  

© 2019 FTFMD. Hybrid sensors of quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) were prepared, and the film depositions, vapor sorptions to polymer films, and liquid properties were observed. The relationship between the SPR wavelength and QCM frequency shifts depends on both the refractive index and the density of the adsorbed molecule and would give information for identification. Furthermore, the swelling of the film can be monitored using the different laws of nature in the SPR and QCM methods.

DOI： 10.23919/AM-FPD.2019.8830578

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Language：English   Publishing type：Research paper (scientific journal)  

© 2019 American Chemical Society. In this study, we demonstrate a simple and efficient method to fabricate miniature surface plasmon resonance (SPR) sensor chips by using confined sessile drop technique. A liquid optical adhesive (NOA 61) was dropped on the circular flat surface of cylindrical substrates made of poly(dimethylsiloxane) (PDMS). The formation of hemispherical optical prisms was accomplished by taking advantage of the sharp edges of cylindrical PDMS substrates that prevented the overflow of liquid NOA 61 at the edge of substrates. The size of the hemispherical optical prisms can be controlled by changing the diameter of the cylindrical PDMS substrates. After UV curing, the SPR sensor chips were obtained by the deposition of 3 nm thick chromium and 47 nm thick gold on the flat side of the prisms. The fabricated miniature SPR sensor chips were then mounted on a three-dimensional-printed flow cell to complete the microfluidic SPR sensor module. The miniature SPR sensor chips provided a comparable sensitivity to the conventional high-refractive-index glass SPR chips. To demonstrate the detection capability of nanometer-sized materials, we applied the miniature microfluidic SPR system for monitoring the deposition of layer-by-layer ultrathin films of poly(diallyldimethylammonium chloride)/poly(sodium 4-styrenesulfonate) and for detecting human immunoglobulin G.

DOI： 10.1021/acsami.9b01617

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© 2019, © 2019 Taylor & Francis Group, LLC. Silver nanoprisms (AgNPrs) have unique optical phenomena due to their localized surface plasmon resonance that results in the extinction of light from the visible to the near-infrared spectral region. In this study, we propose the colorimetric determination of silver nanoprisms in microchannels using a smartphone camera. Image acquisition was performed by capturing an image of the colloidal solution of the silver nanoprisms in the microchannel using the transmitted light. Red, green, and blue chromaticity levels were extracted from the recorded images for further quantification of the silver nanoprisms. This technique was employed for the detection and colorimetric determination of hydrogen peroxide (H2O2). Good linearity between the change in the green chromaticity level and concentration of hydrogen peroxide was observed for values from 10 to 300 μM with an R2 value of 0.9670. We anticipate that the developed methodology for the quantification of silver nanoprisms and hydrogen peroxide by monitoring the change in color in the images of transmitted light will enhance the development of simple, rapid, and reliable detection systems for quality control in the production of silver nanoprisms as well as in chemical sensor applications.

DOI： 10.1080/00032719.2019.1586913

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Language：English   Publishing type：Research paper (scientific journal)  

© 2019 The Japan Society for Analytical Chemistry. Silver nanoprisms (AgNPrs) have a unique localized surface plasmon resonance, resulting in strong absorption and scattering within the visible light region. In this work, we propose image acquisition from colloidal solutions of AgNPrs using a combination of transmitted and scattered light. The developed measurement technique could be carried out by separately recording transmitted and scattering images of the solutions, using a mobile device camera prior to a calculation of the empirical absorption value (IA). The IA value of green for AgNPrs solutions was found to be in agreement with the absorption spectra obtained using a conventional spectroscopic technique. This technique was utilized for the quantifications of hydrogen peroxide and glucose. Good linearities between ΔIA and those typical analytes were observed. The limit of detection for the typical biosensor of glucose was 19.8 μM. As such, we expect the methodology herein developed for hydrogen peroxide and glucose determinations by means of monitoring the color change of transmitted and scatting images from solutions to contribute to the development of simple, rapid, and reliable detection systems to be further applied to biochemical analysis and clinical diagnosis, as well as to household biosensor applications.

DOI： 10.2116/analsci.18P412

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Plasmonic nanostructures can be used to control the photoluminescence properties of various emitting materials. In this work, an efficient plasmon-induced energy transfer (quenching) was investigated. The luminescence intensity of gold quantum dots (AuQDs) was controlled by the localized surface plasmon resonance of silver nanoprisms (AgNPrs). The quenching was modulated by the degree of spectral overlap between the photoluminescence band of AuQDs and the dipole plasmon resonance of AgNPrs. Furthermore, an in situ controlled quenching effect of AuQDs using an oxidative etching reaction of AgNPrs by hydrogen peroxide (H2O2) was demonstrated. This technique was further developed for application as a H2O2 sensor. This system was capable of detecting 1 nM H2O2 in an aqueous solution.

DOI： 10.1007/s11468-019-01006-8

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1587/transele.2018OMP0004

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Other Link： https://dblp.uni-trier.de/db/journals/ieicet/ieicet102c.html#JuagwonLSKSOB19

Publishing type：Research paper (scientific journal)  

© 2019, © 2019 Taylor & Francis Group, LLC. Gas sensing by using the transmission surface plasmon resonance (T-SPR) technique was demonstrated. Polyacrylic acid (PAA)/5-nm-thick gold/40-nm-thick silver/polycarbonate grating substrate structure (Sensor A) responded to ammonia; however, it exhibited a strong humidity dependence. Polyvinyl alcohol (PVA)/5-nm-thick gold/40-nm-thick silver/polycarbonate grating substrate structure (Sensor B) as the sensing material was also prepared and it mainly responded to humidity. The T-SPR properties of Sensors A and B were observed simultaneously by a stacking arrangement that enabled us to obtain the responses by using a single spectrophotometer. The ammonia concentration under various humidity conditions could be accurately obtained by simultaneous measurement of Sensors A and B.

DOI： 10.1080/15421406.2019.1645466

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1166/jnn.2019.16704

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Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

DOI： 10.7567/1347-4065/ab4cfd

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Other Link： http://iopscience.iop.org/article/10.7567/1347-4065/ab4cfd/pdf

Publishing type：Research paper (scientific journal)  

© 2019 The Royal Society of Chemistry. Light management allows enhancement of light harvesting in organic solar cells (OSCs). In this paper, we describe the investigation of OSCs enhanced by the synergistic effect of gold quantum dots (AuQDs) and localized surface plasmons, obtained by blending a AuQD layer and plasmonic gold nanoparticles (AuNPs) in a hole-transport layer (HTL). Different AuQDs emitting blue, green, and red fluorescence were examined in this study. The OSCs were demonstrated to comprise an ITO-coated glass substrate/AuQDs/PEDOT:PSS:AuNPs/P3HT:PCBM/Al structure. The UV-visible spectra, current density versus voltage characteristics, impedance spectra, and incident photon-to-current efficiency of the fabricated devices were evaluated. The results showed an enhancement of photovoltaic efficiency achieved as a result of the increase in short-circuit current density (Jsc) and power conversion efficiency (PCE) in comparison with those of the reference OSCs. The best synergistic effect was found with OSCs consisting of a green-emitting AuQD layer and a HTL containing AuNPs, resulting in the highest improvement in PCE of 13.0%. This indicated that the increase in light harvesting in the developed devices was induced by extended light absorption in the UV region resulting from absorption by the AuQD layer and emission of visible fluorescence from the AuQD layer to the photoactive layers. Moreover, the localized surface plasmon effect of AuNPs, which also contributed to an increase in light trapping in the proposed OSCs, was enhanced by the effect of the AuQDs.

DOI： 10.1039/c8na00119g

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Publishing type：Research paper (international conference proceedings)  

Asia Communications and Photonics Conference (ACP) © OSA 2019 © 2019 The Author(s) Hybrid sensors combining a quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) were developed. The simultaneous measurement of the QCM and SPR signals allowed evaluating the swelling of polymer film and liquid properties. © 2019 K. Shinbo, C. Lertvachirapaiboon, Y. Ohdaira, A. Baba and K. Kato.

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s11468-018-0768-5

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Language：English   Publishing type：Research paper (scientific journal)  

Copyright © Materials Research Society 2018. A transmission surface plasmon resonance image (TSPRi) obtained with a plasmonic grating structure was investigated in combination with a smartphone camera. A substrate of a gold-coated CYTOP grating/glass slide showed the TSPR excitation wavelength of 675 nm at the incident light angle of 30°. The TSPRi acquired from a smartphone camera assembled with liquid crystal tunable filters corresponded with spectroscopic results. The sensitivity of this technique was 282/RIU. Due to changes in the sensitivity of the TSPRi intensity to the refractive index of the environment, this technique can be further developed for portable devices for sensor applications.

DOI： 10.1557/mrc.2018.141

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© 2018 The Royal Society of Chemistry. Surface plasmon resonance (SPR) originates from collective oscillation of electron density and associated electromagnetic field at a metal/dielectric interface. Reflection SPR, which includes prism-coupling and grating-coupling methods, and transmission SPR (TSPR) have been developed for use in a smartphone sensing platform. The strength of this approach relies on the SPR phenomenon: the strong electromagnetic oscillation of electrons that can occur at a metal/dielectric interface and is highly sensitive to changes in the localized dielectric on the metal surface. The observable SPR signals are strong enough to detect with a simple camera. By combining the SPR phenomenon with the high performance of a smartphone camera, smartphone-based SPR platforms have been developed for use in on-site and remote detection of biomedical and environmental samples, point-of-care devices, and practical use in household devices. This review gives an overview of smartphone-based SPR platforms in both reflection SPR and TSPR configurations, the design of the devices, and the typical setup used to acquire spectroscopic information and SPR images, as well as providing some examples of their use in the analysis of chemical and biological samples.

DOI： 10.1039/C8AY01561A

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

The application of Surface Plasmon Resonance Imaging (SPRi) for the detection of transmembrane antigen of the Rhesus (Rh) blood group system is demonstrated. Clinically significant Rh blood group system antigens, including D, C, E, c, and e, can be simultaneously identified via solid phase immobilization assay, which offers significant time savings and assay simplification. Red blood cells (RBCs) flowed through the micro-channel, where a suitable condition for Rh blood group detection was an RBC dilution of 1:10 with a stop-flow condition. Stop flow showed an improvement in specific binding compared to continuous flow. Rh antigens required a longer incubation time to react with the immobilized antibody than A and B antigens due to the difference in antigen type and their location on the RBC. The interaction between the immobilized antibodies and their specific antigenic counterpart on the RBC showed a significant difference in RBC removal behavior using shear flow, measured from the decay of the SPR signal. The strength of the interaction between the immobilized antibody and RBC antigen was determined from the minimum wall shear stress required to start the decay process in the SPR signal. For a given range of immobilized antibody surface densities, the Rh antigen possesses a stronger interaction than A, B, and AB antigens. Identification of 82 samples of ABO and Rh blood groups using SPRi showed good agreement with the standard micro-column agglutination technique. A wider coverage of antigenic recognition for RBC when using the solid phase immobilization assay was demonstrated for the RBC with the antigenic site located on the transmembrane protein of the clinically significant Rh antigen. Given the level of accuracy and precision, the technique showed potential for the detection of the Rh minor blood group system.

DOI： 10.1016/j.bios.2017.10.049

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press  

Detection of chlorpyrifos (CPF) using a surface plasmon resonance (SPR)-enhanced photoelectrochemical sensing system is demonstrated in this study. The presence of CPF was detected based on an increase in the short-circuit photocurrent when a sample is injected into the electrolyte at different concentrations. The short-circuit photocurrent signal was enhanced by both localized SPR of the gold nanoparticles and by the effects of grating-coupled propagating SPR. Using the hybrid SPR-enhancement system, CPF detection was achieved at concentrations as low as 7.5 nM. The proposed technique of leveraging a multifunctional photovoltaic effect can be used for a variety of sensing applications.

DOI： 10.1557/mrc.2017.131

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Japan Society of Applied Physics  

An electrochemically synthesized graphene oxide (GO)/poly(3,4-ethylenedioxythiophene) (PEDOT)/poly(styrene sulfonate) (PSS) thin film-based electrochemical surface plasmon resonance (EC-SPR) sensor chip was developed and employed for the detection of human immunoglobulin G (IgG). GO introduced the carboxylic group on the film surface, which also allowed electrochemical control, for the immobilization of the anti-IgG antibody via covalent bonding through amide coupling reaction. The SPR sensitivity of the detection was improved under the control by applying an electrochemical potential, by which the sensitivity was increased by the increment in applied potential. Among the open-circuit and different applied potentials in the range of -1.0 to 0.50 V, the EC-SPR immunosensor at an applied potential of 0.50 V exhibited the highest sensitivity of 6.08 × 10-3 mL μg-1 cm-2 and linearity in the human IgG concentration range of 1.0 to 10 μg mL-1 with a relatively low detection limit of 0.35 μg mL-1. The proposed sensor chip is promising for immunosensing at the physiological level.

DOI： 10.7567/JJAP.57.02CA07

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER ADVANCED TECHNOLOGY  

Transmission surface plasmon resonance (TSPR) is an unusual extraordinary optical transmission that is more transparent at certain wavelengths than expected by classical theory. The three main plasmonic structures that providing this phenomenon are nanohole arrays, diffraction gratings, and nanoslit arrays. This extraordinary optical transmission phenomenon is produced as a result of surface plasmon excitations. The shifting in TSPR responses upon changing of dielectric environment at the surface of a metallic film was observed. After TSPR was discovered from metallic nanohole arrays in 1998, the number of papers about this topic rapidly increased. In the 20 years since, TSPR has been utilized to improve the detection limits, sensitivity, selectivity, and dynamic range of biosensing devices, resulting in them having greater potential for commercialization. This review gives a broad overview of the TSPR phenomenon, the development of this technique, and the typical experimental setups used to acquire TSPR signals; it also describes how they are applied in the field of research into biosensors.

DOI： 10.1016/j.bios.2017.07.069

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© 2018 Taylor & Francis Group, LLC. Enhancement of photoisomerization of Azobenzene dye Chicago Sky Blue 6B (CSB) was attempted using long-range surface plasmon resonance (LRSPR). The CSB film was prepared on a grating substrate with metal film for LRSPR, and its transmission light property was investigated before and after white light irradiation for photoisomerization. The transmission light was markedly changed by irradiation of p-polarized white light, and the change was attributed to photoisomerization of CSB induced by LRSPR which accompanies an intense electric field. Furthermore, the effect of LRSPR was significant compared to standard SPR.

DOI： 10.1080/15421406.2018.1456146

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DOI： 10.1002/app.45641

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Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

A biosensing platform based on the covalent attachment of biomolecules on electropolymerized carboxylated conducting polymers, poly(3-aminobenzoic acid) and poly(3-pyrrole carboxylic acid), were developed for the selective simultaneous detection of two biomolecules using electrochemical-surface plasmon resonance (EC-SPR) spectroscopy. The surface morphology of the developed biosensors was studied by scanning electron microscopy and atomic force microscopy. The EC-SPR dual biosensor was developed for the label-free, simultaneous, and selective detection of glucose and human immunoglobulin G (IgG). A change in current density was clearly observed after the injection of glucose, whereas a change in SPR reflectivity was clearly observed after the injection of human IgG. The present work demonstrates the potential of this biosensing platform for real sample analysis in the future. (C) 2017 Wiley Periodicals, Inc.

DOI： 10.1002/app.45641

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical Engineers of Japan  

In diagnostics analysis, creatinine is a biomarker for the evaluation of renal and muscular dystrophy in various biology and closely related to the life activities of the organism. In this research, we investigated the transmission surface plasmon resonance-imaging (TSPR-i) with a 3-channel microfluidic cell. TSPR-i based on the exploitation of propagating SPR is the technique for monitoring the changes in surface plasmon resonance of gold film on both glass slide substrates and diffraction gold grating substrates to their surrounding environments in transmission configuration. The silver nanoparticles (AgNPs) were deposited with poly (diallydimethylammonium chloride) (PDADMAC) and poly (sodium 4-styrenesulfonate) (PSS) using layer-by-layer (LbL) technique on gold thin film grating/substrate surfaces for the detection of creatinine. In this experiment, the TSPR-i signal was detected by a camera coupled with liquid crystal tunable filters (LCTF). The TSPR-i signal of Au grating dominated at the incident angle of ∼35 degree and a strong excitation wavelength was observed at ∼720 nm. After the deposition of AgNPs on the gold grating substrate, the TSPR-i intensity decreased and then increased again when incubated with creatinine for 1 h. In addition, TSPR-i technique was used to study the effect of localized surface plasmon resonance (LSPR) from plasmonic AgNPs on the gold-grating/dielectric interface for the signal enhancement of creatinine. The 5-bilayer of AgNPs/PDADMAC film onto 10 bi-layer of PDADMAC/PSS intermediate layers on BK7 glass slides before and after injection of creatinine was studied by UV-vis absorption spectroscopy. The creatinine sensor exhibited good sensitivity toward the determination of creatinine and showed a linear calibration range from 0.1 to 20 mM. A simple, and costeffective method has been demonstrated on the TSPR imaging system for real-time, label-free, good sensitive which will be potentially useful for clinical applications.

DOI： 10.23919/ISEIM.2017.8166530

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Gold quantum dots (AuQDs) are employed as photosensitizers in organic thin-film solar cells (OSCs) to improve their photoelectric conversion properties. Three types of AuQDs with different fluorescence emission wavelengths are used: blue (B-AuQDs), green (G-AuQDs), and red (R-AuQDs). AuQDs are loaded into the poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) thin-film layer of OSCs. UV-vis spectra, atomic force microscope images, current density-voltage characteristics, and impedance spectra of the fabricated devices are measured for the three aforementioned types of AuQDs. All types of AuQDs improve the photoelectric conversion properties, and the G-AuQD-loaded OSCs exhibit the best improvement, exhibiting an efficiency increase of 10% compared with OSCs without the AuQDs. The fluorescence/photo-sensitization of the AuQDs plays an important role in the enhancement of the OSCs. Finite-difference time-domain simulations indicate increased electric field intensity due to a small degree of AuQDs aggregation.

DOI： 10.1002/ppsc.201700133

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

The localized surface plasmon resonance of in-plane dipole plasmon resonance of silver nanoprisms was used to facilitate transmission surface plasmon resonance (TSPR). The TSPR signal was detected by a camera coupled with liquid crystal tunable filters. This technique was further utilized for the multiple detection of hydrogen peroxide. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2017.04.037

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

Analysis of NH3 gas under various humidity conditions was conducted using a waveguide surface plasmon resonance (SPR) sensor with dual sensing parts. Two pairs of Ag films/sensing polymer films were prepared separately on a waveguide core of BK-7 slide glass. Poly(acrylic acid) (PAA) and poly(vinyl alcohol) (PVA) were used as sensing materials. A white light was guided through the core by illuminating the substrate edge, and the SPR property was investigated by observing the output light spectrum. The thicknesses of PAA and PVA films were adjusted to induce SPR at different wavelengths. PAA exhibited remarkable response against NH3 gas, but it also exhibited a strong dependence on humidity. In contrast, PVA responded to humidity but hardly responded to NH3 gas below 20 ppm. The dual sensing would allow us to conduct precise NH3 measurements under various humidity conditions.

DOI： 10.2116/analsci.33.443

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

A novel method was proposed to judge degradation/health of lithium-ion batteries (LIBs) using the capacitance that was estimated from the real-time voltage and current characteristics of the batteries. It is thought that the capacitance of LIBs decreases with degradation because of undesirable components formed on the electrodes that are the main cause of the degradation. As the LIBs are active, the capacitance was evaluated from the differential equation, Q/v = I/(v/t) = i/(dv/dt), using the voltage and current characteristics during the charging or discharging. The capacitances of the commercial LIBs with different SOHs; 100%, 92%, and 88% were estimated during the charging and discharging using the equation. The average capacitance in the specific voltage region of the batteries was directly proportional to the state of health. Therefore, the proposed measurement is thought to be a useful method for judging degradation of LIBs. (C) 2017 Wiley Periodicals, Inc.

DOI： 10.1002/eej.22962

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

In this work, we studied the performance enhancement of organic thin-film solar cells (OSCs) originating from the presence of diffraction gratings on the surface of the active layer. Two types of diffraction gratings, periodic gratings (Blu-ray disc recordable: BD-R) and quasi-random gratings (Blu-ray disc: BD), were employed as master templates for grating structures. The grating structures were introduced to the surfaces of poly(3-hexylthiophene) (P3HT):phenyl-C-61-butyric acid methyl ester (PCBM) films, which were the active layers of the solar cells. The addition of the grating structures led to an increase of light absorption in the absorption region of P3HT:PCBM induced by light scattering. Furthermore, the grating-coupled surface plasmon resonance generated additional light absorption peaks. With illumination of non-polarized light at a normal incident angle, the short-circuit current densities of the BD-R and BD solar cells improved by 11.05% and 10.6%, respectively. Efficiency improvements of 19.28% and 3.21% were also observed for the BD-R and BD devices, respectively. Finally, the finite-difference time-domain simulation results revealed an enhanced electric field in the P3HT: PCBM layer, especially in the BD-R OSC devices.

DOI： 10.1039/c6nr09951c

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The microfluidic transmission surface plasmon resonance (MTSPR) constructed by assembling a gold-coated grating substrate with a microchannel was employed for biosensor application. The transmission surface plasmon resonance spectrum obtained from the MTSPR sensor chip showed a strong and narrow surface plasmon resonance (SPR) peak located between 650 and 800 nm. The maximum SPR excitation was observed at an incident angle of 35 degrees. The MTSPR sensor chip was employed for glucose sensor application. Gold-coated grating substrates were functionalized using 3-mercapto-1-propanesulfonic acid sodium salt and subsequently functionalized using a five-bilayer poly(allylamine hydrochloride)/ poly(sodium 4-styrenesulfonate) to facilitate the coupling/ decoupling of the surface plasmon and to prepare a uniform surface for sensing. The detection limit of our developed system for glucose was 2.31 mM. This practical platform represents a high possibility of further developing several biomolecules, multiplex systems, and a point-of-care assay for practical biosensor applications. (C) 2017 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.56.017002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

In this study, we demonstrate improved photovoltaic properties in inverted organic thin-film solar cells by simultaneous excitation of grating-coupled surface plasmons and grating-coupled waveguide modes on gold grating surfaces. The cell consists of a glass-ITO substrate/titanium dioxide/poly(3-hexylthiophene-2,5-diyl): phenyl-C61-butyric acid methyl ester/poly(3,4-ethylenedioxythiophene): poly( styrene sulfonate)/gold structure. The grating structures were fabricated on P3HT: PCBM layers using a nanoimprinting technique with a PDMS stamp. The grating-structured PDMS stamps were fabricated using a DVD-R grating template with a grating pitch, Lambda, of 740 nm. Reflectivity measurements made using p-polarized light clearly indicate 2 types of excitation modes, i.e., surface plasmons and waveguide modes, while s-polarized light produces only waveguide modes. Incident photon-to-current efficiency measurements exhibited increased photocurrent wavelengths corresponding to the wavelengths of surface plasmon excitations and waveguide mode excitations. Through the simultaneous excitation of surface plasmons and waveguide modes, short-circuit photocurrents in the grating-structured cells exhibited an improvement of up to 11% in the solar cells, leading to an efficiency increase of 16%.

DOI： 10.1039/c6cp06931b

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1541/ieejfms.136.690

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Transmission light property due to surface plasmon resonance (SPR) was investigated for glass substrate/500-nm-thick fluoropolymer (CYTOP) with a grating structure/thin metal film/mixed solution of water and glycerol system. Transmission light peaks were observed due to grating-coupled SPR, with a remarkable peak intensity when pure water exists as an ambient dielectric. CYTOP exhibits a refractive index close to that of water, and the remarkable peak intensity was attributed to long-range SPR. The monitoring of polyelectrolyte layer-by-layer film deposition using transmission light was also investigated.

DOI： 10.1007/s00289-016-1683-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

In this study, urchin-like gold nanoparticles (UL-AuNPs) are used in the fabrication of organic thin-film solar cells (OSCs). UL-AuNPs, which have gold nanothorns on their surface, enhance light accumulation by acting as light-trapping materials. This is due to the enhanced electric field and light scattering attributed to the nanothorns on the surface of the nanoparticles. UL-AuNPs were incorporated into a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) thin-film layer of organic thin-film solar cells (OSCs). UV-vis spectra, atomic force microscopy (AFM) images, current density versus voltage properties, and the impedance spectra of the fabricated devices were recorded at various concentrations of UL-AuNPs. We found that the efficiency of the OSCs with UL-AuNPs was not only higher than that of a reference cell without nanoparticles but also higher than that of OSCs with spherical AuNPs. Finite-difference time-domain (FDTD) simulation indicated that the electric field around the UL-AuNPs increased due to the presence of nanothorns.

DOI： 10.1039/c6cp02373h

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Applied Physics  

Fluorescent nanodroplets of liquid crystal (LC) were generated by the electrospray deposition of LC solvent containing rhodamine 6G (Rh6G) dye molecules. The shape and density of the nanodroplets strongly depended on the concentration of LC diluted with ethanol solution. The fluorescent spectra from the Rh6G molecules in LC nanodroplets were obviously blue-shifted compared with the LC films of the bulk state. Furthermore, the LC nanodroplets were dispersed on a metallic nanograting formed by optically modifying an azobenzene thin-film layer under the metallic film. The nanodroplets were size-selectively aligned on the metallic nanograting.

DOI： 10.7567/JJAP.55.02BB09

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Improvement of the on/off ratio in carrier-generation type organic field-effect transistors with pentacene and MoO3 layers was attempted using oblique deposition. A MoO3 layer was formed only between the gold (Au) source and the drain electrodes, and devices with a MoO3 layer evaporated under various deposition angles were fabricated. A formation of a MoO3-free area is expected adjacent to the source or drain electrode by the oblique deposition. The off-current in the device decreased and the on/off ratio was increased with increasing deposition angle, and we achieved a fabricating device with a MoO3 layer having high on/off ratio, almost the same as that of the device without the MoO3 layer. From those results, we deduced that charge-transfer (CT) complexes at the pentacene/MoO3 interface formed a high-conductive path for the off-current, and the off-current was reduced by the formation of a highly-resistive MoO3-free area between electrodes. Therefore, controlling the CT complex layer formation by patterning the MoO3 layer can reduce the amount of off-current and improve the on/off ratio. (C) 2016 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.55.02BB06

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Fluorescent nanodroplets of liquid crystal (LC) were generated by the electrospray deposition of LC solvent containing rhodamine 6G (Rh6G) dye molecules. The shape and density of the nanodroplets strongly depended on the concentration of LC diluted with ethanol solution. The fluorescent spectra from the Rh6G molecules in LC nanodroplets were obviously blue-shifted compared with the LC films of the bulk state. Furthermore, the LC nanodroplets were dispersed on a metallic nanograting formed by optically modifying an azobenzene thin-film layer under the metallic film. The nanodroplets were size-selectively aligned on the metallic nanograting. (C) 2016 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.55.02BB09

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：HINDAWI PUBLISHING CORP  

In this study, we demonstrate a long-range surface plasmon resonance (LR-SPR) biosensor for the detection of whole cell by captured antigens A and B on the surface of red blood cells (RBCs) as a model. The LR-SPR sensor chip consists of high-refractive index glass, a Cytop film layer, and a thin gold (Au) film, which makes the evanescent field intensity and the penetration depth longer than conventional SPR. Therefore, the LR-SPR biosensor has improved capability for detecting large analytes, such as RBCs. The antibodies specific to blood group A and group B (Anti-A and Anti-B) are covalently immobilized on a grafting self-assembled monolayer (SAM)/Au surface on the biosensor. For blood typing, RBC samples can be detected by the LR-SPR biosensor through a change in the refractive index. We determined that the results of blood typing using the LR-SPR biosensor are consistent with the results obtained fromthe agglutination test. We obtained the lowest detection limits of 1.58 x 10(5) cells/ml for RBC-A and 3.83 x 10(5) cells/ml for RBC-B, indicating that the LR-SPR chip has a higher sensitivity than conventional SPR biosensors (3.3 x 10(8) cells/ml). The surface of the biosensor can be efficiently regenerated using 20mM NaOH. In summary, as the LR-SPR technique is sensitive and has a simple experimental setup, it can easily be applied for ABO blood group typing.

DOI： 10.1155/2016/1432781

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Taylor and Francis Inc.  

A quartz-crystal-microbalance (QCM) and surface-plasmon-resonance (SPR) hybrid sensor was prepared, and the sorptions of water and ethanol vapors to polyvinyl alcohol (PVA) films were observed in situ. The shift of the SPR wavelength depended on the PVA film thickness as well as the sorbed vapor. It was estimated to be due to the film swelling induced by the vapor sorption and the relationship between the film thickness and the penetration depth of evanescent wave.

DOI： 10.1080/15421406.2015.1097002

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical Engineers of Japan  

A novel method was proposed to judge degradation/health of lithium-ion batteries using the capacitance that was estimated from the real-time voltage and current characteristics of the batteries. It is thought that the capacitance of lithium ion batteries decreases with degradation because of undesirable components formed on the electrodes that are the main cause of the degradation. As the lithium ion batteries are active, the capacitance was evaluated from the differential equation, ΔQ/Δv = I/(Δv/Δt) = i/(dv/dt), using the voltage and the current characteristics during the charging or the discharging. The capacitances of the commercial LIBs with different SOHs
100, 92 and 88% were estimated during the charging and the discharging using the equation. The average capacitance in the specific voltage region of the batteries was directly proportional to the state of health. Therefore, the proposed measurement is thought to be a useful method for judging degradation of lithium-ion batteries.

DOI： 10.1541/ieejfms.135.624

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

We fabricated organic field-effect transistors (OFETs) having a thin layer of molybdenum trioxide (MoO3), a Lewis acid, and evaluated their electrical characteristics. The insertion of a thin MoO3 layer reduces the on/off ratio but improves the apparent mobility of the charge carriers. To identify the dominant mechanism responsible for this effect, we characterized devices having a 69-nm-thick pentacene layer with a 1-nm-thick MoO3 layer either between the gold source and the drain electrodes or only directly under these electrodes. The former device exhibited a low on/off ratio, whereas the latter device exhibited an on/off ratio comparable to those of conventional pentacene OFETs without a thin MoO3 layer, suggesting that the formation of charge-transfer (CT) complexes immediately above the conduction channel is the critical mechanism. CT complexes at the pentacene/MoO3 interface immediately above the conduction channel contribute to the formation of an effective channel for off-currents as well as drain currents. Moreover, we also attempted to improve the on/off ratio by using a cloth to rub the surface of a thin MoO3 layer immediately above the conduction channel to create what we believe to be a profile with abrupt changes in height in the direction of the drain current conduction in OFETs. Consequently, it was found that such a rubbed MoO3 layer had a surface with a scratched pattern, and the on/off ratio of the OFET was improved, indicating that controlling the CT complex formation by patterning a MoO3 layer can reduce the off-current in OFETs having a pentacene/MoO3 active layer.

DOI： 10.1587/transele.E98.C.98

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

A quartz-crystal-microbalance (QCM) and surface-plasmon-resonance (SPR) hybrid sensor was prepared, and the depositions of polymer electrolytes layer-by-layer (LbL) films were observed in situ. The estimated thicknesses obtained from the QCM method were different from those obtained from the SPR method. This was estimated to be caused by film swelling and water contained in the film.

DOI： 10.1587/transele.E98.C.136

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

The fabrication of a grating structure formed by a solid-state electrolyte layer on a dye-TiO2 film by the nanoimprinting technique using a polydimethylsiloxane (PDMS) stamp and its application in photoelectric conversion devices are described. The PDMS grating pattern is imprinted from blu-ray disc recordable. A silver electrode was deposited on the patterned solid-state electrolyte layers. Surface plasmon resonance (SPR) excitation was observed in the fabricated solar cells by irradiation with white light. The photoelectric conversion properties were measured to study the effect of the two types of SPR excitations, i.e., the propagating surface plasmon on the Ag grating surface and the localized surface plasmon from the Au nanoparticles on TiO2.

DOI： 10.1587/transele.E98.C.104

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：HINDAWI PUBLISHING CORPORATION  

The electropolymerization process and doping/dedoping properties of poly(3-aminobenzoic acid) (PABA) thin films on gold-coated commercial BD-R and DVD-R grating substrates were simultaneously studied by the combination of electrochemical technique and transmission surface plasmon resonance (TSPR) spectroscopy. The optical property as a function of the applied potentials and time dependence during electropolymerization were studied. The obtained TSPR wavelength scan spectra after electropolymerization showed that the maximum wavelength slightly shifted to longer wavelength indicating the increase of film thickness. In addition, the change during construction of PABA-based immunosensor for label-free detection of human immunoglobulin G can be observed.

DOI： 10.1155/2015/650516

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Water-stable poly(acrylic acid) (PAA) fibers were fabricated on flat gold thin films via an electrospinning technique. The obtained fibers were then used to construct long-range surface plasmon resonance (LR-SPR) biosensors. Because LR-SPR spectroscopy has a greater evanescent field intensity and penetration depth than conventional surface plasmon resonance (SPR) spectroscopy, the increased surface area of the PAA fibers within the surface plasmon evanescent field was efficiently utilized for biosensor applications. The water-stable electrospun PAA fibers were obtained by adding beta-cyclodextrin as a crosslinker, followed by thermal treatment at 150 degrees C for 40 min. In addition, the layer-by-layer deposition of poly(diallyldimethylammonium chloride) and PAA ultrathin films on the electrospun PAA fibers functionalized their surfaces and further increased their water-stability by increasing the number of active carboxylic acid groups. Fiber surfaces were then successfully activated for the construction of immunosensors for the detection of human immunoglobulin G. Therefore, the present study demonstrates the potential of electrospun fibers for LR-SPR biosensor applications. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2014.07.121

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

We demonstrate the multiple plasmonic effect on the photocurrent properties of photoanodes containing Ag or Au nanoparticles (NPs) loaded onto titanium dioxide film (Ag-TiO2 or Au-TiO2) on Au grating surfaces. Ag-TiO2 or Au-TiO2 nanocomposite particles are prepared by a flame spray pyrolysis route. The structures and morphologies of the prepared products are characterized by high-resolution transmission electron microscopy. The Ag-TiO2 or Au-TiO2 composite NPs are deposited by spin coating onto the Au grating surfaces. The photoanode electrode is a layered structure of blu-ray disc-recordable grating substrate/Au/Ag (or Au)-TiO2/dye/electrolyte/indium-tin oxide. The plasmonic effect is induced when Ag or Au NPs are located within the propagating surface plasmon (SP) field on the Au grating surface. The short-circuit photocurrent is increased by exciting the grating-coupled propagating SP on the Au gratings and is further enhanced by positioning the Ag or Au NPs within the grating-coupled SP field. Copyright (C) 2014 John Wiley & Sons, Ltd.

DOI： 10.1002/sia.5577

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

In this study, we achieved an enhancement of the transmission surface plasmon resonance (T-SPR) intensity by depositing silver nanoparticles (AgNPs) onto a gold grating substrate. The T-SPR spectrum of the gold grating substrate with AgNPs showed a strong and narrow SPR peak located between 650 and 800 nm; the maximum SPR excitation was observed at a 35A degrees angle of incidence. We controlled the distance between the gold grating surface and the AgNPs by using layer-by-layer (LbL) ultrathin films of poly(diallydimethylammonium chloride) (PDADMAC) and poly(sodium 4-styrenesulfonate) (PSS) to study the distance dependence of the coupling effect between the AgNPs and the gold grating substrate. The distance-dependent T-SPR response of peak position and intensity showed distinctive changes when the intermediate layer was 10 bilayers (similar to 17 nm) thick. The strongest coupling surface plasmon excitation between the AgNPs and the gold grating substrate was obtained at this layer spacing. Furthermore, we explored the potential of the developed system as a switchable pH sensor. The T-SPR spectrum sensitively changed as the pH switched from acidic (pH 2) to alkaline (pH 12) conditions by the swelling/shrinking of the poly(allylamine hydrochloride) (PAH)/PSS LbL film, respectively, which was deposited between the AgNPs and the gold grating.

DOI： 10.1007/s11468-014-9695-2

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Language：English   Publishing type：Part of collection (book)   Publisher：Wiley Blackwell  

This chapter contains sections titled: Introduction Combined Surface Plasmon Resonance Methods and Electrochemical Measurements Investigation of Electropolymerization Process of Conducting Polymer Thin Films by EC-SPR Electrochemical SPR-surface plasmon light scattering (SPLS) Electrochemical SPR-SPPL Applications to Biosensors Conclusions References

DOI： 10.1002/9783527654703.ch30

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER INTERNATIONAL PUBLISHING AG  

Grating-coupled propagating surface plasmons associated with silver-nanoparticle 2D crystalline sheets exhibit sensitive plasmonic resonance tuning. Multilayered silver-nanoparticle 2D crystalline sheets are fabricated on gold or silver grating surfaces by the Langmuir-Blodgett method. We show that the deposition of Ag crystalline nanosheets on Au or Ag grating surfaces causes a drastic change in propagating surface plasmon resonance (SPR) both in angle measurements at fixed wavelengths and in fixed incident-angle mode by irradiation of white light. The dielectric constant of the multilayered silver nanosheet is estimated by a rigorous coupled-wave analysis. We find that the dielectric constant drastically increases as the number of silver-nanosheet layers increases. The experimentally obtained SP dispersions of Ag crystalline nanosheets on Au and Ag gratings are compared with the calculated SP dispersion curves. The drastic change in the surface plasmon resonance caused by the deposition of Ag-nanoparticle 2D crystalline sheets on metal grating surfaces suggests the potential for applications in highly sensitive sensors or for plasmonic devices requiring greatly enhanced electric fields.

DOI： 10.1186/2193-1801-3-284

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Materials Research Society  

A novel and fundamental method was reported to judge states of lithium ion batteries (LIBs) using the capacitance and the voltage of the cells that were estimated from the real-time currents and voltage characteristics of the cells. We measured the differential capacitance, that is, dQ/dV or delta Q/ delta V that is equal to the currents (I) divided by differential voltages (dV/dt) calculated from the current and the voltage characteristics of the cell during the charging/ discharging, where Q is the charge that flows through the cell, V is the voltage of the cell and t is time. It is thought that the capacitance decrease with the degradation of the cell because the effective area of the electrodes is decreasing due to formation of undesirable compounds. The differential capacitance in some specific voltage range for the LIBs was approximately directly proportional to the state of the degradation of the cell. Therefore, it is concluded that the novel method is very useful to judge the state of the LIBs.

DOI： 10.1557/opl.2014.671

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this work, we report the fabrication of grating structure of solid-state electrolyte layers on dye-TiO2 film by nanoimprint technique using PDMS stamp, and their application to photo-electric conversion devices. PDMS grating pattern is imprinted from BD-R or nickel templates. Silver electrode was deposited on the patterned solid-state electrolyte layers. Surface plasmon resonance excitation is observed on the fabricated solar cells by an irradiation of white light. The photo-electric conversion properties are measured to study the effect of two types of surface plasmon resonance excitations, i.e. propagating surface plasmon on Ag grating surface and localized surface plasmon from the Au nanoparticles on TiO2.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A waveguide-based SPR sensor for double analyte detections was prepared with a single waveguide, and sensing for ammonia and water vapors were carried out. A BK-7 slide glass was used as a waveguide core, and two pairs of Ag films (50 nm) / sensing polymer films with different thicknesses were prepared separately on the waveguide. White light was input from the substrate edge, and the output light spectrum was observed. SPR dips can be separately observed in the output light spectra by selecting the thickness of the polymer film, which govern the SPR condition. Poly(acrylic acid) (PAA) and poly(vinyl alcohol) (PVA) were used as sensing material. PAA responded to both of water and ammonia vapors, and PVA mainly responded to water vapor. Simultaneous measurement would enable precise ammonia measurement under various humidities.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：HINDAWI PUBLISHING CORPORATION  

Au-loaded TiO2 nanoparticles were synthesized by the modified sol-gel method together with the impregnation method. Anatase phase of TiO2 was obtained in all samples with an average particle size of 20 nm. For the enhancement of DSSCs, the dye-sensitized solar cells composed of the ITO/Au-loaded TiO2/N-719/electrolyte/Pt were fabricated. Au-loaded TiO2 films were deposited by using squeegee method. Finally, the fabricated cells were studied upon an irradiation of solar light to study the performance. The fabricated cell with up to 1.0 mol% Au-loaded TiO2 could enhance the performance by localized surface plasmon effect and scattering property.

DOI： 10.1155/2014/865423

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We fabricated plasmonic gold nanoparticle (AuNP)-TiO2 nanocomposite films and measured the photocurrent that originates from the water-splitting reaction catalyzed by the AuNP-TiO2 nanocomposite photo-electrocatalytic (PEC) electrode. The localized surface plasmon resonance (LSPR) of the gold nanoparticles affected the generation of photocurrent by TiO2 upon illumination with visible light. Electrochemical impedance spectroscopy (EIS) revealed that the improvement in the photocurrent generation originates from an enhancement in electron-hole pair generation induced by the SPR of the plasmonic gold nanoparticles rather than the extension of the electron lifetime. Moreover, we introduced a novel method to enhance the photocurrent of TiO2 by a multiple plasmonic effect, i.e., LSPR of plasmonic gold nanoparticles and the grating-coupled propagating SP on a gold grating. We fabricated the AuNP-TiO2 nanocomposites on a gold-coated Blu-ray disc recordable (BD-R). The enhancement of the photocurrent due to the combination of LSPR and the grating-coupled SP was investigated.

DOI： 10.1039/c4cp03885a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

In this study, we present an electrochemically controlled surface plasmon resonance (EC-SPR) biosensor to detect adrenaline on poly(2-aminobenzylamine) (P2ABA) thin films. The P2ABA thin films are stable and display electroactivity in a neutral PBS solution. Specific detection of adrenaline was performed on P2ABA thin films because the benzylamine groups in the P2ABA structure could specifically react with adrenalines. Adrenaline was detected in real time by EC-SPR spectroscopy, which provides an EC-SPR reflectivity change on the P2ABA thin film upon adrenaline injection. The measured responses were quite different from those for uric acid and ascorbic acid, which are major interferences in adrenaline detection. The electrochemically applied potential facilitates the specific detection of adrenaline. In addition, the detection of adrenaline on the P2ABA thin films was investigated by a quartz crystal microbalance technique. The detection limit for adrenaline at open circuit potential was 10 pM. The present study provides a useful information on the detection of adrenaline on the P2ABA thin films. Copyright (c) 2013 John Wiley & Sons, Ltd.

DOI： 10.1002/sia.5301

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Language：English   Publishing type：Research paper (scientific journal)  

Poly(2-aminobenzylamine)/single wall carbon nanotube (P2ABA/SWNTS) thin films were fabricated for the detection of UA by using electrochemical surface plasmon resonance spectroscopy (EC-SPR) technique. The suspension of 0.01% wt of carboxylated SWNTSs was assembled on the polymer film because of the electrostatic and van der Waals interactions between the COOH and NH 2. The P2ABA/SWNTS thin film formation on gold electrode was studied by EC-SPR technique. In this work, uric acid was detected by EC-SPR in PBS buffer comparing with the interference response with ascorbic acid. EC-SPR uric acid sensor using P2ABA/SWNTS thin film can be applied for the detection of uric acid in urine. © 2013 Taylor and Francis, LLC.

DOI： 10.1080/15421406.2013.803887

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

The functionalized pyrrole copolymers were fabricated by electropolymerization of pyrrole (Py) and functionalized pyrrole monomers, pyrrole-3-carboxylic acid (P3C) and 4-(3-pyrrole) butyric acid (PBA). The electrochemical behavior and doping/dedoping properties of the obtained copolymer thin films were investigated by cyclic voltammetry (CV) in neutral phosphate-buffered saline (PBS) solution. Moreover, the functionalized pyrrole copolymer films were characterized by UV-vis absorption spectroscopy and atomic force microscopy (AFM). The obtained copolymer thin films showed good stability and electroactivity in neutral PBS solution. The presented functionalized pyrrole copolymer thin films may possess potential applications to study in various systems of the biosensors.

DOI： 10.1080/15421406.2013.804775

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Electropolymerization of carboxylated conducting polymer/carbon nanotubes (CNTs) composites thin films has been studied by in situ electrochemical-surface plasmon resonance (EC-SPR) spectroscopy. Two derivatives of benzothiophene, thianaphthene-2-carboxylic acid and benzothiophene-2-propionic acid, composited with CNTs were electropolymerized in an acetonitrile with the potential range between 0 and 1.2V at scan rate of 20mV/s. The obtained films were characterized by in situ EC-SPR spectroscopy, UV-vis absorption spectroscopy, and atomic force microscopy. It was found that CNTs can improve properties of polymer/CNT composites films. Moreover, the obtained thianaphthene-2-carboxylic acid film can be further used for construction of immunosensor for detection of human IgG.

DOI： 10.1080/15421406.2013.803890

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

We developed a novel technique for increasing the sensitivity of transmission surface plasmon resonance (T-SPR) signals. T-SPR spectroscopy was performed by irradiating, with white light, a gold grating substrate whose surface was nanostructured by growing gold nanoparticles (AuNPs). AuNPs were grown directly on the substrate surface by alcohol reduction and their growth was observed at various stages by UV-visible spectroscopy and standard Kretschmann-type SPR spectroscopy. For comparison, normal gold film with smooth surface was examined under similar condition. The T-SPR results show a possibility of hybrid excitation of both localized and propagating surface plasmon. Significantly, T-SPR spectra of the gold grating substrate obtained during AuNP growth show stronger and narrower peaks in the range 650-800 nm. The maximum T-SPR excitation was at an incident angle of 35 degrees. A layer-by-layer system of 5,10,15,20-tetrakis (1-methyl-4-pyridinio) porphyrin tetra(p-toluenesulfonate) molecules and sodium copper chlorophyllin molecules was used to verify the enhancement of the developed system. We believe that the AuNPs/Au grating for T-SPR devices will provide enhanced signals for detecting nanometer order materials and for high-sensitive sensor applications.

DOI： 10.1007/s11468-012-9400-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

We developed a novel technique for increasing the sensitivity of transmission surface plasmon resonance (T-SPR) signals. T-SPR spectroscopy was performed by irradiating, with white light, a gold grating substrate whose surface was nanostructured by growing gold nanoparticles (AuNPs). AuNPs were grown directly on the substrate surface by alcohol reduction and their growth was observed at various stages by UV-visible spectroscopy and standard Kretschmann-type SPR spectroscopy. For comparison, normal gold film with smooth surface was examined under similar condition. The T-SPR results show a possibility of hybrid excitation of both localized and propagating surface plasmon. Significantly, T-SPR spectra of the gold grating substrate obtained during AuNP growth show stronger and narrower peaks in the range 650-800 nm. The maximum T-SPR excitation was at an incident angle of 35 degrees. A layer-by-layer system of 5,10,15,20-tetrakis (1-methyl-4-pyridinio) porphyrin tetra(p-toluenesulfonate) molecules and sodium copper chlorophyllin molecules was used to verify the enhancement of the developed system. We believe that the AuNPs/Au grating for T-SPR devices will provide enhanced signals for detecting nanometer order materials and for high-sensitive sensor applications.

DOI： 10.1007/s11468-012-9400-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

In this study, we fabricated a novel quartz-crystal-microbalance (QCM)/optical-waveguide hybrid sensor. An in situ observation of a lead phthalocyanine (PbPc) thin-film deposition was conducted during vacuum evaporation, and the effectiveness of the sensor was demonstrated. The film thickness was obtained from the QCM frequency, and the optical absorption of the film was observed by optical waveguide spectroscopy using part of the QCM substrate without the electrode. The film absorption depends on the polarization direction, substrate temperature and deposition rate, owing to aggregate formation. The thickness dependence of the absorption property was also investigated. (C) 2013 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.52.05DC20

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

We report enhanced photocurrent properties of dye/Au-loaded titanium dioxide (TiO2) films on Au gratings. Au-loaded TiO2 nanopowders were first synthesized by a modified sol-gel method and then prepared by the impregnation method. We also fabricated dye-sensitized solar cells, which were composed of Au grating/Au-TiO2/TMPyP-SCC LbL (20 bilayers)/electrolyte/ITO substrates. Short-circuit photo-current measurements showed that Au-loaded TiO2 with grating-coupled surface plasmon excitation can enhance the short-circuit photocurrentof the fabricated cells.

DOI： 10.1587/transele.E96.0.385

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

Insertion of a thin layer of the Lewis acid molybdenum trioxide (MoO3) improves the apparent mobility of charge carriers in organic field-effect transistors (OFETs). In order to identify the dominant mechanism responsible for this, we characterized devices having a bottom pentacene (70 - z nm)/MoO3 (1 nm)/top pentacene (z nm) structure and those having pentacene (69 nm)/MoO3 (1 nm) only under the gold source and drain electrodes. The former devices exhibited large drain currents (I-DS)and mobilities, regardless of the z value. Moreover, the latter devices exhibited comparable I-DS and mobilities to those of conventional pentacene OFETs, suggesting that the formation of CT complexes just above the conduction channel is the critical mechanism. Carriers generated by dissociation of CT complexes at the pentacene/MoO3 interface contribute to the formation of an effective channel and the apparent mobility. (C) 2012 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.51.101601

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Surface plasmon resonance (SPR)-enhanced optical transmission is actively controlled by an electrochromism of conducting polymer thin films. Polyaniline and poly(3,4-ethylenedioxythiophene) thin films are deposited on a thin gold grating surface. SPR-enhanced optical transmission is demonstrated by irradiating white light on the conducting polymer thin filmgold grating surface and detecting the transmitted light from the back side. The transmission SPR system is combined with an electrochemical setup to manipulate the resonance. The wavelength of the sharp peak in the transmission light spectra is tuned by electrochemical doping/dedoping of the conducting polymer thin films. The present study of controllable SPR-enhanced optical transmission should provide novel active plasmonic devices such as active bandpass filters or biosensors.

DOI： 10.1002/adfm.201200373

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Imprinted solution-processible gold nanoparticle (AuNP) grating films were fabricated for use as a grating-coupled surface plasmon resonance (SPR) excitation substrate. The imprinted AuNP grating pattern, which consists of a 1.72 mu m grating pitch, was fabricated on flat glass substrates by imprinting AuNP on silicon grating templates. In this study, the SPR measurements were carried out on an SPR device in the grating-coupling configuration with a He-Ne laser (lambda = 632.8 nm) as the excitation source, and multimode surface plasmon excitations were observed upon irradiation with white light. SPR excitation of our substrate was observed at the incident angle of 47.1 degrees. For SPR measurements using white light irradiation, multimode surface plasmon excitation resulting from several diffraction orders was observed in the wavelength region of 500-850 nm. The surface plasmon dispersion branches were calculated to obtain the diffraction order in this region. SPR excitation of the imprinted AuNP grating substrate was further studied by fabrication of a layer-by-layer ultrathin film of iron containing bis(terpyridine) polymer (Fe(II)-BTP) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). A shift of the SPR excitation spectrum was observed when the ultrathin film was deposited on the imprinted AuNP grating surface. Thus, this substrate should be a useful SPR substrate in a variety of applications such as photoelectric conversions and sensors. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2012.07.003

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCIENCE PRESS  

Optical near-field excitations were investigated on the basis of molecular alignment control of liquid crystals (LCs) on an optically rewritable nanostructure of photoreactive molecular thin films. Twisted nematic (TN) cells of LC molecules were constructed utilizing ITO substrates with 260 nm gratings of an azobenzene molecular thin film, fabricated using standing evanescent waves. The polarization changes of light transmitted through the TN cells, which were due to the alignment changes of LC molecules locally rubbed by the azobenzene nanogratings, were observed. Furthermore, we demonstrated local plasmon excitation of Au nanowires deposited on the azobenzene nanogratings using oblique vacuum evaporation, a phenomenon that produced strong anti-optical absorption spectra. The modulation of the local plasmon resonance in metallic nanowires decorated with LC molecules was confirmed.

DOI： 10.1007/s11433-012-4754-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

In this study, we describe the combination of transmission surface plasmon resonance (TSPR) an electrochemical techniques for the application to biosensors with conducting polymers. Electropolymerization was employed to construct poly(pyrrole-3-carboxylic acid) (PP3C) film on a gold coated grating substrate using pyrrole-3-carboxylic acid (P3C) monomer solution in 0.5 M H2SO4. In situ electrochemical transmission surface plasmon resonance (EC-TSPR), 1 measurements were carried out to study the kinetic and electroactivity properties of PP3C film. Immobilization of antihuman IgG on the activated surface and the binding process of human IgG and antihuman IgG in neutral solution could be detected in situ by EC-TSPR measurement. The surface modification steps on the PP3C layer led to an increase in intensity of the transmission peak. The performance, sensitivity, and utility of EC-TSPR spectroscopy showed obvious advantages for the detection of binding process with the simple experimental setup, and could be applied to the study of biomolecular interactions in various systems.

DOI： 10.1021/am300970m

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The optical/electrochemical and crosslinking properties of polycarbazole LbL films is studied using EC-SPR spectroscopy. The in situ electrochemical crosslinking and doping/de-doping properties are monitored for several different layered film structures. P4VPCBZ and PCEMMA are used as precursor polyelectrolytes, PAA and PDADMAC as non-crosslinkable polyelectrolytes, which are effective barrier layers for electron transfer. The changes in reflectivity and charge during CV illustrates that quantitative control of electrochemical crosslinking and doping/de-doping can be achieved by varying the composition of the precursor and counter-polyelectrolyte layers. The method may provide new opportunities for basic studies of model conjugated polymer systems and for electrooptic device applications.

DOI： 10.1002/mren.201100068

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We fabricated a hybrid sensor utilizing quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) spectroscopy. We confirmed its effectiveness by observing QCM frequency shifts and SPR wavelength changes for two processes: deposition of various transparent polymer thin films and moisture sorption. For thin-film deposition, the relationship between the QCM frequency and SPR wavelength was found to depend on the refractive index of the film material. For moisture sorption, the direction of SPR wavelength shift depended on the film thickness. This was estimated to be caused by film swelling and decrease in refractive index induced by moisture. (C) 2012 The Japan Society of Applied Physics

DOI： 10.1143/APEX.5.036603

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In this review, we introduce a variety of surface sensitive techniques for the study of organic thin films, and applications to organic devices. These studies include surface plasmon emission light, organic thin film transistors, combination of quartz crystal microbalance and optical waveguide spectroscopy, evaluation of alignment of liquid crystal molecules at surfaces, and biosensor applications.

DOI： 10.1587/transele.E94.C.1824

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Ridge optical waveguides (OWGs) of fluorinated polyimides were deposited on a quartz crystal microbalance (QCM), and a hybrid sensor employing the OWG spectroscopy and the QCM technique was prepared. A polyvinyl alcohol (PVA) film with CoCl2 was deposited on the OWG, and humidity sensing characteristics were investigated. White light was entered into the waveguide and the output light spectra was observed. The output light intensity markedly changed because of the chromism of CoCl2 by humidity sorption. During the output light measurement, the QCM frequency was monitored simultaneously. The humidity dependences of the QCM frequency and output light were also investigated in a range from 10% to 70%. Furthermore, the response to hydrofluoroether (HFE) was observed, and the change in the output light was hardly observed because CoCl2 does not exhibit chromism in HFE sorption.

DOI： 10.1587/transele.E94.C.1851

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DOI： 10.1002/9783527638482.ch22

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Thiolene-based microfluidic devices have been coupled with surface plasmon resonance imaging (SPRI) to provide an integrated platform to study interfacial interactions in both aqueous and organic solutions. In this work, we develop a photolithographic method that interfaces commercially available thiolene resin to gold and glass substrates to generate microfluidic channels with excellent adhesion that leave the underlying sensor surface free from contamination and readily available for surface modification through self-assembly. These devices can sustain high flow rates and have excellent solvent compatibility even with several organic solvents. To demonstrate the versatility of these devices, we have conducted nanomolar detection of streptavidin-biotin interactions using in situ SPRI. (C) 2011 American Institute of Physics. [doi:10.1063/1.3596395]

DOI： 10.1063/1.3596395

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In this study, we demonstrate the fabrication of grating-coupled surface plasmon resonance (SPR) enhanced organic thin-film photovoltaic cells and their improved photocurrent properties. The cell consists of a grating substrate/silver/P3HT:PCBM/PEDOT:PSS structure. Blu-ray disk recordable substrates are used as the diffraction grating substrates on which silver films are deposited by vacuum evaporation. P3HT:PCBM films are spin-coated on silver/grating substrates. Low conductivity PEDOT:PSS/PDADMAC layer-by-layer ultrathin films deposited on P3HT:PCBM films act as the hole transport layer, whereas high conductivity PEDOT:PSS films deposited by spin-coating act as the anode. SPR excitations are observed in the fabricated cells upon irradiation with white light. Up to a 2-fold increase in the short-circuit photocurrent is observed when the surface plasmon (SP) is excited on the silver gratings as compared to that without SP excitation. The finite-difference time-domain simulation indicates that the electric field in the P3HT: PCBM layer can be increased using the grating-coupled SP technique.

DOI： 10.1021/am200304x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KOREAN PHYSICAL SOC  

In this paper, the driving mechanism of carrier-generated organic field-effect transistors (OFETs) with pentacene and vanadium pentoxide (V(2)O(5)) layers is discussed. In this study, large on-currents were observed in an OFET with a 35-mm V(2)O(5) layer. Devices with aluminum (Al)/pentacene/V(2)O(5)/Al layer structures were also prepared. These devices exhibited a large current density in spite of their high carrier injection barriers between each layer and the Al electrodes. Moreover, new absorption bands corresponding to the radical cation absorption of pentacene were observed within the absorption spectrum of the pentacene and V(2)O(5) mixed layers. It was inferred that the charge transfer (CT) complexes that formed at the interface between the pentacene and V(2)O(5) layers were dissociated by the applied gate voltage and that the generated holes contributed to driving the OFETs.

DOI： 10.3938/jkps.58.1402

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SCIENTIFIC PUBLISHERS  

In this report, we demonstrate a novel way to tune the fluorescence property of electrospun conjugated polymer fibers. The basic strategy is to use a soluble precursor polymer with gold nanoparticies for electrospinning, which is then cross-linked by applying potential cycles in an electrochemical cell. Electroactive carbazole units in electrospun precursor polymer fibers were converted to conjugated polymer fibers. Since the conjugated polymer fibers can be formed, the fluorescence from the conjugated polymer fibers can be tuned by the rate of the conversion and doping of the fibers. Furthermore, the quenching of the fluorescence, which overlaps with the plasmon band of the gold nanoparticles, was observed. The quenching of the fluorescence properties of the fibers was dependent on the amount of gold nanoparticles inside the fibers.

DOI： 10.1166/jnn.2011.3648

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A half-cylindrical BK-7 prism/dielectric film with a grating/Ag film/fluorescent polymer film structure was prepared, and its surface plasmon (SP) excitation property was investigated. It was confirmed experimentally that SP excitations are possible in this structure by using prism and grating couplings. The SP excitation property depended on the direction of the grating vector. Furthermore, intense photoluminescence was observed when the SPs were simultaneously excited at the Ag/polymer interface by prism coupling and at the Cytop/Ag interface by grating coupling.

DOI： 10.1587/transele.E94.C.196

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DOI： 10.1143/JJAP.50.01BC15

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

An electrochemically controlled surface plasmon resonance (SPR) immunosensor for the detection of human immunoglobulin G (IgG) has been developed using poly(pyrrole-3-carboxylic acid) (PP3C) film. In this work, a pyrrole-3-carboxylic acid monomer was used for electropolymerization of a PP3C film on a gold-coated high-refractive-index glass slide. In situ electrochemical (EC)-SPR spectroscopy was performed to study the kinetic property and electroactivity property of the PP3C film. Moreover, ultraviolet-visible (UV-vis) spectroscopy was performed to characterize the PP3C film. Finally, the immunosensor-based PP3C film was constructed. The carboxylic acid surface of the PP3C film was activated for the immobilization of anti-human IgG. The immunosensor electrode was used for probing the binding reaction of anti-human IgG/human IgG with several concentrations of human IgG at different constant applied potentials. The probe immobilization and immunosensing process were in situ monitored by EC-SPR technique. The sensitivity of the sensor was improved by controlling the morphology of the PP3C film by applying the potential. (C) 2011 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.50.01BK02

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Gold nanoparticles (AuNPs) have a unique property called localized surface plasmon resonance (LSPR). LSPR excitation wavelength is strongly dependent on size of gold nanoparticles. At the LSPR wavelength, gold nanoparticles exhibit an enormous electric field enhancement extended from their surface. We have been synthesized gold nanoparticles using chemical reduction of hydrogen tetrachloroaurate (HAuCl4) with sodium borohydride (NaBH4). The soluble starch was used as a stabilizer. The pH of gold salt solution and concentration of stabilizer were varied to investigate the change of the size and stability of gold nanoparticles. Under basic condition, the gold ion was easily reduced to gold nanoparticles. Then, the smaller size of gold nanoparticles could be observed. The concentration of starch solution also affected on the size and stability of gold nanoparticles. The size of gold nanoparticles was increased with the decreasing of starch concentration. In this work, grating pattern of gold nanoparticles was prepared by imprinting method. There is a possibility to use the grating pattern of gold nanoparticles in SPR grating-coupling method.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

In this paper, we demonstrate the fabrication of grating-coupled surface plasmon resonance (SPR)-enhanced dye-sensitized solar cells (DSSCs) and their increased short-circuit current properties. DSSCs consisted of a grating substrate/gold/TiO2/dye/electrolyte/indium-tin oxide structure. Blu-ray disc recordables were used as diffraction grating substrates on which gold films were deposited by vacuum evaporation. TiO2 films were prepared on the gold/grating substrates by an electrophoretic deposition technique. 5,10,15,20-Tetrakis (1-methyl-4-pyridinio) porphyrin tetra (p-toluenesulfonate) and sodium copper chlorophyllin layer-by-layer ultrathin films were deposited as the dye layer on the TiO2 films. SPR excitation was observed in the fabricated cells upon irradiation with white light. Up to 4.5-fold increase in the short-circuit photocurrent was observed when the surface plasmon (SP) was excited on the gold gratings as compared with that without SP excitation. Finite-difference time-domain simulation indicated that the electrical field in the dye layer could be increased using the grating-coupled SP technique.

DOI： 10.1039/c1jm12935j

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

Organic field-effect transistors (OFETs) were fabricated using pentacene thin layer, and the effects of inserted Lewis-acid thin layers on electrical properties were investigated. The OFETs have active layers of pentacene and vanadium pentoxide (V2O5) as a Lewis-acid layer. Typical source-drain current (I-DS) vs. source-drain voltage (V-DS) curves were observed under negative gate voltages (V(G)s) application, and the shift of the threshold voltage for FET driving (V-t) to positive side was also observed by V2O5 layer insertion, that is, -2.5 V for device with V2O5 layer and -5.7 V for device without V2O5 layer. It was thought that charge transfer (CT) complexes which were formed at the interface between pentacene and V2O5 layer were dissociated by the applied gate voltage, and the generated holes seem to contribute to drain current and the apparent V-t improvement.

DOI： 10.1063/1.3666646

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this work, electropolymerization of carboxylated conducting polymer/CNTs composites have been studied for construction of surface plasmon resonance immunosensor. The electrochemical experiment was performed in 1.0 M tetrabutylammonium hexafluorophosphate (TBAPF(6)) in acetonitrile containing 10 mM monomers, thianaphthene-2-carboxylic acid and benzothiophene-2-propanoic acid, and CNTs in acetonitrile at scan rate of 20 mV/s using platinum wire as counter electrode and Ag/Ag+ as reference electrode with potential range of 0 V to 1.2 V for 5 cycles. The gold and ITO-coated glass substrates were used as working electrode where the electropolymerization was occurred. The obtained films were characterized by UV-vis absorption spectroscopy, atomic force microscopy and in situ electrochemical-surface plasmon resonance spectroscopy. Further studies about immobilization process are under investigating for this immunosensor system.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A hybrid sensor of quartz crystal microbalance (QCM) and optical waveguide (OWG) spectroscopies was prepared, and in-situ observations were carried out for lead phthalocyanine (PbPc) film depositions using vacuum evaporation technique. The peak wavelength of the absorption spectra changed with the PbPc film thickness. The responses of QCM frequency and optical absorption were also observed, and they suggested the phase formation changed with the thickness. Furthermore, the X-ray diffraction (XRD) pattern and the atomic force microscope (AFM) image were investigated for the film.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The self-assembled monolayer formation of a series of thiophene dendron thiols with different generations and alkyl chain lengths onto gold surfaces is studied. Average film thicknesses and dielectric constants were calculated from SPR using a two-subphase differential method. The in situ adsorption of the thiophene dendron thiols was monitored by SPR kinetics measurements and fitted using an empirical three-step model. Electrochemical redox molecular probing experiments provided additional insight into surface coverage, which showed different abilities to block electron transfer at the monolayer/electrode interfaces. The surface coverage of the films was also estimated by QCM measurements and supported by static WCA measurements.

DOI： 10.1002/macp.201000427

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In this Article, we present a novel method to detect adrenaline on poly(3-aminobenzylamine) (PABA) ultrathin films by electrochemical-surface plasmon resonance (EC-SPR) spectroscopy. We prepared a PABA film, which specifically reacts with adrenaline, on a gold electrode by electropolymerization of 3-aminobenzylamine. The specific reaction of benzylamine within the PABA structure with adrenaline was studied by XPS, UV-vis spectroscopy, and EC-SPR techniques. Adrenaline was detected in real time by EC-SPR spectroscopy, which provides simultaneous monitoring of both optical SPR reflectivity and electrochemical current responses upon injecting adrenaline into the PABA thin film. The number of changes in both current and SPR reflectivity on the injection of adrenaline exhibited the linear relation to the concentration, and the detection limit was 100 pM. The responses were distinctive to those for uric acid and ascorbic acid, which are major interferences of adrenaline.

DOI： 10.1021/la1034992

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The in situ electrochemical and dielectric film properties of monomer co-electropolymerization with a CPN precursor was investigated. A polysiloxane/polythiophene precursor was electropolymerized with thiophene monomer at different composition ratios using cyclic voltammetry. This was investigated in situ by EC-SPR spectroscopy and EC-SPFELS. The characteristic oscillations corresponded to distinct transitions in film deposition. The resonance coupling of the SPR decreased with higher thiophene monomer content. Increasing the amount of thiophene monomer increased the RMS roughness of the film as observed by AFM, which corresponded to an increase in scattered light intensity with EC-SPFELS.

DOI： 10.1002/macp.201000471

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In this paper, we demonstrate photocurrent generation from nanostructured layer-by-layer (LbL) ultrathin films consisting of chromophores and single-walled carbon nanotubes (SWNT). We fabricated 5,10,15,20-tetrakis(1-methy1-4-pyridinio)porphyrin tetr (p-toluenesulfonate) (TMPyP)-SWNT/sodium copper chlorophyllin (SCC)-SWNT LbL film from noncovalently adsorbed composites. SWNT were dissolved in water-soluble cationic TMPyP and anionic SCC, and the resulting solutions were used for electrostatic LbL multilayer fabrication. The solubility of SWNT in water was studied by UV-vis absorption spectroscopy. The composites were highly dispersed owing to the pi-pi interactions. The fluorescence spectroscopy measurements showed efficient quenching of TMPyP and SCC fluorescence, which was due to the interaction with SWNT. In situ surface plasmon resonance spectroscopy during the LbL multilayer fabrication indicated a stepwise increase in reflectivity, implying the successive formation of nanostructured hybrid ultrathin films. Cyclic voltammetry revealed that the electroactivity of the hybrid film was enhanced by the incorporation of SWNT. The composite LbL film electrode exhibited an enhancement of photocurrent compared to a TMPyP/SCC (no SWNT) film electrode, suggesting efficient charge separation and electron transfer in the system.

DOI： 10.1021/jp103121m

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In this work we report an electrochemical surface plasmon resonance/waveguide (EC-SPR/waveguide) glucose biosensor that could detect enzymatic reactions in a conducting polymer/glucose oxidase (GO(x)) multilayer thin film. In order to achieve a controlled enzyme electrode and waveguide mode, GO(x) (negatively charged) was immobilized with a water-soluble, conducting N-alkylaminated polypyrrole (positively charged) using the layer-by-layer (LbL) electrostatic self-assembly technique. The electrochemical and optical signals were simultaneously obtained from the composite LbL enzyme electrode upon the addition of glucose as mediated by the electroactivity and electrochromic property of the polypyrrole layers. Signal enhancement in EC-SPR detection is obtained by monitoring the doping=dedoping events on the polypyrrole. The real-time optical signal could be distinguished between the change in the dielectric constant of the enzyme layer and other nonenzymatic reaction events such as adsorption of glucose and the change of the refractive index of the solution. This was possible by correlation of both the SPR mode and the m = and 1 modes of the waveguide in an SPR/waveguide spectroscopy experiment.

DOI： 10.1021/am100373v

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An electrochemically controlled surface plasmon resonance (SPR) immunosensor based on carboxylated polyaniline was constructed for detecting human immunoglobulin G (IgG) without using further labeled molecules. The carboxylated polyaniline, poly(3-aminobenzoic acid) (PABA), was prepared by electropolymerization of its monomer, 3-aminobenzoic acid (ABA), on a gold-coated high-refractive-index glass slide that was also used as a working electrode for the electrochemical system. The kinetic properties during electropolymerization were monitored in situ with electrochemical-surface plasmon resonance (EC-SPR) spectroscopy. The obtained PABA film, which was used to construct the immunosensor, showed electroactivity in neutral phosphate-buffered saline solution. The carboxylic acid surface of the PABA film was then activated to immobilize anti-human IgG. Finally, the immunosensor electrode was used to probe the binding reaction of anti-human/human IgG with various concentrations of human IgG at different constant applied potentials. The immobilization and binding reaction processes were controlled and also studied in situ by EC-SPR spectroscopy. The binding process at different applied potentials was studied and fitted using the Freundlich model. The surface morphology of the films after the immobilization of anti-human IgG was studied by atomic force microscopy. (c) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2010.03.031

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1541/ieejfms.130.219

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DOI： 10.1541/ieejfms.130.193

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DOI： 10.1541/ieejfms.130.193

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In this report, we demonstrate a convenient method of fabricating single-walled carbon nanotubes/organic semiconductor hybrid ultrathin multilayers using a layer-by-layer self-assembly approach. Single-walled carbon nanotubes were solubilized by water-soluble cationic alcian blue pyridine variant and anionic copper phthalocyanine-3,4',4 '',4'''-tetrasulfonic acid tetrasodium salt, which were then utilized for electrostatic layer-by-layer multilayer fabrication. The solubilization ability of single-walled carbon nanotubes was studied in water by UV-vis absorption spectroscopy. The composites were highly dispersed owing to the pi-pi interactions. In situ surface plasmon resonance spectroscopy during the layer-by-layer multilayer fabrication indicated a stepwise increase in reflectivity, indicating the successive formation of nanostructured hybrid ultrathin films. Cyclic voltammetry revealed that the electroactivity of the hybrid film was enhanced by the incorporation of single-walled nanotubes. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2009.09.052

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

In this study, we report on evaluation of liquid crystal (LC) cells using simultaneous surface plasmon resonance (SPR) and optical waveguide spectroscopy (OWS) technique in attenuated total reflection configuration. This technique allows for in-situ monitoring of alignment property of LC molecules adjacent to the surface and the bulk in the LC cell simultaneously. An increase of the hysteresis both for near the surface and whole cell was observed in SPR/OWS kinetic properties as the number of voltage cycling increased. The LC alignment properties after applying a DC voltage were also measured to study the effect of impurity residual ions in LC cells.

DOI： 10.1080/15421401003609764

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

Polymer fibers were prepared by an electrospinning method utilizing a copper wire electrode in a capillary tube. The morphology of electrospun poly(vinyl alcohol) (PVA) fibers was observed, and was found to be dependent on the wire electrode tip position in the capillary tube, the concentration of the polymer solution, the distance between the electrodes, and the applied voltage. By using the wire electrode, the experimental setup is simple and the distance between the electrodes and the applied voltage can be easily reduced. Furthermore, the preparation of poly(3-hexylthiophene) (P3HT) fibers was carried out. P3HT fibers were successfully prepared by mixing poly(ethylene oxide) (PEO) in P3HT solution. Orientation control was also carried out by depositing the fibers on a rotating collector electrode, and the alignment of the P3HT: PEO fibers was confirmed. Anisotropy of the optical absorption spectra was also observed for the aligned fibers. (C) 2010 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.49.04DK24

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In this study, we report the evaluation of the tilt angle of liquid crystal (LC) molecules near the surface of SiO2 alignment layers and in the whole cell when AC and/or DC voltages are applied. The LC molecule 4-cyano-4'-n-pentylbiphenyl was used. The LC cell consisted of a Au (50 nm)/SiO2 (30 nm)/LC (3 mm)/SiO2 (30 nm)/Au (100 nm) system. Surface plasmon resonance (SPR) spectroscopy and optical waveguide spectroscopy (OWS) in an attenuated total-reflection configuration were used to monitor the alignment properties of LC molecules. From the SPR/OWS angular scan properties, the profile of the tilt angle from the surface to inside the cell was obtained. Furthermore, the effect of space-charge polarization on the LC alignment properties was observed from the SPR kinetic properties. As demonstrated in this report, this technique should provide useful information for understanding the interfacial phenomena in LC displays. (C) 2010 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.49.04DK22

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In this work, we demonstrate multimode surface plasmon (SP) excitations by white light irradiation on metallic diffraction grating/plastic substrates. Recordable compact discs were used as the diffraction grating substrates on which silver films were deposited by vacuum evaporation. Since the grating pitch (1.6 mu m) was larger than that of diffraction gratings commonly used for the excitation of SPs, multimode SP excitations due to several diffraction orders were observed simultaneously in the wavelength region from 400 to 800 nm. The obtained SP excitations were then compared with the calculated SP dispersion on the grating. The multimode SP excitations were further studied on spin-coated poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) thin film/silver grating substrates. An increased photoluminescence intensity due to SP excitations was observed on MEH-PPV/silver grating surfaces. (C) 2010 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.49.01AE02

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Organic field-effect transistors (OFETs) were fabricated using poly(3-hexyl thiophene) (P3HT), and the effects of inserted Lewis-acid thin layers on electrical properties were investigated. The OFETs have active layers of P3HT and vanadium pentoxide (V2O5) as a Lewis-acid layer. Larger drain currents were observed for the OFET with the V2O5 layer than that without the layer. The calculated field-effect mobility of the fabricated OFET was 1.4 x 10(-2) cm(2) / (Vs), where as that of the OFET without the V2O5 layer was 6.2 x 10(-3) cm(2) / (Vs). It was thought that charge transfer (CT) complex which was formed at the interface between P3HT and V2O5 layer was dissociated by gate voltage, and the generated holes seem to contribute to drain current and the apparent high mobility.

DOI： 10.1080/15421401003597977

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The attenuated total reflection (ATR) and emission light properties utilizing surface plasmon (SP) excitations were measured for the electrochemical change of poly(3-hexylthiophene-2,5diyl) (P3HT) thin films in-situ. The SP emission light could detect the SP excited by molecular luminescence of P3HT. The ATR and SP emission light properties were observed for the doped-dedoped states of P3HT thin film. The ATR and SP emission light properties were remarkably changed with the electrochemical doping and dedoping. The SP emission light also decreased by decrease of the molecular luminescence of P3HT by doping. For the dedoped-state P3HT thin film, SP emission light also increased by increase of the molecular luminescence. The SP emission light excited by molecular luminescence can be controlled by the control of doping-dedoping state. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2009.07.083

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In this study, stab and ridge optical waveguides (OWGs) made of fluorinated polyimides were deposited on a quartz crystal microbalance (QCM), and hybrid sensors using OWG spectroscopy and the QCM technique were prepared. Polyvinyl alcohol (PVA) film with CoCl(2) was deposited on the OWGs, and the characteristics of humidity sensing were investigated. A prism coupler was used to enter a He-Ne laser beam (lambda = 632.8 nm) to the slab OWG. The output light intensity markedly changed due to chromism of the CoCl(2) as a result of humidity sorption, and this change was dependent on the incident angle of the laser beam to the slab OWG. During the measurement of output light, the QCM frequency was simultaneously monitored. The humidity dependence of the sensor with the slab OWG was also investigated in the range from 15 to 85%. For the sensor with the ridge OWG, white light was entered by butt-coupling, and the characteristics of humidity sensing were investigated by observing the output light spectrum and the QCM frequency. (C) 2009 Published by Elsevier B.V.

DOI： 10.1016/j.tsf.2009.07.059

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOCIETY APPLIED PHYSICS  

Organic field-effect transistors (OFETs) with copper phthalocyanine (CuPc) and vanadium pentoxide (V(2)O(5)) films were fabricated (top-contact electrode/V(2)O(5)/CuPc/SiO(2)/Si/gate electrode structure), and their electrical properties were investigated. The drain current increased due to the insertion Of V(2)O(5) layer, and it was considered to be due to a formation of charge transfer complex between V(2)O(5) and CuPc. The ON/OFF ratio of the OFETs was higher than that of previously reported OFETs with a top-contact electrode/CuPc/V(2)O(5)/SiO(2)/Si/gate electrode structure. The off-current of the OFETs in this study was maintained small so that few carriers would contribute to the current conduction in the off-state. (C) 2009 The Japan Society of Applied Physics

DOI： 10.1143/APEX.2.071502

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In this study, micro/nanopatterning and assembly of single-walled carbon nanotube-organic semiconductor composites using dip-pen nanolithography, microcontact printing and fountain-pen nanolithography techniques are described. First, the solubilization abilities of carbon nanotubes with Alcian blue-tetrakis(methyl pyridium) chloride (AB) are investigated by UV-visible spectroscopy. The assembly of the composites obtained by microcontact printing technique shows well-ordered monolayers of 1 mu m linewidth pattern. Dip-pen nanolithography shows that 11 nm height and 100 nm linewidth can be obtained on silicon wafer substrates. Finally, fountain-pen nanolithography is shown as a possible large-scale carbon nanotube assembly technique.

DOI： 10.1088/0957-4484/20/8/085301

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We report a way of using citrates, ionic capping molecules on gold nanoparticles, as a "tuner" to adjust the charge density on the particles by solution pH, in correlation with their association constants (pKa). We have synthesized 10% biotin-capped gold nanoparticles with 90% citrates covering on the remaining surfaces. The controlled electrostatic repulsion force between the particles determines the distance between the particles on substrate, i.e., the surface density of the particles, even for the case of immobilization via biotin-avidin reaction. Thus the density of gold nanoparticles on surface was varied in a wide range systematically, especially to high density, and the optical response of two dimensional particle aggregates was investigated to discuss the effect of local plasmon coupling. The UV-vis-Near-IR reflection absorption spectrum of the particle aggregates at low pH (pH < pKa2) appeared with a transverse resonance at ca. lambda = 520 nm and a longitudinal resonance widened and red-shifted to lambda = 680 nm. Surface plasmon resonance (SPR) curve of the aggregates exhibits a large shift of the minimum angle position together with a significant increase of the minimum intensity (dip-up), as opposed to a small angle shift and no dip-up for well-dispersed particles. The deviation from the SPR simulation curves based on the Maxwell-Garnett (MG) theory clearly indicates the effect of local plasmon coupling in aggregates. The Kramers-Kronig transformations of the UV-vis-Near-IR spectra and the SPR data analyses with Fresnel's equations state the increase of the effective dielectric constants of the particle layers with the density of the particles and the formation of aggregates.

DOI： 10.1166/jnn.2009.J066

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We demonstrate nanofabrication of photoreactive azobenzene molecular thin films using optical migration of molecules induced by local polarization in optical near-fields. Transportation and alignment control of the nanomaterial systems were investigated to modulate the excitation of the optical near-fields. Energy transfers from fluorescent molecules were observed along a planar boundary system of metals and dielectrics. The fundamental processes of tunneling energy that flowed to the metallic layer were evaluated from the angular distribution of scattered light in a far field, corresponding to the angular spectrum of scattered fields, including those of evanescent waves excited near the fluorescent molecules and nanostructures fabricated on azo molecular films.

DOI： 10.1117/12.825955

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

A new Mach-Zehnder type optical-interferometer utilizing evanescent wave illuminations of a reflected beam at a prism surface was constructed to evaluate photoreactive molecular thin films on a prism surface. Refractive index changes of the films due to photoisomerization of azo molecules on the prism caused by an irradiation beam were observed from phase changes between an incident beam and the reflected one at the prism surface. Real-time measurements were also demonstrated using the interferometer microscopy, exhibiting two dimensional distributions of the refractive indices in the molecular films partially excited by the focused irradiation laser beam.

DOI： 10.1080/15421400902946103

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

Attenuated total reflection (ATR) property utilizing surface plasmon (SP) excitation was investigated for BK-7 prism/MgF2/Ag film/fluorescent organic dye film structure. In the structure, it is expected that SPs are excited at MgF2/Ag and Ag/dye film interfaces by Otto and Kretschmann configurations, respectively. In the experimental ATR curve, reflection dips for the SP excitations at the interfaces could be detected. Furthermore. SP emission lights were observed by irradiation of Ar ion laser beam from the dye film side. The SP emission light curve with two peaks was observed and it was also considered that the peaks corresponded to the SP excitation of Otto and Kretschmann Configurations. The SP emission light spectra indicated the excited fluorescent dyes induced the SP emission lights. Intense emission light of Otto configuration was observed in this sample.

DOI： 10.1093/ietele/e91-c.12.1883

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In this report. we demonstrate electrocatalytic oxidation properties of ascorbic acid at poly(3,4-ethylenedioxythiophene) (PEDOT) thin films in view of their potential application for big-sensing devices. PEDOT thin films were deposited on gold thin films by electropolymerization of EDOT monomer in acetonitrile solvent. In-situ electrochemical-surface plasmon resonance spectroscopy (EC-SPR) was used to detect both electrochemical and optical signals upon an injection of ascorbic acid.

DOI： 10.1093/ietele/e91-c.12.1881

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In this study, attenuated total reflection (ATR) utilizing surface plasmon (SP) excitation and SP emission lights were observed for the adsorption of polystyrene (PS) spheres and a water-soluble polymer. The PS spheres contained fluorescent dyes and exhibited red fluorescence. The ATR properties indicated film deposition with increasing number of adsorption cycles. The SP emission light induced by the fluorescent dye ill the spheres was also measured. and all increase in the peak intensity, as well as an angle shift. was observed. Furthermore, the SP emission light spectra were investigated at various emission angles. The dispersion relation obtained front the SP emission light almost corresponded to that obtained from the ATR curves.

DOI： 10.1093/ietele/e91-c.10.1663

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Developing highly selective and sensitive chemical sensors is a challenge with respect to new materials for chemical recognition. In this study, a new conjugated polymer network precursor, hexahomotriazacalix[3]arene-carbazole has been synthesized and electrochemically cross-linked to form ultrathin films using cyclic voltammetry. The incorporation of hexahomotriazacalix[3]arene moiety as a neutral cation-binding receptor into a conjugated polycarbazole network facilitates high selectivity and sensitivity for Zn(2+). The ultrathin films were characterized spectroscopically using UV-vis absorption and fluorescence spectroscopy. Surface morphology properties were examined by atomic force microscopy. Electrochemical deposition parameters and sensor transduction was studied by an electrochemical quartz crystal microbalance, surface plasmon resonance spectroscopy, and open-circuit potentiometry techniques. The results indicate that the high selectivity and sensitivity for Zn(2+) compared to those of other cations is due to the combined size and dipole specificity of the azacalixarene unit and nonspecific ionic interaction with the redox couple of the conjugated polycarbazole units.

DOI： 10.1021/cm800284h

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Nanostructured ultrathin films of linear and dendrimeric cationic sexithiophenes, 6TNL and 6TND, respectively, alternated with anionic polycarbazole precursor, poly(2-(N-carbazolyl) ethyl methacrylate-co-methacrylic acid) or PCEMMA32, were successfully fabricated using the layer-by-layer self-assembly deposition technique. The two electro-optically active oligomers exhibited distinct optical properties and aggregation behavior in solution and films as studied by UV-vis and fluorescence spectroscopy. The stepwise increase of the 6TNL/PCEMMA32 and 6TND/PCEMMA32 layers was confirmed by UV-yis spectroscopy and in situ surface plasmon resonance (SPR) spectroscopy. The intralayer electrochemical polymerization and cross-linking behavior of the carbazole functionalized PCEMMA32 layers were then investigated using cyclic voltammetry (CV) and electrochemical surface plasmon resonance (EC-SPR) spectroscopy. The increase in current with each cycle confirmed intralayer cross-linking followed by the doping-dedoping process within these films. The two types of films differed with respect to dielectric constant and thickness changes before and after electropolymerization, indicating the influence of the oligothiophene layers. This demonstrated for the first time the preparation of highly ordered organic semiconductors alternated with in situ electropolymerizable layers in ultrathin films.

DOI： 10.1021/la800307u

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Carbazole containing ligand dendrons are designed based on second generation polybenzyl ether dendrons (2GPO). This is subsequently used for directly synthesizing and capping CdSe nanoparticles in contrast to ligand exchange for introducing functionality. The stable hybrid CdSe-2GPO quantum dot nanoparticles have characteristic energy-transfer properties from the donor carbazole peripheral groups to the acceptor CdSe nanoparticles, i.e., overlap of the fluorescence of the carbazole with the absorbance of the CdSe nanoparticle resulting in an enhanced fluorescence with concentration through F6rster resonance energy transfer (FRET). However, electropolymerization of the peripheral electroactive carbazole units result in a red-shift in absorbance and quenching in fluorescence. This is attributed to a reversed molecular orbital energy order with respect to the electropolymerized carbazole dendron and CdSe nanoparticle. The hole-transfer results in fluoresence quenching and charge transfer between the CdSe nanoparticles and the polycarbazole peripheral units. The photoelectric alteration may yet provide for an interesting electro-optical or sensing device application based on electrochemical properties of the hybrid material.

DOI： 10.1002/adfm.200701201

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

In this study, thin films of poly(vinyl alcohol) (PVA) mixed with 100 nm polystyrene (PS) microspheres were prepared, and changes in attenuated total reflection (ATR) utilizing surface plasmon (SP) excitation due to the adsorption of humidity were investigated. The PS microspheres contained luminescent dyes, and SP emission light due to these dyes was observed. The sample configuration was prism/Ag film (50 nm)/PVA film with sphere. ATR dip and SP emission peak angles shifted with the adsorption and desorption of humidity, and SP emission light intensity changed markedly. Furthermore, kinetic curves were plotted and humidity adsorption responses were repeatedly observed. Finally, the dispersion relations of SPs were obtained from ATR and SP emission light properties.

DOI： 10.1143/JJAP.47.1110

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Vapor treatments using several organic solvents were carried out for vacuum-evaporated magnesium phthalocyanine (MgPc) thin films. The UV-vis absorption spectra, surface morphologies, and X-ray diffraction patterns were markedly altered by the treatments and depend on the vapor. Furthermore, Au top-contact organic field-effect transistors (OFETs) were fabricated using MgPc films with and without the vapor treatments. The FET with N-methylpyrrolidone treatment did not work, but that with dichloromethane vapor treatment showed a large improvement in the on/off ratio and field-effect mobilities. Ethanol vapor treatment (5 min) also improved the FET characteristics, but long-term treatment (60 min) induced poor performance.

DOI： 10.1143/JJAP.47.484

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The preparation and properties of an electrochemically crosslinked Au nanoparticle/polyvinylcarbazole (PVK)/polyfluorene (PFC) nanocomposite film is described. Blends of the blue-light emitting PFC, PVK, and the 11-(9H-carbazol-9-yl)-undecane-1-thiol-capped Au nanoparticles (CBZ-S-Au) were prepared as thin films by spin-coating and subsequent crosslinking by cyclic voltammetry (CV). The electrochemical properties are then evaluated on the basis of the redox behavior (reversibility) and electron-transport properties of the films. They are further characterized by UV-vis spectroscopy, photoluminescence spectroscopy, and atomic force microscopy (AFM). The large differences in photoluminescence properties of the CBZ-S-Au/PFCVK crosslinked copolymer composite film compared to the PFCVK polymer alone result in an efficient energy-transfer system, in which the excimer peak is almost totally quenched. This indicates a compatible match between the absorbance of the An plasmons and the emission of the excimer energy trap from PF polymers. Furthermore, electrochemical crosslinking enhances this match both by shifting the absorbance to greater overlap and decreasing the Forster distance between the Au nanoparticle and the PFCVK polymer chains.

DOI： 10.1002/adfm.200700972

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：INST ELECTR ENGINEERS JAPAN  

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DOI： 10.1109/ISEIM.2008.4664451

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In this short review paper, we summarize some of our ideas to utilize gold nanoparticles for the enhancement of surface plasmon resonance signals on DNA microarray. The hybridization of target-DNA capped gold nanoparticles with probe DNA on surface provides ca. ten times stronger optical contrast compared with that of target-DNA molecules. Our simulation result based on the Maxwell-Garnet theory explains well our experimental data and proves a potential of metallic nanoparticles for the substantial sensitivity enhancements for biosensor application in DNA diagnostics and bio-affinity studies, which leads to the fabrication of high resolution DNA microarrays.

DOI： 10.1007/s11468-007-9035-x

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We have developed a new methodology to fabricate high-resolution DNA microarrays (2500 dots/cm(2)) in combination with microcontact printing (mu CP) and surface plasmon resonance (SPR) imaging. A novel COOH-terminated PEG-disulfide with para-carborane (p-carborane) was synthesized as an initiator chemically bound to a gold substrate for surface coupling reactions with NH2-terminated DNA. The hybridization between target DNA immobilized on gold nanoparticles and probe DNA arrayed on flat gold substrates was successfully demonstrated by SPR imaging, where nonspecific adsorption was not observed at the array background. The gold nanoparticles on the array give quite high contrast even at low surface coverage with gold nanoparticles (similar to 10%) by the enhancement effect of optical signals based on nanoscale phenomena. This enhancement effect can be well described by the simulation based on the Maxwell-Garnett theory for the effective dielectric constants and Fresnel's equation.

DOI： 10.1021/jp070524m

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Ultrathin films of a cross-linked and chemically distinct conjugated poly(p-phenylene) network via electropolymerization are described. The amphiphilic network precursor was synthesized by incorporating the alkoxy carbazole group (-O(CH2)(5)Cb) to a poly(p-phenylene) (C6PPPOH) backbone. In order to investigate the combined thin film electrochemical and photophysical properties of poly(p-phenylene)s and polycarbazole conjugated polymers, C6PPPC5Cb was deposited on substrates using the Langmuir Blodgett Kuhn (LBK) method. The monolayer isotherm of the polymer, C6PPPC5Cb, showed a liquid expanded region slightly different from the parent polymer C6PPPOH. Multilayers (up to 30 layers) were transferred to different substrates such as quartz, gold coated LaSFN9 and ITO substrates for analysis. For conversion to a conjugated polymer network (CPN) film, the electroactive carbazole group was electropolymerized using cyclic voltammetry (CV) resulting in polycarbazole linking units. The differences in the film properties and corresponding changes in the electrochemical behavior indicate the importance of film thickness and electron/ion transport process in cross linked network films. From the electrochemical studies, the scan rate was found to have a considerable effect on electropolymerization with higher oxidation and reduction peak values found for the rigid network polymer compared to the uncrosslinked polymers.

DOI： 10.1021/jp070127b

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DOI： 10.1021/la061820d

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DOI： 10.1021/jp075986e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Nanomolar detection and specific recognition of pinacolyl methylphosphonate (PMP), a hydrolysis product and an analog of a relatively persistent class of toxic nerve agents, has been achieved. In addition, picomolar sensitivity is observed with methylphosphonic acid (MPA), an end-hydrolysis product for all organophosphate-based nerve agents. This is achieved using a combined surface plasmon resonance (SPR) and potentiometry setup. A modified polyamidoamine (PAMAM) carbazole/Cu2+ dendrimer, which is electrochemically crosslinked on a self-assembled monolayer (SAM) modified An substrate, is used as an active sensing element for trapping the nerve-agent analogs. The ultrathin films have been used to study the anchoring of nerve agents via non-covalent interactions. The carbazole to amine ratio is optimized to ensure free primary amines are available to interact with the analyte and the Cu2+ ions present in the system, which further enhances the selectivity. The carbazole group on the periphery serves a dual purpose: crosslinking the dendrimers to form a conjugated network film, and generating the potentiometric response. The adsorption kinetics are monitored by using an in situ SPR/potentiometric setup. This technique not only offers a real-time dual detection of highly toxic nerve-agent analogs, but also shows viability for future sensor-device applications.

DOI： 10.1002/adfm.200600147

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The electro-nanopatterning and mechanism of pattern formation in azobenzene-containing layer-by-layer (LbL) ultrathin films is described using surface probe microscopy techniques. First, arrays of nanodots were patterned on these films to investigate applied time at constant voltage bias dependence in electro-nanopatterning. The anisotropic mass transport and polar alignment of the azobenzene-containing films were observed after applying the electric field and heating the sample locally with the cantilever tip. On the basis of this novel phenomenon, small-sized surface relief gratings (SRG)s and their alignment were fabricated and observed by current-sensing atomic force microscopy. The rate of mass transport for the polymer is mainly controlled by the applied time at constant voltage bias between the cantilever and the electrode/substrate.

DOI： 10.1021/jp063955y

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Biotin-capped gold nanoparticles assembled on flat gold with volume fraction f are studied by surface plasmon resonance (SPR) spectroscopy and atomic force microscopy (AFM) in order to estimate the dielectric function of the gold nanoparticles based on the Maxwell-Garnett (MG) theory. The complex dielectric function (epsilon', epsilon") of the spherical nanoparticles at three representative wavelengths in the vis-near-IR region, i.e., lambda = 543, 632.8, and 1152 nm, is estimated for a surface homogeneously covered with nanoparticles in order to discuss the wavelength dependence of the dielectric function. The SPR response of a surface covered with particles in 2D aggregates is also analyzed. The experimental SPR curve of the particle aggregates deviates from the theoretical predictions, suggesting dipole interactions between particles.

DOI： 10.1021/jp062004h

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We report the simultaneous in situ electrochemical, optical, and surface morphological studies of conjugated polymer ultrathin film formation using a novel combined electrochemical instrumentation-surface plasmon resonance spectroscopy-atomic force microscopy. The initial stages of the electropolymerization of poly(3,4-ethylenedioxythiophene) films on flat gold electrode/substrates were observed in all three experiments simultaneously. In addition to the electrochemical information obtained, the surface plasmon optical technique showed the deposition of the film, and provided electrochromic behavior of the deposited film. Simultaneously, atomic force microscopy gave surface morphological properties and domain growth of the film. The complementarity of the information obtained from the combined techniques is useful for the investigation of polymer growth mechanism between cyclic voltammetry and potentiostatic deposition methods. (c) 2006 American Institute of Physics.

DOI： 10.1063/1.2204587

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In this work, we describe the synthesis and electropolymerization of conjugated substituted polyacetylenes, poly(N-alkoxy-(p-ethynylphenyl)carbazole) or PPA-Cz-Cn with electropolymerizable carbazole side groups to form conjugated polymer network (CPN) films. The phenylacetylene monomer was functionalized with a carbazole group separated by an alkylene spacer. Polymerization of the monomer in solution is accomplished using a Rh catalyst to form a "precursor polymer". The electrochemical behavior and cross-linking of the carbazole side group was then investigated by cyclic voltammetry (CV) and spectroelectrochemistry. A trend in the redox electrochemical behavior was observed with varying alkyl spacer length between the poly(phenylacetylene) backbone and carbazole side-group. The resulting film combines the electrooptical properties of the conjugated poly(phenylacetylene) polymer with polycarbazole units in a cross-linked electropolymerized film as evidenced by the CV and spectroelectrochemical behavior. This study emphasizes the preparation of polymer materials with mixed pi-conjugated species arising from the electrochemical cross-linking of a designed precursor polymer.

DOI： 10.1021/ma0510946

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Photodegradation and photocrosslinking of benzophenone blended polystyrene (PS) thin films were investigated primarily using Fourier transform infrared (FT-IR) imaging, evanescent waveguide spectroscopy (WS), and quartz crystal microbalance (QCM) methods. The main objective is to observe the changes (spectral and chemical) indicative of these competitive processes in an ultrathin polymer film. This also serves as a model study in the application of combined spectroscopic, optical, and acoustic methods towards understanding crosslinking and degradation phenomena within the same time frame of observation. To induce photocrosslinking, 1, 1 2-dodecanediyibis(oxy-4, 1-phenylene)] [bis[phenylmethanone] (2BP12), a small molecule with two benzophenone groups, was blended with PS in solution, spincast onto glass and silicon substrates, and irradiated with ultraviolet light. Photodegradation and benzophenone-mediated crosslinking were observed both directly via functional group spectroscopies and indirectly via their effects on thin film surface properties and morphologies. Atomic force microscopy (AFM) and QCM were used to elucidate local morphology change and mass-uptake kinetics in the presence Of 02 in air, respectively. All results correlated well with the two photoprocesses occurring simultaneously and competitively on these films with the refractive index, thickness, and mass change differing with the presence of 2BP12. Crosslinking was observed to cause an increase in thickness while photodegradation gave a decrease. Both processes resulted in an increase in the refractive index and mass. While various methods have separately identified these observations, this is the first instance that the in situ chemical, optical, and structural dimensionality of the photodegradation and photocrosslinking phenomena in a thin polymer film is correlated within the same time frame of observation. (c) 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.polymer.2005.05.050

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We report the synthesis and electropolymerization of a precursor polymer with a binary molecular composition of thiophene and carbazole electroactive groups to form ultrathin films of conjugated polymer networks (CPN) on flat indium tin oxide (ITO) substrates. In the past we have demonstrated the precursor polymer approach based on a single pendant electroactive group. In this work, we describe the interesting electrocopolymerization mechanism and properties of precursor polymers prepared with two different types of pendant electroactive groups (statistical copolymer) and compared behavior to their respective homopolymers. The presence of a smaller amount of carbazole induces the electropolymerization of the higher oxidation potential thiophene units via the reaction of a radical cation and a neutral molecule pathway. These electrochemically generated thin films gave unique optical, electrochemical, and morphological properties as a function of composition. The film properties were investigated by cyclic voltammetry (CV), spectroelectrochemistry, EQCM, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS).

DOI： 10.1021/ma050001h

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The resonance shifts (i.e., the resonance angle and the reflectance minimum) in surface plasmon resonance (SPR) curves due to the complex refractive index and/or thickness variations of dielectric films were investigated. For both, nonabsorbing and absorbing dielectrics, the resonance angle shifts linearly with the refractive index and/or thickness variations. The reflectance minimum of the nonabsorbing dielectric does not change as the resonance angle shifts. For an absorbing dielectric, the direction of the reflectance change depends strongly on the magnitude of the absorption and thickness of the metal film. The reflectance minimum of the sensor with a thin metal film decreases before increasing while that of the sensor with a thick metal film continuously increases as the absorption of the dielectric film increases. The phenomena were theoretically explained based on the SPR-gencrated evanescent field at the metal/dielectric interface associated with the optical properties of the sensor architecture. (c) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2004.07.015

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DOI： 10.1021/ja046144l

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Electrochemical doping properties and morphology changes of electropolymerized poly(N-vinylcarbazole) (PVK) thin films were investigated toward improved hole-injection/transport properties in polymer light emitting diode (PLED) devices. The conjugated network polycarbazole thin films (resulting from a poly(N-carbazole) (PCz) network) were prepared by electrodeposition of PVK and/or N-vinylcarbazole comonomer via precursor route and were investigated in situ by electrochemical-surface plasmon resonance spectroscopy (EC-SPS). Distinct doping-dedoping properties and morphology transitions were observed with different compositions of PVK and Cz. By electrochemical doping of the cross-linked conjugated polycarbazole units, the electrochemical equilibrium potential (E-eq), which correlates to Fermi level (E-f) or the work function (phi(w)) of the film, was adjusted in the vicinity of the anode electrode. The conjugated network PCz films were then used as a hole-injection/transport layer in a two layer device. Remarkable enhancement of PLED properties was observed when optimal electrochemical doping was done with the films. Important insight was gained on charge transport phenomena between polymer materials and conducting oxide substrates.

DOI： 10.1021/jp047965f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A new thin-film characterization setup was created based on the combination of a surface plasmon spectrometer with an electrochemical. cell operated under high pressure of up to 200 MPa, and at temperatures up to 120 degreesC. The examples given to document its performance include,photoisomerization studies with poly(methyl methacrylate) (PMMA) films partly derivatized with disperse red (DRI), as well as, a preliminary account of the electropolymerization of EDOT under pressure and the assessment of the redox properties of the resulting thin PEDOT films.

DOI： 10.1002/macp.200400332

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In this study, we demonstrate the synthesis of branched oligothiophene dendrons that act as electroactive surfactants for the capping of CdSe nanocrystals through a ligand exchange process. The number of dendrons per nanocrystal and the nature of surface coordination interactions were studied in detail using UV-vis, FT-IR, AFM, and photoluminescence spectroscopies. These dendron/nanocrystal complexes are very soluble in nonpolar solvents and exhibit photoinduced charge-transfer interactions between the two species. One-layer photovoltaic cells were fabricated that showed initial power conversion efficiencies of 0.29%.

DOI： 10.1021/cm048961q

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Selective area electropolymerization of a precursor polymer in a microcontact printed pattern was used to generate a patterned conjugated and fluorescent polymer thin film. The precursor polyfluorene polymer, which has photoluminescent properties defined by the polymer main chain and electropolymerizability from the pendant carbazole units, was synthesized using a Yamamoto coupling route. The polymer was then electrochemically deposited and cross-linked selectively on the alkyl SAM defined regions to form patterns (<50 nm height) with high fidelity. The patterns were characterized by atomic force microscopy and optical fluorescence microscopy. The fluorescence micrograph confirmed that the polymer main chain was largely unaffected by redox electrochemistry and showed highly regular patterning characteristics in a large area. This new combination of site-selective electropolymerization and the precursor approach should provide a unique way to make patterned conjugated polymer systems.

DOI： 10.1021/cm049544g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PURE APPLIED PHYSICS  

Alternate layer-by-layer (LbL) films were fabricated using two kinds of copper phthalocyanine (CuPc) dyes and the electrical properties due to NO2 gas adsorption were investigated. Water-soluble CuPc dyes, that is, cationic Alcian blue, pyridine variant (AB) and anionic copper phthalocyanine-3,4',4",4'"-tetrasulfonic acid, tetrasodium salt (CuPcTs) were used for the alternate LbL films. Successive depositions of the CuPc alternate LbL films were confirmed using UV-visible absorption and ellipsometry measurements. The average thicknesses of the AB and CuPcTs monolayers were estimated to be 0.7 nm and 0.4 nm, respectively. The fundamental electrical properties were examined for the CuPc alternate LbL films with Au gap electrodes and the properties in the direction parallel to the surfaces of the LbL films were measured. The conduction currents were considered to be dominated by hopping conduction. The response to NO, gas was also measured and the large increase in conduction Currents due to NO, gas adsorption was observed. The magnitude of the conduction current after 30 min exposure to 100 ppm NO2 gas was 10(3)-10(4) times larger than that in N-2 gas.

DOI： 10.1143/JJAP.43.2311

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

The electropolymerization and doping/dedoping properties of polyanifine ultrathin films on Au electrode surfaces were investigated by a combination of in situ electrochemical techniques, i.e., electrochemical surface plasmon spectroscopy (ESPR) and the electrochemical quartz crystal microbalance (EQCM). In the ESPR measurements, we employed two wavelengths, i.e., 632.8 and 1152 nm in order to distinguish independently the electrochromic behavior. In addition, we used spectroelectrochemical transmittance measurements in order to probe further the optical properties of the polymer films as a function of the applied potential. The real and imaginary parts of the dielectric constant of the polyanifine thin film at several doping levels was determined quantitatively by taking into consideration the thickness values obtained from the EQCM measurement. The combination of these two techniques provides a powerful method for probing the electrical, optical, and dielectric properties of conjugated ultrathin polymer films. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jelechem.2003.08.012

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DOI： 10.1080/744819019

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

In this paper, we report on in situ optical/electrochemical investigations using a combination of surface plasmon resonance spectroscopy and electrochemistry in order to determine the complex dielectric constants of poly(3,4-ethylenedioxythiophene) (PEDOT) thin films. The PEDOT films were deposited by in situ electropolymerization. The film thickness was monitored by a quartz crystal microbalance. In the electrochemical surface plasmon resonance (EC-SPR) measurements, three wavelengths corresponding to interband and intraband electronic transition regions were used in order to investigate electrochromic properties. The optical conductivity was also determined by EC-SPR measurement with a near-infrared laser wavelength which corresponds to the region outside the anomalous dispersion.

DOI： 10.1021/la034848n

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The properties of attenuated total reflection (ATR) and emission due to surface plasmon (SP) excitation were investigated for the alternate layer-by-layer ultrathin films self-assembled on Ag thin films using polycation (poly(diallyldimethylammonium chloride), PDADMAC) and azo-dye (Direct Red 80, DR80). The emission light had peaks at the same angles as the resonant angles of the ATR curves and the shapes of the emission spectra also corresponded to those of the ATR curves, and the emission was considered to be mainly due to the SP excitation mediated by the surface roughness of Ag thin films. The structure of the PDADMAC/DR80 layer-by-layer films was found to change due to the photoisomerization of DR80 molecules by the irradiation of polarized visible light, and the surface roughness of the layer-by-layer films was also found to increase by the irradiation and hardly to change after 5-min irradiation. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0040-6090(03)00780-6

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In this paper, we describe, for the first time, the combination of surface plasmon resonance spectroscopy (SPS) and surface plasmon enhanced photoluminescence spectroscopy (SPPL) with electrochemical techniques for the detection of photoluminescence in poly(3,4-ethylenedioxythiophene) (PEDOT) ultrathin films. The EC-SPS/SPPL technique allows for the recording of the weak photoluminescence from an ultrathin PEDOT film in its neutral state. A distinct photoluminescence switching was observed during the potential dependent doping/dedoping process. The EC-SPS/SPPL characterization results are consistent with the observed PEDOT bulk electrochromic properties obtained from UV-vis-NIR spectra. This suggests that the described combination method is capable of electrochemically controlling and optically detecting the very weak photoluminescence of ultrathin films.

DOI： 10.1021/jp0271864

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

An in situ combination of surface plasmon resonance (SPR) spectroscopy and quartz crystal microbalance (QCM) is used to study the electropolymerization and the doping/dedoping behavior of thin poly(pyrrole) (ppy) films in aqueous solutions. A mixed anion and cation exchange behavior is observed. The mass as determined with the QCM continuously increases during redox cycling. The combined QCM/SPR data reveal that this is caused by a relatively slow process occurring when ppy is in the oxidized (polaronic) state. This behavior is interpreted as an accumulation of neutral salt and solvent in the film.

DOI： 10.1021/jp034043o

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A simple approach to fabricate dendritic conducting polymer networks has been developed by means of electropolymerization of pyrrole onto a micropatterned self-assembled monolayer. This polypyrrole network was obtained by a combination of microcontact printing (muCP) of an octadecanethiol self-assembled monolayer (ODT-SAM) pattern on gold and subsequent electropolymerization of pyrrole.

DOI： 10.1002/adma.200304728

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The photoalignment of alternate layer-by-layer (LBL) deposited water-soluble azobenzene dye, direct red 80 (DR80), and polycations have been investigated. The ultrathin films were probed by polarized irradiation, UV-vis spectroscopy, and angle-dependent optical retardation measurements using a hybrid liquid crystal (LC) cell. Dye aggregates within layers were found to reorient anisotropically with polarized irradiated visible light. The selective photoisomerization process primarily enhances the E-isomer, giving high dichroism with the long axes of the azobenzene dye oriented perpendicular to the polarization vector of irradiated light (actinic light). The degree of photoalignment was dependent on the number of adsorbed layers, aggregation behavior, and type of polycation pairs in contrast to spin-coated or Langmuir-Blodgett (LB) films. Atomic force microscopy (AFM) before and after photoisomerization showed lateral expansion of the morphological features consistent with greater anisotropic ordering. These results correlated with the in-plane azimuthal LC photoalignment behavior in hybrid LC cells. Interesting trends were observed, including thickness-dependent photoalignment behavior, different irradiation stabilities, phase shift, and read-write capabilities as photoactive ultrathin films.

DOI： 10.1021/la025842l

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DOI： 10.1021/la025842l

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Preparations of alternate layer-by-layer self-assembled films of poly(diallyldimethyl ammonium chloride) (PDADMAC) and Direct Red 80 (DR80, azobenzene dye) and photo-induced surface relief gratings (SRGs) of the films have been investigated in situ using attenuated total reflection (ATR), that is, surface plasmon resonance spectroscopy (SPS) and quartz crystal microbalance (QCM) measurements. Gratings of the PDADMAC/DR80 films were fabricated by exposure to interference patterns of Ar+ laser light at 488 nm for 30 min. The formation of the gratings was observed using atomic force microscopy (AFM). The films were used for applications to liquid crystal (LC) display devices, and aligning properties of nematic liquid crystal molecules, 5CB, on the SRG in the films were also investigated in a hybrid LC cell configuration by monitoring birefringence properties of the LC cell in situ. It was estimated that the LC molecules in the cell did not align immediately after the photo-induced SRG was inscribed, but almost along the gratings after heat treatment at 40 degreesC for 1 min. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0928-4931(02)00214-X

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

In this study, we use a novel method for simultaneously measuring the optical and electrochemical proper-ties of layer-by-layer self-assembled conducting ultrathin polymer films. We employed the recently developed combination of in situ surface plasmon resonance spectroscopy (SPS) and surface plasmon field-enhanced light scattering (SPFELS) with an electrochemical method (cyclic voltammetry). Polyaniline (PANI) and sulfonated polyaniline (SPANI) were used as the polycation and the polyanion for the conducting layer-by-layer film assemblies. The doping-dedoping process of the PANI/SPANI at different film thicknesses was investigated by electrochemical-SPS/SPFELS. The potential cycling resulted in characteristic oscillations that were sensitively monitored with this technique. We were able to obtain in situ information on dielectric constant changes of the PANI/SPANI layer-by-layer films with respect to film thickness and their corresponding morphology transitions during the electrochemical process. Thus, this experimental approach allows for the simultaneous elucidation of optical and electrochemical properties of conducting polymers in thin film formats.

DOI： 10.1021/la011078b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PURE APPLIED PHYSICS  

Photoinduced in-plane alignments of nematic liquid crystal (LC) molecules, 5CB, have been investigated in a LC cell prepared with alternate self-assembled films of polyelectrolytes and low-molecular-weight azobenzene molecules on gold electrodes using the attenuated total reflection (ATR) measurement method. A high dichroism of the self-assembled film was observed with the irradiation of linearly polarized light. The ATR properties due to excitations of surface plasmon polaritons (SPP) were observed in the LC cell and changed with the irradiation of linearly polarized visible light to the LC cell. The experimental results corresponded well with the calculated shifts at different orientation states of 5CB molecules. It was estimated that the LC molecules have in-plane alignments and that the LC molecules are oriented perpendicular to the polarization direction of the irradiated visible light. The molecular orientations could be controlled by the polarization direction of irradiated light on the hybrid LC cell. In-situ observations for the cell were also carried out during the irradiation. Furthermore, the thickness and dielectric constants of the self-assembled films were evaluated using the ATR method.

DOI： 10.1143/JJAP.41.2753

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DOI： 10.1016/S0927-7757(01)01020-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Photo-induced surface relief gratings of alternate layer-by-layer self-assembled films containing azobenzene dyes were fabricated. The alignment properties of nematic liquid crystal (LC) molecules on these films were investigated in a hybrid LC cell configuration. Poly(diallyldimethylammonium chloride) (PDADMAC) and Direct Red 80 (DR80, azobenzene dye) were deposited using the alternate layer-by-layer self-assembly method. The gratings of the PDADMAC/DR80 films were fabricated by exposure to interference patterns of Ar+ laser light at 488 rim. The formation of the gratings on the films was observed using atomic force microscopy. Furthermore, the alignment properties of LC molecules, 5CB, on the films were investigated by monitoring the change in birefringence of the LC cell in situ, This in-plane alignment was observed after similar to 30 min exposure with the laser, simultaneous with the formation of the interference patterns. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0927-7757(01)01005-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The combination of in situ surface plasmon resonance spectroscopy (SPS) and surface plasmon field-enhanced light scattering (SPLS) with an electrochemical method was used to simultaneously investigate the optical and electrochemical properties of polyaniline films on a planar gold electrode. First, the electropolymerization process of aniline and then the doping-dedoping process of the resulting polyaniline film were investigated using SPS and SPLS. The electropolymerization of aniline was achieved by applying a cycling potential known from cyclic voltammetry. Potential cycling resulted in distinct oscillations sensitively monitored with both techniques. Information was obtained on the change of the dielectric constant of the film and of the film thickness, corresponding to morphology transitions of the polyaniline film. The time-differential SPS kinetic reflectivity curve was correlated with cyclic voltammetry. SPLS was also applied in a reversed attenuated total reflection configuration to obtain more correlation with the electrochemical behavior and optical properties of the polyaniline film, Thus, this combination of experimental approaches allows for the simultaneous elucidation of optical and electrochemical properties of an ultrathin conducting polymer film.

DOI： 10.1021/jp011837z

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DOI： 10.1016/S0927-7757(01)01020-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

A liquid crystal (LC) cell with alternate self-assembled films containing azobenzene dye as aligning layers was fabricated and photo-induced inplane alignments of nematic LC molecules, 5CB, have been investigated in the cell using the attenuated total reflection (ATR) method. The ATR properties due to excitations of surface plasmon polaritons (SPP) were observed in the LC cell and sensitively changed with irradiation of linearly polarized visible light to the LC cell. The experimental results corresponded well with the calculated shifts at different alignment states. It was evaluated that the LC molecules within the penetration length of the SPP (about 130 nm) were aligned perpendicular to the polarized direction of the irradiation light, and that the tilt angle was almost 0 degree.

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The alternate adsorption processes of polyelectrolytes from solution have been investigated in situ using a functionalized (gold electrode) quartz substrate via the quartz crystal microbalance (QCM) technique. The deposition process involved the alternate layer by layer electrostatic (Coulombic) interaction between oppositely charged adsorbing polyelectrolytes resulting in ultrathin multilayer films. Three kinds of polyelectrolyte combinations were used: poly(diallyldimethylammonium chloride) (PDADMAC), poly(ethylenimine) (PEI) and poly(allylamine hydrochloride) (PAH) as the cationic polymers and poly(sodium-4-styrensulfonate) (PSS) as the anionic polymer for polycation/polyanion combinations. The electrical behavior of the piezoelectric 'quartz crystal' was sensitive to the adsorption properties of the polyelectrolytes, thus allowing dose observation of the time-dependent adsorption processes. The adsorption relationship was explored for different polyelectrolyte pair-combinations, alternate solution concentration and the presence of rinsing and drying steps. The results showed that the amount of frequency change is mostly dependent on the immediate subphase environment of the crystal surface, i.e. aqueous environment versus air in relation to the classic Sauerbrey equation. (C) 2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0927-7757(00)00579-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Taylor and Francis Inc.  

Photo-induced in-plane alignments of nematic liquid crystal (LC) molecules, 5CB, have been investigated in the cell with alternate self-assembly films of polyelectrolyte and low-molecular weight dyes on the gold electrodes using the attenuated total reflection (ATR) measurement method. Reflectivities due to the excitations of the surface plasmon polariton (SPP) were observed in the ATR properties of the LC cell. In-plane switching of LC molecules adjacent to the aligning layer was evaluated from the ATR curves by means of irradiation of the linearly polarized visible light to the LC cell. It was also estimated that the re-orientation of the LC molecules occurred within about 130 nm from the surface of the aligning layer on the prism by the irradiation of the polarized light. 2000 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint.

DOI： 10.1080/10587250008024825

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GORDON BREACH SCI PUBL LTD  

In this study, photocurrents enhanced by the surface plasmon polariton (SPP) excitation were observed in a merocyanine (MC) Langmuir-Blodgett (LB) film cell. The excitation of the SPP was carried out by the incidence of a laser beam in the attenuated total reflection (ATR) measurement system. The excitation of the SPF induces the strong absorption of the incident light and large photocurrents in the device.

DOI： 10.1080/10587250008024907

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DOI： 10.1541/ieejfms1990.119.1_124

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Language：Japanese   Publisher：Japanese Liquid Crystal Society  

Photo-induced in-plane alignments of the nematic liquid crystal (LC) molecule, 5CB, have been investigated in the cell with alternate layer-by-layer films of polyelectrolyte and low-molecular weight dyes on the gold electrodes using the attenuated total reflection (ATR) measurement method. Direct red 80 (DR80), azo dye, was employed as an anion; poly(diallyldimethylammonium chloride) (PDADMAC) was used as a polycation. The surface plasmon polaritoh (SPP) was observed in the ATR curves of the LC cells. The properties were sensitively changed by re-orientations of the LC molecules by means of the irradiation of the linearly polarized visible light to the LC cell. In-plane alignments of the LC molecules adjacent to the aligning layer were evaluated by fitting the theoretical ATR curves to the experimental ones.

DOI： 10.11538/ekitou.1999.0_94

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

The tilt angles of liquid crystal molecules, 5CB, have been investigated in liquid crystal cells with rubbing-free aligning layers of polyimide (PI) Langmuir-Blodgett (LB) films on aluminum electrodes using the attenuated total reflection (ATR) measurement method. The surface plasmon polariton (SPP) and/or the guided wave excitation modes (GWEM) were observed in the ATR curves of the liquid crystal cells when various DC voltages were applied to the cell. The ATR properties were evaluated from the SPP and the GWEM. The tilt angles of the liquid crystal molecules were calculated by fitting the theoretical ATR curves to the experimental ones using various models of the liquid crystal layer structure. Furthermore, the electric field intensities in the cell were calculated at several incident angles in the ATR curves. The ATR measurement is very useful for evaluating the alignment properties of liquid crystal molecules in liquid crystal cells.

DOI： 10.1143/JJAP.37.2581

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP  

Tilt angles of liquid crystal molecules, 5CB, have been investigated in the liquid crystal cells with the polyimide (PI) LB alignment films on the aluminum electrodes using the attenuated total reflection (ATR) measurement. The ATR properties were evaluated from the surface plasmon polariton (SPP) and the guided wave excitation modes (GWEM) when various DC voltages were applied to the cell. The tilt angles of the liquid crystal molecules were calculated by fitting the theoretical ATR curves to the experimental ones using a three layers model. Furthermore, the electric field intensities in the cell were calculated at several incident angles.

DOI： 10.1080/10587259808044498

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier  

Tilt angles of nematic liquid crystal molecules, 5CB, have been investigated in cells with rubbing-free aligning layers of polyimide Langmuir-Blodgett (LB) films on the aluminum electrodes using the attenuated total reflection (ATR) measurement. The ATR properties were evaluated from the surface plasmon polariton and the guided wave excitation modes when various DC voltages were applied to the cell. The tilt angles near the aligning layers of the polyimide (Pl) LB films and in the middle layer of the cell were calculated by fitting the theoretical ATR curves to the experimental ones. This technique is very useful for evaluating aligning properties of liquid crystal molecules on LB films in the cells.

DOI： 10.1016/S0040-6090(98)00668-3

Scopus

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：INSTITUTE ELECTRICAL ENGINEERS JAPAN  

Behaviors of liquid crystal molecules, 5CB, have been investigated in the thick cells having aligning layers of the polyimide (PI) Langmuir-Blodgett (LB) films on the aluminum electrodes using the attenuated total reflection (ATR) measurement method. The ATR curves strongly depended upon the AC voltages applied to the cell and upon temperatures. The resonant excitations of the surface plasmon polariton (SPP) were observed in the broad region of the incident angle in the ATR measurements. The tilt angles of the liquid crystal molecules were calculated by fitting the theoretical ATR curves to the experimental ones. The results showed that the ATR measurement method was very useful for evaluating the behaviors of liquid crystal molecules in thick cells.

DOI： 10.1109/ISEIM.1998.741812

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1541/ieejfms1990.117.12_1233

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Multiple plasmonic structures have been a great deal of interest in fabricating electric-field enhanced organic device applications such as biosensors and photovoltaic devices. In this work, we investigated the grating-coupled SPR enhanced organic solar cell fabricated via nanoimprinting technique. The common type organic solar cell with poly(3-hexylthiophene-2,5-diyl) (P3HT) as an electron donor and phenyl-C_<61>-butyric acid methyl ester (PCBM) as an electron accepter was fabricated. The grating pattern was created on top of the active layer, followed by thermal evaporation of Al as a back electrode. Moreover, we studied the enhancement of the photocurrent of organic solar cell with grating pattern, compared to those of without grating structure. This could be artributed to the effect of grating-coupled SPR (GC-SPR) and light scattering ability of Al grating back electrode. The photocurrents were measured with alternative illumination of the p- and s-polarized light. The results show that the grating-coupled SPR of Al back electrode can enhance the photocurrent of the solar cell. Further results will be presented in the conference.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

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