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

Despite remarkable progress in solvent-assisted processing of hybrid perovskite thin films, the scalable fabrication of their uniform and pin-hole free layers remains a difficult task, especially on flexible substrates. In contrast, we have demonstrated that the polyiodide-assisted conversion of Pb nanolayers into MAPbI(3) results in the formation of crystalline MAPbI(3) thin films on large flexible substrates already at room temperature. The exposure of stoichiometric Pb/MAI bilayers to iodine vapor leads to the formation of highly reactive polyiodide melts MAI(3(L)), which instantly react with the Pb nanolayers converting them into pure MAPbI(3) films without byproducts or unreacted components.

DOI： 10.35848/1347-4065/ac4ad9

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1557/s43580-022-00262-x

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Other Link： https://link.springer.com/article/10.1557/s43580-022-00262-x/fulltext.html

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

DOI： 10.1088/2058-8585/ac489f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：{IOP} Publishing  

We suggested a printable physically unclonable function (PUF) with a simple circuit structure, to provide a low-cost PUF for improvement in the security level of electronic devices. An element of our contact-type printable PUF was constructed of a conductive filler layer and a pair of electrodes formed by printing. The contact-type printable PUF was based on an open- or short-circuit information of elements induced by a percolation conduction phenomenon of the conductive filler layer. An average conduction probability of the elements could be controlled by adjusting the manufacturing conditions, but an actual appearance pattern of the conduction elements became completely random by the influence of the uncontrollable printing variations. We fabricated a thousand elements for each printing condition to evaluate the PUF performance statistically and obtained a random conduction pattern with a conduction probability of 48.3%. Therefore, our contact-type printable PUF had enough potential to be used as a PUF security system.

DOI： 10.35848/1347-4065/ac506b

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DOI： 10.35848/1347-4065/ac51be

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DOI： 10.1002/admt.202100473

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Harvesting of ambient renewable energy resources, such as indoor light, is a viable solution for the development of autonomous, "install-and-forget", environmental nanosensors. In this work we fabricated and characterized photovoltaic cells based on AgBiI4 rudorffites as promising indoor photovoltaic energy harvesters demonstrating photoconversion efficiency of 5.17% and power output of 1.76 μW cm-2 measured under white LED light of 1000 lux. Considering that modern low-power wireless transmitters consume <1 μJ per bit for data transmission, the indoor rudorffite photovoltaic cell combined with a supercapacitor can be used for sensor readout and reliable intermittent data transmission.

DOI： 10.35848/1347-4065/abf2a5

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Publishing type：Research paper (scientific journal)  

Depositing inks on a planar substrate by printing is a facile way to fabricate conductive traces and other complicated functional devices. However, irrespective of the printing methods used, the thickness of the inks has an upper limit due to their fluidic property and subsequent wetting on the substrates. Herein, we present a method for creating high-aspect ratio conductive traces by combining hot-embossing and gravure doctoring techniques. Binary-sized colloidal pastes containing Ag nanoparticles and micrometer-sized spherical Ag powder additives were filled using a doctor blade in the grooves of polycarbonate (PC) films inscribed via hot-embossing to create buried traces. Under optimal mixing conditions in which the minimum resistivity was achieved, voids between the microparticles provided a pathway for the volatile solvents to smoothly escape from the filled ink and minimized thickness reduction during the thermal sintering process. A fabricated trace buried in the PC film with an aspect ratio of around 3:1 and a linewidth of 55 μm showed extremely low resistance of less than 10 Ω/m. A flexible transparent heater was developed using the reported binary colloidal paste.

DOI： 10.1016/j.apt.2021.01.027

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

DOI： 10.1088/1361-6439/ab999c

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Publishing type：Research paper (scientific journal)   Publisher：Japan Institute of Electronics Packaging  

DOI： 10.5104/jiep.23.387

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

DOI： 10.1021/acsomega.9b04222

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DOI： 10.1007/s00339-020-03579-2

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry ({RSC})  

DOI： 10.1039/D0SM00139B

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DOI： 10.7567/1347-4065/ab6462

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI} {AG  

A fiber-optic strain sensor that can show strain via color change and which can be viewed using human eyes has demand in the civil engineering field for alerting purposes. A previous sensor was fabricated using PMMA (Poly(methyl methacrylate)), which had the exceeding hardness to exhibit satisfactory sensor performance. In this research, an elastomer-based fiber-optic structure was fabricated to enhance the elastic response of such sensors and to enlarge the waveguide cross section. Various organic fluorophores were added to the core and cladding regions of the elastic waveguide to induce energy flow from the core to the cladding when stress is applied to the waveguide. Elastomer pairs suitable for the core and cladding were selected from among several candidate materials having high transparency. A method of dispersing fluorophores to each host elastomer and constructing an excellent core-cladding interface using the selected materials was proposed. To investigate the time-dependent changes in the fluorescence of the doped elastomer waveguide, the absorption and emission spectra were monitored after the host elastomers were cured.

DOI： 10.3390/fib7050037

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Language：Japanese   Publisher：The Japan Society of Applied Physics  

DOI： 10.11470/jsapmeeting.2019.1.0_1732

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

© 2019 IOP Publishing Ltd. Printing speed limitation is a critical issue for the high-throughput production in printed electronics. In this study, the formation mechanism of severe rash-type defects in a reverse-offset printing system operating at a high speed is discussed. A systematic investigation showed that the size and density of the defects were significantly influenced by the printing speed, indentation and by the material properties, such as thickness and elasticity of the polydimethylsiloxane (PDMS) sheets. The observation via a high-speed camera of the nip formations between a curved PDMS sheet and a flat glass revealed that, at the very initial stage of contact formation, parts of contacts were concurrently and unstably formed then widened; however, during the later stage, the coalescence of these spots led to the generation of air bubbles trapped in the contact regions, which lasted for several seconds. Based on complementary experiments on the extinction behaviours of the trapped air, we propose a new defect formation model for the rash-like transfer defects observed in the printing tests due to the trapped air regions resulting from the contact instability of PDMS.

DOI： 10.1088/1361-6439/ab024b

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Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press ({CUP})  

DOI： 10.1557/adv.2019.108

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

Copyright © 2019 American Chemical Society. Thin-film layers of nanoparticles exhibit mechanical fragility that depends on their interactions. Balancing the cohesive force of particles with their interfacial adhesion to a substrate enables the selective transfer of micrometer-scale layer features. Here, the versatility of this adhesion-based transfer approach from poly(dimethylsiloxane) (PDMS) is presented by demonstrating micropatterns of various functional nanoparticulate materials, including Ag, Cu, indium tin oxide, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, and dielectric silica. With the attachment of the Johnson-Kendall-Roberts interaction to a simple strain model of particle layers during the patterning process, the patterning criteria for successful printing at both macroscale and nanoscale levels are deduced. Discrete element modeling analysis was used to validate the scaling laws and to highlight the fracture modes of particle layers during the patterning process. In particular, the balance among cohesive forces in the tensile direction and in the shear direction and the adhesion force at the layer-PDMS interface mainly regulates the patterning quality of adhesion patterning.

DOI： 10.1021/acsami.9b13467

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

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Reverse-offset printing (ROP) is a novel printing technique capable of forming electronics-industry-relevant linewidths (≈1 µm) with good thickness control and sharp edge definition. It is demonstrated that through a controlled oxygen-plasma treatment, the energy of the surfaces related to the process steps of ROP can be optimized to allow the patterning of metal-oxide semiconductor layers using a simple printing ink based on metal nitrates dissolved in an organic solvent. The steps of the ROP process are analyzed using surface-energy measurements and Fourier transform infrared spectra of the ink during drying. Thin-film transistors (TFTs) fabricated using a roll-to-plate ROP of In2O3 semiconductor and evaporated Al source/drain (S/D) contacts show, on average, mobilities of 3.1 and 3.5 cm2 V−1 s−1, and ON/OFF-ratios up to 108 and 107 on a Si/SiO2 substrate and on a flexible polyimide-type substrate, respectively. TFTs on the flexible substrate with also the S/D-contacts printed with ROP using Ag nanoparticle ink exhibit a 1.4 cm2 V−1 s−1 mobility. To demonstrate the scalability of the process, continuous lines of In2O3 are printed using a roll-to-roll-compatible (R2R) ROP with linewidths down to ≈2 µm. This process is expected to lead to miniaturized metal-oxide circuits as required by flexible high-resolution sensor arrays and displays.

DOI： 10.1002/aelm.201900272

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Effects of exposure to ultraviolet (UV) photons and thermal treatments on solution-processed amorphous indium gallium zinc oxide (a-IGZO) films were investigated by X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopy. As a result, oxygen vacancies obviously become more abundant in the films sintered at 250 or 300 °C by the exposure to 7.21 eV photons and less abundant by the subsequent thermal treatment at 250 °C in air. The drain current also clearly becomes smaller in a thin film transistor fabricated using the IGZO film in a manner opposite to the abundance of oxygen vacancies. That is, the drain current becomes smaller by the UV irradiation and returns to the original high value by the subsequent thermal treatment. This indicates that oxygen vacancies act as trapping centers or scattering centers of electrons. In addition, the reversible change of the drain current with the cycle of UV irradiation and the thermal treatment opens the possibility of the use of the IGZO films as a UV sensor.

DOI： 10.1063/1.5049618

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Language：Japanese   Publisher：The Japan Society of Applied Physics  

DOI： 10.11470/jsapmeeting.2018.2.0_1867

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© 2018 American Chemical Society. The submicrometer resolution printing of various metal acetylacetonate complex inks including Fe, V, Mn, Co, Ni, Zn, Zr, Mo, and In was enabled by a robust ink formulation scheme which adopted a ternary solvent system where solubility, surface wettability, and drying as well as absorption behavior on a polydimethylsiloxane sheet were optimized. Hydrogen plasma in heated conditions resulted in bombarded, resistive, or conductive state depending on the temperature and the metal species. With a conductivity-bestowed layer of MoOx and a plasma-protecting layer of ZrOx situated on the top of an IGZO layer, a solution-processed TFT exhibiting an average mobility of 0.17 cm2/(V s) is demonstrated.

DOI： 10.1021/acsami.8b07465

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Language：Japanese   Publisher：The Japan Society of Applied Physics  

DOI： 10.11470/jsapmeeting.2018.1.0_1973

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Language：Japanese   Publisher：The Japan Society of Applied Physics  

DOI： 10.11470/jsapmeeting.2018.1.0_4051

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© 2018 The Chemical Society of Japan. We have fabricated hybrids of two-dimensional silica colloidal crystals and gold nanospheres for the development of platforms showing effective SERS phenomenon with a high spatial reproducibility. The SERS signal of 4-mercaptobenzoic acid immobilized on the hybrids was enhanced up to 10.4 times by optimizing the silica diameter, as compared with that on the gold nanospheres immobilized on a planar glass plate. We propose that the effective enhancement is induced by hot spots generated at the junction regions between the silica nanospheres.

DOI： 10.1246/cl.171185

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Language：Japanese   Publisher：The Japan Society of Applied Physics  

DOI： 10.11470/jsapmeeting.2017.2.0_3856

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Language：Japanese   Publisher：The Japan Society of Applied Physics  

DOI： 10.11470/jsapmeeting.2017.2.0_3857

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© 2017 American Chemical Society. We describe efficient visible- and near-infrared (vis/NIR) light-driven photocatalytic properties of hybrids of Cu2O and plasmonic Cu arrays. The Cu2O/Cu arrays were prepared simply by allowing a Cu half-shell array to stand in an oxygen atmosphere for 3 h, which was prepared by depositing Cu on two-dimensional colloidal crystals with a diameter of 543 or 224 nm. The localized surface plasmon resonances (LSPRs) of the arrays were strongly excited at 866 and 626 nm, respectively, at which the imaginary part of the dielectric function of Cu is small. The rate of photodegradation of methyl orange was 27 and 84 times faster, respectively, than that with a Cu2O/nonplasmonic Cu plate. The photocatalytic activity was demonstrated to be dominated by Cu LSPR excitation. These results showed that the inexpensive Cu2O/Cu arrays can be excellent vis/NIR-light-driven photocatalysts based on the efficient excitation of Cu LSPR.

DOI： 10.1021/acs.langmuir.7b01052

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

Electroless plated metals have been used for wiring and electrodes in the manufacture of electronic devices. To obtain plated patterns, etching and photoresist are generally used. However, through catalyst patterning by printing, we can obtain metal patterns without etching and photoresists by electroless plating. Solution-processed indium-gallium-zinc oxide (IGZO) has received significant attention for showing high performance and ease of preparation in air atmosphere. In this study, we prepared an electroless plated pattern by catalyst printing as electrodes of IGZO TFT. There are few reports on the application of plated metal electrodes prepared by catalyst printing to the source and drain electrodes of IGZO TFT. The prepared IGZO TFT exhibits a typical current-voltage (I-V) curve. The plated electrodes caused many problems such as performance degradation. However, our result showed that the plated metal electrodes can drive IGZO TFT. In addition, we confirm plated metal growth into the catalyst layer by cross sectional scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS) of the plated Ni. We discuss the relevance of the measured work function (WF) of the electrode materials and the performance of IGZO TFT.

DOI： 10.7567/JJAP.56.05EB07

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Other Link： http://orcid.org/0000-0002-7343-9722

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

In this work, we evaluated the feasibility of a paper-based bacterial detection system. The paper served as a substrate for the measurement electrodes and the culture medium. Using a printing technique, we patterned gold electrodes onto the paper substrate and applied Luria broth (LB) agar gel as a culture medium on top of the electrodes. As the first step towards the development of a bacterial detection system, we determined changes in the surface potential during bacterial growth and monitored these changes over 24 h. This allowed us to correlate changes in the surface potential with the different growth phases of the bacteria. (C) 2017 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.56.05EC04

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Other Link： http://orcid.org/0000-0002-7343-9722

Language：Japanese   Publisher：The Japan Society of Applied Physics  

DOI： 10.11470/jsapmeeting.2017.1.0_3995

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Language：Japanese   Publisher：The Japan Society of Applied Physics  

DOI： 10.11470/jsapmeeting.2017.1.0_1849

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Language：Japanese   Publisher：The Japan Society of Applied Physics  

DOI： 10.11470/jsapmeeting.2017.1.0_3996

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

We demonstrated the usefulness of Cu light harvesting plasmonic nanoantennae for the development of inexpensive and efficient artificial organic photoelectric conversion systems. The systems consisted of the stacked structures of layers of porphyrin as a dye molecule, oxidation suppressing layers, and plasmonic Cu arrayed electrodes. To accurately evaluate the effect of Cu nanoantenna on the porphyrin photocurrent, the production of Cu2O by the spontaneous oxidation of the electrode surfaces, which can act as a photoexcited species under visible light irradiation, was effectively suppressed by inserting the ultrathin linking layers consisting of 16-mercaptohexadecanoic acid, titanium oxide, and poly(vinyl alcohol) between the electrode surface and porphyrin molecules. The reflection spectra in an aqueous environment of the arrayed electrodes, which were prepared by thermally depositing Cu on two-dimensional colloidal crystals of silica with diameters of 160, 260, and 330 nm, showed clear reflection dips at 596, 703, and 762 nm, respectively, which are attributed to the excitation of localized surface plasmon resonance (LSPR). While the first dip lies within the wavelengths where the imaginary part of the Cu dielectric function is moderately large, the latter two dips lie within a region of a quite small imaginary part. Consequently, the LSPR excited at the red region provided a particularly large enhancement of porphyrin photocurrent at the Q-band (ca. 59-fold), compared to that on a Cu planar electrode. These results strongly suggest that the plasmonic Cu nanoantennae contribute to the substantial improvement of photoelectric conversion efficiency at the wavelengths, where the imaginary part of the dielectric function is small.

DOI： 10.1021/acsami.6b13147

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Other Link： http://orcid.org/0000-0002-7343-9722

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

We demonstrate the detection of an increase in refractive index and/or thickness by specific adsorption of proteins on a plasmonic surface on a paper substrate in the Otto configuration. Propagating surface plasmon resonance is observed on a gold surface deposited onto polymer-coated papers through angular scans of reflectivity in the Otto configuration under attenuated total reflection conditions. According to a surface analysis with atomic force microscope, the gold surface roughness on a polyvinyl chloride (PVC)-coated paper is comparable to that of a Si wafer, leading to the achievement of protein detection. On the other hand, the propagating length of the surface plasmons is shorter than that on the Si wafer. According to an observation of the gold surface with scanning electron microscope, the gold grain size on the PVC-coated paper is smaller than that on the Si wafer. Thus, many boundaries cause a reduction in the propagating length on the PVC-coated paper.

DOI： 10.1557/adv.2017.378

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Other Link： http://orcid.org/0000-0002-7343-9722

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Physics Publishing  

Wedesigned an aqueous-fluoroalcoholic InGaZnO precursor for obtaining thin-film transistors (TFTs) on a flexible plastic film by spin-coating and low-temperature annealing processes without inert gas conditions. The precursor shows a low surface tension (23.7mNm-1), which is advantageous for homogeneous coating onto plastic film. Thermal analysis of the precursor indicates formation of metal oxides at less than 300 °C. InGaZnO TFTs were obtained from the precursor by annealing at 300 °CviaUVirradiation under humid atmosphere on a transparent polyimide film as well as on a p-Si substrate. The bottom-gate top-contact TFTs on the p-Si show 5.1 cm2 V-1 s-1 of the average saturation mobility. The top-gate top-contact TFTs on the transparent polyimide film drive with 0.99 cm2 V-1 s-1 of the average saturation mobility. The transparent polyimide film maintains flexibility even after humid-UV irradiation and annealing processes. The InGaZnO TFTs on the transparent polyimide film show more than 80% transmittance in the visible light region between 400 and 780 nm.

DOI： 10.1088/2058-8585/1/4/045001

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Language：Japanese   Publisher：The Japan Society of Applied Physics  

DOI： 10.11470/jsapmeeting.2016.2.0_3624

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Silver nanocolloid, a dense suspension of ligand-encapsulated silver nanoparticles, is an important material for printing-based device production technologies. However, printed conductive patterns of sufficiently high quality and resolution for industrial products have not yet been achieved, as the use of conventional printing techniques is severely limiting. Here we report a printing technique to manufacture ultrafine conductive patterns utilizing the exclusive chemisorption phenomenon of weakly encapsulated silver nanoparticles on a photoactivated surface. The process includes masked irradiation of vacuum ultraviolet light on an amorphous perfluorinated polymer layer to photoactivate the surface with pendant carboxylate groups, and subsequent coating of alkylamine-encapsulated silver nanocolloids, which causes amine-carboxylate conversion to trigger the spontaneous formation of a self-fused solid silver layer. The technique can produce silver patterns of submicron fineness adhered strongly to substrates, thus enabling manufacture of flexible transparent conductive sheets. This printing technique could replace conventional vacuum- and photolithography-based device processing.

DOI： 10.1038/ncomms11402

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

We investigated hybrid organic-inorganic complementary inverters with a solution-processed indium-gallium-zinc-oxide (IGZO) n-channel thin-film transistor (TFT) and p-channel TFTs using the high-uniformity polymer poly[2,5-bis(alkyl)pyrrolo[3,4-c]pyrrolo-1,4(2H,5H)-dione-alt-5,5-di(thiophene-2-yl)-2,2-(E)-2-(2-(thiophen-2-yl) vinyl) thiophene] (PDVT-10). The IGZO TFT was fabricated at 150 degrees C for 1 min. It showed a high field-effect mobility of 0.9cm(2).V-1.s(-1) and a high on/off current ratio of 10(7). A hybrid complementary inverter was fabricated by combining IGZO with a PDVT-10 thin-film transistor and its operation was confirmed. (C) 2016 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.55.04EL04

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Other Link： http://orcid.org/0000-0002-7343-9722

Language：Japanese   Publisher：The Japan Society of Applied Physics  

DOI： 10.11470/jsapmeeting.2016.1.0_4010

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Language：Japanese   Publisher：The Japan Society of Applied Physics  

DOI： 10.11470/jsapmeeting.2016.1.0_4011

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

We fabricated solution-processed indium-gallium-zinc oxide (IGZO) thin-film transistors (TFTs) by microwave (MW) annealing an IGZO precursor film followed by irradiating with vacuum ultraviolet (VUV) light. MW annealing allows more rapid heating of the precursor film than conventional annealing processes using a hot plate or electric oven and promotes the crystallization of IGZO. VUV irradiation was used to reduce the duration and temperature of the post-annealing step. Consequently, the IGZO TFTs fabricated through MW annealing for 5 min and VUV irradiation for 1 min exhibited an on/off current ratio of 108 and a field-effect mobility of 0.3 cm(2) V-1 s(-1). These results indicate that MW annealing and photoirradiation is an effective combination for annealing solution processed IGZO precursor films to prepare the semiconductor layers of TFTs. (C) 2015 Author(s).

DOI： 10.1063/1.4922512

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

We developed a contact inking technique for microcontact printing aiming at the fabrication of conductive silver-nanoparticle (Ag NP) lines with rectangular cross section and constant layer thickness, irrespective of pattern size and shape. In the proposed process, Ag NP ink was first coated on a blanket and then inking was carried out by a contact with a microcontact stamp. The ink transferred onto the top of the stamp was finally settled on a workpiece by pressing to complete the printing process. To achieve robust inking to the stamp, the peel strengths between the Ag NP layer and the blankets and between the Ag NP layer and the stamp were investigated using poly (dimethylsiloxane) (PDMS) materials with different surface energies. Interestingly, it was revealed that the transferability of Ag-NP from the blanket toward the stamp was not solely determined by the surface energy difference but also by the extent of solvent uptake by the PDMS blanket during inking. The solvent-containing PDMS significantly lowered its adhesion strength against adjacent ink layers and, as a consequence, the ink transfer was successfully achieved even if the ink passed from a higher to a lower energy surface. Furthermore, by the solvent-vapour annealing of contact-inked semi-dried patterns, arbitrarily iterated transfers between PDMS surfaces became possible. With the contact-inking process developed here, we demonstrate a finely defined printed structure of Ag NP conductive lines with widths of up to 1 mu m.

DOI： 10.1088/0960-1317/25/5/055022

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Other Link： http://orcid.org/0000-0002-7343-9722

Language：Japanese   Publisher：The Japan Society of Applied Physics  

DOI： 10.11470/jsapmeeting.2015.1.0_3809

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TECHNICAL ASSOC PHOTOPOLYMERS,JAPAN  

DOI： 10.2494/photopolymer.28.353

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Other Link： http://orcid.org/0000-0002-7343-9722

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

We have achieved a drastic improvement of the performance as thin film transistor (TFT) for solution-processed IGZO thin film by controlling drying temperature of solvents containing the precursor solution. The IGZO-precursor solution was prepared by mixing of metal nitrates and two kinds of organic solvents, 2-methoxyethanol (2ME) and 2,2,2-trifluoroethanol (TFE). 2ME was used for dissolving metal nitrates. TFE was added as a solvent for reducing surface tension as small as possible, leading to improvement of the wettability of the precursor solution on the surface of the substrate. In order to discuss the relationship between morphology and drying process, the spin-coated IGZO-precursor films were dried at room temperature and 140 °C on a hotplate, respectively. Annealing of the both films was carried out at 300 °C in an electric oven for 60 min after each drying process. Drying at room temperature provides a discontinuous film, resulting in a large variation of the TFT performance. On the other hand, drying at 140 °C provides a continuous film, resulting in the higher TFT performance and a minor variation. The difference in surface morphologies would be derived from the evaporation rate of the organic solvents. The rapid evaporation at 140 °C brings about rapid pinning of the spin-coated precursor layer on the substrate. Preparation process via the drying at 140 °C gave ~ 1 cm&lt
sup&gt
2&lt
/sup&gt
V&lt
sup&gt
-1&lt
/sup&gt
s&lt
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-1&lt
/sup&gt
of the saturated mobility, quite small hysteresis, and 10&lt
sup&gt
7&lt
/sup&gt
~ 10&lt
sup&gt
8&lt
/sup&gt
of the on-off ratio.

DOI： 10.1557/opl.2015.267

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

We succeeded in controlling the wavelength range in which the photocurrent of porphyrin is enhanced by tuning as well as expanding the wavelength ranges in which the localized surface plasmon resonance (LSPR) occurs. We fabricated photoelectric conversion systems consisting of 5,10,15,20-tetrakis(p-carboxyphenyl) porphyrin (TCPP) and silver nanoprisms with small (SAgPRs) and large (LAgPRs) aspect ratios as plasmonic nano-antennae. Their photocurrents were much larger than those from TCPP-modified Ag planar electrodes at the specific wavelengths corresponding to their LSPR bands (SAgPRs: 460-610 nm; LAgPRs: 610-690 nm). The maximum enhancement factors (EFs) for the SAgPRs and the LAgPRs were 37 and 35, respectively. In order to enhance the photocurrents, we expanded the LSPR bands by the combined use of SAgPRs and LAgPRs. The system consisting of the mixture (MAgPRs) showed enhancement of the photocurrent over the entire Q-band region (480-690 nm). Finally, the total EFs of the photocurrents were evaluated by irradiation with AM1.5G sunlight through a long-pass filter of 480 nm and the results revealed that the EFs were in the order of MAgPRs &gt; SAgPRs &gt; LAgPRs. Furthermore, the system showed stability without loss of the enhancement property for at least 10 min under the solar irradiation.

DOI： 10.1039/c5tc02606g

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

Printed low-voltage programmable (&lt
6 V) write-once-read-many (WORM) memories can be utilized in low-bit count and low-complexity printed electronic systems powered by printed batteries. Such WORM memories can be operated as anti-fuses based on electrical sintering of Ag nanoparticles or as fuses based on breaking of a printed Ag conductor of sub-μm2 cross-sectional area. In this paper, we present initial results on fuse-type WORM memories fabricated with reverse offset printing that can allow narrow line width (∼3 μm) with low variation in the cross-sectional area of the bits.

DOI： 10.1109/ESTC.2014.6962777

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Other Link： http://orcid.org/0000-0002-7343-9722

Language：Japanese   Publisher：The Japan Society of Applied Physics  

DOI： 10.11470/jsapmeeting.2014.2.0_4019

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

We demonstrate a new approach to plasmonic enhanced photocatalytic water splitting by developing a novel core-shell Ti@TiO2 brush nanostructure where an elongated Ti nanorod forms a plasmonic core that concentrates light inside of a nanotubular anodic TiO2 shell. Following the ubiquitous element approach aimed at providing an enhanced device functionality without the usage of noble or rare earth elements, we utilized only inexpensive Ti to create a complex Ti@TiO2 nanostructure with an enhanced UV and Vis photocatalytic activity that emerges from the interplay between the surface plasmon resonance in the Ti core, Vis light absorption in the Tirich oxide layer at the Ti/TiO2 interface and UV light absorption in the nanotubular TiO2 shell.

DOI： 10.1088/0957-4484/25/31/315402

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We fabricated a thin-film transistor (TFT) using amorphous indium gallium zinc oxide (a-IGZO), which was formed through annealing of an IGZO precursor film with a single-mode cavity microwave at 2.45GHz. The transisitor fabricated with the a-IGZO film prepared by microwave annealing for 15 min showed higher device performance, i.e., a field effect mobility of 5.75 x 10(-2)cm(2).V-1.s(-1), an on/off ratio of 10(6), and a threshold voltage of 20 V, than that prepared by annealing with a conventional oven for 120 min. The Raman spectra confirm that the device improvement originates from the decrease in the number of -OH groups and removal of organic species for 15 min by microwave annealing. These results suggest that the microwave annealing method has an advantage as the annealing process of solution-processed oxide semiconductors to reduce the process time. It can be applied to the fabrication of TFTs. (C) 2014 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.53.05HA12

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

Indium-gallium-zinc oxide (IGZO) nanoparticles that can act as an oxide semiconductor were successfully synthesized using a coprecipitation method via the hydrolysis of urea in aqueous media containing ethylene glycol. The resulting IGZO precursor nanoparticles contain crystalline indium hydroxide and zinc-gallium carbonate. Sintering the precursor nanoparticles at temperatures higher than 300 degrees C provides amorphous IGZO nanoparticles, while poly-crystalline IGZO nanoparticles are obtained at temperatures above 700 degrees C. Poly-crystalline IGZO ink was prepared using the IGZO nanoparticles for the fabrication of a thin film transistor (TFT). Annealing at temperatures higher than 400 degrees C for 30 min gives the desired TFT switching properties due to the removal of the organic fraction contained in the ink.

DOI： 10.1039/c3tc31944j

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TECHNICAL ASSOC PHOTOPOLYMERS,JAPAN  

DOI： 10.2494/photopolymer.27.339

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Surface plasmon excitation provides stronger enhancement of the fluorescence intensity and better sensitivity than other sensing approaches but requires optimal positioning of a prism to ensure optimum output of the incident light. Here we describe a simple, highly sensitive optical sensing system combining surface plasmon excitation and fluorescence to address this limitation. V-shaped fluidic channels are employed to mimic the functions of a prism, sensing plate, and flow channel in a single setup. Superior performance is demonstrated for different biomolecular recognition reactions on a self-assembled monolayer, and the sensitivity reaches 100 fM for biotin-streptavidin interactions. Using an antibody as a probe, we demonstrate the detection of intact influenza viruses at 0.2HA units ml(-1) levels. The convenient sensing system developed here has the advantages of being prism-free and requiring less sample (1-2 mu l), making this platform suitable for use in situations requiring low sample volumes.

DOI： 10.1038/ncomms3855

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Ordered arrays of copper nanostructures were fabricated and modified with porphyrin molecules in order to evaluate fluorescence enhancement due to the localized surface plasmon resonance. The nanostructures were prepared by thermally depositing copper on the upper hemispheres of two-dimensional silica colloidal crystals. The wavelength at which the surface plasmon resonance of the nanostructures was generated was tuned to a longer wavelength than the interband transition region of copper (&gt
590 nm) by controlling the diameter of the underlying silica particles. Immobilization of porphyrin monolayers onto the nanostructures was achieved via self-assembly of 16-mercaptohexadecanoic acid, which also suppressed the oxidation of the copper surface. The maximum fluorescence enhancement of porphyrin by a factor of 89.2 was achieved as compared with that on a planar Cu plate (CuP) due to the generation of the surface plasmon resonance. Furthermore, it was found that while the fluorescence from the porphyrin was quenched within the interband transition region, it was efficiently enhanced at longer wavelengths. It was demonstrated that the enhancement induced by the proximity of the fluorophore to the nanostructures was enough to overcome the highly efficient quenching effects of the metal. From these results, it is speculated that the surface plasmon resonance of copper has tremendous potential for practical use as high functional plasmonic sensor and devices. © 2013 American Chemical Society.

DOI： 10.1021/nn403925d

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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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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：Japanese   Publisher：公益社団法人 応用物理学会  

DOI： 10.11470/jsapmeeting.2013.2.0_4462

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Recently, spontaneously formed microwrinkles on hard coating-capped elastomer surfaces have attracted the attention of both the scientific and applied research communities, because of their simple fabrication process and potential for diverse practical applications. The depth and averaged orientation of the microwrinkle grooves can be controlled by applying strain. Here, we study the diffusion of light passed through a surface with wrinkles in the range of hundreds of microns. Without strain, the sample shows no wrinkles and is a transparent plate. With strain, the surface shows wrinkles and diffuses the light beam depending on the magnitude of applied strain. Thus, the present system can be used as a switchable optical diffuser. ©2013, The Society of Polymer Science, Japan.

DOI： 10.1295/koron.70.179

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

The optical diffusion of transmitted or reflected light via a deformable wrinkled surface with a periodicity in the range of hundreds of micrometers is studied. Without strain, the sample shows no wrinkles and no optical diffusion. With uniaxial strain, the surface shows aligned wrinkles and anisotropically diffuses incident light in a manner that depends on the degree of applied strain. The relationship between the sinusoidal microstructure and the diffused state is successfully explained in the context of geometric optics. The present system can be used as a mechanically tunable optical diffuser.

DOI： 10.1002/adom.201300128

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

We have developed a fluorescence enhancement system for biomolecular detection using a monolithic waveguide sensing plate. The plate consists of a thermally grown amorphous SiO2 layer, a Si single-crystal layer, and bulk amorphous SiO2. Waveguide-mode excitation in this plate produces an enhanced electric field on the plate surface, and therefore, signals from analyte-labeling fluorescent dyes are enhanced. In the present paper, we elucidate the impact of the system from viewpoints of the electric field enhancement factor calculated numerically and the analysis of the limit of detection estimated from experimental results. Optimal layer thicknesses of the plates to achieve the highest sensitivity are also discussed. Further, an interesting phenomenon that accompanied the waveguide-mode excitation, namely, photoluminescence from the amorphous SiO2 layer itself, is also reported. (C) 2013 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4800826]

DOI： 10.1063/1.4800826

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

We synthesized viscous precursors to indium gallium zinc oxide (IGZO) using three kinds of alcoholamines, ethanolamine (EA), diethanolamine (DEA), and triethanolamine (TEA), by a simple process. The viscous precursors are obtained just by vigorous stirring of alcoholamine and urea in an aqueous solution containing the metal nitrates during heating at 150-160°C. The precursor containing EA (EA-precursor) is a pale-orange suspension containing aggregates of the metal hydroxides and shows pseudoplastic flow. The precursors containing DEA (DEA-precursor) and TEA (TEA-precursor) are transparent pale-yellow and dark-orange sols, respectively. They give Newtonian flow in the lower shear rate and pseudoplastic flow in the higher shear rate. Higher concentration of metal salts leads to higher viscosity of the precursors. According to thermogravimetry-differential thermal analysis (TG-DTA) for the EA- and DEA-precursors, evaporation of alcoholamine occurs at around each boiling point and subsequently formation of metal oxides occur at around 300°C. In the case of the TEA-precursor, formation of metal oxides occurs before pyrolysis of TEA attributed to the higher boiling point of TEA. The thin IGZO film, which is prepared by spin-coating of the diluted DEA-precursor and subsequent sintering at 450°C for 30 min, shows 0.02 cm2·V-1s -1 of the mobility and 10-5 of the on/off ratio. The highly viscous DEA-precursor containing high concentration of metal ions allows patterning in an area of 100 cm2 onto a surface of a silicon wafer with screen printing. © 2013 Materials Research Society.

DOI： 10.1557/opl.2013.783

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

In this study, we analyzed adsorption and binding behaviors of citrate-capped silver nanoparticles (AgNPs) on a pyridyl-terminated surface using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Adsorption of the AgNPs onto the pyridyl-terminated silicon wafer surface was completed through pH-controlled sol immersion. The adsorption occurred predominantly at a pH less than the pK(b) value of the pyridyl group and more than the pK(a1) of citric acid, indicating that the driving force behind adsorption was electrostatic interaction. Adsorption of citrate onto the pyridyl group also occurred at pK(al) &lt; pH &lt; pK(b) without AgNPs. According to XPS in the N1s region, larger deprotonation from the pyridinium-formed pyridyl groups was demonstrated subsequent to adsorption of the AgNPs. The deprotonation from the pyridinium indicates the formation of the neutral pyridyl group as the counterpart of hydrogen bonding with the carboxyl group of citrate. The binding state between the pyridyl group and citrate surrounding AgNPs is expected to be kept stable through hydrogen bonding and van der Waals force derived from the AgNPs approach to the pyridyl surface.

DOI： 10.1021/la2032785

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The ability to control metal patterns at the micro- and nanoscales, along with the development of a simple fabrication method, is important to many applications in the fields of materials science, biological sensing, electronics, and photonics. Herein, a simple approach to fabricating gold micropatterns with controlled roughness is reported. In this approach, gold is evaporated onto a striped liquid micropattern formed on self-organized microwrinkles. Gold nanoribbons with higher roughness form on the liquid part of the substrate because the deposited gold atoms can diffuse, grow, and aggregate at the liquid-air interface, whereas flat gold films form on the solid part. The rough gold nanoribbons formed on the liquid can then be peeled off through contact with water. The extinction spectrum of the rough gold nanoribbons suggests characteristic surface-plasmon absorption. This shows the possibility of using rough gold nanoribbons with controlled shape in plasmonic technology.

DOI： 10.1002/smll.201002072

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

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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In order to utilize silver nanoparticles for various applications such as photocatalysts while maintaining their chemical stability, enhanced electric fields on the nanoparticle surfaces induced by localized surface plasmon excitation must be used effectively. For satisfying these requirements, an ultrathin silica coating with a thickness of only a few nm was formed around silver nanoparticles by a chemical reaction in a solution, while parameters such as the amount of sodium silicate and the number of dialysis procedures performed were changed. As a result, it was found that a key factor for obtaining stable thin-silica-coated silver nanoparticles is the conductivity of the solution. Using a solution with an appropriate conductivity above 2.7 mS/m, silica films can be coated on silver nanoparticles without causing deterioration of the plasmonic activity resulting from the aggregation of silver. (C) 2009 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.48.06FE04

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We fabricated a boronic acid-surface on a flat silica surface for optical detection of recognition of catechol structure. The boronic acid-surface was obatained by chemical reaction between 4-carboxyphenylboronic acid (CPB) and the primary amine group of 3-aminopropyltriethoxysilane (APS) modified onto the silica surface. The UV-vis spectroscopic and the X-ray photoelectron spectroscopic (XPS) measurements indicated that 90% of the primary amines of APS reacted with CPB. Recognition of the catechol structure on the CPB surface was observed with in-situ time dependent measurement using optical configuration of surface plasmon spectroscopy. Injection of phosphate buffers containing 1.0 mM dopamine (DA) and catechol, respectively, at pH 7.0 allowed increase of the reflectivity, suggesting complexation between DA or catechol and the boronic acid of CPB. On the other hand, increasing of the reflectivity (δR) in the case of tyramine, which is very similar in chemical structure to DA but has no catechol structure, was quite small. The ratio of (δR) between DA and tyramine (DA/tyramine) was experimentally estimated to be 5.5, which briefly shows that the CPB-modified surface can recognize catechol structure. The (δR) behaviors of DA differed from the pH of buffers. At pH 8.1, polymerization of DA was observed on the CPB-modified surface while no recognition at pH 6.0. The efficient pH for the 1:1 complexation between DA and boronic acid of the CPB-modified surface is thought to be around 7.0. © 2009 The Surface Science Society of Japan.

DOI： 10.1380/ejssnt.2009.571

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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 present a genuine experimental technique to fabricate silver nanoparticles with all ultrathin silica coating, thus making the nanoparticles chemically inert. The impact of the coating on plasmonic properties is experimentally quantified and compared with theoretical predictions. Furthermore, numerical simulations of the near-field enhancing properties of the nanoparticles are conducted. It is found that the coatings fabricated are sufficiently thin to make the plasmonic resonance wavelength shift negligible and for observing a significant field enhancement on the surface of the silica shell at the resonance wavelength. Application of such inert nanoparticles to sensitize the absorption of near-ultraviolet light is discussed.

DOI： 10.1143/JJAP.47.8641

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We achieved fabrication of the benzylamine-terminated surface onto a glass substrate for detection of catecholamines by fluorogenic derivatization. Fabrication was carried out in turn as follows, (1) immobilization of 3-aminopropyltriethoxysilane (APS) onto the glass surface, (2) modification of 1,4-phenylenediisothiocyanate (PDC) onto the amino-terminated surface, and (3) modification of p-xylylenediamine (XDA) onto the isothiocyanate-terminated surface. The sequent surface reactions were monitored by UV-vis spectroscopy, contact angle measurement, X-ray photoelectron spectroscopy (XPS), and surface plasmon spectroscopy. Fluorogenic derivatization of adrenaline was performed by exposure of the benzylamine-terminated surface to borate buffer containing adrenaline and potassium hexacyanoferrate (III) as an oxidant. Fluorescent spectra indicated existence of a fluorophore on the benzylamine-terminated surface after treatment with adrenaline.

DOI： 10.1166/sl.2008.413

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An evanescent-field-coupled waveguide-mode sensor with a multilayer structure consisting of a dielectric waveguide, a thin reflecting layer, and a glass substrate illuminated under the Kretschmann configuration operates as a sensor that is capable of detecting modifications in the dielectric environment near the waveguide surface with superior sensitivity by measuring the change in reflectivity. The sensitivity of the sensor is strongly dependent on the optical constants of the reflecting layer. Numerical simulations show that a sensor having a reflecting layer with a small value of the real part of the complex refractive index shows a good sensitivity for both S- and P-polarized light. Materials with values of the real and imaginary parts of the complex refractive index of &gt; 4 and similar to 0.5, respectively, are suitable for use as reflecting layers when S- polarized light excites only the lowest order waveguide mode. The simulations were experimentally confirmed using sensors with Au, Cu, Cr, W, a-Si, or Ge reflecting layers deposited by radiofrequency magnetron sputtering by observation of specific adsorption of streptavidin on biotinyl groups using an S-polarized laser beam with a wavelength of 632.8 nm. From the results, guidelines are given for the fabrication of preferred sensor configurations.

DOI： 10.1088/0957-4484/19/9/095503

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Sensors based on surface plasmons or waveguide modes are at the focus of interest for applications in biological or environmental chemistry. Waveguide-mode spectra of 1 mu m-thick pure and perforated silica films comprising isolated nanometric holes with great aspect ratio were measured before and after adhesion of streptavidin at concentrations of 500 nM. The shift of the angular position for guided modes was nine times higher in perforated films than in bulk films. Capturing of streptavidin in the nanoholes is at the origin of that largely enhanced shift in the angular position as the amplitude of the guided mode in the waveguide perfectly overlaps with the perturbation caused by the molecules. Hence, the device allows for strongly confined modes and their strong perturbation to enable ultra-sensitive sensor applications. (c) 2007 Optical Society of America.

DOI： 10.1364/OE.15.002592

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

We synthesized novel imidazole-based azo compounds and their optical properties were investigated. In the course of recrystallization, pink-orange and violet products were obtained. The violet one shows poor solubility for most organic solvents except polar aprotic solvents such as dimethylsulfoxide (DMSO) and dimethylfolmamide (DMF). The spectra of NMR in DMSO-d(6) and UV-vis absorption spectra in DMSO for both products were found to be identical. However, there were differences in FT-IR absorption spectra. The violet solid compound exhibited broad bands that could be attributed to N-(HN)-N-... hydrogen bonding. These results show that the violet product consists of an aggregation of molecules formed via intermolecular hydrogen bonding. Additionally, imidazole-based azo copolymers containing liquid crystalline side chain groups were also synthesized. The photoinduced birefringence of these copolymers was observed by irradiation of a linearly polarized 532 mn laser beam as a pumping light. It was confirmed that the material exhibited photoisomerization properties and the observed birefringence was attributed to photoinduced molecular reorientation. Moreover, the dipolar effect in photoinduced birefringence was briefly discussed.

DOI： 10.1143/JJAP.45.460

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

Photonic crystal is a frontier material to control photons. Among many photonic crystals, the inverse opal structure, which is formed by using a mold of self-assembled particles, became popular because of its easy fabrication and easy chemical modification. In this paper, the TiO2 inverse opal structure was modified to a dye-sensitized photoelectrode. The inverse opal structure was designed to inhibit the emission of the dye. As a result, the incident monochromatic photon-to-electron conversion efficiency per one molar dye of the dye-sensitized inverse opal electrode becomes larger than the one of a normal dye-sensitized electrode. (c) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.colsurfa.2004.10.032

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This work presents high sensitive detection of specific adsorption of proteins onto a silicon oxide (SiOx) surface modified by molecules with a biotinyl-end group. We fabricated a SiOx waveguide by sputtering onto a thin gold film and measured the incident angle-dependence of reflectivity using a polarized He-Ne laser under total internal reflection condition. When the s-polarized light was irradiated to the SiOx waveguide (760 nm) coupled with a prism, the incident angle-dependence of reflectivity showed narrow dips due to excitation of the waveguide mode. The waveguide surface was modified by the molecules with the biotinyl-end group as a protein probe. Specific adsorption of streptavidin in a PBS buffer solution was monitored through time course of the reflectivity change at a constant incident angle, where the waveguide mode was excited. As compared with conventional SPR system using a gold surface, high sensitive detection of the specific adsorption was achieved. Additionally, we fabricated micro-patterned arrays of biotinyl-end layers onto the SiOx waveguide surface by micro-contact printing (μCP). Then we observed the specific adsorption behavior on the micro-patterned arrays by the imaging based on the waveguide mode using a CCD camera. © 2006 Materials Research Society.

DOI： 10.1557/proc-0900-o12-39

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

We fabricated periodic structures of CdS using honeycomb films consisting of an amphiphilic copolymer as a template. The honeycomb film using an amphiphilic copolymer was fabricated on the water surface under highly humid condition and was then transferred onto a solid substrate. The pore size in the honeycomb film was ca. 5 mu m. The CdS nanoparticles were synthesized using a gelatin as an inhibitor of rapid nuclear growth and then the gelatin was removed by decomposition using an enzyme. The CdS particles were introduced into pores of the honeycomb film by casting, dipping, and electrochemical deposition. Dipping the honeycomb film into CdS suspension under ultrasonication, periodic deposition of CdS particles in the honeycomb holes was achieved. The CdS-honeycomb film composite was calcinated at 450 degrees C for 30 min in order to remove organic moiety. After calcination, periodic arrangement of porous CdS dots with diameter of 3-5 mu m was partially formed. The CdS dots are applicable to photoelectrochemical and optical devices such as a photodiode.

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DOI： 10.1142/9789812796714_0033

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This paper describes effective photocurrent generation based on a polymer Langmuir-Blodgett (LB) monolayer containing ruthenium complex on a silver electrode excited by surface plasmon resonance (SPR). It was found that photocurrent generation is greatly enhanced at an incident angle where the electromagnetic field was most enhanced by SPR. At this angle, the photocurrent is enhanced by a factor of 23.6 compared with that at the critical angle for total internal reflection. The incident monochromatic photon-to-current conversion efficiency was 9.53 x 10(-3)%, higher than that of the corresponding polymer LB monolayer film on a transparent indium tin oxide electrode with conventional direct transmitted light (2.87 x 10(-3)%). Furthermore, it was demonstrated that precoating with poly(N-dodecylacrylamide) homopolymer ensures adequate separation of the Ru(bpY)(3)(2+) and silver surface, thereby suppressing the quenching of photoexcited Ru(bpy)(3)(2+) by the silver. Controlling the distance between the Ru(bpy)(3)(2+) layer and the silver using the Langmuir-Blodgett technique leads to effective photoexcitation of Ru(bpy)(3)(2+) by SPR and suppression of quenching by the silver surface, resulting in efficient photocurrent generation.

DOI： 10.1021/jp014552v

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We fabricated periodic structures of CdS using honeycomb films consisting of an amphiphilic copolymer as a template. The honeycomb film using an amphiphilic copolymer was fabricated on the water surface under highly humid condition and was then transferred onto a solid substrate. The pore size in the honeycomb film was ca. 5 mu m. The CdS nanoparticles were synthesized using a gelatin as an inhibitor of rapid nuclear growth and then the gelatin was removed by decomposition using an enzyme. The CdS particles were introduced into pores of the honeycomb film by casting, dipping, and electrochemical deposition. Dipping the honeycomb film into CdS suspension under ultrasonication, periodic deposition of CdS particles in the honeycomb holes was achieved. The CdS-honeycomb film composite was calcinated at 450 degrees C for 30 min in order to remove organic moiety. After calcination, periodic arrangement of porous CdS dots with diameter of 3-5 mu m was partially formed. The CdS dots are applicable to photoelectrochemical and optical devices such as a photodiode.

DOI： 10.1142/s0219581x02000656

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

Recently a method that utilizes the condensation of micrometer-sized water droplets on evaporating solutions of polymers has been reported for the preparation of porous thin films with fine hexagonal periodicity, honeycomb films. Here we report a method for imprinting a honeycomb pattern on the PDMS (poly(dimethyl siloxane)) elastomer. For the preparation of the honeycomb film, a benzene solution of amphiphilic copolymer was cast at high atmospheric humidity. On the film the PDMS precursor was poured and cured. The cured PDMS with the honeycomb film was peeled from the slide glass. The PDMS was rinsed with the solvent to remove the honeycomb film. The exposed PDMS surface was observed using SEM and AFM. The pattern-imprinted PDMS surface can be used as a template for patterning of materials, which are difficult to produce a honeycomb pattern by the conventional method described above. Here, we show some examples of such honeycomb-originated structures composed of polymers or nanoparticles, which were fabricated using the pattern-imprinted PDMS. The present study shows an example of the secondary uses of the self-organized structures for the cost-saving micro/nanofabrication of various materials.

DOI： 10.1142/s0219581x02000681

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

An anodic photocurrent due to photoinduced electron transfer between excited Ru(bpy)(3)(2+) and triethanolamine was remarkably enhanced by light irradiation using the surface plasmon resonance on a silver electrode which was modified by amphiphilic copolymer Langmuir-Blodgett monolayer containing Ru(bpy)(3)(2+) compared with irradiation of transmitted light.

DOI： 10.1246/cl.2001.378

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

Sulfonated polyaniline (SPAn) was employed to incorporate photocatalytic molecules directly into a polyaniline (PAn) matrix. Photoinduced electron transfer between SPAn and the tris(2,2'-bipyridyl)ruthenium complex (Ru(bpy)(3)(2+)) was studied for a Ru(bpy)(3)(2+)-incorporated SPAn film in solutions containing viologens. The change in the spectrum of the film was observed by the illumination to the electrochemically reduced film under open circuit conditions in an aqueous solution at pH 2.5 containing methylviologen (MV2+). This is due to a photoelectrochromism; caused by the photooxidation of SPAn by the photoexcited Ru(bpy)(4)(2+). The film was hydrolyzed in the aqueous solution once the potential was swept above + 1.2 V. Ru(bpy)(3)(2+) molecules were revealed to accelerate the hydrolysis of the SPAn backbone. Although the illumination to the electrochemically reduced film under open circuit did not seem to induce the hydrolysis under the present conditions, the fully oxidized film was photohydrolyzed by the illumination, leading to a decrease in the absorption corresponding to SPAn at the illuminated part. The photoelectrochromism and photohydrolysis of the film were discussed from a viewpoint of negative and positive image formation, respectively. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-0728(00)00414-9

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

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J-GLOBAL

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J-GLOBAL

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