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Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

<title>Abstract</title>The interface of organic semiconductor films is of particular importance with respect to various electrochemical devices such as transistors and solar cells. In this study, we developed a new spectroscopic system, namely electrochemical attenuated total reflectance ultraviolet (EC-ATR-UV) spectroscopy, which can access the interfacial area. Ionic liquid-gated organic field-effect transistors (IL-gated OFETs) were successfully fabricated on the ATR prism. Spectral changes of the organic semiconductor were then investigated in relation to the gate voltage application and IL species, and the magnitude of spectral changes was found to correlate positively with the drain current. Additionally, the Stark shifts of not only the organic semiconductor, but also of the IL on the organic semiconductor films were detected. This new method can be applied to other electrochemical devices such as organic thin film solar cells, in which the interfacial region is crucial to their functioning.

DOI： 10.1038/s42004-021-00525-y

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Other Link： http://www.nature.com/articles/s42004-021-00525-y

Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)  

© 2020, The Author(s). In this study, surface plasmon resonance (SPR) wavelength shifts due to molecular electronic absorptions in the far-ultraviolet (FUV, < 200 nm) and deep-ultraviolet (DUV, < 300 nm) regions were investigated by attenuated total reflectance (ATR) spectroscopy. Due to the strong absorption in the DUV region, N,N-dimethylformamide (DMF) significantly increased the SPR wavelength shift of Al film. On the other hand, no such shift enhancement was observed in the visible region for Au film because DMF does not have absorbance compared to non-absorbing materials such as water and alcohols. The enhanced SPR wavelength shift, caused by the overlap between SPR and molecular resonance wavelengths in FUV-DUV region, is expected to result in high sensitivity for resonant materials.

DOI： 10.1038/s41598-020-66949-z

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

The electronic states ofN-butyl-N-methylpyrrolidinium dicyanamide ([BMP][DCA]), a solvated ionic liquid, around Li(+)were investigated using attenuated total reflectance far-ultraviolet and deep-ultraviolet (ATR-FUV-DUV) spectroscopy. The absorption bands ascribed to the [DCA](-)were blue-shifted as the Li(+)concentration increased, and the origin of the shift was explained by the energetic destabilization of the final (excited) molecular orbital using time-dependent density functional theory (TD-DFT) calculations. Using the multivariate curve resolution-alternating least squares (MCR-ALS) algorithm, the obtained spectra were decomposed into two types of [DCA](-)at electronic state level, which were categorised as pure [BMP][DCA] and [DCA](-)affected by Li+. Our results revealed that the number of [DCA](-)with electronic states affected by a Li+, which was termed the electronic coordination number, was similar to 5. This value was different from the coordination number within the first solvation layer, which was similar to 4. Combining the TD-DFT with molecular dynamics simulations, we demonstrated that one [DCA](-)outside the first solvation layer had a different electronic state from that of pure [BMP][DCA]. This is the first successful study that combines ATR-FUV-DUV spectroscopy with MCR-ALS calculations to build a solvation model that describes the electronic states.

DOI： 10.1039/d0cp03865b

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

DOI： 10.1021/acs.analchem.0c01631

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

Ionic liquids (ILs) with their high dielectric constants (k) are promising dielectrics of organic field-effect transistors (OFETs). However, it is known that interfacial polarizations of dielectrics sometimes cause carrier trappings. In this paper, we investigated the carrier trapping behavior at the interface by using a benchmark system of electric double-layer OFETs (EDL-OFETs) with high device performance and stability: rubrene single crystal as an organic semiconductor showing high hole career mobility and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIM-FSI) as an IL gate dielectric. Apparent bias stress was observed for the system: the operational voltage of the EDL-OFET increased to more than double in similar to 2 h. Operando electrochemical frequency modulation atomic force micros-copy revealed the gradual structuring of the first IL layer facing the carrier-injected rubrene surface. Molecular dynamics (MD) simulations suggested the reorientations of ions in the first IL layer with electrostatic stabilization by forming a patchwork structure. In this stable configuration, negatively charged O and F atoms of the FSI anions pointing to the positively charged rubrene surface come closer, leading to the gradual hole carrier trapping. It was also found that the structured IL layer is deformed and IL-originated bias stress recovers immediately by applying a large OFF-state gate voltage for detrapping the hole carrier.

DOI： 10.1021/acs.jpcc.9b10636

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

This journal is © the Owner Societies. Focusing on the electric double layer formed at aqueous solution/graphite electrode interfaces, we investigated the relationship between the mobility of interfacial water and its hydrogen bonding networks by using molecular dynamics simulations. We focused on the mobility of the first hydration layer constructed nearest to the electrode. The mobility was determined by calculating the diffusion coefficient which showed an opposite trend to that of the applied potential polarity. The mobility decreased upon positive potentials while showing an increase upon negative potentials, which is rationalized by the strength of the interfacial hydrogen bonding networks.

DOI： 10.1039/C9CP06013H

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Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)  

© 2019 Elsevier B.V. Recently, a focus has been placed on plasmonics utilizing ultraviolet light because of its higher energy and shorter wavelength, compared to visible light. Al is a suitable metal for plasmonics in the ultraviolet region. However, Al is easily oxidized, and accurate control for Al film deposition is difficult. In this study, organic thin films were formed on the Al films, and their surface plasmon resonance (SPR) wavelengths were measured by our original attenuated total reflectance spectroscopic system. With an increase in the organic film thickness, the SPR wavelength shifted to longer wavelengths. The minimum detection thickness of the organic overlayer reached 2 nm for three Al films under different conditions (i.e., different Al thickness and oxidation effects), and the spectra were reproduced by simulations based on the Fresnel equations. These results showed the practical advantage of the Al-based SPR sensor without accurate control of the chemical state of the Al film.

DOI： 10.1016/j.sna.2019.111661

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Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

DOI： 10.1021/acs.analchem.8b04931

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

We measured the electronic spectra of graphene nanostructures (flakes and platelets) extending into the far ultraviolet (FUV) region by attenuated total reflection far- and deep-ultraviolet (ATR-FUV-DUV) spectroscopy in the region of 2.76-8.55 eV (450-145 nm). The major absorption of graphene appears in the DUV region (4.7 eV), as already reported; however, we observed a new peak in the FUV region, visible clearly in the case of flakes at 7.5-7.7 eV (165-161 nm) and less pronounced in the spectrum of the platelets at 6.6-6.7 eV (188-185 rim). Graphene flakes (thickness 1-2 nm; sub micrometers of side dimension) and nanoplatelets (thickness 6-8 nm; several micrometers of side dimension) give notably different ATR absorbance spectra in the spectral region studied. This discrepancy is reduced upon applying mechanical pressure on the samples. These observations can evidence that the morphology as well as electronic structure of graphene can be manifested in the FUV DUV region. Quantum chemical calculations were applied to several molecular models incorporating the expected principal structural features of graphene nanostructures. On the basis of the results of time-dependent density functional theory and Zerner's intermediate neglect of differential overlap (ZINDO) calculations, it was possible to consistently reproduce the experimental spectral variations in terms of both band positions and intensities. The spectral differences result from the differences in the die area, ordering and the number of layers, and structural factors which separate nanoflakes and nanoplatelets. These results provide insights into the probable origins of the spectral variability of graphene nanostructures as well as the molecular orbitals involved in a FUV pi-pi* transition of graphene nanostructures.

DOI： 10.1021/acs.jpcc.8b08089

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

Despite providing rich information on electronic states, the far-ultraviolet (FUV, &lt
200 nm) and deep-ultraviolet (DUV, &lt
300 nm) absorption spectra of ionic liquids (ILs) are difficult to obtain without saturation due to very strong analyte absorbance. Herein, FUV-DUV spectra of selected ILs were systematically and easily recorded using an attenuated total reflectance spectrometer and rationalized based on quantum chemical calculations. ILs containing pyrrolidinium or ammonium cations and fluorine-containing anions exhibited weak absorbance below 200 nm that could not be measured by conventional UV-Vis spectroscopy, whereas the corresponding imidazolium-based ILs showed distinct absorption bands that could be reproduced by single-cation-model calculations. On the other hand, imidazolium-based ILs with halide anions showed characteristic charge transfer (CT)-related absorbances. Thus, the above spectroscopic investigations contribute to a fundamental understanding of the electronic processes (e.g., intramolecular excitations and CT transitions) and molecular designs used in electrochemical devices.

DOI： 10.1039/c8an00563j

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier B.V.  

Attenuated total reflectance spectra including the far-ultraviolet (FUV, ≤ 200 nm) region of titanium dioxide (TiO2) with and without gold (Au) nanoparticles were measured. A newly developed external light-irradiation system enabled to observe spectral changes of TiO2 with Au nanoparticles upon light irradiations. Absorption in the FUV region decreased and increased by the irradiation with ultraviolet and visible light, respectively. These spectral changes may reflect photo-induced electron transfer from TiO2 to Au nanoparticles under ultraviolet light and from Au nanoparticles to TiO2 under visible light, respectively.

DOI： 10.1016/j.saa.2017.11.011

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

We investigated the surface (<50 nm) of poly(3-hydroxybutyrate) (PHB) and its nanocomposite with graphene by attenuated total reflection far- and deep-ultraviolet (ATR-FUV-DUV; 145-300 nm; 8.55-4.13 eV) spectroscopy and quantum mechanical calculations. The major absorption of polymers occurs in FUV and is related to Rydberg transitions. ATR-FUV-DUV spectroscopy allows for direct measurements of these transitions in the solid phase. Using ATR-FUV-DUV spectroscopy, periodic density functional theory (DFT) and time-dependent DFT (TD-DFT), we explained the origins of the FUV-DUV absorption of PHB and provided insights into structural changes of PHB which occur upon formation of a graphene nanocomposite and upon heating of the pure polymer. The structural changes cause specific and gradual spectral variations in FUV-DUV. We systematically studied the relaxation of the polymer helix and concluded that the common feature of all models of the unfolded helix lies in a specific and consistent FUV-DUV spectral signature. Relaxed structures feature a blue-shift of the major FUV transition (non-bonding molecular orbital to Rydberg 3p and to *) as compared with crystalline PHB. The FUV absorption of the relaxed structures was determined to be significantly stronger than that of the crystalline state. These results are consistent with the observed temperature-dependent spectra of the pure PHB. The simulation of the thermal expansion of the crystalline polymer by a periodic-DFT study allows us to exclude the possibility that spectral variations observed experimentally are influenced by changes in the crystalline phase. We concluded that the crystallinity of PHB at the sample surface increases with an increase in graphene content in the nanocomposite. However, it is unlikely that the polymer structure inside the crystal is affected; instead the FUV-DUV spectral variations result from changes in the polymer morphology that occur at the sample surface. The phase transition of PHB is affected by temperature and addition of graphene content. These changes are likely to be the opposite of those occurring in the bulk sample.

DOI： 10.1039/c7cp07271f

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Nature Publishing Group  

Surface plasmon resonance (SPR) sensors detect refractive index changes on metal thin films and are frequently used in aqueous solutions as bio-and chemical-sensors. Recently, we proposed new SPR sensors using aluminum (Al) thin films that work in the far-and deep-ultraviolet (FUV-DUV, 120-300 nm) regions and investigated SPR properties by an attenuated total reflectance (ATR) based spectrometer. The FUV-DUV-SPR sensors are expected to have three advantages compared to visible-SPR sensors: higher sensitivity, material selectivity, and surface specificity. However, in this study, it was revealed that the Al thin film on a quartz prism cannot be used as the FUV-DUV-SPR sensor in water solutions. This is because its SPR wavelength shifts to the visible region owing to the presence of water. On the other hand, the SPR wavelength of the Al thin film on the sapphire prism remained in the DUV region even in water. In addition, the SPR wavelength shifted to longer wavelengths with increasing refractive index on the Al thin film. These results mean that the Al thin film on the sapphire prism can be used as the FUV-DUV-SPR sensor in solutions, which may lead to the development of novel and sophisticated SPR sensors.

DOI： 10.1038/s41598-017-06403-9

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Chemical Society of Japan  

Aluminum film thickness dependence of surface plasmon resonance (SPR) in the far- and deep-ultraviolet regions (170300 nm) was revealed using an attenuated total reflectance spectrometer. In the far-ultraviolet region (&lt
200 nm), films of thicknesses 23 and 9 nm showed strong SPR excitations in air and 1,1,1,3,3,3-hexafluoro-2-propanol, which were reproduced by simulations based on the Fresnel equations, respectively. Therefore, Al-SPR sensors are expected to work both in air and in liquids by controlling the film thickness.

DOI： 10.1246/cl.170635

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

Plasmon-induced charge separation (PIGS) at the interface between a plasmonic nanoparticle and semiconductor is now widely used for photovoltaics and photocatalysis. Here we take advantage of PIGS for site-selective nanoetching of silver nanocubes on TiO2 beyond the diffraction limit. A silver nanocube exhibits two resonance modes localized at the top and bottom of the nanocube (distal and proximal modes, respectively) when it is placed on TiO2. We achieved selective etching at the top and the bottom of the nanocubes by PIGS based on the distal and proximal modes, respectively. The site-selective nanophotonic etching reveals that the anodic reaction involved in PIGS is induced by the plasmonic near field, which causes an external photoelectric effect. In particular, the distal mode etching at the top edges is explained in terms of ejection of energetic electrons (or hot electrons) from the distal site to TiO2 across the nanocube.

DOI： 10.1021/acs.jpclett.6b02393

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Optical Society of America  

The surface plasmon resonance (SPR) of Al thin films was investigated by varying the refractive index of the environment near the films in the far-ultraviolet (FUV, 120-200 nm) and deep-ultraviolet (DUV, 200-300 nm) regions. An original FUV-DUV spectrometer that adopts an attenuated total reflectance (ATR) system was used. The measurable wavelength range was down to the 180 nm, and the environment near the Al surface could be controlled. The resultant spectra enabled the dispersion relationship of Al-SPR in the FUV and DUV regions to be obtained. In the presence of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) on the Al film, the angle and wavelength of the SPR became larger and longer, respectively, compared to those in air. These shifts correspond well with the results of simulations performed using Fresnel equations. (C) 2016 Optical Society of America

DOI： 10.1364/OE.24.021886

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

Electronic absorption spectra of imidazolium-based ionic liquids were studied by far- and deep-ultraviolet spectroscopy and quantum chemical calculations. The absorption spectra in the 145-300 nm region of imidazolium-based ionic liquids, [C(n)mim](+)[BF4](-) (n = 2, 4, 8) and [C(4)mim](+)[PF6](-), were recorded using our original attenuated total reflectance (ATR) system spectrometer. The obtained spectra had two definitive peaks at similar to 160 and similar to 210 nm. Depending on the number of carbon atoms in the alkyl side chain, the peak wavelength around 160 nm changed, while that around 210 nm remained at almost the same wavelength. Quantum chemical calculation results based on the time-dependent density functional theory (TD-DFT) also showed the corresponding peak shifts. In contrast, there was almost no significant difference between [C(4)mim](+)[BF4](-) and [C(4)mim](+)[PF6](-), which corresponded with our calculations. Therefore, it can be concluded that the absorption spectra in the 145-300 nm region are mainly determined by the cations when fluorine-containing anions are adopted. In addition, upon addition of organic solvent (acetonitrile) to [C(4)mim](+)[BF4](-), small peak shifts to the longer wavelength were revealed for both peaks at similar to 160 and similar to 210 nm. The peak shift in the deep-ultraviolet region (<= 200 nm) in the presence of the solvent, which indicates the change of electronic states of the ionic liquid, was experimentally observed for the first time by using the ATR spectrometer.

DOI： 10.1039/c6cp02930b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Taylor \& Francis  

Phosphorus (P) is an essential element for all forms of life and is applied as fertilizer in agriculture. The P availability for plants may be highly dependent on the chemical state of P in fertilizers and soils; however, the nature of this dependence remains obscure due to the limitations of generally applied wet chemical and instrumental analytical approaches. This paper focuses on recently developed infrared, Raman, ultraviolet and X-ray microspectroscopic techniques for the characterization of P in soil. Microspectroscopic techniques have the advantage that discrete P phases can be distinguished and characterized even if their mass fractions are very low. However, only small volumes of soil can be analyzed by microspectroscopic methods hence a combination of macro-and microspectroscopic techniques is a promising concept.

DOI： 10.1080/00103624.2016.1228942

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

In application of graphene to real electronics, understanding the mechanism of the electrical breakdown of the graphene in harsh environments should precede many activities in tamed conditions. In this article, we report the unusual structural evolution of microbridge graphene in air near the electrical current-breakdown limit. In-situ micro-Raman study revealed that Joule heating near the electrical breakdown gave rise to a substantial structural evolution: a previously unknown broad amorphous-like and partially reversible phase at an on-and off-current of similar to 3.0 X 10(8) A/cm(2), which finally drove the phase to the electrical current-breakdown. Our calculations suggest that the phase originates from the broken symmetry caused by defect formations during Joule heating. In particular, these formations are bonds of carbon-oxygen and vacancies-oxygen. A collection of energetically favorable vacancies-oxygen pairs results in porous graphene, and its evolution can be the key to understanding how the breakdown starts and propagates in graphene under high current density in air. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.carbon.2015.11.075

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Far- and deep-ultraviolet spectra (150-300nm) of semiconductor nanoparticles (zinc oxide and zinc sulfide) are successfully measured by using attenuated total reflectance (ATR) spectroscopy, and analyzed using finite-difference time-domain (FDTD) simulations. The obtained spectra show good consistency with earlier synchrotron-radiation spectra and with theoretical calculations. The FDTD simulation results show that the present system collected the correct spectra. In the present system, the obtained spectra are affected by the real part n of the complex refractive index more strongly than the imaginary part k. It is also revealed both experimentally and theoretically that spectral intensities of the semiconductor nanoparticles are approximately one tenth those of liquid samples. These results provide insights into the far- and deep-ultraviolet spectroscopy based on the ATR system, and show the general applicability of our original ATR spectroscopy to semiconductor nanoparticles. The system needs neither high vacuum nor much space, and enables rapid and systematic investigation of the electronic states of various materials.

DOI： 10.1002/cphc.201500992

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

Semiconductor materials have been successfully used as surface-enhanced Raman scattering (SERS)-active substrates, providing SERS technology with a high flexibility for application in a diverse range of fields. Here, we employ a dye-sensitized semiconductor system combined with semiconductor-enhanced Raman spectroscopy to detect metal ions, using an approach based on the "turn-off" SERS strategy that takes advantage of the intrinsic capacity of the semiconductor to catalyze the degradation of a Raman probe. Alizarin red S (ARS)-sensitized colloidal TiO2 nanoparticles (NPs) were selected as an example to show how semiconductor-enhanced Raman spectroscopy enables the determination of Cr(VI) in water. Firstly, we explored the SERS mechanism of ARS-TiO2 complexes and found that the strong electronic coupling between ARS and colloidal TiO2 NPs gives rise to the formation of a ligand-to-metal charge transfer (LMCT) transition, providing a new electronic transition pathway for the Raman process. Secondly, colloidal TiO2 nanoparticles were used as active sites to induce the self-degradation of the Raman probe adsorbed on their surfaces in the presence of Cr(VI). Our data demonstrate the potential of ARS-TiO2 complexes as a SERS-active sensing platform for Cr(VI) in an aqueous solution. Remarkably, the method proposed in this contribution is relatively simple, without requiring complex pretreatment and complicated instruments, but provides high sensitivity and excellent selectivity in a high-throughput fashion. Finally, the ARS-TiO2 complexes are successfully applied to the detection of Cr(VI) in environmental samples. Thus, the present work provides a facile method for the detection of Cr(VI) in aqueous solutions and a viable application for semiconductor-enhanced Raman spectroscopy based on the chemical enhancement they contribute.

DOI： 10.1039/c4sc02618g

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

Quantitative analysis of phosphate anions was achieved by measurement of "turn-off" SERS based on the first-layer effect of a chemical mechanism. More importantly, our results demonstrate that it is possible, by means of semiconductor-enhanced Raman scattering, to enhance the SERS sensing performance including stability and reproducibility.

DOI： 10.1039/c5cc02395e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

In this paper, we demonstrate a simple and reliable two-step strategy based on an electrospinning technique combined with in situ calcination for the fabrication of ZnO nanofibers deposited on a silver foil surface. These nanofibers are used as a novel sensitive surface-enhanced Raman scattering (SERS) substrate. The strong interactions between ZnO nanofibers and silver foil afford continuous delocalized surface plasmons, resulting in localization of the electric field at the gap between the ZnO nanofibers and silver foil; thus, the exciton-plasmon interactions between ZnO nanofibers and the silver foil surface contribute to the enhanced scattering, generating a large electromagnetic field enhancement. In addition, the ZnO nanofibers deposited on the silver foil surface exhibit enhanced photocatalytic activity toward the degradation of organic pollutants because of the charge separation effect and increase in the lifetime of the photogenerated excitons under ultraviolet light irradiation; thus, this new substrate can be used as a SERS substrate for determining the catalytic activity and reaction kinetics during the photodegradation of organic pollutants.

DOI： 10.1039/c5ta01974e

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE Publications Sage UK: London, England  

This study has investigated hydrophilicity changes and their inhomogeneity of TiO2 films on Pyrex glasses by near-infrared (NIR) spectral imaging. Near-infrared spectra of TiO2 films in the 9000-4000 cm(-1) region were measured using a newly developed NIR camera named Compovision. A band in the 5400-4800 cm(-1) region, which is assigned to a combination (v(2) + v(3)) mode of bending (v(2)) and antisymmetric stretching (v(3)) modes of the H2O molecule, was clearly identified and its intensity increased with time in the air. It is interesting that the increased rate rose with ultraviolet (UV) light irradiation (300-400 nm, 1 mW cm(-2)) compared to without UV light irradiation. This result suggested that the hydrophilicity of TiO2 was enhanced about twice upon the UV light irradiation. Moreover, the NIR images clarified spatial distributions of the hydrophilicity on the TiO2 surface with a significantly wide area (20 x 40 mm) and a high speed (within 5 s for one image). This rapid imaging system enabled us to detect the hydrophilicity change during only 1 min. The potential of this camera is quite superior, not only for basic research, but also for diverse industrial applications.

DOI： 10.1366/15-07861

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

The tip-enhanced Raman scattering (TERS) spectra of bradykinin (BK) and its potent B-2 BK receptor antagonists, [D-Arg(0), Hyp(3), Thi(5,8), L-Pip(7)] BK and [D-Arg(0), Hyp(3), Thi(5), D-Phe(7), L-Pip(8)] BK, approximately with a size of about 40 nm, adsorbed onto colloidal suspended Ag nanowires with diameter in the range of 350-500 nm and length of 2-50 mu m were recorded. The metal surface plasmon resonance and morphology of the Ag nanowires were studied by ultraviolet-visible (UV-Vis) spectroscopy and scanning electron microscopy (SEM). Briefly, it was shown that two C-terminal amino acids of BK and [D-Arg(0), Hyp(3), Thi(5),8, L-Pip(7)] BK are involved in the interaction with the colloidal suspended Ag nanowire surface, whereas three last amino acids of the [D-Arg(0), Hyp(3,) Thi(5), D-Phe(7), L-Pip(8)] BK sequence attached the Ag surface. Thus, BK adsorbs on the colloidal suspended Ag nanowires mainly through the Phe(5/8) ring (tilted orientation) and the one oxygen atom of the carboxylate group and the H2N-C-NH-CH2- fragment of Arg(9). In the case of [D-Arg(0), Hyp(3), Thi(5,8), L-Pip(7)] BK, the Thi(8) ring (through the lone electron pair on the sulfur atom) and the both oxygen atoms of the carboxylate group and the amine group of Arg(9) mainly participated in the interaction with the Ag nanowire surface. For [D-Arg(0), Hyp(3), Thi(5), D-Phe(7), L-Pip(8)] BK, the D-Phe(7) ring, the Pip(8) ring, and the Arg(9) side-chain assisted in the peptide interaction with the Ag surface. The obtained results emphasize the importance of the C-terminal part of these peptides in the adsorption process onto the colloidal suspended Ag nanowires.

DOI： 10.1039/c5cp03438h

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

The potential of a nanoporous Ag microstructure (np-AgMs) for use as a single particle for surface-enhanced Raman scattering spectroscopy (SERS), with the added advantages of being easy to manipulate and reusable, was successfully demonstrated. The np-AgMs with interconnected pore and controllable pore size were fabricated from symmetric hexapod AgCl via a galvanic replacement reaction in NaCl solution with zinc (Zn) as the sacrificed metal. The clean surface of np-AgMs enables rapid surface functionalization with easy handling and sample preparation as no particle aggregation occurs. The SERS acquisition spots on the np-AgMs can be visually selected using a normal Raman microscope. SERS spectra of p-aminothiophenol (PATP) with a concentration range of 10 (8)-10 (3) M can be achieved. The position-dependent enhancement of np-AgMs was expendably evaluated. The signal-position correlation was confirmed by electric filed enhancement obtained from Finite-difference time-domain (FDTD) calculation. In addition, the highly stable substrate showed insignificant loss of the enhanced Raman signal after several cycles of chemical re-generation. Finally, the potential application of np-AgMs in label-free detection of biomolecules including hemoprotein, protein without chromophore and DNA strains at low concentration of 500 mu g mL(-1) was demonstrated.

DOI： 10.1039/c4ra11890a

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Absorption spectra of anatase and rutile TiO2 modified with various sizes of Au nanospheres (5-60 nm) in the 150-300 nm region were measured by using attenuated total reflection spectroscopy. The smaller Au nanospheres induced larger spectral changes, which mean larger electronic state changes and higher charge-separation efficiency enhancements. In fact, TiO2 with the smaller Au nanospheres showed the higher photocatalytic activities. In contrast, although Au nanorods with various aspect ratios or Au nanocubes were deposited instead of Au nanospheres on TiO2, their spectra (i.e. electronic states) were not significantly changed. Therefore, it was revealed that while there was little shape dependence, the smaller Au nanoparticles induced the larger electronic state change. This may be due to the difference in the potential gradient generated in the interfacial region between TiO2 and the metal, and the smaller Au nanoparticle deposition leads to the higher photocatalytic activities.

DOI： 10.1039/c4ra12503g

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

Surface-enhanced resonance Raman scattering (SERRS) spectra of myoglobin (Mb) with various ligands were measured. In the resonance Raman scattering (RRS) spectra, peaks at around 1610 and 1640 cm(-1) have so far been used to discriminate between the heme iron in a high or low spin state. In the SERRS spectra, however, the spin state cannot be distinguished by the corresponding peaks. Alternatively, the intensity ratio of the SERRS peak at 1560 cm(-1) to that at 1620 cm(-1) was applied to detect the spin states sensitively (1.5 x 10(5) times compared with the RRS): namely, a high ratio was obtained from met-Mb in the high spin state at pH &lt;= 7 except for in a strong acid solution. The different marker bands between the SERRS and RRS spectra may be due to the enhancement order from the surface selection rule.

DOI： 10.1039/c4an01516a

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

Step, ridge, and crack submicro/nanostructures of epitaxial graphene on 4H-SiC (000 (1) over bar) were characterized using tip-enhanced Raman scattering (TERS) spectroscopy. The nanostructures were created during graphene synthesis due to a difference in the thermal expansion coefficient of graphene and SiC. These structures are a distinctive property of epitaxial graphene, together with other desirable properties, such as large graphene sheet and minimal defects. The results of this study illustrate that the exceptional spatial resolution of TERS allows spectroscopic measurements of individual nanostructures, a feat which normal Raman spectroscopy is not capable of. By analyzing TERS spectra, the change of local strain on the nanoridge and decreased graphene content in the submicrometer crack were detected. Using G' band positions in the TERS spectra, the strain difference between the ridge center and flat area was calculated to be 1.6 x 10(3) and 5.8 x 10(4) for uniaxial and biaxial strain, respectively. This confirms the proposed mechanism in previous researches that nanoridges on epitaxial graphene form as a relief against compressive strain. With this study, we demonstrate that TERS is a powerful technique for the characterization of individual local nanostructures on epitaxial graphene.

DOI： 10.1021/jp508730y

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

One or both of two localized surface plasmon modes (full-surface mode and interface mode) of a commercially available single Au nanosphere on TiO2 are excited, and the corresponding spectral changes are induced in the presence of thiocyanate. Similar spectral changes can be simulated by assuming site-selective oxidation of the Au nanosphere by plasmon-induced charge separation (PICS).

DOI： 10.1246/cl.140153

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

Resonance Raman, surface-enhanced resonance Raman scattering (SERBS), and tip-enhanced Raman scattering (TERS) spectra were acquired for deoxymyoglobin (deoxy-Mb) and reduced cytochrome c (reduced Cyt c). Two kinds of Ag nanoparticles (citrate-reduced Ag and thiol-protected) were used for the SERRS measurements. The SERRS spectra could be obtained even when the concentration and laser power were respectively less than a thousandth part and hundredth part of those of the corresponding resonance Raman spectral measurements, demonstrative of the remarkably high sensitivity of SERRS spectroscopy. However, the oxidation of deoxy-Mb (Fe2+) and reduced Cyt c to met-Mb (Fe3+) and oxidized Cyt c, respectively, during the acquisition of the SERRS spectra using citrate-reduced Ag nanoparticles limited the analysis of the proteins in their initial oxidation state. Oxidation was induced by the photocatalytic activity of the citrate reduced Ag nanoparticles upon irradiation with incident laser light. Oxidation was effectively prevented by using thiol-protected Ag nanoparticles for the SERRS measurement or by employing TERS measurements, where the molecules and Ag nanoparticles did not make direct contact, thus preventing the oxidation reactions. The function of heme proteins is strongly related to their oxidation states; thus, it is crucial to obtain Raman spectra in the native oxidation states while circumventing the possibility of photooxidation. From this perspective, SERRS employing thiol-protected Ag nanoparticles and TERS are essential techniques for Raman measurements. In particular, TERS is a developing technique, and this study demonstrates its suitability for acquiring enhanced Raman spectra of heme proteins with nanoscale spatial resolution while preventing photooxidation.

DOI： 10.1021/jp502981e

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Absorption spectra of anatase and rutile TiO2 in the 150-300 nm region before and after the deposition of Pt nanoparticles were measured. For anatase TiO2, the spectral intensity in the longer wavelength region decreased (&gt;similar to 210 nm), while that in the shorter wavelength region increased (&lt;similar to 210 nm). In particular, spectral band intensity in the far-ultraviolet (FUV) region (similar to 160 nm) was increased. In contrast, the spectral intensity of rutile TiO2 increased over the entire wavelength region under investigation. Rutile TiO2 showed a spectral band at a longer wavelength region (similar to 170 nm) than anatase TiO2, and the difference in the band wavelengths in the FUV region was due to the differences in the electronic structures of their phase. The decrease and increase in the intensity upon the Pt nanoparticle deposition suggest electron transfer from the TiO2 to Pt nanoparticles and enhancement of charge-separation, respectively. The photocatalytic activity of rutile TiO2, as evaluated by a photo-degradation reaction of methylene blue, increased more than that of anatase TiO2 upon the deposition of Pt nanoparticles. Thus, we concluded that the charge-separation efficiency of rutile TiO2 is enhanced relative to that of anatase TiO2 upon the deposition of Pt nanoparticles.

DOI： 10.1039/c4cp00329b

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Absorption spectra (150-300 nm) of TiO2 and TiO2 modified with metal (Pt, Pd, and Au) nanoparticles were systematically measured using an attenuated total reflection-far ultraviolet spectrometer. The deposition of metal nanoparticles altered the spectral shape and intensity, indicating changes in the electronic states and photocatalytic activities of TiO2.

DOI： 10.1039/c3cc48446g

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

Thin poly(vinyl chloride) films with size-controlled nanopores (40-150 nm diameter) are prepared by a new and simple method on ITO-coated glass plates and TiO2 substrates by using monodisperse Au nanoparticles. These films are expected to be applied to nanomasks for nanoelectrode ensembles and templates for deposition of size-controlled metal nanoparticles.

DOI： 10.1246/cl.130371

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

The mechanism of plasmon-induced charge separation of gold nanoparticles (Au NPs) on TiO2 was investigated with the help of anionic ligands. Au NPs are oxidized in the presence of KX (X = SCN, Br or Cl), chiefly via direct oxidation to [AuX4](-). The reactivity of Au NPs depends on the solution pH, the type of anion ligands and the excitation wavelength, suggesting that the photopotential of Au NPs during plasmon-induced charge separation depends on both the flatband potential of TiO2 and the energy of irradiated photons. The results indicate that the reactivity and efficiency of the plasmon-induced charge separation and accompanying reactions can be tuned and optimized by changing those factors.

DOI： 10.1039/c3dt51495a

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

Spectral dip formation at arbitrary wavelengths and the corresponding multicolour changes were achieved by using plasmonic Au nanoparticles on TiO2, based on plasmon-induced charge separation and a coordination effect of iodide ions. The dips were stable in air under white light, in marked contrast to the case of conventional Ag nanoparticles.

DOI： 10.1039/c2cc37854j

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

Optical control of size, shape, or orientation of a metal nanoparticle is important for development of nanoscale optical devices and elements of photonic circuits. Thus far, however, independent control of two or more parameters has not yet been achieved. Here we place a simple spherical Ag nanoparticle on TiO2 with high refractive index and separate a plasmon mode localized at the Ag-TiO2 interface from the other mode distributed over the nanoparticle. Selective excitation of each mode gives rise to a corresponding morphological change and selective suppression of the plasmon mode, resulting in multicolor changes of scattering light from orange to red, green, or a dark color.

DOI： 10.1021/nl302919n

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

An electrochemical method for fabrication of metal nanoparticles with controlled size and shape was developed. Ag ions are adsorbed on a conductive substrate, and a voltage is applied between the substrate and a tip of atomic force microscopy in contact mode or tapping mode for deposition of Ag nanoparticles. Although control of particle size is difficult in contact mode because of deterioration in cantilever elasticity, it is possible in tapping mode through regulating the applied voltage or voltage application time. The present method can also be applied to fabrication of Ag nanorods and Ag nanoparticle arrays with controlled size and spacing and deposition of Au nanoparticles.

DOI： 10.1021/jp2123086

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

Changes in morphology and optical properties of single Ag nanoplates on a nanoparticulate TiO2 film were studied, by means of combined atomic force microscopy and optical dark-field microscopy with the aid of discrete dipole approximation-based spectral simulation. Photocatalytic reduction of Ag+ ions under diffusion-controlled conditions grows hexagonal and triangular Ag nanoplates mostly in vertical orientation. The Ag nanoplates absorb and scatter light at different wavelengths on the basis of three different localized surface plasmon resonance modes, the in-plane longitudinal (IPL), in-plane transverse (IPT), and out-of-plane modes. Typical upright nanoplates scatter orthogonally polarized green and near-infrared (NIR) light on the basis of the IPT and IPL modes, respectively. Sufficient irradiation with visible and/or NIR light topples the standing nanoplates over by photo electrochemical reactions, and typical overturned nanoplates scatter NIR light. Such photoelectrochemical behavior is applied to orientation-selective overturn and polarization-selective control of the optical properties by irradiation with polarized visible or NIR light.

DOI： 10.1021/jp109715y

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

Upright Ag nanoplates on a nanoparticulate TiO2 film are oriented on the basis of plasmon-induced charge separation. Polarized visible light removes nanoplates oriented perpendicularly to polarization via excitation of in-plane transverse mode. Polarized near-infrared light removes nanoplates in parallel geometry via excitation of in-plane longitudinal mode.

DOI： 10.1039/c1nr10762c

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

Triangular and hexagonal Ag nanoplates deposited on a TiO2 film in a mostly vertical orientation topple under visible light, resulting in a decrease of extinction at the excitation wavelength and increase at longer wavelengths.

DOI： 10.1039/b904384e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

We present the O-2-blowing method for the growth of high-quality single crystals of Bi-based perovskite ferroelectrics, in which O-2 gas is directly introduced inside crucibles during crystal growth. The O-2-blowing method is demonstrated to be effective for enhancing polarization and piezoelectric properties as well as reducing leakage current for (Bi,Na)TiO3-BaTiO3 crystals. The superior properties are suggested to originate from the reduced reorientation of non-180 degrees domains. Ab initio calculations suggest that the interaction between spontaneous polarization and defect dipole composed of Bi vacancy and O vacancy is the origin of the reorientation of non-180 degrees domains. (c) 2008 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.116.994

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Publisher：Royal Society of Chemistry (RSC)  

The purpose of this review is to demonstrate advances, challenges and perspectives of quantum chemical approaches in molecular spectroscopy of the condensed phase.

DOI： 10.1039/d0cs01602k

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Publisher：Wiley  

DOI： 10.1002/9780470027318.a9279.pub2

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/9780470027318.a9279.pub2

Authorship：Lead author,　Last author,　Corresponding author   Publisher：Elsevier  

DOI： 10.1016/b978-0-12-818870-5.00007-1

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J-GLOBAL

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

Attenuated total reflectance far-ultraviolet (ATR-FUV) spectroscopy can be used to investigate the electronic excitation absorption in various materials. Recently, ATR-FUV studies regarding inorganic semiconductor powders and ionic liquids have been progressing. Newly developed systems enable spectral measurements under conditions where materials exhibit their functionalities. For optical functional materials, such as titanium dioxide, an external light-irradiation system was developed. Upon irradiation with UV and visible light, the spectral intensity in the FUV region was changed. In addition, strong relationships between metal modified titanium dioxide and its photocatalytic activity were revealed. Another developed system that operates under electrochemical conditions was applied to the investigation of ionic liquids. As a result, reversible spectral changes depending on the applied voltage were measured, and the interaction between the iodide anion and the imidazolium cation was revealed. These new ATR-FUV systems can be used for other functional materials that contribute to our understanding and device design of materials.

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Authorship：Lead author,　Corresponding author  

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：AMER CHEMICAL SOC  

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Authorship：Lead author,　Corresponding author  

© 2019 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Plasmonics in the UV region has been widely focused because of the higher energy and the abundant electronic resonances compared to the conventional visible plasmonics. Recently, we have investigated the surface plasmon resonance (SPR) properties of the Al film, aiming for the application as refractive index sensors. Utilizing the UV lights, we expect three advantages: high sensitivity, material selectivity, and surface selectivity. By using an original attenuated total reflectance spectroscopic instrument, Al-SPR angle and wavelength were investigated with changing environments on the Al film. Al film thickness and materials of prisms on which Al was evaporated were also important factors for the SPR properties. By optimizing the conditions, the Al film worked as a sensor both in air and in liquids. In addition, our established system expands the plasmonics into an even higher energy region than 200 nm, while the UV-plasmonics have been studied in the wavelength region longer than 200 nm.

DOI： 10.1002/tcr.201800078

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PubMed

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Language：English   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

Recently, ionic liquids faced on electrodes have been intensively studied because they have been expected as novel electrolytes having high safety and functions. In this study, we constructed an attenuated total reflectance spectroscopic system which worked under electrochemical environments, and investigated electronic states of the ionic liquids near the electrode surface. In accordance with an applied voltage, electronic transition spectra in 150-450 nm range of an ionic liquid consisted of imidazolium cation and iodine anion varied. In particular, absorption due to a charge transfer from the anion to the cation drastically increased at positive potentials. The amount of spectral change and the contact area between the electrode and the ionic liquid were in a positive relationship, and thus, the spectral variations reflected the behavior of the interfacial ionic liquid on the electrode. Time dependence and hysteresis were also discussed. The newly developed system will be applied not only for the ionic liquids but also for various electrochemical materials such as organic semiconductors.

DOI： 10.1117/12.2528346

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This chapter is concerned with recent advances in far-ultraviolet (FUV) spectroscopy of liquids and solids. In the FUV region not only - and n-π but also Rydberg transitions may be observed. Using an attenuated total reflection (ATR)-FUV spectrometer, one can measure FUV spectra of almost all kinds of solid and liquid samples. The most fundamental advantage of FUV spectroscopy is that it contains unique information about the electronic transitions and structure of molecules. In this chapter principle, advantages, and instrument of FUV spectroscopy for studies of condensed matters are described first, and then ATR-FUV studies of electronic structure of organic molecules, polymers, and water are reported. To interpret their spectra quantum chemical calculations were carried out. Finally, FUV spectroscopy of inorganic semiconductor powders is discussed. ATR-FUV spectroscopy has opened a new avenue for σ chemistry.

DOI： 10.1016/B978-0-12-811220-5.00007-1

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© 2018 The Author(s). Surface plasmon resonance (SPR) in the ultraviolet region attracts much attention due to the higher energy and abundant molecular electronic transitions therein compared to those in the visible region. Herein, we investigated the SPR of aluminum (Al) thin films with varying refractive index of the environment near the films in the far-ultraviolet (FUV, = 200 nm) and deep-ultraviolet (DUV, ≤ 300 nm) regions. By using our original FUV-DUV spectrometer which adopts an attenuated total reflectance (ATR) system, the measurable wavelength range was down to the 180 nm, and the environment near the Al surface could be controlled. Based on the obtained spectra, the dispersion relation of Al-SPR in the FUV and DUV regions was obtained. The FUV-DUV-SPR sensors are expected to have three advantages compared to visible-SPR sensors: higher sensitivity, material selectivity, and surface specificity.

DOI： 10.1364/BGPPM.2018.JTu2A.51

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY 26-2 NISHIGOTANDA 1 CHOME SHINAGAWA-KU, TOKYO, 141, JAPAN  

Recently, spectroscopy and photonics in the far-ultraviolet (FUV) region (120 - 200 nm region) have been a matter of great attention because of rapid development of sensitive instruments in this region and an increase in the possible applications. In the present work the state-of-the-art of progress in FUV spectroscopy of the liquids and solids, which are concerned with various valence electronic transitions including sigma, n, and pi electrons, were outlined. FUV spectroscopy is rich in information about the electronic structure and transitions of a molecule, but the absorptivity is very high for liquid and solid states in the FUV region. Thus, spectral measurements for condensed matter in this region were difficult. To overcome this difficulty we introduced an attenuated total reflection (ATR) technique to the FUV region. ATR-FUV spectroscopy has paved a new avenue for condensed-matter FUV spectroscopy. This article demonstrates that FUV holds considerable promise in various fields of research from basic science, such as studies of electronic structure of molecules and those of hydrogen bonding, hydration, and adsorption of water, to material researche, such as polymers, inorganic semiconductors, and ionic liquids.

DOI： 10.2116/bunsekikagaku.66.319

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Language：Japanese   Publisher：The Surface Science Society of Japan  

DOI： 10.14886/sssj2008.36.0_71

CiNii Article

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Language：English  

© 2016 SPIE. Recently, far-ultraviolet (FUV) spectroscopy of solid and liquid states has been a matter of keen interest because it provides new possibilities for studying electronic structures and transitions of almost all kinds of molecules. It has also great potential for a variety of applications from quantitative and qualitative analysis of aqueous solutions to environmental and geographical analyses. This review describes the state-of- the-art of FUV spectroscopy; an introduction to FUV spectroscopy, the development of FUV spectrometers, investigations on electronic transitions and structure, its various applications, and future prospects.

DOI： 10.1117/12.2236269

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Language：English  

© 2016 SPIE. We investigated the surface plasmon resonance (SPR) of aluminum (Al) thin films with varying refractive index of the environment near the films in the fara€'ultraviolet (FUV, ≤ 200 nm) and deepa€'ultraviolet (DUV, ≤ 300 nm) regions. By using our original FUVa€'DUV spectrometer which adopts an attenuated total reflectance (ATR) system, the measurable wavelength range was down to the 180 nm, and the environment near the Al surface could be controlled. In addition, this spectrometer was equipped with a variable incident angle apparatus, which enabled us to measure the FUVa€'DUV reflectance spectra (170-450 nm) with various incident angles ranging from 45° to 85°. Based on the obtained spectra, the dispersion relation of Ala€'SPR in the FUV and DUV regions was obtained. In the presence of various liquids (HFIP, water, alcohols etc.) on the Al film, the angle and wavelength of the SPR became larger and longer, respectively, compared with those in the air (i.e., with no materials on the film). These shifts correspond well with the results of simulations performed according to the Fresnel equations, and can be used in the application of SPR sensors. FUVa€'DUVa€'SPR sensors (in particular, FUVa€'SPR sensors) with tunable incident light wavelength have three experimental advantages compared with conventional visiblea€'SPR sensors, as discussed based on the Fresnel equations, i.e., higher sensitivity, more narrowly limited surface measurement, and better material selectivity.

DOI： 10.1117/12.2236259

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Language：English   Publisher：Royal Society of Chemistry  

Recently, far-ultraviolet (FUV) spectroscopy, which is the spectroscopy of wavelengths in the region 140-200 nm, of solid and liquid states has received significant attention as a novel spectroscopic method. FUV spectroscopy provides new possibilities for studying electronic structures and transitions in almost all types of molecules, from water to polymers. It also shows great promise for a variety of applications. It is well known that wavelengths below 200 nm are rich in information regarding the electronic structure and states of molecules. However, absorptivity is so high in the FUV region, that it has not been employed to investigate solids and liquids. Another problem for FUV region analysis was the instrumentation: FUV spectrometers required vacuum evacuation. Moreover, it was difficult to find applications for FUV spectroscopy. Recently, we introduced the attenuated total reflection (ATR) technique to FUV spectroscopy, which overcomes these issues. ATR-FUV spectroscopy enables the measurement of FUV spectra for solid and liquid samples, establishing a new spectroscopic research area. Using ATR-FUV spectroscopy, electronic transitions that cannot be observed with ordinary UV spectroscopy (200-380 nm) are accessible; Rydberg transitions are just one example. FUV spectroscopy has been demonstrated to have unique and versatile applications. A variety of extensive application studies are now in progress, ranging from applications to fundamental science, such as studies of hydrogen bonding, hydration, and adsorption of water and aqueous solutions, to practical applications such as online, geochemical, environmental, and polymer film analyses. This review provides an introduction to, and brief history of, FUV spectroscopy, and describes the development of new FUV spectrometers, studies on electronic structure and transitions, its various applications, and future prospects.

DOI： 10.1039/c6an00522e

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Authorship：Lead author,　Corresponding author   Language：English   Publisher：Royal Society of Chemistry  

Titanium dioxide (TiO2) is a typical semiconductor metal oxide. It functions under irradiation with ultraviolet (UV, &lt;= 400 nm), deep-ultraviolet (DUV, &lt;= 300 nm), and far-ultraviolet (FUV, &lt;= 200 nm) light. Therefore, investigations in these regions are essentially important not only for the basic understanding of the properties of TiO2 but also for the development of various applications such as photocatalysis and solar cells. In this review, the historic and recent research studies of TiO2 in these areas are overviewed. In particular, recent marked progress on attenuated total reflectance (ATR) DUV-FUV spectroscopy, resonant DUV Rayleigh scattering spectroscopy, and DUV Raman spectroscopy are focused on intensively. These pursuits provide detailed insights into the electronic states, bandgap energies, and phase transformations of TiO2 and TiO2 based materials as well as design guides for their applications.

DOI： 10.1039/c6tc02368a

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Language：English   Publisher：Springer Japan  

The electronic structure and photocatalytic activities of TiO2 and metalnanoparticle-modified TiO2 were investigated by far-ultraviolet and deep-ultraviolet spectroscopy and photodegradation reaction of methylene blue. First, spectra of naked anatase TiO2 (Sect. 6.2) and metal (Au, Pd, Pt)-nanoparticle-modified TiO2 (Sect. 6.3) were measured. The naked TiO2 spectrum corresponded well with the previously reported reflection spectrum and theoretical calculations. Then, the deposition of metal nanoparticles substantially changed the spectral shape, which indicates changes in the electronic states of TiO2, and the degree of spectral changes strongly depends on the work function of the modified metal. In addition, consistent changes of photocatalytic activities were also observed. Next, two crystalline types of TiO2 (anatase and rutile) were compared (Sect. 6.4), and a larger enhancement of the photocatalytic activity of rutile TiO2 upon Pt nanoparticle deposition was revealed. Subsequently, size effects of modified Au nanoparticle on electronic structures and photocatalytic activities of TiO2 were discussed (Sect. 6.5), and it was made clear that the smaller Au nanoparticle induced the larger electronicstate changes and the higher photocatalytic-activity enhancements. These results demonstrated that the novel far-ultraviolet and deep-ultraviolet spectroscopy is a considerable promising method to investigate the electronic states of materials, leading to the development of high-efficiency optical materials such as photocatalysts and solar cells.

DOI： 10.1007/978-4-431-55549-0_6

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Language：English   Publisher：ROYAL SOC CHEMISTRY  

In our SERRS spectra of metmyoglobin by excitation at 514 nm, the peak at 1510 cm(-1), which is assigned to the 6-coordinated heme in the low spin state, was observed by the addition of imidazole and NaN3. Thus, the SERRS likely originates not from the non-native 5-coordinated heme, which is in the high spin state.

DOI： 10.1039/c5an00648a

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Language：Japanese  

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