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

Graphene is widely recognized as an outstanding and multi-functional material in various application fields such as electronics, photonics, mechanics, and life sciences. We propose a neurotransmitter sensor with ultra-small volume for detecting the photonic light-matter response. Such detection can be achieved using surface-activated monolayer graphene sheets and CMOS-compatible silicon-photonic circuits. Patterned pieces of CVD-grown graphene are integrated on the top of a silicon micro-ring resonator, which induce the adsorption of catecholamine molecules originated from the pi-stacking effect. We used dopamine to demonstrate such detection and examine the sensitivity of graphene-dopamine coupling. To avoid high optical insertion loss and degradation of resonance characteristics caused by a graphene's extremely high optical absorption coefficient in the near infrared region, a ring resonator with adjusted coupling design is used to compensate for the drawbacks. Owing to the advanced nano-sensing platform and measurement system, an activated graphene-sensing surface of only similar to 30 mu m(2)/ch enables pi coupling to dopamine with enough sensitivity to detect less than 10-mu M solution concentration. The detection mechanism through the surface reaction is also verified by optical simulation and atomic force microscopy measurement, revealing that the flowing dopamine molecules can only occupy the outermost surface of graphene. We expect this sensor to contribute to the development of an innovative label-free and disposable bio-sensing platform with accurate, sensitive, and fast response. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

DOI： 10.1364/OE.27.032058

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DOI： 10.1021/acsami.9b05552

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

Neuronal constructs with tuneable 3D geometry can contribute greatly to the construction of brain-like functional tissues for transplantable grafts and robust experimental models. In this study, we propose a self-folding graphene/polymer bilayer film that forms a micro-roll for neuron encapsulation, and highlight the importance of employing pores on the micro-roll to allow neurons to interact with their surroundings. The micro-patterns and varied thicknesses of the bilayer provide control over the 3D geometries of the micro-roll. The pores facilitate the diffusion of reagents, resulting in the adequate loading of probes for imaging and the successful stimulation of the encapsulated neurons. Moreover, the encapsulated neurons inside the micro-roll are functionally integrated into surrounding neuronal networks by extending their axons through the pores. Thus, our method for encapsulating neurons with a porous graphene-laden film allows the construction of precisely shaped neuronal tissues that interact with their surroundings. We believe that the method will open a new avenue for the reconstruction of functional neuronal tissues and is potentially applicable to other self-folding bilayers.

DOI： 10.1039/c9nr04165f

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Language：English   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

DOI： 10.2116/analsci.highlights1902

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

Three-dimensional (3D) graphene architectures are of great interest as applications in flexible electronics and biointerfaces. In this study, we demonstrate the facile formation of predetermined 3D polymeric microstructures simply by transferring monolayer graphene. The graphene adheres to the surface of polymeric films via noncovalent pi-pi stacking bonding and induces a sloped internal strain, leading to the self-rolling of 3D microscale architectures. Micro patterns and varied thicknesses of the 2D films prior to the self-rolling allows for control over the resulting 3D geometries. The strain then present on the hexagonal unit cell of the graphene produces a nonlinear electrical conductivity across the device. The driving force behind the self-folding process arises from the reconfiguration of the molecules within the crystalline materials. We believe that this effective and versatile way of realizing a 3D graphene structure is potentially applicable to alternative 2D layered materials as well as other flexible polymeric templates.

DOI： 10.1021/acs.nanolett.8b04279

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MYU, SCIENTIFIC PUBLISHING DIVISION  

We describe an originally developed fabrication process of introducing an adhesive layer that fixes a graphene layer on a substrate via p-p interactions. The adhesive layer is prepared with an easy and highly reproductive wet chemical reaction that modifies the surface of the substrate before transferring the graphene layer. By using the process, we can greatly reduce the damage of the graphene layer that occurs during the manufacturing of a graphene microelectrode (GME). The process enables us to produce almost damage-free GMEs in high yield. The durability of a GME during an electrochemical measurement was also improved and the GME can be used stably even after repeating the electrochemical measurement, rinsing with water, and air drying.

DOI： 10.18494/SAM.2019.2237

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

Sodium chloride (NaCl) aqueous solution becomes NaCl hydrate, NaCl center dot 2H(2)O, at low temperature, which is different from potassium chloride and is a typical complex model for studying the freeze-drying process in foods and pharmaceuticals. Here, we detected unit-cell-sized NaCl particles in ice as precursor substances of NaCl center dot H2O during freezing of NaCl solution by using terahertz (THz) spectroscopy. In the freezing process, Na+ and Cl- ions form two types of metastable unit-cell-sized NaCl particles on the pathway to the well-known NaCl center dot H2O crystal production, which are not listed in the phase diagram of freezing of NaCl solution but have absorption peaks in THz spectra. This finding of single unit-cell-sized particles signifies the importance of studying the freeze-drying process in-depth and offers a new possibility for the development of freeze-drying technology for the manufacture of nanometer-sized particles such as ultrafine pharmaceutical powders, which more readily dissolve in water.

DOI： 10.1021/jacs.8b07828

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

The relaxation time and mobility of electrons on graphene are deduced quantitatively by complex permittivity analysis with microwave dielectric loss spectroscopy. Hexagonal graphene sheets with uniform domain sizes from 6 to 30 mu m, which target the mean free path of electrons on graphene based on the significantly longer turnover time of microwave probing at gigahertz (GHz) frequencies as compared to the relaxation time of electrons, are employed to determine the factors for carrier relaxation at the intradomain and grain boundaries. The changes in the complex permittivity by carrier injections clearly show an evidence of plasma carriers in graphene. This result validates the plasma carrier model with the restoring force in the GHz regime instead of the free carrier model, which is applied to analyze the optical conductivity over the terahertz (THz) regime. Based on Dirac massless fermions in graphene, the relaxation time of electrons is estimated to be 250-450 fs from the changes in complex permittivity, which are experimentally determined by frequency-dependent microwave conductivity measurements. The obtained relaxation time shows a positive correlation with the domain size of graphene, implying that the scattering dominantly occurs at the domain boundary.

DOI： 10.1002/adom.201701402

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MYU, SCIENTIFIC PUBLISHING DIVISION  

We have successfully created a graphene microroll aptasensor (GMA) through the self-folding of bilayer thin films. The inner surface of the GMA consists of a functionalized graphene surface, which works as a fluorescence aptamer-based biosensor. This is achieved by combining previously reported two-dimensional (2D) graphene aptasensor technology, a novel self-folding process for flexible, multilayered polymeric films. The aptasensing portion is composed of a graphene surface, which is functionalized with a pyrene-aptamer-dye probe. The three components of the probe work as linkers to the graphene surface, a protein recognition part, and a fluorescence detection tag, respectively. In this paper, we discuss the specialized fabrication process required to produce the GMA. By confirming the diffusion of target molecules through the hollow space of the GMA, we also show the ability of this device to detect concentration changes in real time.

DOI： 10.18494/SAM.2018.2069

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

Multi-layered thin films with heterogeneous mechanical properties can be spontaneously transformed to realise various three-dimensional (3D) geometries. Here, we describe micro-patterned all-polymer films called micro-rolls that we use for encapsulating, manipulating, and observing adherent cells in vitro. The micro-rolls are formed of twin-layered films consisting of two polymers with different levels of mechanical stiffness; therefore they can be fabricated by using the strain engineering and a self-folding rolling process. By controlling the strain of the films geometrically, we can achieve 3D tubular architectures with controllable diameters. Integration with a batch release of sacrificial hydrogel layers provides a high yield and the biocompatibility of the micro-rolls with any length in the release process without cytotoxicity. Thus, the multiple cells can be wrapped in individual micro-rolls and artificially reconstructed into hollow or fibre-shaped cellular 3D constructs that possess the intrinsic morphologies and functions of living tissues. This system can potentially provide 3D bio-interfaces such as those needed for reconstruction and assembly of functional tissues and implantable tissue grafts.

DOI： 10.1038/s41598-017-17403-0

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

We report on a self-propelled gel using ionic liquid as a new type of self-propellant that generates a powerful and durable motion at an air-water interface. The gel is composed of 1-ethyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) and poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)). A long rectangular ion gel piece placed on the interface shows rapid rotation motion with maximum frequency close to 10 Hz, corresponding to the velocity over 300 mms(-1) at an outmost end of the piece. The rotation continues for ca. 10(2) s, followed by a reciprocating motion (<similar to 10(3) s) and a nonlinear motion in long-time observations (>similar to 10(3) s). The behaviours can be explained by the model considering elution of EMIM-TFSI to the air-water interface, rapid dissolution into water, and slow diffusion in an inhomogeneous polymer gel network. Because the self-propellants are promptly removed from the interface by dissolution, durable self-propelled motions are observed also at limited interface areas close in size to the gel pieces. A variety of motions are induced in such systems where the degree of freedom in motion is limited. As the ion gel possesses formability and processability, it is also advantageous for practical applications. We demonstrate that the gel does work as an engine.

DOI： 10.1038/s41598-017-09351-6

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

The Raman spectroscopy of pharmaceutical cocrystals based on caffeine and oxalic acid in nanosized pores of mesoporous silica has been demonstrated at various molar amounts. The Raman peak shifts of caffeine molecules express the existence of pharmaceutical cocrystals in mesoporous silica. The molar amount dependence of the peak shifts describes that caffeine and oxalic acid cocrystallized on the surface of the nanosized pores and piled up layer by layer. This is the first report that shows the Raman spectroscopy is a powerful tool to observe the synthesis of pharmaceutical cocrystals incorporated in the nanosized pores of mesoporous silica. The results indicate a way to control the size of cocrystals on a nanometer scale, which will provide higher bioavailability of pharmaceuticals.

DOI： 10.2116/analsci.33.47

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

We report on a new protein sensor built on pristine graphene. Graphene grown by chemical vapor deposition and supported on a SiO2 surface was modified with a sequence consisting of pyrene, DNA aptamer, and dye. Here, an aptamer is a nucleic acid having a specific base sequence that recognizes and forms a complex with a target molecule such as a protein. In our protein sensing system, the recognition of a target protein triggers the fluorescence of a dye tethered on the graphene surface. This is based on the effective fluorescence quenching property of graphene via fluorescence resonance energy transfer (FRET). We first demonstrate that the graphene FRET aptasensor yields fluorescence when there is a target protein in the sample using prostate specific antigen (PSA, a cancer marker) as the target. We confirm that the fluorescence intensities vary depending on the PSA concentrations. We also discuss the selectivity and limit of detection using a microchannel configuration built on a graphene FRET aptasensor. A similar aptasensor has been intensively studied using graphene oxide (GO) dispersed in aqueous media, but has been little studied on a solid support. By preparing the graphene and GO FRET aptasensor on the same substrate, we show quantitatively that the graphene sensor yields brighter fluorescence than the GO aptasensor. We also demonstrate the response of the graphene FRET aptasensor under sample flow conditions.

DOI： 10.1021/acssensors.6b00191

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

The wettability of hydroxyapatite (HAp) films can be controlled by process conditions and substrates. C-plane-terminated HAp films on Si(100) substrate were hydrophobic. Only when sputter deposition with Ar was carried out with H2O vapor, followed by solid-phase crystallization at 500-700 degrees C, did highly hydrophilic films with water contact angles between 10 and 20 degrees form. The hydrophilic property was characterized by H2O bending mode signals at 1595 cm(-1) in infrared spectroscopy. Preferentially c- or (310)-plane-oriented epitaxial HAp films on sapphire c-planes were hydrophobic, whereas randomly oriented polycrystalline HAp films on sapphire a-planes were moderately hydrophilic. (C) 2015 The Japan Society of Applied Physics

DOI： 10.7567/APEX.8.107001

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

We propose a molecular design for a biomolecular probe to realize an on-chip graphene oxide (GO) aptasensor with enhanced sensitivity. Here, GO works as an excellent acceptor for fluorescence resonance energy transfer. We inserted a rigid double-stranded DNA as a spacer between the GO surface and the aptamer sequence to extend the distance between a fluorescence dye and the GO surface during molecular recognition. We examined the dependence of the sensitivity on the length of the spacer quantitatively by using a 2x2 linear-array aptasensor. We used the modified aptamer with 10 and 30 base pair (bp) double-stranded DNA spacers. The signal with a 30bp-spacer was about twice as strong that with a 10bp-spacer as regards both thrombin and prostate specific antigen detections. The improvement in the sensitivity was supported by a model calculation that estimated the effect of spacer length on fluorescence recovery efficiency.

DOI： 10.2116/analsci.31.875

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

We investigated the crystallinity, orientation, and stability of hydroxyapatite (HAp) thin films on structural materials including SiO2 and metals (Ru, Ti, and Pt). The HAp films were deposited by electron cyclotron resonance (ECR) plasma sputtering with an Xe sputtering gas under simultaneous flow of H2O vapor. The HAp films as-crystallized during deposition and solid-phase crystallized by post annealing were analyzed with X-ray diffraction, Fourier-transform infrared spectroscopy, and Raman scattering. The lowest solid-phase crystallization temperatures were 350 degrees C on Ru, 300 degrees C on Ti, and 300 degrees C on Pt. These crystallization temperatures are much lower than those on silicon and SiO2 substrates (550 degrees C). For HAp films as-crystallized at temperatures above 400 degrees C, the elements out diffused and reacted with substrates. Precipitation of CaO was observed for HAp films deposited on SiO2 and Ru substrates. Diffusion of POET into SiO2 and Ru-catalyzed decomposition of HAp crystals are suggested for the mechanism. When deposited on Pt substrates, CaPt2O4 alloy byproducts were created for solid-phase crystallized films and CaPt2 alloy byproducts were created for as-crystallized films, indicating reaction of Ca atoms with Pt substrates. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.surfcoat.2015.02.011

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

The versatility of an on-chip graphene oxide (GO) aptasensor was successfully confirmed by the detection of three different proteins, namely, thrombin (TB), prostate specific antigen (PSA), and hemagglutinin (HA), simply by changing the aptamers but with the sensor composition remaining the same. The results indicate that both DNA and RNA aptamers immobilized on the GO surface are sufficiently active to realize an on-chip aptasensor. Molecular selectivity and concentration dependence were investigated in relation to TB and PSA detection by using a dual, triple, and quintuple microchannel configuration. The multiple target detection of TB and PSA on a single chip was also demonstrated by using a 2 x 3 linear-array GO aptasensor. This work enables us to apply this sensor to the development of a multicomponent analysis system for a wide variety of targets by choosing appropriate aptamers. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.aca.2014.10.047

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Language：English   Publishing type：Part of collection (book)   Publisher：Pan Stanford Publishing Pte. Ltd.  

DOI： 10.4032/9789814613095

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Terahertz (THz) spectroscopy is a powerful tool for identifying inter-molecular hydrogen bonds in pharmaceutical materials. Here, we present quantitative chemical imaging of multicomponent pellets composed of pharmaceutical cocrystals and cellulose by THz spectroscopy. The stabilized THz time-domain spectroscope with laser beam monitoring and feedback supports accurate absorption spectra measurement. The linearity of THz absorptions of cocrystals and cellulose against the concentration are experimentally verified. In addition, the concentrations of the materials inside pellets are quantitatively extracted and mapped from the THz spectroscopic image by linear regression using reference THz spectra obtained for cocrystals and diluents.

DOI： 10.1109/JLT.2014.2314139

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

We report how the crystallinity and orientation of hydroxyapatite (HAp) films deposited on sapphire substrates depend on the crystallographic planes. Both solid-phase crystallization of amorphous HAp Films and crystallization during sputter deposition at elevated temperatures were examined. The low-temperature epitaxial phase on C-plane sapphire substrates has c-axis orientated HAp crystals regardless of the crystallization route, whereas the preferred orientation switches to the (310) direction at higher temperatures. Only the symmetric stretching mode (v(1)) of PO43- units appears in the Raman scattering spectra, confirming well-ordered crystalline domains. In contrast, HAp crystals grown on A-plane sapphire substrates are always oriented toward random orientations. Exhibiting all vibrational modes (v(1), v(3), and v(4)) of PO43- units in the Raman scattering spectra reflects random orientation, violating the Raman selection rule. If we assume that Raman intensities of PO43- units represent the crystallinity of HAp films, crystallization terminating the surface with the C-plane is hindered by the presence of excess H2O and OH species in the film, whereas crystallization at random orientations on the A-plane sapphire is rather promoted by these species. Such contrasting behaviors between C-plane and A-plane substrates will reflect surface-plane dependent creation of crystalline seeds and eventually determine the orientation of resulting HAp films. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jcrysgro.2014.07.030

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

Optical cavities using air-band states in Si photonic crystals (PhCs) are proposed as biosensors. Since the light in the air band of PhCs is preferably located at the lower-index cladding rather than the inside of higher-index Si, interactions are enhanced between the light and the target molecules in the cladding, being effective for the sensitive detections. Such an air-band PhC is used as an optical cavity, which is surrounded with another PhC as the photonic-bandgap mirrors. Simulations are performed for air-band resonators in one-dimensional (1D) PhC of arrayed holes in a Si channel waveguide, in order to analyze a figure of sensing, i.e., red shifts in the resonance wavelengths induced by the presence of target molecules. The S value, the amount of red shift caused by the unit change in the cladding index, can be as large as 200 nm/RIU, which is 2 times larger than those for ordinary 1D-PhC resonators. Fabricated devices successfully show the resonance peaks, whose wavelengths and quality factors agree well with theoretical ones. These results suggest that the air-band resonators are promising for high-performance biosensors. (C) 2014 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.53.04EG09

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Language：Japanese  

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Hydroxyapatite (HAp) films were deposited by electron cyclotron resonance plasma sputtering under a simultaneous flow of H2O vapor gas. Crystallization during sputter-deposition at elevated temperatures and solid-phase crystallization of amorphous films were compared in terms of film properties. When HAp films were deposited with Ar sputtering gas at temperatures above 460 degrees C, CaO byproducts precipitated with HAp crystallites. Using Xe instead of Ar resolved the compositional problem, yielding a single HAp phase. Preferentially c-axis-oriented HAp films were obtained at substrate temperatures between 460 and 500 degrees C and H2O pressures higher than 1 x 10(-2) Pa. The absorption signal of the asymmetric stretching mode of the PO43- unit (nu(3)) in the Fourier-transform infrared absorption (FT-IR) spectra was the narrowest for films as-crystallized during deposition with Xe, but widest for solid-phase crystallized films. While the symmetric stretching mode of PO43- (nu(1)) is theoretically IR-inactive, this signal emerged in the FT-IR spectra of solid-phase crystallized films, but was absent for as-crystallized films, indicating superior crystallinity for the latter. The Raman scattering signal corresponding to nu(1) PO43- sensitively reflected this crystallinity. The surface hardness of as-crystallized films evaluated by a pencil hardness test was higher than that of solid-phase crystallized films. (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jpcs.2013.08.014

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

Molecular networks based on noncovalent bonds have resonant frequencies in the terahertz (THz) region. THz spectroscopy is a powerful tool for identifying molecular bonds, such as intermolecular or intramolecular hydrogen bonds, in pharmaceuticals. A THz chemical imaging (TCI) system was developed by combining a THz time-domain spectrometer with a translational stage to obtain two-dimensional distributions of molecular networks in tablet samples Since THz spectral peaks of pharmaceuticals are broad at room temperature, multicomponent chemical analysis with the TCI system has some limitations. In this paper, we describe multicomponent,chemical analysis of pharmaceuticals using a sample chamber cooled, by a cryostat. TCI measurement at low temperature sharpens spectral peaks and/or shifts peak frequencies, enabling us to determine the distribution of several kinds of pharmaceuticals in a tablet. The TCI system provides THz images of polymorphic form distribution of famotidine binding with D-mannitol in an over-the-counter pharmaceutical tablet. Furthermore, the molecular mechanics method was used to determine the vibrational modes of the peaks in the spectra of famotidine polymorphic forms. (C) The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.

DOI： 10.1149/2.0201409jes

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In this paper, we describe a nondestructive method of observing changes in the microstructure of optical fibers subjected to CO2 laser irradiation for optical fiber splicing using synchrotron radiation micro-computed tomography (CT). In particular, we evaluated a method of enhancing the contrast between a GeO2-doped optical fiber core and a silica cladding by performing CT observations of the X-ray energy around the Ge-K absorption edge. Specifically, procedures for extracting a GeO2-doped core from a three-dimensional image of optical fibers by the cluster labeling method are proposed and evaluated. The approach enabled us to observe how inclusions at the optical fiber splicing interface influence the optical fiber core structure. We also expect this observation method to be used for improving such aspects of laser processing performance as insertion loss and mechanical strength for recently developed optical fibers. © 2013 The Japan Society of Applied Physics.

DOI： 10.7567/JJAP.52.096602

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

We deposited hydroxyapatite (HAp) thin films on Si(1 0 0) substrates by means of electron cyclotron resonance (ECR) plasma sputtering from a HAp target and characterized their structural properties by X-ray diffraction (XRD) and Fourier transform infrared absorption spectroscopy. Deposition in the presence of an H2O vapor at room temperature incorporated H2O and OH species in the deposited films. Post-annealing in an O-2 ambient self-organized OH- and PO43- functional groups in HAp crystals. The XRD patterns revealed randomly orientation when the annealing temperature ranged between 700 and 900 degrees C. In contrast, preferentially c-axis-oriented HAp crystals nucleated after prolonged annealing at 550-600 degrees C. The possible scenario for the preferred orientation is that C-plane terminated HAp crystallites were initially created in the near-surface region, and the following crystallization proceeded exclusively on the seed surface. After post annealing in a vacuum or in an Ar gas ambient at 900 degrees C, films were reduced into tricalcium phosphate, increasing photoabsorption in the infrared range. (c) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsusc.2013.03.070

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

Terahertz (THz) spectroscopic imaging is a promising technique for distinguishing pharmaceuticals of similar molecular composition but differing crystal structures. Physicochemical properties, for instance bioavailability, are manipulated by altering a drug's crystal structure through methods such as cocrystallization. Cocrystals are molecular complexes having crystal structures different from those of their pure components. A technique for identifying the two-dimensional distribution of these alternate forms is required. Here we present the first demonstration of THz spectroscopic imaging of cocrystals. THz spectra of caffeine-oxalic acid cocrystal measured at low temperature exhibit sharp peaks, enabling us to visualize the cocrystal distribution in nonuniform tablets. The cocrystal distribution was clearly identified using THz spectroscopic data, and the cocrystal concentration was calculated with 0.3-1.3% w/w error from the known total concentration. From this result, THz spectroscopy quantitative chemical mapping of cocrystals and offers researchers and drug developers a new analytical tool.

DOI： 10.1021/ac302852n

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

We have developed a new procedure for fabricating interdigitated array gold electrodes (Au-IDA) modified with reduced graphene oxide (rGO). In this procedure, we coated the gold surface of the micrometer order electrodes with graphene oxide (GO) prior to the reduction and the lift-off processes to avoid short-circuiting the pair of electrodes by conductive rGO flakes after the reduction. We then studied the basic electrochemical activity of the prepared electrodes, rGO/Au-IDA, mainly on p-aminophenol (pAP), because pAP is a good probe for an electrochemical immunoassay. The voltammograms showed that denser rGO provides better electrode reactivity for pAP. We confirmed that redox cycling between the anode and cathode at the rGO/Au-IDA was established, which yields more sensitive detection than with a single electrode. As one application of the electrochemical immunoassay using the rGO/Au-IDA, we demonstrated the quantitative detection of cortisol, a stress marker, at levels found in human saliva.

DOI： 10.2116/analsci.29.55

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

One-dimensional Si photonic crystal waveguides having a partial slot resonator are investigated for biosensing. The thickness of sensing layer for antigen-antibody reactions is found to be one of the critical parameters for the high sensitivity.

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

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

We study protein recognition on a graphene oxide (GO) surface using a single GO piece fixed on a solid support. The GO surface is modified by newly designed processes using pyrene as a linker to an sp(2) domain in the GO, an aptamer for thrombin recognition, and a probe dye for fluorescence detection. In this system, the dye probe fluorescence, which was initially quenched by GO, is recovered when the aptamer recognizes the corresponding protein. We demonstrate the label-free and selective protein recognition for thrombin. The elementary processes of protein recognition are observed directly with a confocal laser scanning microscope and an atomic force microscope using an identical piece of GO. They indicate that proteins are recognized homogeneously on the modified GO surface. We also show that the recognition system can be installed and operated in microchannel devices.

DOI： 10.1039/c2tb00167e

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

We designed a biomolecular probe for highly sensitive protein detection by modifying an aptamer with a DNA spacer. The spacer controls the distance between a fluorescence dye and a quencher, which is crucial for FRET-based sensors. We successfully demonstrated an improvement in the sensitivity of an on-chip graphene oxide aptasensor.

DOI： 10.1039/c3cc45615c

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In order to decrease the impact of diabetes mellitus on patient quality of life, noninvasive and continuous monitoring of blood glucose level represents the ideal detection protocol for an appropriate decision-making process. The limit of detection of such a sensor should be lower than 70 mg/dL for efficient detection of hypoglycemia episodes. However, a reasonable anticipation of loss of accuracy when moving from in vitro to in vivo requires demonstration of sensitivity several times lower than this value in the ideal in vitro conditions for any viable alternative to the standard finger-prick-based method. This paper then investigates the detection of aqueous glucose solutions at low concentration levels based on a measurement protocol called "frequency shift" (FS). This protocol, based on the continuous-wave photoacoustic technique, is equivalent to an acoustic velocity measurement and therefore depends on the temperature as well. A thermo-regulated bath system was then used to control the temperature with an accuracy of ±0.035 C. The sensor showed a linear glucose dependence characterized by a slope of 0.19%/g/dL, which is consistent with previously reported results, and accuracy of about ±26 mg/dL was obtained. Using a differential experimental protocol, we were able to improve the temperature control accuracy down to ±0.015 C. Measurements down to a 9.6 mg/dL concentration level were demonstrated with an accuracy of ±3.5 mg/dL despite a bias from temperature fluctuations equivalent to a ±11 mg/dL glucose concentration variation. The FS protocol then enables low milligram per deciliter glucose concentration measurements at levels several times lower than the requirements. However, temperature variations strongly limit the measurement accuracy due to the lack of FS selectivity to glucose. To take full advantage of the proposed approach, temperature should then be monitored simultaneously and its effect compensated to allow comparable sensitivity in in vivo conditions. © 2013 Elsevier B.V.

DOI： 10.1016/j.snb.2013.05.028

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOC INC  

Molecular networks based on hydrogen bonds have resonant frequencies in the terahertz (THz) region. THz spectroscopy is a powerful tool for identifying molecular networks created by intermolecular or intra-molecular hydrogen bonds in pharmaceutical and biomedical samples such as drugs, proteins, and cancer cells. A THz chemical imaging (TCI) system was developed by combining a THz time-domain spectrometer with a translational stage to obtain two-dimensional distributions of molecular networks in tablet samples. Since THz spectral peaks of pharmaceuticals are broad at room temperature, multicomponent chemical analysis is limited using the TCI system. In this paper, we describe multicomponent chemical analysis of pharmaceuticals using a sample chamber cooled by a cryostat. TCI measurement at low temperature sharpens spectral peaks and/or shifts peak frequencies, enabling us to determine the distribution of several kinds of pharmaceutical chemicals within a tablet.

DOI： 10.1149/05012.0109ecst

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Molecular networks based on hydrogen bonds have resonant frequencies in the terahertz (THz) region. THz spectroscopy is a powerful tool for identifying molecular networks created by intermolecular or intra-molecular hydrogen bonds in pharmaceutical and biomedical samples such as drugs, proteins, and cancer cells. A THz chemical imaging (TCI) system was developed by combining a THz time-domain spectrometer with a translational stage to obtain two-dimensional distributions of molecular networks in tablet samples. Since THz spectral peaks of pharmaceuticals are broad at room temperature, multicomponent chemical analysis is limited using the TCI system. In this paper, we describe multicomponent chemical analysis of pharmaceuticals using a sample chamber cooled by a cryostat. TCI measurement at low temperature sharpens spectral peaks and/or shifts peak frequencies, enabling us to determine the distribution of several kinds of pharmaceutical chemicals within a tablet. © 2012 The Electrochemical Society.

DOI： 10.1149/05012.0109ecst

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

THz spectroscopy is advantageous in analytical chemistry because it can detect and identify intermolecular interactions in chemical compounds, such as hydrogen bonds and hydrations, and molecular networks. Recent advances in THz components, such as ultrashort pulsed lasers and photoconductive antennas, have improved the sensitivity of THz time-domain (TDS) spectroscopy and have made the THz chemical imaging possible. THz chemical imaging can reveal hydrogen bond distributions and will be a very powerful tool in biology, pharmacology, and life sciences. THz-TDS is also promising for the quantitative chemical analysis and detection of molecules and clusters in nanospace and ice.

DOI： 10.1109/TTHZ.2011.2159562

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

We successfully analyzed the concentrations of five amino acids in commercially available dietary amino acid supplements by using terahertz time-domain spectroscopy (THz-TDS) with an error of +/- 12% for the best reproduced components. We also succeeded in analyzing tablets of the supplements wrapped in paper, and thus showed the merit of using THz waves for the nondestructive quantitative analysis of packaged samples by employing the fact that THz waves are capable of passing through several types of packaging material. The ability of THz waves to pass through the paper made it possible to perform a quantitative analysis using the same standard spectra as those used for an unwrapped sample, and the accuracy of a direct quantitative analysis of a packaged sample was almost the same as that of an unwrapped sample.

DOI： 10.2116/analsci.27.351

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DOI： 10.1149/1.3571988

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

A terahertz spectroscopic imaging system was fabricated for the detection of two-dimensional molecular distributions in pharmaceutical tablets based on absorption peaks of intermolecular or intramolecular hydrogen bonds in crystals. The terahertz imaging system consists of a terahertz time-domain spectrometer and a three-dimension translational stage. Using the system, we obtained frequency-dependent terahertz images of famotidine polymorphic forms A and B. An offset subtraction process is useful for detecting the distribution in an inhomogeneous tablet containing a mixture of the two forms. The terahertz imaging technique is a valuable tool for the analysis of polymorphic forms of crystal in inhomogeneous pharmaceutical tablets.

DOI： 10.1080/15421406.2011.563625

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Surface Science Society of Japan  

In order to determine the local structure of carbon sp(2) clusters in chemically modified graphene oxide (GO) flakes, their luminescence was analyzed, using near- infrared photoluminescence (NIR PL) spectral imaging. GO flakes emit a broad PL spectrum of wavelengths of 800 to 1400 nm, indicating that they contain sp(2) clusters, whose size is theoretically estimated to be in the 1.3 to 2.3 nm region. The size distribution of such sp(2) clusters is fairly uniform at different positions and for different numbers of layers of GO, at the spatial resolution of NIR PL image (5 mu m). The analysis by transmission electron microscopy directly confirmed the existence of such sp(2) clusters and the estimated size of the sp(2) clusters was widely ranged from 0.5 to 4 nm. The effect of the GO reduction to the local structure of carbon sp(2) clusters was also studied and it was found that the NIR PL intensity decreased as the reduction progressed and that there was no large spectral shift.

DOI： 10.1380/ejssnt.2012.513

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOC INC  

A terahertz (THz) chemical imaging system was fabricated for the detection of two-dimensional molecular networks in pharmaceutical tablets. Frequency-dependent THz images of homemade tablets containing polymorphic forms enables us to determine the distribution of two polymorphic forms. The system also provided THz images of polymorphic form distribution of famotidine in an over-the-counter drug tablet for the first time. Furthermore, the molecular mechanics method was used to determine the vibrational modes of famotidine polymorphic forms.

DOI： 10.1149/1.3571988

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One of the most attractive hypothesis for the origin of homochirality in terrestrial bioorganic compounds is that a kind of "chiral impulse" as an asymmetric excitation source induced asymmetric reactions on the surfaces of such materials such as meteorites or interstellar dusts prior to the existence of terrestrial life (Cosmic Scenario). To experimentally introduce chiral structure into racemic films of amino acids (alanine, phenylalanine, isovaline, etc.), we irradiated them with linearly polarized light (LPL) from synchrotron radiation and circularly polarized light (CPL) from a free electron laser. After the irradiation, we evaluated optical anisotropy by measuring the circular dichroism (CD) spectra and verified that new Cotton peaks appeared at almost the same peak position as those of the corresponding non-racemic amino acid films. With LPL irradiation, twodimensional anisotropic structure expressed as linear dichroism and/or linear birefringence was introduced into the racemic films. With CPL irradiation, the signs of the Cotton peaks exhibit symmetrical structure corresponding to the direction of CPL rotation. This indicates that some kinds of chiral structure were introduced into the racemic film. The CD spectra after CPL irradiation suggest the chiral structure should be derived from not only preferential photolysis but also from photolysis-induced molecular structural change. These results suggest that circularly polarized light sources in space could be associated with the origin of terrestrial homochirality
that is, they would be effective asymmetric exciting sources introducing chiral structures into bio-organic molecules or complex organic compounds. © 2009 by the authors
licensee Molecular Diversity Preservation International.

DOI： 10.3390/ijms10073044

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Language：Japanese   Publisher：日本セラミックス協会  

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

Terahertz (THz) absorption spectra have been applied to measure the compositions of amino acid samples. Because the concentration information about a specific composition is involved in its spectrum, keeping the spectrum length and dynamic range as wide as possible is essential for precise measurements. It is well known that a spectrum is always contaminated by apparatus noises. In this paper, we present a criterion for noise cutting based on wavelet transform, which usually extends the range determined by traditional threshold criterion. Finally, the improvement on measurement precision shows the validity of the new criterion. © 2009 Higher Education Press and Springer-Verlag GmbH.

DOI： 10.1007/s12200-009-0051-7

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

We developed a molecular-recognition material of low-molecular-weight organic Compounds by using mesoporous silicas, and applied this material to a chemical sensor, aiming at the development of new and practical analytical techniques. We have found that it is important to determine the optimized surface condition and the porosity of mesoporous silicas to compare very similar molecules, namely benzene and toluene, which have no and one methyl group, respectively, in their Molecular structures. We applied mesoporous silica to a micro gas-sensing system, which has been originally developed. We Succeeded to detect benzene gas at ppm levels in car exhausts containing interference components. We also found that mesoporpos silica is an excellent optical material in the terahertz region, and we developed a useful way for terahertz time-domain spectroscopy to distinguish between intra- and intermolecular modes by incorporating target molecules in nano-sized spaces of nanoporous materials.

DOI： 10.2116/bunsekikagaku.57.871

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

The spatial resolution of transmitted terahertz (THz) images of metal slits and protein [myoglobin (Mb)] thin films was analyzed at 1.40, 1.63, and 2.55THz by using continuous THz waves from a tunable gas laser. The resolution of the THz images of the metal slit was 0.40, 0.35, and 0.45mm at 2.55, 1.63, and 1.40THz, respectively. The spatial resolution is determined not only by the diffraction limit of the wavelength of the THz wave but also by other experimental conditions such as laser power. The resolution of the THz images of Mb thin films was 0.55 and 0.60 mm at 2.55 and 1.63 THz, respectively. The approximately twofold stronger THz wave absorption of Mb film at 2.55 THz than at 1.63 THz provides the better resolution. By using a THz wave with a frequency at which the target sample has strong absorption we can obtain a THz image with good resolution.

DOI： 10.1143/JJAP.47.1315

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Language：English   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

Recent progress in analytical terahertz (THz) spectroscopy is reviewed with illustrative examples showing that it is an effective method for detecting and identifying intermolecular interactions in chemical compounds, such as hydrogen bonds. The unique and characteristic properties of THz waves, their significance to both science and industry, and the bases of one of the successful fields of analytical THz spectroscopy, namely THz time-domain spectroscopy and THz imaging for chemical analysis, are described. Preliminary quantitative studies are presented to show the potential of THz spectroscopy for the detection and identification of intermolecular hydrogen bonds in unknown mixture samples. The selective detection of intramolecular hydrogen bonds and the detection of intramolecular interactions in ice are also introduced. Some brief remarks are provided on future developments, the main issues, and the prospects for analytical THz spectroscopy.

DOI： 10.2116/analsci.24.185

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DOI： 10.1143/JJAP.47.1315

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

The hydrogen bond resonance of a sodium chloride (NaCl) ion pair trapped in aqueous ice has been observed by transmission terahertz time-domain spectroscopy. The absorption peak of a sodium chloride ion pair in ice is 1.65 THz at 83 K. By investigating the interaction of the cation and anion with other chemical compounds, we deduce that the absorption peak originates from the hydrogen bond resonance of sodium chloride and water molecules. The charge redistribution that occurs when other ion pairs are added to aqueous salt solution changes the absorption spectrum. Furthermore, the results also indicate that simple molecules such as sodium halides have fingerprints in the terahertz region when the ions are trapped in ice. NaCl ion pairs in seawater and in Ringer's solution were examined.

DOI： 10.2116/analsci.23.917

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

Terahertz time-domain spectroscopy (THz-TDS) is used to study the intra- and intermolecular vibrational modes of aromatic carboxylic acids, for example, o-phthalic acid, benzoic acid, and salicylic acid, which form either intra- or intermolecular hydrogen bond(s) in different ways. Incorporating the target molecules in nano-sized spaces in mesoporous silicate (SBA-16) is found to be effective for the separate detection of intramolecular hydrogen bonding modes and intermolecular modes. The results are supported by an analysis of the differences in the peak shifts, which depend on temperature, caused by the different nature of the THz absorption. Raman spectra revealed that incorporating the molecules in the nano-sized pores of SBA-16 slightly changes the molecular structures. In the future, THz-TDS using nanoporous materials will be used to analyze the intra- and intermolecular vibrational modes of molecules with larger hydrogen bonding networks such as proteins or DNA.

DOI： 10.2116/analsci.23.803

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

We have generated terahertz (THz) waves by difference frequency generation (DFG) with a 1.55 mu m pump laser. 1.55 mu m pump beams were effectively converted to 1 THz waves through a periodically chi((2))- inverted GaP stack fabricated by direct wafer bonding. The output efficiency was an order of magnitude larger than that of typical chi ((2)) materials such as lithium niobate employing a similar DFG method. To investigate the increase in output power due to quasi-phase matching including optical losses, we measured its dependence on stack length. From the measured data, we analyze the conditions for effective power enhancement and show that it takes place if the pump-beam loss, alpha, is much smaller than that of the THz waves, alpha (3) (or the pump-beam attenuation length, 1/alpha, is much longer than that of the THz waves, 1/alpha(3),), which is achieved by improving the bonding quality of the stack. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/pssa.200622323

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

We have generated terahertz (THz) waves by difference frequency generation (DFG) with a 1.55 μm pump laser. 1.55 μm pump beams were effectively converted to 1 THz waves through a periodically χ (2)-inverted GaP stack fabricated by direct wafer bonding. The output efficiency was an order of magnitude larger than that of typical χ (2) materials such as lithium niobate employing a similar DFG method. To investigate the increase in output power due to quasi-phase matching including optical losses, we measured its dependence on stack length. From the measured data, we analyze the conditions for effective power enhancement and show that it takes place if the pump-beam loss, α, is much smaller than that of the THz waves, α 3 (or the pump-beam attenuation length, 1/αa, is much longer than that of the THz waves, 1/α 3), which is achieved by improving the bonding quality of the stack. © 2007 WILEY-VCH Verlag GmbH &amp
Co. KGaA.

DOI： 10.1002/pssa.200622323

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DOI： 10.5111/bunkou.56.15

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

The inter- and intramolecular hydrogen-bonding modes of two steric isomers, namely fumaric acid and maleic acid, are observed by using terahertz time-domain spectroscopy (THz-TDS). The intermolecular modes observed with fumaric acid crystals are inactivated by incorporating the molecules in the nano-sized pores of a mesoporous silicate (SBA-16) due to the separation of the molecules, whereas the intramolecular modes of maleic acid of the crystal and the incorporated samples are similar.

DOI： 10.1246/cl.2006.1128

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

The measurement of absorption spectra using angle-dependent terahertz (THz) time-domain spectroscopy for amino acid single crystals of L-cysteine and L-histidine is reported for the first time. Linearly polarized THz radiation enables us to observe angle-dependent far-infrared absorption spectra of amino acid single crystals and determine the direction of the oscillating dipole of the molecules in the 20-100 cm(-1) range. By comparing the THz spectra of a single crystal and powder, we found that there was a clear hydrogen-bond peak in the crystal spectrum as a result of the larger hydrogen-bond network. The low-temperature THz spectra of amino acid microcrystals showed more intermolecular vibrational modes than those measured at room temperature. An ab initio frequency calculation of a single amino acid molecule was used to predict the intramolecular vibrational modes. The validity of the calculation models was confirmed by comparing the results with experimentally obtained data in the Raman spectral region.

DOI： 10.1021/jp060492n

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

The prognostic significance of p53 mutation, microsattelite instability and DNA mismatch protein hMLH1 expression in suboptimally resected advanced ovarian carcinoma treated with the combination chemotherapy of paclitaxel and carboplatin was evaluated. The overall combination chemotherapy response rate and the complete remission rate were significantly higher among patients with mutant p53 tumors than those with wild-type p53 tumors (35/42 (83%) vs. 32/58 (55%); P=0.003 and 18/42 (43%) vs. 16/58 (28%); P=0.03, respectively). This tendency apparently existed in non-serous carcinoma, but not in serous carcinoma. Univariate analysis showed that the risk of death due to disease and risk of progression was significantly lower among patients with p53 mutation (P=0.0357 and 0.0281, respectively). However, the presence of microsattelite instability or loss of hMLH1 expression was not associated with either the clinical response or prognosis. Determining p53 mutational status can be useful in predicting therapeutic response to drugs in ovarian carcinoma, especially in non-serous tumors. (c) 2005 Elsevier Ireland Ltd. All rights reserved.

DOI： 10.1016/j.canlet.2005.10.035

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Language：English   Publisher：AMER CHEMICAL SOC  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCI PRINTERS & PUBL INC  

BACKGROUND: Spontaneous rupture of uterine surface varicose veins is rare but may become a serious complication of pregnancy.
CASE: A 40-year-old woman, gravida 2, para 0-0-1-0, presented with worsening generalized abdominal pain after occasional nausea, vomiting and diarrhea over the previous 2 days. After a 4-hour observation period, sudden onset of severe, prolonged fetal heart rate decelerations was recognized along with frequent uterine contractions. Emergency cesarean section was performed under a tentative diagnosis of placental abruption. A live, female infant weighing 1,730 g was delivered and had Apgar scores of 5 and 9 at 1 and 5 minutes, respectively. Intraoperatively, approximately 500 mL of hemoperitoneum was present, and multiple bleeding sites from varicose veins on the posterior uterine surface were detected. Because the maternal vital signs became unstable and hemostasis was difficult, hysterectomy was performed and blood transfusion administered.
CONCLUSION: Although very rare, hemoperitoneum should be included in the differential diagnosis when a pregnant woman experiences acute-onset, severe abdominal pain, even without an episode of abdominal trauma.

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

Attenuated total reflection Fourier transform infrared spectra are recorded for a number of diamond molecules (or higher diamondoids) in the spectral range between 650 and 3000 cm(-1). Molecules studied are diamantane, triamantane, [121]tetramantane, [123]tetramantane, [1(2,3)4]pentamantane, [12(3)4]pentamantane, 3-methyl-[1(2,3)4]pentamantane, and [12312]hexamantane (cyclohexamantane). Spectral trends are clearly recognized throughout the spectra revealing the general fingerprint of this class of molecules. In general, the spectra show good agreement with density functional theory calculations at the B3LYP/D95(d,p) level of theory. (c) 2006 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jms.2006.05.001

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

The quantitative analysis of amino acids by terahertz (THz) time-domain absorption spectroscopy is demonstrated. The optical densities of the amino acids were found to be linearly proportional to the concentration. The molar absorption coefficients of L-glutamic acid (L-Glu), L-glutamic acid sodium salt ( Na- L-Glu), L- glutamic acid hydrochloric salt (HCl-L-Glu), L- cysteine (L-Cys), and L- histidine ( L- His) were calculated by averaging the THz spectra of the amino acids at several different concentrations in approximately the 0.2-1.0 mol L-1 range. The concentrations of L-Glu, L-Cys, and L- His mixed samples were successfully calculated with errors of less than 11% and 20% when their concentrations were higher than 0.45 and 0.22 mol L-1, respectively, by using the obtained molar absorption coefficient.

DOI： 10.1021/ac060520y

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Language：Japanese   Publisher：公益社団法人 電気化学会  

DOI： 10.5796/electrochemistry.74.506

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

We propose a THz notch filter that uses the absorption of the intermolecular hydrogen bonds in a molecular crystal such as sucrose. Terahertz ( THz) time-domain spectroscopy was used to investigate the absorption characteristics of a rotationally oriented sucrose single crystal in the 0.3-3.0 THz frequency range. The crystal was set so that the ( 100) face ( cleavage) was normal to the THz propagation direction. The two lowest frequency intermolecular hydrogen bonding bands clearly exist at room temperature and at 1.45 and 1.64 THz when the b-axis of the crystal is parallel and perpendicular to the THz polarization, respectively. In contrast, they disappear when the b-axis is reversed. This absorption feature means that it would be possible to utilize a sucrose crystal as a notch filter with a 1.45-THz band center for the 0.1-1.7 THz range and with a 1.64-THz band center for the 0.1-1.9 THz range. When the crystal is rotated, the transmitted intensities of the frequency components near the absorption bands alternate as a sine function against angle. The spectroscopic properties of the sucrose filter were confirmed by continuous THz wave imaging. (c) 2006 Optical Society of America.

DOI： 10.1364/OE.14.005765

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

We have realized a terahertz (THz)-wave source employing difference frequency generation (DFG) from a quasi-phase-matched GaP stack pumped at 1.55 mu m. We observed THz waves with enhanced power by quasi-phase matching (QPM) in the < 110 > direction of GaP with a < 111 > polarization direction for the incidence of two pump lights with the same propagation and polarization directions. We obtained THz-wave power proportional to the product of two pump-light powers due to DFG. We also confirmed that power peaks appeared at around 1 and 2.6 THz reflecting the first- and the third-order QPM, respectively.

DOI： 10.1063/10274832

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

We propose a novel method to realize widely tunable terahertz-wave generation from GaP by collinearly phase-matched difference-frequency generation. Our method makes it possible to achieve a wavelength-tunable output without decreasing the output efficiency, which can be used for wavelength sweeping in spectroscopy.

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The gas selectivities of highly ordered mesoporous silicates and commercially-obtained porous silicates with respect to benzene, toluene and xylene were studied. After studying the porosities, pore uniformities, and surface silanol structures of the silicates and their relationships to gas selectivity in detail, we found that we could achieve high benzene selectivity by controlling the micropore size (less than 1 nm). Concluding that mesoporous silicate has a suitable micropore size and structure for benzene selectivity, we also observed that mesoporous silicate SBA-16 exhibited a high (>6) benzene selectivity from toluene and xylene even in a pseudo-atmospheric environment. A benzene detection limit of about 100 ppb was achieved by introducing SBA-16 into a microfluidic device originally developed for the separate detection of benzene, toluene, and xylene gases. © Springer-Verlag 2005.

DOI： 10.1007/s00216-004-2974-6

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Mesoporous silica SBA-15 and SBA-16 films can be successfully prepared on a substrate by a simple method involving a rapid heating process, which is controlled by a voltage applied to a heating electrode on the substrate. This advantageous method has considerable potential for electronic device fabrication processes. Copyright © 2005 The Chemical Society of Japan.

DOI： 10.1246/cl.2005.328

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We have studied the changes in the adsorption characteristics of mesoporous silicate (SBA-15) for benzene and toluene that are caused by using different calcination temperatures (Tc = 773 to 1173 K) in the synthesis process. We found that SBA-15 calcined at 773 K shows an extremely high benzene selectivity, especially in the low pressure region, while SBA-15 treated at higher Tc shows lower selectivity. In order to analyze the benzene selective mechanism, we studied the structures of the SBA-15 series, including their meso- and microporosity in detail. We found that the BET surface area (SBET) and the peak position of the mesopore diameter (2R p) decreased, the peak position of the micropore diameter (2r p) increased, and the 2rp distribution became broader with increasing Tc. Among above factors, we conclude that the size and the distribution of 2rp are the most important to achieve a high benzene selectivity. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2005.

DOI： 10.1039/b410851e

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

A tunable frequency terahertz; (THz) wave source provides spectral images of chromoprotein and chromophore films on quartz plates. A Near-infrared (NIR) Raman microprobe mapping technique is used to measure the same regions in the films in order to detect the molecular structure and to understand THz spectral images. The fact that there is little fluorescence interference in NIR Raman microscopy for the colour films is an advantage over visible Raman microscopy. A combination of THz spectral imaging and NIR Raman microscopy techniques enables us to observe the distribution of molecules and to expand the field of THz imaging research.

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

The absorption spectrum of a protein, namely horse heart myoglobin, was measured by terahertz time-domain spectroscopy of up to 2.75 THz. High-power THz radiation from a tunable cw gas-vapour laser was used to perform two-dimensional imaging. Clear images of the protein film were obtained by monitoring it at the absorption peak frequency. Experimental results show that a spectral image of biological samples can be obtained by employing THz radiation in real time.

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

DOI： 10.1109/LEOS.2005.1547967

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ROYAL SOC CHEMISTRY  

In order to improve the sensitivity of portable air monitoring system based on absorption microdetection cell, we proposed different fabrication processes and tested its regarding the optical guidance efficiency. Two materials (Aluminum and Titanium / Platinum) have been coated on the microchannels sidewalls as reflective layers. Due to its better reflective properties in UV range, Aluminum yields to improvement by a factor of 2 in terms of coupling efficiency through a 3 cm long optical cell, while the gain is around 30% with Titanium/Platinum.

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DOI： 10.1016/j.physe.2004.04.018

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Vibrational analysis is carried out for the radical anions of naphthalene-h8 and -d8. Their infrared (IR) spectra are observed in tetrahydrofuran by using a cell designed for IR measurements of unstable species. The vibrational force field and the IR intensities are calculated by the ab initio molecular orbital and density functional methods at various theoretical levels. As found in the cases of the radical cations of many polycyclic aromatic hydrocarbons (PAHs), a few strong IR bands with intensities of the order of 102 km mol-1 are observed in the 1700-900 cm -1 region. These observed spectral features are well reproduced by the calculations at the CASSCF (complete active space self-consistent field) and B3LYP (Becke's three-parameter hybrid method using the Lee-Yang-Parr correlation functional) levels. The calculation at the B3LYP level gives a better fit between the observed and calculated absolute IR intensities. Normal modes and the origin of the strong IR intensities characteristic of the radical anions are discussed in terms of molecular symmetry coordinates and the dipole derivatives based on these coordinates. It is found that the IR intensities of the b2u modes below 2000 cm-1 are dominated by the contribution from one molecular symmetry coordinate, in which the C-C bonds in one ring stretch while those in the other ring shrink. The mechanism that gives rise to the strong IR intensity for this vibration is discussed by examining the changes in the electronic structure induced by this vibration.

DOI： 10.1139/v04-050

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Single-wall carbon nanotubes (SWNTs) suspended between ultra-fine Si nanopillars were characterized by microscopic Raman spectroscopy. The Raman signals from the suspended SWNTs are extremely intense, compared with those from the carbon nanotubes that grow on the flat surface of substrates and adhere tightly to the substrate surfaces. This intensity enhancement makes it possible to discriminate the Raman signals of the suspended SWNTs from these of carbon nanotubes on the substrate surface and thereby detect the signals from the suspended SWNTs selectively. Based on this novel phenomenon, the structural features of the suspended SWNTs are analyzed. © 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2004.01.054

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The high benzene gas selectivity of mesoporous silicate (SBA-15) was observed in the sub-nanometre micropore condensation region. The benzene/toluene ratios of the adsorbed amount were >100 and >6 in ideal and pseudo-atmospheric environments, respectively. © 2004 The Royal Society of Chemistry.

DOI： 10.1039/b316799b

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We have developed a portable automatic measurement system for the detection and identification of aromatic volatile organic compound (VOC) gases, namely benzene, toluene, and xylenes (BTX), which are air pollutants, by assembling two microfluidic devices, a concentration cell and a detection cell, and peripheral devices. We combined the processes of gas concentration and thermal desorption performed by the concentration cell, with the process of spectroscopic detection performed by the detection cell. We achieved a 50ppb detection limit for toluene gas as an example of BTX detection in a sampling time of 30min. We also found that we could obtain better BTX separation by using a highly ordered mesoporous silicate as a gas adsorbent due to a function of its nano-sized pores. As a result, we successfully measured ppm level concentrations of BTX in a mixture gas separately with this device. © 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0925-4005(03)00540-9

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人 電気学会  

Airborne benzene, toluene, and xylene (BTX) are aromatic volatile organic compounds (VOCs) of great social and environmental significance. Since they are toxic even at ppb concentrations and their levels of toxicity are different, quantitative identification of VOCs in the air is required. We developed small (37cm x 28 cm x 10cm) VOC detection system (fig.1) comprising microfluidic device (concentration and detection cells, 1 cm x 3 cm, respectively), a pump, a deuterium (D₂) lamp, an UV spectrometer, and a SCSI interface. When BTX mixture gas was introduced into this detector, we successfully obtained the component ratios.

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Mesoporous materials are a focus of research due to their porous structure and high surface area. These innovative mesoporous materials has uniform pore size and periodic porous structural properties while retaining their basic mesoporous characteristics. This paper reports on the platinum surface modification of SBA-15, that is, the growth of platinum exclusively in the micropores on a mesoporous surface by means of radiation treatment.

DOI： 10.1002/adma.200390118

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The mesoporous materials SBA-15 and SBA-16 from the self-assembled template organic framework inorganic compound materials are successfully prepared with powder and film states. The powder state of mesoporous material exhibit a variety of properties and possibilities of these kinds of materials. The film state of these SBA-15 and SBA-16 are successfully fabricated into the surface photo voltage (SPV) type gas sensor device as a gas adsorption insulator layer. These kinds of gas sensors device exhibit NO and NO2 gas sensing properties dependent on their mesoporous film structure. We are succeeded in indication about a possibility of mesoporous silicate film for the SPV type gas sensor application. Keywords: mesoporous silicate, SBA-15, SBA-16, NO, NO2, gas sensor, Surface Photo Voltage. © 2003, The Institute of Electrical Engineers of Japan. All rights reserved.

DOI： 10.1541/ieejsmas.123.118

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We have developed a gas sensing microfluidic device for the detection and identification of aromatic volatile organic compound (VOC) gases, namely, benzene, toluene, and xylenes (BTX), which are air pollutants. We combined a nanostructured material, mesoporous silicate, as a gas concentrator and separator, and carried out spectroscopic measurement with a microfluidic device for gas identification and quantitative detection. Our method is completely different from conventional methods such as gas chromatography (GC)/mass spectrometry(MS) and provides a portable, highly sensitive and selective gas monitoring system. In this paper, we report an improvement in the performance of our BTX gas sensor that we realized by optimizing the operating conditions and by using the properties of mesoporous silicate with uniform nanosized pores. We also successfully measured mixture BTX gases separately with this device. We were able to realise better BTX separation with mesoporous silicate than with random-structured silicates. We successfully analyzed the principle behind the improvement in the gas separation owing to the characteristics of the nanosized pores of mesoporous silicate by positron annihilation spectroscopy.

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Airborne benzene, toluene, and xylene (BTX) are aromatic volatile organic compounds (VOCs) of great social and environmental significance. Since they are toxic even at ppb concentrations and their levels of toxicity are different, quantitative identification of VOCs in the air is required. We developed small (37cm x 28 cm x 10cm) VOC detection system (fig.1) comprising microfluidic device (concentration and detection cells, 1 cm x 3 cm, respectively), a pump, a deuterium (D2) lamp, an UV spectrometer, and a SCSI interface. When BTX mixture gas was introduced into this detector, we successfully obtained the component ratios. © 2003, The Institute of Electrical Engineers of Japan. All rights reserved.

DOI： 10.1541/ieejsmas.123.134

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Publishing type：Research paper (international conference proceedings)  

A self-ordered hexagonal and cubic-like mesoporous silica film has been successfully fabricated from a Metal-Insulator-Semiconductor device applied to a Nitrogen oxides (NOx) gas sensor based on the surface photo voltage system. These self-ordered mesoporous silica films are synthesized by using a nonionic triblock copolymer surfactant as a template in spin coating. The sensing characteristics as a NOx gas sensor are dependent on both mesostructures and exposure gases. © 2003 Elsevier Science B. V. All rights reserved.

DOI： 10.1016/S0167-2991(03)80500-1

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The radio frequency (RF) sputtering method was used to prepare nanoscale platinum (0) particles highly dispersed in a graphite-like carbon film (Pt-NEGCF) by co-sputtering platinum and carbon. The preparation is very simple, controllable, and reproducible. We studied this film with respect to its structural characterization and electrocatalytic properties. The XPS spectrum reveals that the platinum state in the Pt-NEGCF is platinum (0). TEM images show that the structure of the carbon in the film is graphite-like and that the platinum particles are highly dispersed in the carbon matrix. The electrochemical properties of the Pt-NEGCF electrode were evaluated. Compared with Pt bulk electrode, this film electrode is highly electrocatalytic as regards hydrogen evolution, dioxygen reduction, and hydrogen peroxide oxidation with good stability.

DOI： 10.1021/cm020636k

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We achieved separate detection of the components of 10 ppm of a benzene, toluene, and o-xylene mixture gas by using mesoporous silica powder incorporated in our microfluidic device. The device consists of concentration and detection cells formed of 3 cm × 1 cm Pyrex plates. We first introduced the mixture gas into the concentration cell where it was adsorbed on an adsorbent in a channel formed in the cell. We then raised the temperature using a thin-film heater and introduced the desorbed gas into the detection cell. Here, we measured the changes in the absorption spectra of the mixture gas in the detection cell. We found that the mixture ratio of the compounds in the desorbed gas varies with time because the thermal desorption property of each compound is different from that of the adsorbent. We analyzed the thermal desorption mechanism by comparing two types of silica adsorbents with different pore structures. We found that an adsorbent that has pores with a periodic and uniform nanosized column shape provides better component separation. We concluded that the uniform pore structure might cause the adsorbate molecules to exhibit a homogeneous adsorption state thus revealing the desorption properties of the gas more clearly.

DOI： 10.1021/ac0201732

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A self-ordered cubic-like mesoporous silica film has been successfully fabricated in a metal-insulator-semiconductor (=Au/SiO2 (cubic-like meso)/Si3N4/SiO2/Si) device based on the surface photovoltage (SPV) system and applied to an NO gas sensor. The self-ordered cubic-like mesoporous silica film is synthesized by using as a template in spin coating a nonionic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO100-PPO65-PEO100) type triblock copolymer surfactant. The sensing characteristics of the self-ordered cubic-like mesoporous SPV system have been investigated by repeated exposure to 100 ppm NO gas and standard air, as well as observation of the alternating (photo) current, which resulted from the physical adsorption and chemical interactions between detected NO gas and the self-ordered cubic-like mesoporous film. In sensing NO gas, this cubic-like mesoporous SPV system exhibits a response nearly five times larger than that of a simple SPV sensor without mesoporous silica film. Even at room temperature, this mesoporous SPV system exhibits a recoverable response. These results can be explained by the characteristics of the cubic-like mesoporous silica film including large surface area and a bi-continuous mesopore structure. This kind of mesoporous film has a great potential for application to highly sensitive and responsive gas sensors. © 2002 Elsevier Science Inc. All rights reserved.

DOI： 10.1016/S1387-1811(02)00387-6

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Self-ordered hexagonal and cubic structured mesoporous silicate film combined SPV type gas sensors (SPV-hex and SPV-cub) were successfully fabricated. These sensors have a sensitivity for NO gas and exhibit different sensing performance depending on the accessibility of the mesostructure to the gas.

DOI： 10.1002/1521-4095(20020605)14:11<812::AID-ADMA812>3.0.CO;2-W

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Self-ordered mesoporous silicate films from organic-inorganic compound materials are successfully fabricated into the surface photo voltage (SPV) type gas sensor device as a gas adsorption insulator layer. These kinds of gas sensors device exhibit NO gas sensing property dependent on their mesoporous film structure. We are succeeded in indication about a possibility of mesoporous silicate film for the SPV type gas sensor application.

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The mesoporous materials from the self-assembled organic-inorganic compound materials have great possibilities for a variety of applications. However, to make use of these kinds of materials effectively, they must be controlled. In this paper, were are succeeded in powder state pore size control and in significantly fabrication film state for device application use.

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We integrated an air-cooled cold trap (CT) channel in a microfluidic device for monitoring airborne benzene, toluene, ethylbenzene, and xylene (BTEX) gases and demonstrated its effect on improving the detection limit of the microfluidic device. The device consists of concentration and detection cells formed of 3 × 1 cm Pyrex plates. We first introduced a sample gas into the concentration cell, and the gas was adsorbed onto an adsorbent in the channel. We then raised the temperature using a thin-film heater and introduced the desorbed gas into the detection cell. To prevent dilution of the gas before detection, we propose an improvement to the concentration cell structure that involves the integration of the CT channel. We examined the CT effect by comparing three types of concentration cell with different channel structures. We found that we could detect a gas concentration about 2 orders of magnitude lower than in our previous work by optimizing the channel structure and integrating a CT channel. As an example of BTEX detection, we obtained a 0.05 ppm detection limit for toluene gas with a sampling time of 30 min.

DOI： 10.1021/ac0110810

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

We have used near-infrared (NIR) Raman spectroscopy to study a coloration reaction that occurs in nano-sized pores in a porous glass chip. This coloration reaction is a modified Saltzman reaction that produces an azo dye by selective reaction with nitrogen dioxide gas (NO2). Neither the details of the reaction mechanisms in the nano-sized pores nor the interaction between the products and the pore surface have previously been investigated. We analyzed the mechanism by measuring the Raman intensity of the azo dye produced in the pores. We found that, in the early stages of NO2 exposure, the NO2 gas reacts at the surface of the porous glass chip, while in the later stages more NO2 gas diffuses into deeper areas without reacting with the reagent. We estimated the limit of the NO2 gas diffusion distance to be about 500 m We also analyzed the interaction between the azo dye and the surface of the pores by comparing the Raman spectrum in the porous glass chip with that in a bulk d(4)-methanol solution. The azo dye is mainly adsorbed as a result of hydrogen bonding between the pi-electrons of the phenyl group and the silanol of the glass surface. We also determined that the azo dye has a trans-conformation molecular structure by calculating the total steric energy. The interaction between the azo group and the silanol is weaker in the adsorbed state than in bulk, due to the steric effect of the bulky substituents around the azo group. Our proposed geometry for the azo dye adsorbed on the surface of the pores has a flatter orientation.

DOI： 10.1039/b200510g

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We developed a micro-fluidic device to identify and quantify airborne aromatic volatile organic compounds (VOCs: benzene, toluene, and xylenes) in car exhaust fumes. The device consists of concentration- and detection-cells made of glass plates. The concentration-cell is composed of an adsorbent to concentrate VOC gases and a thin-film platinum heater to desorb the concentrated gas thermally. Absorption spectra of the concentrated gases are measured in the detection-cell which is connected to the concentration-cell. We successfully measured 50 ppb of toluene. This device is expected to be applied in field monitoring because it is easy to maintain and can measure VOCs every hour.

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Language：Japanese   Publisher：電気学会  

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High-resolution soft X-ray emission and absorption spectra in the C K region of hydrofullerene, which probably consists mainly of C60H36, were measured using highly brilliant synchrotron radiation to identify its molecular structure and electronic structure. Comparison with the C2p-DOS spectra, calculated by discrete variational (DV) Xα molecular orbital calculations, of three possible C60H36 isomers, showed that the measured X-ray spectra approximately agreed with the calculated C2p-DOS spectra of the T-symmetry isomer. The X-ray spectral features were explained by the electronic structure hybridized between the sp2 and sp3 carbon atoms of the T-symmetry C60H36. © 2000 Elsevier Science B.V.

DOI： 10.1016/S0368-2048(00)00101-8

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Partial-fluorescence-yield (PFY) x-ray absorption measurements, using the optimized window widths of position sensitive detectors in wave-length dispersive x-ray spectrometers, have been applied for radiative-process-resolved (RPR) x-ray absorption spectroscopy. We have measured PFY-absorption spectra of graphite and diamond at the C K threshold and of h-BN and c-BN at the B K threshold. Resonant elastic x-ray scattering was observed in graphite and h-BN on their PFY-absorption spectra, and excitonic x-ray scattering was observed in diamond and c-BN. These results show that PFY-absorption measurements for RPR x-ray absorption spectroscopy can provide the information about the electronic structures and the radiative-decay process in inner-shell excitation.

DOI： 10.1107/S0909049500015867

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Soft X-ray emission spectra in the O K region of oxygen incorporated in microporous carbon were measured using synchrotron radiation, in order to observe directly the oxygen on the graphitic surface in micropores and obtain information about its chemical bonding states. The O K X-ray emission spectra of the microporous carbon exhibited a main peak at 526 eV with a low-energy tail, and the reference compounds also exhibited similar spectral features. A spectral feature analysis of the reference compounds using discrete variational Xα molecular orbital calculations showed that the measured 526-eV peaks of the microporous carbon may be due to O2p orbitals and the low-energy tails be to the hybridized O2p/O2s orbitals.

DOI： 10.1016/S0368-2048(00)00417-5

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Soft X-ray emission and absorption spectra in the O K region of oxygen incorporated in microporous carbon were measured using synchrotron radiation, in order to directly observe the oxygen and identify its chemical bonding states on the graphitic surface in microporous carbon. The O K X-ray emission spectrum exhibits a peak at 526 eV with a low-energy tail, and the absorption spectrum at the O K threshold exhibits a sharp peak at 531.5 eV and then rises from 535 eV. Spectral feature analysis using DV-Xα molecular orbital calculations show that the measured X-ray spectra are not sufficiently explained by H2O or typical substituents, such as -OH, -CHO, and -COOH, on the graphitic surfaces. © 2001 Elsevier Science Ltd.

DOI： 10.1016/S0008-6223(00)00259-1

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We directly observed azo dye in a porous glass chip by near-infrared (NIR) Raman spectroscopy. We produced the dye by a modified Saltzman reaction by using sulfanilamide (SFA) and N, N-dimethyl-1-naphthylamine (DMNA) as reagents and used it for the selective sensing of atmospheric nitrogen dioxide gas (NO2). The use of NIR laser excitation is particularly advantageous for the direct measurement of azo dye because it avoids the problem of interference from fluorescence. We obtained the 1597 cm-1 band assigned to the phenyl group stretching mode and the 1415 cm-1 band assigned to the azo group stretching mode. The Raman intensity and visible absorption intensity of the peaks of the azo dye in a porous glass chip increased as we increased the exposure time to NO2. This allowed us to monitor the NO2-sensing reaction in a porous glass chip using NIR Raman spectroscopy. Furthermore, we determined the depth profiles of the azo dye concentration in the porous glass chip by confocal NIR Raman spectroscopy and found that they were different in the early and later NO2-exposure stages. This result indicates that the consumption of the NO2-sensing reagents that accompany azo dye production occurs preferentially at the surface to the deeper regions of the porous glass chip.

DOI： 10.1366/0003702011953397

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Soft X-ray emission and absorption spectra in the C K region of amorphous carbon films systematically deposited by RF, ion-beam, and ECR sputtering under various deposition conditions were measured using highly brilliant synchrotron radiation. A broad main peak and a high-energy shoulder were observed in the emission spectra, and a fine structure consisting of at least five peaks was observed in the absorption spectra. By analogy to the occupied/unoccupied C2p-DOS obtained by DV-Xα molecular orbital calculations of simple cluster models composed of sp2 and sp3 carbon atoms, we approximately explained the spectral features in the measured X-ray emission spectra by σ and π bonds and estimated the fine structures in the absorption spectra by the hybridized unoccupied molecular orbitals formed by the local-structures composed of sp2 and sp3 carbon atoms. © 2001 Elsevier Science Ltd.

DOI： 10.1016/S0008-6223(00)00260-8

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Soft x-ray emission and absorption spectra in the C K region of Mo/SiC/Si multilayer mirrors were measured using highly brilliant synchrotron radiation to identify the chemical bonding states of the buried silicon carbide layers. Comparison with the C 2p density of state (DOS) spectra, calculated by discrete variational-Xα molecular orbital calculations, of several SiC-based cluster models showed that the measured x-ray spectra approximately agreed with the calculated C 2p-DOS spectra of the c- and h-SiC-based SiCx models in which some silicon atoms were replaced by carbon atoms. The chemical bonding states of the silicon carbide layers in the Mo/SiC/Si multilayer mirrors were therefore estimated to be carbon-excessive silicon carbide. © 2000 American Institute of Physics.

DOI： 10.1063/1.1318231

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Publishing type：Research paper (scientific journal)  

The possible configurations of benzene and pyridine molecules adsorbed in microporous carbon were analyzed by synchrotron-radiation-excited soft X-ray emission spectroscopy and by analyzing its spectral features using DV-Xα molecular orbital calculations. The distances between the adsorbed molecules and the graphitic surface were estimated to be approximately 0.33 nm in both benzene- and pyridine-adsorbed systems. Both molecular orientations were also estimated to be almost parallel to the graphitic surface of microporous carbon. The electronic states of benzene and pyridine molecules adsorbed on the graphitic surface were similar to those of individual nonadsorbed free molecules. Therefore, the adsorption of benzene and pyridine molecules in the microporous carbon can be confirmed to be physisorption, and there is little charge-transfer between the adsorbed molecules and the graphitic surface.

DOI： 10.1021/jp000669s

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Benzene and pyridine molecules adsorbed in micropores of microporous carbon were directly observed by synchrotron-radiation-excited soft X-ray emission spectroscopy. There were spectral feature differences in C K X-ray emission between the adsorbate benzene and pyridine molecules, while the X-ray spectra agreed closely with their corresponding calculated C2p-DOS spectra. These results show that synchrotron-radiation-excited soft X-ray emission spectroscopy is a powerful tool for in-situ direct observation of molecular adsorbates in bulk microporous materials and for investigating their electronic structures and chemical bonding states in micropores.

DOI： 10.1016/S0008-6223(00)00031-2

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Language：Japanese   Publisher：Information Science and Technology Association, Japan  

DOI： 10.18919/jkg.45.9_466

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We have designed a label-free protein detection system on an aptamer modified graphene oxide (GO) surface fixed on a solid support. The aptasensor we studied uses fluorescence resonance energy transfer (FRET) between the dye at the terminus and the GO surface. Our system can be installed in a microfluidicdevice, that enables us accurate quantitative evaluation of the fluorescence intensity. We successfully demonstrated an enhancement in the sensitivity of an on-chip GO aptasensor by using an originally designed biomolecular probe for highly sensitive protein detection. The performance of the designed probes was examined quantitatively by using a multichannel linear-array GO aptasensor.

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (bulletin of university, research institution)   Publisher：電気通信協会  

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Language：Japanese   Publisher：電気通信協会  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)   Publisher：日本化学会  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)   Publisher：社団法人 日本分光学会  

DOI： 10.5111/bunkou.52.225

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)   Publisher：一般社団法人 表面技術協会  

DOI： 10.4139/sfj.53.902

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ラセミックな DL-イソバリン固相薄膜に，自由電子レーザーからの純粋円偏光を照射したところ、照射前には観測されなかった円二色性が観測された。Cotton 極大の符号は照射円偏光のヘリシティ符号（左 or 右まわり）により完全に逆転し，対称的な二色性スペクトルが得られた。照射後の吸収スペクトルはわずかに低エネルギー側にシフトするものの極大形状は照射前とほぼ変化がなかったことから，分子の単純な不斉分解ではなく，分子配座変化を伴う構造変化によるキラル発現であると推測される。この結果は，無生物的に生成されたラセミックな有機物が，低温の星間物質表面に吸着した状態であっても，宇宙空間に存在する円偏光への曝露により，そのヘリシティに対応した対称性方向のキラリティを発現しうることを示す。

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