Hiroyuki Sugimura

Kyoto University, Kioto, Kyōto, Japan

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Publications (219)384.32 Total impact

  • Takashi Ichii, Hiroyuki Sugimura
    Microscopy (Oxford, England). 11/2014; 63 Suppl 1:i10-i11.
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    ABSTRACT: The creation of a model that explains the dependency of the voltammetric characteristics of ferrocene-terminated Si (Si-Fc) samples on the type of substrate (n- or p-type) would be helpful in understanding the electronic characteristics of these materials. To explain the dependency, Si-Fc samples are treated like diodes. As diodes, the samples may allow charge flow in a certain direction while inhibiting the opposite flow. The treatment of a sample as a diode is done to facilitate analysis of charge flow within the sample, thus enabling easy prediction of its electrochemical characteristics. Likewise, the trend of the anodic peak potential versus light intensity plot (of the samples with n-type substrate) is also associated with the sample’s diode characteristics. Our proposed model opens many scientific possibilities, especially in relating the voltammetric characteristics of electroactive molecules on a Si surface with the properties of a diode (e.g., open-circuit voltage).
    ChemElectroChem. 09/2014;
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    Yudi Tu, Takashi Ichii, Om Prakash Khatri, Hiroyuki Sugimura
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    ABSTRACT: A dry photoprocess for converting graphene oxide (GO) to reduced GO (rGO) by vacuum–ultraviolet (VUV) irradiation is reported. The rapid reduction of GO was achieved by irradiating a GO sheet in vacuum with 172 nm VUV light at a low power density of 10 mWcm−2. This VUV reduction photochemistry was successfully applied to photolithography by which rGO lines could be drawn on a GO microsheet at a sub-micrometer resolution. This method will be promising for the fabrication of graphene-based microdevices.
    Applied Physics Express 07/2014; 7(7):075101. · 2.73 Impact Factor
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    ABSTRACT: The photochemical grafting of methyl groups onto an n-type Si(111) substrate was successfully achieved using a Grignard reagent. The preparation involved illuminating a hydrogen-terminated Si(111) that was immersed in a CH3MgBr-THF solution. The success was attributed to the ability of the n-type hydrogenated substrate to produce holes on its surface when illuminated. The rate of grafting methyl groups onto the silicon surface was higher when a larger illumination intensity or when a substrate with lower dopant concentration was used. In addition, the methylated layer has an atomically flat structure, has a hydrophobic surface, and has electron affinity that was lower than the bulk Si.
    Journal of Colloid and Interface Science 08/2013; · 3.55 Impact Factor
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    ABSTRACT: A new integration technique of Deoxyribonucleic acid (DNA) origami as an excellent platform to arrange various nanomaterials such as metallic nanoparticles, carbon nanotubes and proteins and so on with nanometer scale resolution into MEMS utilizing DNA hybridization of a complementary pair of single-strand DNAs (ssDNAs) was demonstrated. A contact-mode atomic force microscopy (AFM) based lithography was adopted to form ssDNA modified patterns into an organic thin film with 30 nm resolution on a silicon substrate. A newly designed DNA origami (30 nm × 150 nm) with ssDNA as sticky ends was successfully fixed at specific positions of the substrate by DNA hybridization.
    Micro Electro Mechanical Systems (MEMS), 2013 IEEE 26th International Conference on; 01/2013
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    ABSTRACT: It is essential to immobilize gold nanoparticles (AuNPs) firmly onto a certain substrate in a closely packed manner to apply plasmonic functions of AuNP in photonic/electronic devices. AuNP-Si systems are of particular interest for the integration of plasmonics to semiconductor electronics. Here we report on the arrangement of AuNPs into a 2-D array that was covalently bonded to a Si substrate without surface oxide. This process was achieved by simply irradiating visible light to a hydogen-terminated Si substrate immersed in a solution of AuNPs covered with a self-assembled monolayer (SAM) of 11-mercaptoundecene (MUD). These MUD-AuNPs were attached to the substrate by forming Si–C bonds as a result of the photochemical reaction between Si–H groups on the substrate and vinyl groups of the MUD-SAMs. The reaction proceeded most effectively at a wavelength band around 520 nm adjusted to the plasmonic resonance peak of the MUD-AuNPs(20 nm in diameter)/toluene solution centered at 535 nm, demonstrating that the photochemical reaction was assisted by localized surface plasmon, which allowed the AuNPs to be photon collectors.
    The Journal of Physical Chemistry C. 09/2012; 117(6):2480–2485.
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    ABSTRACT: Frequency modulation atomic force microscopy (FM-AFM) imaging in ionic liquids (ILs) were carried out. A quartz tuning fork sensor with a sharpened tungsten tip was used as a force sensor instead of a Si cantilever. Only the tip apex was immersed in ILs and the quality factor of the sensors was kept more than 100 in spite of the high viscosity of ILs. Atomic-resolution topographic imaging was successfully achieved in an IL as well as in an aqueous solution. In addition, frequency shift versus tip-to-sample distance curves were obtained and the structures of local solvation layers were studied.
    Japanese Journal of Applied Physics 08/2012; 51(8). · 1.07 Impact Factor
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    ABSTRACT: UV photon induced assembly of ω-alkenyl terminated gold nanoparticles (AuNPs) on pre-defined sites of crystalline silicon surface through covalent interaction is demonstrated. Highly ordered and stable hexadecyl monolayer on oxide free silicon surface is used to construct the photopattern and then the linear patterns of hydrogen-terminated sites were effectively used to assemble AuNPs by UV induced hydrosilylation. This approach is entirely based on oxide free interfaces, where both robust organic monolayer and AuNPs are assembled in a linear fashion. The developed strategy promises immense potential to miniaturize silicon based devices for technological applications, where electron coupling between the nanoparticles and the silicon surface is very significant. This work further paving the new direction to immobilize various types of nanoparticles in different architecture on oxide free crystalline silicon surface to exploit their utilization in technological applications.
    Journal of Materials Chemistry 07/2012; 22(32):16546-16551. · 5.97 Impact Factor
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    ABSTRACT: Synthesis of ω-alkenyl-terminated silver nanoparticles (AgNPs) and then their immobilization on a hydrogen-terminated silicon surface in two-dimensional arrangement through covalent interaction are demonstrated. The thermal-induced hydrosilylation at mild conditions facilitate nanoparticles assembly through interaction between terminal alkenyl (CH(2)=CH-) groups of AgNPs and hydrogen-terminated silicon surface. The assembly of AgNPs on a silicon surface is characterized by FESEM and XPS. Adequate coating of 10-undecene-1-thiol (UDT) on AgNPs and mild temperature hydrosilylation impede the fusion or aggregation of nanoparticles, while they immobilized on a silicon surface, which is very crucial to preserve the discrete entities of nanoparticles. This elegant and facile approach provides stable monolayer of AgNPs with very good coverage area and promises potential to fabricate electronic devices and solar cells, where nanoparticles needs to be directly attached to the silicon surface without an interfacial oxide thin film.
    Journal of Colloid and Interface Science 06/2012; 382(1):22-7. · 3.55 Impact Factor
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    ABSTRACT: We have fabricated gold nanoparticle (AuNP) arrays on indium-tin oxide (ITO) substrates in a nearly one-dimensional fashion. AuNPs were site-selectively immobilized on ITO of which the surface had been patterned by a nanolithography process based on scanning probe microscopy. The fabricated nanoscale lines covered with aminosilane self-assembled monolayer served as chemisorption sites for citrate-stabilized AuNPs of 20 nm in diameter, accordingly, AuNP nanolines with a thickness of single nanoparticle diameter were spontaneously assembled on the lines. In this 1D array, the AuNPs were almost separated from each other due to the electrostatic repulsion between their negatively charged surface layers. Furthermore, a reorganization process of the immobilized AuNP arrays has been successfully demonstrated by replacing each AuNP's surface layer from citric acid to dodecanethiol. By this process, the AuNPs lost their electrostatic repulsion and became hydrophobic so as to be attracted to each other through hydrophobic interaction, resulting in reorganization of the AuNP array. By repeating the deposition and reorganization cycle, AuNPs were more densely packed. The optical absorption peak of the arrays due to their plasmonic resonance was found to shift from 526 to 590 nm in wavelength with repeating cycles, indicating that the resonance manner was changed from the single nanoparticle mode to the multiple particle mode with interparticle coupling.
    Langmuir 05/2012; 28(20):7579-84. · 4.38 Impact Factor
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    ABSTRACT: Highly controlled arrays of gold nanoparticles (AuNPs) were fabricated on optically transparent indium tin oxide (ITO) substrates by combining atomic force microscope (AFM) lithography and surface modification using self-assembled monolayers (SAMs). The nanopatterns of methyl and amino groups were fabricated on ITO substrates and AuNPs were assembled just on the amino-terminated nanopatterns, which is based on the different affinities of the AuNPs for the functional groups. The site selectivity was intensively improved by dehydration and repairing defects in a long alkylsilane SAM with short alkylsilane molecules.
    Applied Physics Express 02/2012; 5(2):5202-. · 2.73 Impact Factor
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    ABSTRACT: The molecular density of an aminosilane self-assembled monolayer formed from N-(2-aminoethyl)-3-aminopropyltriethoxysilane (AEAPS) by a vapor phase method has been estimated to be about 3 AEAPS molecules per nm(2) based on chemical labeling, optical absorption spectroscopy and X-ray photoelectron spectroscopy.
    Chemical Communications 08/2011; 47(31):8841-3. · 6.38 Impact Factor
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    ABSTRACT: Electrochemically active self-assembled monolayers (SAM) have been successfully fabricated with atomic-scale uniformity on a silicon (Si)(111) surface by immobilizing vinylferrocene (VFC) molecules through Si-C covalent bonds. The reaction of VFC with the hydrogen-terminated Si (H-Si)(111) surface was photochemically promoted by irradiation of visible light on a H-Si(111) substrate immersed in n-decane solution of VFC. We found that aggregation and polymerization of VFC was avoided when n-decane was used as a solvent. Voltammetric quantification revealed that the surface density of ferrocenyl groups was 1.4×10(-10) mol cm(-2), i.e., 11% in substitution rate of Si-H bond. VFC-SAMs were then formed by the optimized preparation method on n-type and p-type Si wafers. VFC-SAM on n-type Si showed positive photo-responsivity, while VFC-SAM on p-type Si showed negative photo-responsivity.
    Journal of Colloid and Interface Science 06/2011; 361(1):259-69. · 3.55 Impact Factor
  • Kuniaki Murase, Akira Ito, Takashi Ichii, Hiroyuki Sugimura
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    ABSTRACT: A novel metallization of non-conductive epoxy substrate with Cu-Sn “speculum alloy,” or “white bronze,” was performed through successive electrochemical processes: (i) conventional electroless deposition of pure Cu layer and (ii) subsequent electrochemical alloying of the resulting pure Cu layer with Sn using an ionic liquid bath at 150°C, a medium-low temperature. Availability of the Sn quasi-reference electrode for the alloying was verified, and the resulting compact and adhesive Cu-Sn layers, composed of Cu6Sn5 and/or Cu3Sn intermetallic phases, were examined as an alternative to nickel plating. The abundance of the two intermetallic phases was found to be dependent on the alloying potential and duration, and was discussed in terms of alloy formation thermodynamics of the Cu-Sn system.
    Journal of The Electrochemical Society. 05/2011; 158(6):D335-D341.
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    ABSTRACT: Nanostructures consisting of concentric Au circles with a nm-scale line thickness have been fabricated on silicon (Si) substrates based on electroless plating and by the use of scanning probe microscope as a lithographic tool. First, a micro-template was fabricated on a hexadecyl self-assembled monolayer (HD-SAM) covalently bonded to a Si(111) substrate by scanning probe anodization lithography in which the HD-SAM was locally degraded and the substrate Si was anodized along a trace of an conductive AFM-tip biased negatively to the grounded Si substrate. Anodic Si oxide formed by this local anodization process was then etched with HF in order to expose the Si surface under the anodic oxide layer. Consequently, a Si nanopattern surrounded with the HD-SAM identical to the anodic oxide pattern was formed. This Si nanopattern served as a template for fabricating a Au nanostructure by means of electroless plating. Due to the galvanic displacement of surface Si atoms with Au complex ions in a plating bath, Au started to nucleate on the exposed Si surface, while no nuclei was formed on the surrounding HD-SAM. Consequently, a Au nanostructure was formed through further Au deposition on the Au nuclei. The fabricated Au nanostructures are promising for applications emerging plasmonic functions.
    Journal of Photochemistry and Photobiology A-chemistry - J PHOTOCHEM PHOTOBIOL A-CHEM. 01/2011; 221(2):209-213.
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    ABSTRACT: Redox behaviors of binary self-assembled monolayers (SAMs) consisting of ferrocenyl- and methyl-terminated alkanethiols on gold were investigated in three different ionic liquids (ILs) and were compared with the behaviors in an aqueous HClO4 solution. A set of cyclic voltammograms showed that, when the surface density of ferrocenyl-groups was relatively high, the shape of redox waves (e.g. peak area and peak broadening towards positive potential) for the ferrocenyl-groups was strongly affected by the anion size of the ILs, suggesting that the compensation of surface positive charge emerged when oxidized to ferrocenium state is sterically-hindered in the case of large anions like bis[(trifluoromethyl)sulfonyl]amide (TFSA−). This is supported by the fact that the anion-size effect disappeared if the density of ferrocenyl-groups was diluted. A potential-step chronocoulometry was concomitantly employed to estimate the net faradaic charge of the redox. The redox behaviors in mixed ILs containing two different sized anions also gave clear evidence that smaller anions, e.g. BF4- ions, have a greater tendency to make ion pairs with ferrocenium moieties.
    01/2010;
  • Journal of The Electrochemical Society 01/2010; 160(9). · 2.59 Impact Factor
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    ABSTRACT: We have prepared alkanethiol monolayers, directly attached to a silicon substrate, by immersing hydrogen-terminated silicon in 1-hexadecanethiol solution at 150 °C. The evidence for the 1-hexadecanethiol monolayer formation was obtained and the resulting monolayers were compared with the monolayers formed from 1-hexadecanol using water contact angle measurements, X-ray photoelectron spectroscopy, ellipsometry, and atomic force microscopy. The densities of the alkyl chains in the 1-hexadecanethiol monolayers were lower than those of the 1-hexadecanol monolayer. The durability of these monolayers to 5% HF aqueous solution was also examined. The 1-hexadecanethiol monolayer is found to be less durable than the 1-hexadecanol monolayer.
    Japanese Journal of Applied Physics 01/2010; 49(1). · 1.07 Impact Factor
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    ABSTRACT: The functionalisation process of carbon nanotubes (CNTs) is required as a primary step in fabricating CNTs-supported composites. In this study, multiwall carbon nanotubes (MWNTs) were treated under N2 atmospheric pressure plasma in order to functionalise their sidewalls with nitrogen-containing and other functional groups. The surface-treated MWNTs with –NO, –NH2 and other functional groups grafted on their sidewalls were analysed by X-ray photoelectron spectroscopy (XPS). In addition, a certain amount of structural disorder generated by the continuous decoration of functional groups on the MWNT sidewalls was investigated by Raman spectroscopy and high-resolution transmission electron microscopy (TEM). The functional groups introduced by N2 atmospheric pressure plasma were used as the chemical reaction sites for fabricating the Pt/MWNT nanocomposites. The deposition manner of Pt nanoparticles from their precursor ions (PtCl2–6) was positively correlated with the proportion of the surface functional groups. The plasma-treated MWNT-supported platinum catalysts exhibited higher electrochemical activity for hydrogen adsorption/desorption and methanol oxidation than did the catalysts prepared with MWNTs treated by HNO3/H2SO4. These results were due to the uniformly deposited Pt nanoparticles on the MWNTs caused by the strong interactions between the Pt precursors and the functional groups formed by N2 atmospheric pressure plasma.
    Fuel Cells 11/2009; 10(2):221 - 226. · 1.55 Impact Factor
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    ABSTRACT: The redox behavior of the binary self-assembled monolayers (SAMs) of 11-ferrocenyl-1-undecanethiol and 1-undecanthiol on gold substrate was investigated in an ionic liquid (IL), trimethyl-n-hexylammonium bis[(trifluoromethyl)sulfonyl]amide (TMHA-Tf2N) and HClO4 aqueous solution. It was found that the total amount of charge for the redox of ferrocenyl groups in the ionic liquid is about 70% of that in the HClO4 solution, indicating that less number of ferrocenyl groups are involved in the redox in the ionic liquid. A set of impedance measurements indicated that the electron transfer rate between the SAMs and the substrate is lower in the ionic liquid than that in aqueous solution, suggesting a slow and incomplete reconstruction of TMHA-Tf2N ions at the SAMs/ionic liquid surface.
    ECS Transactions 08/2009; 16(49).

Publication Stats

1k Citations
384.32 Total Impact Points

Institutions

  • 2004–2014
    • Kyoto University
      • Department of Materials Science and Engineering
      Kioto, Kyōto, Japan
    • Kanagawa Academy of Science and Technology
      Kawasaki Si, Kanagawa, Japan
  • 2012
    • Indian Institute of Petroleum (IIP)
      Dehra, Uttarakhand, India
  • 1998–2006
    • Nagoya University
      • • Center for Integrated Research in Science and Engineering (CIRSE)
      • • Graduate School of Engineering
      Nagoya-shi, Aichi-ken, Japan
  • 1993
    • Tohoku University
      Japan