Takashi Takei

Tokyo Metropolitan University, Edo, Tōkyō, Japan

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Publications (60)180 Total impact

  • Takashi Takei · Junya Suenaga · Tamao Ishida · Masatake Haruta
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    ABSTRACT: Ethanol oxidation in water by molecular oxygen on supported gold nanoparticles (NPs) has been investigated at a temperature as low as 120 °C. Among various base metal oxide supports, NiO provided the highest conversion of ethanol and good selectivity to acetic acid. Furthermore Cu doping to the NiO support to enhance the semiconductivity resulted in an improvement in the selectivity to acetic acid without the depression of the conversion of ethanol. An increase in the specific surface area of the NiO support by Cu doping enabled the deposition of smaller gold NPs and, accordingly, the improvement of the catalytic activity.
    Topics in Catalysis 04/2015; 58(4-6):295-301. DOI:10.1007/s11244-015-0370-4 · 2.37 Impact Factor
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    ABSTRACT: To detect volatile organic compounds (VOCs), optical sensors based on the localized surface-plasmon resonance (LSPR) are widely used because they are simple and inexpensive to fabricate. Although LSPR spectroscopy has been generally applied to biological molecules such as proteins and DNA, small molecular sensing has been difficult because of the very small changes induced in the refractive index. We describe a LSPR gas sensor with high and wide range sensitivity. These characteristics are obtained from the improved peak shift that results from using an Au-dot pattern coated with a porous silica film. The 400-nm-diameter, 800-nm-wide Au dots were patterned by electron beam lithography (EBL) on a quartz glass substrate. The LSPR peak of the isolated Au-dot pattern occurs at 1230 nm in the near isolated area bringing enough refractive index changes. In addition, coating the Au-dot pattern with a thin porous silica film increases the adsorption of VOCs, thereby increasing the refractive-index change. The response of the sensor to VOC vapors was measured in a dynamic-flow system. The relative intensity decreases with toluene vapor exposure but completely recovers to the initial baseline after exposure to clean air. The real-time response allows detection of toluene vapors with concentrations ranging from 1 to 26,000 ppm, and the limit of detection for toluene is calculated to be 0.4 ppm. Eighteen VOC vapors were tested and each type exhibited different calibration curves, but these differences depend on the adsorption characteristics of porous silica rather than on the refractive index of the VOCs.
    Sensors and Actuators B Chemical 06/2014; 196:1–9. DOI:10.1016/j.snb.2014.01.066 · 4.10 Impact Factor
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    ABSTRACT: Glucose oxidation by enzyme takes place in neutral aqueous solution at room temperature, producing gluconic acid in equilibrium with gluconate, while gold catalysts exhibit much higher catalytic activity but in alkali solution to produce sodium gluconate. The combination of glucose oxidase with selected gold catalysts such as Au/ZrO2 and Au/NanoDiamond led to improved catalytic performance in neutral solution at room temperature. Gold nanoparticles supported on ZrO2 decomposed hydrogen peroxide (H2O2) formed by the oxidation of glucose and depressed the damage of glucose oxidase by H2O2. In addition, Au/ZrO2 utilized H2O2 produced by the enzyme to oxidize glucose to gluconic acid. In contrast, gold nanoparticles supported on NanoDiamond were active only for the decomposition of H2O2, while the presence of NanoDiamond itself could encourage glucose oxidase for the selective oxidation.
    Applied Catalysis A General 11/2013; 468:453-458. DOI:10.1016/j.apcata.2013.09.023 · 3.94 Impact Factor
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    ABSTRACT: A new filter-type Au/ZrO2 catalyst was fabricated by using poly(ethylene terephthalate) (PET) nonwoven fabric as a support. Owing to its flexibility, thinness, lightness, and easy handling, this form of a catalyst is advantageous in practical use for air purification over the existing catalyst forms such as pellets and honeycombs. Zirconium oxide fine particles were first deposited on PET nonwoven fabric in the presence of 3-methacryloxypropyltrimethoxysilane to form thin layer like a fish scale and then gold nanoparticles (NPs) were deposited on ZrO2 fine particles by deposition–precipitation method. The catalyst was active enough at room temperature and oxidized 1000 ppm CO and removed 140 ppm HCHO in air. The catalytic activity of Au/ZrO2 supported on PET nonwoven fabric was also measured under similar conditions to those for practical air purification in offices and houses for the oxidation of 0.5 ppm HCHO and high HCHO conversion (close to 100%) was maintained up to 136 h.
    Applied Catalysis B Environmental 05/2013; s 134–135:130–135. DOI:10.1016/j.apcatb.2012.12.018 · 7.44 Impact Factor
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    ABSTRACT: Shape-controlled hollow silica nanoparticles have been successfully synthesized by an inorganic particle template method, which involves sol–gel silica coating over surfaces of the template and followed by acid-dissolution removal of the template. This work demonstrates shape control of the hollow particle using calcium carbonate as the template with a variety of shapes such as cubic, rough-surfaced spherical and rod-like particles. Inner size and shape of hollow silica nanoparticles synthesized were exactly reflected to outer size and shape of template used, and existence of micropores in the silica shell wall was verified by nitrogen gas adsorption analysis.
    Advanced Powder Technology 09/2012; 23(5-5):562-565. DOI:10.1016/j.apt.2011.06.002 · 2.64 Impact Factor
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    ABSTRACT: Titanosilicalite-1 (TS-1) was first treated with aqueous KOH solution to introduce surface defects. Then KOH-treated TS-1 (TS-1K) was further treated with aqueous HNO3 solution to remove residual potassium. Then, Au was deposited by solid grinding on this support free of K (TS-1KH) as 1.6 nm clusters, which could be stabilized by surface detects. Finally, Au/TS-1KH was modified by impregnating potassium salts, alkali hydroxides or alkaline earth metal acetates. XRD and UV–vis spectra indicated that the crystalline MFI structure and 4-fold coordinated Ti4+ sites of TS-1 were maintained even after different treatments. HAADF-STEM showed that after the modification of Au/TS-1-KH the mean diameter of Au clusters increased only slightly from 1.6 nm to 1.8 nm. In propene epoxidation with molecular O2 and H2O, Au/TS-1KH promoted by basic potassium salts (CH3COO−, CO32− and PO43−) or hydroxides of Na, K, Rb and Cs could produce PO with the selectivity of 12–45%, while Au/TS-1KH combined with neutral potassium salts (KCl, KNO3 and K2SO4), LiOH or alkaline earth metal acetates could not produce PO.
    Applied Catalysis A General 09/2012; s 435–436:115–122. DOI:10.1016/j.apcata.2012.05.040 · 3.94 Impact Factor
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    ABSTRACT: Transition metal oxides (MnO2, Co3O4, and NiO) are catalytically active for the ammoxidation of alcohols to nitriles. In particular, MnO2 exhibited remarkably high catalytic activity and selectivity for the ammoxidation of alcohols to produce nitriles. Benzyl alcohol could also be directly converted to benzonitrile by MnO2 catalyst by the one-pot ammoxidation and the hydration with water which was formed by the first ammoxidation step. The deposition of gold nanoparticles (Au NPs) onto MnO2 did not enhance the ammoxidation of benzyl alcohol but promoted the hydration of benzonitrile to produce benzamide with high selectivity. In contrast, Au NPs supported on Al2O3, CuO, and CeO2 catalyzed the ammoxidation of benzyl alcohol, whereas these metal oxides themselves were inactive for the ammoxidation or showed low catalytic activity. These results have demonstrated that gold is intrinsically active as a catalyst for the ammoxidation of alcohols.
    Applied Catalysis A General 05/2012; s 425–426:85–90. DOI:10.1016/j.apcata.2012.03.006 · 3.94 Impact Factor
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    ABSTRACT: Gold nanoparticles supported on metal oxides catalyzed the N-alkylation of aniline with benzyl alcohol to produce secondary amine under the equimolar amounts of substrates without additives under mild conditions. Selectivity to secondary amine was changed by the kinds of supports. Gold on ZrO2 exhibited the highest catalytic performance and achieved 94% selectivity to secondary amine. Surface hydroxyl groups of ZrO2 played important roles in the deprotonation of alcohol in the alcohol dehydrogenation step, as the adsorption sites of aniline, and as a proton source in the hydrogen transfer step.
    Applied Catalysis A General 01/2012; s 413–414:261–266. DOI:10.1016/j.apcata.2011.11.017 · 3.94 Impact Factor
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    ABSTRACT: Gold can be deposited as nanoparticles (NPs) with diameters of 2-5. nm and clusters with diameters less than 2. nm on a variety of materials such as oxides, carbides, and sulfides of transition metals, carbons, and organic polymers. Such supported gold NPs and clusters exhibit surprisingly high catalytic activities for many reactions, with both gas- and liquid-phase reactants, in particular, at temperatures below 573. K. Until now, more than 10 techniques have been developed for depositing gold as NPs and clusters. The atomic scale structures of supported NPs and clusters have been extensively and intensively investigated with a high-resolution transmission electron microscopy.The mechanisms of catalysis by supported gold NPs have recently been elucidated by using real powder catalysts and model single-crystal catalysts for the low-temperature oxidation of CO. Another simple reaction that has recently been investigated is dihydrogen dissociation, for which gold NP catalysts are still poorly active. Both of these reactions have been demonstrated to take place at perimeter interfaces around the gold NPs. This result means that there is a great chance for gold to exhibit high catalytic activity for hydrogenation reactions by an appropriate choice of metal oxide supports and by minimizing the diameters of gold particles. The catalytic nature of gold clusters has also been investigated theoretically in relation to the effect of cluster size and the influence of organic ligands and polymers.The catalytic performance of gold NPs and clusters has been explored extensively for reactions of both gases and liquids. Supported gold catalysts are useful for air cleaning at room temperature, and they are valuable for green production of bulk and fine chemicals. Supported gold clusters are expected to open new doors for simple chemistry for the selective manufacture of needed products. Size and structure specificity are expected to present opportunities for selective conversions. It is recommended that researchers explore the magic numbers and structures of gold and suitable support materials for selected target reactions.
    01/2012: pages 1-126;
  • Takashi Takei · Norihiko Iguchi · Masatake Haruta
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    ABSTRACT: Twenty three kinds of metal oxides were screened as supports for Aunanoparticles (Au NPs) in the gas phase oxidation of ethanol. Mild oxidation to acetaldehyde, which is economically preferable, is catalyzed by Au NPs deposited on catalytically inert metal oxides, in particular, strongly acidic MoO3 or weakly basic La2O3. Deep oxidation to acetic acid takes place over Au NPs deposited on n-type semiconductive metal oxides such as ZnO and V2O5, which exhibit a little catalytic activity for ethanol oxidation at 200 °C. Complete oxidation to CO2 and H2O preferentially takes place over p-type semiconductive metal oxides such as MnO2 and Co3O4, and CeO2 which has oxygen-storage and discharge capability. These metal oxides show catalytic activity for ethanol oxidation even at 100 °C producing mainly acetaldehyde, and their catalytic activity is noticeably enhanced in the conversion of ethanol and the selectivity to CO2 by the deposition of Au NPs. The wide range of product tunability can be explained by the adsorption structures of ethanol and by the reactivities of oxygen species on the metal oxide supports.
    New Journal of Chemistry 09/2011; 35(10):2227-2233. DOI:10.1039/C1NJ20297A · 3.09 Impact Factor
  • Takashi Takei · Norihiko Iguchi · Masatake Haruta
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    ABSTRACT: Following gradual shift of primary resources from fossil towards renewable ones in chemical industry, biomass based ethanol has been attracting growing interests as a fuel to replace gasoline and as a chemical feed stock to replace ethylene. This paper reviews major work reported in the last 10years for the production of acetaldehyde, acetic acid, and other related compounds from ethanol. At present acetic acid can be industrially produced more economically from methanol than from ethylene, the production of acetic acid from ethanol is not profitable. Acetaldehyde, which is more expensive than ethanol, can be selectively produced in gas phase by dehydrogenation over supported Cu catalysts and by oxidation with O2 over V and Mo based oxides. It is noteworthy that gold nanoparticles deposited on basic and acidic metal oxides are highly selective to acetaldehyde by oxidation with O2. Acetic acid can be produced in water solvent over Au catalysts supported on MgAl2O4 or on Cu doped NiO, while in gas phase over Mo–V–Nb mixed oxides combined with TiO2 colloids. KeywordsEthanol–Acetaldehyde–Acetic acid–Ethyl acetate–Ethylene oxide–Gold catalysts–Copper catalysts–Mo or V based oxides
    Catalysis Surveys from Asia 06/2011; 15(2):80-88. DOI:10.1007/s10563-011-9112-1 · 3.28 Impact Factor
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    ABSTRACT: Gold was deposited on alkaline-treated TS-1 (TS-1-Na1) to prepare Au/TS-1-Na1(DP) by deposition–precipitation (DP) and Au/TS-1-Na1(SG) by solid grinding (SG). 129Xe NMR technique has detected that tiny Au clusters have been incorporated into the microporous channels of Au/TS-1-Na1(DP), while they were absent inside the microporous channels of Au/TS-1-Na1(SG). On the other hand, HAADF-STEM observation showed that the amount of Au clusters (1.0–2.0nm) over the exterior surfaces was much larger in Au/TS-1-Na1(SG) than in Au/TS-1-Na1(DP). In propene epoxidation with O2 and H2, Au/TS-1-Na1(SG) exhibited much higher PO formation rate (127gPOkgcat-1h−1) than Au/TS-1-Na1(DP) (74gPOkgcat-1h−1), indicating that Au clusters with diameters of 1.0–2.0nm are more active for PO synthesis than tiny Au clusters incorporated inside the microporous channels.
    Journal of Catalysis 02/2011; 278(1):8-15. DOI:10.1016/j.jcat.2010.11.012 · 6.92 Impact Factor
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    ABSTRACT: Trapping gold! A novel porous metal-organic framework (MOF) with an unprecedented hexagonal (4,8)-connected topology has been assembled and characterized. By employing the resultant MOF as a host, for the first time, ultrafine Au clusters with an average atom number of 2.5 were successfully prepared and incorporated into the pores of the MOF through a simple surfactant-free method (see graphic).
    Chemistry - A European Journal 01/2011; 17(1):78-81. DOI:10.1002/chem.201002088 · 5.73 Impact Factor
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    ABSTRACT: The influence of the preparation methods (IP:impregnation, DP:deposition-precipitation, SG:solid grinding) for Pt/CeO2 and Au/CeO2 was studied on the size and shape of metal particles and the catalytic activity for CO oxidation. The fine structures of these catalysts were examined by HR-TEM and were correlated to their catalytic properties. The size of metal particles depended on the preparation methods and increased in the order of DP<SG<IP. Gold on CeO2 was much more active than Pt/CeO2, but the activation energy were similar (in the range of 46∼56kJ/mol). The turnover frequency based on surface exposed metal atom sharply increased with a decrease in the mean diameter of Au particles, whereas it decreased in the case of Pt/CeO2.
    Studies in surface science and catalysis 12/2010; 175:843-847. DOI:10.1016/S0167-2991(10)75174-0
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    ABSTRACT: A AuLa2(OH)9 coprecipitate calcined in air at temperatures below 450K showed surprisingly high catalytic activity for CO oxidation, 100% conversion at a temperature as low as 193K, when it was reduced in a N2 stream containing H2 or CO at 373K. The reduction treatment transformed Au(OH)3 species interacting with the La(OH)3 support into Au0 clusters smaller than 1.8nm in diameters.
    Chemical Physics Letters 06/2010; 493(4):207-211. DOI:10.1016/j.cplett.2010.05.024 · 1.90 Impact Factor
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    ABSTRACT: Gold could be deposited as clusters smaller than 2.0 nm in diameter on TS-1 by solid grinding (SG) of the support with dimethyl Au(III) acetylacetonate after TS-1 was pretreated in aqueous solution of alkaline metal hydroxides. While in C3H6 epoxidation with O2 and H2 mixture Au nanoparticles larger than 2.0 nm deposited on TS-1 without alkaline treatment gave a very low PO formation rate of 11 gPO kgcat.−1 h−1, Au clusters on alkaline treated TS-1 presented a greatly enhanced rate as high as 137 gPO kgcat.−1 h−1, which was comparable to the best data reported so far. In addition, very high H2 efficiency reaching 47% could be obtained by gold clusters on alkaline treated TS-1.
    Applied Catalysis B Environmental 04/2010; 95(3-4):430-438. DOI:10.1016/j.apcatb.2010.01.023 · 7.44 Impact Factor
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    ABSTRACT: Heterogeneous catalysts that can work at ambient temperature are useful for in-door air quality control, pure gas production for fuel cells and semiconductors, gas sensing, and so forth. Deposition of gold nanoparticles on base metal oxide is known to provide highly active catalysts for CO oxidation at temperatures below room temperature. Here we report that some select base metal oxides such as Co3O4, MnO2, and NiO are intrinsically active catalysts for CO oxidation below 50°C when pretreated at moderate temperature between 150 and 250°C in a stream of non-reducing dry gases, for example, dry air, CO in air, or N2. These metal oxides are p-type semiconductors and form surface excess oxygen adsorbed at oxygen vacancies which are created by the above pretreatments.
    Journal of Catalysis 10/2009; 267(2):121-128. DOI:10.1016/j.jcat.2009.08.003 · 6.92 Impact Factor
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    ABSTRACT: Slze matters: Gold clusters (<2.0 nm), but not gold nanoparticles, deposited on alkaline-treated titanosilicalite-1 allow O2 and H 2O to react to give hydroperoxides (-OOH). These transfer to neighboring Ti sites to form Ti-OOH (see scheme), which is responsible for propene epoxidation to give propene epoxide (PO).
    Angewandte Chemie International Edition 10/2009; 48(42):7862-6. DOI:10.1002/anie.200903011 · 11.26 Impact Factor
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    ABSTRACT: Not all that glitters... The activity of supported gold nanoparticles depends on the method used for their preparation. Gold clusters of about 2 nm in diameter were deposited on nonreducible metal oxides and carbon materials by solid grinding of a volatile organogold complex in a ball mill and subsequent calcination (see scheme). Au/ZrO2 and Au/Al2O3 prepared in this way were extremely efficient catalysts for the aerobic oxidation of glucose. (Chemical Equation Presented).
    Angewandte Chemie International Edition 11/2008; 47(48):9265-8. DOI:10.1002/anie.200802845 · 11.26 Impact Factor
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    ABSTRACT: A Pt-Ru nanoparticle catalyst was prepared using mesoporous carbon, CMK-3, as a support, and the catalytic activity was compared to that on Ketjen carbon black, KB. The DMFC performances of MEA prepared with these catalysts were also measured and compared with each other. The catalysts deposited on CMK-3, Pt-Ru/CMK-3, had a narrow size distribution around 2.5nm and highly distributed on the surface of the support. Pt-Ru/CMK-3 showed a higher mass activity for methanol oxidation based on a cyclic voltammogram, but a lower DMFC performance than that of Pt-Ru/KB. It was considered that the catalyst layer with CMK-3 had a lower electric conductivity and/or unfavorable microstructure to prepare a large number of active reaction sites in the layer.
    02/2007; 75(2):172-174. DOI:10.5796/electrochemistry.75.172

Publication Stats

805 Citations
180.00 Total Impact Points


  • 1990–2014
    • Tokyo Metropolitan University
      • • Department of Applied Chemistry
      • • Department of Chemistry
      Edo, Tōkyō, Japan
  • 2010–2013
    • Japan Science and Technology Agency (JST)
      Edo, Tōkyō, Japan