Seiji Yamazoe

Small, negatively charged gold clusters isolated in vacuum can oxidize CO via electron-transfer-mediated activation of O2. This suggests that Au clusters can act as aerobic oxidation catalysts in the real world when their structure parameters satisfy given required conditions. However, there is a technical challenge for the development of Au cluster oxidation catalysts; the structural parameters of the Au clusters, such as size and composition, must be precisely controlled because the intrinsic

We analyzed the X-ray absorption fine structure (XAFS) spectra of W L1- and L3-edges in order to determine the structure of various W species on TiO2. Two 2p → 5d transitions were observed in the second derivative of the W L3-edge X-ray absorption near-edge structure (XANES) spectra of all samples containing W (WO3, Na2WO4, Cr2WO6, Ba2NiWO6, (NH4)10W12O41·5H2O, Sc2W3O12, H3PW12O40·13H2O, and TiO2-loaded WO3 samples). These two transitions can be assigned to 5d orbitals split by the ligand field.

Unique thermal properties of metal clusters are believed to originate from the hierarchy of the bonding. However, an atomic-level understanding of how the bond stiffnesses are affected by the atomic packing of a metal cluster and the interfacial structure with the surrounding environment has not been attained to date. Here we elucidate the hierarchy in the bond stiffness in thiolate-protected, icosahedral-based gold clusters Au25(SC2H4Ph)18, Au38(SC2H4Ph)24 and Au144(SC2H4Ph)60 by analysing Au L

The preferential locations of Ag and Cu atoms in the initial stage of doping into [Au25(SC2H4Ph)18]− were studied by X-ray absorption spectroscopy and density functional theory computations. The extended X-ray absorption fine structure (EXAFS) spectra of [Au23.8Ag1.2(SC2H4Ph)18]− at the Ag K-edge were reproduced using a model structure in which the Ag dopant occupied a surface site in the icosahedral Au13 core that was computationally the most stable site. In contrast, the Cu K-edge EXAFS spectr

Various studies on functionalization of water-splitting photocatalysts have been performed toward their practical usage. Control of the cocatalyst has been investigated, and recently, in addition to particle-size control, alloying has been extensively used to achieve this goal. It is essential to investigate photocatalysts with precisely controlled cocatalysts to obtain a detailed understanding of the effect of heteroatom doping of the cocatalyst on the photocatalytic activity and thereby establ

Selective catalytic oxidation of NH3 to give N2 under UV irradiation (photo-SCO) takes place at a low temperature over the TiO2 catalyst. An active site for the photo-SCO is a Lewis acid site on TiO2, and adsorption of NH3 to the Lewis acid site is the first step in the photo-SCO. The adsorbed NH3 on the Lewis acid site is activated under UV irradiation to generate NH2 radical and Ti−OH (Brønsted acid site). The formed NH2 radical reacts with an oxygen anion radical species formed under UV irrad

The fluxional nature of small gold clusters has been exemplified by reversible isomerization between [Au₉(PPh₃)₈]³⁺ with a crown motif (Au₉(C)) and that with a butterfly motif (Au₉(B)) induced by association and dissociation with compact counteranions (NO₃^-, Cl^-). However, structural isomerization was suppressed by substitution of the central Au atom of the Au₉ core in [Au₉(PP

The formation of a NH2 radical on TiO2 under photoirradiation was confirmed by electron paramagnetic resonance spectroscopy. Photogenerated holes and electrons on TiO2 are trapped by adsorbed NH3 and Ti4+ species, respectively, to form the NH2 radical and Ti3+ species. The half-life of the NH2 radical determined by the Arrhenius equation was found to be 1.4 min for the photoassisted selective catalytic reduction (photo-SCR) of NO with NH3. The NH2 radical was quenched just after the introduction

The development of novel catalysts based on metal clusters requires a rational design principle as well as atomically precise synthetic methods. Toward this goal, we have developed a method to precisely and independently control the size, composition, and surface modification of heterogeneous gold clusters by calcination of the ligand-protected Au clusters on carbon supports. We studied the effects of these structural parameters using benzyl alcohol oxidation as a test reaction. Unexpectedly, Au

Brønsted and Lewis base catalysis of hexametalate clusters of group 5 metals [M(V)6O19]8– (M(V) = Ta, Nb) and group 6 metals [M(VI)6O19]2– (M(VI) = Mo, W) was studied using Knoevenagel condensation and CO2 fixation reaction, respectively, as test reactions. It was found from mass spectrometry and elemental analysis that tetrabutylammonium salts of [M(V)6O19]8– were partially protonated to form [H4M(V)6O19]4– under ambient conditions, whereas those of [M(VI)6O19]2– were not. Base catalytic activi

Orientated NaNbO3 (NN) films were grown on SrRuO3/(001)SrTiO3 [SRO/(001)STO], SRO/(110)STO, and SRO/(111)STO substrates by pulsed laser deposition. Scanning electron microscopy images showed that the surface morphologies of the NN/SRO/(001)STO, NN/SRO/(110)STO, and NN/SRO/(111)STO took the form of a stepped structure, a striped pattern, and trigonal pyramidal-like structures, respectively. The dielectric and ferroelectric properties of the films were characterized. The NN/SRO/(110)STO film showe