Trapping sites in single atom (SA) catalysts are critical to the stabilization and reactivity of isolated atoms. Herein, we show that anchoring of Pt SAs on TiO 2 nanosheets is strongly aided by lattice incorporated fluorine species. Tailoring the speciation of fluorine on TiO 2 nanosheets is a key factor for uniform and stable dispersion of the Pt SAs and high efficiency in Pt SA co-catalyzed photocatalytic H 2 production. Fluorinestabilized uniformly dispersed Pt SAs on the (001) surface of TiO 2 can provide a remarkable photocatalytic activity (a H 2 production rate of 45.3 mmol h −1 mg −1 Pt for 65 mW/cm 2 365 nm light). This high (maximized) efficiency can be achieved with a remarkably low loading amount of Pt SAs on TiO 2 nanosheets (0.03 wt %), which is far superior to Pt nanoparticles on a TiO 2 nanosheet with the same or a higher loading amount. F-stabilized Pt SAs on TiO 2 nanosheets also exhibit an excellent stability in long-term photocatalytic reactions.

Multicopper oxidase belongs to the class of enzyme containing four or more Cu centers in a protein molecule (1). The minimum functional unit of multicopper oxidase comprises a set of one type 1 Cu, one type 2 Cu, and a pair of type 3 Cus. The type 1 Cu functions as the electron mediator from a substrate to the trinuclear center composed of the type 2 Cu and type 3 Cus, where dioxygen is bound and reduced to two water molecules. All these copper sites are indispensable for the four-electron reduction of dioxygen without the release of activated oxygen species as intermediates.When lacquer tree laccase, the best studied multicopper oxidase, was reduced fully and reacted with dioxygen, the three-electron reduced form of dioxygen appeared within 15 ms with a life-time of s to min order depending on the pH (2, 3). We spectroscopically and magnetically characterized this species as the oxygen-centered racial bound to the trinclear copper center, finding that it decayed on accepting the final electron from type 2 Cu under the control of proton transfer gating (4). In order to detect the preceding inter-1 This study was supported by Grants-in-Aid for Scientific Research, C 11640558 and B 13440194, from the Ministry of Education, Science, Sports and Culture of Japan, and the Joint Studies Program of the Institute for Molecular Science 1 To whom correspondence should be addressed. E-mail: tsO513@ kenroku.kanazawa-u.ac.jp Abbreviations: TloxT23red, type 1 Cu as Cu(II), and type 2 and 3 Cus as Cud); TloxT3red, type 2 Cu-depleted laccase in which type 1 Cu is Cu(II) and type 3 Cus are reduced; T12oxT3red, type 1 and 2 Cus as Cu(ll), and type 3 Cus as Cu(D; EPR, electron paramagnetic resonance; CD, circular dichroism; T, tesla (1 T = 10,000 G); TlHg, mercury derivative of laccase at the type 1 Cu site; FTTR, Fouriertransform infrared; DPPH, diphenylpicrylhydrazyl.© 2001 by The Japanese Biochemical Society. mediate, such as the two-electron reduced form of dioxygen, we investigated the earlier reaction process of the reduced laccase with dioxygen by means of stopped-flow spectroscopy (2). However, it was impossible to detect the two-electron reduced form of dioxygen because the diffusion of dioxygen towards the active site was too slow (ms order) compared with the rate of the electron transfer from type 1 Cu to the putative peroxide intermediate (the two-electron reduced form) (|xs or less order). The content of the two-electron reduced species has been estimated to be a few percent and only the formation of the metastable three-electron reduced form of dioxygen (the radical intermediate) could be observed insofar as the reactions of the native enzyme were studied (3).The type 2 Cu in laccase has been selectively depleted through the action of potassium hexacyanoferratefll) CK,-[Fe(CN) 6 ]) on the resting enzyme under anaerobic conditions, followed by the action of dimethylglyoxime and EDTA (5). In the type 2 Cu-depelted laccase the type 1 Cu is cupric and the coupled type 3 Cus are cuprous (TloxT3red, which has been simply ab...

An efficient and practical protocol for the transfer hydrogenation of nitroarenes was developed, which uses flower‐shaped micro‐mesoporous iron oxide (MMIO) with formic acid as the reducing agent and tris[(2‐diphenylphosphino)‐ethyl]phosphine as the ligand in the absence of an additional base. The recyclable catalytic system enables the reduction of the nitro group in a broad range of substrates to yield valuable amines and shows a high tolerance to sensitive functional groups.

A magnetic photocatalytic material composed of nanoscale zero-valent iron (nZVI) homogeneously distributed over a mesoporous nanocrystalline TiO2 matrix has been prepared by a multistage chemical process, including sol-gel technique, wet impregnation, and chemical reduction. X-ray powder diffraction and Raman spectroscopy were used for the structural and chemical characterization of the magnetic photocatalyst, while bulk magnetization measurements and scanning/transmission electron microscopy were employed to determine the physical and textural properties of the photocatalyst. The synthesized nZVI@TiO2 photocatalyst shows very high efficiency in the removal of hexavalent chromium, Cr(vi), from water. The degradation rate follows a pseudo-first-order kinetic model. Most importantly, the remarkable efficiency of the photocatalyst is found to be due to the synergistic contributions of both counterparts, nZVI and TiO2, as validated by comparative experiments with neat TiO2 and nZVI@TiO2 under UV-C irradiation and without irradiation. New insights into the mechanism of synergistic degradation of chromium(vi) and suppressed oxidation of nZVI particles in the composite material are proposed and therein discussed.

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