Photocatalytic TiO(2) powders impart ultraviolet light-induced self-cleaning and antibacterial functions when coated on outdoor building materials. For indoor applications, however, TiO(2) must be modified for visible-light and dark sensitivity. Here we report that the grafting of nanometer-sized Cu(x)O clusters onto TiO(2) generates an excellent risk-reduction material in indoor environments. X-ray absorption near-edge structure using synchrotron radiation and high-resolution transmission electron microscopic analyses revealed that Cu(x)O clusters were composed of Cu(I) and Cu(II) valence states. The Cu(II) species in the Cu(x)O clusters endow TiO(2) with efficient visible-light photooxidation of volatile organic compounds, whereas the Cu(I) species impart antimicrobial properties under dark conditions. By controlling the balance between Cu(I) and Cu(II) in Cu(x)O, efficient decomposition and antipathogenic activity were achieved in the hybrid Cu(x)O/TiO(2) nanocomposites.

We have prepared a TiO 2 -based novel visible-light-sensitive photocatalyst, in which Fe(III) species were grafted on a rutile TiO 2 surface (denoted as Fe(III)/TiO 2 ). With use of X-ray absorption fine structure analysis, the grafted iron species were determined to be in the 3+ state and adopt an amorphous FeO(OH)-like structure. Fe(III)/TiO 2 displayed optical absorption in the visible light range over 400 nm, which was assigned to the interfacial charge transfer from the valence band of TiO 2 to the surface Fe(III) species. Its photocatalytic activity was evaluated by the decomposition of gaseous 2-propanol under visible light (400-530 nm), which revealed a high quantum efficiency (QE) of 22%. Monochromatic light experiments indicated that the effective wavelength region was extended as far as 580 nm while maintaining a QE of greater than 10%. On the basis of the analogy to Cu(II)-grafted TiO 2 photocatalyst et al. Chem. Phys. Lett. 2008, 457, 202), we speculate that the high performance of the present photocatalyst is derived from the photoproduced holes that are generated in the valence band of TiO 2 and contribute to the oxidative decomposition of 2-propanol, and the catalytic reduction of oxygen (presumably multielectron reduction) by photoproduced Fe(II) species on TiO 2 .

The water splitting under visible light irradiation has been achieved by the Z-scheme system constituted of an Fe3+/Fe2+ redox couple as an electron relay and two powdered heterogeneous photocatalysts which we have recently developed. The (Pt/SrTiO3:Rh)–(BiVO4) system showed the highest activity with 0.3% of an apparent quantum yield at 440 nm. It can use visible light up to 520 nm.