A novel colloidal approach toward semiconductor/metal nanocomposites is presented. Organic-soluble anatase TiO(2) nanorods are used for the first time to stabilize Ag nanoparticles in optically clear nonpolar solutions in the absence of specific ligands for silver. Metallic silver is generated upon UV illumination of deaerated TiO(2) solutions containing AgNO(3). The Ag nanoparticles can be obtained in different size-morphological regimes as a function of the irradiation time, due to light-induced photofragmentation and ripening processes. A mechanism for the colloidal stabilization of the silver nanoparticles is tentatively suggested, which regards the TiO(2) nanorods as inorganic stabilizers, thus acting in the same manner as conventional surfactant molecules. The proposed photocatalytic approach offers a convenient method for producing TiO(2)/Ag nanocomposite systems with a certain control over the metal particle size without the use of surfactants and/or additives. Stable colloidal TiO(2)-nanorod-stabilized Ag nanoparticles can be potentially available for a number of applications that require "clean" metal surfaces, such as homogeneous organic catalysis, photocatalysis, and sensing devices.

The photocatalytic performance of anatase TiO 2 nanorod-stabilized Ag nanoparticles has been investigated during the reductive bleaching of a model dye, Uniblue A (UBA), in homogeneous organic solutions. The activity of the TiO 2 /Ag nanocomposite has been found to vary continuously during the course of photocatalysis, following a concomitant light-induced modification of the metal nanoparticle size and size distribution. The direct involvement of the metal particles in mediating electron transfer between photoexcited TiO 2 and the target UBA is explained on the basis of the size-dependent redox properties of the metal nanoparticles. The present results can be useful in the design of new composite materials with well-tailored photocatalytic properties and long-term stability.

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