Composites of metal nanoparticles and TiO2 immobilized in spherical polyelectrolyte brushes.

The synthesis and the catalytic activity of nanocomposites consisting of metal nanoparticles (Au, Pt, Pd) and nanoparticles of TiO(2) (anatase) is presented. These composite particles have been synthesized by reduction of the respective metal ions adsorbed on the surface of as-prepared TiO(2) nanoparticles that are immobilized on spherical polyelectrolyte brush particles (SPB) as carrier system. The SPB particles consist of a polystyrene core from which long chains of poly(styrene sodium sulfonate) are grafted. We demonstrate that the metal nanoparticles (such as Au, Pt, and Pd) are only generated on the surface of the anatase particles having a size of ca. 10 nm. These metal NP/TiO(2)@SPB composite particles exhibit a high colloidal stability. They are excellent heterogeneous photocatalysts for the degradation of the dye Rhodamine B under UV irradiation. The photocatalytic activity of the composite particles is 2-5 times higher than that of the pure TiO(2) particles. This finding is traced back to an enhanced adsorption of the dye on the metal@TiO(2) composites.