Synthesis of -Cyclodextrin-Modified Water-Dispersible Ag-TiO₂ Core–Shell Nanoparticles and Their Photocatalytic Activity

The -cyclodextrin-modified Ag-TiO₂ core–shell nanoparticles were prepared by sodium borohydrate reduction of AgNO₃ and the subsequent hydrolysis of the tetraisopropyl orthotitanate in an aqueous medium. Inversely in the preparation of -cyclodextrin-modified TiO₂-Ag core–shell nanoparticles, first hydrolysis and then following reduction were carried out. The synthesized spherical core–shell nanoparticles were highly water-dispersible and had an average diameter in the range of 9 to 12 nm. A significant shifting of surface plasmon band was observed for the synthesized Ag-TiO₂ and TiO₂-Ag core–shell nanoparticles. On a model reaction, namely, the photodegradation of phenol by the UV light irradiation, the photocatalytic property of TiO₂ nanoparticles was enhanced, when the Ag nanoparticle was embedded in the core of TiO₂ nanoparticles but TiO₂ nanoparticles coated by Ag shell decreased the photocatalytic property of TiO₂ nanoparticles. The mechanism is ascribed to the surface plasmon characteristics of Ag in the core of the TiO₂ nanoparticles under the acceleration by host–guest inclusion characteristics.