Preparation and photocatalytic properties of titanium dioxide modified with gold or silver nanoparticles

A nontrivial and simple method for modifying the surface of anatase polymorphic particles with gold or silver nanoparticles has been developed. The method involves the UV-induced formation of Au (Ag) nanoparticles from the corresponding precursors – HAuCl4 or AgNO3 – in a solution of a stabilizing polymer – chitosan, than dispersing TiO2 particles in the resulting colloidal solution, and subsequent enzymatic destruction of chitosan. As a result, Au or Ag nanoparticles, the size of which is 5.0 ± 0.1 nm and 22.0 ± 0.25 nm, respectively, completely settle on the TiO2 surface. It was found that in the reactions of decomposition of methylene blue and para-nitrophenol in an aqueous solution under UV irradiation, modified TiO2 is 2–2.5 times more photocatalytically active than the initial titanium dioxide. It is essential that the photocatalytic properties of TiO2 modified with Au (Ag) nanoparticles also manifest themselves under the action of visible light.