Organic-Inorganic Dual-Coated TiO₂ Nanoparticles for Regulation of Photocatalytic Activity

Abstract

Organic-inorganic dual-coated photocatalytic TiO₂ nanoparticles (NPs) were obtained by two-step surface modification of i) an inner SiO₂-coating and ii) outer alkylation through a silane coupling reaction, exhibiting tunable photocatalytic activity. Evaluation of the photocatalytic activity under ultraviolet ray irradiation revealed that the dual coating on the surface of the TiO₂ NPs changed the reaction rate-determining step of the photocatalytic decomposition of methylene blue (MB) from an adsorption-limited manner to a diffusion-limited manner. Unmodified TiO₂ NPs decomposed MB as soon as MB was adsorbed on the surface, while the decomposition reaction proceeded in the concentration-independent diffusion-controlled manner in the surface-modified NPs. The double shells might confine both outward excited electron diffusion and inward substance diffusion, preventing the generation of active oxygen on the surface of TiO₂ NPs.