Ag size-dependent visible-light-responsive photoactivity of Ag–TiO2 nanostructure based on surface plasmon resonance

Abstract

Anatase TiO₂ nanocrystals with regular polyhedron morphology and co-exposed {001} and {101} facets are prepared, and then ultrafine Ag nanoparticles (SAg NPs) with different sizes are loaded on those TiO₂ facets (denoted as SAg–TiO₂) through a novel in situ photoreduction approach. For comparison, Ag nanoparticles (PAg NPs) are also loaded on TiO₂ facets (denoted as PAg–TiO₂) by a traditional photodeposition method. The experimental results show that PAg NPs with a size of ∼20 nm only appeared on the {101} facets of TiO₂, while SAg NPs with a much smaller size (1–6 nm) are highly dispersed on both {001} and {101} facets of TiO₂. The size of Ag NPs plays an important role in surface plasmon resonance (SPR) effect and the photogenerated carrier separation process, and those Ag NPs loaded on TiO₂ facets show size-dependent photoactivity for the RhB degradation. SAg–TiO₂ with ultrafine SAg NPs on both {001} and {101} facets of TiO₂ results in more substantial visible-light-responsive photoactivity and stability than PAg–TiO₂ with larger Ag NPs on {101} facets of TiO₂. Moreover, the RhB photodegradation reaction rate constant of SAg–TiO₂ with Ag particle size of ∼1 nm is 10 and 21.3 times higher than that of PAg–TiO₂ and the pristine TiO₂, respectively.