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

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 similar to 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 similar to 1 nm is 10 and 21.3 times higher than that of PAg-TiO2 and the pristine TiO2, respectively.