Synthesis and Ag-loading-density-dependent photocatalytic activity of Ag@TiO2 hybrid nanocrystals

Silver-decorated TiO2 nanoparticles (Ag@TiO2) were synthesized by photoreducing Ag+ species in an EG–ethanol solution in the presence of TiO2 (P25) nanoparticles. The TEM observations indicate that the Ag nanoclusters (NCs) with a size range of 1–3 nm were uniformly anchored on the surfaces of TiO2 nanoparticles. The Ag@TiO2 nanocomposites with various amounts of Ag NCs (0.5–10% in mass) were synthesized by changing the concentrations of Ag+ in their precursors. The photocatalytic activity of the as-synthesized Ag@TiO2 nanocomposites was investigated by photodegradating RhB dye under visible-light irradiation (λ ≥ 400 nm). The results show that the as-obtained Ag@TiO2 nanocomposites show a novel Ag-loading-density-dependent photocatalytic activity, and that the Ag@TiO2 photocatalyst with ∼1% Ag NCs has the best photocatalytic performance with a high rate constant, 22 times higher than that of P25 TiO2 under the same condition. The enhanced photocatalytic performance should be attributed to the LSPR property of Ag NCs. The possible mechanism for the Ag-loading-density-dependent photocatalytic performance was discussed in detail.