Local Electric Field-Enhanced Plasmonic Photocatalyst: Formation of Ag Cluster-Incorporated AgBr Nanoparticles on TiO₂

A successive ionic layer adsorption and reaction-photoreduction (SILAR-PR) technique forms Ag clusters mainly in the interior of AgBr nanoparticles (NPs) on the TiO₂ surface (Ag@AgBr/mp-TiO₂). The localized surface plasmon resonance (LSPR) of Ag NP-loaded TiO₂ (Ag/mp-TiO₂) rapidly weakens in the air at room temperature. In contrast, the LSPR intensity of Ag@AgBr/mp-TiO₂ is preserved in the air at least for several days. Ag@AgBr/mp-TiO₂ stably exhibits a high level of photocatalytic activity for the decomposition of 2-naphthol under irradiation of visible-light (λ > 400 nm), whereas Ag­(core)–SiO₂(shell) NP-incorporated TiO₂ (TiO₂/Ag@SiO₂) is only active near UV region (J. Am. Chem. Soc. 2008, 130, 1676). Spectroscopic and photoelectrochemical measurements suggested that the high photocatalytic activity of Ag@AgBr/mp-TiO₂ stems from the enhancement of the local electric field near Ag clusters increasing the rate of the photocharge carrier generation in AgBr in a manner similar to the TiO₂/Ag@SiO₂ system. Eventually, AgBr plays the role of not only a visible-light photocatalyst but also an oxidation inhibitor of Ag clusters, while Ag cluster acts as an amplifier for the local electric field.