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 TiO 2 surface (Ag@AgBr/mp-TiO 2 ). The localized surface plasmon resonance (LSPR) of Ag NP-loaded TiO 2 (Ag/mp-TiO 2 ) rapidly weakens in the air at room temperature. In contrast, the LSPR intensity of Ag@AgBr/mp-TiO 2 is preserved in the air at least for several days. Ag@AgBr/mp-TiO 2 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)–SiO 2 (shell) NP-incorporated TiO 2 (TiO 2 /Ag@SiO 2 ) 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-TiO 2 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 TiO 2 /Ag@SiO 2 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.