Site-Selective Plasmonic Etching of Silver Nanocubes

Plasmon-induced charge separation (PIGS) at the interface between a plasmonic nanoparticle and semiconductor is now widely used for photovoltaics and photocatalysis. Here we take advantage of PIGS for site-selective nanoetching of silver nanocubes on TiO2 beyond the diffraction limit. A silver nanocube exhibits two resonance modes localized at the top and bottom of the nanocube (distal and proximal modes, respectively) when it is placed on TiO2. We achieved selective etching at the top and the bottom of the nanocubes by PIGS based on the distal and proximal modes, respectively. The site-selective nanophotonic etching reveals that the anodic reaction involved in PIGS is induced by the plasmonic near field, which causes an external photoelectric effect. In particular, the distal mode etching at the top edges is explained in terms of ejection of energetic electrons (or hot electrons) from the distal site to TiO2 across the nanocube.