Thiosulfate-mediated seeded growth of Au@AuAg yolk–shell nanocubes with surface concavity: optical and catalytic properties

Abstract

Gold–silver (Au–Ag) nanocrystals with a combination of concave surface and hollow interior are of great interest due to their distinctive structural merits. Herein, we introduce a facile strategy based on seed surface doping to create concave Au@AuAg yolk–shell nanocubes with surface concavity (Au@AuAg YSCNCs), and examine their intriguing properties in optics and catalysis. In particular, the Au@Ag core–shell nanocubes are generated and reacted with sodium thiosulfate, followed by the addition of HAuCl₄ to remove Ag atoms on the side walls and deposit Au/Ag atoms on the corners/edges via the galvanic replacement reaction. UV-vis extinction spectra show that compared to Au@Ag core–shell nanocubes, the current Au@AuAg YSCNCs enable a redshift in the major absorption peak, which should be attributed to the increase in charge polarization regions. Meanwhile, the structural advantage is validated using the reduction of 4-nitrophenol as the model reaction. In particular, the current Au@AuAg YSCNCs exhibit an enhanced catalytic efficiency compared to the Au@Ag core–shell nanocubes. Mechanism study using density functional theory reveals that the structural advantage boosts the catalytic activity by upshifting the d-band center and thus lowering the activation barrier. The current study provides a feasible strategy to integrate two structural features (e.g., concave surface and hollow interior) into one AuAg nano-entity, which could be potentially extended to other metals and/or alloys.