Silver-Free Gold Nanocages with Near-Infrared Extinctions

This article reports the preparation of silver-free Au nanocages from cubic palladium templates. Pd nanocubes were subjected to galvanic replacement with Au³⁺ to produce Pd@Au nanocages having tunable dimensions (i.e., edge length, gold layer thickness, and hollow pore size), which allowed selectable positioning of the optical extinction maxima from the visible to the near infrared. These new nanocages circumvent the problems associated with previous Ag-derived gold alloy nanocages, which suffer from the toxicity of residual silver and the possible fragmentation of such alloyed nanostructures, thereby limiting their potential applications. In contrast, the present materials represent stable, nontoxic, tunable, and hollow plasmonic nanostructures.