Structural evolution of Ag-Au nanoplates by pH controlled galvanic displacement

In this study, we performed a systematic study of the replacement reaction between silver nanoplates and an aqueous HAuCl4 solution. The aqueous HAuCl4 solution was adjusted to various pH values before the reaction. Under the different pH conditions, the hydrolyzed Au complexes existing in the solution have different concentrations. As a result, the total standard potential of the solution decreased with increasing pH. Thus, the pH was used to investigate the morphological, structural, compositional, and spectral changes of the reaction on the nanoscale. The alloy and dealloying processes were monitored and different structures were obtained. This work has enabled us to prepare metal nanostructures with controllable shapes at room temperature and their optical properties could be readily tuned by adjusting the pH. (C) 2012 Elsevier B.V. All rights reserved.