Electrochemically shape-controlled formation of concave AuPd alloy nanoparticles on ITO substrate

Abstract

Shape-control of AuPd alloy nanoparticles (AuPd NPs) substrated on indium-tin oxide (ITO) was successfully achieved, for the first time, by using electrochemical square-wave-potential (SWP) method. Concave trisoctahedral AuPd alloy NPs (TOH AuPd NPs) and concave hexoctahedral AuPd alloy NPs (HOH AuPd NPs) were prepared under SWP conditions with lower potential of 0.3 V while different upper potentials of 0.64 and 0.70 V, respectively. Different techniques including SEM, EDX and electrochemical cyclic voltammetry were employed to characterize the morphology and composition of AuPd alloy NPs. The results demonstrated that the as-prepared TOH AuPd NPs and HOH AuPd NPs are uniform in shape of correspondingly concave TOH and concave HOH, and are well dispersed on the ITO substrate. The composition in terms of and Au:Pd atomic ratio of both TOH and HOH AuPd alloy NPs is determined by EDX around 3:1. However, a surface enrichment of Au on the AuPd NPs was observed, and is ascribed to the lower surface energy of Au in comparison with that of Pd. It has been found that, starting from the as-synthesized TOH AuPd NPs, shape transformation from TOH to HOH can be accomplished by applying a treatment of square wave with lower potential of 0.3 V and upper potential of 0.7 V. Prolonging the treatment time results in increasing the size of AuPd NPs, while the HOH shape is preserved.