Selective exposition of high and low density crystal facets of gold nanocrystals using the seeded-growth technique

Abstract

Control of the crystallographic orientation of nanocrystal facets is widely recognized to be a key prerequisite for the synthesis of highly efficient nanocrystal-based catalysts. Here, we demonstrate that the facet evolution during the synthesis of gold nanocrystals can effectively be controlled by the addition of auxiliary metal ions during the kinetically controlled reduction of precursor salts. In particular, in the presence of Cu²⁺ the formation of predominantly {111} faceted particles is observed, whereas the addition of Ag⁺ and Pb²⁺ is found to result in the selective exposition of {110} and {100} crystal facets. The effect of auxiliary metal ions to induce the exposition of facets with particular crystallographic orientation is interpreted as a consequence of kinetic selection due to underpotential deposition (upd) during the kinetically controlled growth of nanocrystals. In this regard, the observed trends in facet exposition are in agreement with the respective trends of underpotential deposition of the various auxiliary metal additives on single-crystalline planar gold substrates.