Facile fabrication of single crystal gold nanoplates with micrometer lateral size

In this study, we present a facile method to synthesize gold nanoplates with micrometer lateral size by the reaction of chloroauric acid with dopamine. The synthesis process does not require any surfactants, seed crystals, or exotic power input such as heating or agitating. The as-prepared gold nanoplates, which appear in triangular, truncated triangular or hexagonal shape, are single crystal and mainly enclosed by gold (1 1 1) planes. More importantly, the plate thickness is tunable by adding different amount of diluted hydrochloric acid to the reactant solution. The effects of the molar ratio of chloroauric acid to dopamine, the initial pH value and the presence of NaCl on the nanoplates are investigated in detail. It is demonstrated that a relatively low molar ratio and an acidic condition facilitate the anisotropic growth of gold nanoplates. Besides, the thickness of nanoplates can be greatly influenced by the synergistic effect of H+ and Cl−. Finally, the morphology evolution of the product at different reaction time was investigated, and a preliminary crystal growth mechanism was proposed.