Monomeric and polymeric amines as dual reductants/stabilisers for the synthesis of gold nanocrystals: A mechanistic study

Uniform, monodisperse gold nanocrystals have been prepared in a single-step synthesis by the addition of secondary and tertiary alkylamines, or a cationic polymer containing these moieties, to dilute solutions of gold tetrachloraurate. The acidic pH resulted in the formation of quaternary ammonium sites, scavenging loosely bound chloride ions from the tetrachloraurate species, lowering the overall potential and reducing Au-III to nanocrystalline Au-0. The secondary amino groups then served to stabilise the particles, preventing aggregation and collapse of the colloidal system. Addition of further capping groups was thus not required. The particles were characterised by UV/Visible spectroscopy, HR-TEM, Xray diffraction, electrochemical potential and pH measurements (Eh-pH) and FTIR.