Spherical aggregates composed of gold nanoparticles

Abstract

Alkylated triethylenetetramine (C12E3) was synthesized and used as botha reductant in the preparation of gold nanoparticles by the reduction ofHAuCl4 and a stabilizer in the subsequent self-assembly of the gold nanoparticles.In acidic aqueous solution, spherical aggregates (with a diameter of about202 ± 22 nm) of gold nanoparticles (with the mean diameter of∼18.7 nm) were formed. The anion-induced ammonium adsorption of the alkylated amines onthe gold nanoparticles was considered to provide the electrostatic repulsion andsteric hindrance between the gold nanoparticles, which constituted the barrierthat prevented the individual particles from coagulating. However, as the aminogroups became deprotonated with increasing pH, the ammonium adsorption wasweakened, and the amino groups were desorbed from the gold surface, resulting indiscrete gold particles. The results indicate that the morphology of the reducedgold nanoparticles is controllable through pH-‘tunable’ aggregation under themediation of the amino groups of alkylated amine to create spherical microstructures.