Formation of gold nanoparticles using amine reducing agents.

We report on the use of amines as reducing agents in the formation of gold nanoparticles. We can predict whether the amines will function as reducing agents in this reaction based on their redox properties. The kinetics of AuNP formation can be understood in terms of Marcus electron transfer theory, where the slower reactions proceed in the inverted region owing to the difference between the Au reduction potential and the amine oxidation potential. For a certain number of the amine reducing agents, following reduction of HAuCl4, a subsequent reaction of the amine radical cation with other reducing agent molecules in solution can form poly(amine)s. These findings point collectively to the utility of amines as reducing agents in AuNP formation and provide information on the conditions under which these reactions will proceed.