Growth of Ag-nanoparticles using aspartic acid in aqueous solutions

Spectrophotometric, kinetic, and transmission electron microscopic (TEM) data for the formation of Ag-nanoparticles using aspartic acid (Asp) as reductant are reported for the first time. In the formation of transparent silver sols, an alkaline medium is required. The silver nanoparticles are spherical, uniform particle size, and strongly depend on the [Asp]. The apparent rate constant decreases with [Asp] (from 4.0 to 24.0 x 10(-4) mol dm(-3), the rate constants decreased from 2.6 x 10(-4) to 0.3 x 10(-4) s(-1)). For a certain reaction time, i.e., 30 min, the absorbance of the silver sol first increased until it reached a maximum, and then decreased with [Asp]. Kinetic and TEM results indicate that the size of the Ag-nanoparticles depends on the [Asp]. It is proposed that the oxidation of Asp occurs by the adsorbed Ag+ ions on the surface of Ag2O particles. (C) 2010 Elsevier Inc. All rights reserved.