Size-control of monodispersing gold nanoparticles via stepwise seed-mediated growth

Abstract

A stepwise seed-mediated growth approach is practiced to synthesize monodispersing Au particles in diameters of 3.2-14.0 nm using poly(vinylpyrrolidone) (PVP) and D-ascorbic acid as the capping agent and reductant, respectively. The starting Au seeds are in diameters of (1.9±0.4) nm and are obtained by reduction of aqueous HAuCl4 with NaBH4 in the presence of PVP. By control of the ratio of seeds to metal precursor (HAuCl4), nearly dispersing Au particles with average diameters of 3.2, 4.7, 6.3, 8.0, 10.3, and 14.0 nm are obtained in sequential growth steps without the need of using alternative reductant and capping agent. Key factors affecting the size distribution or monodispersity of Au particles are discussed on the basis of LaMer growth model. The use of higher seeds-to-HAuCl4 ratios in coupling with slow ascorbic acid addition is crucial for the control of monodispersity of product Au nanoparticles. Fast ascorbic acid addition would lead to secondary nucleation which results in Au particles with broadly dispersed sizes. © Editorial office of Acta Physico-Chimica Sinica.