(203-211)Effect of high gold salt concentrations on the size and polydispersity of gold nanoparticles prepared by an extended Turkevich–Frens method

摘要

The Turkevich–Frens synthesis starting conditionsare expanded, ranging the gold salt concentrations up to 2 mMand citrate/gold(III) molar ratios up to 18:1. For each concentrationof the initial gold salt solution, the citrate/gold(III)molar ratios are systematically varied from 2:1 to 18:1 andboth the size and size distribution of the resulting gold nanoparticlesare compared. This study reveals a different nanoparticlesize evolution for gold salt solutions ranging below0.8 mM compared to the case of gold salt solutions above0.8 mM. In the case of [Au3+]<0.8 mM, both the size and sizedistribution vary substantially with the citrate/gold(III) ratio,both displaying plateaux that evolve inversely to [Au3+] atlarger ratios. Conversely, for [Au3+]≥0.8 mM, the size andsize distribution of the synthesized gold nanoparticles continuouslyrise as the citrate/gold(III) ratio is increased. A startinggold salt concentration of 0.6mMleads to the formation of themost monodisperse gold nanoparticles (polydispersity index<0.1) for a wide range of citrate/gold(III) molar ratios (from 4:1to 18:1). Via a model for the formation of gold nanoparticlesby the citrate method, the experimental trends in size could bequalitatively predicted: the simulations showed that the destabilizingeffect of increased electrolyte concentration at highinitial [Au3+] is compensated by a slight increase in zetapotential of gold nanoparticles to produce concentrated dispersionof gold nanoparticles of small sizes.