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

• Published in: Gold Bulletin Vol. 45; no. 4; pp. 203 - 211
• Main Authors: Zabetakis, Kara, Ghann, William E., Kumar, Sanjeev, Daniel, Marie-Christine
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.12.2012; World Gold Council
• Subjects: Chemistry and Materials Science; Citrates; Gold; Materials Science; Metallic Materials; Nanoparticles; Original Paper; Properties; United States; High concentration; Synthesis; Citrate reduction; Gold nanoparticles
• ISSN: 2190-7579; 1027-8591; 2190-7579
• DOI: 10.1007/s13404-012-0069-2

The Turkevich–Frens synthesis starting conditions are expanded, ranging the gold salt concentrations up to 2 mM and citrate/gold(III) molar ratios up to 18:1. For each concentration of the initial gold salt solution, the citrate/gold(III) molar ratios are systematically varied from 2:1 to 18:1 and both the size and size distribution of the resulting gold nanoparticles are compared. This study reveals a different nanoparticle size evolution for gold salt solutions ranging below 0.8 mM compared to the case of gold salt solutions above 0.8 mM. In the case of [Au 3+ ] < 0.8 mM, both the size and size distribution vary substantially with the citrate/gold(III) ratio, both displaying plateaux that evolve inversely to [Au 3+ ] at larger ratios. Conversely, for [Au 3+ ] ≥ 0.8 mM, the size and size distribution of the synthesized gold nanoparticles continuously rise as the citrate/gold(III) ratio is increased. A starting gold salt concentration of 0.6 mM leads to the formation of the most monodisperse gold nanoparticles (polydispersity index < 0.1) for a wide range of citrate/gold(III) molar ratios (from 4:1 to 18:1). Via a model for the formation of gold nanoparticles by the citrate method, the experimental trends in size could be qualitatively predicted: the simulations showed that the destabilizing effect of increased electrolyte concentration at high initial [Au 3+ ] is compensated by a slight increase in zeta potential of gold nanoparticles to produce concentrated dispersion of gold nanoparticles of small sizes.