Little adjustments significantly improve the Turkevich synthesis of gold nanoparticles

In this report, we show how the classical and widely used Turkevich synthesis can be improved significantly by simple adjustments. The gold nanoparticles (AuNPs) produced with the optimized protocol have a much narrower size distribution (5-8% standard deviation), and their diameters can be reproduced with unrivaled little variation (<3%). Moreover, large volumes of these particles can be produced in one synthesis; we routinely synthesize 1000 mL of ∼3.5 nM AuNPs. The key features of the improved protocol are the control of the pH by using a citrate buffer instead of a citrate solution as the reducing agent or stabilizer and optimized mixing of reagents. Further, the shape uniformity of the particles can be improved by addition of 0.02 mM EDTA. While the proposed protocol is as straightforward as the original Turkevich protocol, it is more tolerant against variations in precursor concentration.