Nagavenkata Rajesh Pavan Pothukuchi

Molecular Level Insights Into The Turkevich Mechanism of Reduction Of Gold Au(III) Using Citrate

Gold nanoparticles (AuNPs) are one of the most widely used and studied nanomaterials with potential applications in nanomedicine, bionanotechnology, microelectronics, optics, and catalysis. Precise control of these nanoparticles’ size, shape, and synthesis protocols is important in tuning the material properties at bulk. Turkevich’s method for synthesizing citrate-stabilized AuNPs is the most popular because of its straightforward methodology and reliability in producing highly stabilized AuNPs ranging from 5 to 150 nm. The ease of exchanging citrate stabilizers with ligands that show high affinity with gold, especially thiols, allows the multi-functionalization of the AuNPs. The mechanism involves the oxidation of citrate, reduction of auric salt Au(III) to aurous salt Au(I), and disproportionation of the aurous species to gold (Au) atoms.​ Several studies have been conducted in the last 20 years to understand the mechanism of the Turkevich method, which might look simple to the eye but complex to understand. The nucleation and growth mechanism of AuNP formation, the formation of various complexes, the formation of byproducts, and their role in the synthesis are yet to be fully understood at the molecular level. This study aims to understand the reduction of gold from Au(I) to Au(0), especially the disproportionation reaction in the Turkevich method. Force fields to perform classical molecular dynamics (MD) simulations of the complexes were developed using density functional theory (DFT) and analytical methods. The study primarily focuses on understanding the formation of the Gold – di carboxy acetone (DCA-Au) complex and the dependence of the protonation state of DCA on complex formation. The study also highlights the role of the Au-O bond in complex formation.