Mechanism of Gold Nanoparticle Formation in the Classical Citrate Synthesis Method Derived from Coupled In Situ XANES and SAXS Evaluation

Although gold nanoparticles (GNP) are among the most intensely studied nanoscale materials, the actual mechanisms of GNP formation often remain unclear due to limited accessibility to in situ-derived time-resolved information about precursor conversion and particle size distribution. Overcoming such limitations, a method is presented that analyzes the formation of nanoparticles via in situ SAXS and XANES using synchrotron radiation. The method is applied to study the classical GNP synthesis route via the reduction of tetrachloroauric acid by trisodium citrate at different temperatures and reactant concentrations. A mechanism of nanoparticle formation is proposed comprising different steps of particle growth…