Gold Nanoparticles Formation via Au(III) Complex Ions Reduction with l-Ascorbic Acid

In this paper, the kinetics and mechanism of gold nanoparticles formation during the redox reaction between [AuCl4]¯ complex and l-ascorbic acid under different conditions were described. It was also shown that reagent concentration, chloride ions, and pH influence kinetics of nucleation and growth. To establish rate constants of these stages, the model of Finke and Watzky was applied. From Arrhenius and Eyring dependencies, the values of activation energy (22.5 kJ mol−1 for the nucleation step and 30.3 kJ mol−1 for the growth step), entropy (about −228 J K−1 mol−1 for the nucleation step and −128 J K−1 mol−1 for the growth step), and enthalpy (19.8 kJ mol−1 for nucleation and 27.8 kJ mol−1 for particles growth) were determined. It was also shown that the disproporationation reaction had influence on the rate of nanoparticles formation and may have impact on final particles morphology.