Acceleration effect of copper(II) ions on the rate of citrate synthesis of gold nanoparticles

Abstract

The gold nanoparticles (GNPs) were obtained by modification of the classical Turkevich citrate method by the addition of copper(II) ions in the initial reaction mixture. We studied the kinetics of the nanoparticles growth with or without copper(II) ions, synthesized at two different temperatures. The kinetic curves obtained by means of UV–vis spectroscopy from the plasmon maxima demonstrated the acceleration effects of the copper(II) ions on nucleation and growth of the GNPs. These effects were also confirmed from the Atomic Force Microscope (AFM) imaging data where the AFM was applied as a tool for studying the kinetics of the GNPs’ growth. From the analysis of AFM images in the course of the synthesis process were obtained the sizes (i.e., diameters) of the GNPs and the GNPs’ growth profiles were fitted with the Finke–Watzky (F–W) kinetic model. From the experimental data and the theoretical fits we found that the citrate reduction of the tetrachloroauric acid was accelerated by the addition of copper(II) ions as well as the GNPs’ growth was accelerated following the F–W kinetics model. Using Transmission Electron Microscopy (TEM) we compared the morphology and the size distribution of the nanoparticles synthesized by the citrate method with or without copper(II) ions. The results showed that the addition of copper(II) ions in the initial reaction mixture of the Turkevich citrate synthesis let to acceleration of both the nucleation and the growth processes following the F–W kinetic model.