UV–vis spectroscopy for on-line monitoring of Au nanoparticles size during growth

Gold nanoparticles have been prepared by alcoholic reduction of Au(III) ions in presence of a polymeric stabilizer (poly(Nvinyl pyrrolidone), PVP). On-line UV–vis spectroscopic characterization and transmission electron microscopy (TEM) analysis are presented. Optical spectroscopy data show that the temporal evolution of absorption spectra and the absorbance peak properties are correlated to the off-line size measurements obtained at chemical reaction end by TEM micrographs. The Au cluster size behaves linearly with time above a threshold temperature (70 8C), according to a deposition-controlled growth mechanism