On-line monitoring of Au nanoparticles formation by optical spectroscopy

Experimental results concerning the synthesis of gold nanoparticles prepared by alcoholic reduction of Au(III) ions in presence of a polymeric stabilizer, and UV-visible spectroscopic characterization is presented. Optical spectroscopic data have been correlated to off-line size measurements obtained analysing transmission electron micrographs. The gold cluster size, coming from both TEM micrographs and absorbance cubic root, behaved linearly with time above a threshold temperature (70 $^\circ$ C) according to a deposition-controlled growth mechanism. The plasmon peak halfwidth behaved linearly with inverse particle radius (obtained by TEM), thus proving the hypothesized mechanism growth. The spectroscopic approach allows an on-line gold cluster measurement with possibility to fine control particle size also in the case of a fast process.