Synthesis and agglomeration of gold nanoparticles in reverse micelles

Abstract

Reverse micelles prepared in the system water, sodium bis-(2-ethylhexyl) sulfoccinate (AOT), and isooctane were investigated as a templating system for the production of gold nanoparticles from the reduction of Au (III) by sulfite ions. A coreshell Mie model was used to describe the optical properties of gold nanoparticles synthesized inside the reverse micelles. Dynamic light scattering measurements of gold colloids in aqueous media and in reverse micelle solution indicated agglomeration of micelles containing particles. This agglomeration was verified theoretically by estimating the total interaction energy between pairs of particles as a function of particle size. The analysis indicated that particles larger than about 8 nm diameter should reversibly flocculate. Transmission Electron Microscopy measurements of gold nanoparticles produced inside reverse micelles showed diameters of 8 to 10 nm. Evidence of cluster formation was also observed. Time correlated UV-Vis absorption measurements showed a red shift for the peak wavelength. This was interpreted as the result of multiple scattering and plasmon interaction between particles due to agglomeration of micelles with particles larger than 8 nm.