AFM investigation of gold nanoparticles synthesized in water/AOT/n-heptane microemulsions

Gold nanoparticles, synthesized within AOT reversed micelles, have been imaged by an atomic force microscope (AFM) operating in the contact mode in air at room temperature. The AFM images show an attractive interaction among gold nanoparticles leading to the formation of well distinct aggregates where, however, each nanoparticle retains its individuality. Moreover, the AFM images show that the mean size of gold nanoparticles is a function of the size of the AOT reverse micelles and offer evidence of a stabilization mechanism of the nanoparticles due, most probably, to the formation of an adsorbed layer of surfactant molecules at the nanoparticle surface. This stabilization mechanism results in being active even at high nanoparticle concentration.