Au Nanoparticle Synthesis Via Femtosecond Laser-Induced Photochemical Reduction of [AuCl4]−

Abstract

Laser-assisted metallic nanoparticle synthesis is a versatile “green” method that has become a topic of active research. This chapter discusses the photochemical reaction mechanisms driving AuCl4½?? reduction using femtosecond-laser irradiation, and reviews recent advances in Au nanoparticle size-control. We begin by describing the physical processes underlying the interactions between laser pulses and the condensed media, including optical breakdown and supercontinuum emission. These processes produce a highly reactive plasma containing free electrons, which reduce AuCl4½??, and radical species producing H2O2 that cause autocatalytic growth of Au nanoparticles. Then, we discuss the reduction kinetics of AuCl4½??, which follow an autocatalytic rate law in which the first- and second-order rate constants depend on free electrons and H2O2 availability. Finally, we explain strategies to control the size of gold nanoparticles as they are synthe-sized; including modifications of laser parameters and solution compositions.