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 AuCl 4 ½ À 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 AuCl 4 ½ À , and radical species producing H 2 O 2 that cause autocatalytic growth of Au nanoparticles. Then, we discuss the reduction kinetics of AuCl 4 ½ À , which follow an autocatalytic rate law in which the first-and second-order rate constants depend on free electrons and H 2 O 2 availability. Finally, we explain strategies to control the size of gold nanoparticles as they are synthesized; including modifications of laser parameters and solution compositions.

Fabrication of Gold–Silicon Nanostructured Surfaces with Reactive Laser Ablation in Liquid

“…This method, termed reactive laser ablation in liquid (RLAL), is widely used to form clusters and nanoparticles from reactions of metal salts with ablated surface materials . For instance, RLAL of a silicon wafer in metal salt solutions can form various metal-silica nanostructures, core/shell nanoparticles, − and metal phyllosilicates. , RLAL has recently been used to generate metal carbides on the LIPSS in a variety of metals and synthesize silver–silicon NSS for use in SERS. − Synthesizing these materials in a one-step process allows metal nanoparticles to deposit and embed on the surface, which may enhance their SERS capabilities . Although RLAL has been used by multiple groups to synthesize metal-silicon surfaces for use as SERS substrates, the lack of characterization leaves the composition of the surfaces unknown, and the reaction mechanisms have not been explored. − …”

“…This method, termed reactive laser ablation in liquid (RLAL), is widely used to form clusters and nanoparticles from reactions of metal salts with ablated surface materials. 1 For instance, RLAL of a silicon wafer in metal salt solutions can form various metal-silica nanostructures, 31 core/shell nanoparticles, 32−34 and metal phyllosilicates. 35,36 RLAL has recently been used to generate metal carbides on the LIPSS in a variety of metals 37 and synthesize silver−silicon NSS for use in SERS.…”

One-step femtosecond laser ablation synthesis of sub-3 nm gold nanoparticles stabilized by silica

“…A second laser-assisted approach to metal NP synthesis involves photochemical reduction of metal salts by focusing the laser beam into solution [25]. The dense plasma formed at the laser focus in solution generates a high concentration of reactive species such as hydrated electrons and hydrogen radicals [26], which can reduce metal salts to form isolated metal atoms that coalesce into NPs.…”

Synthesis of Single-Nanometer-Sized Gold Nanoparticles in Liquid–Liquid Dispersion System by Femtosecond Laser Irradiation

“…We expect that the reduction of Au ions to Au atoms followed by the nucleation of AuNPs in aqueous HAuCl4 solution [11][12][13][14] is also operative in the mixture. Initially, the in the presence of AuNPs (eq.…”