Diameter control of gold nanoparticles synthesized in gas phase using atmospheric-pressure H2/Ar plasma jet and gold wire as the nanoparticle source: Control by varying the H2/Ar mixture ratio

Abstract

This report describes diameter control of gold nanoparticles (AuNPs) during synthesis using an atmospheric-pressure H2/Ar plasma jet drive with pulse-modulated ultrahigh frequency, employing Au wire as the NP source material. During this process, where most of the AuNPs are regarded as formed through condensation from Au vapor derived by the Au wire etching, the mean diameter varied in the approximate range of 2–12 nm with H2 volume ratios up to 3.9%. In plasma diagnostics, results showed that the H2 volume ratio influences the plasma discharge behaviour, which affects the heat flux density flowed into the Au wire, and the atomic hydrogen concentration in the plasma. Both seemed to influence the etching rate of the Au wire per unit area, which is directly related to the concentration of Au vapor in the plasma. The concentration is one factor affecting the particle size evolution because of the collisions among vapor species in reaction field. Therefore, the AuNP size variation with the H2 volume ratio was discussed from the perspective of the etching rate of the Au wire at each H2 volume ratio.