Effects of discharge duration on the size and shape of gold nanoparticles synthesized using solution plasma processing

Abstract

Gold nanoparticles were synthesized with various discharge durations using solution plasma processing (SPP), and the effects of the discharge duration between 120 and 900 s on the size and shape of the gold nanoparticles were investigated using UV–Vis NIR spectrophotometry and transmission electron microscopy (TEM). The results showed that discharge duration had a strong effect on the formation of gold nanoparticles. The results from the UV–Vis NIR spectrophotometer showed that an absorption coefficient peak at a wavelength of approximately 520 nm was observed, which indicated the formation of gold nanoparticles. As the discharge duration increased, the average particle diameter and the size distribution became smaller. Especially for the discharge duration of 900 s, the average diameter of gold nanoparticles was measured to be the smallest, less than ⩽25 nm in diameter, and most uniform in size distribution. The particle shape became more spherical as the discharge duration increased. Possible mechanisms for the formation of nanoparticles in SPP were suggested in that electrons and electric energy provided from SPP are to increase the surface potential of nanoparticles and, consequently, the increment of electrons and electric energy produces many charged nanoparticles. The charged particles prevent or reduce particle aggregation strongly so that the diameter of the nanoparticles decreased.