Biosynthesis of Gold Nanoparticles Using Bacteria

Biosynthesis of gold nanoparticles (AuNPs) from Pseudomonas aeruginosa and Rhodopseudomonas capsulata bacteria is considered to be a novel, effective and eco-friendly method. The important parameter, which controls the size and shape of AuNPs, was pH value. The R. capsulata biomass and aqueous HAuCl₄ solution were incubated at pH values ranging from 7 to 4. The AuNPs were characterized by UV–Vis whose absorbance measured at 540 nm followed by transmission electron microscopy showed the formation of AuNPs in the range of 20–80 nm in diameter at pH 6.5. Scanning electron microscopy revealed the AuNPs ranging from 50 to 70 nm, Fourier transform infrared spectroscopy confirmed the formation of AuNPs in the range of 4,000–400 cm^?1. The results demonstrated that spherical AuNPs in the range of 10–20 nm were observed at pH value of 7 whereas a number of nanoplates were observed at pH 4. Hence, the present study enlightens on the green chemistry approach on the production of AuNPs using microorganisms. In comparison to chemical synthesis, the synthesis of AuNPs by microbial source is the most reliable method of production and yield.