Procedure Optimization for Increasing Biosynthesis Rate of Gold Nanoparticles by Aspergillus flavus Supernatant

Biosynthesis of gold nanoparticles was investigated using Aspergillus flavus and the procedure was optimized for maximum production. The color changing from whitish-yellow to purple along with the maximum absorbance at 540 nm in UV-vis spectrum approved the production of gold nanoparticles preliminarily. The XRD spectrum of nanoparticles showed 2θ values corresponding to the gold nanocrystals. TEM micrographs demonstrated the extracellular formation of spherical gold nanoparticles. The optimization process revealed that the maximum rate of gold nanoparticles production achieved after 6 h at 28°C, 2.5 mM HAuCl4 concentration, and pH 6 with different shapes in the size range of 30–50 nm.