Size controlled, time-efficient biosynthesis of silver nanoparticles from Pleurotus florida using ultra-violet, visible range, and microwave radiations

Monodisperse silver nanoparticles (AgNPs) were synthesized from cell free extracts of edible fungus Pleurotus florida by different electro-magnetic radiations, microwave, visible light and ultra-violet rays. The UV-vis spectroscopy of these nano-silver sols indicated the absorption maxima in 425-500 nm range. Synthesized nano-Ag sols had near spherical particles with nano-scale dimensions embedded in a matrix. Microwave irradiation led to synthesis of mono-disperse AgNPs of size similar to 10 nm within 150 s of exposure. However, visible light and ultra violet radiations led to synthesis of polydisperse AgNPs with inconsistent dimensions. The Fourier transform infrared spectroscopy of AgNPs elucidated the presence of molecules of fungal origin besides the vibrational peaks for Ag-O bond. The fungal proteins showed novel conformations upon capping the nanoparticles. The antibacterial activity of the AgNPs against gram positive and negative pathogens was assessed to determine their potential applications in silver-loaded antibacterial materials.