Systems and methods for synthesizing silver nanoparticles (SNPs) using Trichoderma fungi have been developed. In an aspect, Trichoderma reesei was used for the extracellular synthesis of silver nanoparticles. In the biosynthesis of metal nanoparticle by a fungus, one or more enzymes or metabolites are produced that reduce a salt to its metallic solid nanoparticles through a catalytic process.