Green synthesis of silver nanoparticles by a novel method: Comparative study of their properties

► This study presents a novel green method for the synthesis of AgNPs. ► A mixture of Ag+, a starch solution and a supernatant of a fungal culture are used. ► This novel method compared with modified polysaccharide and microbial methods. ► The synthesized AgNPs were characterized by UV–visible, DLS, FTIR, XRD and TEM analyses. ► Results show that the novel method produced high quality AgNPs than the others. This study presents a novel green method using starch for the synthesis of silver nanoparticles (AgNPs). In this method, the fungal supernatant was added to a mixture of starch and silver nitrate solutions. The characteristics of AgNPs synthesized by three independent processes—a modified polysaccharide method, a microbial method, and our novel method—were compared. Dynamic light scattering (DLS) analysis revealed that the average sizes of AgNPs synthesized by the microbial method, the modified polysaccharide method, and our novel method were 84, 20, and 15nm, respectively. The most stable AgNPs were generated by our novel method. The X-ray diffraction (XRD) spectrum of the products from the novel method showed that these AgNPs have high crystallinity. Fourier-transform infrared spectroscopy (FTIR) spectra demonstrated that the functional groups present in the products prepared by the novel method are a combination of the functional groups present in the AgNPs synthesized by the other two methods.