Phytosynthesis of colloidal nanosilver from Mentha longifolia and Mentha arvensis: Comparative morphological and optical characterization

The present study involves an ecofriendly strategy for the reduction of bulk silver into its nanoforms by using the aqueous extracts of Mentha longifolia leaves (MLL), M. longifolia branches (MLB), and Mentha arvensis (MA). Synthesis of silver nanoparticles (AgNPs) was confirmed initially by observing a change in the color of the reaction mixture followed by measuring the absorbance, and a characteristic surface plasmon resonance band was observed between 400 and 500 nm of the λ of light. Morphological and optical characterization techniques of AgNPs were performed by using UV–visible spectrophotometer, scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy (EDX), and dynamic light scattering (DLS) analysis. It was confirmed that the phytosynthesized nanoparticles are anisotropic and nearly spherical having a size smaller than 100 nm while some cubical and prismatic nanostructures were also observed. The average size of a single nanoparticle measured by DLS analysis was reported 10.50 nm, 15.55 nm, and 20.46 nm biofabricated by using MLB, MLL, and MA extract, respectively. The EDX analysis reported the presence of elemental Ag while elemental O was also observed in MLL and MLB AgNPs. The results from these experiments endorse the potential of reported plant species to phytosynthesize AgNPs. The future applications of this work involve the utilization of AgNPs for multiple biological applications.