One-pot green synthesis of Ag- and Zn-based monometallic and bimetallic nanostructures and evaluation of their antibacterial activities

Abstract

Herein, a bio-inspired synthetic procedure was described for Ag, ZnO, and Ag/ZnO nanocomposites using an extract of Dendrophthoe falcata leaves. The leaf extract functioned both as a reducing and stabilizing agent, making the synthesis totally green. The biogenic nanoparticles (NPs) were characterized by UV–Visible spectroscopy, zeta potential, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). The zeta potential measurement showed the presence of negatively charged groups attached to the surface of NPs providing them moderate colloidal stability. The crystalline nature and structure of NPs were confirmed by powder XRD. The evolution of crystalline phase was noted for Ag NPs at room temperature while annealing at 450 °C was essential for both ZnO and Ag/ZnO phases. According to SEM–EDS and TEM data, the Ag/ZnO composite was rich in Ag concentration and nearly spherical Ag NPs were distributed over the surface of ZnO matrix. Furthermore, the antibacterial efficacy of the as-prepared samples was investigated against both gram-positive and gram-negative bacterial strains. The Zn-based mono- and bimetallic colloids demonstrated a higher antimicrobial potency on gram-positive strains than on gram-negative strains.