In situ facile green synthesis of Ag–ZnO nanocomposites using Tetradenia riperia leaf extract and its antimicrobial efficacy on water disinfection

Abstract

In this work, Ag-ZnO nanocomposites were prepared by a green synthesis route using aqueous leaf extract of Tetradenia riperia and investigated for antibacterial activity against Escherichia coli and Staphylococcus aureus. To optimize the synthesis of the Ag-ZnO, the effects of precursor concentrations, pH, and temperatures were studied. The Ag-ZnO nanocomposites were characterized by XRD, ATR-FTIR, FESEM, and TEM. Results show that the concentration of 8% Ag, the temperature of 80 °C, and a pH of 7-8 were optimal for the synthesis of Ag-ZnO nanocomposites. The XRD analysis showed the decrease in particle size of Ag-ZnO from 23.6 to 14.8 nm with an increase in Ag concentrations, which was further supported by FESEM analysis. TEM image of 8% Ag provides more information on the coexistence of Ag on ZnO where an average particle size of 14.8 nm was determined. The ATR-FTIR analysis confirmed the presence of phenolic compounds, which work as reducing and stabilizing agents. The antimicrobial activity results show that Ag-ZnO nanocomposite demonstrated a higher antimicrobial potency on E. coli than on S. aureus. Therefore, Tetradenia riperia leaf extract is a viable route for the synthesis of Ag-ZnO nanocomposites to be used for various applications, including water disinfection.