Microwave-assisted synthesis, characterization and antibacterial activity of Ag/ZnO nanoparticles supported bentonite clay

Composites of silver-zinc oxide nanoparticles supported on bentonite clay were synthesized by the microwave-assisted synthesis method for use as an antibacterial material. Silver nitrate was used as the precursor of silver nanoparticles while zinc oxide nanoparticles were commercially sourced. The composites were characterized by powder X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared (FTIR) and BET surface area measurements. XRD spectra showed peaks of silver confirming the formation of the silver and not of the silver nitrate or any other impurity of the metal. Meanwhile TEM confirmed the formation of silver and zinc oxide nanoparticles on the clay layers, with particle sizes ranging from 9-30 nm and 15-70 nm, respectively. The antibacterial activities of the composites were evaluated against Gram negative Escherichia coli bacteria and Gram positive Enterococcus faecalis bacteria by the disc diffusion method. Whereas both composites of Ag-clay and ZnO-clay showed good antibacterial activity against bacteria, a better antibacterial activity was observed with Ag/ZnO-clay composite. The results therefore reveal that Ag/ZnO-clay composite is a promising bactericide that can be used for deactivating microbes in water.