Antibacterial activity studies of ZnO nanostructures with different morphologies against E. coli and S. aureus

In the current study, three different ZnO nanostructures (Z1, Z2, and Z3) were synthesized using solid-state thermal decomposition, homogeneous precipitation, and wet chemical methods. The nanostructures were characterized using different techniques. Formation of ZnO nanostructures with wurtzite structure is demonstrated by powder XRD. FESEM and TEM studies show rod-like morphology of Z1 and Z2 nanostructures, while the morphology of Z3 nanostructures is hierarchical assembly consisting of nanorods. From TEM studies, average length of rods in Z1 and Z2 nanostructures are about 0.33 and 1.43 µm, while the average diameter of rods in Z1, Z2, and Z3 nanostructures are in the range of 16–90 nm. SAED results indicate single crystalline nature of Z1 and Z2 and polycrystalline nature of Z3 nanostructures. DRS studies indicate that the band gap of Z1, Z2, and Z3 nanostructures is about 3.20–3.30 eV. After characterization, the antibacterial activity of ZnO nanostructures was evaluated against Escherichia coli and Staphylococcus aureus by zone of inhibition and sprinkle methods. The current study was undertaken to evaluate and compare antibacterial activity of ZnO nanostructures with different shapes synthesized using three different methods. In the zone of inhibition method, ZnO nanostructures exhibit better antibacterial activity against S. aureus than E. coli, while in the sprinkle method, Z2 and Z3 nanostructures exhibit complete antibacterial activity at 10 and 20 mg concentrations against S. aureus while only Z3 nanostructures exhibit complete antibacterial activity at 10, 20 and 30 mg concentrations against E. coli.