Green synthesis of Ag doped ZnO nanoparticles: study of their structural, optical, thermal and antibacterial properties

Currently, different physical and chemical methods are being used for the synthesis of nanomaterials, which has associated critical issues like environmental toxicity and cost-effectiveness. This requires to be addressed by adopting an alternate approach. This article reports the synthesis and characterisation of undoped and Ag-doped ZnO nanoparticles for antibacterial applications. The nanoparticles were synthesised via a green synthesis approach using leaf extracts of three different plants, namely, Azadirachta indica, Hibiscus rosa-sinensis and Ocimum tenuiflorum. The biosynthesised ZnO:Ag nanoparticles were characterised by XRD, TEM, FESEM, UV-visible spectroscopy, FTIR and DSC-TGA. The antibacterial activity of the synthesised samples was tested against Enterococcus hirae (Gram-positive) and Escherichia coli (Gram-negative) bacteria at 100 µl (0.5 mg/mL) concentrations using the disc diffusion method. Comparatively, ZnO:Ag nanoparticles have shown enhanced antibacterial activity against both E. coli and E. hirae with respect to pure ZnO nanoparticles, which were found to be better than commercial antibiotic kanamycin.