Biosynthesis of zinc oxide nanoparticles from Azadirachta indica for antibacterial and photocatalytic applications

Green synthesis of nanoparticles is gaining importance and has been suggested as possible alternatives to chemical and physical methods. The present work reports low-cost, green synthesis of zinc oxide (ZnO) nanoparticles using 25% (w/v) of Azadirachta indica (Neem) leaf extract. The biosynthesized nanoparticles were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), UV-visible spectroscopy (UV-vis), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR). The synthesized ZnO nanoparticles were pure, predominantly spherical in shape with size ranging from 9.6 to 25.5 nm. In the present work, the biosynthesized ZnO nanoparticles have been used for antibacterial and photocatalytic applications. The antibacterial activity of characterized samples was determined using different concentrations of biosynthesized ZnO nanoparticles (20 µg/mL, 40 µg/mL, 60 µg/mL, 80 µg/mL and 100 µg/mL) against Gram-positive and Gram-negative bacteria: Staphylococcus aureus, Streptococcus pyogenes and Escherichia coli using shake flask method. The obtained results revealed that the bacterial growth decreases with increase in concentration of biosynthesized ZnO nanoparticles. In Addition, Gram-positive bacteria seemed to be more sensitive to ZnO nanoparticles than Gram-negative bacteria. The biosynthesized ZnO nanoparticles showed photocatalytic activity under the UV light enhancing the degradation rate of methylene blue (MB), which is one of the main water-pollutant released by textile industries.