Biocidal activity of ZnO NPs against pathogens and antioxidant activity - a greener approach by Citrus hystrix leaf extract as bio-reductant

Leaf extract-mediated bio-synthesis of nanoparticles has received significant attention due to low cost, feasibility, and lack of harmful solvents or toxic inorganic reducing agents. The synthesized ZnO NPs exhibited crystallite size of 17 nm, hexagonal phased wurtzite structure with the corresponding Eg value of 3.2 eV. X-Ray Diffraction and UV-DRS results imply typical ZnO NPs structural formation with slightly heightened band gap energy. Functional group, especially Zn-O bond vibrations at 880 and 432 cm−1 are identified with aid of Fourier Transform Infrared spectroscopy (FT-IR) operating in-between 4000 and 400 cm−1 respectively. Results of FESEM and HR-TEM declare spherical shaped, bush-like morphology with particle sized 26–69 \ub1 0.5 nm. The EDX spectrum results convey the mass percentage of Zn as 70.43% and O as 14.19%. SAED pattern of ZnO NPs demonstrates good crystalline high intense lattice planes (101) with an interplanar spacing of 0.36 nm are, well consistent with obtained XRD results. The results showed Citrus hystrix leaf extract mediated ZnO NPs deliver prominent antibacterial activities against Escherichia coli and Staphylococcus aureus and antifungal activity against Candida albicans and Aspergillus niger. ZnO NPs also possess a good antioxidant activity. An excellent IC50 value of 133.9 μg/ml is obtained for the synthesized ZnO NPs