Characterization and investigation of Bio-inspired ZnO nanoparticles using Prosopis juliflora and Cordia dichotoma for antioxidant and antibacterial applications

Green synthesis of zinc oxide nanoparticles was carried out using Prosopis juliflora bark extract and Cordia dichotoma leaf extract with zinc acetate precursor in the presence of 2 M NaOH solution. The prepared zinc oxide nanoparticles were characterized by Powder X-ray diffraction (PXRD), UV-visible absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), Photoluminescence spectroscopy (PL) to study its structural and optical properties. X-ray diffraction studies confirmed the hexagonal wurtzite phase of the samples with an average crystallite size calculated using Scherrer equation were 38.22 nm and 29.95 nm for Prosopis juliflora mediated zinc oxide (PJZ) and Cordia dichotoma mediated zinc oxide (CDZ) NPs respectively. Williamson-Hall modified form of uniform deformation model (UDM), uniform stress deformation model (USDM) and uniform deformation energy-density model (UDEDM) were carried out to determine crystallite size and micro-strain of ZnO nanomaterials. Tauc’s plot method revealed an energy gap value of 2.86 eV for PJZ sample and 2.95 eV for CDZ sample due to quantum confinement effect. FTIR spectra of the samples were recorded to ascertain the biomolecules involved in the green synthesis. PL spectra showed a strong UV emission peak around 370 nm and a visible broad green emission band at 554 nm which is due to the presence of singly ionized oxygen vacancies. An effective green method to prepare zinc oxide nanomaterials with the efficient antioxidant potential is reported in this study. The current study has also demonstrated that the small particle size of ZnO NPs is responsible for significant antibacterial activity against both gram-positive and gram-negative bacteria.