Green synthesis of emerging ZnO and Ca-doped ZnO nanoparticles towards optical, magnetic properties and its antibacterial application

Abstract

A green synthesis method is adopted to prepare emerging low cost ZnO (ZNP) and Ca substitute ZnO nanoparticles (CZNP) using Psidium guajava fruit (PGF) extract as an effective reducing and capping agent. An X-ray diffraction study of the synthesized nanoparticles revealed that they have a hexagonal wurtzite structure. The elemental compositions and oxidation states of ZNP and CZNP surfaces are quantified. The HRSEM image shows the nano-flake like structure of the synthesized nanomaterials ZNP and CZNP samples. The elemental compositions were identified using EDAX spectra. From the Raman spectra, the low wavenumber region of 2nd order Raman modes at 341 and 346 cm-1 were ascribed to the difference E2 high-E2 low. Kubelka–Munk (K–M) method is used for estimating direct band gap and it is 3.3 eV and 3.04 eV for ZNP and CZNP respectively. Due to the zinc and oxygen vacancies, six different bands were observed in the photoluminescence spectra. The TG analysis was observed 5.6% of weight loss for ZNP and 5.8% of weight loss for CZNP sample. The Magnetization–Field (M–H) hysteresis curves revealed the appearance of diamagnetic behavior at room temperature. The asfabricated pure ZnO and Ca-doped ZnO nanoparticles were evaluated for the antibacterial activity. The Ca substituted ZnO sample showed higher antibacterial activity than pure ZnO sample.