Antibacterial activity and photocatalytic oxidative performance of zinc oxide nanorods biosynthesized using Aerva lanata leaf extract

Abstract

A simple biosynthesis process was followed for preparing zinc oxide nanorods (ZnO NRs) using Aerva lanata leaf extract as reducing and structure directing agent. The FE-SEM images displayed presence of ZnO NRs with a mean diameter of ∼100 nm. The EDX spectrum ascertained purity of the ZnO NRs. The UV–Vis spectrum exhibited characteristic absorption band of ZnO NRs and their band gap was found out as 3.24 eV. The XRD pattern indicated wurtzite crystalline structure and hexagonal phase of the ZnO NRs with good crystallinity. The FTIR band noticed at 534.34 cm−1 due to the characteristic stretching of Zn–O bond disclosed purity of the ZnO NRs. The antibacterial activity of the ZnO NRs was assessed against selected Gram-positive and Gram-negative bacteria. Among them, highest antibacterial activity was detected against E. coli (ZOI: 8 mm vs 100 μL ZnO NRs) and S. aureus (ZOI: 7 mm vs 100 μL ZnO NRs). Besides, the ZnO NRs were used as photocatalyst towards oxidation of methylene blue dye under natural sunlight illumination. The rate constant for the ZnO NRs and chemically synthesized ZnO NPs towards photocatalytic oxidation of MB dye was found out as 11.28 and 7.80 × 10−4 s−1, respectively. The thermal stability and photostability of the ZnO NRs were confirmed by thermogravimetric analysis and photocatalytic recycling experiments. The proposed mechanisms for the inferior antibacterial activity and significant photocatalytic performance exhibited by the ZnO NRs are discussed in detail.