Study on the effect of the concentration of Hibiscus sabdariffa extract on the green synthesis of ZnO nanoparticles

Abstract

This work evaluates the effects of different concentrations of Hibiscus sabdariffa flower (Jamaica) extracts on the green synthesis of zinc oxide (ZnO), for the photocatalytic degradation of methylene blue (MB). Zinc nitrate is used for the synthesis of ZnO as a source of the zinc ions. Extracts of 1%, 4% and 8% (% weight-volume) of Hibiscus sabdariffa, in an aqueous medium, were used as reducing and stabilizing agents. In FTIR characterization, the ZnO bond was observed at 618 cm−1. By means of XRD, the material was observed to have a hexagonal crystalline phase (Wurzite). Through XPS, the energy values of 1022 eV for Zn and 531 eV for O were observed, showing the chemical state of Zn+2. The morphology of the ZnO nanoparticles (NPs) varies in its semicircular shape and size distributions depending on the extract used, which range from 30 to 8 nm. The values of the band gap decreased from 2.96 to 2.77 eV as the concentration of extract increased. These materials presented good photocatalytic activity, degrading 97% of MB in 150 min, which are efficient results comparable to ZnO NPs green synthesized via other extracts and other methods.