Impact of Hibiscus extract on the structural and activity of sonochemically fabricated ZnO nanoparticles

Abstract

In the present work, a green chemistry route for synthesizing zinc oxide (ZnO) nanostructures using Hibiscus extract as a stabilizing and a reducing agent under ultrasonic energy. The ZnO nanostructures obtained without (ZnO) and with Hibiscus extract (ZnO-H) were characterized to explore the effect of the plant extract on ZnO structure, morphology, and photocatalytic activity. The X-ray diffraction (XRD) data showed a reduction in ZnO crystallite size from 40 to 31 upon treatment with the Hibiscus extract. In addition, thinner ZnO nanorods were formed due to the use of the extract, as perceived from the scanning electron microscopic (SEM) analysis. The N2 physisorption data revealed that surface area and porosity increased with Hibiscus extract treatment, where the SBET increased from 4.0–10.0 m2. g−1, while the pore size and pore volume increased from 0.021 to 0.06 cm3. g−1 and 12.5–18.2 nm, respectively. The X-ray photoelectron spectroscopy (XPS) confirmed the formation of ZnO with minor shift in the binding energies as an effect of using the extract. As a consequence of band gap narrowing, surface area and porosity increase, the ZnO-H nanostructures exhibited better photocatalytic degradation performance for the methylene blue (MB) dye. The high efficiency for MB degradation was reflected by the higher photodegradation percentage and greater pseudo-first-order kinetics rate constant. The radical scavenger study revealed that superoxide radicals played a major role in the photodegradation of MB, especially over ZnO-H. The inexpensive, simple, eco-friendly approach of the previously described protocol for “one-pot” synthesis and alteration of ZnO characteristics could be expanded to fabricate other kinds of nanoparticles and to extend their utility in different areas of nanotechnology.