Green synthesis of ZnO nanoparticles using Aphloia theiformis leaf extract from Madagascar: Characterisations

Abstract

We report a sustainable green synthesis of zinc oxide nanoparticles (ZnONPs) using an aqueous extract of Aphloia theiformis, an indigenous medicinal plant from Madagascar. The phytochemicals in the extract act as both reducing and stabilising agents. Zinc nitrate hexahydrate (Zn(NO3)2.6H2O) was used as the precursor, and synthesis was carried out by a simple thermal process at 100 °C, followed by calcination at different temperatures to improve crystallinity. The nanoparticles were thoroughly characterised by SEM EDX, FTIR, XRD, Raman spectroscopy, and UV–Vis diffuse reflectance spectroscopy. The ZnONPs exhibit a quasi-spherical morphology with a relatively narrow size distribution (20–40 nm) and a pure hexagonal wurtzite phase, free of detectable secondary phases. The FTIR analysis confirms that polyphenols and flavonoids play a key role in the reduction and stabilisation of the nanoparticles. Raman spectroscopy reveals a dominant E₂(high) mode at 437 cm⁻¹, which is indicative of high crystallinity. Optical measurements show a band gap of 3.12–3.25 eV, consistent with semiconducting zinc oxide (ZnO). To the best of our knowledge, this is the first report describing the use of Aphloia theiformis leaf extract for the green synthesis of ZnONPs. This study introduces Aphloia theiformis as a novel bioresource for the green synthesis of nanomaterials, opening new avenues for environmentally sustainable nanotechnology.