Biogenic production of eco-friendly Arjuna-ZnO NPs for sunlight-activated efficient degradation of organic dyes of high commercial usage

Abstract

The present study describes an environmentally benign biological method for the production of zinc oxide nanoparticles (ZnO NPs) by blending water-based leaf extract from a sustainable bio-source, the Arjuna tree, under ambient conditions. Aqueous leaf extract comprised of different reducing agents appeared as the precursor for phytofabrication, and zinc nitrate hexahydrate (ZnNO₃·6H₂O) acted as a zinc source. The phytofabricated Arjuna-ZnO NPs had a hexagonal shape with an average size of 31.14 nm, as revealed by HR-TEM, FE-SEM micrographs, and XRD patterns. The FESEM-EDS micrograph and the XRD patterns also revealed the elemental composition, phase purity, and crystalline nature of phytofabricated Arjuna-ZnO NPs. The initial formation of ZnO NPs was confirmed by absorption maxima at approximately 376 nm and Zn-O stretching vibrations at 520 cm⁻¹ using UV–VIS and an FT-IR spectrophotometers, respectively. The aqueous extract of Arjuna leaf was also analysed using FT-IR spectrophotometer to identify the functional groups of bioactive substances that participated in the reduction and encapsulation processes. The efficacy of the Arjuna-ZnO NPs was assessed in terms of their ability to photocatalyzed on three noxious dyes, methylene blue (MB), methyl orange (MO), and congo red (CR), for high commercial and industrial usage. The phytofabricated Arjuna-ZnO NPs were photoactive and proved highly efficient and effective nano-photocatalysts for the photodegradation of three dyes, MB, MO, and CR, under natural sunshine, underscoring their potential for effective remediation of environmental pollutants. The degradation process adhered to pseudo-first-order kinetics in terms of adsorption kinetics.