Biomolecules Influences on the Physiochemical Characteristics of ZnO Nanoparticles and Its Enhanced Photocatalysis under Solar Irradiation

Due to the versatility as reducing, capping, and complexing properties of naturally occurring green chemical compounds found in medicinally significant plants, they are now being used more frequently in synthesizing metal oxide nanocrystals. These compounds are considered the most effective and ecologically responsible choice. Moreover, in contrast to conventional chemical approaches, using plants’ secondary metabolites, such as bioactive compounds sourced from plants, offers an environmentally sound way to synthesize ZnO NPs. In this research, the ZnO NPs were synthesized through chemical and green methods using the medicinal valuable W. Tintoria leaf extract at (10 mL, 20 mL, and 30 mL) extract concentrations. X-ray diffraction, Fourier Transform infrared spectroscopy, field emission scanning electron microscope and UV–visible spectroscopy were used to investigate the structural, functional, morphological, optical, and photocatalytic properties of the ZnO NPs. According to a structural investigation, their crystallite size decreased from 13.2 to 5.9 nm with the addition of biomolecules. It is evident from the vibrational analysis that the phenolic, flavonoid, and alkaloid groups are found in the bio-ZnO NPs compared with chem-ZnO NPs. The plant-biomolecules controlled the morphology, size, and dispersion of the particles well enough, according to morphology characterization. And the estimated energy band gap was increased to 2.78 eV from 2.98 eV, as validated by the UV–visible report. The chemical and 30 mL of bio-synthesized ZnO NP-based Rhodamine B dye photodegradation studies show enhanced degradation at 95.70