Green synthesis of zinc oxide nanoparticles using Catharanthus pusillus: Characterization, antibacterial, cytotoxicity of A549 cells, and photocatalytic degradation of Eosin (E) dye

The current study examines the green synthesis of zinc oxide nanoparticles (ZnO NPs) using an aqueous extract of Catharanthus pusillus , which is an eco-friendly and sustainable approach. The produced ZnO NPs were investigated by Ultraviolet-Visible Diffuse Reflectance Spectrometer (UV/DRS), Fourier Transform-Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy, Field Emission-Scanning Electron Microscopy (FE-SEM) & Energy Dispersive X-ray (EDX) and Thermogravimetric analysis (TGA). The surface plasmon resonance (SPR) was measured using UV/DRS at 347 nm and bandgap energy 3.12 eV by Tauc's plot. FT-IR spectral analysis confirms the presence of tannins, carboxyl, and phenolic functional groups. The XRD pattern of CP-ZnO NPs signifies a crystalline hexagonal shape, and the average size of the particles was about 18.5 nm. FE-SEM was used to evaluate the surface shape and structure of the ZnO NPs and the EDX spectrum, which showed a distinctive metallic Zinc peak at 8.70 keV. TGA demonstrated excellent thermal stability with only 13.79 % weight loss up to 800 °C. ZnO NPs derived from C. pusillus showed significant antibacterial properties against human pathogens Enterococcus faecalis (25 ± 1.04 mm), Staphylococcus aureus (18 ± 0.82 mm), Candida albicans (19 ± 0.94 mm), Escherichia coli (24 ± 0.96 mm) and Klebsiella pneumoniae (22 ± 1.01 mm) at 100 μg/mL. Cytotoxicity assay reveals green synthesis of CP-ZnO NPs with IC 50 values of 36.63 μg/mL against the A549 lung cancer cell line at 100 μg/mL. Additionally, synthesized ZnO NPs of photocatalytic activity were evaluated by degradation of Eosin (E) dye, and degradation of 82 % at 180 mins. • This is the first report on green-synthesized Zinc oxide nanoparticles (ZnO NPs) using Catharanthus pusillus leaves extract. • Characterization confirmed spherical morphology by FESEM-EDX. • ZnO NPs exhibited strong antimicrobial efficacy against bacteria. • Significant cytotoxicity observed against A549 lung cancer cells (IC 50 = 36.63 μg/ml). • Synthesized NPs showed 82 % photocatalytic degradation of eosin dye under sunlight.