Zinc oxide (ZnO) nanoparticles (NPs) are gaining more interest due to their multifunctional and biological properties. Herein, we synthesized ZnO NPs and characterized their optical and electrical properties for application in catalysis and optoelectronic devices and potential biomedical applications. The synthesis of ZnO NPs was performed via a precipitation method, and their crystallinity, crystal structure, crystal phase purity, particle morphology, and size distribution were characterized via X-ray diffraction and transmission electron micrographs. The crystal ligand environment, chemical purity and chemical oxidation states were studied by Raman, infrared and X-ray photoelectron spectroscopy. Thermal stability and residual matter decomposition were studied by thermogravimetric analysis. Furthermore, the optical energy band gap was investigated by UV-Vis absorbance spectroscopy. Similarly, the photocatalytic properties were also studied by rhodamine B degradation under UV light irradiation. Biological activities, such as antibacterial and cytotoxicity potentials, were explored. The synthesized ZnO crystallized in a hexagonal wurtzite structure with an average crystallite diameter of 43 nm. Various anion ligands around Zn2+ in wurtzite were confirmed. The sample showed a 3.26 eV optical energy gap with a high photocatalytic activity of 99.5% in 70 min. The synthesized NPs showed high antibacterial activity against Pseudomonas aeruginosa and less cytotoxicity to kidney cancer cell lines (A498). From this finding, we suggest that the prepared ZnO NPs could be used for various biomedical applications. © 2021 Elsevier B.V.