Crystallographic insights into copper oxide nanoparticles synthesized via a unique sol-gel method: Antibacterial activity and photocatalytic evaluation

A unique sol-gel method was employed to synthesize high-purity copper oxide nanoparticles (CuO NPs) using starch as a natural stabilizer and citric acid as a gelling agent, enabling precise control over nucleation, growth and structural integrity. The synthesized CuO NPs were analyzed utilizing various techniques, including X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), UV–Vis spectroscopy, Dynamic Light Scattering, Zeta potential, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy. XRD analysis validated monoclinic crystal structure with average crystallite size of 21.72 nm and 100 % CuO purity, while SEM revealed uniformly spherical particles. FTIR spectroscopy showed distinct absorption bands at 598.49 cm⁻¹ and 532.83 cm⁻¹ for Cu–O stretching and UV–Vis analysis indicated an absorption peak at 392.08 nm with a 2.01 eV band gap, suggesting sunlight-driven photocatalytic potential. The measured zeta potential of +27.92 mV indicates moderate colloidal stability. The CuO NPs exhibited antibacterial activity against Staphylococcus aureus while no inhibitory effect was observed against multi-drug resistant Escherichia coli. The photocatalytic performance was evaluated through sunlight-assisted degradation of methylene blue, achieving an efficiency of about 88 % within 210 min. This study aims to synthesize high-purity, well-dispersed CuO NPs for precise control over structure and stability. The work’s impact lies in showcasing bio-assisted CuO NPs as efficient sunlight-driven photocatalysts and effective antibacterial agents, highlighting their promise for sustainable environmental and biomedical applications.