Modulating the structural and optical properties of CuO nanoparticles through experimental and computational study towards antioxidant and antibacterial applications

Abstract Antibiotic resistance is a major health concern, emphasizing the need for alternatives like metal oxide nanoparticles (MONPs). This study employs the precipitation method to synthesize copper oxide nanoparticles (CuO NPs) using copper chloride and sodium hydroxide. X-ray diffraction (XRD) confirms a well-crystalline monoclinic structure, while Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) reveal irregular nanorod-like shapes with diameters of 130–200 nm for CuO NPs(1) and 50–100 nm for CuO NPs(2). Energy Dispersive x-ray Spectroscopy (EDX) confirmed the existence of copper (Cu) and oxygen (O), while Fourier Transform Infrared Spectroscopy (FTIR) revealed a peak corresponding to the Cu–O stretching vibration. The CuO NPs demonstrate widened band gaps of 3.38 eV for CuO NPs(1) and 3.57 eV for CuO NPs(2), significantly higher than that of bulk CuO. UV–vis analysis further quantifies optical parameters, including absorption coefficient, transmittance, and reflectance, crucial for optimizing optical components in technological applications. Density Functional Theory (DFT) calculations indicate that CuO has an antiferromagnetic ground state with a local magnetic moment of 0.675 μ B and an indirect band gap of 1.42 eV. Combining CuO nanoparticles (NPs) with conventional antibiotics enhances the effectiveness against Bacillus subtilis and Klebsiella pneumoniae , while their dose-dependent antioxidant activity, comparable to ascorbic acid, suggests potential in treating degenerative diseases Our results suggest that both CuO NPs can be extensively used as antioxidant and antibacterial agents.