Green synthesis and enhanced photocatalytic performance of metal-doped CuO nanoparticles for efficient degradation of organic pollutants and biological applications

A significant challenge in nanoscience is the development of sustainable and eco-friendly synthesis approaches. Among various methods, the green synthesis of metal-doped CuO nanoparticles (M-CuO NPs) using plant extracts offers distinct advantages over conventional physicochemical techniques. In this study, Co-, Ni-, and Zn-incorporated CuO NPs were fabricated by utilizing the extract of Tecoma stans leaves. The structural, optical, surface, and functional characteristics of the fabricated NPs were systematically characterized by employing various physicochemical techniques. X-ray diffraction (XRD) analysis verified the monoclinic crystal structure of all M-CuO NPs. Through the utilization of Tauc plots, it was found that the values of the optical band gap (E g ) for Co-CuO, Ni-CuO, and Zn-CuO were 2.45, 2.74, and 3.01 eV, respectively. The use of Fourier transform infrared (FTIR) spectroscopy was able to confirm the existence of functional groups that were related to the NPs fabricated. The quasi-spherical morphology of the Co-CuO NPs was validated through high-resolution transmission electron microscopy (HR-TEM). Co-CuO NPs had higher photocatalytic activity when exposed to UV light for the degradation of paracetamol (PCM) and methylene blue (MB) among the samples that were fabricated. Under optimal conditions (pH = 5, starting concentration = 10 mg/L, and catalyst dose = 10 mg), the degradation efficiencies reached 96.3% for PCM and 95% for MB within 120 min. Based on the comparative physicochemical characterization and photocatalytic performance, Co-CuO NPs were identified as the most promising material and were therefore selected for subsequent biological investigations. In addition, the antimicrobial activity of Co-CuO NPs was found to be substantial against Escherichia coli (E. coli) , Proteus vulgaris (P. vulgaris) , Bacillus subtilis (B. subtilis) , and Staphylococcus aureus (S. aureus) . The MTT test was utilized to assess the cytotoxic effects of Co-CuO NPs on the A549 cell line. The results of this evaluation revealed an IC₅₀ value of 35.01 µg/mL following a 24 h exposure. Additionally, the DPPH assay was exploited to test the antioxidant activity and the results were compared to those obtained from the standard L -ascorbic acid. Similarly, the results of anti-inflammatory activity of Co-CuO NPs were compared with the standard drug diclofenac.