Ficus religiosa Fruits-mediated Synthesis of CeO2 Nanoparticles and CeO₂/CuO Nanocomposites: Structural Insights and Antimicrobial Efficacy

A novel, simple, and inexpensive technique, chemical coprecipitation, was employed to produce CeO2 nanoparticles and CeO2/CuO nanocomposite. It entailed reacting dehydrated metal nitrate salts with an aqueous extract of Ficus religiosa. The CeO2 and CeO2/CuO solids were identified by X-ray diffraction (XRD), FTIR, and transmission electron microscopy (TEM). The diffraction peaks of the CeO2 and CeO2/CuO revealed cubic and monoclinic structures, respectively, with average crystallite sizes of 20.5 and 26.8 nm, based on the XRD data. TEM examinations show that the mean sizes of CeO2 and CeO2/CuO particles were (39.8 and 66.5 nm, respectively). These results imply negligible agglomeration. This study evaluated the antimicrobial efficacy of CeO2/CuO nanocomposite and CeO₂/CuO NPs against bacterial and fungal pathogens. The nanocomposite exhibited superior activity, producing larger inhibition zones (Bacillus subtilis: 26 mm; Candida albicans: 28 mm) compared to CeO₂ NPs and the standard drugs ciprofloxacin (as antibiotic) and nystatin (as antifungal). MIC and MBC/MFC assays confirmed stronger potency, particularly against Gram-positive bacteria and C. albicans. Time–kill kinetics revealed complete eradication of B. subtilis and K. pneumoniae within 180 min, while partial survival occurred in S. aureus and S. typhi. Both materials were inactive against Aspergillus niger, indicating selective but potent antimicrobial effects.