Fabrication and structural characterisation of La 2 O 3 /CuO nanocomposite for biological and dye water treatment applications

The present study reports the facile and environmentally benign synthesis of La2O3, CuO, and a La2O3/CuO nanocomposite via a solution combustion method using gallic acid as a sustainable green fuel. Unlike previous studies, this work systematically correlates the heterostructure formation with photocatalytic degradation of Tartrazine dye and biological activities, providing a comprehensive evaluation of the multifunctional performance of the La2O3/CuO nanocomposite. The structural, morphological, and optical properties of the synthesised materials were characterised using XRD, SEM, EDX, FTIR, UV–Vis, PL, TEM, and XPS. XRD confirmed the formation of hexagonal La2O3 and monoclinic CuO phases, while the composite exhibited successful integration of both oxides without impurity phases. The La2O3/CuO nanocomposite showed enhanced optical absorption and a reduced effective band gap relative to the individual oxides, suggesting improved charge-transfer behaviour. The photocatalytic performance was evaluated using the Tartrazine (TZ) dye under UV irradiation, where the La2O3/CuO nanocomposite achieved a superior degradation efficiency of 90.19% within 60 min, significantly higher than that of pristine La2O3 and CuO. Kinetic analysis revealed pseudo-first-order reaction behaviour with an enhanced rate constant (0.03873 min−1). Scavenger studies confirmed that photogenerated holes and superoxide radicals play dominant roles in the degradation process. In addition, the composite exhibited improved antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa, enhanced antifungal activity against Aspergillus niger, and moderate antioxidant performance. The enhanced multifunctional performance of the La2O3/CuO is attributed to synergistic interfacial interactions, efficient charge separation, and increased generation of reactive oxygen species (ROS).