Phytochemical-mediated synthesis of ZnO–PbO nanocomposite using Centella asiatica extract with photocatalytic and antibacterial efficiency

The study reports the synthesis of a ZnO–PbO nanocomposite through a phytochemical-mediated precipitation route using Centella asiatica leaf extract as a natural reducing and stabilizing source. The synthesis proceeded without external alkali or pH adjustment. X-ray diffraction confirmed a polycrystalline ZnO–PbO–PbO2 system with partial Zn incorporation, supported by Rietveld refinement and EDS mapping. SEM and TEM revealed rod-like aggregates and fine spherical nanocrystals corresponding to secondary and primary structural levels. FTIR showed characteristic Pb–O and Zn–O bonds, and the composite displayed visible-light activity. The photocatalytic degradation of eosin yellow reached 94% under sunlight following pseudo-first-order kinetics, aided by H2O2 in a Fenton-like process. The nanocomposite also showed antibacterial activity against both Gram-positive and Gram-negative strains with greater inhibition toward Staphylococcus aureus and Pseudomonas aeruginosa. The use of plant extract avoided toxic reagents, but the presence of PbO requires safe recovery to prevent environmental contamination.