Green-synthesized Y/Co Co-doped TiO₂ nanoparticles from Lagenaria siceraria peel for enhanced photocatalytic and antibacterial performance

This study reports a green synthesis route for pure and Y/Co co-doped TiO₂ nanoparticles using Lagenaria siceraria peel extract as a natural reducing and stabilizing agent. A key contribution of this work is the integration of plant-mediated synthesis with Y/Co co-doping to simultaneously tailor the structural, optical, photocatalytic, and antibacterial properties of TiO₂ within a single framework. X-ray diffraction confirmed that all synthesized samples retained the anatase phase, while peak shifting and strain analysis indicated successful incorporation of Y and Co into the TiO₂ lattice. FTIR, SEM, and EDX analyses further verified changes in bonding environment, reduced particle size, and effective dopant incorporation. UV-Vis spectroscopy revealed progressive band-gap narrowing after co-doping, demonstrating improved optical response compared with pure TiO₂. The crystallite size decreased from 9.77 nm to 8.23 nm, while the optical band gap decreased from 3.35 eV to 3.00 eV after Y/Co co-doping. These modifications led to enhanced functional performance, particularly in the photocatalytic degradation of methylene blue under UV irradiation, where the 3% Y/Co co-doped TiO₂ showed the highest degradation efficiency. The 3% Y/Co co-doped TiO₂ achieved a photocatalytic degradation efficiency of 92.45% after 120 min under UV irradiation. Antibacterial studies against S. aureus and E. coli also demonstrated stronger activity for the co-doped samples, supported by improved minimum inhibitory concentration values. In addition, brine shrimp lethality testing indicated increased biological activity at higher dopant concentration. Overall, the results show that Y/Co co-doping is an effective strategy for tailoring the physicochemical and biological properties of green-synthesized TiO₂ nanoparticles. Among the investigated compositions, 3% Y/Co co-doped TiO₂ exhibited the best overall performance, highlighting its potential for sustainable photocatalytic and antimicrobial applications.