Defect-engineered Ta-doped NiO: Phase evaluation, charge carrier dynamics, and photocatalytic performance

: Pure NiO and Ta doped NiO (3%, 5% and 7%) were synthesized using hydrothermal method and studied for dual function, i.e. photocatalytic degradation of organic pollutant and antibacterial activity. The structural and optical study provide evidence for the successful incorporation of Ta and defect engineering in the NiO lattice. A significant band gap reduction from 3.75 eV (pure NiO) to 2.24 eV (7% Ta-doped NiO) indicates enhanced visible-light absorption and improved charge separation. The optimized 7% Ta-doped NiO showed better photocatalytic activity, with 94% and 83% degradation of Congo Red and phenol respectively under visible light irradiation. Significant antibacterial activity against Escherichia coli and Staphylococcus aureus were also observed. The improvement of dual functions is attributed to defect sites caused by Ta incorporation and to the generation of reactive oxygen species (ROS), which serves as a key factor in both the photocatalytic and the antibacterial activities. This study demonstrates Ta-doped NiO as a promising multifunctional material for environmental and antimicrobial applications.