The increasing threat of environmental pollution and microbial contamination has intensified research on multifunctional photocatalysis, particularly titanium dioxide (TiO₂), due to its stability, abundance, and oxidative potential. Although it has a wide band gap, rapid charge recombination restricts visible-light activity. Recent advancements in green-synthesised doped TiO₂ nanostructures offer sustainable solutions by integrating plant-mediated synthesis and dopant engineering. This case study has systematically examined the photocatalytic and antibacterial activity of green-synthesised Ag-Co co-doped TiO₂ NPs, emphasising the combined role of silver’s plasmonic activity and cobalt’s band-gap modulation. Individual Ag and Co doping studies show significant band-gap narrowing, from 3.3 eV to as low as 2.4 eV. Dye degradation efficiencies up to 97% under UV light, attributed to enhanced charge separation and oxygen vacancy generation. Although direct Ag-Co co-doping reports remain limited, insights from similar codoped systems (e.g., Ag-Cu, Co-Sr) demonstrate potential for improved charge carrier mobility and dual functionality in photocatalysis and antibacterial applications. The case study further discusses the green synthesis parameters, structural and optical characterisations, and environmental implementations such as water purification and antimicrobial coatings. Finally, it highlights challenges in scalability and biosafety, urging future research toward mechanism-guided design and computational modelling of eco-friendly co-doped TiO₂ NPs for sustainable environmental remediation.

Keywords 

Green synthesis, Ag-Co co-doping, photocatalysis, dye degradation, antibacterial activity, and waste water remediation.