Ti/TiO2 nanoneedles/AgBr heterojunction architecture as antifouling surfaces

Metallic surfaces endowed with antifouling characteristics are crucial in biomedical devices, frequently-contacted surfaces, food and cosmetic packaging, etc. Here, flexible Ti foil has been employed to grow TiO₂ nanoneedles, known for their exceptional properties, using a modified hydrothermal synthesis method. The established hydrothermal synthesis of TiO₂ nanoneedles employs concentrated HCl solution that completely digests the Ti foil. In the present study, concentration of HCl was lowered systematically to unearth the optimal conditions for obtaining hydrothermally grown TiO₂ nanoneedles. To make the surfaces antifouling under dark–light dual-mode conditions, deposition of varying loadings of photosensitizing AgBr was made. These nanostructures were characterized using field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV diffuse reflectance spectroscopy, respectively. Antibacterial efficacy of TiO₂/AgBr heterojunctions was evaluated under both dark and visible light conditions against two representative gram-negative bacteria, Pseudomonas fluorescens and Escherichia coli DH5-α. Notably, TiO₂ nanostructures coated with 50 mg ml⁻¹ of the AgBr precursor achieved complete bacterial clearance for P. fluorescens within 180–240 min in the dark, while a comparable activity was observed within 90–120 min under light conditions. In the case of E. coli DH5-α, even a lesser loading of 30 mg ml⁻¹ was more effective. The crystal violet assay employing biofilm-forming P. fluorescens showed increased biofilm inhibition with higher AgBr loadings. The findings of this study highlight the multifunctional potential of the AgBr-loaded TiO₂ nanostructure as a dual-mode antibacterial coating on metallic surfaces.