Synthesis and visible light photocatalytic antibacterial activity of nickel-doped TiO2 nanoparticles against Gram-positive and Gram-negative bacteria

• Ni-TiO2 with visible light induced photocatalytic inactivation of bacteria.
• Photocatalytic inhibition of both Gram-positive and Gram-negative bacteria.
• No bactericidal activity in presence of light and Ni-TiO2 only.

Nanocrystalline anatase titanium dioxide (TiO2) nanoparticles doped with nickel ions (1.0–3.0 mol%) were synthesized by sol–gel method. XRD and XPS showed the proper substitutions of the few sites of Ti4+ ions by Ni2+ ions in titania host lattice. Particle size was estimated from TEM analysis and found in the range of 10–12 nm. UV–vis diffuse reflectance absorption measurement of doped titania nanoparticles shows the optical absorption in the visible region; which also confirms the incorporation of nickel ions in TiO2 crystal lattice. For photocatalytic inactivation four common bacterial pathogens, Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Salmonella abony were illuminated with nickel doped-TiO2 nanoparticles. This shows a substantial decrease in bacterial numbers. The decrease in photoluminescence intensity with increasing dopant content reveals the higher photocatalytic inactivation and lower recombination rate of photogenerated charge carriers. The survival number of all bacteria species is not affected in dark with nanoparticles and in light condition without nanoparticles.

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