Mesoporous TiO₂ Nanoparticles Containing Ag Ion with Excellent Antimicrobial Activity at Remarkable Low Silver Concentrations

Mesoporous Ag–TiO₂ nanoparticles with TiO₂ homogenous anatase crystalline phase was synthesized using a one-pot sol–gel method. The sample was calcined at 100 °C and characterized by XRD, HR TEM, EDAX, IR spectroscopy, DRS, N₂ adsorption–desorption isotherm and Brunauer–Emmett–Teller (BET) analysis. The BET surface area of the sample was 266 m²/g and the crystallite size as calculated using Scherrer formula was 3.76 nm. The Ag–TiO₂ nanoparticles exhibited excellent antimicrobial activity against representative Gram-positive and Gram-negative bacterial cultures and Candida albicans. Complete inhibition of microorganisms was achieved at a very low Ag–TiO₂ concentration, in the range of 1.0 to 20 μg/mL (effective Ag concentrations were 11.7 to 234 ppb) in less than 2 h under ambient conditions, without the requirement of photoactivation. Silver ion release studies showed that about 18% of silver ions were present in solution. Thus, it may be inferred that the antimicrobial activity is due to Ag ions released from the TiO₂ matrix. The mesoporous nature and antimicrobial activity at low concentrations without photoactivation are important aspects which make this material an excellent candidate for potential application as disinfectant and/or antimicrobial agent.