Photocatalytic inactivation of Escherichia coli using doped titanium dioxide under fluorescent irradiation

One of the challenges that the scientific community faces is to increase the activity of the photocatalyst TiO2 on exposure to indoor illumination. In this paper, the photocatalytic activity of TiO2 commercial powders doped with Pt, C and N under irradiation with fluorescent light was studied using Escherichia coli (ATCC8739). Standardized cell suspensions were inoculated onto filters on which powders were immobilized. Irradiation encompassed visible light at 2.70-3.99 W m(-2), and UV at 0.05-0.12 W m(-2) intensity. E. coli inactivation as a function of time was monitored for up to 120 min. The bacterial count was reduced by up to 3.3 +/- 0.1 log at a loading of 4.2 gm(-2) using Pt (0.2 wt%) doped TiO2 within 2 h of fluorescent light exposure. TiO2 doped with 0.85 wt% C and 0.49 wt% C demonstrated lower antibacterial activity, with the highest inactivation (1 log and 1.2 +/- 0.2 log, respectively) at a loading of 1.6 g m(-2). There was no antibacterial activity demonstrated using N (0.1 wt%) doped TiO2. In general, lower TiO2 concentrations were more effective. It is proposed that increased physical contact between the nanoparticles and the bacterial cells, revealed by scanning electron microscopy, enhanced photocatalytic activity, and this interaction should be considered in additional to other properties of photocatalysts, if antibacterial properties are required. (C) 2013 Elsevier B.V. All rights reserved.