(70dm) Titanium Dioxide–Carbon Nanostructure Composites for Enhanced Photocatalysis

Bioterrorism is a major concern for destabilizing the environmental and physiological well being of the society. Biological warfare agents include bacteria, viruses, fungi and other microorganisms. Available techniques for inactivation of hazardous bioparticulates include use of thermal treatments, chemical disinfectants (chlorine bleach, hydrogen peroxide etc.), germicidal UV (250nm wavelength), photocatalysis (by irradiating TiO2 particles with 350nm wavelength UV light). The shortcomings with the current techniques are that they are effective only in wet or dry state or can damage the substrate on which the inactivation process is carried out. Photocatalysis using titanium dioxide particles can be applied to wet and dry systems and can also be used for surface disinfection. A significant drawback of photocatalysis process is the time required for inactivation, especially for bacterial endospores. Enhancement in photocatalysis can be achieved by reducing the recombination of photon generated electron-hole pairs, with subsequent increase in generation of reactive species, such as hydroxyl radicals. Several attempts have been made to increase the photocatalytic inactivation rate by trapping of either holes or electrons. Carbon nanostructures, such as multi-wall carbon nanotubes are well known electron acceptors and can effectively trap electrons. Novel composite photocatalysts, with modified electronic properties were synthesized by bonding titanium dioxide with carbon nanostructures. The modified photocatalysts were tested for degradation of red dye and shown to be better than the commercially available photocatalyst-Degussa P25. The modified photocatalysts were also tested for inactivation of Escherichia coli and spores of Bacillus cereus and compared with the Degussa P25.