Enhanced inactivation of bacterial spores by atmospheric pressure plasma with catalyst TiO₂

Both atmospheric pressure plasma and photo-catalyst metal oxide titanium dioxide (TiO₂) are well known for their microorganism inactivation and chemical material decomposition abilities. In this work, radio-frequency atmospheric pressure plasma and TiO₂ are used together to inactivate Bacillus subtilis spores that have a very high degree of environmental resistance to ultra-violet (UV) photons and heat. The combinational use of the plasma and TiO₂ demonstrates an enhanced performance of B. subtilis spore inactivation by showing a decrease in the decimal reduction time of as large as 40% compared with the use of plasma alone. A significant increase of hydroxyl (OH) and excited oxygen atomic emission line (O I) intensities in the presence of TiO₂ suggests that the atmospheric pressure plasma assisted by TiO₂ is very effective at generating reactive oxygen radicals, which is known to be a dominant factor in bacterial spore inactivation. Possible TiO₂ activation mechanism by the plasma is investigated.