Pyroelectrocatalytic Disinfection Using the Pyroelectric Effect of Nano- and Microcrystalline LiNbO3 and LiTaO3 Particles

LiNbO3 (LN) and LiTaO3 (LT) materials of polar crystal structure exhibit a spontaneous polarization that can be changed by temperature. This phenomenon, commonly known as the pyroelectric effect, leads to the generation of surface charges that in turn are the source for a pyroelectrocatalytic or pyroelectrochemical activity of these materials described in this paper. It can also degradation be regarded as a selective, conversion of thermal via electrical to chemical energy and disinfection based on the pyroelectric effect. In this context, we have investigated the impact of thermally excited pyroelectric LN and LT nano- and microcrystalline powder materials on the bacterium Escherichia coli in aqueous solutions. Powders have been prepared both by milling of commercially available single crystals and by precursor-based solution routes. Our results show that in dependence on the crystallite size and surface area of the pyroelectric particulate material in direct contact with the cells and/or their culture solution, a high antimicrobial activity can be achieved. On the basis of further experimental results of oxidative conversion of the fluorescent dye 2',7'-dichlorofluorescin, a disinfection mechanism including the formation of reactive oxygen species at the pyroelectric particle surface is proposed. The phenomenon is discussed in analogy to the well-established photocatalytic disinfection mechanism.