, Volume 18, Issue 1, pp 289-294

An ESR study on the photoreactivity of tio2 pigments

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The photoreactivity of commercial TiO2 pigments has been studied by monitoring the generation of radicals at the TiO2- water interface upon illumination with ultraviolet light. The ESR spin-trapping technique has been employed, using 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) as spin trap. In illuminated TiO2 dispersions the only radical species identified has been the OH. The amount of radicals generated was found to depend upon the surface properties of the pigment, such as impurities and surface treatments, and upon the oxygen concentration in the slurry. A feasible mechanism for radical generation, involving O2 adsorption is proposed. The initial rate of radical generation has been found to be in good agreement with other methods commonly used to characterize the photostability of paints.