Photocatalytic activity of ZnO and TiO2 'nanoparticles' for use in cement mixes

Commercial titanium and zinc nanoparticle suspensions were tested for use in self-cleaning and protection of built cement structures. The methylene blue decolorization test, assessment of activity against the fungus Cladosporium sp. in laboratory cultures, and accelerated testing for anti-fungal activity on gypsum panels all showed that the Zn particles were more effective than TiO2 (both at 4%). The commercial “nanoparticle” suspensions were shown, by scanning electron microscopy and electron dispersive spectroscopy, to have a size range outside that required for classification as nanoparticles and should more correctly be characterized as microparticles. The large surface area of these particles, together with their obvious photocatalytic activity shown by the methylene blue test, as well as their apparent inherent antimicrobial activity, indicate that the ZnO particle suspension is more effective and appropriate for inhibition of fungal growth on calciferous building materials than the more commonly used TiO2.