Colloidal Nanocrystalline Semiconductor Materials as Photocatalysts for Environmental Protection of Architectural Stone (original) (raw)
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Photocatalytic nanostructured TiO2 for protection of porous and compact stone
The enhanced photocatalytic activity for degradation of a wide range of pollutants makes nanostructured TiO2 an ideal candidate for self-cleaning coatings. The deposition of different types of TiO2 nanocrystalline coatings on stone has been investigated in order to test the surface protection and self-cleaning abilities of the nanostructured materials. TiO2 nanocrystals with controlled size, shape and surface chemistry have been prepared by using two distinct synthetic approaches, namely colloidal synthesis by hot injection and hydrothermal nanophase crystallisation. Two different types of stones, possessing different porosity, namely porous calcarenite and a compact limestone have been selected, being both widely used in South Italian monuments and building relevant for cultural heritage. The physical properties of coated and uncoated stone surfaces, respectively, have been investigated, and colour, wettability and stability of the coatings have been checked. The self-cleaning prop...
Environmental science and pollution research international, 2013
Abstract Self-cleaning photocatalytic coatings for biocalcarenite stones, based on TiO2 nanoparticles obtained by sol–gel processes at different pH values and also adding gold particles, have been investigated. The selected test material is a biocalcarenite named “pietra di Lecce” (Lecce stone), outcropping in Southern Italy. Scanning electron microscopy with energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, and Raman investigations were carried out to characterize the TiO2 nanoparticles and coatings. Nanocrystalline anatase and, to a lesser extent, brookite phases are obtained. Photocatalytic activity of the TiO2 sols and of the coatings on “pietra di Lecce” was assessed under ultraviolet irradiation, monitoring methyl orange (MeO) dye degradation as a function of time. To evaluate the harmlessness of the treatment, colorimetric tests and water absorption by capillarity were performed. The results show good photodegradation rates for titania nanosols, particularly when putting in Au particles, whereas a satisfactory chromatic compatibility between the sol and the surface of the calcarenite is found only without Au addition. Highlights Sols of nanocrystalline titania at different pH values and with Au particles were prepared and characterized. Satisfactory photodegradation of MeO by the sols in solution and on calcarenite-coated surfaces is obtained. The addition of Au particles improves the photodegradation activity but gives poor chromatic results on “pietra di Lecce.”