RT doctoral thesis
T1 Titania-silica composite materials for self-cleaning applications on monumental stones
A1 Faria Soares Pinho da Silva, Luís Miguel
A2 Química Física
AB Atmospheric pollution has an evidently adverse impact on the aesthetics ofurban buildings and structures. Thus, the synthesis of photocatalysts capableof removing pollutants deposited on the surface of stone and other buildingmaterials is an interesting challenge to researchers. In the work undertaken forthe Doctoral Thesis presented, mesoporous TiO2-SiO2 composites that havephotocatalytic activity have been synthesized by mixing ethoxysilaneoligomers and TiO2 nanoparticles in the presence of a non-ionic surfactant (noctylamine).The products synthesized have a clear practical application onbuildings and other monumental heritage structures since they can be appliedoutdoors by means of a simple and low-cost process. The resultingnanomaterials give self-cleaning properties and create crack-free effectiveadhesive coatings for exterior stone surfaces. In addition, they improve themechanical resistance of the stone. Another important advantage of thesenanocomposites is that they substantially improve protection against saltcrystallization degradation processes.By using of N2 physisorption, atomic force microscopy and electrontomography, together with 3D reconstructions, we have been able to concludethat the texture of the nanocomposites synthesized is a key parameter forcontrolling the photocatalytic activity. Specifically, we find that n-octylaminecreates a mesoporous SiO2 structure within which TiO2 nanoparticles areembedded, and that TiO2 and SiO2 are present in separate domains in the bulkof the material. The mesoporous structure enhances the activity of thematerial by improving the access of light to photoactive sites.We optimize the effectiveness of these photocatalysts on stone by varying theloading and particle size of TiO2 in the starting sol. We find that theintegration of around 4% w/v content of TiO2 nanoparticles into the SiO2network significantly improves their effectiveness due to a higher availabilityof photoactive sites. For higher TiO2 loadings (10% w/v), photocatalyticactivity decreases because the porous volume is drastically reduced and accessto photoactive sites is more restricted. Regarding the effect of particle size, weobserve that larger and sharper TiO2 nanoparticles enhance the photocatalyticactivity.
YR 2013
FD 2013-08-02T00:00:00Z
LK http://hdl.handle.net/10498/15521
UL http://hdl.handle.net/10498/15521
LA eng
DS Repositorio Institucional de la Universidad de Cádiz
RD 21-sep-2026