Singular Effect Of Crystallite Size On The Charge Carrier Generation Andphotocatalytic Activity Of Nano-tio2

Photocatalytic processes on nanometric titanium oxide have been extensively studied from the stand-point of solar energy utilization and remediation of water and gas streams polluted with organicmolecules. It is accepted that TiO2crystallite size and crystalline phase are among the parameters involvedin the control of the photocatalytic activity. However, while changing the catalyst nanoparticle size, otherattributes important to assess photocatalytic activity may be modified, making thus difficult to define towhich extension the photoactivity changes are related only to size differences. Therefore, aiming at study-ing exclusively the size effect and the parameters directly related to size on the photocatalytic activity ofnanometric TiO2, in this work it was explored a method to synthesize TiO2nanoparticles with controlledsize, highly similar morphology and comparable phase and degree of crystallinity. A set composed offour samples of nano-TiO2loaded porous Vycor glass, each sample having a specific TiO2nanoparticlesize, was tested on the photoactivated process of depollution of solutions of salicylic acid and methyleneblue. The photocatalytic activity observed for the organic compounds tested was inversely proportionalto the TiO2nanoparticle size. An opposite tendency was observed for the generation of OH radicals dur-ing photocatalyst illumination, as more radicals are formed on the material containing the larger TiO2nanoparticles. Results of this study suggest that photocatalytic activity of nano-TiO2is less favored bythe enhanced light absorption response and the higher generation of oxidative species observed for thelarger nanoparticles. 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