Surface segregation of MgO on TiO2 nanoparticles and its relationship with particle phases stability

Abstract

The size control in nanoparticles is one of the biggest challenges in the development of these new materials. The prediction of the final particle size and their respective cristalline phase allows these materials to be used in specific applications, such as photocatalysis, solar cells and self-cleaning surfaces. MgO-doped titania is specially relevant since it enhances the already intrinsic photocatalytic efficiency of the nanometric TiO2. It is expected to verify the ocurrence of surface segregation of the MgO on the nanometric TiO2 prepared through the organic precursors method, and to observe how this phenomenon affects both the particle size and stability of the TiO2 polymorphs. To accomplish that, TiO2 will be synthesized with different MgO molar percentages (0, 1, 5, 7, 10 and 20 percent) and specific surface area, particle size, crystallite size, stable crystallographic phases and surface chemical composition will be evaluated. The methods that will be used to characterize the nanopowders will be: N2 adsorption (adopting the BET method), X-ray diffraction, infrared spectroscopy (FTIR with DRIFT cell), laser granulometry, zeta potential measurements and X-ray fluorescence analysis. The surface MgO quantification will be possible due to its easy removal from the surface in an acidic solution of HNO3.