Síntese e caracterização de nanoestruturas à base de dióxido de titânio

Abstract

Nanostructures based in Titanium dioxide have been extensively studied due to their potential technological applications. One of their most promising applications is the photocatalysis, in which the surface area is a crucial property for a high efficient process. Since the discovery of a simple wet chemical route, which is, NaOH treatment of crystalline TiO2 powders to produce TiO2-based nanotubes with a large surface area, significant interest have been given to this nanostructure. In this study, anatase titanium dioxide nanoparticles were submitted to a hydrothermal treatment statically and under stirring during one and four days. The samples synthesized during one day and during four days statically yielded multi-walled nanotubes, however the sample produced under stirring yielded nanotubes with more walls than the statically one. The titanium dioxide synthesized during four days under stirring resulted in nanoribbons. Two samples, one made of nanotubes and other made of nanoribbons, were washed with hydrochloric acid for proton exchange. Scanning and transmission electron microscopy confirmed the formation of these nanostructures, which were also analyzed with X-Ray diffraction and Raman spectroscopy. Through the X-Ray diffraction the structure of the nanotubes and nanoribbons were assigned to a NaTi3O6(OH)·2(H2O). The proton exchange Na to H influences in the position and ratio of the relative intensities of some Raman modes. The shifts in frequency of the bands and the changes in their ratio intensity can be explained by the decrease in interlayer distance and the proton exchange, confirmed by X-Ray patterns.