Estudo Teórico de nanotubos de dióxido de titânio e suas interações com gases

Abstract

The theoretical study of nanotubes of titanium dioxide, used a methodology to create models of nanotubes from the unit cells of the crystal of TiO2 (rutile and anatase) in specific planes, in this case the plane anatase (101) and rutile in plane (110). The structures were generated under an quantum mechanical calculations in semi-empirical methods (PM7) and abinitio DFT and HF methods in the 6-31G and 6-311G basis. Various models were created and verficou that the most stable structures were the ones that showed the larger diameter. Among the models that stand out for the amount of energy variation have the anatase nanotube of molecular formula [[(TiO2)4]20]3 and rutile nanotube of molecular formula [[(TiO2)2]13]3. Through comparison of models with the same number of atoms, it was found that anatase nanotubes had a greater stability compared with the rutile nanotubes. In the evaluation of the gap by means of semiempirical methods and HF anatase nanotubes were classified as insulators because the band gap between 6.00 eV at 10.00 eV, as in DFT values varied from 2.00 eV to 2.50 eV, classified as the semiconductor. It was found that the links Ti-Ti-O and Ti in anatase models were smaller than in the models rutile. Interactions of H2 and CO with a model of anatase verficou were performed and the adsorption of CO with pure structure. Adsorption with H2 molecule was found by tests doping with Pt and Au.