Studies On Chemical Modification Of Carbon Nanotubes And Short Carbon Nanotubes Improving The Photocatalytic Properties Of TiO₂

With their chemical inactivity, extremely mechanical strength, well electronic properties and unusual sorption, carbon nanotubes (CNTs) are a one-dimension nanostructural material. For many unique performance and potential application of the new carbonaceous materials, they have generated great interest since their discovery in 1991, producing a main focus of research in physics, chemistry and material field. And the aspects of study on CNTs have become their chemical reactions and applications, with the gradual development of composite technology and purification of CNTs.The huge molecular weight of CNTs leads to their indissoluble, which limits the research of their chemical character. However, after CNTs' structures are modified and product some active functional group on them, such as -OH, -COOH and so on, the organic chemical reactions between CNTs and some organic compound are feasible. In the public literatures, most kinds of organic chemical decoration were carried out by reaction between CNTs and amines to product amide-alkyl groups. In this work we decorate CNTs with amine group by reacting with diamine for the first time. Before this decoration, an efficient method for purification and function of multi-walled carbon nanotubes (MWNTs) synthesized by chemical vapor deposition (CVD) has been carried out. TEM, Raman and IR spectra indicated that the ends and side-walls of MWNTs are opened and oxidized into carboxylate group ( v (C=o)= 1709cm-1). Then the carboxyl-terminated MWNTs were reacted with NH2CH2CH2NH2 with the aid of the condensation agent DCC. The modified carbon nanotubes were characterized with FT-IR and Raman spectra. After the condensation reaction, the amide-alkyl chain appears on the derivatives of MWNTs (v(C=O)=1581cm-1) and the solubility of MWNTs in organic solvent is enhanced, while the structure of carbon nanotubes were preserved.In the second part of the work, the short MWNTs were prepared bypost-synthesis chemical oxidation with ultrasonication, and used as catalytic carriers in TiOa-CNTs. TEM image showed that above 82% of MWNTs could be shortened to the length of less than 500 nm. The nano composites of photocatalysts TiCVCNTs were made by the method of sol-gel, using short MWNTs as the carriers and titanium tetrabutoxide as the precursor. TiOa-CNTs were characterized by TEM, XRD and BET techniques. The results indicate that, compared with pure TiO2, TiO2-CNTs have less crystallite size, larger BET surface area and anatase crystal. This material is quite stable, not inclined to aggregate. The photocatalytic activity of TiO2-CNTs was evaluated by degradation of dye brilliant red X-3B in aqueous solution. The results show that the photocatalytic activity of TiOa-CNTs is higher than that of pure TiO2 both as suspender and as a coating of the electrode.