The formation mechanism and photocatalytic properties of a multiwalled carbon nanotube (MWCNT)/TiO2- based nanotube (TNTs) composite are investigated. The CNT/TNT composite is synthesized via a solution chemical route. It is confirmed that this 1-D nanotube composite has a core-shell nanotubular structure, where the TNT surrounds the CNT core. The photocatalytic activity investigated based on the methylene blue degradation test is superior to that of with pure TNT. The CNTs play two important roles in enhancing the photocatalytic activity. One is to act as a template to form the core-shell structure while titanate nanosheets are converted into nanotubes. The other is to act as an electron reservoir that facilitates charge separation and electron transfer from the TNT, thus decreasing the electronhole recombination efficiency.

We demonstrate the electrochromic properties of TiO2 nanotubes prepared by an anodization process and investigate the effects of heat treatment and viologen incorporation on them. The morphology and crystal structure of anodized TiO2 nanotubes are investigated by scanning electron microscopy and X-ray diffraction. As-formed TiO2 nanotubes have straight tubular layers with an amorphous structure. As the annealing temperature increases, the anodized TiO2 nanotubes are converted to the anatase and rutile phases with some cracks on the tube surface and irregular morphology. Electrochemical results reveal that amorphous TiO2 nanotubes annealed at 150°C have the largest oxidation/ reduction current, which leads to the best electrochromic performance during the coloring/bleaching process. Viologenanchored TiO2 nanotubes show superior electrochromic properties compared to pristine TiO2 nanotubes, which indicates that the incorporation of a viologen can be an effective way to enhance the electrochromic properties of TiO2 nanotubes.

nanopowders with anatase structure were firstly prepared by controlling the pH value of a precursor solution without any heat-treatment at room temperature. The prepared nanopowders were hydrothermally treated in 10M NaOH solution at . Then, the samples were washed in DI water or 0.1M HCl. The nanotubes were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The gas sensitivity of nanotubes for toluene gas was also investigated. The results show that nanotubes can be prepared by hydrothermal treatment. The morphology of nanotubes prepared by 0.1M HCl washing is destroyed to some extent. nanotubes with DI water washing show better sensitivity than that with 0.1M HCl washing.

There has been a controversy on the formation mechanism of TiO2 nanotubes. This study was conducted to elucidate the formation mechanism of TiO2 nanotubes. TiO2 nanotubes were prepared by a hydrothermal method. TiO2 nanotubes formation mechanism was investigated by controlling the formation time. It was found that TiO2 nanotubes were formed by growing, not by wrapping of sheets. The phase structure of hydrogen titanate nanotubes was different from that of TiO2 nanotubes. It is important to wash the sodium titanate nanotubes with an acidic solution to get hydrogen titanate nanotubes and then to calcine the hydrogen titanate nanotubes around 400℃ to obtain TiO2 nanotubes.