One-Step Hydrothermal Synthesis and Visible-Light Photocatalytic Activity of Ultrafine Cu-Nanodot-Modified TiO<sub>2</sub> Nanotubes

One dimensional titanate nanotubes modified with copper nanospheres were synthesized through a facile one-step hydrothermal process. Transmission electron microscope (TEM), X-ray diffraction (XRD), and energy dispersive spectrometry (EDS) were used to monitor the changes in the morphology and phases during the hydrothermal process. The diameter of the Cu-TiO2 composite nanotubes was 10-15 nm and their lengths were ca 100 nm, the dimension of the covered Cu nanoparticles was about 5 nm. Brunauer-Emmett-Teller (BET) tests revealed the specific surface area of the Cu-TiO2 composite nanotubes to be 154.67 m(2) . g(-1). The formation process and mechanism of the composite nanotubes were surveyed by adjusting the hydrothermal duration and titanium precursor. The results revealed that an amorphous titanium precursor is essential for the successful formation of this unique topography and phase composition. Anti-Ostwald ripening, a decrease in the dimensions of the copper nanospheres with hydrothermal time, was observed in the TEM images, which is of benefit to helps keep the particles on the nanoscale. The UV-Vis spectrum of the as-prepared material exhibits a strong absorption at 350-800 nm in the visible band compared with commercial TiO2 nanopowders. The plasmonic absorption of metallic copper particles between 550 and 600 nm is seen in the UV-Vis spectrum. Schottky barriers between copper-TiO2 interfaces make this kind of material a potential agent in speeding up electron transport rates and slowing recombination rates. Photocatalytic experiments demonstrated this unique Cu-TiO2 composite nanotube material has a high photocatalytic activity under visible-light irradiation.