Large-scale synthesis of aligned carbon nanotubes was achieved by using a method based on chemical vapor deposition catalyzed by iron nanoparticles embedded in mesoporous silica. Scanning electron microscope images show that the nanotubes are approximately perpendicular to the surface of the silica and form an aligned array of isolated tubes with spacings between the tubes of about 100 nanometers. The tubes are up to about 50 micrometers long and well graphitized. The growth direction of the nanotubes may be controlled by the pores from which the nanotubes grow.

In this study, conventional TiO 2 powder was heated in hydrogen (H 2 ) gas at a high temperature as pretreatment. The photoactivity of the treated TiO 2 samples was evaluated in the photodegradation of sulfosalicylic acid (SSA) in aqueous suspension. The experimental results demonstrated that the photodegradation rates of SSA were significantly enhanced by using the H 2 -treated TiO 2 catalysts and an optimum temperature for the H 2 treatment was found to be of 500-600°C. The in situ electron paramagnetic resonance (EPR) signal intensity of oxygen vacancies (OV) and trivalent titanium (Ti 3þ ) associated with the photocatalytic activity was studied. The results proved the presence of OV and Ti 3þ in the lattice of the H 2 -treated TiO 2 and indicated that both were contributed to the enhancement of photocatalytic activity. Moreover, the experimental results presented that the EPR signal intensity of OV and Ti 3þ in the H 2 -treated TiO 2 samples after 10 months storage was still significant higher than that in the untreated TiO 2 catalyst. The experiment also demonstrated that the significant enhancement occurred in the photodegradation of phenol using the H 2 -treated TiO 2 .

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