No abstract

Superfast crystallization of TiO2 nanotubes at low energy budget (bath temperature starting from 2 °C).

Cost effectiveness and reducing the energy and time consumption are crucial factors of concern while material preparation for device fabrication is considered. Here a simple electro chemical reductive method of self-doping is proved for first time to achieve efficient ultrafast (5 s) low temperature (15 °C) crystallization of well aligned TiO 2 nanotubes (TONT). Moreover, the so prepared self-doped TONTs are demonstrated to exhibit superior photocatalytic performance over the undoped in the degradation of the organic pollutant methylene blue. The effect is correlated with the tailoring of the crystallinity and red shift in band gap on self-doping due to the introduction of Ti 3+ ions and oxygen vacancies.

No abstract

Modified hybrid structures of TiO2 nanotubes (TONT), p-Al doped TONT/n-TONT with an additional overlayer of alumina, are constructed to achieve 99.57% photodegradation of the stable organic pollutant methylene blue (MB) within 180 min, a degradation rate 17 times higher than pure TONTs. The anodization at three different temperatures 2, 28 and 40 °C followed by impregnation of Al is used for their preparation. The analyses of structure, chemical composition and morphology are completed using x-ray diffraction, x-ray photoelectron spectroscopy (XPS) and high resolution transmission microscopy, respectively, Rutherford back scattering and field emission scanning electron microscopy confirm the formation of the hybrid structure. This structure exhibits the highest photodegradation rate with TONT based catalysts to date for MB blue, by enhancing the electron—hole separation, the absorption of visible photons and the adsorption sites for the pollutant. The optical data coupled with valence band XPS is used for elucidating the energy band structure of the p-n junctions and to gain insight into the effect of the junction mechanism on photoactivity. The rectification ratios of the impregnated p-n junctions, determined by current—voltage measurements, are found to vary from 102 to 106.