Nitrogen-doped mesoporous nanohybrids of TiO2 nanoparticles and HTiNbO5 nanosheets with a high visible-light photocatalytic activity and a good biocompatibility

Nitrogen-doped mesoporous nanohybrids of TiO2 nanoparticles and HTiNbO5 nanosheets have been successfully synthesized by first exfoliating layered HTiNbO5 in tetrabutylammonium hydroxide (TBAOH) to obtain HTiNbO5 nanosheets, then reassembling with TiO2 colloids and finally heating with urea in air at 450 degrees C. The resulting samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, laser Raman spectroscopy (LRS) and N-2 adsorption-desorption measurements. It was found that the TiO2 nanoparticles existed in the anatase phase and the titanoniobate nanosheets were still maintained after nitrogen doping. The obtained nitrogen-doped nanohybrids showed a greatly expanded surface area with a mesoporous structure and the doped nitrogen atoms were located in the interstitial sites of TiO2, giving rise to the visible light response. The catalytic activities of the obtained samples were evaluated by the photodegradation of rhodamine B (RhB) solution under visible light irradiation. The obtained N-doped nanohybrid had a higher activity than N-doped HTiNbO5 nanosheets and N-doped TiO2, indicating the synergetic effect of TiO2 nanoparticles and HTiNbO5 nanosheets. The dye molecules were mainly degraded to aliphatic organic compounds and mostly further mineralized to CO2 and/or CO, rather than being simply decolorized. In addition, the cell viability results of the HepG2 cells showed that the as-prepared sample had a good biocompatibility.