Novel mesoporous NiO/HTiNbO5 nanohybrids with high visible-light photocatalytic activity and good biocompatibility

Mesoporous nanohybrids of NiO nanoparticles and HTiNbO5 nanosheets have been successfully synthesized by first exfoliating layered HTiNbO5 in tetrabutylammonium hydroxide (TBAOH) to obtain HTiNbO5 nanosheets, then reassembling with a nickel precursor and finally heating with urea. The resulting samples were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, photoluminescence spectroscopy (PL) and N-2 adsorption-desorption measurements. It was found that the as-prepared nanohybrids had a relatively large interlayer spacing of 1.05 nm. After calcination, the titanoniobate nanosheet was still retained and the pore size of the resulting nanohybrids became larger. Compared with the original HTiNbO5, the obtained nanohybrids were mesoporous with a greatly expanded surface area (similar to 75-115 m(2) g(-1)), a much strengthened absorption in the UV light region and a visible-light response. Nickel atoms were present in the form of Ni-O in the nanohybrid, and NiO nanoparticles were homogeneously distributed with an average particle size of 2-3 nm, giving rise to the visible light response. The catalytic activities of the obtained samples were evaluated by the photodegradation of RhB solution under visible light irradiation. The introduction of urea during the calcination process not only increased the thermal stability and surface area, but also decreased the rate of recombination of photogenerated holes and electrons, leading to a greatly enhanced photocatalytic activity of the resulting nanohybrids. The dye molecules were mainly degraded to aliphatic organic compounds and partially mineralized to CO2 and/or CO, rather than being simply decolorized. In addition, cell viability results for HepG2 cells show that the as-prepared sample have good biocompatibility.