Approximately 15 nm thick nitrogen-doped lanthanum titanate (La₂Ti₂O₇) nanosheets with a single-crystalline perovskite structure have been prepared by hydrothermal processing and subsequent heat treatment in NH3 at 600 °C. Doping nitrogen into the La₂Ti₂O₇ nanosheets results in the narrowing of the band gap, extending the light absorption into the visible light region (∼495 nm). The nitrogen-doped La₂Ti₂O₇ nanosheets not only show significant visible light photocatalytic activity toward the decomposition of methyl orange but also exhibit enhanced the ultraviolet light photocatalytic activity. The enhancement of photocatalytic activity originates from the narrowing of the band gap of La₂Ti₂O₇ nanosheets. The results obtained show that the desirable route to extend the photocatalytic activity of a semiconductor from the ultraviolet to the visible light region is to narrow the band gap rather than to create localized mid-gap states.

NaYF₄ :Yb,Tm@TiO₂ core–shell composites were synthesized via a facile hydrothermal method. The highly crystalline TiO₂ shell can be uniformly coated onto lanthanide-doped NaYF₄ microrods and nanorods under mild conditions without calcination. The thickness of the TiO₂ shell can be tuned by varying the ratio of fluoride rods and Ti precursors. The microcomposite with a moderate TiO₂ shell shows excellent photocatalytic activity under near-infrared irradiation.

Porous activated carbon nanofibers have been prepared by electrospinning a H₃PO₄-containing polyacrylonitrile precursor. A small amount of H₃PO₄ (<1 wt%) serves as the activation agent during carbonization of the nanofibers. The activated carbon nanofibers have a large surface area (∼709 m² g⁻¹) and high porosity (0.356 cm³ g⁻¹). A high specific capacitance of 156 F g⁻¹ (at 0.5 A g⁻¹) is obtained at a 1 : 10 mass ratio of H₃PO₄ to polyacrylonitrile. The energy density of the supercapacitor with the activated carbon nanofibers as the electrodes reaches 10.98 Wh kg⁻¹ at a power density of 10 kW kg⁻¹. This is ∼9 fold larger than that of carbon nanofibers without H₃PO₄ because the H₃PO₄-based activation process significantly increases both the micropore volume and the volume ratio of mesopores to micropores.

Dual-carbon confined CoSe₂ microcubes are synthesized and demonstrate enhanced rate and cycling performance for sodium storage.

Single-crystalline uniform Ta₂O₅ nanowires are prepared by a novel synthetic route. The formation of the nanowires involves an oriented attachment process caused by the reduction of surface energy. The nanowires are successfully applied to photocatalytic H₂ evolution, contaminant degradation, and dye-sensitized solar cells (DSCs). The Ta₂O₅-based DSCs reveal a significant photovoltaic response, which has not been reported. As a photocatalyst, the Ta₂O₅ nanowires possess high H₂ evolution efficiency under Xe lamp irradiation, nearly 27-fold higher than the commercial powders. A better performance of photocatalytic contaminant degradation is also observed. Such improvements are ascribed to better charge transport ability for the single-crystalline wire and a higher potential energy of the conduction band. This new synthetic approach using a water-soluble precursor provides a versatile way to prepare nanostructured metal oxides.