Sn-doped TiO₂ nanotubes, synthesized through a sol–gel method and a subsequent hydrothermal process, exhibit excellent electrochemical performance for sodium ion batteries.

Cobalt oxide (Co₃O₄) was homogeneously coated on multiwalled carbon nanotube through a simple chemical deposition method and employed in supercapacitor electrodes. SEM image indicated the uniform distribution of Co₃O₄ nanoparticles on the surface of the multiwalled carbon nanotube. A maximum specific capacitance of 273 Fg⁻¹ was obtained at the charge–discharge current density of 0.5 Ag⁻¹. After 500 cycles of continuous charge–discharge process, about 88% of the initial capacity could be retained.

Transition metal (TM)-doped TiO₂ films (TM = Co, Ni, and Fe) were deposited on Si(100) substrates by a sol–gel method. With the same dopant content, Co dopants catalyze the anatase-to-rutile transformation (ART) more obviously than Ni and Fe doping. This is attributed to the different strain energy induced by the different dopants. The optical properties of TM-doped TiO₂ films were studied with spectroscopic ellipsometry data. With increasing dopant content, the optical band gap (E_OBG) shifts to lower energy. With the same dopant content, the E_OBG of Co-doped TiO₂ film is the smallest and that of Fe-doped TiO₂ film is the largest. The results are related to electric disorder due to the ART. Ferromagnetic behaviors were clearly observed for TM-doped TiO₂ films except the undoped TiO₂ film which is weakly magnetic. Additionally, it is found that the magnetizations of the TM-doped TiO₂ films decrease with increasing dopant content.

NaNbO₃ single-crystal films with (100), (110) and (111) oriented crystal planes were grown on LaAlO₃ (100), (110) and (111) substrates by pulsed laser deposition. The NaNbO₃ films exhibit anisotropy in the photocatalytic oxidization activity for Rhodamine B (RhB) degradation. The increasing order of RhB degradation in Ar atmosphere under full arc irradiation of a Xe lamp is (100) < (110) < (111), which is consistent with that of ˙OH generation. The good linear relationship between the activity of RhB degradation and the coercive electric field indicates that the photocatalytic activity is closely related to the ferroelectric property.