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HfOxNy thin film was deposited on oxidized silicon substrate; its physical structure and chemical composition were studied in detail by X-ray diffractometer, scanning electron microscopy, field emission transmission electron microscope and X-ray photoelectron spectrometer. Microtemperature sensors with high sensitivity based on the film were fabricated. To clarify the conduction process of grain, grain boundary (GB) and the whole film, temperature-dependent AC impedances of a sensor were measured and analyzed in 40–300 K. The results show that at all of the measured temperatures, the resistance of grain is much larger than that of GB, and its rising rates with the temperature reduction are also much larger than that of GB, indicating that the resistive property of HfOxNy thin film is determined by grain. In addition, it has been confirmed that the conduction process of both the HfOxNy film and GB is dominated by thermal activation and Mott variable-range hopping (VRH) in relatively high and low temperature range, respectively. The conduction process of the grain obeys Mott VRH in the whole considered temperature range, while the Mott characteristic temperature is changed. These results provide new insights into the performance enhancement of the transition metal oxynitride-based temperature sensors.

ZnO/Ag2S core–shell nanorod arrays (NRAs) are successfully fabricated via chemical bath deposition procedure and subsequent successive ionic layer adsorption and reaction (SILAR) technique. The average diameter of ZnO core is about 100 nm, and the thicknesses of Ag2S shell are adjusted from 6 to 35 nm by varying the time of SILAR. ZnO/Ag2S NRAs show an enhancement of absorption in the visible region, and the absorption intensity in the visible region enhances with the increase in Ag2S shell thickness. Compared with pure ZnO NRAs, ZnO/Ag2S NRAs exhibit outstanding photocatalytic activity for degradation of rhodamine B (RhB) aqueous solution under simulated sunlight irradiation. In addition, ZnO/Ag2S NRAs with Ag2S shell thickness of 6 nm display the highest photocatalytic activity, which is 6.0 times higher than that of pure ZnO NRAs.

Novel Fe3O4@SiO2@mTiO2–Au (mTiO2: mesoporous TiO2) core–shell microspheres were fabricated by the facile and efficient methods, and they were characterized by SEM, TEM, XRD, XPS, BET, VSM, and photoelectrochemical measurements. Through the test of methylene blue (MB) degradation, the relative photocatalytic activity of four samples follows the order: Fe3O4@SiO2@mTiO2–Au (FSTA) > Fe3O4@SiO2@mTiO2 (FST) > Fe3O4@mTiO2 (FT) > P25. The superior photocatalytic property of FSTA is mainly attributed to the positive effect of three components including decorative Au nanoparticles, SiO2 intermediate layer, and mesoporous TiO2 layer. Moreover, FSTA microspheres were easily recycled by using an external magnetic field while their photocatalytic efficiency had no obvious decrease after running 6 times of photocatalytic test. The well-designed microstructure makes FSTA a highly efficient, recoverable, and stable photocatalytic system, which has promising applications in environmental treatment.

A novel magnetically separable composite photocatalyst—〈La-doped TiO2〉/CoFe2O4 nanofiber—was prepared by a two-spinneret electrospinning method combined with sol–gel method. The nanofibers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), Energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometer (VSM). It was shown that the diameter of 〈1.0% La-doped TiO2〉/CoFe2O4 nanofibers was 100–150 nm after calcination at 600 °C for 2 h. EDS and XPS measurements on the photocatalytic material indicated the existence of La3+ oxidation states in 〈1.0% La-doped TiO2〉/CoFe2O4 nanofibers. The photocatalytic activity of as-prepared nanofibers was evaluated using methylene blue (MB) as a model organic compound and the result revealed that the 〈1.0% La-doped TiO2〉/CoFe2O4 nanofibers have an efficient photocatalytic property, and the degradation rate of MB could reach 93% in 150 min. Moreover, the magnetic property of the nanofibers has also been characterized, and the nanofibers show a good magnetic response, which indicates that the possibility of the magnetic nanofibers’ potential recycling property.

Magnetically separable TiO2-coated SrFe12O19 electrospun nanofibers were obtained successfully by means of sol–gel, electrospinning, and coating technology, followed by heat treatment at 550–650 °C for 3 h. The average diameter of the electrospun fibers was 500–600 nm. The fibers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM). The optimized calcining temperature was determined by XRD and the analysis of decolorizing efficiency of methylene blue (MB) under UV–vis irradiation. The photocatalytic activity of the TiO2-coated SrFe12O19 fibers was investigated using ultraviolet–visible absorbance by following the photooxidative decomposition of a model pollutant dye solution, MB in a photochemical reactor. In contrast to pure TiO2 fibers, the TiO2-coated SrFe12O19 fibers have higher absorption in 250–750 nm wavelength regions. The presence of SrFe12O19 not only broadened the response region of visible-light, but also enhanced the absorbance for UV light. The decolorizing efficiency of MB under UV–vis irradiation was up to 98.19%, which was a little higher than that of Degussa P25 (97.68%). Furthermore, these fibers could be recollected easily with a magnet in a photocatalytic process and had effectively avoided secondary pollution of treated water.