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Anatase–rutile mixed-phase TiO2 is proved to have better photocatalytic activity than pure anatase TiO2, but the preparation of the mixed-phase TiO2 usually needs thermal treatments at more than 500 °C. In this study, we present a one-step nonaqueous sol–gel route to form mixed-phase TiO2 at relatively low temperatures from 160 to 220 °C. The structure, morphology and surface chemical state were examined with X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), respectively. The influence of the preparation temperature on the structural characteristics including grain size and phase content were investigated using the Rietveld refinement. Through TEM, the evolution from sphere-like anatase nanoparticle to hexagonal rutile single-crystal was investigated. The photocatalytic activities of the obtained anatase and anatase-rutile TiO2 were evaluated by degradation of Rhodamine B under visible light, and a distinct enhanced activity was observed. Through the UV-vis spectrum and mass spectrum, the pathway of RhB degradation caused by the mixed-phase TiO2 with visible light was studied. At the same time, the mechanism of the enhanced photocatalytic properties was presented. The mechanisms were verified with UV-vis measurements. It is believed that the obtained mixed-phase TiO2 is one promising candidate for wastewater treatment. [ABSTRACT FROM AUTHOR]

ZnO quantum dots (QDs), a few nanometers in size, were synthesized by a sol–gel method using different solvents (methanol, ethanol and hexanol). The structural, morphological and photoluminescent properties were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), photoluminescence spectrometry, and UV-vis spectroscopy. The results indicated that ZnO QDs with good dispersion, ranging in size from 3.3 nm to 7.7 nm, could be controlled easily by the solvents. The ZnO QDs exhibited strong visible emission from green to orange. The reasons for the change in emission color are believed to be the quantum size effect and the change in defect concentration due to the different solvents used in their preparation. A possible mechanism for the photoluminescence of ZnO QDs is also presented. [ABSTRACT FROM AUTHOR]