Active species such as holes, electrons, hydroxyl radicals (•OH), and superoxide radicals (O 2 •− ) involved in the photodegradation process of methyl orange (MO) over TiO 2 photocatalyst were detected by several techniques. Using different types of active species scavengers, the results showed that the MO oxidation was driven mainly by the participation of O 2 •−, holes and •OH radicals. Characterized by the liquid chromatography/mass spectrometry, the transversion of the degradation products with the light irradiation time was first analyzed. Combined with the measurement of oxidation reduction potential, dissolved oxygen, conductivity, and pH values, the degradation process of MO on TiO 2 under the effect of the active species was revealed. This was the first time that electrodes were introduced to track the degradation process in situ, and these parameters would be helpful to explain the degradation processes of other organic pollutants.

A nanocrystal heterojunction LaVO4TiO2 visible light photocatalyst has been successfully prepared by a simple coupled method. The catalyst was characterized by powder X-ray diffraction, nitrogen adsorption-desorption, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectra, photoluminescence, and electrochemistry technology.The results showed that the prepared nanocomposite catalysts exhibited strong photocatalytic activity for decomposition of benzene under visible light irradiation with high photochemical stability. The enhanced photocatalytic performance of LaVO4/TiO2 may be attributed to not only the matched band potentials but also interconnected heterojunction of LaVO4 and TiO2 nanoparticles.

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ZnIn 2 S 4 microspheres were successfully synthesized by a hydrothermal method. A series of synthesis temperatures from 80 to 200 °C was investigated. The samples were characterized by X-ray diffraction, UV-vis spectroscopy, nitrogen sorption analysis, X-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy (SEM). The results indicated that the crystalloid structure and optical property of temperature series products were almost the same. The specific surface area (S BET ) of ZnIn 2 S 4 products declined with increasing synthesis temperature. The 80 °C sample had the largest S BET (85.53 m 2 g -1 ). SEM images demonstrated that the morphology of ZnIn 2 S 4 was marigold-like microspheres, and the 80 °C sample had a well-proportioned morphology. Several dyes (methyl orange, congo red, and rhodamine B) were applied in the ZnIn 2 S 4 photocatalytic reactivity investigation. It showed efficient visible light photocatalytic degradation of dyes. A liquid chromatogram-mass spectrometer was used for identification of dyes and their degradation products. A large number of • OH radicals, investigated by the method of photoluminescence with terephthalic acid, were generated in the photocatalyst system. The results indicated that the • OH radicals played an important role in the superior visible photocatalytic activity of the ZnIn 2 S 4 system. The mechanism related to the photocatalytic degradation was proposed and discussed.

Photonic crystals have attracted extensive interest for the potential applications in manipulating light by nontraditional ways based on photonic band structure concepts. In this paper, 3D inverse-opal TiO 2 photonic crystals (TiO 2 -PCs) with designed photonic band gaps are prepared. It is worth noting that when the photonic band gaps of the TiO 2 -PCs are matched with the absorption peaks of the dyes (methyl orange, rhodamine B, and methylene blue), the photocatalytic activity of the corresponding sample is improved under simulated solar light (320 nm < λ < 800 nm) and visible light (420 nm < λ < 800 nm) irradiation. The enhancement could be attributed to the intensified dye sensitization as a result of slow photon effect on the edges of the photonic band gaps. Furthermore, the TiO 2 -PCs exhibit much higher photocatalytic activity and stability than TiO 2 nanoparticle film. It is believed that the presence of inverse opal structure plays an essential role in affecting the dye sensitization and photoreactivity, which could provide valuable information on the design of photocatalysts and set the foundation for the future environmental and energy technologies.