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In this paper, Sn-doped TiO 2 nanoparticles were prepared by a sol–gel method, and also were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectrum (IR), ultraviolet–visible diffuse reflection spectrum (UV–vis DRS), photoluminescence spectrum (PL), surface photovoltage spectroscopy (SPS) and electrical field induced surface photovoltage spectroscopy (EFISPS). The sample activity was evaluated by photocatalytic oxidation reactions of phenol solution. The effects of thermal treatment temperature and Sn amount on photoinduced charge property, mainly involving charge separation and bound excitons resulting from surface states, and photocatalytic activity of TiO 2 nanoparticles were principally investigated. The results show that an appropriate calcination temperature and Sn dopant amount can greatly enhance the SPS responses of TiO 2 nanoparticles related not only to the band–band transitions but also to the bound excitons, and obviously weaken the PL signal, while the photocatalytic activity remarkably raises. These demonstrate that the separation rate of photoinduced charges of TiO 2 nanoparticles can be effectively improved by doping Sn, which is responsible for the obvious increase in the photocatalytic activity. Moreover, the existence of bound excitons related to surface states also favor the photocatalytic activity. In addition, it can be found that the SPS responses related to the bound excitons could easily exhibit in the TiO 2 sample consisting of much of anatase and little of rutile, which is possibly ascribed to the heterojunction between the anatase and rutile phase.

TiO 2 nanoparticles capped with sodium dodecylbenzenesulfonate (DBS) are synthesized by a sol–hydrothermal process using tetrabutyl titanate and DBS as raw materials. The effects of surface-capping DBS on the surface photovoltage spectroscopy (SPS), photoluminescence (PL) and photocatalytic performance of TiO 2 nanoparticles are principally investigated together with their relationships. The results show that the surface of TiO 2 nanoparticles can be well capped by DBS groups while the pH value and added DBS amount are controlled at 5.0 and 2% of TiO 2 mass weight, respectively, and the linkage between DBS groups and TiO 2 surfaces is mainly by means of quasi-sulphonate bond. The intensities of SPS and PL spectra of TiO 2 obviously decrease after DBS-capping, while the activity can greatly increase during the photocatalytic degradation of Rhodamine B (RhB) solution, which are mainly attributed to the electron-withdrawing character of the DBS groups. Moreover, the enhancement of photocatalytic activity of DBS-capped TiO 2 is also related to the increase in the capability for adsorbing RhB.

In this paper, pure and La doped TiO 2 nanoparticles with different La content were prepared by a sol–gel process using Ti (OC 4 H 9 ) 4 as raw material, and also were characterized by XRD, TG-DTA, TEM, XPS, DRS and Photoluminescence (PL) spectra. We mainly investigated the effects of calcining temperature and La content on the properties and the photocatalytic activity for degrading phenol of as-prepared TiO 2 samples, and also discussed the relationships between PL spectra and photocatalytic activity as well as the mechanisms of La doping on TiO 2 phase transformation. The results showed that La 3+ did not enter into the crystal lattices of TiO 2 and was uniformly dispersed onto TiO 2 as the form of La 2 O 3 particles with small size, which possibly made La dopant have a great inhibition on TiO 2 phase transformation; La dopant did not give rise to a new PL signal, but it could improve the intensity of PL spectra with a appropriate La content, which was possibly attributed to the increase in the content of surface oxygen vacancies and defects after doping La; La doped TiO 2 nanoparticles calcined at 600°C exhibited higher photocatalytic activity, indicating that 600°C was an appropriate calcination temperature. The order of photocatalytic activity of La doped TiO 2 samples with different La content was as following: 1>1.5>3>0.5>5>0 mol%, which was the same as the order of their PL intensity, namely, the stronger the PL intensity, the higher the photocatalytic activity, demonstrating that there were certain relationships between PL spectra and photocatalytic activity. This could be explained by the points that PL spectra mainly resulted from surface oxygen vacancies and defects during the process of PL, while surface oxygen vacancies and defects could be favorable in capturing the photoinduced electrons during the process of photocatalytic reactions.

The pure, 1 mol% only La or only Cu doped TiO2 and La and Cu codoped TiO2 were prepared by a sol-gel process. The effects of doping on photoinduced charge properties of nanosized TiO2 were mainly investigated by means of Surface Photovoltage Spectrum (SPS) and Photoluminescence Spectrum (PL), together with their relationships with photocatalytic activity. The results show that La dopant can inhibit the phase transformation of TiO 2 , meanwhile improve the separation rate of photoinduced charge carriers, and enrich the binding surface states. However, Cu dopant has a reverse effect compared to La dopant. This is responsible for the results that doping La is favorable for the increase in the photocatalytic activity for degrading the RhB solution, while doping Cu is bad to photocatalyitc reaction. In addition, codoping La and Cu cannot exhibit an obvious combination effect.

The ZnO nanoparticles are prepared by a precipitation process, and also are characterized by means of the modern testing techniques such as XPS, ESR, SPS and PL. The activity of the as-prepared ZnO is evaluated in the photocatalytic oxidation of gas phase n-C7H16. The relationships of surface oxygen vacancies (SOV) with photoluminescence (PL) and photo-catalytic performance are discussed in details. The results show that the smaller the particle size, the larger the SOV content, the stronger the PL signal, the higher the photocatalytic activity, in-dicating that the SOV, PL and photocatalytic activity have inherent relationships. This was because of the reasons that the PL signal is attributed to the free and binding excitons resulting from the SOV, while the SOV is favorable for a photocatalytic oxidation reaction since the SOV can easily capture the photoinduced electrons, and the captured electrons had strong interac-tions with the adsorbed oxygen. In addition, the surface states of ZnO nanoparticles, arising from the SOV and oxygen species, are very abundant.