In this paper, ABO3-type perovskite LaFeO3 nanosized photocatalysts were synthesized by a sol-gel method, using citric acid (HOOCCH2C(OH)(COOH)CH2COOH) as complexing reagent and La(NO3)3 6H2O and Fe (NO3)3 9H2O as raw materials. The asprepared samples also were characterized by several testing techniques, such as thermogravimetry-differential thermal analysis (TG-DTA), X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET), 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 of different LaFeO3 nanoparticles for degrading Rhodamine B solution under visible irradiation (λ>400nm) was evaluated. The effects of thermal treatment temperature on photoinduced charge property and hotocatalytic activity were mainly investigated, together with their relationships. The results show that the LaFeO3 sample calcined at 500 8C exhibits higher activity, and the activity decreases with increasing calcination temperature, which is in good agreement with the characterization results. The weaker is the PL and SPS signal, the higher is the photocatalytic activity. Moreover, the activity of all as-prepared LaFeO3 samples is higher than that of international P-25 TiO2 under visible irradiation.

In this review, the photoluminescence (PL) performance and mechanism of nano-sized semiconductor materials, such as TiO2 and ZnO, are introduced, together with their attributes and affecting factors. Moreover, the applications of PL spectra in environmental photocatalysis are discussed in detail, viz. the inherent relationships between the PL intensity and photocatalytic activity are revealed on the basis of PL attributes, demonstrating that the PL spectra can reflect some important information such as surface defects and oxygen vacancies, surface states, photo-induced charge carrier separation and recombination processes in nano-sized semiconductor materials. Thus, the PL spectrum can provide a firm foundation in theory for designing and synthesizing new semiconductor photocatalysts with high activity, as well as quickly evaluating the photocatalytic activity of semiconductor samples.

In this paper, TiO2 nanoparticles doped with different amounts of Zn were prepared by a sol-gel method and were mainly characterized by means of X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and surface photovoltage spectrum (SPS). The effects of surface oxygen vacancies (SOVs) of Zn-doped TiO2 nanoparticles on photophysical and photocatalytic processes were investigated along with their inherent relationships. The results show that the SOVs easily bind photoinduced electrons to further give rise to PL signals. The SOVs can result in an interesting sub-band SPS response near the band edge in the TiO2 sample consisting of much anatase and little rutile, except for an obvious band-to-band SPS response. Moreover, the intensities of PL and SPS signals of TiO2, as well as the photocatalytic activity for degrading phenol solution, can be enhanced by doping an appropriate amount of Zn. These improvements are mainly attributed to the increase in the SOV amount. It can be suggested that the SOVs should play an important role during the processes of PL, surface photovoltage, and photocatalytic reactions, and, for the as-prepared TiO2 samples doped with different amounts of Zn by thermal treatment at 550℃, the larger the SOV amount, the stronger the PL and SPS signal, and the higher the photocatalytic activity.

In this paper, Sn-doped TiO2 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 TiO2 nanoparticles were principally investigated. The results show that an appropriate calcination temperature and Sn dopant amount can greatly enhance the SPS responses of TiO2 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 TiO2 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 TiO2 sample consisting of much of anatase and little of rutile, which is possibly ascribed to the heterojunction between the anatase and rutile phase.

In this paper, we examined the lifetimes of made-in-home ZnO and TiO2 nanoparticles in the gas phase photocatalytic oxidation of n-C7H16 or SO2, and especially investigated the deactivation mechanism by utilizing surface photovoltage spectrum (SPS) and X-Ray photoelectron spectroscopy (XPS) testing techniques and by considering semiconductor chemical properties. The results showed that ZnO could almost be deactivated in the gas phase photocatalytic oxidation of n-C7H16, while TiO2 could keep most of its activity. In the gas phase photocatalytic oxidation of n-C7H16 or SO2, ZnO and TiO2 both could almost be deactivated. The deactivation mainly resulted from semiconductor surface conduction type change from N-type before the photocatalytic reaction to P-type after the deactivation because of the adsorption of the oxidation products such as H2O, CO2 and SO3 on the semiconductor photocatalyst surface. In addition, the activity of the deactivated photocatalyst could be regenerated to a nearly full extent by washing and drying.