Long Persistent Luminescence Assistant Photocatalytic And Persistent Photocatalysis Effect

Photocatalysis(PC)have attracted more and more widespread attention in environmental treatment.The titanium dioxide(TiO2)as a most useful photocatalyst has been widely used for the environmental treatment due to its strong oxidizing power,non-toxicity,high photochemical corrosive resistance and cost effectiveness when compared with the other candidates.However,the photocatalytic degradation using TiO2 requires continuous ultraviolet light irradiation and thus it doesn't work when the light source is not present.In order to support photocatalytic decomposition of TiO2 for organic pollutant at night or in low-transparent wastewaters,we synthesize a highly efficient ultraviolet emitting Long persistent luminescence(LPL)CdSiO3:Gd3+,Bi3+.The long lasting phosphorescence spectra can adjusted by changing the content of Bi3+ co-dopants and approximately 68.7% of the spectral areas can well match the absorption band of TiO2.The long lasting phosphorescence of the optimal CdSiO3:0.5%Gd3+,0.5%Bi3+ sample can last about 6 hours,even using the threshold value of the 0.32mcd/m2.In order to evaluate its ability to assist TiO2 catalysts,the functional CdSiO3:Gd3+,Bi3+@TiO2 composite was synthesized by a sol-gel method.The subsequent characterization of the composite demonstrated that the TiO2 nano-particles were successfully coated onto the surface of CdSiO3:Gd3+,Bi3+ particles.The unique ability of CdSiO3:Gd3+,Bi3+ to assist the photocatalytic activity of TiO2 was evaluated through investigations of the decomposition of methylene blue.The results revealed that the efficient ultraviolet long lasting phosphorescence of CdSiO3:Gd3+,Bi3+ can not only support the photocatalytic activity of TiO2 in the absence of ultraviolet light but also significantly increases the photocatalytic activity per unit mass of TiO2 under ultraviolet irradiation.Thus,this obtained CdSiO3:Gd3+,Bi3+@TiO2 composite can be potentially used as an efficient functional photocatalyst to treat the organic pollutants at night or in low-transparent wastewater.However,Use LPL to support a photocatalyst consists of the complex and indirect energy transfer processes: light source ? LPL material ? PC material;and thus the energy transfers are inefficient.In additional,the LPL light can be badly quenched in the water and the absorption efficiency of LPL light by photocatalyst is not sufficient.Therefore,the present LPL assistant PC materials suffer from their own drawbacks.By combining the physical and chemical processes of the photocatalysis and the long persistent luminescence,it is the first time that we design a new concept called the “Long Persistent Photocatalysis(LPPC)”.According to this concept we use a hydrothermal method to fabricate typical LPPC MgGa2O4 nanorodes.The Rh B decomposition experiments indicate that,after removing the irradiation light source,the MgGa2O4 nanorodes are still able to constantly degrade RhB in dark,due to the LPPC effect.Although the present LPPC efficiency of the MgGa2O4 nanorodes is actually weak at this preliminary stage,this interesting discovery is still significant and of course enables the LPPC materials to find potential photocatalysis applications in the absence of irradiation light source.In order to solve the low efficiency of visible light absorption of MgGa2O4 materials,We developed a new LPPC material: black peony-like BiOCl.It is found that the black peony-like BiOCl material is able to efficiently degrade rhodamine B dye after removing the visible irradiation light,just like persistent luminescence of phosphor.The discovery of LPPC effect provides a potential solution to realize full-time photocatalytic applications.The LPPC effect was justified through a serial of the decomposition experiments,and its potential prospect of full-time application was evaluated by the exp eriments as well.On the basis of the results,a possible LPPC mechanism of the black peony-like BiOCl material has been proposed.