Optical And Photocatalytic Properties Of Tungsten-molybdenum Synergistic Sensitization For Rare Earth Doped Titanium Dioxide

Upconversion(UC)luminescence has been widely used in illumination,temperature sensing and biological imaging due to its high luminescence efficiency.As a common UC matrix material,titanium dioxide(TiO2)has a simple preparation method,excellent thermal and chemical stability.Molybdenum ions loading greatly improves the up-conversion luminescence efficiency of rare earth doped TiO2.Similarly,some self-doped metal oxide semiconductors have favourable localized surface plasmon resonance(LSPR)effect,which is also helpful to improve the UC luminescence efficiency.Moreover,the hot electrons produced by LSPR can enhance the photocatalytic performance.By combining UC fluorescent materials and semiconductor with LSPR effect,the UC luminescence and photocatalytic properties are explored effectively for promoting UC luminescence efficiency and solving increasingly serious energy problems.The following are the main research contents:(1)Different morphology of titanium dioxide codoped with erbium and ytterbium(Er-Yb:TiO2)is synthesized by sol-gel method and hydrothermal process.To characterize the morphology of Er-Yb:TiO2,the scanning electron microscopy(SEM)is measured.The results of X-ray diffraction(XRD)further show the crystal structure of as-prepared sample.In order to certify the UC property of Er-Yb:TiO2,utilizing 980 nm laser as excitation source,stronger red emission and weaker green emissions are observed.The photon process fitting indicates the green and red UC luminescence of Er-Yb:TiO2 are two-photon process.(2)Molybdenum supported titanium dioxide codoped with erbium and ytterbium(Mo/Er-Yb:TiO2)is successfully synthesized by using ammonium molybdate as molybdenum source and TiO2 prepared by sol-gel method as a titanium source.The SEM is tested so that ensure the morphology of Mo/Er-Yb:TiO2,which infers regular eight prism structure.XRD results further make sure the crystal structure,which indicates a new material,namely Yb2(MoO4)3.For examining the UC capacity of Mo/Er-Yb:TiO2,under the excitation of 980 nm laser,extremely intense green emissions and weak red emission are obtained.Moreover,the sensitivity of Mo/Er-Yb:TiO2 is larger than that of Er-Yb:TiO2 in temperature sensing.This way of transition metal ions supporting provides a novel method to enhance the UC luminescence efficiency.(3)The semiconductor material W18O49 with LSPR effect is grown on FTO conductive glass by solvothermal method.Er-Yb:TiO2 prepared via solvothermal method is assembled on the surface of W18O49 film through self-assembly process.The SEM,XRD and EDS measurements show that the Er-Yb:TiO2 is distributes on the W18O49 uniformly,which demonstrates that the Er-Yb:TiO2/W18O49/FTO nanofilm is synthesized successfully.UV-Vis-NIR absorption spectra further certify the LSPR effect of W18O49.Under the action of LSPR,the UC luminescence intensity of Er-Yb:TiO2/W18O49/FTO nanofilm is increased by one order of magnitude than that of Er-Yb:TiO2/FTO nanofilm.This strategy of employing the LSPR effect explores new UC intensity enhancement method effectively.(4)W18O49 nanowires are grown on Mo/Er-Yb:TiO2 by solvothermal method(Mo/Er-Yb:TiO2@W18O49).To explain the morphology of the sample,the SEM is measured,the result of which shows that the rod-like morphology is observed.XRD patterns further ensure the crystal structure.For confirming the Mo/Er-Yb:TiO2 is coated inside of W18O49,EDS examination is executed,which tests the elements species and determines the quasi-core@shell structure.Upon 980 nm laser irradiation,Mo/Er-Yb:TiO2@W18O49 has better properties than pure W18O49 In hydrogen production by decomposition of boron ammonia(BH3NH3)under the LSPR effect.It proves that the UC emissions play a crucial role in photocatalytic reaction.This supplies an efficient way for producing clean energy.