Synthesis And Performance Of Nanocomposites Based On Semiconductor Photocatalyst And Upconversion Luminescence Materials

Nowadays,the combination of semiconductor photocatalysts and other functional materials to prepare composite photocatalysts with excellent photocatalytic properties has attracted widespread attention.Rare earth upconversion luminescent materials can convert near-infrared photons into UV or visible light photons through a continuous energy transfer process,they are often used in lighting,imaging and sensing.Semiconductor materials are widely used as photocatalysis because they can produce active species that degrade pollutants under the excitation of light.However,most semiconductor photocatalysts can only have photocatalytic activity under UV or visible light.To extend the spectral response range of semiconductor photocatalysts,combining upconversion luminescent materials to expand the spectral response range is an efficient strategy.In this thesis,we use a simple method to combine semiconductor photocatalysts with rare earth upconversion luminescent materials to construct composite materials with photocatalytic activity under visible and near-infrared light.The details are as follows:（1）Using melamine and different barbituric acid as raw materials,the carbon-doped g-C₃N₄ was synthesized by the hydrothermal method and calcination method.Then,loading Bi F₃:Yb³⁺,Er³⁺upconversion luminescence nanomaterials with different contents on the surface of CNB to prepare a nanocomposite photocatalyst.The nanocomposite materials not only exhibit excellent photocatalytic performance under visible light,but also have good photocatalytic activity under NIR light irradiation.At the same time,they also show good stability.The photocatalytic degradation experiments prove that the nanocomposite material is expected to be applied in the treatment of environmental pollution.（2）The uniform dispersed Na Bi F₄:Yb³⁺,Tm³⁺upconversion nanoparticles and Bi₂WO₆ microspheres were synthesized by precipitation method and hydrothermal method,respectively.Then,with the assistance of PVP,Na Bi F₄:Yb³⁺,Tm³⁺upconversion nanoparticles were modified on the surface of Bi₂WO₆ microspheres to obtain Na Bi F₄:Yb³⁺,Tm³⁺/Bi₂WO₆ nanocomposite materials.The photocatalytic degradation of Rh B test shows that the composite materials have good photocatalytic performance,and the photocatalytic response is successfully extended to the NIR region.In the cycle tests,the nanocomposites show excellent stability,indicating that the nanocomposite materials can provide the possibility for photocatalytic degradation of organic pollutants.（3）Flower-like Bi₂S₃ photocatalyst were synthesized by hydrothermal method.Na YF₄:Yb³⁺,Er³⁺upconversion nanoparticles were modified on the surface of Bi₂S₃ to prepare Na YF₄:Yb³⁺,Er³⁺/Bi₂S₃ nanocomposites.Under visible light irradiation,the prepared composite photocatalyst exhibits enhanced photocatalytic performance and excellent cycle stability.Under NIR light excitation,the nanocomposites still show a certain photocatalytic activity.The results indicate that the prepared nanocomposites with broad spectral response range are good photocatalyst in treatment of organic pollution.