Construction And Properties Of Dual Mode Luminescent Composite Based On Carbon Dot And Rare Earth Luminescent Materials

Carbon dots?CDs?,as a new kind of fluorescent carbon nanomaterials,have attracted more and more attention because of their excellent optical properties,good water solubility,easy surface functionalization and many other advantages.However,carbon dots always have serious self-quenching in solid state,which limits the application in LED lighting,solid-state photoelectric devices,fingerprint development and other fields.Rare earth luminescent materials have important application value in LED display,biomedicine and other fields due to the stable physical and chemical properties,high temperature resistance,the ability of withstanding high energy radiation,stable optical imaging and low spontaneous fluorescence background.Based on the above points,in this dissertation,we have prepared carbon dots,rare earth luminescent materials and composites based on carbon dots and rare earth luminescent materials by hydrothermal method.The multicolor tunable luminescence is realized and the phenomenon of solid-state quenching of carbon dots is supressed.At the same time,the synthesis and energy transfer(CDs,Eu³⁺,Er³⁺,Tm³⁺,Ho³⁺)of the crystals are discussed and studied.The main contents are as follows:1.Using citric acid and urea as raw materials,blue light emission fluorescent carbon dots with excitation independent characteristics were obtained.TheYF₃:Eu³⁺,Tb³⁺/CDs nanocomposites were synthesized by one step hydrothermal method.Under the excitation of 318 nm ultraviolet light,the carbon dots solution produces blue light emission,YF₃:Eu³⁺emits red light,YF₃:Tb³⁺emits green light,and the composites show dual emission of carbon dots and Ln³⁺(Eu³⁺,Tb³⁺)simultaneously.By adjusting the ratio of carbon dots and rare earth phosphors,the light color can be adjusted.Meanwhile,the energy transfer process between carbon dots and Eu³⁺ inYF₃:Eu³⁺,Tb³⁺/CDs can be proved.2.Carbon dots with excitation dependent properties were prepared from citric acid and ethylenediamine.NaYF₄:Yb³⁺,Er³⁺/CDs nanocomposites were prepared by hydrothermal method and liquid-phase method,respectively.The crystal structure and optical properties of namocomposites obtained by different methods are discussed.The energy transfer process between carbon dots and Er³⁺is proved,and the synthesized NaYF₄:Yb³⁺,Er³⁺/CDs nanocomposites have the characteristics of up-down dual mode light emitting.3.The blue emission carbon dots with excitation independence were prepared by using citric acid and ethylenediamine as raw materials.BaYF₅:Yb³⁺,Tm³⁺@CDs and BaYF₅:Yb³⁺,Ho³⁺@CDs composite phosphors were prepared by simple hydrothermal method.The carbon dots act as the double funtion of receiving and supplying electron,and there aretwo-way energy transfer processes between Tm³⁺/Ho³⁺ions and carbon dots,respectively,which enhances the emission intensity of BaYF₅:Ln³⁺@CDs composite phosphor in the red region,and provides the potential for realizing tunable emitting.