Synthesis And Application Exploration Of Several Rare-earth Upconversion And Lead Halide Perovskite Luminescent Materials

In recent years,rare earth upconversion luminescent materials have received extensive attention in the fields of substance detection,bioimaging,photodynamic therapy,three-dimensional display,and signal sensing due to their unique physical and chemical properties(narrow emission band,long fluorescence lifetime,high light stability,large back-Stokes shift,low autofluorescence,no photobleaching and light scintillation,low toxicity and the light damage to biological tissues,etc.).Through functional modification,rare earth-doped nanomaterials can be effectively combined with several photothermal diagnosis and treatment reagents to build a nano diagnosis and treatment platform guided by multi-modal imaging.All-inorganic lead halide perovskite materials are widely used in photovoltaics and solid-state light-emitting diodes,X-ray detectors and imaging,photoelectric detectors and other fields due to their excellent photoelectric properties(emission wavelength is easy to adjust,broad spectrum absorption,large extinction coefficient,high fluorescence emission efficiency,narrow emission spectrum,etc.).However,the ionic nature and low formation energy of perovskite materials make them extremely susceptible to environmental pressures such as light,oxygen,heat and moisture,and they are extremely easy to decompose in the presence of water.However,water will inevitably be encountered in the material synthesis and device manufacturing process,which will seriously affect the stability and performance of the device.Therefore,improving the water stability of the perovskite material and extending the working life of the device are essential for its future commercial applications.In this paper,several luminescent materials are designed and synthesized,and the rare earth up-conversion luminescent materials are effectively combined with several photothermal diagnosis and treatment reagents to build a multi-functional nano diagnosis and treatment platform for cancer treatment guided by multi-mode imaging.In addition,a water-stable lead halide perovskite luminescent material was successfully prepared,and the performance of light-emitting diodes was studied.The specific content is summarized as follows:1.The monodisperse NaYF4:Yb/Er/Cu upconversion nanocrystals were prepared by solvothermal method.The successful co-doping of Cu2+ ions not only achieved the simultaneous control of the crystalline phase/morphology of NaYF4:Yb/Er crystals,but also the emission intensity of green and red light upconversion of 60%mol Cu2+doped NaYF4:Yb/Er nanocrystals is increased by 37 and 25 times compared with undoped NaYF4:Yb/Er nanocrystals.NaYF4:Yb/Er/Cu upconversion nanocrystals were used to realize an optical temperature sensor excited by 980 nm in a wide temperature range,which can be used as a high-sensitivity temperature sensor.2.A general in-situ growth methode was developed to grow ultra-small metal sulfide(Mn+S,M=Ag,Cu,Cd)quantum dots(QDs)uniformly on on the surface of chitosan(CS)modified NaYF4:Yb/Er upconversion nanocrystals.Taking Ag2S as an example,the growth behavior of Ag2S QDs on the surface of NaYF4:Yb/Er@CS is studied.The effects of Ag:Y ratio,S:Ag ratio,pH value,reaction time and reaction temperature on the growth behavior of Ag2S on the surface of NaYF4:Yb/Er@CS were systematically studied.The resulting NaYF4:Yb/Er@CS@Ag2S nanocomposite platform not only has the upconversion luminescence(UCL)characteristics of NaYF4:Yb/Er,but also has the good photothermal conversion effect of Ag2S.At the cellular level,the potential value of NaYF4:Yb/Er@CS@Ag2S nanocomposites in the field of UCL imaging guided photothermal therapy(PTT)is proved.3.A new type of NaYF4:Yb/Er@NaLuF4:Nd/Yb@NaLuF4@CS@Ag2Se(labeled as UCNPs@CS@Ag2Se)multifunctional diagnosis and treatment platform was prepared.The material can realize upconversion(UC)and down-conversion(DS)luminescence in NIR ? and ? biological window regions under the excitation of 808 nm laser.At the same time,the attached Ag2Se nanodots will produce high temperature under 808 nm laser irradiation.The nanocomposite not only integrates the unique optical properties,CT imaging capabilities of UCNPs and the excellent photothermal conversion capabilities and photoacoustic effects of Ag2Se nanodots,but also has good biocompatibility and negligible toxicity.These excellent properties prove the potential application value of UCNPs@CS@Ag2Se nanocomposite in the field of UCL/DSL/CT/PA multimodal imaging guided PTT.4.A new multifunctional NaYF4:Yb/Er@NaYF4:Yb-Cu2-xS(labeled as UCNPs-Cu2-xS)core/shell/satellite structure nanoplatform was designed.Among nanocomposites,UCNPs with excellent luminescence properties and high X-ray attenuation coefficient can be used as contrast agents for UCL and CT imaging,and Cu(?)in Cu2-xS nanodots can be used as magnetic resonance imaging(MRI)agents.In addition,Cu2-xS nanodots with high absorbance in the NIR ? region can not only be used as a stable photothermal agent under near-infrared laser irradiation,but also Cu(?)in Cu2-xS nanodots could respond to over-expressed H2O2 in tumor microenvironment and generate toxic hydroxyl radicals(·OH)to effectively kill cancer cells.Furthermore,UCNPs-Cu2-xS nanocomposites have negligible cytotoxicity and high photothermal conversion efficiency,indicating that they have great potential for UCL/CT/MR multimodal imaging-guided chemodynamic therapy(CDT)/PTT of cancer.5.A facile synthesis strategy was explored to synthesize ultra-stable CsPbBr3/CsPb2Br5@PbBr(OH)(PQDs@PbBr(OH))nano/microspheres through a water-assisted process.These PQDs@PbBr(OH)nano/microspheres can still maintain excellent photoluminescence(PL)intensity and high photoluminescence quantum yield(PLQY?90%)after immersing in water for more than 18 months.The crystal phase,particle size and PL peak position of the nano/micro spheres can be adjusted by changing the water content in the reaction mixture.Compared with the CsPbBr3/Cs4PbBr6 nanocrystals(NCs)obtained in the anhydrous system,the nano/microspheres have ultra-high water stability,thermal stability and light stability.Finally,based on the excellent stability of PQDs@PbBr(OH),we successfully fabricated LED devices,which have excellent stability and high luminous efficiency,confirming that the material has potential application value in the field of LEDs.