Modulation Of Luminescence Properties Of Temperature-sensitive Rare Earth Fluoride Nanomaterials And Their Applications

Rare-earth-doped nanomaterials have received a lot of attention because of their size effect and excellent optical properties in the fields of temperature sensing,white LEDs,fluorescent anti-counterfeiting,bioimaging and solar cells.Rare earth doped nanomaterials with temperature response properties have been widely used in the fields of temperature sensing and fluorescent anti-counterfeiting because of their unique temperature-sensitive fluorescent properties.However,there are still limitations in temperature sensing and fluorescent anti-counterfeiting applications because of the limitations of the emission range and sensitivity of existing temperature-sensitive fluorescent materials.In this paper,we construct a series of temperature-sensitive rare earth-doped nanomaterials with a wide emission range,high temperature response sensitivity and rich emission color in view of the existing problems,the main contents of which are as follows:（1）Study on the luminescence mechanism of temperature-sensitive near-infrared second region fluorescent materials and their applicationsThe rare earth-doped nanomaterials of Tm-Er and Yb-Ho-Nd were synthesized by high-temperature thermal decomposition,and then coated with SiO₂ shells on their surfaces,and finally two materials,NaYF₄:Tm³⁺Er³⁺@NaYF₄@SiO₂ and NaYF₄:Yb³⁺Ho³⁺@NaYF₄:Nd³⁺@SiO₂ were obtained.The successful synthesis of the nanomaterials and the successful encapsulation of the SiO₂ shell layer were demonstrated using XRD,TEM and FTIR.The fluorescence emission spectra of both materials in the near-infrared region will change regularly with temperature changes,which proves their temperature sensing ability,and their temperature sensing performance is evaluated,and the highest relative sensitivity of the two materials is 0.36%K^-1（298 K）and 0.76%K^-1（343 K）,respectively.The biosafety of both nanomaterials was evaluated using cytotoxicity,hemolysis,blood count,and H&E staining experiments,and the experimental results demonstrated that both materials have good biocompatibility and hematological compatibility.The results of in vitro penetration experiments indicate that the prepared nanoparticles have good penetration ability.All experimental results indicate that NaYF₄:Tm³⁺Er³⁺@NaYF₄@SiO₂ and NaYF₄:Yb³⁺Ho³⁺@NaYF₄:Nd³⁺@SiO₂ have good biocompatibility and temperature sensing ability,and have potential applications in deep tissue temperature sensing.（2）Modulation of luminescence properties of multicolor luminescent temperature-sensitive fluorescent materials and their multifunctional applicationsIn view of the problem of low temperature response sensitivity and single function of rare earth doped nanomaterials synthesized in the previous work,we synthesized a series of rare earth doped nanomaterials with good temperature sensing performance and multi-color fluorescence emission properties by introducing NaYbF₄ shell and adjusting the rare earth ion doping concentration.The successful construction of the core-shell structure was demonstrated using XRD,XPS and TEM characterization;The test results of simultaneous differential thermal analysis show that even at a temperature of 800°C,the maximum weight loss of the material does not exceed 8%,indicating that the synthesized material has good thermal stability;Using a fluorescence spectrometer to measure the upconversion fluorescence emission spectra of materials under different conditions（temperature,excitation wavelength,excitation power）,and it was found that the materials under different conditions had rich multicolor fluorescence emission.The synthesized nanomaterials were composed into a series of fluorescent anti-counterfeiting patterns,and their fluorescence photos were taken under different external conditions,and finally high-precision,multi-color and multi-mode dynamic fluorescence anti-counterfeiting was realized.In addition,the analysis of their temperature-dependent fluorescence emission spectra showed that these materials also have the ability of temperature sensing,with a maximum relative sensitivity of 1.1387%K-1（398 K）.This work successfully constructs a multifunctional platform with good temperature sensing ability and fluorescence anti-counterfeiting ability,which provides a new idea for multi-mode fluorescence anti-counterfeiting.In summary,this paper has designed and synthesized a series of temperature-sensitive rare-earth-doped fluoride materials with excellent fluorescence properties by regulating the energy transfer process between rare-earth ions,designing a reasonable core-shell structure,and changing the doping concentration,which expands its application in biological tissue temperature sensing and multi-mode fluorescence anti-counterfeiting,and also enriches the design ideas and basic theories of temperature-sensitive fluorescent materials,providing a reference for the development of temperature-sensitive fluorescent materials.