Study On Temperature Sensing Mechanism Of Rare Earth Doped Up-conversion Luminescent Materials Based On Fluorescence Intensity Ratio

Rare earth luminescent materials stand out for their excellent luminescent properties,stability and biosafety in material optical response temperature sensing.Among them,rare earth ions fluorescence intensity ratio?FIR?temperature sensing method has attracted much attention because of its non-intrusive mode,fast response,self-reference and high sensitivity.These unique advantages also make the application of FIR temperature measurement methods in scientific research,production and life gradually increased.However,in order to meet the needs of high precision temperature measurement in some fields such as precision equipment and clinical medicine,it is imperative to improve the sensitivity of temperature sensor.For this reason,we will discuss thermal coupling levels fluorescence intensity ratio?TCL-FIR?temperature sensor and non-thermal coupling levels fluorescence intensity ratio?NTCL-FIR?temperature sensor based on YbPO₄,BaTiO₃,NaYb?MoO₄?₂,LaAlO₃ and Y₂O₃ respectively.Through theoretical analysis and experimental verification,methods to improve the accuracy of temperature measurement are explored,and related applications are discussed.The application of fluorescence intensity ratio temperature sensor in biological system is preliminarily explored.Specific research contents are as follows:?1?The YbPO₄ nanoparticles have been successfully synthesized and doped with Tm³⁺-Yb³⁺,Er³⁺-Yb³⁺,Ho³⁺-Yb³⁺ion pairs.The difference and relationship between absolute sensitivity S_a and relative sensitivity S_r are discussed through theoretical analysis and experimental verification.The relationship between S_r,S_a and energy level difference??E?is obtained by deducing their defining formulas.Using this relationship,we can predict the optimal temperature sensing range of a given matrix material,or choose the best temperature sensing matrix according to the target temperature sensing range.This study will be conducive to the better application of thermal coupling level temperature measurement method in practice.?2?The temperature dependence of radiation intensity of non-thermal coupling levels is discussed by using Arrhenius equation and the NTCL-FIR temperature sensing method was proposed.The NTCL-FIR temperature sensing model exhibited extremely low temperature uncertainty??0.27 K?,ultrahigh temperature sensitivity(>10%K^-1)and satisfactory signal recognition ability.Compared with the traditional TCL-FIR temperature sensing model,the maximum absolute sensitivity S_a of the NTCL-FIR temperature sensor was improved by 2 order of magnitude,reaching 44.90%K^-11 at 573K and the maximum relative sensitivity S_r of the NTCL-FIR temperature sensor increased by nearly 10 times,reaching 1.85%K^-1 in this work.Besides,the NTCL-FIR model was not restricted to single luminescent center for temperature sensing,but was also applicable among the cases of double luminescent centers.In addition,we have applied the novel NTCL-FIR temperature sensor to liquid temperature measurement system based on NaYF₄:Tm³⁺,Yb³⁺@NaYF₄ core-shell structure,which was expected to be used for accurate temperature measurement in vivo.All of these results indicate that the designed NTCL-FIR temperature sensor have great potential for future applications.And it not only has important significance to improve the temperature detection performance but also provides inspiration and reference for practical development of rare earth ions-based temperature detectors.