Upconversion Luminescence Of Rare Earth Ions Codoped Materials And Its Temperature Characteristics

Rare-earth-ion(RE³⁺)doped up-conversion luminescent materials have great potential in the application of temperature sensors and bio-fluorescent labeling,etc.The fluorescence intensity ratio measurement（FIR）technology based on such materials,which been widely used,has the advantages of anti-interference,high sensitivity and good spatial resolution.For FIR thermometry,the laser excitation is very important,which not only can avoid the interference of autologous or background fluorescence,but also improve the signal-to-noise ratio.However,some studies shown that the excitation radiation will introduce thermal effects and will seriously reduce the accuracy of temperature measurement.Secondly,the phenomenon of fluorescence heat quenching is widely existed and narrowed the thermometry range and reduce the accuracy too.In this paper,based on several RE³⁺co-doped up-conversion materials,the laser induced thermal effect and fluorescence heat enhancement phenomena are studied,respectively.Based on the NaYF₄:Yb³⁺-Er³⁺nanoparticles,the influence of Yb³⁺doping on laser thermal effect was studied.Under 980 nm laser excitation,the effect of Yb³⁺doping on the up-conversion fluorescence of Er³⁺was discussed.The thermal coupling energy level（TCL）of Er³⁺,⁴S_3/2/2 and ²H_11/2,were used to characterize the temperature.In the power range of 0.25-2.25 W/cm²,the relationship between the Yb³⁺doping ratio and the temperature deviation introduced by the laser thermal effect was analyzed,It is showing that the thermal effect will be introduced even at very low pump power,and the higher the Yb³⁺doping ratio,the more severe the thermal effect;based on the CaWO₄:Eu³⁺phosphor,the above experiment was improved.It is found that the Yb³⁺doping ratio is linearly related to the deviation caused by the 980nm laser thermal effect,and that a 1%increase in Yb³⁺introduces an error of about 0.3 K.In practice,In practice,we can choose the appropriate pump source and sensing material according to the conclusion,and optimize the measurement design to get higher temperature measurement accuracy.Based on Yb³⁺-Nd³⁺calcium phosphate glass,the near-infrared fluorescence enhancement of Nd³⁺and its temperature sensing characteristics were studied.Under the excitation of 980nm laser,the three NIR fluorescence peaks of Nd³⁺increased with increasing temperature,which implies that the sensitization of Yb³⁺was successfully used to enhance the fluorescence.The three thermal coupling energy of Nd³⁺were further discussed and the one which have the highest sensitivity was given.The uncertainty of temperature measurement at 785 K is about 10 K,which proves that it has the potential for temperature measurement in high temperature areas.