用于高灵敏度光学测温的Yb^(3+)–Tb^(3+):CsPbI_(3)纳米晶体弥散玻璃

Glasses Containing Yb^(3+)-Tb^(3+):CsPbI_(3) Nanocrystal Glass for High Sensitivity Optical Temperature Measurement

光学温度传感器是利用材料在不同温度下的光学性质变化来测量温度的一种先进传感技术。相比于传统的温度传感器,光学温度传感器具有非接触性、高精度、快速响应和抗干扰能力强的优势。然而,现阶段光学温度传感器仍面临一些挑战,如部分材料温度响应范围有限、复杂环境下测量精度受影响等问题。采用熔融淬火法合成了Yb^(3+)–Tb^(3+):CsPbI_(3)纳米晶弥散玻璃,在365 nm的激发光下产生了来自Tb^(3+)的绿光(^(7)F_(6)–^(5)D_(4)跃迁,545 nm)及来自CsPbI_(3)纳米晶的红光(680 nm)。Yb^(3+)敏化增强Tb^(3+)绿色发光,Tb^(3+)荧光强度随温度变化较为稳定,而CsPbI_(3)纳米晶的红光随温度升高会快速衰减。针对Yb^(3+)–Tb^(3+):CsPbI_(3)纳米晶弥散玻璃的温度传感性能进行表征,发现当Yb_(2)O_(3)浓度为0.3%(摩尔分数),Tb_(4)O_(7)浓度为1.2%时,其绝对灵敏度的最高可达到0.086 K^(–1),相对灵敏度的最高为8.63%K^(–1),最小温度不确定值为0.058 K(298~403 K),表明这种材料在温度传感器中具有潜在的应用前景。

Introduction Optical temperature sensor is based on the change of optical properties of materials at different temperatures.It has the advantages of non-contact,high precision and fast response,and is widely used in industrial and medical fields.However,optical temperature sensors still face some challenges at this stage,such as limited temperature response range of some materials,affected measurement accuracy in complex environments,and high cost.Therefore,improving the temperature measuring range of the sensor,enhancing the anti-interference ability and reducing the cost are the important directions of the current research and development of optical temperature sensors.Rare earth ion has a special electronic structure,5s and 5p orbitals can shield the electron transition in 4f level,so the electronic transition in 4f level is less affected by the external environment,when the external temperature changes,the fluorescence intensity of rare earth ion does not change significantly.The luminescence intensity of CsPbI_(3) nanocrystalline glass varies greatly by external temperature,and the fluorescence quenching phenomenon is easy to occur at high temperature.In this paper,a fluorescence temperature sensor based on rare earth ion and cesium lead halide perovskite nanocrystalline is used to detect the ambient temperature by the ratio of fluorescence intensity of different luminous centers,which has better sensitivity and does not require complex testing instruments.Methods The glass with the nominal compositions of 41GeO_(2)-25B_(2)O_(3)-8ZnO-3.6PbI_(2)-5.4Cs_(2)O-11NaI-5SrO-1NaF-1.2Tb_(4)O_(7)-yYb_(2)O_(3)(where y=0,0.3%,0.6%,0.9%,1.2%,in mole fraction denoted as Y-1,Y-2,Y-3,Y-4,Y-5 respectively),were prepared by melt-quenching method.The Tb^(3+)–Yb^(3+):CsPbI_(3) NCs glass were synthesized by subsequent heat treatments.The raw materials were well-mixed and then put into the alumina crucible.The glass batch were melted at 1200℃for 30 minutes,and the molten glass were poured and pressed into sheets,subsequently annealed to release thermal stresses.These glass sheets were heat treated at various conditions and then optical polished for structural and performance characters.Results and discussion XRD and TEM analyses reveal that the lattice structure is belonged to CsPbI_(3) NCs,with the incorporation of Tb^(3+)and Yb^(3+).Upon excitation with 365 nm,Tb^(3+)undergoes transitions from ^(7)F_(6) to ^(5)D_(3),followed by the emission of distinct wavelengths at ^(5)D_(4)-_(7)F_(6)(485 nm),^(5)D_(4)-^(7)F_(5)(545 nm),and ^(5)D_(4)-^(7)F_(4)(585 nm),indicating a non-radiation relaxation to the ^(5)D_(4) level.The energy difference between the ^(5)D_(4) and ^(7)F_(6) states in Tb^(3+)precisely twice than that of the transition from the state ^(2)F_(5/2) to the ground state ^(2)F_(7/2) for excited Yb^(3+),allowing Tb^(3+)to absorb a single high-energy photon and transfer the energy from ^(5)D_(4) to two Yb^(3+)ions.Thus two low-energy NIR photons are emitted:Tb^(3+)(^(5)D_(4))→Yb^(3+)(^(2)F_(5/2))+Yb^(3+)(^(2)F_(5/2)).The energy transfer between Tb^(3+)and Yb^(3+)ions is confirmed by the NIR fluorescence spectra.When the glass without heat treatment excited by 365 nm laser,but Yb^(3+)luminescence peak appears at 950–1100 nm,confirming that there is an energy transfer process from Tb^(3+)to Yb^(3+)since the sole Yb^(3+)ion cannot be excited by 365 nm laser.Moreover,the infrared luminescence intensity increases with the increase of Yb^(3+)concentration,indicating that the probability of Tb^(3+)transferring energy to Yb^(3+)increases with the increase of Yb^(3+)concentrations.As the concentration of Yb^(3+)increased,the fluorescence intensity of Tb^(3+)also increase in the un-heat-treated glasses.Since there are no nanocrystals in the glass matrix,it was speculated that there was a back energy transfer process from Yb^(3+)to Tb^(3+).In the presence of CsPbI_(3) NCs,it is found that the lifetime of CsPbI_(3) NCs is almost the same before and after adding rare earth ions,indicating that there is no energy transfer between nanocrystals and rare earth ions.The fluorescence lifetime of Tb^(3+)was found to be enhanced with the increase of Yb^(3+)concentration,indicating the existence of back energy transfer process from Yb^(3+)to Tb^(3+).Because the luminous intensities of Tb^(3+)and CsPbI_(3) NCs have different sensitivity to temperature,good self-calibration temperature measurement performance can be obtained by using their luminous intensity ratio with temperature change.In this work,when Tb^(3+)is 1.2 mol%and Yb^(3+)is 0.3 mol%,the Tb^(3+)–Yb^(3+):CsPbI_(3) NCs glass exhibit the best temperature sensitivity.Conclusions The main conclusions of this paper are as follows.The optical temperature sensor was prepared by using Tb^(3+)and CsPbI_(3) NCs with different luminous colors and different sensitivity to temperature.Under the excitation of 365 nm light,Yb^(3+)emits light,and with the increase of Yb^(3+)content,the luminous intensity of Tb^(3+)increases.Since Yb^(3+)cannot absorb the at 365 nm light,there is an energy transfer from Tb^(3+)to Yb^(3+).The energy transfer mechanism is as follows:Firstly,Tb^(3+)(^(5)D_(4))→Yb^(3+)(^(2)F_(5/2))+Yb^(3+)(^(2)F_(5/2))energy transfer process occurs,leading to the emission of 1020 nm near-infrared light from Yb^(3+);Then,Yb^(3+)(^(2)F_(5/2))+Yb^(3+)(^(2)F_(5/2))→Tb^(3+)(^(5)D_(4))occurs back energy transfer process,and Tb^(3+)luminescence is enhanced.Using the fluorescence intensity ratio between the ^(5)D_(4)–^(7)F_(4)(545 nm)emission of Tb^(3+)and the emission of CsPbI_(3) NCs at 680 nm,the temperature sensor with high sensitivity(SA=0.086 K^(–1),SR=8.63%·K^(–1),δT_(min)=0.058 K,298~403 K)has been prepared,which has potential in the application of optical temperature sensor.