Research On Temperature Sensing Technology Based On Near-infrared Luminous Micro/nano Materials

Temperature is related to the normal operation of human production and life,and its importance is self-evident.With the rapid development of science and technology,higher standards are required for temperature measurement.At present,the fluorescence intensity ratiometric temperature measurement technology based on rare earth ion doped luminescent materials has become a hot spot in the field of temperature sensing.However,this kind of temperature measurement technology usually uses the thermal coupling energy levels of rare earth ions,and its temperature measurement sensitivity is limited by the size of the energy level gap of the thermal coupling energy levels.In addition,the fluorescence spectrum tends to overlap.Therefore,the temperature measurement error obtained by using the thermal coupling energy level to achieve the fluorescence intensity ratiometric temperature measurement is relatively large and the sensitivity is low.In view of the key problems in the field of fluorescence temperature measurement listed above,this paper adopts measures such as selecting suitable host materials,controlling synthesis conditions,optimizing the doping concentration of rare earth ions and building core-shell structures to optimize the temperature sensing performance.The luminescence mechanism of the studied rare earth ions doping system is theoretically explored,and its temperature sensing characteristics and potential application value are evaluated.The main research contents of this paper are as follows:In the study of the temperature sensing properties of near-infrared luminescent nanomaterials,fluoride with relatively low phonon energy was used as the host material,and Yb³⁺and Tm³⁺were doped in it.The core,core/shell,and core/shell/shell structure of nanocrystals were prepared by solvothermal method,the microstructure of the synthesized nanocrystals was characterized.In addition,the luminescence mechanism of Tm³⁺under980 nm laser excitation was discussed in detail,and the temperature-dependent emission spectra based on the Tm³⁺:³H₄?³H₆ and ³F4?³H₆ transitions were measured.The emission peak centered at 800 nm is located in the wavelength range of the first biological transparency window,and the emission peak centered at 1800 nm is located in the wavelength range of the third biological transparency window.This study also systematically analyzed the effect of the shell coating on the Tm³⁺luminescence process and fluorescence lifetime,and further evaluated the temperature sensing performance of the ³H₄ and ³F₄energy levels.It was found that the core/shell/shell structured nanocrystals showed up-conversion fluorescence intensity saturation.The near-infrared fluorescence intensity ratio is almost independent of the pump power,which can realize high-reliability temperature detection.The maximum absolute and relative sensitivity of temperature measurement are S_{a Max}=3.9%K^-1 and S_{r Max}=0.33%K^-1 in the physiological temperature range,respectively,and the temperature measurement uncertainty is 0.75 K.At present,there are some problems that need to be solved in the field of biological temperature measurement.The temperature measurement of deep tissue cannot be realized and the temperature measurement sensitivity is relatively low,etc.,and near-infrared light can reduce the scattering and absorption of biological tissues,so near-infrared fluorescence is suitable for biological temperature measurement.The Yb³⁺and Tm³⁺co-doped system can use near-infrared luminescence to measure temperature,and has superior temperature sensing performance,which proves that the near-infrared temperature measurement strategy designed in this paper has a huge application prospect in the field of biological temperature measurement.In the study of temperature sensing characteristics of near-infrared luminescent micron materials,the host material is Na Y(WO₄)₂ with polarization and low phonon energy,in which Yb³⁺and Er³⁺are doped.A series of microcrystalline materials were prepared by high-temperature solid-phase method,and their microstructures were characterized.Under the non-resonant pumping of 915 nm laser,the near-infrared photoluminescence characteristics and temperature characteristics of this series of microcrystalline materials were studied.From the temperature-dependent emission spectrum of the microcrystalline material,the physical mechanism of the luminescence under 915 nm laser excitation is inferred.The luminescence and temperature spectra are comprehensively analyzed in combination with the rate equation.A physical model was found that led to the opposite change of Yb³⁺and Er³⁺co-doped luminescence.The above physical model was discussed in detail by using the influence of temperature on the fluorescence lifetime of Er³⁺'s ⁴I_13/2energy level.The temperature sensing of the series of microcrystalline materials with different Yb³⁺doping concentrations was also studied,and the influence of different Yb³⁺doping concentrations on the luminescence and temperature characteristics was discussed.The temperature measurement performance was evaluated by using temperature measurement sensitivity.The maximum sensitivity of micron crystals with a Yb³⁺doping concentration of 9%is S_{a Max}=0.0108 K^-1.In order to achieve the optimization of temperature sensing performance,the ²H_11/2 and ⁴S_3/2 energy levels of Er³⁺are not used for the ratiometric temperature measurement of fluorescence intensity.Instead,temperature detection is performed through non-thermally coupled energy levels,which breaks the limitation of energy level gap on temperature measurement sensitivity.It is proved that the use of non-thermal coupling energy levels can effectively improve the temperature measurement sensitivity,and it also shows that the Yb³⁺-Er³⁺co-activated phosphor has great development potential in the field of temperature sensing.