Reaserch On Photoluminescence Properties And Temperature Measurement Mechanism Of Rare Earth Doped Micro-nano Materials

The spectral characteristics of rare earth doped luminescent materials are closely related to temperature.The non-contact temperature measurement technology based on rare earth ions can effectively avoid the adverse effects of ambient factors,pump source and autofluorescence interference on temperature detection,so temperature measurement is made in the special places such as power stations,coal mines and living organisms.However,its application has been restricted due to the low photo-fluorescence efficiency of rare earth ions.In addition,the sensitivity of fluorescence intensity ratio thermometry based on the rare earth ion's thermal coupling energy level is difficult to further improve,due to the thermal coupling energy level difference is limited to 200-2000 cm^-1.The related research works were carried out on the above two issues in this paper.The rare earth ions doped fluoride nanoparticles and NaY?WO₄?₂:Yb³⁺-Er³⁺phosphor materials were prepared by solvothermal method and high temperature solid phase method,respectively.Under near-infrared light excitation,the photoluminescence properties of the above luminescent materials were systematically studied.And the temperature sensing characteristics were also explored.The specific research works is as follows:In order to enhance the upconversion luminescence properties of Tm³⁺ions,the composite shell nanoparticles with core/shell/shell structure were constructed.Under the excitation of 980 nm laser,it was found that the short-wavelength up-conversion emission of Tm³⁺ions was significantly enhanced.At the same time,the corresponding fluorescence enhancement mechanism was analyzed,and the correlation between the fluorescence decay curve and the temperature corresponding to the fluorescent band with the peak at450 nm was discussed.The study found that there is a good linear relationship between the fluorescence lifetime of the¹I₆ level and the temperature,and the maximum sensitivity of0.785%K^-11 is obtained at 423 K.The photoluminescence of NaYF₄:Yb³⁺-Tm³⁺nanoparticles in the near-infrared region was studied by 980 nm near-infrared laser pumping.The relationship between emission fluorescence and temperature was analyzed.It was found that the change trend of fluorescence intensity corresponding to the ²F_5/2?²F_7/2/2 level transition of Yb³⁺are opposite to the fluorescence intensity corresponding to the³F₄?³H₆ level transition of Tm³⁺,and then the intrinsic physical mechanism leading to this change trend is analyzed.The exploration of temperature measurement is based on the ratio of the two fluorescence intensities,it is found that the fluorescence intensity ratio has a good linear relationship with temperature in the temperature range of 293 K-423 K,which is suitable for two near-infrared"biological window"temperature measurement.and the maximum sensitivity at 293 K is 1.84%K^-1,which is higher than the sensitivity value of rare earth luminescent materials in the previous reports.The near-infrared fluorescence and temperature sensing characteristics of NaY?WO₄?₂:Yb³⁺-Er³⁺phosphors were studied by 915 nm near-infrared laser pumping.It was found that the near-infrared fluorescence temperature measurement can be conducted by utilizing the fluorescence intensity ratio between the fluorescence peak of 1016 nm and the fluorescence peak of 1530 nm of Er³⁺ions in temperature region of 303 K-723 K,reaching a maximum relative sensitivity of 1.5%K^-11 and a maximum absolute sensitivity of 0.87%K^-11 at 302 K and 690 K,respectively.