A Lu-based 1-x Eu x Temperature measurement method based on the fluorescence thermosensitivity of NbO4 and its application

Abstract

The present invention discloses a temperature measurement method and its application based on the fluorescence and thermal sensitivity characteristics of Lu 1‑x Eu x NbO4. Using Lu 1‑ x Eu x NbO4 (0.005 < x < 0.05) as the temperature-sensitive material, ultraviolet light with a wavelength of 200 - 300 nm is used to excite Lu 1‑x Eu x NbO4 to emit light, and the emission spectrum of the material in the wavelength range of 300 - 750 nm is detected. Then, two methods are used to calibrate the temperature: calculate the ratio R of the integrated emission intensity of the material in two wavelength ranges of 300 - 520 nm and 520 - 750 nm, and obtain the temperature to be measured according to the temperature change curve of R; calculate the ratio r of the peak intensity of the material emitting light in the range of 300 - 520 nm and the emission intensity of the material at 613 nm, and obtain the temperature to be measured according to the temperature change curve of r. The present invention is a non-contact temperature measurement method with the characteristics of high sensitivity and fast response, and can be applied to temperature measurement at the sub-micron or even nano scale, and can also be used for temperature measurement of biological cells.

Description

Technical Field

[0001] The present invention relates to the field of temperature detection based on optical sensing, and in particular to a temperature sensor based on luminescent material Lu 1- x Eu x A new method for temperature detection based on the fluorescence thermosensitive properties of NbO4 and its application. Background Art

[0002] Temperature is a fundamental thermodynamic quantity. Within the sensor field, temperature sensing accounts for nearly 80% of applications. Accurate temperature measurement is crucial in scientific research, technological development, and engineering applications. Traditional thermometers utilize contact-based temperature measurement, severely limiting their speed and accuracy. This limitation cannot meet the high-speed, high-precision temperature measurement requirements of modern energy, information, and biology. For example, traditional temperature measurement methods cannot measure temperatures at the submicron or even nanometer scale, nor can they measure temperatures within biological cells. Consequently, non-contact temperature detection based on optical sensing has become a hot topic of research, as it overcomes the limitations of traditional contact thermometers.

[0003] Within a certain temperature range, the temperature-dependent changes in certain optical properties of luminescent materials, such as peak position, fluorescence intensity, spectral linewidth, polarization anisotropy, and fluorescence lifetime, can be used to calibrate temperature. This new temperature measurement technology, which utilizes the thermal sensitivity of a material's optical response to detect temperature, can meet the requirements of non-contact, high-resolution, and fast-response detection.

[0004] Temperature detection based on the fluorescence intensity ratio of the rare earth ion thermal coupling energy level is considered to be a temperature measurement technology with great application prospects. It calibrates the temperature by measuring the intensity ratio of the emission peak corresponding to the rare earth ion thermal coupling energy level transition. Since the energy difference of rare earth ions is not large after being excited (generally between 200-2000cm -1 The electron distribution on the two energy levels of Er will reach thermal equilibrium in a very short time, forming a pair of thermally coupled energy levels. Changes in temperature will cause changes in the number of electrons distributed in the two energy states. Therefore, the intensity ratio of the luminescence from the two energy levels changes with temperature. For example: Er 3+ The main luminescence energy level of the ion 2 H 11 / 2 and 4 S 3 / 2 It is a pair of thermally coupled energy levels, using 980nm infrared light to excite Er 3+ , Yb 3+ Co-doped NaYF4 phosphor NaYF4:20% Yb 3+ ,2% Er 3+ ,because 2 H11 / 2 → 4 I 15 / 2 and 4 S 3 / 2 → 4 I 15 / 2 The fluorescence intensity of the electron transition luminescence gradually increases with the increase of temperature. 2 H 11 / 2 and 4 S 3 / 2 The fluorescence intensity ratio of the energy level transition to the ground state emission can be used to calibrate the temperature in the range of 160-300K. 3+ Ionic 5 F1 / 5 G6 and 5 F 2,3 / 3 The K8 energy level is also a pair of thermally coupled energy levels. 980nm infrared light is used to excite NaLuF4:10% Yb 3+ ,0.5% Ho 3+ Powder luminescence, measurement 5 F1 / 5 G6→ 5 I8 and 5 F 2,3 / 3 K8→ 5 The luminescence intensity ratio of the I8 electron transition varies with temperature, allowing temperature measurements to be made within the range of 390K to 780K. This temperature measurement method is less dependent on measurement conditions and is not limited by fluctuations in the excitation light source intensity or non-temperature factors such as the number and distribution of luminescence centers, which can cause changes in luminescence intensity. Consequently, measurement errors are minimal, making it a new, highly accurate, non-contact temperature measurement method.

[0005] However, the relative sensitivity of the temperature detection method based on the fluorescence intensity ratio of the thermal coupling energy levels of rare earth ions is proportional to the energy difference ΔE between the two thermal coupling energy levels. In order to avoid "decoupling", ΔE is generally less than the energy of 4-5 matrix phonons. Therefore, the relative sensitivity of this method to temperature is not high. For example: using NaYF4:20% Yb 3+ ,2% Er 3+ The relative sensitivity of powder as a sensitive material for temperature measurement at 300K is only 1.20%·K -1 Similarly, NaLuF4:10% Yb 3+ ,0.5%Ho 3+ When the powder is used as a sensitive material for temperature measurement, the relative sensitivity at 500K is only 0.83%·K -1 Therefore, how to improve the temperature sensitivity of luminescent materials is one of the main technical problems faced by the temperature detection method based on the fluorescence intensity ratio of the thermally coupled energy levels of rare earth ions.

[0006] In addition, when measuring temperature by using the method based on the fluorescence intensity ratio of thermally coupled energy levels of rare earth ions, due to the low quantum efficiency of the temperature-sensitive material for luminescence, in order to improve the measurement accuracy of fluorescence, it is often necessary to increase the power of the excitation light source. On the one hand, the high-power excitation light will heat the surface of the sample, causing measurement errors; on the other hand, the high-power excitation light source will also ablate the tissue structure of the organism, making it difficult to measure the temperature of biological cells by this method.

[0007] Therefore, for temperature detection based on the thermosensitive characteristics of the luminescence intensity ratio of rare earth fluorescent materials, as a very promising temperature measurement technology, it is urgently necessary to solve the problems of low luminescence efficiency of the material and low temperature sensitivity in the existing technology. Summary of the Invention

[0008] The purpose of the present invention is to overcome the deficiencies of the existing technology and provide a method for temperature detection that can use a low-power excitation light source to excite the material to luminesce and detect the temperature through the characteristic that the intensity ratio of the material's luminescence in different wavelength bands changes with temperature.

[0009] The technical solution of the present invention is as follows: Using Lu 1-x Eu x NbO4 as the temperature-sensitive material (where 0.005 < x < 0.05), placing Lu 1-x Eu x NbO4 in a temperature environment to reach thermal equilibrium, using ultraviolet light with a wavelength of 200 - 300 nm as the excitation light source to irradiate Lu 1-x Eu x NbO4 to excite the material to luminesce, detecting the emission spectrum of the material in the wavelength range of 300 - 750 nm, and then calibrating the temperature by two methods. First, from the detected emission spectrum, respectively obtain the integrated intensity I E of the material's luminescence in the range of 300 - 520 nm, and the integrated intensity I R of the material's luminescence in the two wavelength ranges of 520 - 750 nm, calculate the ratio R of I R and I E , and then compare with the standard curve of R changing with temperature to obtain the magnitude of the temperature to be measured; second, from the detected emission spectrum, respectively obtain the peak intensity of the material in the range of 300 - 520 nm and the luminescence intensity of the material at 613 nm, calculate their ratio r, and then compare with the standard curve of r changing with temperature to obtain the magnitude of the temperature to be measured. For an environment without fluorescence interference, use the characteristic of R changing with temperature to measure temperature; for an environment with fluorescence interference, use the characteristic of r changing with temperature to measure temperature.

[0010] The technical principle of the present invention is:

[0011] Irradiate Lu with ultraviolet light having a wavelength in the range of 200 - 300 nm 1-x Eu x NbO4, which can excite the interband transition of electrons. Part of the electrons that transition to the conduction band are confined around the NbO4 tetrahedron and recombine with the valence band electrons to produce a broadband emission with a wavelength covering 300 - 520 nm. Another part of the electrons are captured by Eu 3+ and transfer energy to the Eu 3+ ions to excite the Eu 3+ ions to emit light. The emission spectrum of the Eu 3+ ions is mainly distributed in the wavelength range of 520 - 750 nm. As the temperature increases, part of the electrons confined around the NbO4 tetrahedron escape under the action of thermal excitation and are then captured by Eu 3+ . Since the Eu 3+ can obtain a part of energy by capturing this part of electrons, compensating for part of the thermal quenching effect. Therefore, as the temperature increases, the broadband emission of the thermosensitive material Lu 1-x Eu x NbO4 in the range of 300 - 520 nm rapidly weakens, while the luminous intensity in the wavelength range of 520 - 750 nm changes slowly or even increases. This results in the intensity ratio R (or r) of the light emission in these two wavelength ranges varying monotonically with temperature. Therefore, the magnitude of the待测温度 (it should be "measured temperature" in English, but since the original text has this placeholder, it remains as "待测温度") can be calibrated through R (or r). Since within the doping amount range of 0.005 < x < 0.05 of Eu 3+ , the material can efficiently emit light within the wavelength range of 300 - 750 nm. Therefore, using Lu 1-x Eu x NbO4 as the temperature-sensitive material, within the range of 0.005 < x < 0.05, precise measurement of temperature can be achieved based on the thermosensitive characteristics of R (or r).

[0012] The beneficial effects and applications of the present invention include:

[0013] The temperature measurement method of the present invention is based on the idea of using electron-assisted energy transfer to excite rare earth ions to emit light in the Lu 1-x Eu x NbO4 fluorescent material. By measuring the intensity ratio of the light emission of the material in the 300 - 520 nm band and the 520 - 750 nm band to determine the temperature, it is a non-contact temperature measurement method. Due to the fast acquisition speed of the fluorescence spectrum, the temperature measurement has the characteristic of fast response. Using this method, the relative sensitivity at 37 °C is as high as 3.25% K -1 ; the relative sensitivity at 100 °C also reaches 1.25% K -1 , which is better than the relative sensitivity of most temperature measurements based on the thermally coupled energy levels of rare earth ions, and it is a new high-sensitivity temperature measurement method.

[0014] Because the ultraviolet light with a wavelength of 200-300nm is used to excite Lu 1-x Eu x NbO4 has a high external quantum efficiency, so accurate fluorescence measurements can be achieved using low-power excitation light to stimulate the material. Using a low-power excitation light source can avoid temperature measurement errors caused by the material absorbing the excitation light and causing the material to heat up.

[0015] In addition, due to Lu 1-x Eu x The external quantum efficiency of NbO4 luminescence decays less with increasing temperature. Even at 175°C, the total quantum efficiency of the material's luminescence can still maintain more than 80% of the room temperature efficiency. Considering that this method has extremely high sensitivity in temperature measurement at 0-100°C, the temperature measurement method of the present invention is very suitable for accurate temperature measurement in the range of 0-100°C.

[0016] In addition, due to the use of ultraviolet light with a wavelength of 200-300nm to excite Lu 1-x Eu x NbO4 has a high external quantum efficiency, and a small amount of Lu 1-x Eu x NbO4 material, even stimulates a Lu 1-x Eu x NbO4 nanocrystals emit light, which can also achieve accurate measurement of fluorescence. Therefore, this method can be used to measure temperature at the submicron or even nanometer scale. Taking into account the high sensitivity of this temperature measurement method in the range of 0-100℃ and the fact that the use of low-power excitation light sources will not damage biological tissues, this temperature measurement method is suitable for measuring the temperature of biological cells. 1-x Eu x After the NbO4 nanoparticles were dispersed by ultrasound, Lu 1-x Eu x NbO4 nanoparticles are adsorbed (or bonded) on the surface of biological cells and irradiated with ultraviolet light with a wavelength of 200-300nm. 1-x Eu x NbO4 excites the material to emit light, and the temperature of the cell surface is calibrated by measuring R (or r). 1-x Eu x NbO4 nanoparticles are injected into biological cells and irradiated with ultraviolet light with a wavelength of 200-300nm. 1-x Eu x NbO4 excites the material to emit light, and the measured R (or r) can be used to calibrate the internal environment temperature of the cell to be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 :Lu0.99 Eu 0.01 XRD pattern of NbO4 powder.

[0018] Figure 2 : Using 248nm ultraviolet light to excite Lu 0.99 Eu 0.01 Luminescence spectrum of NbO4 at room temperature (298K).

[0019] Figure 3 : Using 248nm ultraviolet light to excite Lu 0.99 Eu 0.01 The quantum efficiency test diagram of NbO4 luminescence at room temperature (298K), where EQE is the external quantum efficiency.

[0020] Figure 4 : Using 248nm ultraviolet light to excite Lu 0.95 Eu 0.05 Luminescence spectrum of NbO4 at room temperature (298K).

[0021] Figure 5 :In the temperature range of 298-478K, 248nm ultraviolet light is used to excite Lu 0.99 Eu 0.01 Luminescence spectra of NbO4 at different temperatures.

[0022] Figure 6 :Lu 0.99 Eu 0.01 A graph showing the luminescence integrated intensity ratio R of NbO4 in the two wavelength ranges of 300-520nm and 520-750nm as a function of temperature.

[0023] Figure 7 : Sensitivity curve of temperature measurement based on the temperature-sensitive characteristics of R.

[0024] Figure 8 :Lu 0.99 Eu 0.01 A graph showing the luminescence intensity ratio r of NbO4 at 399nm and 613nm as a function of temperature.

[0025] Figure 9 : Sensitivity curve of temperature measurement based on the temperature-sensitive characteristics of r. DETAILED DESCRIPTION

[0026] Example 1: Lu 0.99 Eu 0.01 NbO4(LNO:0.01Eu 3+ ) powder preparation and luminescence performance test

[0027] Lu2O3, Eu2O3, and Nb2O5 are used as raw materials. First, the raw materials need to be pre-calcined at 800℃ for 2 hours to remove impurities such as moisture adsorbed on the surface of the materials. A certain amount of Lu2O3, Eu2O3, and Nb2O5 are weighed according to stoichiometry, fully ground and mixed, and then reacted at 1250℃ for 12 hours. After naturally cooling to room temperature, ball milling for 4 hours, and then placed in a muffle furnace for reaction at a high temperature of 1300℃ for 12 hours, cooled to room temperature, and after grinding, X-ray diffraction is used to analyze the phase and crystal structure of the material, as shown in FIG. Figure 1 As shown, it is proved that pure phase Lu was prepared 0.99 Eu 0.01 NbO4 phosphor. Lu was measured using a fluorescence spectrometer 0.99 Eu 0.01 The photoluminescence of NbO4 phosphor at room temperature is irradiated by 248nm ultraviolet light. 0.99 Eu 0.01 NbO4 phosphor, stimulates the interband transition of electrons, and measures the emission spectrum of the material in the range of 300-750nm ( Figure 2 ) and the quantum efficiency of light conversion ( Figure 3 ).like Figure 2 As shown, Lu 0.99 Eu 0.01 The emission spectrum of NbO4 includes broadband emission in the wavelength range of 300-520nm due to the matrix and 3+ The linear emission peak of ion 4f electron transition emission is distributed in the wavelength range of 520-750nm. Figure 3 As shown, Lu 0.99 Eu 0.01 The external quantum efficiency (EQE) of NbO4 photoluminescence is as high as 39.2%.

[0028] Example 2: Lu 0.95 Eu 0.05 NbO4(LNO:0.05Eu 3+ ) powder preparation and luminescence performance test

[0029] Lu2O3, Eu2O3, and Nb2O5 are used as raw materials. First, the raw materials need to be pre-calcined at 800°C for 2 hours to remove impurities such as moisture adsorbed on the surface of the materials. A certain amount of Lu2O3, Eu2O3, and Nb2O5 are weighed according to a molar ratio of 0.95:0.05:1. After being fully ground and mixed, they are reacted at 1250°C for 12 hours. After naturally cooling to room temperature, they are ball-milled for 4 hours, and then placed in a muffle furnace for reaction at a high temperature of 1300°C for 12 hours. After cooling to room temperature, X-ray diffraction analysis is used after grinding to prove that pure phase Lu is prepared. 0.95 Eu 0.05 NbO4 phosphor. Lu was measured using a fluorescence spectrometer0.95 Eu 0.05 The photoluminescence of NbO4 phosphor at room temperature is irradiated by 248nm ultraviolet light. 0.95 Eu 0.05 NbO4 phosphor, stimulates the interband transition of electrons, and measures the emission spectrum of the material in the range of 300-750nm, such as Figure 4 As shown, it was observed that 248 nm ultraviolet light excited Lu 0.95 Eu 0.05 NbO4 can achieve broadband emission in the wavelength range of 300-520nm, and due to Eu 3+ The linear emission peak of ion 4f electron transition emission is distributed in the wavelength range of 520-750nm.

[0030] Example 3: Measuring temperature based on the size of R

[0031] Lu 0.99 Eu 0.01 NbO4 phosphor is used as a temperature sensitive material and placed in an environment with different temperatures ranging from 298K to 478K. 248nm ultraviolet light is selected to excite Lu 0.99 Eu 0.01 The NbO4 phosphor emits light and the photoluminescence spectrum of the material is measured at different temperatures, such as Figure 5 As shown. The integrated intensity I of the luminescence of the material in the range of 300-520nm is obtained respectively. E , and the luminous integral intensity I of the material in the two wavelength ranges of 520-750nm R , calculate I R and I E The ratio R of the temperature is plotted as Figure 6 As shown in the figure, it can be seen that R increases monotonically with increasing temperature. By measuring the R value at a certain temperature, Figure 6 The precise value of the temperature can be obtained by looking at the R-T curve. Figure 7 The absolute sensitivity (S a ) can be as high as 0.049K -1 , relative sensitivity (S r ) up to 3.25% K -1 ; Absolute sensitivity at 100℃ reaches 0.063K -1 , the relative sensitivity also reached 1.25% K -1 .

[0032] Example 4: Measuring temperature based on the size of r

[0033] Lu 0.99 Eu 0.01NbO4 phosphor is used as a temperature sensitive material and placed in an environment with different temperatures ranging from 298K to 478K. 248nm ultraviolet light is selected to excite Lu 0.99 Eu 0.01 The NbO4 phosphor emits light and the photoluminescence spectrum of the material is measured at different temperatures, such as Figure 5 As shown. The luminous intensity I of the material at 399nm is obtained respectively 399 , and the luminous intensity of the material at 613nm I 399 , calculate the ratio r of the two, and draw the temperature change curve of r as shown in Figure 8 As shown in the figure, it can be seen that r increases monotonically with increasing temperature. By measuring the r value at a certain temperature, Figure 8 The exact value of the temperature can be obtained by looking at the r-T curve. Figure 9 The absolute and relative sensitivities of measuring temperature using this method are shown.

Claims

1. A Lu-based 1-x Eu x The method for measuring temperature based on the fluorescent thermal sensitivity of NbO4 is characterized by: Lu 1-x Eu x NbO4 is a temperature sensitive material, of which 0.005 <x<0.05; The Lu 1-x Eu x NbO4 is placed in a temperature environment to reach thermal equilibrium, and ultraviolet light with a wavelength of 200-300nm is used as an excitation light source to irradiate the Lu 1-x Eu x NbO4, stimulate the material to emit light, detect the emission spectrum of the material in the wavelength range of 300-750nm, and then calibrate the temperature using the following two methods: (1) From the detected emission spectrum, the integrated intensity I of the luminescence of the material in the range of 300-520nm is obtained. E And the luminous integral intensity I of the material in the two wavelength ranges of 520-750nm R , calculate I R and I E The ratio R is then compared with the standard curve of R changing with temperature to obtain the size of the temperature to be measured; (2) From the detected emission spectrum, the peak intensity of the material in the range of 300-520nm and the luminescence intensity of the material at 613nm are obtained respectively, and their ratio r is calculated. Then, the value of the temperature to be measured is obtained by comparing it with the standard curve of r changing with temperature.

2. The temperature measurement method according to claim 1, wherein: The Lu 1-x Eu x NbO4 is Lu 0.99 Eu 0.01 NbO4.

3. The temperature measurement method according to claim 1, wherein: For an environment without fluorescence interference, the standard curve of R changing with temperature is used to obtain the size of the temperature to be measured.

4. The temperature measurement method according to claim 1, wherein: In an environment with fluorescence interference, a standard curve comparing r with temperature is used to obtain the magnitude of the temperature to be measured.

5. A Lu-based method according to claim 1 or 2 1-x Eu x The application of the temperature measurement method based on the fluorescence thermal sensitivity characteristics of NbO4 in the temperature measurement of biological cells.

6. The use according to claim 5, characterized in that: Lu 1-x Eu x After the NbO4 nanoparticles were dispersed by ultrasound, Lu 1-x Eu x NbO4 nanoparticles are adsorbed or bonded to the surface of biological cells, and ultraviolet light with a wavelength of 200-300nm is used to irradiate Lu 1-x Eu x NbO4 excites the material to emit light, and the temperature of the cell surface is calibrated by measuring R or r.

7. The use according to claim 5, characterized in that: A small amount of Lu 1-x Eu x NbO4 nanoparticles are injected into biological cells and irradiated with ultraviolet light with a wavelength of 200-300nm. 1-x Eu x NbO4 excites the material to emit light, and the internal environment temperature of the cell to be tested is calibrated by measuring R or r.

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