A downconversion fluorescence thermometry method based on bilinear mode

Abstract

This invention discloses a downconversion fluorescence thermometry method based on bilinear mode, implemented using a hardware system. The hardware system includes a 280nm light-emitting diode, two convex lenses, and a Tb... 3+ :Cs2Na 0.9 Ag 0.1 The system comprises InCl6 temperature-sensing material, a grating spectrometer, an oscilloscope, a signal generator, a computer, and a thermostat. The specific implementation steps are: signal excitation and acquisition; temperature calibration; actual temperature measurement; and high measurement accuracy: VPR mode linear correlation coefficient R² ≥ 0.998, FL mode linear correlation coefficient R² ≥ 0.992, avoiding measurement errors introduced by the exponential bias or correction term of traditional FIR technology, thus fundamentally improving temperature measurement accuracy.

Description

Technical Field

[0001] This invention relates to the field of rare earth fluorescence temperature measurement technology, specifically to a downconversion fluorescence temperature measurement method based on a bilinear mode of valley-to-peak ratio (VPR) and fluorescence lifetime (FL), which is suitable for non-contact temperature measurement scenarios with high requirements for temperature measurement accuracy, anti-interference and temperature range coverage, such as microelectronics, biomedicine, and semiconductor detection. Background Technology

[0002] Non-contact optical temperature measurement technology has become an indispensable temperature measurement method in many key fields such as microelectronics, biomedicine, and semiconductor testing due to its advantages such as non-invasiveness, fast response, high spatial resolution, and resistance to electromagnetic interference. Among them, fluorescent thermometers based on rare earth luminescent materials are a popular research branch in this field.

[0003] The core of rare-earth fluorescence thermometry relies on temperature-sensitive optical parameters such as fluorescence intensity, peak position, full width at half maximum (FWHM), fluorescence intensity ratio (FIR), and fluorescence lifetime (FL). Among these, the fluorescence intensity ratio (FIR) technique is the most widely used due to its strong resistance to light source fluctuations and ease of operation. FIR technology is mainly based on the thermally coupled energy level (TCLs) model of rare-earth luminescent materials. Its core principle is to select a pair of thermally coupled energy levels of rare-earth ions (typically with an energy level spacing of 200 cm⁻¹). -1 -2000cm -1 The temperature calibration and actual measurement are completed by using the fluorescence intensity ratio (FIR) of the adjacent energy levels of the spontaneous emission of the adjacent energy levels as a function of temperature.

[0004] Since the particle number distribution of thermally coupled energy levels follows a Boltzmann distribution, the fluorescence ratio (FIR) exhibits an exponential form of the Boltzmann distribution, expressed as FIR = Aexp(-ΔE / kT) (where A is a constant, ΔE is the energy level difference, k is the Boltzmann constant, and T is the absolute temperature). The core indicator for evaluating the temperature measurement performance of FIR technology is the temperature sensitivity Sr, expressed as Sr = ΔE / kT². This formula shows that when the thermally coupled energy level pairs of rare-earth ions are fixed and ΔE is constant, Sr decays rapidly with increasing temperature according to a 1 / T² law, leading to a significant decrease in temperature sensitivity in the high-temperature region.

[0005] To improve the temperature sensing sensitivity of Sr, existing techniques attempt to increase the energy level difference ΔE. However, studies have shown that increasing ΔE leads to a significant decrease in the proportion of particles in the upper energy level, resulting in extremely weak fluorescence intensity. When ΔE increases to 2000 cm⁻¹, the fluorescence intensity becomes even weaker. -1 When the above conditions are met, the signal-to-noise ratio (SNR) of the acquired fluorescence signal will decrease by more than an order of magnitude, directly leading to increased measurement error and a significant decrease in the stability of the temperature measurement system. If ΔE is reduced to 200cm... -1The FIR formula needs to introduce a correction term B that varies with temperature (i.e., FIR = Aexp(-ΔE / kT) + B). The temperature dependence of the correction term will further increase the measurement uncertainty, leading to a decrease in the accuracy of temperature measurement.

[0006] In summary, existing FIR technology suffers from core defects such as temperature-dependent attenuation of temperature measurement sensitivity, high measurement uncertainty, and difficulty in self-calibration. It is difficult to meet the requirements of high-precision, wide-temperature-range non-contact temperature measurement in complex environments. Therefore, it is urgent to develop a new fluorescence temperature measurement mode with linear response, wide temperature range complementarity, strong anti-interference ability, and self-calibration function to solve the above technical problems. Summary of the Invention

[0007] To address the technical problems of existing FIR technologies, such as rapid decay of temperature measurement sensitivity with temperature, low signal-to-noise ratio, large measurement error, and difficulty in self-calibration, this invention provides a downconversion fluorescence thermometry method based on a bilinear mode of peak-to-valley ratio (VPR) and fluorescence lifetime (FL). By constructing a bilinear correlation model, a linear response over a wide temperature range is achieved. Combined with a self-calibration mechanism of dual-mode cross-validation, the anti-interference capability and measurement stability of temperature measurement are improved. At the same time, lead-free perovskite thermosensitive material is used to achieve environmental friendliness and adaptability to complex environments.

[0008] This invention provides a downconversion fluorescence thermometry method based on bilinear mode: This is implemented using a hardware system, which includes a 280nm light-emitting diode, two convex lenses, and Tb. 3+ :Cs2Na 0.9 Ag 0.1 The equipment includes InCl6 temperature-sensing material, a grating spectrometer, an oscilloscope, a signal generator, a computer, and a thermostat; the specific implementation steps are as follows: (1) Signal excitation and acquisition: The ultraviolet light emitted by the 280nm light-emitting diode is focused by the first convex lens and then irradiates the surface of the temperature-sensitive material vertically. The material is excited to emit down-convert fluorescence. The fluorescence is focused by the second convex lens and then enters the slit of the grating spectrometer. The signal generator pulses the 280nm light-emitting diode to make the fluorescence pulsed or continuously emitted. (2) Temperature calibration: Tb 3+ :Cs2Na 0.9 Ag 0.1 The InCl6 temperature-sensing material is placed in a thermostat, with the temperature range set to 80K-300K, and held for 5 minutes every 10K until the temperature stabilizes. The detector of the grating spectrometer converts the optical signal into an electrical signal, which is transmitted to the oscilloscope and computer through a multi-port interface. The computer calculates the VPR and FL values, establishes the VPR-temperature curve and FL-temperature curve through linear fitting, and completes the calibration. (3) Actual temperature measurement: Place the temperature sensing material in the temperature field to be measured, repeat step (1), substitute the collected time-resolved signal and valley-to-peak ratio VPR into the calibration curve to calculate and output the temperature value to be measured, and obtain the final result after eliminating outliers through dual-mode cross-validation.

[0009] Preferably, the temperature-sensing material is Tb. 3+ Doped Cs2Na 0.9 Ag 0.1 InCl6 lead-free perovskite material was used with downconversion excitation and 280nm ultraviolet light as the excitation source.

[0010] Preferably, the fluorescence detected by the grating spectrometer originates from Tb. 3+ Ionic 5 D4→ 7 The F5 energy level radiative transition produces two split fluorescence peaks, which overlap due to their similar wavelengths to form a valley at 545 nm.

[0011] Preferably, the bilinear mode includes a valley-to-peak ratio mode and a fluorescence lifetime mode; in the VPR mode, the fluorescence intensity ratio of the 545nm valley to the 543nm peak increases linearly with increasing temperature, with a linear correlation coefficient R² ≥ 0.998; in the FL mode, the lifetime of the 548nm fluorescence peak decreases linearly with increasing temperature, with a linear correlation coefficient R² ≥ 0.992.

[0012] Preferably, the relative sensitivity of the VPR mode decreases slowly with increasing temperature; the relative sensitivity of the FL mode increases linearly with increasing temperature, and the dual-mode sensitivities form a temperature-dependent complementary relationship.

[0013] Beneficial effects: Excellent linearity and high measurement accuracy: The linear correlation coefficient R² of VPR mode is ≥0.998 and the linear correlation coefficient of FL mode is ≥0.992, which avoids the measurement error introduced by the exponential deviation or correction term of traditional FIR technology, and improves the accuracy of temperature measurement in principle. Wide temperature range complementarity and strong adaptability: Utilizing the complementary temperature dependence of the sensitivity of VPR and FL modes, a wide temperature measurement coverage from 80K to 300K low temperature to room temperature is achieved, along with Tb-based... 3+ :Cs2Na 0.9 Ag 0.1 Compared with the FIR technology of InCl6, the present invention improves the temperature measurement sensitivity at 300K by 4 times, and a single temperature sensing material can be adapted to multiple temperature range scenarios without the need to change materials, thus simplifying the operation process. Strong anti-interference capability and high measurement stability: Dual-mode synchronous signal acquisition and cross-validation to eliminate outliers significantly improve the system's resistance to interference from ambient light and light source fluctuations compared to single-mode systems. Verified dual-mode cross-validation has reduced the temperature measurement error to below ±1K, comparable to Tb-based systems. 3+ :Cs2Na 0.9 Ag 0.1 Compared to the FIR technology using InCl6, this invention reduces the measurement error by more than 20% at 300K. In practical applications, the error compared to the standard thermometer measurement is ≤ ±0.5K.

[0014] Environmentally friendly and adaptable to complex environments: the temperature-sensing material is Tb 3+ :Cs2Na 0.9 Ag 0.1 InCl6 is a lead-free perovskite with no heavy metal contamination and excellent chemical stability, making it suitable for complex industrial environments such as microelectronics and semiconductor testing, as well as special environments such as biomedicine. Self-calibration function, easy to operate: VPR and FL dual-mode data can be mutually verified to achieve self-calibration, without the need for additional calibration equipment, which simplifies the operation process of the temperature measurement system and reduces the cost of use; Non-contact temperature measurement, non-invasive: Based on the principle of optical fluorescence thermometry, non-contact temperature measurement is achieved, avoiding the interference of contact temperature measurement on the temperature field of the object being measured (such as microelectronics and semiconductor devices), while meeting the non-invasive temperature measurement requirements of fields such as biomedicine. Attached Figure Description

[0015] All accompanying drawings are high-resolution electronic images with a resolution of ≥300dpi, and will be referenced in the corresponding technical solution section of the instruction manual. Figure 1 :Tb 3+ :Cs2Na 0.9 Ag 0.1 Flowchart of InCl6 thermosensitive material preparation; the attached diagram clearly shows the core steps of thermosensitive material preparation, including raw material ratio, ultrasonication, shaking, centrifugation, washing, drying and grinding, to guide the specific preparation of thermosensitive materials; Figure 2 :Tb 3+ :Cs2Na 0.9 Ag 0.1 TEM image of InCl6 nanoparticles; the attached figure shows a (022) interplanar spacing of 0.52 nm and a scale bar of 2 nm, confirming that the prepared temperature-sensing material is a nanoparticle with a clear crystal structure and high material purity. Figure 3 Schematic diagram of temperature measurement system: In the attached diagram: 1-Temperature sensing material Tb 3+ :Cs2Na 0.9 Ag 0.1InCl6, 2-lens, 3-spectrometer, 4-photomultiplier tube, 5-oscilloscope, 6-lens, 7-280nm light-emitting diode, 8-signal generator, 9-computer; Figure 4 : Linear temperature dependence of VPR and FL; the horizontal axis is temperature / K, the left vertical axis is VPR value, and the right vertical axis is fluorescence lifetime / ms. The linear fitting equations for VPR-temperature and FL-temperature and the corresponding R are marked. 2 The value visually demonstrates the linear response characteristics of the bilinear mode; Figure 5 Measurement error distribution diagram; the horizontal axis of the attached figure is the number of measurements, and the vertical axis is temperature / K. It marks the temperature measurement error range of VPR and FL single modes and the temperature measurement error after dual-mode cross-validation, intuitively demonstrating the role of dual-mode cross-validation in reducing measurement error. Figure 6 Temperature sensitivity graph; the horizontal axis represents temperature in K, and the left vertical axis represents the relative sensitivity of VPR mode in %K. -1 The right vertical axis represents the relative sensitivity of FL mode / %K -1 This visually demonstrates the complementary sensitivity temperature dependence of VPR and FL modes. Detailed Implementation

[0016] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection.

[0017] It should be noted that the temperature measurement method of the present invention is implemented based on a dedicated hardware system, the components and core functions of which are shown in Table 1 below: Table 1. Temperature Measurement Hardware System Components and Functions The core technical solution of this invention includes four core steps: preparation of temperature-sensing materials, system construction, temperature calibration, and actual temperature measurement. The specific implementation details of each step are as follows: Preparation of temperature-sensing materials: Preparation of Tb 3+ Tb³⁺:Cs₂Na with a doping concentration of 15-30 mol% 0.9 Ag 0.1 InCl6 lead-free perovskite material ensures the material's fluorescence temperature sensitivity and stability; System setup: The hardware setup is completed in the optical path sequence of excitation source → first convex lens → temperature sensing material → second convex lens → grating spectrometer; the signal generator is connected to the 280nm light-emitting diode to realize the modulation control of the excitation source; the grating spectrometer is connected to the oscilloscope and computer through a multi-port interface to realize the synchronous acquisition and transmission of fluorescence spectral signals and time-resolved signals. Temperature calibration: Tb 3+ :Cs2Na 0.9 Ag 0.1 The InCl6 temperature-sensing material was placed in a thermostat, with the temperature adjustment range set to 80K-300K. Calibration nodes were established at 10K intervals, with each node held for 5 minutes until the temperature stabilized. Fluorescence intensity spectral signals at each temperature node were acquired using a grating spectrometer, and time-resolved signals were acquired using an oscilloscope. The acquired signals were processed by a computer to calculate the peak-to-valley ratio (VPR) (the fluorescence intensity ratio of the 545nm valley to the 543nm peak) and fluorescence lifetime (FL) (the fluorescence lifetime of the 548nm fluorescence peak). Linear fitting was performed on the VPR and FL values ​​against their corresponding temperature values ​​to establish VPR-temperature linear curves and FL-temperature linear curves, thus completing the temperature calibration of the entire temperature measurement system. Actual temperature measurement: Tb 3+ :Cs2Na 0.9 Ag 0.1 The InCl6 temperature-sensing material is placed in the temperature field to be measured, and the above signal excitation and acquisition steps are repeated. The computer calculates the VPR and FL values ​​under this temperature field in real time. The two parameter values ​​are substituted into the corresponding calibration linear curves to obtain two independent temperature measurement results. Outliers are eliminated through dual-mode cross-validation. Temperature data in VPR and FL modes are acquired simultaneously for the same temperature measurement object. When the temperature deviation between the two modes is ≤ ±2K, the average value of the two modes is taken as the valid result. When the deviation is > ±2K, the abnormal data set is eliminated and the signal is reacquired. After cross-validation, the final measured temperature value is output.

[0018] The bilinear mode of this invention is based on Tb 3+ Ionic 5 D4→ 7 The F5 energy level radiative transition is achieved, which produces two split fluorescence peaks at 543 nm and 548 nm. The two peaks overlap due to their similar wavelengths, forming a fluorescence valley at 545 nm. In the valley-to-peak ratio (VPR) mode, the intensity ratio of the 545 nm valley to the 543 nm peak increases linearly with increasing temperature, with a linear correlation coefficient R² ≥ 0.998. In the fluorescence lifetime (FL) mode, the lifetime of the 548 nm fluorescence peak decreases linearly with increasing temperature, with a linear correlation coefficient R² ≥ 0.992. Both modes break through the exponential relationship limitations of traditional FIR technology.

[0019] The relative sensitivities of the VPR and FL modes exhibit temperature-dependent complementary characteristics: the relative sensitivity of the VPR mode decreases slowly with increasing temperature, reaching 0.7%K⁻¹ at 80K and 0.3%K⁻¹ at 300K; the relative sensitivity of the FL mode increases linearly with increasing temperature, reaching 0.13%K⁻¹ at 173K and 0.16%K⁻¹ at 293K. -1 The dual-mode complementary sensitivity characteristics enable comprehensive temperature measurement coverage across a wide temperature range of 80K-300K without the need to replace the sensing material.

[0020] To further illustrate the technical solution and implementation effects of the present invention, the preparation of the temperature-sensing material, system construction and parameter setting, temperature calibration experiment, and temperature measurement verification experiment of the present invention are described in detail with specific experimental parameters. This embodiment is only used to explain the present invention and is not intended to limit the scope of protection of the present invention.

[0021] Preparation of temperature-sensing materials Raw material weighing: Weigh 1 mmol of CsCl, 0.9 mmol of NaCl, 0.1 mmol of AgCl, (0.5-0.5x) mmol of In₂O₃, and x mmol of TbCl₃ (Tb 3+ Doping concentration = x / [2(0.5-0.5x)+x]×100%, x=0.15-0.3, corresponding to Tb 3+ The doping concentration (15-30 mol%) was loaded into a flask; Mixing treatment: Sonicate the powdered raw materials in the flask for 10 minutes to ensure uniform mixing; add 3 mL of 37 wt% HCl solution to the flask and shake for 1 minute to allow the raw materials to react fully. Centrifugation and washing: Transfer the reaction mixture into a centrifuge tube and centrifuge at 4000 r / min for 10 minutes; discard the supernatant after centrifugation, and wash the precipitate twice with anhydrous ethanol to remove impurities; Drying and grinding: The rinsed precipitate was dried in a 60℃ oven for 12 hours and then thoroughly ground to obtain Tb. 3+ :Cs2Na 0.9 Ag 0.1 The InCl6 nanoparticle samples were sealed, dried, and stored to ensure stable material properties.

[0022] System setup and parameter settings: The temperature measurement system is constructed according to the optical path sequence of the technical solution of this invention, and the following specific operating parameters are set for each core component to ensure the accuracy of signal acquisition and processing: Excitation source: 280nm light-emitting diode, using pulse output mode, pulse frequency 100Hz, duty cycle 20%; Optical components: Two convex lenses are placed coaxially. The excitation light is focused onto the surface of the temperature-sensitive material after passing through the first convex lens, and the diameter of the focused light spot is 1mm. Acquisition equipment: The grating spectrometer was set to a resolution of 0.1 nm to ensure accurate acquisition of fluorescence spectra; the oscilloscope sampling frequency was set to 1 GHz to ensure the accuracy of time-resolved signal acquisition. Connection method: The detector of the grating spectrometer is connected to the oscilloscope and the computer data acquisition card through a multi-port interface to realize synchronous and lossless transmission of fluorescence spectral signals and time-resolved signals.

[0023] Temperature calibration and temperature measurement experiment Temperature calibration experiment: The temperature adjustment range of the thermostat was set from 80K to 300K, with each 10K serving as a calibration node. Each node was held for 5 minutes to ensure temperature stability. Fluorescence spectra and fluorescence lifetime signals were collected at each temperature node, and the VPR and FL values ​​for each node were calculated by computer. Linear fitting was performed on the data to obtain the calibration curve for this embodiment. VPR-Temperature Curve: VPR = 0.1125 + 0.0011T (linear correlation coefficient R² = 0.998). FL-Temperature curve: FL = 8.50705 - 0.0092T (linear correlation coefficient R² = 0.992); Measurement error verification experiment: Multiple random signal acquisition and temperature measurement experiments were conducted in a constant temperature environment of 213K. The results showed that the maximum measurement error of VPR and FL single-mode temperature measurement could reach ±3K. After eliminating outliers through dual-mode cross-validation, the temperature measurement error was reduced to less than ±1K, which significantly improved the measurement accuracy. Sensitivity test experiment: Full-range sensitivity test was conducted in the temperature range of 80K-300K. The results showed that the relative sensitivity of VPR mode at 80K was 0.7%K. -1 At 300K, it is 0.3%K. -1 It exhibits a slow decay trend; the relative sensitivity at 173K in FL mode is 0.13%K. -1 At 293K, it is 0.16%K. -1 The temperature-dependent complementary characteristics of the two modes are perfectly complementary and show a linear increasing trend. Actual temperature measurement experiment: Tb 3+ :Cs2Na 0.9 Ag 0.1 The InCl6 temperature-sensing material and the semiconductor device under test are placed in the same environment. The temperature measurement system is activated to collect fluorescence signals. The computer calculates the VPR and FL values ​​in real time and substitutes them into the calibration curve. After dual-mode cross-validation, the final temperature is output. The error between this result and the measurement value of the standard thermometer is ≤ ±0.5K, which meets the requirements of high-precision temperature measurement.

[0024] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A downconversion fluorescence thermometry method based on bilinear mode, characterized in that, This is implemented using a hardware system, which includes a 280nm light-emitting diode, two convex lenses, and Tb. 3+ :Cs2Na 0.9 Ag 0.1 The equipment includes InCl6 temperature-sensing material, a grating spectrometer, an oscilloscope, a signal generator, a computer, and a thermostat; the specific implementation steps are as follows: (1) Signal excitation and acquisition: The ultraviolet light emitted by the 280nm light-emitting diode is focused by the first convex lens and then irradiates the surface of the temperature-sensitive material vertically. The material is excited to emit down-convert fluorescence. The fluorescence is focused by the second convex lens and then enters the slit of the grating spectrometer. The signal generator pulses the 280nm light-emitting diode to make the fluorescence pulsed or continuously emitted. (2) Temperature calibration: Tb with a doping concentration of 20-25 mol% 3+ :Cs2Na 0.9 Ag 0.1 The InCl6 temperature-sensing material is placed in a thermostat, with the temperature range set to 80K-300K, and held for 5 minutes every 10K until the temperature stabilizes. The detector of the grating spectrometer converts the optical signal into an electrical signal, which is transmitted to the oscilloscope and computer through a multi-port interface. The computer calculates the VPR and FL values, establishes the VPR-temperature curve and FL-temperature curve through linear fitting, and completes the calibration. (3) Actual temperature measurement: Place the temperature sensing material in the temperature field to be measured, repeat step (1), substitute the collected time-resolved signal and valley-to-peak ratio VPR into the calibration curve to calculate and output the temperature value to be measured. When the deviation between VPR and the temperature value calculated by FL mode is ≤ ±2K, take the average of the two as the final result; when the deviation is > ±2K, discard the data and re-acquire the signal. After dual-mode cross-validation, the final result is obtained.

2. The downconversion fluorescence thermometry method based on bilinear mode according to claim 1, characterized in that, The temperature-sensing material is Tb. 3+ Doped Cs2Na 0.9 Ag 0.1 InCl6 lead-free perovskite material was used with downconversion excitation and 280nm ultraviolet light as the excitation source.

3. The downconversion fluorescence thermometry method based on bilinear mode according to claim 1, characterized in that, The fluorescence detected by the grating spectrometer originates from Tb. 3+ Ionic 5 D4→ 7 The F5 energy level radiative transition produces two split fluorescence peaks, which overlap due to their similar wavelengths to form a valley at 545 nm.

4. The downconversion fluorescence thermometry method based on bilinear mode according to claim 3, characterized in that, The bilinear modes include a valley-to-peak ratio mode and a fluorescence lifetime mode. In the VPR mode, the fluorescence intensity ratio of the 545nm valley to the 543nm peak increases linearly with increasing temperature, with a linear correlation coefficient R² ≥ 0.

998. In the FL mode, the lifetime of the 548nm fluorescence peak decreases linearly with increasing temperature, with a linear correlation coefficient R² ≥ 0.

992.

5. The downconversion fluorescence thermometry method based on bilinear mode according to claim 4, characterized in that, The relative sensitivity of the VPR mode decreases slowly with increasing temperature; the relative sensitivity of the FL mode increases linearly with increasing temperature. The dual-mode sensitivity forms a temperature-dependent complementarity, and the dual-mode complementarity achieves a temperature measurement sensitivity of ≥0.13%K⁻¹ in the 80K-300K temperature range with no sensitivity blank area.

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