A fluorescence lifetime temperature measurement method using dual-path signals

Abstract

The present invention discloses a fluorescence lifetime temperature measurement method using dual-path signals. The method uses a temperature probe prepared from a rare earth ion dual-doped nanofluorescent material to detect temperature. The excited state energy of doped ion 1 in the nanofluorescent material is higher than that of doped ion 2. The fluorescence lifetime of doped ion 1 shortens as temperature increases, while the fluorescence lifetime of doped ion 2 increases as temperature increases. A fitting curve of the fluorescence lifetime ratio of doped ion 1 to doped ion 2 versus temperature is used as a calibration curve for the temperature probe. The temperature measurement operating range of the probe is determined based on a theoretical temperature measurement sensitivity curve. The fitting formula corresponding to the calibration curve is used to reversely infer the detected temperature based on the measured fluorescence lifetime ratio. The present invention does not rely on the penetration depth of the probe into the object to be measured and can be used for temperature measurement on the surface of the material. It is also suitable for temperature monitoring in complex environments within the material. The rare earth ion doping system can be flexibly designed to select the fluorescence band corresponding to the acquisition signal. No hardware is required, and the method is low-cost and easy to operate.

Description

Technical Field

[0001] The invention belongs to the field of optical sensing and relates to a fluorescence lifetime temperature measurement method using dual-path signals. Background Art

[0002] Temperature is a physical quantity that characterizes the degree of hotness or coldness of an object. It is closely related to almost all physical processes and therefore plays a very important role in scientific research, industrial production, medicine and other fields.

[0003] Traditional temperature measurement devices, such as thermocouples and thermistors, use electrical signals to characterize temperature by contacting the object being measured. With the rapid development of fields such as microelectronics, photonics, and nanomedicine, there is a strong demand for ultra-high spatial resolution temperature measurement at the micro- and nanoscale. However, the traditional contact temperature measurement methods mentioned above are no longer applicable in these cutting-edge applications. Furthermore, contact temperature measurement methods are also powerless in specialized applications such as in-vivo temperature monitoring and temperature sensing of non-fixed components. Although infrared thermometers, another commonly used method, use a non-contact solution, they are limited by the differences in emissivity of different materials and are difficult to obtain, resulting in low accuracy.

[0004] Multiple dimensions of rare earth fluorescence signals can be used for temperature sensing. For example, the fluorescence intensity of each band usually decreases with increasing temperature, the ratio of the fluorescence intensity of two bands changes with temperature, and the fluorescence lifetime of the same radiation band will also vary at different ambient temperatures. These changing patterns can all be used for temperature sensing. Among them, temperature sensing technology based on fluorescence lifetime has unique advantages, mainly because: on the one hand, fluorescence lifetime can reduce the impact of fluctuations in the external environment and signal intensity on the measurement results; on the other hand, fluorescence lifetime is independent of the absorption of the material to be measured or the intermediate isolation material, and is therefore not affected by the penetration depth of the probe. In summary, using rare earth-doped nanomaterials as probes for lifetime temperature measurement further integrates the ultra-high spatial resolution of nanomaterials on the basis of the advantages of the original fluorescence lifetime temperature measurement technology itself, which can meet the needs of many cutting-edge temperature measurement fields at the micro-nano scale.

[0005] The principle of rare earth fluorescence temperature measurement is briefly described as follows: During the rare earth ion photoluminescence process, when the excitation light source is turned off, the spontaneous radiation of the luminescence center begins to decay, and the expression of its fluorescence intensity changing with time is:

[0006]

[0007] Where I and I0 are the fluorescence intensities at time t and the initial time, respectively. τ is the fluorescence lifetime, which is determined by the rare earth ion's spontaneous emission and nonradiative processes (primarily multi-phonon nonradiative relaxation, but also including nonradiative depopulation processes such as energy transfer). The greater the sum of these two factors, the shorter the lifetime. The probability of spontaneous emission from rare earth ions is largely unaffected by temperature, so lifetime thermometry essentially exploits the fact that nonradiative relaxation processes become more intense with increasing temperature.

[0008] However, to obtain a strong fluorescence signal for easy reading and subsequent processing, energy levels with weak non-radiative relaxation are typically selected for fluorescence lifetime sensing. This results in a less pronounced change in rare earth fluorescence lifetime with temperature. Consequently, the main bottleneck of current fluorescence lifetime thermometry technology is its low sensitivity. To overcome the limitations of current fluorescence lifetime thermometry technology, it is urgently necessary to develop new temperature-responsive nanomaterials, improve temperature measurement methods, and construct nanoscale temperature sensors with high sensing sensitivity. Summary of the Invention

[0009] In view of the above-mentioned prior art, the technical problem to be solved by the present invention is to provide a simple and easy fluorescence lifetime temperature measurement method using dual-channel fluorescence lifetime signals to improve the sensitivity of lifetime temperature measurement technology.

[0010] To solve the above technical problems, the present invention provides a fluorescence lifetime temperature measurement method using dual-channel signals, and uses a temperature measuring probe prepared from a nano-fluorescent material doped with rare earth ions to detect temperature. In the nano-fluorescent material, the excited state energy of doped ion 1 is higher than that of doped ion 2, the fluorescence lifetime of doped ion 1 shortens with increasing temperature, and the fluorescence lifetime of doped ion 2 extends with increasing temperature. A fitting curve of the fluorescence lifetime ratio of doped ion 1 and doped ion 2 versus temperature is used as a calibration curve of the temperature measuring probe, the temperature measurement working range of the probe is determined according to the theoretical temperature measurement sensitivity curve, and the detection temperature is obtained by inverse deduction based on the measured fluorescence lifetime ratio using the fitting formula corresponding to the calibration curve.

[0011] Furthermore, the method for obtaining a fitting curve of the fluorescence lifetime ratio of the dopant ion 1 and the dopant ion 2 as a function of temperature includes:

[0012] Step 1: placing the temperature measuring probe in an environment with an initial temperature of t0;

[0013] Step 2: Use a signal generator to modulate the excitation wavelength of doped ion 1 and the semiconductor laser outputs a square wave laser to irradiate the temperature measuring probe;

[0014] Step 3: Collect the decay curves of the fluorescence emission wavelengths of dopant ion 1 and dopant ion 2 respectively, and fit them to obtain the fluorescence lifetime curves of dopant ion 1 and dopant ion 2;

[0015] Step 4: Change the ambient temperature, respectively at temperatures t1, t2, ..., tn Repeat step 3 to get t1, t2, ..., t n Fluorescence lifetime curves of dopant ion 1 and dopant ion 2 at different temperatures;

[0016] Step 5: Obtain the fluorescence lifetime curves of dopant 1 and dopant 2 at t0, t1, ..., t n The fluorescence lifetime at the temperature is calculated, and then a data graph of the fluorescence lifetime ratio of the dopant ion 1 and the dopant ion 2 as a function of temperature is plotted. Then, a fitting curve of the fluorescence lifetime ratio of the dopant ion 1 and the dopant ion 2 as a function of temperature is obtained by polynomial fitting.

[0017] Further, according to The fluorescence lifetime curves of dopant ion 1 and dopant ion 2 are fitted, where I and I0 are the fluorescence intensities at time t and the initial time, respectively, and τ is the fluorescence lifetime.

[0018] Furthermore, the theoretical temperature measurement sensitivity curve is based on Plot, where τ1 is the fluorescence lifetime of dopant ion 1, τ2 is the fluorescence lifetime of dopant ion 2, and T represents the temperature.

[0019] Furthermore, the temperature probe is prepared by co-doping NaYF4 nanocrystals with Nd and Yb ions prepared by thermal decomposition or hydrothermal method, and the temperature probe is in the form of powder, block, dispersion or film.

[0020] Beneficial effects of the present invention:

[0021] The traditional fluorescence lifetime temperature measurement scheme is realized by utilizing the law that the non-radiative relaxation process becomes more intense as the temperature rises. In order to obtain a stronger fluorescence signal for easy reading and subsequent processing, energy levels with weaker non-radiative relaxation are usually selected for fluorescence lifetime sensing, resulting in the rare earth fluorescence lifetime not changing significantly with temperature. Therefore, the main bottleneck of the current fluorescence lifetime temperature measurement technology is low sensitivity. The present invention is an improved technology for temperature sensing based on rare earth fluorescence lifetime, involving the use of dual-path fluorescence lifetime signals to improve the temperature measurement sensitivity of rare earth ion fluorescence lifetime, specifically by regulating the rare earth ion luminescence path, realizing the shortening and extension of the dual-path fluorescence lifetime respectively with increasing temperature, and using the law that the ratio of the dual-path fluorescence lifetime changes with temperature for temperature sensing, thereby achieving improved temperature measurement sensitivity. Compared with the prior art, the present invention has the following characteristics:

[0022] 1. This solution does not depend on the penetration depth of the probe into the object to be measured. It can be used not only for surface temperature measurement of materials, but also for temperature monitoring in complex environments inside materials.

[0023] 2. The rare earth ion doping system can be flexibly designed, and the fluorescence band corresponding to the collected signal can be selected according to different needs.

[0024] 3. No hardware is added to the existing temperature measurement system. It is only necessary to collect dual-channel fluorescence attenuation data during measurement. Therefore, the present invention is low-cost and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the fluorescence pathway of rare earth ion dual-doped nanomaterials;

[0026] Figure 2 This is the spectrum of NaYF4 nanocrystals co-doped with Nd (ion 1) and Yb (ion 2) under 800 nm excitation;

[0027] Figure 3 is the law of shortening of Nd fluorescence lifetime with temperature;

[0028] Figure 4 is the law of the extension of Yb fluorescence lifetime with temperature;

[0029] Figure 5 is the variation of the fluorescence lifetime ratio of Nd to Yb with temperature;

[0030] Figure 6 This is a comparison of the temperature measurement sensitivity of this method and the traditional fluorescence lifetime temperature measurement sensitivity. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] The present invention first needs to realize that the fluorescence lifetime of the two rare earth luminescence centers is shortened and prolonged respectively with the increase of ambient temperature. Different energy transfer systems can be used to realize the phenomenon that the rare earth fluorescence lifetime is prolonged with the increase of temperature. The phonon-assisted energy transfer process is used to realize the phenomenon that the rare earth fluorescence lifetime is prolonged with the increase of temperature, such as Figure 1 As shown in the figure, a rare earth ion dual-doped nanofluorescent material is constructed. The excited state energy of ion 1 is slightly higher than the excited state energy of ion 2. At this time, ion 1 will use the vibration energy of lattice phonons to transfer energy to ion 2. The energy transfer process becomes more intense as the temperature rises. When the impact of the energy transfer process is stronger than the temperature quenching effect of ion 2 itself, the fluorescence lifetime τ2 of ion 2 will be extended as the temperature T rises. In addition, due to the simultaneous existence of radiationless relaxation and energy transfer of ion 1, which are aggravated by the increase in temperature, its fluorescence lifetime τ1 will be shortened as the temperature T rises, thereby shortening and extending the lifetimes of the two fluorescence signals as the temperature rises. Figure 3 As shown in Figure 2, the Nd fluorescence lifetime shortens with increasing temperature, as shown in Figure 2. Figure 4 As shown in Figure 2, the Yb fluorescence lifetime increases with increasing temperature.

[0033] For the above rare earth nano fluorescent materials, if the fluorescence lifetimes τ1 and τ2 are used respectively, the relative sensitivity of their respective lifetime temperature measurements are:

[0034]

[0035]

[0036] If the fluorescence lifetime ratio (LLR) of the two is used, the corresponding temperature measurement relative sensitivity becomes:

[0037]

[0038] Clearly, the relative sensitivity of this LLR temperature measurement method is the sum of the two single lifetime temperature measurement methods, which can improve the temperature measurement performance. The temperature measurement is carried out using the ratio of the two fluorescence lifetimes as the sensing parameter, and the obtained temperature measurement sensitivity is the sum of the two fluorescence lifetime temperature measurements used separately.

[0039] The present invention uses a temperature measuring probe prepared by a nano fluorescent material doped with rare earth ions to detect temperature. In the nano fluorescent material, the excited state energy of the doped ion 1 is higher than that of the doped ion 2. The fluorescence lifetime of the doped ion 1 shortens as the temperature increases, while the fluorescence lifetime of the doped ion 2 increases as the temperature increases. A fitting curve of the fluorescence lifetime ratio of the doped ion 1 to the doped ion 2 versus temperature is used as a calibration curve of the temperature measuring probe. The temperature measurement working range of the probe is determined based on a theoretical temperature measurement sensitivity curve. The detected temperature is obtained by reverse deduction based on the measured fluorescence lifetime ratio using a fitting formula corresponding to the calibration curve.

[0040] The method for obtaining a fitting curve of the fluorescence lifetime ratio of the dopant ion 1 and the dopant ion 2 as a function of temperature includes:

[0041] Step 1: placing the temperature measuring probe in an environment with an initial temperature of t0;

[0042] Step 2: Use a signal generator to modulate the excitation wavelength of doped ion 1 and the semiconductor laser outputs a square wave laser to irradiate the temperature measuring probe;

[0043] Step 3: Collect the decay curves of the fluorescence emission wavelengths of dopant ion 1 and dopant ion 2 respectively, and fit them to obtain the fluorescence lifetime curves of dopant ion 1 and dopant ion 2;

[0044] Step 4: Change the ambient temperature, respectively at temperatures t1, t2, ..., t n Repeat step 3 to get t1, t2, ..., t n Fluorescence lifetime curves of dopant ion 1 and dopant ion 2 at different temperatures;

[0045] Step 5: Obtain the fluorescence lifetime curves of dopant 1 and dopant 2 at t0, t1, ..., t n The fluorescence lifetime at the temperature is calculated, and then a data graph of the fluorescence lifetime ratio of the dopant ion 1 and the dopant ion 2 as a function of temperature is plotted. Then, a fitting curve of the fluorescence lifetime ratio of the dopant ion 1 and the dopant ion 2 as a function of temperature is obtained by polynomial fitting.

[0046] according to The fluorescence lifetime curves of dopant ion 1 and dopant ion 2 are fitted, where I and I0 are the fluorescence intensities at time t and the initial time, respectively, and τ is the fluorescence lifetime.

[0047] Theoretical temperature measurement sensitivity curve is based on Plot, where τ1 is the fluorescence lifetime of dopant ion 1, τ2 is the fluorescence lifetime of dopant ion 2, and T represents the temperature.

[0048] The temperature probe is prepared by co-doping NaYF4 nanocrystals with Nd and Yb ions prepared by thermal decomposition or hydrothermal method. The temperature probe is in the form of powder, block, dispersion or film.

[0049] Taking Nd and Yb ion co-doped NaYF4 nanocrystals as an example, the details are as follows:

[0050] Step 1: Prepare Nd and Yb ion co-doped NaYF4 nanocrystals using synthesis techniques such as thermal decomposition and hydrothermal methods. Prepare the nanocrystals into different forms such as powder, block, dispersion, and film as temperature probes according to actual needs.

[0051] Step 2: Place the temperature probe on the electric heating plate and adjust the power of the heating plate to keep the temperature at 30 degrees Celsius. Use a signal generator to modulate an 800-nanometer semiconductor laser. The laser outputs a square wave laser to illuminate the probe. The fluorescence spectrum emitted by the probe is as follows: Figure 2 shown.

[0052] Step 3: Use a fluorescence lifetime spectrometer (or narrowband filter + InGaAs photodetector + oscilloscope) to collect the fluorescence decay curves of Nd ions near 895 nanometers and Yb ions near 980 nanometers, respectively, and obtain their fluorescence lifetimes by fitting according to formula (1).

[0053] Step 4: Adjust the input power of the heating plate to raise the temperature to 60, 90, 120, and 150 degrees Celsius respectively, and repeat step 3.

[0054] Step 5: Draw a data graph of the probe fluorescence lifetime ratio changing with temperature, and use a second-order polynomial to fit the experimental data, such as Figure 5 As shown, the theoretical temperature measurement sensitivity curve of the probe is drawn based on formula (4) to identify the best response and optimal working range of the probe.

[0055] In practical applications of step 6, the fitting curve in step 5 is used as the calibration curve of the temperature measuring probe, and the calibration formula is used to reversely infer the ambient temperature under the condition of the measured fluorescence lifetime ratio to achieve high-sensitivity temperature sensing.

[0056] like Figure 6 As shown, the fluorescence lifetime ratio temperature measurement sensitivity adopted in the present invention is superior to the traditional fluorescence lifetime temperature measurement sensitivity.

[0057] The specific embodiments described above provide a detailed description of the objectives, principles, technical solutions, and beneficial effects of the present invention. It should be understood that the foregoing descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A fluorescence lifetime temperature measurement method using dual-path signals, characterized in that: The temperature is detected by a temperature probe prepared using a nano-fluorescent material doped with rare earth ions. In the nano-fluorescent material, the excited state energy of doped ion 1 is higher than that of doped ion 2. The fluorescence lifetime of doped ion 1 shortens with increasing temperature, while the fluorescence lifetime of doped ion 2 prolongs with increasing temperature. A fitting curve of the fluorescence lifetime ratio of doped ion 1 to doped ion 2 versus temperature is used as a calibration curve for the temperature probe. The temperature measurement operating range of the probe is determined based on the theoretical temperature measurement sensitivity curve. The detected temperature is obtained by inverse deduction based on the measured fluorescence lifetime ratio using the fitting formula corresponding to the calibration curve.

2. The fluorescence lifetime temperature measurement method using dual-path signals according to claim 1, characterized in that: The method for obtaining a fitting curve of the fluorescence lifetime ratio of the dopant ion 1 and the dopant ion 2 as a function of temperature comprises: Step 1: placing the temperature measuring probe in an environment with an initial temperature of t0; Step 2: Use a signal generator to modulate the excitation wavelength of doped ion 1 and the semiconductor laser outputs a square wave laser to irradiate the temperature measuring probe; Step 3: Collect the decay curves of the fluorescence emission wavelengths of dopant ion 1 and dopant ion 2 respectively, and fit them to obtain the fluorescence lifetime curves of dopant ion 1 and dopant ion 2; Step 4: Change the ambient temperature, respectively at temperatures t1, t2, ..., t n Repeat step 3 to get t1, t2, ..., t n Fluorescence lifetime curves of dopant ion 1 and dopant ion 2 at different temperatures; Step 5: Obtain the fluorescence lifetime curves of dopant 1 and dopant 2 at t0, t1, ..., t n The fluorescence lifetime at the temperature is calculated, and then a data graph of the fluorescence lifetime ratio of the dopant ion 1 and the dopant ion 2 as a function of temperature is plotted. Then, a fitting curve of the fluorescence lifetime ratio of the dopant ion 1 and the dopant ion 2 as a function of temperature is obtained by polynomial fitting.

3. The fluorescence lifetime temperature measurement method using dual-path signals according to claim 2, characterized in that: according to The fluorescence lifetime curves of dopant ion 1 and dopant ion 2 are fitted, where I and I0 are the fluorescence intensities at time t and the initial time, respectively, and τ is the fluorescence lifetime.

4. The fluorescence lifetime temperature measurement method using dual-path signals according to claim 1, characterized in that: The theoretical temperature measurement sensitivity curve is based on Plot, where τ1 is the fluorescence lifetime of dopant ion 1, τ2 is the fluorescence lifetime of dopant ion 2, and T represents the temperature.

5. The fluorescence lifetime temperature measurement method using dual-path signals according to any one of claims 1 to 4, characterized in that: The temperature measuring probe is prepared by co-doping NaYF4 nanocrystals with Nd and Yb ions prepared by thermal decomposition or hydrothermal method. The temperature measuring probe is in the form of powder, block, dispersion or film.

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