A multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement

Abstract

This invention discloses a multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement. The probe composite material comprises a substrate, a photonic crystal, gold nanorods, and Er... 3+ Highly doped core-shell upconversion nanoparticles. Through the synergistic effect of photonic crystals, plasma, and a low-temperature field, the upconversion luminescence intensity and signal-to-noise ratio are significantly enhanced. Utilizing highly doped Er... 3+ The system features multi-wavelength excitation and emission characteristics. This probe can achieve six temperature measurement modes based on the intensity ratio of near-infrared and green light emission under single-wavelength excitation at 808nm, 980nm, or 1532nm. This invention solves the problems of single excitation modes and low temperature sensitivity in the low-temperature range of existing technologies, achieving high-sensitivity and high-precision temperature detection in a wide temperature range of 80K to 300K, with a maximum relative sensitivity of 7.06%–14.95%K. ‑1 It has broad application prospects in low-temperature sensing in fields such as biomedicine and microelectronics.

Description

Technical Field

[0001] This invention relates to the field of upconversion luminescence enhancement and temperature detection technology, specifically to a multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement. Background Technology

[0002] With the rapid development of micro- and nano-scale temperature measurement technologies in fields such as biomedical diagnostics, integrated optoelectronic devices, quantum physics, and extreme environment monitoring, higher demands are being placed on the sensitivity, accuracy, and reliability of temperature detection. Non-contact optical temperature measurement technologies based on luminescent materials, especially upconversion luminescent materials, have become a research hotspot in the field of high-precision temperature detection due to their advantages such as low background fluorescence interference, strong penetration ability into biological tissues, and good photochemical stability.

[0003] However, existing ratiometric fluorescent thermometers based on upconversion luminescent materials still face the following technical bottlenecks:

[0004] Limited excitation modes: Most rely on a single wavelength (such as 980nm) for excitation, which limits their application flexibility and reliability in complex measurement environments.

[0005] Temperature measurement is difficult in the low-temperature range: In the low-temperature range below 100K, due to insufficient phonon energy, the thermal excitation population efficiency of high-energy particles is significantly reduced, resulting in weak luminescence signals and making it difficult to achieve stable and reliable temperature measurement.

[0006] Low luminous efficiency: The luminous efficiency of traditional upconversion luminescent systems is limited, which restricts further improvement of temperature measurement signal-to-noise ratio and sensitivity.

[0007] Although existing research has attempted to enhance upconversion luminescence by introducing photonic crystal structures, plasma structures, or utilizing low-temperature environments, the enhancement effect of a single modulation method is limited and cannot meet the application requirements of high-sensitivity and high-precision temperature detection. Therefore, how to effectively enhance upconversion luminescence through multi-method synergy and construct a temperature probe with both high sensitivity and multi-mode detection capabilities is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, this invention provides a multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement. Through the synergistic effect of photonic crystals, plasma, and a low-temperature field, it significantly enhances the upconversion luminescence intensity and is based on highly doped Er... 3+ The system's multi-wavelength response characteristics enable six temperature measurement modes under excitation at three wavelengths: 808nm, 980nm, or 1532nm, significantly improving the sensitivity, accuracy, and application flexibility of temperature detection.

[0009] This invention provides a multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement, comprising:

[0010] Base;

[0011] A photonic crystal thin film disposed on the substrate;

[0012] Gold nanorods (AuNRs) attached to the photonic crystal film;

[0013] And upconversion nanoparticles attached to the photonic crystal film and gold nanorods;

[0014] The upconversion nanoparticles have a core-shell structure, wherein the active luminescent core is doped with the activator Er. 3+ An inert protective shell is applied to the surface of the active luminescent core.

[0015] Preferably, Er in the active luminescent core 3+ The molar percentage of doping concentration is 25%~100%.

[0016] Preferably, the main matrix is ​​NaYF4, NaLuF4, or NaGdF4; the material of the inert protective shell is NaYF4, NaLuF4, or NaGdF4.

[0017] Preferably, the photonic crystal is a photonic crystal with a face-centered cubic (FCC) lattice structure formed by the self-assembly of polymethyl methacrylate (PMMA) microspheres, and the close-packed plane (111 plane) of the photonic crystal structure is parallel to the substrate.

[0018] Preferably, the gold nanorods have an average length of 70-90 nm and an average diameter of 15-20 nm.

[0019] This invention provides a multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement, which is prepared by the following method, including the following steps:

[0020] Step 1, Preparation of Er 3+ Highly doped core-shell upconversion nanoparticles;

[0021] Step 2: Fabricate a photonic crystal thin film on a substrate using a self-assembly method;

[0022] Step 3: Prepare gold nanorods;

[0023] Step 4: Add the gold nanorod dispersion to the photonic crystal film region, dry it, and then add the upconversion nanoparticle dispersion to the same region. After drying, a composite film is obtained, which is the upconversion fluorescence temperature probe.

[0024] Preferably, the preparation of upconversion nanoparticles in step 1 includes the following steps:

[0025] (1) Preparation of active luminescent cores;

[0026] Will contain Er 3+ Lanthanide hydrated chloride was added to a reaction vessel containing oleic acid (OA) and 1-octadecene ODE. The mixture was heated to 150-160°C under an inert gas atmosphere and stirred thoroughly until the raw materials were completely dissolved to form a homogeneous and transparent solution, which was then cooled. Subsequently, a methanol solution containing NaOH and NH4F was added, and the mixture was heated at 80-85°C to remove the methanol. The temperature was then gradually increased to 300°C over 20 minutes and held for at least 60 minutes before heating was stopped. The system was then cooled to room temperature, and the nanoparticles were collected by centrifugation, washed with ethanol, and finally uniformly dispersed in cyclohexane for later use.

[0027] By adjusting Er in lanthanide hydrated chloride 3+ The proportion of chloride affects the Er content in the obtained active luminescent nanoparticles. 3+ The molar percentage of doping concentration is 25%-100%; the lanthanide is any one of Y, Gd or Lu;

[0028] (2) Preparation of inert protective shell precursor;

[0029] (CF3COO)3Ln and CF3COONa were mixed at a molar ratio of 1:1 and then transferred to a reaction vessel containing OA and ODE. The mixture was heated to 120-130°C and stirred thoroughly under an inert gas flow protection until it was completely dissolved and dehydrated. It was then cooled to room temperature as an inert protective shell precursor solution. The Ln was any one of Y, Gd or Lu.

[0030] (3) Preparation of an active luminescent core-inert protective shell;

[0031] The active luminescent core nanoparticles obtained in step (1) were dispersed in a reaction vessel containing OA and ODE, and cyclohexane was removed by heating. The solution was then heated to 300°C under inert gas flow protection, and then the inert protective shell precursor solution was gradually injected in four batches at 15-minute intervals. After the last addition, the reaction was kept at a constant temperature to ensure complete shell growth. After cooling to room temperature, the product was precipitated with ethanol, washed, and then dispersed in cyclohexane for later use.

[0032] Preferably, step 2, the preparation of the photonic crystal thin film, includes the following steps:

[0033] Methyl methacrylate (MMA), deionized water, and potassium persulfate (K2S2O8) were added to a reaction vessel. The mixture was continuously stirred in an oil bath and heated to 90°C for at least 90 minutes. After cooling to room temperature, a PMMA microsphere dispersion was obtained and stored for later use. To adjust the size of the microspheres, deionized water, the PMMA microsphere dispersion, purified MMA, and azobisisobutyronitrile (AIBN) were added to a reaction vessel and stirred thoroughly in a 90°C oil bath. The above swelling polymerization steps were repeated until the microspheres reached the desired size, resulting in a PMMA microsphere suspension. Subsequently, a clean substrate was vertically inserted into the PMMA microsphere suspension and dried in an oven. Solvent evaporation induced self-assembly to form a photonic crystal film.

[0034] Preferably, step 3, preparing gold nanorods, includes the following steps:

[0035] (1) Seed solution preparation;

[0036] Under vigorous stirring, chloroauric acid (HAuCl4) solution and hexadecyltrimethylammonium bromide (CTAB) solution were mixed evenly, and then freshly prepared sodium borohydride (NaBH4) solution was quickly added. After stirring, the seed solution was obtained and allowed to stand at room temperature for later use.

[0037] (2) Preparation of gold nanorods;

[0038] Hexadecyltrimethylammonium bromide (CTAB) and sodium oleate (NaOL) were dissolved in deionized water and stirred at 70°C until completely dissolved, then cooled to 30°C. Silver nitrate (AgNO3) solution was added first and allowed to stand, then HAuCl4 solution was added and stirred for at least 90 minutes. Hydrochloric acid was then added and stirring continued. Ascorbic acid solution was then added and stirred vigorously for at least 30 seconds. Finally, the above seed solution was added, and the mixture was allowed to stand at 30°C to react, yielding gold nanorods.

[0039] This invention also provides a temperature detection method based on a multi-field synergistic enhancement multi-mode upconversion fluorescence temperature probe, comprising the following steps:

[0040] (1) Place the upconversion fluorescence temperature probe in the environment of the temperature to be measured;

[0041] (2) Select any near-infrared laser of wavelength 808nm, 980nm or 1532nm as the excitation source, irradiate the temperature probe, and collect its upconversion emission spectrum at different temperatures;

[0042] (3) Calculate the fluorescence intensity ratio (LIR) of the near-infrared emission peak to the green emission peak in the emission spectrum, wherein the near-infrared emission peak is selected from one of the emission peaks of 808 nm, 980 nm or 1532 nm, and the green emission peak is the emission peak of 545 nm;

[0043] (4) Calculate the temperature value in the environment to be measured based on the pre-established standard relationship curve between fluorescence intensity ratio and temperature.

[0044] Preferably, the standard relationship curve between the fluorescence intensity ratio and temperature satisfies the formula: Where LIR is the fluorescence intensity ratio, A is a constant, kB is the Boltzmann constant, ΔE is the fitted value, and T is the absolute temperature;

[0045] 808nm as the excitation source:

[0046] The temperature sensing curves corresponding to the 980nm / 545nm modes are as follows: ;

[0047] The temperature sensing curves corresponding to the 1532nm / 545nm modes are as follows: ;

[0048] 980nm as the excitation source:

[0049] The temperature sensing curves corresponding to the 808nm / 545nm modes are as follows: ;

[0050] The temperature sensing curves corresponding to the 1532nm / 545nm modes are as follows: ;

[0051] 1532nm as the excitation source:

[0052] The temperature sensing curves corresponding to the 808nm / 545nm modes are as follows: ;

[0053] The temperature sensing curves corresponding to the 980nm / 545nm modes are as follows: .

[0054] Working principle of the invention:

[0055] The upconversion luminescence enhancement strategy provided by this invention, which combines photonic crystals, plasma, and a low-temperature field, achieves the regulation and enhancement of the upconversion luminescence process by introducing an external multi-physics field, wherein:

[0056] Photonic crystal enhancement mechanism: Photonic crystals form a photonic bandgap effect through their periodic arrangement, which modulates the local photon distribution, enabling the excitation light to be locally enhanced near the luminescence center, thereby improving the upconversion absorption efficiency and thus increasing the upconversion luminescence intensity.

[0057] Gold nanorod plasmon enhancement mechanism: By introducing a gold nanorod structure, a local surface plasmon resonance effect is excited on its surface, generating a strong local electromagnetic field, which significantly enhances the excitation light and thus significantly improves the upconversion luminescence intensity.

[0058] Low-temperature field enhancement mechanism: By applying a low-temperature environment, the non-radiative relaxation process is effectively suppressed, multiphonon relaxation loss is reduced, thereby enhancing the upconversion luminescence efficiency.

[0059] This invention constructs a highly sensitive upconversion fluorescence temperature probe with three wavelength excitations and six testing modes, based on Er 3+ Temperature detection is achieved using the upconversion luminescence properties of highly doped systems. Among these, high concentrations of Er... 3+ This can enhance the absorption capacity of nanoparticles for excitation light, thereby increasing the upconversion luminescence intensity; simultaneously, Er 3+ The ions possess a rich, stepped energy level structure, enabling them to respond to a variety of excitation wavelengths, including 808 nm. 4 I 15 / 2 → 4 I 9 / 2 ), 980nm ( 4 I 15 / 2 → 4 I 11 / 2 , 4 I 11 / 2 → 4 F 7 / 2 ), 1532nm ( 4 I 15 / 2 → 4 I 13 / 2 In addition, Er 3+ Ions, under multi-wavelength excitation, can generate multi-band emission through transitions at different energy levels, including green light in the visible region. 4 S 3 / 2 → 4 I 15 / 2 ), red light ( 4 F 9 / 2 → 4 I 15 / 2 As well as emission in the near-infrared region at 808nm, 980nm, and 1532nm, thus enabling multi-mode temperature detection; furthermore, Er 3+ Highly doped systems exhibit significant temperature-dependent luminescence properties. When Er 3+ As the doping concentration increases, the interiono-ionic interaction strengthens due to the decreased interiono-ionic distance. At room temperature, phonon-assisted processes can compensate for Er... 3+ -Er 3+ The energy difference between the cross-relaxations enhances the cross-relaxation process, resulting in stronger red light emission (655nm) from the system. 4 F9 / 2 → 4 I 15 / 2 ) and weaker green light emission (525nm, 2 H 11 / 2 → 4 I 15 / 2 545nm 4 S 3 / 2 → 4 I 15 / 2 As temperature decreases, lattice vibrations weaken, phonon-assisted effects diminish, and the cross-relaxation rate decreases, thereby suppressing the nonradiative relaxation process of the green emission level and increasing the intensity of green upconversion luminescence. Meanwhile, near-infrared emission primarily originates from transitions between lower energy levels and is less dependent on phonon participation; its luminescence intensity remains relatively stable with temperature changes. Based on these characteristics, a fluorescence intensity ratio-based temperature detector can be constructed using the intensity ratio between near-infrared and green emission, thus achieving highly sensitive detection of temperature changes.

[0060] The beneficial effects of this invention are:

[0061] This invention provides a multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement, based on Er 3+ A multi-field synergistic enhancement method for upconversion luminescence modulation in highly doped systems is proposed. Through the synergistic effect of photonic crystals, gold nanorod plasmas, and low-temperature fields, multi-field modulation of the upconversion luminescence process is achieved. A high-sensitivity, high-temperature-precision multi-mode upconversion fluorescence temperature probe is constructed, thereby improving the upconversion luminescence intensity and overcoming the problem of limited modulation effect of single physical fields.

[0062] This invention provides a multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement. The synergistic effect of photonic crystals, gold nanorod plasma, and a low-temperature field enhances upconversion luminescence and Er... 3+ The highly doped system exhibits strong temperature dependence and high sensitivity with three-wavelength excitation and six testing modes. Based on a cross-relaxation-dominated upconversion luminescence mechanism, it differs from traditional temperature measurement methods based on the emission intensity ratio of rare-earth ion thermally coupled energy levels. This allows for temperature detection over a wide temperature range of 80–300 K, meeting the needs of various measurement scenarios and improving application flexibility. Furthermore, each testing mode maintains high sensitivity and accuracy, with a maximum relative sensitivity of 7.06–14.95% K. -1 It is significantly superior to traditional upconversion temperature probe materials (such as NaYF4:20%Yb,2%Er@NaYF4), achieving ultrasensitive temperature detection at low temperatures. Attached Figure Description

[0063] Figure 1 This is a schematic diagram of the upconversion emission of rare earth ion energy levels under three-wavelength excitation according to the present invention;

[0064] Figure 2 These are TEM images of the upconversion nanoparticles NaErF4 (a) and NaErF4@NaYF4 (b) obtained in Example 1 of this invention.

[0065] Figure 3 The X-ray diffraction pattern of the upconversion nanoparticles obtained in Example 1 of this invention;

[0066] Figure 4 The image shows the SEM image (a) and transmission spectrum (b) of the photonic crystal obtained in Example 2 of this invention.

[0067] Figure 5 The image shows the SEM image (a) and absorption spectrum (b) of the gold nanorods obtained in Example 3 of this invention.

[0068] Figure 6 This is a SEM image of the composite thin film obtained in Example 4 of the present invention;

[0069] Figure 7 The upconversion fluorescence temperature probe obtained in Example 5 of this invention has a temperature-dependent upconversion emission spectrum (a), temperature sensing curve (b), and sensing sensitivity (c) under 808 nm excitation.

[0070] Figure 8 The upconversion fluorescence temperature probe obtained in Example 6 of this invention has a temperature-dependent upconversion emission spectrum (a), temperature sensing curve (b), and sensing sensitivity (c) under 980 nm excitation.

[0071] Figure 9 The upconversion fluorescence temperature probe obtained in Example 7 of this invention has a temperature-dependent upconversion emission spectrum (a), temperature sensing curve (b), and sensing sensitivity (c) under 1532 nm excitation. Detailed Implementation

[0072] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0073] Example 1

[0074] This embodiment provides a method for preparing upconversion nanoparticles with a luminescent core and an inert protective shell, comprising the following steps:

[0075] (1) Preparation of active luminescent cores;

[0076] 1 mmol of erbium chloride hexahydrate (ErCl3・6H2O) was added to a three-necked flask containing 6 mL of oleic acid OA and 15 mL of 1-octadecene ODE. The mixture was heated to 150 °C and stirred thoroughly for 30 min under an argon atmosphere until the raw materials were completely dissolved to form a homogeneous and transparent solution. The solution was then cooled to 35 °C. Subsequently, a methanol solution containing 2.5 mmol of NaOH and 4 mmol of NH4F was added, and the mixture was heated at 80-85 °C to remove the methanol. The temperature was then gradually increased to 300 °C over 20 min and held for 60 min before heating was stopped. The system was then cooled to room temperature, and the nanoparticles were collected by centrifugation, washed with ethanol, and finally uniformly dispersed in cyclohexane for later use.

[0077] (2) Preparation of inert protective shell precursor;

[0078] Mix CF3COOY and CF3COONa at a molar ratio of 1:1, then transfer the mixture to a reaction flask containing equal volumes of OA and ODE. Heat the mixture to 120°C under an argon atmosphere and stir thoroughly for 30 minutes until it is completely dissolved and dehydrated. Then cool it to room temperature as an inert protective shell precursor solution.

[0079] (3) Preparation of an active luminescent core-inert protective shell;

[0080] 0.25 mmol of the active luminescent nanoparticles obtained in step (1) were dispersed in a three-necked flask containing 5 mL of OA and 5 mL of LODE. The cyclohexane was removed by heating at 85 °C for 30 minutes. The solution was then heated to 300 °C under an argon atmosphere. Subsequently, a total of 1 mmol of inert protective shell precursor solution was gradually injected in four portions at 15-minute intervals. After the last addition, the reaction was continued for 45 minutes to ensure complete shell growth. After cooling to room temperature, the product was precipitated with ethanol, washed, and then dispersed in cyclohexane for later use.

[0081] Figure 2 The images show transmission electron microscopy (TEM) images of the active luminescent core NaErF4 and upconversion nanoparticles NaErF4@NaYF4 prepared in Example 1 of this invention. They are uniform in size and well dispersed. The average particle sizes of NaErF4 and NaErF4@NaYF4 were measured to be 18.3 nm and 36.7 nm, respectively.

[0082] Figure 3 The X-ray diffraction pattern of the upconversion nanoparticles prepared in Example 1 of this invention is shown. The XRD pattern of the nanoparticles matches the standard pattern, and the corresponding crystal phase is a pure hexagonal phase.

[0083] Example 2

[0084] This embodiment provides a method for preparing a photonic crystal thin film, including the following steps:

[0085] 6 mL of methyl methacrylate (MMA), 80 mL of deionized water, and 36 mg of potassium persulfate (K2S2O8) were added to a 250 mL three-necked round-bottom flask. The mixture was continuously stirred in an oil bath and heated to 90 °C for 90 minutes. After cooling to room temperature, a PMMA microsphere dispersion was obtained and stored for later use. To adjust the size of the microspheres, 40 mL of deionized water, 40 mL of the PMMA microsphere dispersion, 6 mL of purified MMA, and 36 mg of azobisisobutyronitrile (AIBN) were added to a three-necked round-bottom flask. The mixture was stirred thoroughly in an oil bath at 90 °C for 30 minutes. The above swelling polymerization steps were repeated until the microspheres reached the desired size, resulting in a PMMA microsphere suspension. Subsequently, a clean glass substrate was vertically inserted into the PMMA microsphere suspension and dried in an oven at 32 °C. Solvent evaporation induced self-assembly to form a photonic crystal film, thus completing the self-assembly.

[0086] Figure 4 (a) is the SEM image of the photonic crystal prepared in Example 2 of the present invention. The photonic crystal has a face-centered cubic (FCC) lattice structure, and the close-packed planes (111 planes) of the structure are parallel to the glass substrate. The lattice constant is 330 nm.

[0087] Figure 4 (b) is the transmission spectrum of the photonic crystal prepared in Example 2 of the present invention, with the transmission peak located at 980 nm.

[0088] Example 3

[0089] This embodiment provides a method for preparing gold nanorods, including the following steps:

[0090] (1) Seed solution preparation;

[0091] Under vigorous stirring, 0.25 mL of 0.01 M chloroauric acid (HAuCl4) solution and 9.75 mL of 0.1 M hexadecyltrimethylammonium bromide (CTAB) solution were mixed thoroughly. Then, 0.048 mL of freshly prepared 0.1 M sodium borohydride (NaBH4) solution was quickly added. After stirring for 2 minutes, the solution was allowed to stand at room temperature for 60 minutes to obtain the seed solution, which was then stored for later use.

[0092] (2) Preparation of gold nanorods;

[0093] 0.7 g of cetyltrimethylammonium bromide (CTAB) and 1.234 g of sodium oleate (NaOL) were dissolved in 50 mL of deionized water and stirred at 70 °C for 30 minutes until completely dissolved, then cooled to 30 °C. First, 0.72 mL of 0.01 M silver nitrate (AgNO3) solution was added and allowed to stand for 15 minutes, then 2.5 mL of 0.01 M HAuCl4 solution was added and stirred for 90 minutes. Next, 1.8 mL of 1 M hydrochloric acid was added and stirred for another 15 minutes. Then, 0.08 mL of 0.1 M ascorbic acid solution was added and stirred vigorously for 30 seconds. Finally, 0.04 mL of the above seed solution was added, and the mixture was allowed to stand at 30 °C for 12 hours to obtain a gold nanorod (AuNRs) dispersion.

[0094] Figure 5 (a) is the SEM image of the gold nanorods prepared in Example 3 of the present invention. The nanorods are randomly arranged and have good dispersion and uniform size, with an average length of 80.7 nm and an average diameter of 17.8 nm.

[0095] Figure 5 (b) is the absorption spectrum of the gold nanorods prepared in Example 3 of the present invention, with the absorption peak located at around 980 nm.

[0096] Example 4

[0097] This embodiment provides a multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement, which is prepared by the following method, including the following steps:

[0098] First, a 0.5 × 0.5 cm mark is made on the glass substrate of Example 2 by cutting. 2 A square photonic crystal thin film region;

[0099] Take 20 μL of the gold nanorod dispersion from Example 3 and drop it onto the photonic crystal film region. Let it air dry naturally at room temperature. During the solvent evaporation process, the gold nanorods will be deposited and arranged in the pores and surface of the photonic crystal.

[0100] Then, 20 μL of the upconversion nanoparticle dispersion from Example 1 was added to the same area. As the cyclohexane gradually evaporated, the upconversion nanoparticles were loosely fixed on the composite structure formed by the photonic crystal and the gold nanorods. After drying, a composite film was obtained, which is the upconversion fluorescence temperature probe.

[0101] Figure 6 The image shows the SEM pattern of the composite film prepared in Example 4 of this invention. Upconversion nanoparticles and gold nanorods mainly fill the pores between the photonic crystal microspheres.

[0102] Example 5: Temperature sensing performance test under 808nm excitation;

[0103] The temperature probe prepared in Example 4 was placed in a temperature-controlled cryogenic optical cavity. Using an 808nm laser as the excitation source, the upconversion emission spectra of the probe at different temperature points in the range of 80K to 300K were collected, with the main emission peaks located at 980nm, 1532nm, and 545nm.

[0104] Figure 7 (a) is the temperature-dependent upconversion emission spectrum of the upconversion fluorescent nanoprobe in this embodiment under 808nm laser irradiation.

[0105] It can be seen that as the temperature gradually decreases from 300K to 80K, the green light band (545nm, corresponding to Er) increases. 3+ of 4 S 3 / 2 → 4 I 15 / 2 The emission intensity of the transition (transition) is significantly improved; compared with room temperature, the green light emission at 80K is enhanced by approximately 64.3 times; while in the infrared band (980nm, 4 I 11 / 2 → 4 I 15 / 2 1532nm, 4 I 13 / 2 → 4 I 15 / 2 The emission intensity of the two instruments remained almost constant, with the maximum variation being only about 2.2 times and 0.1 times, respectively.

[0106] Calculate the fluorescence intensity ratio (LIR) at 980nm and 545nm, and 1532nm and 545nm respectively, plot the fluorescence intensity ratio (LIR)-temperature (T) graph and apply the formula. The temperature sensing curve was fitted.

[0107] like Figure 7 As shown in (b), the fitting results are as follows:

[0108] The temperature sensing curves corresponding to the 980nm / 545nm modes are as follows: ;

[0109] The temperature sensing curves corresponding to the 1532nm / 545nm modes are as follows: .

[0110] Figure 7 (c) shows the sensing sensitivity curve of the upconversion fluorescent nanoprobe in the example under 808 nm laser irradiation. The maximum relative sensitivity using the 980 nm / 545 nm mode and the 1532 nm / 545 nm mode was 7.1% K. -1 and 15.0%K -1 .

[0111] Example 6: Temperature sensing performance test under 980nm excitation;

[0112] The same method as in Example 5 was used, but the excitation source was replaced with a 980nm laser. The temperature-dependent emission spectrum is as follows: Figure 8 As shown in (a), a similar phenomenon was observed where the green light intensity significantly increased with decreasing temperature; compared to room temperature, green light emission was approximately 600 times stronger at 80K; while in the infrared band (808nm, 4 I 9 / 2 → 4 I 15 / 2 1532nm, 4 I 13 / 2 → 4 I 15 / 2 The emission intensity of the two instruments remained almost constant, with the maximum variation being only about 6.2 times and 1.5 times, respectively.

[0113] The fluorescence intensity ratios at 808nm to 545nm and 1532nm to 545nm were calculated and fitted, and the results are as follows: Figure 8 As shown in (b); the fitting results are as follows:

[0114] The temperature sensing curves corresponding to the 808nm / 545nm modes are as follows: ;

[0115] The temperature sensing curves corresponding to the 1532nm / 545nm modes are as follows: .

[0116] Figure 8 (c) shows the sensing sensitivity curve of the upconversion nanoprobe under 980nm laser irradiation in this embodiment. The maximum relative sensitivity using the 808nm / 545nm mode and the 1532nm / 545nm mode is 8.1%K. -1 and 13.5%K -1 .

[0117] Example 7: Temperature sensing performance test under 1532nm excitation;

[0118] The same method as in Example 5 was used, but the excitation source was replaced with a 1532nm laser. The temperature-dependent emission spectrum is as follows: Figure 9 As shown in (a). Compared to room temperature, green light emission is enhanced by approximately 405 times at 80K; while in the infrared band (808nm, 4 I 9 / 2 → 4 I 15 / 2 980nm, 4 I 11 / 2 → 4 I 15 / 2The emission intensity remained almost constant, with the maximum variation being only about 8.6 times and 2.5 times, respectively.

[0119] The fluorescence intensity ratios at 808nm to 545nm and 980nm to 545nm were calculated and fitted, and the results are as follows: Figure 9 As shown in (b). The fitting results are as follows:

[0120] The temperature sensing curves corresponding to the 808nm / 545nm modes are as follows: ;

[0121] The temperature sensing curves corresponding to the 980nm / 545nm modes are as follows: .

[0122] Figure 9 (c) shows the sensing sensitivity curve of the upconversion nanoprobe under 1532nm laser irradiation in this embodiment. The maximum relative sensitivity using the 808nm / 545nm and 980nm / 545nm modes is 9.0%K. -1 and 12.7%K -1 .

[0123] The results of Examples 5-7 above fully demonstrate that the temperature probe provided by the present invention can achieve ultra-high sensitivity temperature detection in a wide low temperature range of 80-300K, under three excitation wavelengths and six ratio calculation modes.

Claims

1. A multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement, characterized in that, include: Base; A photonic crystal film disposed on the substrate; the photonic crystal is a face-centered cubic lattice structure formed by the self-assembly of polymethyl methacrylate microspheres, and the close-packed plane of the photonic crystal structure is parallel to the substrate; Gold nanorods attached to the photonic crystal film; And upconversion nanoparticles attached to the photonic crystal film and gold nanorods; the gold nanorod dispersion is dropped onto the region of the photonic crystal film, dried, and then the upconversion nanoparticle dispersion is dropped onto the same region, dried to obtain a composite film, namely the upconversion fluorescence temperature probe. The upconversion nanoparticles have a core-shell structure, wherein the active luminescent core is doped with the activator Er. 3+ An inert protective shell covers the surface of the active luminescent core, and Er in the active luminescent core... 3+ The molar percentage of doping concentration is 25%~100%; Based on Er 3+ A multi-field synergistic enhancement method for upconversion luminescence modulation in highly doped systems achieves multi-field modulation of the upconversion luminescence process through the synergistic effect of photonic crystals, gold nanorod plasma, and a low-temperature field. It features high sensitivity with three-wavelength excitation and six testing modes, enabling temperature detection over a wide temperature range of 80–300 K. The testing modes include: 808nm as the excitation source: 980nm / 545nm mode; 1532nm / 545nm mode; 980nm as the excitation source: 808nm / 545nm mode; 1532nm / 545nm mode; 1532nm as the excitation source: 808nm / 545nm mode; 980nm / 545nm mode.

2. The multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement according to claim 1, characterized in that: The main matrix is ​​NaYF4, NaLuF4, or NaGdF4; the inert protective shell is made of NaYF4, NaLuF4, or NaGdF4.

3. The multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement according to claim 1, characterized in that: The gold nanorods have an average length of 70-90 nm and an average diameter of 15-20 nm.

4. The multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement according to claim 1, characterized in that: It is prepared by the following method, including the following steps: Step 1, Preparation of Er 3+ Highly doped core-shell upconversion nanoparticles; Step 2: Prepare a photonic crystal thin film on the substrate using a self-assembly method; Step 3: Prepare gold nanorods; Step 4: Add the gold nanorod dispersion to the photonic crystal film region, dry it, and then add the upconversion nanoparticle dispersion to the same region. After drying, a composite film is obtained, which is the upconversion fluorescence temperature probe.

5. The multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement according to claim 4, characterized in that: Step 1 involves the preparation of upconversion nanoparticles, which includes the following steps: (1) Preparation of active luminescent cores; Will contain Er 3+ Lanthanide hydrated chloride was added to a reaction vessel containing oleic acid (OA) and 1-octadecene ODE. The mixture was heated to 150-160°C under an inert gas atmosphere and stirred thoroughly until the raw materials were completely dissolved to form a homogeneous and transparent solution, which was then cooled. Subsequently, a methanol solution containing NaOH and NH4F was added, and the mixture was heated at 80-85°C to remove the methanol. The temperature was then gradually increased to 300°C over 20 minutes and held for at least 60 minutes before heating was stopped. The system was then cooled to room temperature, and the nanoparticles were collected by centrifugation, washed with ethanol, and finally uniformly dispersed in cyclohexane for later use. By adjusting Er in lanthanide hydrated chloride 3+ The proportion of chloride affects the Er content in the obtained active luminescent nanoparticles. 3+ The molar percentage of doping concentration is 25%-100%; the lanthanide is any one of Y, Gd or Lu; (2) Preparation of inert protective shell precursor; (CF3COO)3Ln and CF3COONa were mixed at a molar ratio of 1:1 and then transferred to a reaction vessel containing OA and ODE. The mixture was heated to 120-130°C and stirred thoroughly under an inert gas flow protection until it was completely dissolved and dehydrated. It was then cooled to room temperature as an inert protective shell precursor solution. The Ln was any one of Y, Gd or Lu. (3) Preparation of an active luminescent core-inert protective shell; The active luminescent core nanoparticles obtained in step (1) were dispersed in a reaction vessel containing OA and ODE, and cyclohexane was removed by heating. The solution was then heated to 300°C under inert gas flow protection, and then the inert protective shell precursor solution was gradually injected in four batches at 15-minute intervals. After the last addition, the reaction was kept at a constant temperature to ensure complete shell growth. After cooling to room temperature, the product was precipitated with ethanol, washed, and then dispersed in cyclohexane for later use.

6. The multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement according to claim 4, characterized in that: Step 2, the fabrication of the photonic crystal thin film, includes the following steps: Methyl methacrylate, deionized water, and potassium persulfate were added to a reaction vessel. The mixture was continuously stirred in an oil bath and heated to 90°C for at least 90 minutes. After cooling to room temperature, a PMMA microsphere dispersion was obtained and stored for later use. To adjust the size of the microspheres, deionized water, the PMMA microsphere dispersion, purified methyl methacrylate, and azobisisobutyronitrile were added to a reaction vessel and stirred thoroughly in a 90°C oil bath. The above swelling polymerization steps were repeated until the microspheres reached the desired size, resulting in a PMMA microsphere suspension. Subsequently, a clean substrate was vertically inserted into the PMMA microsphere suspension and dried in an oven. Solvent evaporation induced self-assembly to form a photonic crystal film.

7. The multi-mode upconversion fluorescence temperature probe based on multi-field synergistic enhancement according to claim 4, characterized in that: Step 3, the preparation of gold nanorods, includes the following steps: (1) Seed solution preparation; Under vigorous stirring, the chloroauric acid solution and the hexadecyltrimethylammonium bromide solution were mixed evenly, and then freshly prepared sodium borohydride solution was quickly added. After stirring, the seed solution was obtained and left to stand at room temperature for later use. (2) Preparation of gold nanorods; Hexadecyltrimethylammonium bromide and sodium oleate were dissolved in deionized water and stirred at 70°C until completely dissolved, then cooled to 30°C. Silver nitrate solution was added first and allowed to stand, then HAuCl4 solution was added and stirred for at least 90 minutes. Hydrochloric acid was then added and stirring continued. Ascorbic acid solution was then added and stirred vigorously for at least 30 seconds. Finally, the above seed solution was added, and the mixture was allowed to stand at 30°C to react, yielding gold nanorods.

8. A temperature detection method based on a multi-mode upconversion fluorescence temperature probe with multi-field synergistic enhancement as described in any one of claims 1-7, characterized in that: Includes the following steps: (1) Place the upconversion fluorescence temperature probe in the environment of the temperature to be measured; (2) Select any near-infrared laser of wavelength 808nm, 980nm or 1532nm as the excitation source, irradiate the temperature probe, and collect its upconversion emission spectrum at different temperatures; (3) Calculate the fluorescence intensity ratio of the near-infrared emission peak to the green emission peak in the emission spectrum, wherein the near-infrared emission peak is selected from one of the emission peaks of 808nm, 980nm or 1532nm, and the green emission peak is the emission peak of 545nm; (4) Calculate the temperature value in the environment to be measured based on the pre-established standard relationship curve between fluorescence intensity ratio and temperature; 808nm as the excitation source: The temperature sensing curves corresponding to the 980nm / 545nm modes are as follows: ; The temperature sensing curves corresponding to the 1532nm / 545nm modes are as follows: ; 980nm as the excitation source: The temperature sensing curves corresponding to the 808nm / 545nm modes are as follows: ; The temperature sensing curves corresponding to the 1532nm / 545nm modes are as follows: ; 1532nm as the excitation source: The temperature sensing curves corresponding to the 808nm / 545nm modes are as follows: ; The temperature sensing curves corresponding to the 980nm / 545nm modes are as follows: .

Images