Up-conversion luminescence temperature sensor based on plasmon effect and preparation and application thereof

Abstract

The invention belongs to the technical field of temperature sensors, and particularly relates to an up-conversion luminescence temperature sensor based on a plasmon effect and preparation and application thereof. The core of the sensor provided by the invention is a composite structure formed by a gold nanorod array and Er < 3 + > and Yb < 3 + > co-doped NaYF4 up-conversion nanoparticles, and the gold nanorod array is prepared by adopting a two-way aluminum oxide template method and is regularly and orderly arranged in a hexagonal shape. Under the excitation of 980nm near-infrared light, the local surface plasmon resonance effect of the gold nanorods can significantly improve the up-conversion luminescence intensity and accelerate the thermal response rate of the sensor; the ratio type temperature sensing system is constructed by detecting the fluorescence intensity ratio of two emission bands of 515-535 nm and 535-555 nm, self-calibration accurate detection within the temperature range of 303-348 K can be achieved, and the sensor has the advantages of being uniform in structure, controllable in preparation, high in detection sensitivity, high in response speed and the like.

Description

Technical Field

[0001] This invention belongs to the field of temperature sensor technology, specifically relating to an upconversion luminescent temperature sensor based on the plasmon effect and its fabrication and application. Background Technology

[0002] Non-contact optical nanothermometers, with their high spatial resolution and non-invasive nature, have become a research hotspot in the field of precision temperature measurement. Among them, ratiometric optical thermometers based on the upconversion luminescence mechanism exhibit excellent performance, possessing not only high sensitivity but also the ability to be excited by low-energy near-infrared light, making them highly valuable for applications in bioimaging and micro-area temperature monitoring. Rare-earth ion-doped upconversion nanoparticles are a class of functional nanomaterials with long luminescence lifetimes, tunable emission colors, good photostability, large anti-Stokes shift, and weak autofluorescence, making them promising for precise measurements over a wide temperature range. However, this technology still faces several technical bottlenecks in practical applications, with thermal quenching being one of the core issues. As the temperature increases, the fluorescence intensity of upconversion nanoparticles significantly decreases, greatly limiting their application in high-temperature and variable-temperature environments.

[0003] Among commonly used upconversion ions, Er 3+ Two emission energy levels 2 H 11 / 2 → 4 I 15 / 2 and 4 S3 / 2→ 4 I 15 The / 2 energy level is sensitive to temperature changes and has therefore attracted much attention. The particle number distribution of these two energy levels follows a Boltzmann distribution and changes regularly with temperature. Based on the self-calibrating properties of their fluorescence intensity ratio (FIR), they possess the advantages of being unaffected by fluctuations in excitation source power and having excellent anti-interference capabilities. However, upconversion nanomaterials have inherent drawbacks: the absorption cross-section of rare earth ions is relatively small (typically below 10). -20 •cm 2 This results in weak luminescence intensity of the material, requiring a high-power laser as the excitation source to obtain sufficient detection signal, which limits its application in power-sensitive scenarios; at the same time, the material has low thermal conductivity and a slow rate of thermal equilibrium, making it difficult to meet the needs of modern cutting-edge fields for rapid temperature response.

[0004] To overcome these limitations, researchers have attempted to combine upconversion nanoparticles with plasmonic nanostructures, theoretically improving upconversion luminescence efficiency by leveraging the localized electromagnetic field enhancement effect generated by the plasmonic effect. However, existing composite structures still have shortcomings: most designs are limited by high scattering loss and low coupling efficiency, restricting practical sensing applications; the geometric parameters of metal nanostructures, such as shape, size, and particle spacing, play a decisive role in the plasmonic enhancement effect, and the control of these key parameters suffers from poor repeatability and difficulty in large-scale uniform fabrication; the fabrication of complex structures such as multilayer metal-dielectric-metal nanocavities also significantly increases process complexity and cost, resulting in product yields that are difficult to meet practical application requirements. Summary of the Invention

[0005] To address the problems in existing technologies regarding balancing enhancement effects with optical loss, precise control of structural parameters and ensuring fabrication repeatability, and balancing performance improvement with manufacturing costs, this invention provides an upconversion luminescence temperature sensor based on the plasmon effect. The sensor structure consists of a gold nanopillar array and Er... 3+ Yb 3+ The composite structure is formed by coupling co-doped NaYF4 upconversion nanoparticles, in which gold nanopillars are prepared using double-pass alumina as a template, exhibiting a highly uniform and periodically distributed hexagonal array. Under 980 nm near-infrared light excitation, this composite structure can significantly enhance the upconversion luminescence intensity and improve the temperature response rate through the local surface plasmon resonance effect of the gold nanopillars. By detecting the FIR of the two emission bands at 515-535 nm and 535-555 nm, a ratiometric temperature sensor can be constructed, enabling self-calibrated temperature detection in the range of 303-348 K.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides an upconversion luminescence temperature sensor based on the plasmon effect, wherein the core component of the upconversion luminescence temperature sensor is a gold nanopillar array and an Er 3+ Yb 3+ Co-doped NaYF4 upconversion nanoparticles (NaYF4:Yb 3+ Er 3+ The composite structure is formed by nanoparticles; the gold nanopillar array is prepared by the double-pass alumina template method and is arranged in a periodically ordered hexagonal pattern. Under 980nm near-infrared light excitation, the upconversion luminescence temperature sensor can achieve self-calibrated ratio-type temperature detection by measuring the integrated fluorescence intensity ratio (FIR) of the two emission bands at 515–535nm and 535–555nm.

[0007] The second aspect of the present invention also provides a method for fabricating the upconversion luminescence temperature sensor based on the plasmon effect described in the first aspect, the method comprising the following steps: S1. Gold nanopillar arrays were prepared by using a double-pass alumina (AAO) template and nanoimprinting technology: taking advantage of the structural characteristics of the double-pass alumina template, a gold film was first deposited in the nanopores to obtain a continuous gold nanostructure with a consistent thickness. Then, the alumina template was removed by etching with phosphoric acid solution to obtain a highly ordered gold nanopillar array. S2, Er 3+ Yb 3+ The upconversion luminescent temperature sensor is obtained by casting a dispersion of co-doped NaYF4 upconversion nanoparticles onto the surface of a gold nanopillar array and then allowing it to evaporate naturally to form a uniform composite structure.

[0008] Preferably, the Er 3+ Yb 3+ In co-doped NaYF4 upconversion nanoparticles, rare earth ions Yb 3+ With Er 3+ The molar ratio is 6-9:1-4.

[0009] Preferably, the dual-channel alumina template is a hexagonal periodic array with a pore size of 180-220 nm, a template thickness of 190-210 nm, and the channels are arranged in a hexagonal periodic pattern with a unit lattice side length of 430-470 nm.

[0010] Preferably, in S2, the thickness of the upconversion nanoparticle layer is 230–250 nm.

[0011] Preferably, in step S2, the natural evaporation time is 5-30 minutes.

[0012] Preferably, in S1, the concentration of the phosphoric acid solution is 0.3-0.8 mol / L, the etching temperature is 30-40℃, and the etching time is 1-4 hours.

[0013] Preferably, in S2, the Er 3+ Yb 3+ The dispersion of co-doped NaYF4 upconversion nanoparticles is Er 3+ Yb 3+ Cyclohexane dispersions of co-doped NaYF4 upconversion nanoparticles at concentrations of 15-30 mg / mL.

[0014] The third aspect of the present invention also provides the application of the upconversion luminescent temperature sensor based on the plasmon effect described in the first aspect in temperature detection.

[0015] Preferably, the specific method for temperature detection is as follows: (1) Within the temperature range of 303-348K, the fluorescence intensity ratio (FIR) of the two emission bands in the 515-535nm band and the 535-555nm band is calibrated as a function of temperature using the upconversion luminescence temperature sensor described in the first aspect. (2) The upconversion luminescence temperature sensor described in the first aspect is brought into contact with the object to be tested, and the FIR of the two emission bands is measured under the action of 980nm excitation light. The temperature of the object to be tested is inverted according to the relationship curve calibrated in step (1). The relationship between FIR and absolute temperature (T, unit: K) satisfies the equation: FIR=44.1exp (-1445.0 / T), and the applicable detection temperature range of this equation is 303–348K.

[0016] In the upconversion luminescence temperature sensor provided by this invention, the plasmon resonance effect of the gold nanopillar array can enhance the upconversion luminescence intensity and improve the sensor's thermal response rate, enabling it to reach thermal equilibrium within 70 ns after contact with a heat source. This ensures that the sensor's relative thermal sensitivity at 303 K is not less than 15.8 × 10⁻⁶. -3 ·K -1 .

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention provides an upconversion luminescence temperature sensor based on the plasmon effect. The core of this sensor is a gold nanopillar array and Er 3+ Yb 3+ A composite structure formed by co-doped NaYF4 upconversion nanoparticles, in which the gold nanopillar array is prepared using a double-pass alumina template method and exhibits a hexagonal periodically ordered arrangement, is utilized. Under 980 nm near-infrared light excitation, the localized surface plasmon resonance effect of the gold nanopillars in this sensor significantly enhances the upconversion luminescence intensity and accelerates the sensor's thermal response rate. By detecting the fluorescence intensity ratio between the two emission bands of 515-535 nm and 535-555 nm, a ratiometric temperature sensing system is constructed, enabling self-calibrated and accurate detection within a temperature range of 303-348 K. Furthermore, this sensor possesses advantages such as uniform structure, controllable fabrication, high detection sensitivity, and fast response speed, demonstrating significant practicality. Attached Figure Description

[0018] Figure 1 The front view (a) and top view (b) of the upconversion luminescent temperature sensor structure based on the plasmon effect in Example 1 are shown. Figure 2 The scanning electron microscope (SEM) image (a) and its surface scan (b) of the upconversion luminescent temperature sensor based on the plasmon effect in Example 1 are shown. Figure 3The fluorescence spectrum and enhancement amplitude of the upconversion luminescence temperature sensor based on the plasmon effect in Example 1 are shown in (a), and the test mechanism diagram of its surface plasmon-enhanced upconversion luminescence is shown in (b). Figure 4 The temperature-dependent fluorescence spectrum of the upconversion luminescence temperature sensor based on the plasmon effect in Example 1 is shown in (a), the relationship between its FIR and temperature is shown in (b), and the relationship between the logarithm of its FIR and the reciprocal of its temperature is shown in (c). Figure 5 The absolute thermal sensitivity (a) and relative thermal sensitivity (b) of the upconversion luminescent temperature sensor based on the plasmon effect in Example 1 are shown. Figure 6 The field strengths of pure UCNP and UCNP-gold nanopillar array composite structures are shown in the data. Figure 7 The time it takes for the upconversion luminescent temperature sensor based on the plasmon effect in Example 1 to reach thermal equilibrium at 350K. Detailed Implementation

[0019] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0020] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0021] Example 1: An upconversion luminescent temperature sensor based on plasmon effect and its fabrication The sensor structure consists of a gold nanopillar array and NaYF4:Yb 3+ Er 3+ The coupling is formed through the following steps: (1) A double-channel alumina (AAO) template with a pore size of 200 nm, a template thickness of 200 nm, a hexagonal periodic arrangement of channels, and a unit lattice side length of 450 nm was selected. Utilizing the structural characteristics of the AAO template, a gold film was deposited in the nanopores using a vertical deposition method, with the deposition rate controlled at 0.3 Å / s, to obtain a continuous gold nanostructure with uniform thickness. Subsequently, the gold nano sample was immersed in a 0.5 mol / L phosphoric acid solution and etched at 35 °C for 2 hours to completely remove the alumina template, ultimately obtaining a highly ordered array of gold nanopillars.

[0022] (2) Preparation of NaYF4:Yb by solvothermal method3+ Er 3+ The specific steps for upconversion nanoparticles are as follows: (a) Accurately weigh YCl3·6H2O (0.8 mmol), YbCl3·6H2O (0.18 mmol), and ErCl3·6H2O (0.02 mmol), add 5 mL of deionized water, and stir magnetically at room temperature until completely dissolved to form a clear rare earth ion mixed solution (YbCl3·6H2O). 3+ With Er 3+ The molar ratio is 9:1.

[0023] (b) Transfer the rare earth ion solution prepared in step (a) to a 100 mL three-necked flask and add 6 mL of oleic acid (OA, analytical grade). Purge air with nitrogen, stir and heat to 180 °C under nitrogen protection, and maintain for 30 minutes until the solution changes from an initial turbid state to a completely clear and transparent state, indicating that the dehydration process has been completed and a stable rare earth-oleic acid complex has been formed.

[0024] (c) Add 15 mL of 1-octadecene (ODE, 90%) to the above transparent solution and continue stirring at 180 °C for 30 minutes to ensure the reaction system is homogeneous and stable.

[0025] (d) After the reaction system was naturally cooled to 60 °C, a pre-prepared methanol solution (containing 2.5 mmol NaOH and 4.0 mmol NH4F, total volume 10 mL) was slowly injected through a syringe. After injection, the mixture was stirred vigorously at 60 °C for 30 minutes to ensure thorough mixing of the fluorine source and the rare earth complex. Subsequently, under continuous nitrogen protection and stirring, the reaction system was heated to 300 °C at a rate of 10 °C / min and refluxed at this temperature for 80 minutes to complete the crystallization and growth of the nanoparticles.

[0026] (e) After the reaction is complete, remove the heat source and allow the reaction system to cool naturally to room temperature. Add an equal volume of anhydrous ethanol to the product, and centrifuge at 10,000 rpm for 5 minutes to collect the precipitate. Wash the obtained precipitate three times alternately with cyclohexane and anhydrous ethanol to remove residual reactants and organic solvents. Finally, the purified NaYF4:Yb 3+ Er 3+ The nanoparticles were dispersed in 10 mL of cyclohexane to form a stable dispersion with a concentration of approximately 20 mg / mL, and then sealed and stored at 4°C for later use.

[0027] (3) Take 20 μL of Yb with a concentration of 20 mg / mL. 3+ With Er 3+ NaYF4:Yb with a molar ratio of 9:1 3+Er 3+ The cyclohexane dispersion of nanoparticles was uniformly drop-coated onto the surface of the gold nanopillar array substrate prepared in step (1) using a 10 μL pipette. A total of 20 μL of liquid was divided into 4 × 5 μL portions for drop-coating. The piston was pushed slowly and at a constant speed of 1 μL / s to avoid droplet spraying or the formation of large bubbles. After each 5 μL portion was added, a 10-second pause was allowed. The cyclohexane was allowed to spread and coalesce naturally on the substrate surface due to its low surface tension, ultimately forming a uniform liquid film with a thickness of 240 nm on the array surface.

[0028] (4) Place the sample containing the liquid film in a clean environment and let it stand for 5 minutes at room temperature (25°C) and relative humidity (<30%). After the cyclohexane has completely evaporated, a uniform nanocrystalline layer (i.e., upconversion nanoparticle layer) with a thickness of 240 nm is formed on the surface of the gold nanopillar array, and finally a structurally complete gold nanopillar array / NaYF4:Yb is obtained. 3+ Er 3+ Composite structure.

[0029] like Figure 1 As shown in (a) and (b), the area of ​​a single unit cell in the resulting composite structure is only 0.315 μm. 2 This micro / nano structure enables temperature detection to be confined to the micrometer scale, providing the necessary spatial resolution for micro-area temperature monitoring. Furthermore, the composite structure was characterized using field emission scanning electron microscopy, with results as follows: Figure 2 As shown in (a) and (b), NaYF4:Yb 3+ Er 3+ The nanoparticles are arranged in a dense monolayer, completely covering the surface and inter-pillar gaps of the gold nanopillar array, forming a continuous and dense composite interface. This helps ensure that the temperature signal originates from a uniform sensitive region. Moreover, energy dispersive spectroscopy analysis confirms that the elements are uniformly distributed and there is no obvious phase separation phenomenon, indicating that a plasmon-enhanced upconversion luminescence composite system with an ideal structure has been successfully constructed.

[0030] Example 2: Upconversion emission spectrum and energy level transition analysis of a composite sensor The upconversion luminescence spectrum of the composite structure obtained in Example 1 was tested. The specific method is as follows: an external excitation light source was used to continuously irradiate the plasmon effect upconversion luminescence temperature sensor with irradiation light of wavelength 980 nm and intensity 570 mW; 20 μL of NaYF4:Yb prepared in Example 1 was also used. 3+ Er 3+ A cyclohexane dispersion of nanoparticles was uniformly drop-coated onto the surface of a glass substrate. The sample was placed in a clean environment and allowed to stand at room temperature for 5 minutes. After the cyclohexane had completely evaporated naturally, a nanocrystalline layer was formed on the glass substrate. This was compared to the composite structure of NaYF4:Yb.3+ Er 3+ The upconversion emission spectrum, the test results are as follows Figure 3 As shown in (a).

[0031] NaYF4:Yb 3+ Er 3+ It exhibits a characteristic sharp green upconversion emission peak in the wavelength ranges of 515-535 nm and 535-555 nm, which is due to Er 3+ From thermally coupled energy levels 2 H 11 / 2 and 4 S 3 / 2 transition to ground state 4 I 15 / 2 At the 541nm peak, the luminescence intensity of the plasmon effect upconversion luminescence temperature sensor in Example 1 is NaYF4:Yb. 3+ Er 3+ Eight times larger than nanoparticles, by comparing upconversion emission spectra and analyzing peak positions, energy level transition maps can be obtained, such as... Figure 3 As shown in (b).

[0032] Example 3: Evaluation of fluorescence intensity temperature dependence and sensitivity of composite sensor The composite structure sample obtained in Example 1 was placed on an 800W precision temperature control platform (seller: Yuyue Electric, model: F108) and subjected to variable temperature testing at 5K intervals within the temperature range of 303–348K. A 980nm near-infrared laser (power fixed at 570mW) was used as the excitation source, and the emission spectrum was collected by a fluorescence spectrometer. Figure 4 The experimental results in (a) show that as the temperature increases, the 515-535nm (corresponding to Er) wavelength increases. 3+ of 2 H 11 / 2→ 4 I 15 / 2 transition) and 535-555nm (corresponding to 4 S3 / 2→ 4 I 15 The fluorescence intensity in both bands (e.g., the / 2 transition) shows a decreasing trend, but the decay rate of the former is significantly slower than that of the latter. This differential temperature response characteristic leads to a monotonically increasing FIR in both bands with increasing temperature, providing a physical basis for ratiometric temperature detection. The reason why the FIR increases with increasing temperature is that the green emission band corresponds to Er 3+ Ions from two thermally coupled energy levels 4 H 11 / 2 and 4 S 3 / 2 Leap to 4 I 15 / 2Ground state. Due to the small band gap between TCLs (approximately 800 cm⁻¹). -1 As the temperature rises, those in 4 S 3 / 2 Er of energy level 3+ Ions will gain energy, their population will redistribute, and some ions will jump to higher energy levels. 4 H 11 / 2 The result is that 4 H 11 / 2 The particle population at the energy level increases, while 4 S 3 / 2 The population at each energy level decreases accordingly. This process follows the Boltzmann distribution theory and can be expressed by the following formula: ; ; Where FIR is the fluorescence intensity ratio, I （515-535nm） It is the fluorescence intensity derived from high-energy-level transitions, I （535-555nm） It is the fluorescence intensity derived from low-energy level transitions; A is the fluorescence intensity derived from NaYF4:Yb. 3+ Er 3+ The determined proportionality constant, NaYF4:Yb prepared in step (2) of Example 1 3+ Er 3+ The proportionality constant is 44.1, a = lnA, and ΔE refers to... 4 H 11 / 2 and 4 S 3 / 2 The energy difference between two thermally coupled energy levels, k b Denotes the Boltzmann constant, b = ΔE / k b T represents absolute temperature.

[0033] like Figure 4 As shown in (b), formula (1) fits the trend of FIR with temperature very well. The fitting curve of the upconversion luminescence temperature sensor based on the plasmon effect in Example 1 is 44.1•exp(-1445.0 / T). Furthermore, Figure 4 (c) shows the relationship between the natural logarithm of the FIR and the reciprocal of the temperature, which is based on experimental data and can be well fitted by formula (2). The slope of the linear fitting curve of the upconversion luminescent temperature sensor based on the plasmon effect in Example 1 is -1445.0. Based on the linear behavior, the temperature can be accurately determined by the FIR with emission bands of 515-535nm and 535-555nm. Sensitivity is a key parameter for evaluating the performance of optical nanothermometers, and is usually expressed as relative sensitivity (S). r ) and absolute sensitivity (S a The specific definition is as follows: ; .

[0034] S r and S a It can be calculated using formulas (3) and (4), where FIR is the ratio of the integral intensities from the two thermally coupled energy levels, and ΔE is... 4 H 11 / 2 and 4 S 3 / The energy difference between two thermally coupled energy levels, where k represents the Boltzmann constant and T is the absolute temperature (unit: K). For example... Figure 5 As shown in (a), at 348 K, the relative sensitivity of the upconversion luminescent temperature sensor based on the plasmon effect in Example 1 is 8.2 × 10⁻⁶. -3 K -1 .like Figure 5 As shown in (b), at 303 K, the relative sensitivity of the upconversion luminescent temperature sensor based on the plasmon effect in Example 1 is 15.8 × 10⁻⁶. -3 K -1 .

[0035] Example 4: Analysis of the Local Field Strength Enhancement Effect of Composite Sensors Gold nanopillar arrays and NaYF4:Yb were compared using the FDTD (finite-difference time-domain) method. 3+ Er 3+ Composite structure, pure NaYF4:Yb 3+ Er 3+ Layered structure and NaYF4:Yb 3+ Er 3+ The local electromagnetic field enhancement effect of the composite structure with gold film (prepared using gold film as the substrate) was simulated and analyzed. Among them, the gold nanopillar array and NaYF4:Yb... 3+ Er 3+ In the composite structure, the short side length of the periodic unit is set to 450 nm, the long side length to 780 nm, and the height of the gold pillar to 200 nm. (NaYF4:Yb) 3+ Er 3+ The layer height is 240nm, and the glass thickness is 200nm. NaYF4:Yb 3+ Er 3+ In the layered structure, the layer height is 240 nm, and the glass thickness is 200 nm. NaYF4:Yb 3+ Er 3+ In the composite structure with gold film, NaYF4:Yb 3+ Er 3+ The layer height is 40nm and the gold film thickness is 200nm.

[0036] The results are as follows Figure 6 As shown, the gold nanopillar array and NaYF4:Yb 3+ Er 3+ Compared with the other two structures, the composite structure has a significant local field enhancement effect.

[0037] The enhancement mechanism can be attributed to the localized surface plasmon resonance excited by the gold nanopillar array. When the incident light wavelength matches the plasmon resonance peak of the nanopillar, a strong electromagnetic field localization and enhancement is generated at the top of the nanopillar, especially in the narrow gap region between adjacent nanopillars. This enhanced field interacts effectively with the upconversion nanoparticles covering it.

[0038] In contrast, the luminescence intensity of a pure upconversion nanoparticle layer is mainly limited by the inherently small absorption cross-section of rare earth ions. For the upconversion nanoparticle-planar gold film structure, the upconversion luminescence efficiency is suppressed due to reflection from the metal surface and potential non-radiative energy transfer. However, in the gold nanopillar array composite structure of Example 1, the upconversion nanoparticles are located in the high-field "hot spot" region formed by the gaps between the gold nanopillars. This localized field enhancement effect significantly improves the Yb concentration in the upconversion nanoparticles. 3+ The absorption efficiency of ions to 980 nm excited photons is thus enhanced, thereby increasing Er through energy transfer processes. 3 + Ion upconversion luminescence.

[0039] Therefore, the composite structure obtained in Embodiment 1 of the present invention can effectively enhance the luminescence intensity of upconversion through the plasmon resonance effect, providing an enhanced signal basis for high-sensitivity temperature detection.

[0040] Example 5: Temperature Response Rate Test of Composite Sensor This experiment tested the time it took for the upper surface of the plasmon effect upconversion luminescent temperature sensor obtained in Example 1 to reach thermal equilibrium when it was in contact with a 350K heat source at room temperature. The temperature evolution process could be tracked by solving the unsteady-state equation of thermal diffusion (Equation 5). ; In the formula, It is the density of the material. It is the specific heat capacity of the material. It is the rate of change of temperature over time. It is a heat conduction term. It is the thermal conductivity of the material. Spatial location The temperature corresponding to time t. This is the heat source / heat loss term. Among them, NaYF4:Yb 3+ Er 3+The specific heat capacity of NaYF4 is 720 J / (kg·K), and its thermal conductivity is 3.7 W / (m·K); the thermal conductivity of gold is 310 W / (m·K). Therefore, the thermal conductivity of the gold nanopillar array is approximately that of NaYF4:Yb. 3+ Er 3+ 85 times that of NaYF4:Yb, forming a high-speed heat conduction path, rapidly spreading heat laterally. 3+ Er 3+ Located near the hotspot of the gold pillar, the local temperature rise is large, and the density gradient-driven thermal diffusion shortens the equilibrium time to 70 ns, as shown in the example. Figure 7 As shown.

[0041] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A plasmonic-based upconversion luminescent temperature sensor, characterized in that, The core component of the upconversion luminescence temperature sensor is a gold nanopillar array and Er 3+ Yb 3+ The composite structure is formed by co-doping NaYF4 upconversion nanoparticles; the gold nanopillar array is prepared by the double-pass alumina template method and is arranged in a periodically ordered hexagonal pattern. Under 980nm near-infrared light excitation, the upconversion luminescence temperature sensor can achieve self-calibrated ratio-type temperature detection by measuring the integrated fluorescence intensity ratio (FIR) of the two emission bands at 515–535nm and 535–555nm.

2. The method for fabricating the upconversion luminescence temperature sensor based on the plasmon effect as described in claim 1, characterized in that, Includes the following steps: S1. Preparation of gold nanopillar arrays by double-pass alumina template and nanoimprint technology: Utilizing the structural characteristics of the double-pass alumina template, a gold film is first deposited in the nanopores to obtain a continuous and uniformly thick gold nanostructure. Then, the alumina template is removed by etching with phosphoric acid solution to obtain a highly ordered gold nanopillar array. S2, Er 3+ Yb 3+ The upconversion luminescent temperature sensor is obtained by casting a dispersion of co-doped NaYF4 upconversion nanoparticles onto the surface of a gold nanopillar array and then allowing it to evaporate naturally to form a uniform composite structure.

3. The method for fabricating an upconversion luminescent temperature sensor based on the plasmon effect according to claim 2, characterized in that, The Er 3+ Yb 3+ In co-doped NaYF4 upconversion nanoparticles, rare earth ions Yb 3+ With Er 3+ The molar ratio is 6-9:1-4.

4. The method for fabricating an upconversion luminescent temperature sensor based on plasmon effect according to claim 2, characterized in that, The dual-channel alumina template is a hexagonal periodic array with a pore size of 180-220 nm, a template thickness of 190-210 nm, and the channels are arranged in a hexagonal periodic pattern with a unit lattice side length of 430-470 nm.

5. The method for fabricating an upconversion luminescent temperature sensor based on plasmon effect according to claim 2, characterized in that, In S2, the thickness of the upconversion nanoparticle layer is 230–250 nm.

6. The method for fabricating an upconversion luminescent temperature sensor based on plasmon effect according to claim 2, characterized in that, In S2, the natural evaporation time is 5-30 minutes.

7. The method for fabricating an upconversion luminescent temperature sensor based on the plasmon effect according to claim 2, characterized in that, In S1, the concentration of the phosphoric acid solution is 0.3-0.8 mol / L, the etching temperature is 30-40℃, and the etching time is 1-4 hours.

8. The method for fabricating an upconversion luminescent temperature sensor based on plasmon effect according to claim 2, characterized in that, In S2, the Er 3+ Yb 3+ The dispersion of co-doped NaYF4 upconversion nanoparticles is Er 3+ Yb 3+ Cyclohexane dispersions of co-doped NaYF4 upconversion nanoparticles at concentrations of 15-30 mg / mL.

9. The application of the upconversion luminescent temperature sensor based on plasmon effect as described in claim 1 in temperature detection.

10. The application according to claim 9, characterized in that, The specific method for temperature detection is as follows: (1) Within the temperature range of 303–348K, the fluorescence intensity ratio (FIR) of the two emission bands in the 515–535nm and 535–555nm bands was calibrated as a function of temperature using the upconversion luminescence temperature sensor described in claim 1. (2) Contact the upconversion luminescence temperature sensor of claim 1 with the object to be tested, measure the FIR of the two emission bands under the action of 980nm excitation light, and invert the temperature of the object to be tested according to the relationship curve calibrated in step (1); The relationship between FIR and absolute temperature (T, unit: K) satisfies the equation: FIR=44.1exp (-1445.0 / T), and the applicable detection temperature range of this equation is 303–348K.

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