Near-infrared nanometer thermometer based on Tm < 3 + > doped nanoparticles and preparation and application thereof

Abstract

The invention discloses a near-infrared nanometer thermometer based on Tm < 3 + > doped nanoparticles and preparation and application thereof. The near-infrared nanometer thermometer is core / shell / shell nanoparticles of beta-NaGdF4: Er < 3 + >, Yb < 3 + > / NaGdF4: Tm < 3 + >, Yb < 3 + > / NaGdF4. According to the preparation method of the near-infrared nanometer thermometer, the reaction speed is high, temperature control is accurate, the thickness of the shell layer can be controlled, the obtained product is small in particle size and uniform in morphology and size, the near-infrared nanometer thermometer can be used as the near-infrared nanometer thermometer, and the near-infrared nanometer thermometer works in the near-infrared NIR-IIc wave band and has the advantages of high brightness, high stability and high sensitivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanometer temperature measurement, and in particular to a Tm 3+ Doped nanoparticle near-infrared nanothermometer and preparation and application thereof. BACKGROUND

[0002] In recent years, luminescent nanothermometry has shown an increasingly wide application prospect in microfluidics, microelectronics and biomedicine due to its remote and minimally invasive thermal sensing characteristics. As a typical spectral analysis technique, it realizes precise temperature measurement by monitoring the response change of the optical parameters of a specific probe with temperature in real time. It is particularly worth noting that among various luminescent nanothermometers, nanothermometers working in the near-infrared (NIR) band have unique advantages in the biomedical field: compared with ultraviolet / visible light, near-infrared light has lower light scattering and absorption characteristics, lower phototoxicity and stronger tissue penetration capability.

[0003] The near-infrared spectral region can generally be divided into multiple biological tissue optical transparent windows: NIR-I (750-900 nm), NIR-II (including NIR-IIx: 1400-1500 nm and NIR-IIc: 1700-1880 nm two sub-bands) and NIR-III (2000-2340 nm). It is worth noting that existing researches mainly focus on the development of NIR-I and NIR-IIx band nanothermometers, while in the longer wavelength NIR-IIc spectral region, the research on related nanothermometry materials still has obvious gaps. The reliability of the ratio type thermal sensing luminescent nanothermometer based on the calibration curve is problematic, especially the spectral distortion problem caused by the optical probe environment, which ultimately leads to insufficient temperature measurement sensitivity and actual reliability in the NIR spectral region.

[0004] Therefore, it is necessary to provide a nanothermometer with high brightness, high stability and high sensitivity in the NIR-IIc band. SUMMARY

[0005] Therefore, the present application provides a Tm 3+ Doped nanoparticle near-infrared nanothermometer and preparation and application thereof, which is used to solve the problem of how to provide a nanothermometer with high brightness, high stability and high sensitivity in the NIR-IIc band.

[0006] To achieve the above technical purpose, the present application adopts the following technical solutions: In a first aspect, the present application provides a Tm 3+ Doped nanoparticle near-infrared nanothermometer, which is a β-NaGdF4:Er 3+ ,Yb 3+ / NaGdF4: Tm 3+ ,Yb 3+ / NaGdF4: Tm

[0007] In a second aspect, the application provides a kind of based on Tm 3+ The preparation method of the near-infrared nanoparticle-doped nanometer thermometer includes the following steps: S1. Ln (TFA) 3 is used as the core precursor, mixed with sodium trifluoroacetate, capping agent and organic solvent containing oleylamine, degassed, and then nucleation reaction is carried out to obtain β-NaGdF4: Er 3+ ,Yb 3+ Core nanoparticles; S2. Ln' (TFA) 3 is used as the first shell precursor, mixed with sodium trifluoroacetate, capping agent and organic solvent after degassing, and then the core nanoparticles are added to carry out epitaxial growth reaction to obtain β-NaGdF4: Er 3+ ,Yb 3+ / NaGdF4: Tm 3+ ,Yb 3+ Core / shell nanoparticles; S3. Gd (TFA) 3 is used as the second shell precursor, mixed with sodium trifluoroacetate, capping agent and organic solvent after degassing, and then the core / shell nanoparticles are added to carry out epitaxial growth reaction to obtain the near-infrared nanometer thermometer; Wherein, Ln=Gd,Yb,Er; Ln'=Gd,Yb,Tm.

[0008] Preferably, in step S1, the preparation method of the core precursor Ln (TFA) 3 is: Ln2O3 is added to a mixture of trifluoroacetic acid and water, heated to reflux until the solution is clear, and the core precursor is obtained; the molar proportion of Yb2O3 in Ln2O3 is 20%-25%, and the molar proportion of Er2O3 is 2%-5%.

[0009] Preferably, in step S1, the nucleation reaction conditions are: under inert atmosphere, 280-290℃ for 1s, then 240-250℃ for 10-20min, and then the reaction is terminated by cooling to 50℃; Ln2O3 includes Gd2O3, Yb2O3 and Er2O3; and / or the molar ratio of sodium trifluoroacetate to Ln (TFA) 3 is 4-1:1.

[0010] Preferably, in step S2, the preparation method of the first shell precursor Ln' (TFA) 3 is: Ln'2O3 is added to a mixture of trifluoroacetic acid and water, heated to reflux until the solution is clear, and the first shell precursor is obtained; Ln'2O3 includes Gd2O3, Yb2O3 and Tm2O3; the molar proportion of Yb2O3 in Ln'2O3 is 20%-25%, and the molar proportion of Tm2O3 is 10%-15%.

[0011] Preferably, in step S2, the conditions of the epitaxial growth reaction are: 240-250℃ for 10-20min under inert atmosphere, and then the reaction is terminated by cooling to 50℃; and / or, the molar ratio of sodium trifluoroacetate to Ln'(TFA)3 is 4-1:1.

[0012] Preferably, Gd2O3 is added to the mixture of trifluoroacetic acid and water, and heated to reflux until the solution is clear, to obtain the second shell precursor; the molar ratio of Ln2O3, Ln'2O3 and Gd2O3 is 1:1:1-1.2.

[0013] Preferably, the conditions of the epitaxial growth reaction are: 240-250℃ for 10-20min under inert atmosphere, and then the reaction is terminated by cooling to 50℃; and / or, the molar ratio of sodium trifluoroacetate to Gd(TFA)3 is 4-1:1.

[0014] Preferably, the amount ratio of the core nanoparticles to Ln'(TFA)3 is 100-120mg:0.625mmol; and the amount ratio of the core / shell nanoparticles to Gd(TFA)3 is 120-130mg:0.625mmol.

[0015] In a third aspect, the application provides an application of the near-infrared nanometer thermometer in the NIR-IIc wave band.

[0016] The application has the following advantages: the preparation method of the near-infrared nanometer thermometer has fast reaction speed, precise temperature control, and controllable shell thickness, and the obtained product has small particle size and uniform morphology, which is beneficial to be used as a near-infrared nanometer thermometer; and the near-infrared nanometer thermometer works in the near-infrared NIR-IIc wave band, and has the advantages of high brightness, high stability and high sensitivity. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 For Tm 3+ Mechanism diagram of the doped near-infrared nanometer thermometer; Figure 2 XRD pattern of the core nanoparticles in Example 1; Figure 3 Electron microscope image and corresponding particle size distribution diagram of the core nanoparticles in Example 1; Figure 4 XRD pattern of the core / shell nanoparticles in Example 1; Figure 5 Electron microscope image and corresponding particle size distribution diagram of the core / shell nanoparticles in Example 1; Figure 6 XRD pattern of the core / shell / shell nanoparticles in Example 1; Figure 7 Transmission electron microscopy (TEM) images and corresponding particle size distribution of the core / shell / shell nanoparticles in Example 1; Figure 8 Tm in Example 1 3+ Near-infrared emission spectra of the doped core / shell / shell nanoparticles under 980 nm laser excitation; Figure 9 Tm in Example 1 3+ Temperature-dependent near-infrared emission spectra of the doped core / shell / shell nanoparticles under 980 nm laser excitation; Figure 10 Plot of the luminescence intensity ratio (LIR) as a function of temperature in Example 1; Figure 11 Plot of the relative thermal sensitivity as a function of temperature in Example 1; Figure 12 Tm in Comparative Example 1 3+ Near-infrared emission spectra of the doped core / shell / shell nanoparticles under 980 nm laser excitation; Figure 13 Tm in Comparative Example 2 3+ Near-infrared emission spectra of the doped core / shell / shell nanoparticles under 980 nm laser excitation; Figure 14 Plot of the relative thermal sensitivity as a function of temperature in Example 2. DETAILED DESCRIPTION

[0018] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0019] The present application provides a near-infrared nanothermometer based on Tm 3+ doped nanoparticles, which is a core / shell / shell nanoparticle of β-NaGdF4:Er 3+ ,Yb 3+ / NaGdF4:Tm 3+ ,Yb 3+ / NaGdF4.

[0020] In the present application, the near-infrared nanothermometer based on Tm 3+ doped nanoparticles has a core / shell / shell structure, the first shell layer coats the core layer, and the second shell layer coats the first shell layer, the core layer is β-NaGdF4:Er 3+ ,Yb 3+ , i.e. β-NaGdF4 doped with Er 3+ and Yb 3+ , and the middle shell layer is NaGdF4:Tm3+ ,Yb 3+ That is, doping with Tm 3+ and Yb 3+ The structure uses NaGdF4 as the outer shell. In this structure, the luminescent elements Er and Tm are separated, and a protective NaGdF4 layer is added to the outermost layer to ensure excellent Er and Tm emission intensity, thus enabling its use as a nano-thermometer. The specific luminescence process is as follows: Yb acts as a photosensitizer, absorbing 980 nm excitation light and then transferring the energy to Er, causing Er to emit 1550 nm near-infrared light. Simultaneously, Yb can also transfer the 980 nm light energy to Tm, causing Tm to emit 1850 nm light. Figure 1 As shown.

[0021] In some embodiments, based on Tm 3+ The near-infrared nanothermometer doped with nanoparticles is β-NaGdF4: Er 3+ (2mol%), Yb 3+ (20 mol%) / NaGdF4:Tm 3+ (10 mol%), Yb 3+ (20 mol%) / NaGdF4 core / shell / shell nanoparticles.

[0022] In this embodiment, based on Tm 3+ The core layer of the near-infrared nanothermometer doped with nanoparticles is β-NaGdF4:Er 3+ ,Yb 3+ And Er 3+ The doping ratio is 2 mmol%, Yb 3+ The doping ratio is 20 mmol%, i.e., Er 3+ Yb 3+ The molar amounts of Gd in the core layer respectively 3+ Er 3+ Yb 3+ 2% and 20% of the sum of molar amounts; the middle shell is NaGdF4:Tm 3+ ,Yb 3+ And Tm 3+ The doping ratio is 10 mmol%, Yb 3+ The doping ratio is 20 mmol%, i.e., Tm 3+ Yb 3+ The molar amounts of Gd in the middle shell respectively 3+ Er 3 + Yb 3+ 10% and 20% of the sum of molar amounts; the outer shell is NaGdF4.

[0023] This application provides a Tm-based3+ The preparation method of the near-infrared nanometer thermometer doped with nanoparticles comprises the following steps: S1. Ln(TFA)3 is mixed with sodium trifluoroacetate, a capping agent and an organic solvent containing oleylamine as a core precursor, degassed, and then a nucleation reaction is performed to obtain β-NaGdF4:Er 3+ ,Yb 3+ core nanoparticles; S2. Ln'(TFA)3 is mixed with sodium trifluoroacetate, a capping agent and an organic solvent as a first shell precursor, degassed, and then the core nanoparticles are added and an epitaxial growth reaction is performed to obtain β-NaGdF4:Er 3+ ,Yb 3+ / NaGdF4:Tm 3+ ,Yb 3+ core / shell nanoparticles; S3. Gd(TFA)3 is mixed with sodium trifluoroacetate, a capping agent and an organic solvent as a second shell precursor, degassed, and then the core / shell nanoparticles are added and an epitaxial growth reaction is performed to obtain the near-infrared nanometer thermometer; wherein, Ln=Gd, Yb, Er; Ln'=Gd, Yb, Tm.

[0024] In the present application, steps S1-S3 all involve the reaction equations as formula (1) and formula (2):

[0025] Formula (1) converts rare earth oxides that are insoluble in organic solvents into trifluoroacetates that are soluble and have good thermal stability, ensures uniform dispersion of reactants in the organic phase, and is the basis for realizing homogeneous reaction and high-quality nanocrystal synthesis. Formula (2) is the reaction of rare earth trifluoroacetate precursors with sodium trifluoroacetate to generate NaLnF4 crystals in high-temperature organic solvents. By using the above reactions, steps S2-S3 grow lattice-matched shell layers on the core particles that have been formed. Ln2O3 in the reaction equation refers to different things in different steps. In step S1, it is Ln2O3 (Ln=Gd, Yb, Er). In step S2, it is Ln'2O3 (Ln'=Gd, Yb, Tm). In step S3, it is Gd2O3.

[0026] Specifically, step S1 generates a large number of crystal nuclei instantaneously at high temperature, and then reduces the temperature to make the crystal nuclei grow slowly, thereby obtaining core nanoparticles with uniform size and good crystallinity. The core nanoparticles are doped with Er 3+ and Yb 3+ , which can absorb excitation light and produce a reference signal. Among them, Yb 3+ serves as a sensitizing agent to efficiently absorb 980 nm laser energy, and Er 3+ serves as an activator to receive Yb 3+After absorbing energy, the 1550 nm light emitted is temperature sensitive and serves as a temperature measurement signal; step S2 epitaxially grows NaGdF4:Tm on the surface of the core 3+ Yb 3+ As the first shell, the first shell serves to generate another temperature sensitive temperature measurement signal, wherein Yb 3+ continues to absorb energy as a sensitizer, Tm 3+ After receiving energy, the 1850 nm emission light intensity is highly sensitive to temperature and serves as a temperature measurement signal; the present application will Er 3+ and Tm 3+ (temperature signal source) are physically isolated in different layers, avoiding adverse energy cross relaxation between ions, so that both signals can be independently and strongly emitted; step S3 grows an inert NaGdF4 shell on the outermost layer. The rare earth ions on the surface of the core / shell nanoparticle are not saturated due to coordination, which is a "quenching center" for luminescence. The inert shell can effectively passivate these surface defects, isolate the luminescence center from the external environment, greatly enhance the luminescence intensity of the core and the first shell, and improve the signal-to-noise ratio and stability of temperature measurement.

[0027] In some embodiments, in step S1, the preparation method of the core precursor Ln(TFA)3 is as follows: Ln2O3 (Ln=Gd, Yb, Er) is added to a mixture of trifluoroacetic acid and water, heated to reflux until the solution is clear, and then dried to obtain the core precursor; Ln2O3 includes Gd2O3, Yb2O3 and Er2O3; in Ln2O3, the molar percentage of Yb2O3 is 20%-25%, the molar percentage of Er2O3 is 2%-5%, and the balance is Gd2O3.

[0028] In some embodiments, in the preparation process of the core precursor Ln(TFA)3, the volume ratio of trifluoroacetic acid to water is 1:1, and the heating reflux temperature is 90-95℃.

[0029] In some embodiments, in Ln2O3, the molar percentage of Yb2O3 is 20%, the molar percentage of Er2O3 is 2%, and the balance is Gd2O3.

[0030] In some embodiments, in step S1, the nucleation process is carried out by stepwise temperature control: in a nitrogen-protected microwave reactor, 280-290℃ for 1s, then 240-250℃ for 10-20min, and then the reaction is terminated by cooling to 50℃; and / or the molar ratio of sodium trifluoroacetate to Ln(TFA)3 is 4-1:1.

[0031] In some embodiments, in step S1, the capping agent includes oleic acid, and the organic solvent containing oleylamine is a mixture of oleylamine and 1-octadecene.

[0032] In some embodiments, in the nucleation process, the volume ratio of oleic acid, oleylamine and octadecene is 1:1:2, and the molar ratio of sodium ions in sodium trifluoroacetate to Ln ions in Ln(TFA)3 is 3:1.

[0033] In some embodiments, in step S2, the first shell precursor Ln'(TFA)3 is prepared by adding Ln'2O3 (Ln' = Gd, Yb, Tm) to a mixture of trifluoroacetic acid and water, heating to reflux until the solution is clear, and drying to obtain the first shell precursor. Ln'2O3 includes Gd2O3, Yb2O3 and Tm2O3. In Ln'2O3, the molar fraction of Yb2O3 is 20-25%, the molar fraction of Tm2O3 is 10-15%, and the remainder is Gd2O3.

[0034] In some embodiments, in the preparation of the first shell precursor Ln'(TFA)3, the heating to reflux temperature is 90-95°C, and the volume ratio of trifluoroacetic acid to water is 1:1.

[0035] In some embodiments, in step S2, the conditions for the epitaxial growth reaction are: in a microwave reactor under nitrogen protection, 240-250°C for 10-20 min, then cooled to 50°C to terminate the reaction; and / or, the molar ratio of sodium trifluoroacetate to Ln'(TFA)3 is 4-1:1.

[0036] In some embodiments, in step S2, the capping agent includes oleic acid; the organic solvent is 1-octadecene, and oleylamine is not included. In the process of shell growth, the addition of oleylamine will inhibit the growth of the shell.

[0037] In some embodiments, in step S3, Gd2O3 is added to a mixture of trifluoroacetic acid and water, heated to reflux until the solution is clear, and the second shell precursor is obtained. The molar ratio of Ln2O3, Ln'2O3 and Gd2O3 is 1:1:1-1.2.

[0038] In some embodiments, in step S3, the conditions for the epitaxial growth reaction are: in an inert atmosphere, 240-250°C for 10-20 min, then cooled to 50°C to terminate the reaction; and / or, the molar ratio of sodium trifluoroacetate to Gd(TFA)3 is 4-1:1.

[0039] In some embodiments, in step S3, the conditions for the epitaxial growth reaction are: the molar ratio of sodium trifluoroacetate to Gd(TFA)3 is 2:1.

[0040] In some embodiments, in step S3, the capping agent includes oleic acid; the organic solvent is 1-octadecene, and oleylamine is not included. In the process of shell growth, the addition of oleylamine will inhibit the growth of the shell.

[0041] In some embodiments, the ratio of core nanoparticles to Ln'(TFA)3 is 100-120 mg: 0.625 mmol; the ratio of core / shell nanoparticles to Gd(TFA)3 is 120-130 mg: 0.625 mmol.

[0042] In this embodiment, adding different amounts of core nanoparticles will result in synthesized core / shell particles with different shell thicknesses; a thinner shell will result in weaker luminescence intensity.

[0043] In some embodiments, the degassing conditions are as follows: the mixed raw materials are vacuum degassed at 110-120°C for 30-40 minutes.

[0044] This application provides an application of a near-infrared nanothermometer in the NIR-IIc band; specifically, it uses Tm 3+ Doped nanoparticles were dispersed in a toluene solution and irradiated with a 980 nm laser (laser power density: 6.7 W / cm²). 2 It can emit spectra at 1550 nm and 1850 nm in the near-infrared region, and this Tm 3+ Doped nanoparticles, used as near-infrared nanothermometers, exhibit very high relative thermal sensitivity, reaching 2.3% at 50℃. -1 .

[0045] Shifting the operating wavelength towards longer wavelengths can significantly alleviate spectral distortion caused by the optical probe environment. This application selects Er 3+ 1550 nm and Tm 3+ The 1850 nm emission is used as a signal pair. These two bands are located in the NIR-IIc window of biological tissues. In this window, the scattering, absorption and autofluorescence of light by biological tissues are significantly reduced, which gives the thermometer the ability to detect deep tissues and a high signal-to-noise ratio. It fundamentally solves the problems of penetration depth and background interference, thereby improving the relative thermal sensitivity.

[0046] The following specific embodiments further illustrate this solution.

[0047] Example 1 A Tm-based 3+ Near-infrared nanothermometer doped with nanoparticles, namely β-NaGdF4:Er 3+ (2 mol%), Yb 3+ (20 mol%) / NaGdF4:Tm 3+ (10 mol%), Yb 3+ (20 mol%) / NaGdF4 core / shell / shell nanoparticles.

[0048] Based on Tm 3+The method for preparing the near-infrared nanoparticle-doped nanothermometer is as follows: S1. 0.3125 mmol of Ln2O3 (0.244 mmol of Gd2O3, 0.0625 mmol of Yb2O3, and 0.00625 mmol of Er2O3) is placed in a 50 mL three-necked round-bottom flask, 10 mL of trifluoroacetic acid / water (v / v=1:1) mixed solvent is added, and the reaction is refluxed under the condition of 95 ℃ oil bath until the system is clear and transparent. After the reaction is completed, the product is dried at 60 ℃ in air for 12 h, and finally 0.625 mmol of Ln(TFA)3 core precursor is obtained. In the prepared Ln(TFA)3 precursor (0.625 mmol), 1.875 mmol of sodium trifluoroacetate is added according to the stoichiometric ratio (Na + :Ln 3+ =3:1), and 2.5 mL of oleic acid, 2.5 mL of oleylamine, and 5 mL of 1-octadecene are added. The above-mentioned mixed system is treated with vacuum degassing at 120 ℃ for 30 min to remove volatile impurities, and then the reaction liquid after degassing is transferred to a 35 mL microwave reaction tube, which is purged with nitrogen and sealed, and placed in a CEM Discovery SP microwave reactor. The reaction program is set as follows: rapidly heated to 280 ℃ for 1 s to initiate nucleation, then adjusted to 250 ℃ for 10 min, and finally cooled to 50 ℃ to terminate the reaction. The obtained product is purified by washing with 1:3 (v / v) n-hexane-ethanol mixed solution, centrifuged at 6595 g for 20 min, and then repeatedly purified by centrifugation with 1:3 (v / v) toluene-acetone system. The purified nanoparticles are dispersed in 5 mL of anhydrous toluene, and then resuspended in an ethanol-water (1:1, v / v) system to completely remove the by-product sodium fluoride. After centrifugal separation, the final product β-NaGdF4:Er 3+ (2 mol%), Yb 3+ (20 mol%) core nanoparticles are obtained. The XRD pattern of the core nanoparticles is shown in Figure 2 ; the electron microscope image and the corresponding particle size distribution graph of the core nanoparticles are shown in Figure 3 ; and the particle size distribution of the core nanoparticles is shown in S2. 0.3125 mmol of Ln'2O3 (0.219 mmol of Gd2O3, 0.0625 mmol of Yb2O3, 0.0313 mmol of Tm2O3) was placed in a 50 mL three-necked round-bottom flask, 10 mL trifluoroacetic acid / water (v / v = 1:1) mixed solvent was added, and the reaction was refluxed under 95 °C oil bath condition until the system was clear and transparent. After the reaction was completed, the product was dried at 60 °C in air for 12 h, and finally 0.625 mmol of Ln'(TFA)3 shell precursor was obtained. In the prepared Ln'(TFA)3 precursor (0.625 mmol), 1.875 mmol of sodium trifluoroacetate was added according to the stoichiometric ratio (Na+:Ln3+= 3:1), and 5 mL of oleic acid and 5 mL of 1-octadecene were added. The mixed system was vacuum degassed at 120 °C for 30 min to remove volatile impurities, and then the degassed reaction solution was transferred to a 35 mL microwave reaction tube and 100 mg of core particles were added. After nitrogen purging and sealing, it was placed in a CEM Discovery SP microwave reactor, and the reaction program was set as follows: rapid heating to 250 °C, constant temperature for 10 min, and finally cooling to 50 °C to terminate the reaction. The obtained product was purified by washing with 1:3 (v / v) n-hexane-ethanol mixed solution, 6595 g centrifugation for 20 min, and 1:3 (v / v) toluene-acetone system repeated centrifugal purification. The purified nanoparticles were dispersed in 5 mL of anhydrous toluene, and the nanoparticles were resuspended in ethanol-water (1:1, v / v) system to completely remove the by-product sodium fluoride. After centrifugal separation, the final product β-NaGdF4:Er 3+ (2 mol%),Yb 3+ (20 mol%) / NaGdF4:Tm 3+ (10 mol%),Yb 3+ (20 mol%) core / shell nanoparticles with an intermediate shell thickness of 3 nm; the XRD pattern of the core / shell nanoparticles is shown in Figure 4 ; the electron microscope image and the corresponding particle size distribution diagram of the core / shell nanoparticles are shown in Figure 5 ; S3. 0.3125 mmol of Gd2O3 was placed in a 50 mL three-necked round bottom flask, 10 mL trifluoroacetic acid / water (v / v=1:1) mixed solvent was added, and the reaction was refluxed under 95 °C oil bath until the system was clear and transparent. After the reaction was completed, the product was dried at 60 °C in air for 12 h, and finally 0.625 mmol of Gd(TFA)3shell precursor was obtained. In the prepared Gd(TFA)3precursor (0.625 mmol), 1.25 mmol of sodium trifluoroacetate was added according to the stoichiometric ratio (Na+: Gd3+= 2:1), and 5 mL of oleic acid and 5 mL of 1-octadecene were added. The mixed system was vacuum degassed at 120 °C for 30 min to remove volatile impurities, and then the degassed reaction solution was transferred to a 35 mL microwave reaction tube and 120 mg of core / shell particles were added. After nitrogen purging and sealing, it was placed in a CEM Discovery SP microwave reactor, and the reaction program was set as follows: rapid heating to 250 °C, constant temperature for 10 min, and finally cooling to 50 °C to terminate the reaction. The obtained product was purified by washing with 1:3 (v / v) n-hexane-ethanol mixed solution, centrifugation at 6595 g for 20 min, and then repeated with 1:3 (v / v) toluene-acetone system. The purified nanoparticles were dispersed in 5 mL of anhydrous toluene, and then resuspended in ethanol-water (1:1, v / v) system to completely remove the byproduct sodium fluoride. After centrifugal separation, β-NaGdF4: Er 3+ (2 mol%),Yb 3+ (20 mol%) / NaGdF4:Tm 3+ (10 mol%),Yb 3+ (20 mol%) / NaGdF4core / shell / shell nanoparticles, the outermost shell layer has a thickness of 3.4 nm, which is based on Tm 3+ doped nanoparticles near-infrared nanometer thermometer; the XRD pattern of the core / shell / shell nanoparticles is shown in Figure 6 ; the electron microscope image and the corresponding particle size distribution diagram of the core / shell / shell nanoparticles are shown in Figure 7 .

[0049] Example 2 A Tm 3+ doped nanoparticles near-infrared nanometer thermometer, which is β-NaGdF4: Er 3+ (2 mol%),Yb 3+ (20 mol%) / NaGdF4:Tm 3+ (20 mol%),Yb 3+ (20 mol%) / NaGdF4core / shell / shell nanoparticles.

[0050] Tm3+ The preparation method of the doped nanoparticle near-infrared nanometer thermometer is the same as that of Example 1, except that in step S2, 0.3125 mmol of Ln'2O3, 0.188 mmol of Gd2O3, 0.0625 mmol of Yb2O3, and 0.0625 mmol of Tm2O3.

[0051] Comparative Example 1 A Tm-based 3+ Doped nanoparticles are β-NaGdF4: Er 3+ (2 mol%), Yb 3+ (20 mol%), Tm 3+ (10 mol%) / NaGdF4 core-shell structure nanoparticles.

[0052] Tm-based 3+ The preparation method of the doped nanoparticles is as follows: 0.3125 mmol of Ln2O3 (0.213 mmol of Gd2O3, 0.0625 mmol of Yb2O3, 0.00625 mmol of Er2O3, and 0.0313 mmol of Tm2O3) was placed in a 50 mL three-necked round-bottom flask, 10 mL of trifluoroacetic acid / water (v / v=1:1) mixed solvent was added, and the system was refluxed under 95°C oil bath conditions until it was clear and transparent. After the reaction was completed, the product was dried at 60°C in air for 12 h, and finally 0.625 mmol of Ln(TFA)3 core precursor was obtained; In the prepared Ln(TFA)3 precursor (0.625 mmol), 1.875 mmol of sodium trifluoroacetate was added according to the stoichiometric ratio (Na+:Ln3+=3:1), and 2.5 mL of oleic acid, 2.5 mL of oleylamine, and 5 mL of 1-octadecene were added. The mixed system was vacuum degassed at 120°C for 30 minutes to remove volatile impurities, and then the degassed reaction solution was transferred to a 35 mL microwave reaction tube, purged with nitrogen and sealed, placed in a CEM Discovery SP microwave reactor, and the reaction program was set as follows: rapidly heated to 280°C for 1 second to initiate nucleation, then adjusted to 250°C for 10 minutes, and finally cooled to 50°C to terminate the reaction. The product was purified by washing with 1:3 (v / v) n-hexane-ethanol mixed solution, centrifuging at 6595 g for 20 minutes, and repeating the purification with 1:3 (v / v) toluene-acetone system; the purified nanoparticles were dispersed in 5 mL of anhydrous toluene, and to completely remove the byproduct sodium fluoride, the nanoparticles were resuspended in ethanol-water (1:1, v / v) system, and the final product β-NaGdF4: Er 3+(2 mol%), Yb 3+ (20 mol%), Tm 3+ (10 mol%) core nanoparticles. Gd2O3(0.3125 mmol) was placed in a 50 mL three-necked round bottom flask, 10 mL trifluoroacetic acid / water (v / v = 1 : 1) mixed solvent was added, and the reaction was refluxed at 95 °C under oil bath condition until the system was clear and transparent. After the reaction was completed, the product was dried at 60 °C in air for 12 h, and finally 0.625 mmol of Gd(TFA)3shell precursor was obtained. In the prepared Gd(TFA)3precursor, 1.875 mmol of sodium trifluoroacetate was added according to the stoichiometric ratio (Na+: Gd3+= 3: 1), and 5 mL of oleic acid and 5 mL of 1-octadecene were added. The mixed system was vacuum degassed at 120 °C for 30 min to remove volatile impurities, and then the degassed reaction solution was transferred to a 35 mL microwave reaction tube and 100 mg of core particles were added. After nitrogen purging and sealing, it was placed in a CEM Discovery SP microwave reactor, and the reaction program was set as follows: rapid heating to 250 °C, constant temperature for 10 min, and finally cooling to 50 °C to terminate the reaction. The product was purified by washing with 1:3 (v / v) n-hexane-ethanol mixed solution, and centrifuged at 6595 g for 20 min. The purified nanoparticles were dispersed in 5 mL of anhydrous toluene, and to completely remove the byproduct sodium fluoride, the nanoparticles were resuspended in ethanol-water (1:1, v / v) system, and the final product β-NaGdF4: Er 3+ (2 mol%), Yb 3+ (20 mol%), Tm 3+ (10 mol%) / NaGdF4core / shell nanoparticles.

[0053] Comparative Example 2 A Tm 3+ doped nanoparticle, which is β-NaGdF4: Er 3+ (2 mol%), Yb 3+ (20 mol%) / NaGdF4:Yb 3+ (20 mol%), Tm 3+ (10 mol%) core / shell structure nanoparticles.

[0054] A Tm 3+ doped nanoparticle was prepared as follows: The 0.3125 mmol of Ln203(wherein Gd203is 0.244 mmol, Yb203is 0.0625 mmol, Er203is 0.00625 mmol) was placed in a 50 mL three-necked round bottom flask, 10 mL trifluoroacetic acid / water (v / v = 1:1) mixed solvent was added, and the reaction was refluxed under 95 °C oil bath condition until the system was clear and transparent. After the reaction was completed, the product was dried at 60 °C in air for 12 h, and finally 0.625 mmol of Ln(TFA)3core precursor was obtained. In the prepared Ln(TFA)3precursor (0.625 mmol), 1.875 mmol of sodium trifluoroacetate was added according to the stoichiometric ratio (Na+:Ln3+= 3:1), and 2.5 mL of oleic acid, 2.5 mL of oleylamine and 5 mL of 1-octadecene were added. The mixed system was treated with vacuum degassing at 120 °C for 30 min to remove volatile impurities. Then the degassed reaction solution was transferred to a 35 mL microwave reaction tube, purged with nitrogen and sealed, and placed in a CEM Discovery SP microwave reactor. The reaction program was set as: rapidly heated to 280 °C for 1 s to initiate nucleation, then adjusted to 250 °C for 10 min, and finally cooled to 50 °C to terminate the reaction. Product purification: washed with 1:3 (v / v) n-hexane-ethanol mixed solution, 6595 g centrifuged for 20 min, and repeated with 1:3 (v / v) toluene-acetone system. The purified nanoparticles were dispersed in 5 mL of anhydrous toluene. To completely remove the by-product sodium fluoride, the nanoparticles were resuspended in ethanol-water (1:1, v / v) system, and the final product β-NaGdF4:Er 3+ (2 mol%),Yb 3+ (20 mol%) core nanoparticles; The 0.3125 mmol of Ln2O3 (0.219 mmol of Gd2O3, 0.0625 mmol of Yb2O3, and 0.0313 mmol of Tm2O3) was placed in a 50 mL three-necked round bottom flask, 10 mL trifluoroacetic acid / water (v / v=1:1) mixed solvent was added, and the reaction was refluxed under 95 ℃ oil bath condition until the system was clear and transparent. After the reaction was completed, the product was dried at 60 ℃ in air for 12 h, and finally 0.625 mmol of Ln(TFA)3 shell precursor was obtained; 1.875 mmol of sodium trifluoroacetate was added to the prepared Ln(TFA)3 precursor (0.625 mmol) according to the stoichiometric ratio (Na⁺:Ln³⁺=3:1), and 5 mL of oleic acid and 5 mL of 1-octadecene were added. The mixed system was vacuum degassed at 120 ℃ for 30 min to remove volatile impurities. Then the degassed reaction solution was transferred to a 35 mL microwave reaction tube and 100 mg of core particles were added, which was purged with nitrogen and sealed in a CEM Discovery SP microwave reactor. The reaction program was set as follows: rapid heating to 250 ℃, constant temperature for 10 min, and finally cooling to 50 ℃ to terminate the reaction. The product was purified by washing with 1:3 (v / v) n-hexane-ethanol mixed solution, centrifugation for 20 min at 6595 g, and repeated purification with 1:3 (v / v) toluene-acetone system; the purified nanoparticles were dispersed in 5 mL of anhydrous toluene, and the nanoparticles were resuspended in ethanol-water (1:1, v / v) system to completely remove the by-product sodium fluoride, and the final product β-NaGdF4:Er 3+ (2 mol%), Yb 3+ (20 mol%) / NaGdF4:Yb 3+ (20 mol%), Tm 3+ (10 mol%) core / shell nanoparticles.

[0055] Test and evaluation The products obtained in different examples and comparative examples were dispersed in toluene solution, and the effect was tested under 980 nm laser irradiation (laser power density: 6.7 W / cm 2 ).

[0056] Figure 8 The near-infrared emission spectrum of the Tm 3+ doped core / shell / shell nanoparticles under 980 nm laser excitation shows that the sample prepared in Example 1 can emit light in the NIR-IIc region, and the intensity of the emitted light is high; Figure 9 The near-infrared emission spectrum of the Tm 3+The temperature-dependent near-infrared emission spectrum of the doped core / shell / shell nanoparticles under 980 nm laser excitation shows that the emission spectrum of the sample prepared in Example 1 changes in emission intensity at different temperatures, and can be used as a nanometer thermometer; Figure 10 The graph of the change of the luminescence intensity ratio (LIR) with temperature in Example 1, i.e. the standard curve of the nanometer thermometer, shows that the sample prepared in Example 1 is placed in an environment with an unknown temperature, and the corresponding temperature can be measured by the obtained LIR value. Figure 11 The graph of the change of the relative thermal sensitivity with temperature in Example 1 shows that the thermometer prepared in Example 1 has high sensitivity, and in the near-infrared region, the sensitivity can reach 2.3%.

[0057] Figure 12 Tm in Comparative Example 1 3+ The near-infrared emission spectrum of the doped core / shell / shell nanoparticles under 980 nm laser excitation shows that in Comparative Example 1, all doping elements are placed in the same layer and are not separated, and only Er emission light can be detected, and the emission light of Tm disappears. However, the nanometer thermometer must have two different waveband emission lights, and therefore the material prepared in Comparative Example 1 does not have the condition to be used as a nanometer thermometer. Figure 13 Tm in Comparative Example 2 3+ The near-infrared emission spectrum of the doped core / shell nanoparticles under 980 nm laser excitation shows that in Comparative Example 2, there is no protection of the outermost shell, the overall luminescence intensity is weak, and the spectral noise is large. Figure 14 The graph of the change of the relative thermal sensitivity with temperature in Example 2 shows that Example 2 prepared a thermometer with the same structure as Example 1, but Tm 3+ The doping ratio is higher than that of Example 1, and the maximum sensitivity is 1.5%, which is not as good as Example 1.

[0058] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A Tm 3+ A near-infrared nanoparticle-doped nanothermometer, characterized in that, which is a core / shell / shell nanoparticle of β-NaGdF4:Er 3+ ,Yb 3+ / NaGdF4:Tm 3+ ,Yb 3+ / NaGdF4.

2. A Tm-based 3+ A method of preparing a near-infrared nanoparticle-doped nanothermometer, characterized by, The method comprises the following steps: S1. The Ln(TFA)3 is mixed with sodium trifluoroacetate, capping agent, organic solvent containing oleylamine as the core precursor, degassed, and then nucleated to obtain β-NaGdF4: Er 3+ ,Yb 3+ core nanoparticles; S2. After degassing the mixture of Ln'(TFA)3, sodium trifluoroacetate, capping agent and organic solvent, the core nanoparticles were added and epitaxial growth reaction was carried out to obtain β-NaGdF4:Er 3+ ,Yb 3+ / NaGdF4:Tm 3+ ,Yb 3+ core / shell nanoparticles; S3. The second shell precursor Gd(TFA)3 is mixed with sodium trifluoroacetate, a capping agent and an organic solvent, and degassed, and then the core / shell nanoparticles are added to perform an epitaxial growth reaction to obtain the near-infrared nanometer thermometer. In the formula, Ln = Gd, Yb, Er; and Ln' = Gd, Yb, Tm.

3. The preparation method according to claim 2, characterized in that, In step S1, the preparation method of the core precursor Ln(TFA)3 is as follows: Ln2O3 is added to a mixture of trifluoroacetic acid and water, and heated to reflux until the solution is clear, to obtain the core precursor; the Ln2O3 includes Gd2O3, Yb2O3 and Er2O3; in step S1, the nucleation reaction conditions are as follows: under an inert atmosphere, 280-290°C for 1s, then 240-250°C for 10-20min, and then the reaction is terminated by cooling to 50°C.

4. The production method according to claim 3, characterized by, In the Ln2O3, the molar proportion of Yb2O3 is 20%-25%, and the molar proportion of Er2O3 is 2%-5%; the molar ratio of sodium trifluoroacetate to Ln(TFA)3 is 4-1:

1.

5. The preparation method according to claim 2, characterized in that, In step S2, the preparation method of the first shell precursor Ln'(TFA)3 is as follows: Ln'2O3 is added to a mixture of trifluoroacetic acid and water, and heated to reflux until the solution is clear, to obtain the first shell precursor; the Ln'2O3 includes Gd2O3, Yb2O3 and Tm2O3; in step S2, the epitaxial growth reaction conditions are as follows: under an inert atmosphere, 240-250°C for 10-20min, and then the reaction is terminated by cooling to 50°C.

6. The production method according to claim 5, wherein In the Ln'2O3, the molar proportion of Yb2O3 is 20%-25%, and the molar proportion of Tm2O3 is 10%-15%; the molar ratio of sodium trifluoroacetate to Ln'(TFA)3 is 4-1:

1.

7. The preparation method according to claim 2, characterized in that, In step S3, Gd2O3 is added to a mixture of trifluoroacetic acid and water, and heated to reflux until the solution is clear, to obtain the second shell precursor.

8. The preparation method according to claim 7, characterized in that, In step S3, the epitaxial growth reaction conditions are as follows: under an inert atmosphere, 240-250°C for 10-20min, and then the reaction is terminated by cooling to 50°C; the molar ratio of sodium trifluoroacetate to Gd(TFA)3 is 4-1:

1.

9. The preparation method according to claim 2, characterized in that, The dosage ratio of the core nanoparticles to Ln'(TFA)3 is 100-120mg:0.625mmol; and the dosage ratio of the core / shell nanoparticles to Gd(TFA)3 is 120-130mg:0.625mmol.

10. The application of the near-infrared nanometer thermometer prepared by the method of any one of claims 2-9 in the NIR-IIc wave band.

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