CN114214069A - Core-shell double-doped nanoparticle material for improving sensitivity of non-contact temperature sensor and preparation method and application thereof - Google Patents
Core-shell double-doped nanoparticle material for improving sensitivity of non-contact temperature sensor and preparation method and application thereof Download PDFInfo
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- C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
- C09K11/7766—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals
- C09K11/7772—Halogenides
- C09K11/7773—Halogenides with alkali or alkaline earth metal
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- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
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Abstract
The invention discloses a core-shell double-doped nano particle material for improving the sensitivity of a non-contact temperature sensor and a preparation method and application thereof, and the preparation method comprises the following steps: (1) towards the medium containing Tm3+Adding oleic acid and octadecylene into the rare earth ion aqueous solution, and dissolving; (2) will contain NaOH and NH4Adding the methanol solution of F into the step (1) and then heating; (3) washing the nano particles generated in the step (2) and then dispersing the nano particles in cyclohexane; (4) to contain Er3+Adding oleic acid and octadecylene into the rare earth ion aqueous solution, and dissolving; (5) will contain NaOH and NH4Adding the methanol solution of F and the solution obtained in the step (3) into the step (4) and then heating; (6) and washing and drying the generated nano particles to obtain the nano particles with the core-shell structure. The invention also researches the optical temperature sensing characteristic of the thermocouple energy level, constructs a temperature measuring platform and evaluates the application of the temperature measuring platform in the optical fiber temperature sensorFeasibility and reliability.
Description
Technical Field
The invention belongs to the technical field of material preparation, and particularly relates to a core-shell double-doped nanoparticle material for improving the sensitivity of a non-contact temperature sensor, and a preparation method and application thereof.
Background
As one of the basic parameters of physics, temperature has become an important measure for scientific research work and industrial production. In a plurality of temperature measurement methods, the rare earth-based non-contact optical temperature sensor draws wide attention of people, and compared with the traditional temperature measurement method, the method is only related to the fluorescence characteristic of the material, so that the dependence of the traditional temperature measurement method on the environment can be effectively avoided. In particular, the optical thermometry based on the rare earth upconversion Fluorescence Intensity Ratio (FIR) has potential applications in metallurgy, catalysis, high temperature synthesis, material processing, biological cells and the like, and has wide applicability to malignant environments and fast moving objects, so that the thermometry is called as one of promising thermometry. Moreover, the rare earth elements have quite abundant energy level structures, and different rare earth luminescent ions are doped in a cladding and partition mode through the shell layer, so that high-sensitivity temperature measurement is realized.
In the aspect of FIR temperature measurement, the up-conversion fluorescence intensity ratio based on two thermocouple energy levels enables the FIR temperature measurement not to be influenced by factors such as spectrum loss and laser power intensity fluctuation, and the like, thereby realizing high-sensitivity temperature measurement. In the traditional temperature measuring material taking oxide as a matrix, the up-conversion fluorescence intensity is low, the temperature measuring sensitivity is low, and the current social requirements cannot be met, so that the research and development of a luminescent material with high sensitivity and high fluorescence intensity are urgently needed. Among the lanthanide series matrixes, fluoride has the advantages of low phonon energy, high transmittance, good stability and the like, and NaYF4Phonon energy is only 360cm-1Thus NaYF4Becomes one of the most desirable matrix materials. Tm is3+And Er3+As the rare earth element with higher luminous efficiency at present, the rare earth element is an ideal activator of the nano particles. Yb of3+With 980nm excitation light energyThe amount is matched, so that the nano particle is an ideal sensitizer. And 980nm lasers in the market are efficient and cheap, and reliable excitation energy is provided for the up-conversion nano materials. Thus, NaYF4:Yb3+/Tm3+And NaYF4:Yb3+/Er3+The nano particles are ideal up-conversion nano particles at present. However, it has certain limitations, such as many surface defects, large specific surface area, etc., which make the luminescence weak and the up-conversion efficiency not high. Therefore, it is necessary to develop a material which can improve both the luminous intensity and the sensitivity.
In the existing rare earth-based non-contact temperature measurement material, most material structures only have nuclear layers, and shell layer coating is not carried out, so that the surface defects are increased, the fluorescence intensity is weakened, and the temperature measurement sensitivity is not high.
Disclosure of Invention
In order to further solve the defects of the existing temperature measurement technology, the invention provides a core-shell double-doped nanoparticle material for improving the sensitivity of a non-contact temperature sensor and a preparation method and application thereof.
In order to achieve the purpose, the invention provides the following technical scheme:
the first technical scheme is as follows: a preparation method of a core-shell double-doped up-conversion nanoparticle material for improving the sensitivity of a non-contact temperature sensor comprises the following steps:
(1) lanthanide series rare earth ion Ln3+Magnetically stirring the aqueous solution, stirring and evaporating the water in the solution, adding oleic acid and octadecene after the water is completely evaporated, heating to 120 ℃ under the protection of argon and keeping for 30min to remove the water in OA and ODE, then raising the temperature to 150-160 ℃ and keeping for 60min, and cooling to room temperature; the Ln3+Is Y3+，Yb3+And Tm3+(ii) a Preferably 160 ℃;
(2) adding NaOH and NH into the solution obtained in the step (1)4Stirring the methanol solution of F, heating to 120 ℃ under the protection of argon (preferably 100 ℃), raising the temperature to 310 ℃ after the methanol is removed, keeping the temperature for 1-2h, and cooling to room temperature to obtain nanoparticles A; what is needed isNaOH and NH4The methanol solution of F is 5 mL;
(3) washing the obtained nano particle A and dissolving the nano particle A in cyclohexane to obtain the NaYF with a naked core structure4:Yb3+/Tm3+Nanoparticles;
(4) lanthanide series rare earth ion Ln3+Magnetically stirring the aqueous solution, stirring and evaporating the water in the solution, adding oleic acid and octadecene after the water is completely evaporated, heating to 120 ℃ under the protection of argon gas, keeping for 30min, then raising the temperature to 150-160 ℃ (preferably 160 ℃) and keeping for 60min, and cooling to room temperature; the Ln3+Is Y3+，Yb3+And Er3+；
(5) Will contain NaOH and NH4F methanol solution and the naked nuclear structure NaYF dispersed in the cyclohexane in the step (3)4:Yb3+/Tm3+Adding the nanoparticles into the solution obtained in the step (4), stirring, heating to 120 ℃ under the protection of argon (preferably 100 ℃), raising the temperature to 310 ℃ after the methanol and cyclohexane are removed, keeping the temperature for 1-2h, and cooling to room temperature to obtain nanoparticles B; the NaOH and NH4The methanol solution of F is 5 mL;
(6) washing the obtained nano particles B, and then drying for 24h in vacuum to obtain the NaYF with the core-shell structure4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+Nanoparticles. The drying temperature was 50 ℃.
Further, Y in the step (1)3+，Yb3+And Tm3+Are respectively selected from YCl3·6H2O、YbCl3·6H2O and TmCl3·6H2O; y in step (4)3+，Yb3+And Er3+Are respectively selected from YCl3·6H2O、YbCl3·6H2O and ErCl3·6H2O。
Further, said Y is3+，Yb3+And Tm3+In a molar ratio of 81.5:18: 0.5; said Y is3+，Yb3+And Er3+The molar ratio of (1) to (2) is (81.3-81.7) to (18) (0.3-0.7).
Further, the volume ratio of the oleic acid to the octadecane in the step (1) is (3.5-4): (7-8); and (4) the volume ratio of the oleic acid to the octadecene is (7-8) to (14-16).
Further, Y in the step (2)3+With NaOH and NH4The molar ratio of F is 1 (3.0-3.1) to (4.9-5.0); y in step (5)3+With NaOH and NH4The molar ratio of F is 1 (3.0-3.1) to (4.9-5.0), Y in this step3+The content is Y in the step (4)3+And (4) content.
Further, after methanol is removed cleanly in the step (2), the reaction temperature is raised to 300 ℃, and the reaction temperature is kept for 1.5 hours; and (4) after the methanol and the cyclohexane are removed, raising the reaction temperature to 300 ℃ and keeping the temperature for 1.5 h.
The washing steps in the step (3) and the step (6) comprise: adding excessive absolute ethyl alcohol into a reaction system, precipitating nanoparticles, carrying out centrifugal separation, removing supernatant, dispersing the obtained nanoparticles in cyclohexane, then adding absolute ethyl alcohol to wash a product, centrifuging, and repeating the steps for three times.
The second technical scheme is as follows: core-shell structure NaYF obtained by the preparation method4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+Up-converting the nanoparticles.
Further, the Er3+The doping molar amount of (A) is 0.3-0.7%.
The third technical scheme is as follows: NaYF with core-shell structure4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+Use of nanoparticles as probes.
Further, the core-shell structure NaYF4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+The method for detecting the temperature by using the nanoparticle probe comprises the following steps:
(1) NaYF with core-shell structure4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+The nano particle powder is adsorbed on the end face of the optical fiber and used as a temperature sensing probe of the sensor;
(2) excitation light from a 980nm laser propagates along the fiber to the wavelength division multiplexer;
(3) excited NaYF with core-shell structure4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+The nanoparticles produce up-converted fluorescence that will pass along the fiber through the wavelength division multiplexer and be received by the spectrometer analyzer for analysis;
(4) recording the up-conversion fluorescence intensity of 700nm and 646nm emission peaks of a probe under the real-time temperature change of 295K to 495K, taking standard temperature as a horizontal coordinate, and obtaining the fluorescence intensity by a formula
The measured temperature was calculated as the ordinate and the feasibility of the sensor was evaluated.
The non-contact core-shell double-doped up-conversion nanoparticle probe disclosed by the invention is high in sensitivity, can not cause a sample to generate heat or damage due to low-power near infrared light excitation, can be used in the field of accurate temperature measurement, and provides a new idea for a non-contact optical temperature sensor on the future nano scale.
Compared with the prior art, the invention has the beneficial effects that:
(1) the raw materials used in the invention are all inorganic salts, and the preparation process does not generate toxic gas and is environment-friendly. The prepared nano particles are orderly arranged, uniform in size distribution, free of agglomeration and approximately in a hexagonal structure in appearance; (2) the optical temperature sensor is prepared by core-shell double-doped nano particles, and the sensitivity of the sensor is very high and is obviously higher than that of the optical temperature sensor based on most Tm at present3+、Er3+The rare earth material of (1); (3) the invention can utilize the fluorescence intensity ratio of 700nm and 646nm of the emission peak, and the maximum absolute sensitivity and the maximum relative sensitivity of the invention are respectively as high as 0.0250K within the temperature range of 295K-495K-1And 2.155% K-1All have higher sensitivity than other thermocouple energy levels, which has potential application in optical temperature sensors; (4) NaYF adopting core-shell structure4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+The up-conversion nano particles are used as optical fiber temperature sensors, and the probe material is feasible and reliableAnd can be recycled.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1(a) is a diagram of a bare-core NaYF prepared in example 1 of the present invention4:Yb3+/Tm3+(18/0.5 mol%) and a naked nuclear structure NaYF4:Yb3+/Er3+(18/0.5 mol%) and NaYF with core-shell structure4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3 +/Er3+(18/xmol%) (x ═ 0.3/0.5/0.7%) XRD pattern of the nanoparticles; (b) is a partial XRD enlarged view of the crystal face of the nano particle (201);
FIG. 2 is the LR-TEM, HR-TEM and DLS images of the nanoparticle prepared in example 1 of the present invention, wherein (a), (b) and (c) are respectively the NaYF with naked core structure4:Yb3+/Tm3+(18/0.5 mol%) of LR-TEM, HR-TEM and DLS patterns, (d), (e) and (f) are core-shell structures NaYF4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+LR-TEM, HR-TEM and DLS images of (18/0.5 mol%) nanoparticles;
FIG. 3 is a TEM energy spectrum and a basal plane scan of the upconversion nanoparticles of the present invention;
FIG. 4(a) shows a naked core structure NaYF4:Yb3+/Tm3+(18/0.5 mol%) and a naked nuclear structure NaYF4:Yb3+/Er3+(18/0.5 mol%) and NaYF with core-shell structure4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/0.5 mol%) fluorescence spectrum of the nanoparticle (laser: 980nm, power density: 7.5W/cm)-2) (ii) a (b) A trend graph of the sum of the integrated intensities of the up-converted fluorescence of different samples; (c) a chromaticity diagram for different samples; (d) is a core-shell structureStructure NaYF4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/xmol%) (x ═ 0.3/0.5/0.7%) fluorescence spectrum of nanoparticles (laser: 980nm, power density: 7.5W/cm-2) (ii) a (e) Emission peak fluorescence integral intensity along with Er at 475nm and 538nm3+A variation trend graph of the doping concentration; (f) a chromaticity diagram for different samples; (g) is a core-shell structure NaYF under the excitation of 980nm4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+A log-log plot of up-conversion emission intensity versus laser power of (a); (h) is a core-shell structure NaYF under the excitation of 980nm laser4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+Nanoparticle up-conversion emission schematic; (i) is a schematic diagram of an energy transfer mechanism;
FIG. 5(a) shows a naked core structure NaYF4:Yb3+/Tm3+(18/0.5 mol%) and NaYF with core-shell structure4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/0.5 mol%) nanoparticle up-converted fluorescence decay curve at 475nm emission wavelength; (c) is a naked nuclear structure NaYF4:Yb3+/Er3+(18/0.5 mol%) and NaYF with core-shell structure4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/0.5 mol%) nanoparticle up-converted fluorescence decay curve at 538nm emission wavelength; (b) is of a core-shell structure NaYF4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/xmol%) (x ═ 0.3/0.5/0.7%) nanoparticles upconverted fluorescence decay curve at emission wavelength of 475 nm; (d) is of a core-shell structure NaYF4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/xmol%) (x ═ 0.3/0.5/0.7%) nanoparticles upconverted fluorescence decay curve at emission wavelength 538 nm;
FIG. 6(a) is NaYF with core-shell structure4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/0.5 mol%) nanoparticles at different temperaturesA fluorescence spectrum; (b) the change of the fluorescence intensity of 646nm and 700nm along with the temperature; (c) a linear fitting graph of fluorescence intensity ratio and reciprocal temperature is obtained; (d) is an absolute sensitivity and relative sensitivity curve of FIR temperature measurement (laser: 980nm, power density: 4W/cm)-2) (ii) a (e) Cycle repeats from 295K to 495K for FIR;
FIG. 7(a) is a NaYF core-shell structure4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/0.5 mol%) nanoparticles fluorescence intensity ratio at 520nm to 538nm plotted as a linear fit to the reciprocal temperature; (b) the absolute sensitivity and the relative sensitivity curve of the temperature measurement of the fluorescence intensity ratio of 520nm to 538nm are shown; (c) is of a core-shell structure NaYF4:Yb3 +/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/0.5 mol%) nanoparticles fluorescence intensity ratio at 700nm to 800nm versus reciprocal temperature as a linear fit; (d) the absolute sensitivity and the relative sensitivity curve of the temperature measurement of the fluorescence intensity ratio of 700nm to 800nm are shown;
FIG. 8(a) shows a naked core structure NaYF4:Yb3+/Tm3+(18/0.5 mol%) nanoparticles fluorescence intensity ratio at 700nm to 646nm versus reciprocal temperature; (b) the absolute sensitivity and relative sensitivity curve of the temperature measurement of the fluorescence intensity ratio of 700nm to 646 nm; (c) is a naked nuclear structure NaYF4:Yb3+/Er3+(18/0.5 mol%) nanoparticles fluorescence intensity ratio at 520nm to 538nm plotted as a linear fit to the reciprocal temperature; (d) the absolute sensitivity and relative sensitivity curve of the temperature measurement of the fluorescence intensity ratio of 520nm to 538 nm;
FIG. 9(a) is an experimental arrangement of a fiber optic temperature sensing system; (b) the measured temperature and the standard temperature displayed on the heater (the red line is a base line of the measured temperature and the standard temperature being equal); (c) the FIR values recorded at room temperature under different excitation powers; (d) is the FIR value recorded over 5 cycles between 295K and 495K.
Detailed Description
Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.
It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.
It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The specification and examples are exemplary only.
As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.
Example 1:
(1) preparation of NaYF with bare core structure4:Yb3+/Tm3+(18/0.5 mol%) nanoparticles
Weighing YCl with a molar ratio of 81.5:18:0.53·6H2O、YbCl3·6H2O and TmCl3·6H2Water soluble O with total rare earth ion content of 0.5mmolThe solution (1mL) was added to a 50mL flask, the water in the solution was evaporated by stirring with a magnetic stirrer, after the water was completely evaporated, 3.75mL of Oleic Acid (OA) was added followed by 7.5mL of 1-Octadecene (ODE), and the mixture was heated to 120 ℃ under argon for 30min to remove the water from OA and ODE. The temperature of the system is increased to 160 ℃, and the system is naturally cooled to the room temperature after reacting for 60 min. 5mL of a solution containing 1.25 mmole of NaOH and 2 mmole of NH were added dropwise with vigorous stirring4F, and stirring vigorously for 30min at room temperature, and then raising the temperature of the system to 100 ℃ under the condition of argon atmosphere to remove the methanol solution in the reaction mixture. And finally, after the methanol is completely removed, rapidly heating the temperature to 300 ℃ under the protection of argon, keeping the temperature for 1.5h, and stopping heating after the reaction is finished. After the reaction system is naturally cooled to room temperature, precipitating the product by using excessive absolute ethyl alcohol, washing the product for many times by using a mixed solution of the absolute ethyl alcohol and cyclohexane, and finally dispersing the reaction product in 4mL of cyclohexane to obtain the NaYF with a naked core structure4:Yb3+/Tm3+(18/0.5 mol%) nanoparticles.
(2) Preparing NaYF with core-shell structure4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/xmol%) (x ═ 0.3,0.5,0.7) nanoparticles
Will contain YCl3·6H2O、YbCl3·6H2O、ErCl3·6H2O water solution (1mL) with the total rare earth ion content of 0.5mmol in different proportions is added into a 50mL flask, water in the solution is stirred and evaporated under the action of a magnetic stirrer, 7.5mL of Oleic Acid (OA) and 15mL of 1-Octadecene (ODE) are added after the water is completely evaporated, and the mixture is heated to 120 ℃ under the protection of argon and is kept for 30min to remove the water in the OA and the ODE. The temperature of the system was raised to 160 ℃ and reacted for 60min until the solution became clear pale yellow, and then naturally cooled to room temperature. NaYF dispersed in 4mL of cyclohexane4:Yb3+/Tm3+The bare-core nanoparticles (the product prepared in step (1)) are added dropwise to the reaction solution. 5mL of a solution containing 1.25 mmole of NaOH and 2 mmole of NH were added dropwise to the reaction flask with vigorous stirring4And F, stirring vigorously for 30min at room temperature, and then raising the temperature of the system to 100 ℃ under the condition of introducing protective gas argon, so as to remove the methanol and cyclohexane solution in the reaction mixed liquid. And finally, after the methanol and the cyclohexane are removed, rapidly heating to 300 ℃ under the protection of argon, keeping the temperature for 1.5h, and stopping heating after the reaction is finished. After the reaction system is naturally cooled to room temperature, precipitating the product by using excessive absolute ethyl alcohol, washing the product for multiple times by using a mixed solution of the absolute ethyl alcohol and cyclohexane, and finally, drying the reaction product in vacuum at 50 ℃ for 24 hours to obtain the oil-soluble NaYF with the core-shell structure4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/xmol%) (x ═ 0.3,0.5,0.7) nanoparticles.
(3) Preparing NaYF with shell structure4:Yb3+/Er3+(18/0.5 mol%) nanoparticles
Weighing YCl with a molar ratio of 81.5:18:0.53·6H2O、YbCl3·6H2O and ErCl3·6H2An aqueous solution (1mL) containing 0.5mmol of O in terms of total rare earth ions is added into a 50mL flask, water in the solution is stirred and evaporated under the action of a magnetic stirrer, after the water is completely evaporated, 3.75mL of Oleic Acid (OA) and 7.5mL of 1-Octadecene (ODE) are added in sequence, and the mixture is heated to 120 ℃ under the protection of argon and is kept for 30min to remove the water in the OA and ODE. The temperature of the system is increased to 160 ℃, and the system is naturally cooled to the room temperature after reacting for 60 min. 5mL of a solution containing 1.25 mmole of NaOH and 2 mmole of NH were added dropwise with vigorous stirring4F, stirring vigorously for 30min at room temperature, and then raising the temperature of the system to 100 ℃ under the condition of introducing protective gas to remove the methanol solution in the reaction mixed liquid. And finally, after the methanol is completely removed, rapidly heating the temperature to 300 ℃ under the protection of argon, keeping the temperature for 1.5h, and stopping heating after the reaction is finished. After the reaction system is naturally cooled to room temperature, precipitating the product by using excessive absolute ethyl alcohol, washing the product for many times by using a mixed solution of the absolute ethyl alcohol and cyclohexane, and finally dispersing the reaction product in 4mL of cyclohexane to obtain the shell structure NaYF4:Yb3+/Er3+Nanoparticles.
(4) Core-shell double-doped up-conversion nanoparticle material for improving sensitivity of non-contact temperature sensor and application method of preparation method thereof
And (3) adsorbing the core-shell double-doped up-conversion nanoparticle powder in the step (2) on the end face of the optical fiber to be used as a temperature sensing probe of the sensor. The excitation light of the 980nm laser propagates along the fiber to the wavelength division multiplexer. The excited nanoparticles produce up-converted fluorescence that will pass along the fiber through the wavelength division multiplexer and be received by the spectrometer analyzer for analysis. The up-converted fluorescence intensities of the 700nm and 646nm emission peaks were recorded by the probe at real-time temperature changes of 295K to 495K. Establishing a temperature sensing relationship
The measured temperature is calculated and compared with a standard temperature to evaluate the application feasibility.
The nanoparticles prepared in example 1 were subjected to performance tests, and in fig. 1, (a) is an XRD pattern of the bare core-structured and core-shell-structured nanoparticles prepared in example 1-2, and (b) is a local XRD magnification of the crystal plane of the nanoparticle (201). As can be seen from the figure, the regions are doped with different Tm3+And Er3+Core-shell structure NaYF of content4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+After the nano particle samples are dried, the nano particle samples are subjected to X-ray diffraction (XRD) characterization, and the diffraction positions of all the samples can be well corresponding to the positions of all diffraction peaks in JDPDS standard cards NO:28-1192 through a characterization chart. Regionalized doping of Tm in core-shell3+And Er3+No impurity peak is generated. Does not destroy any original NaYF4Indicating that the NaYF is obtained as a pure beta phase4. To further prove that the obtained sample is a nanoparticle with a core-shell structure. As shown in fig. 1(b), the present invention selects an XRD pattern corresponding to the (201) crystal plane for local amplification, and according to the bragg equation, 2dsin θ is k λ, where d is the crystal plane spacing, θ is the diffraction angle, k is a positive integer, and λ is the wavelength of the X-ray. After the shell layer is coated, the diffraction angle theta corresponding to the (201) crystal face is deviated to a small angleAnd k and λ are not changed, so the value of d becomes larger, which indicates that the lattice expands. This is due to the fact that after coating the shell layer, the nanoparticles grow epitaxially in the core layer, resulting in lattice expansion. It is worth noting that the ion Er emits light along with the shell3+The diffraction angle is shifted towards a small angle, which indicates that with Er3+Is increased, the crystal lattice of the nano particle is further expanded, thereby causing a luminescence center Tm3+And Er3+The symmetry of the nearby crystal field is damaged, the transition probability of the space forbidden 4f-4f is improved, and the up-conversion luminescence is enhanced.
FIGS. 2(a), (d) are naked core structure NaYF4:Yb3+/Tm3+(18/0.5 mol%) and NaYF with core-shell structure4:Yb3+/Tm3 +(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/0.5 mol%) of the nanoparticle sample, as can be seen from the transmission electron microscope image, the nanoparticles, regardless of the bare core structure or the core-shell structure, are orderly arranged, have no agglomeration phenomenon, and have a morphology similar to a hexagonal structure. The morphology and homogeneity of the other samples is similar. The high resolution TEM image shows that the interplanar spacing of the bare core structure (b) and the core-shell structure (e) is 0.52nm, which corresponds to NaYF4The (110) crystal face shows that the synthesized nano-particle has good crystallinity, and the particle size and Zeta potential analysis instrument characterize NaYF4The particle size distribution of the nanoparticle sample is shown in the graphs (c) and (f), and the hydration kinetic diameter d of the sample can be seen1＝21.35±1.68nm，d2The particle size is smaller than 36.56 +/-4.26 nm. According to the Debye-Scheller formula,
the particle size of the nanoparticles can be calculated from the half-width of the strongest XRD diffraction peak, where K0.89 is the Scherrer constant, λ 0.154056nm is the wavelength of CuK α rays, BMIs the half-peak width of the diffraction peak, and θ is the bragg angle corresponding to the maximum diffraction peak. From this, the average crystal sizes were estimated to be 18 to 24nm and 33 to 42nm, respectively, further showing that they are consistent with the particle sizes measured by the particle size analyzer.
FIG. 3 is a TEM spectrum of up-converted nanoparticles, as is clear from the figureThe surface scanning distribution diagram of each doping element of F, Y, Yb, Tm and Er shows that the distribution of each element is very uniform, and the successful synthesis of the NaYF with the core-shell structure is shown again4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/0.5 mol%) of upconverting nanoparticles.
It can be seen from FIGS. 4(a) and 4(i) that the synthesized nanoparticles emit strong blue and green light, Tm3+The emission peak of (A) is mainly concentrated around 475nm, corresponding to1G4→3H6An energy level transition; er3+The emission peak of (A) is mainly concentrated around 538nm, corresponding to4S3/2→4I15/2And (4) energy level transition. According to the luminous intensity (I)UC) And 980nm laser power density (P)NIR) The relationship (c) of (a) to (b),
i.e. IUCAnd PNIRIs proportional to the power of n, wherein n represents the number of photons that the upconversion luminescence process needs to absorb 980nm near infrared light to emit one photon. Tm is3+And Er3+The dependence of the fluorescence intensity of the radiative transition on the power density is shown in FIG. 4(g), and it can be known from the linear fitting result,1G4→3H6、4S3/2→4I15/2the energy level transition n has values of 2.10 and 1.92, respectively, indicating that the energy level is Tm3+And Er3+The two-photon absorption process of (1). In order to realize multi-photon up-conversion emission, the invention selects 18% Yb3+And 0.5% Tm3+The nanoparticles of the inner core are synthesized, and then 18% Yb is selected according to the blue-green color ratio (figure 4c)3+And 0.5% Er3+The shell layer of the nanoparticle is synthesized. As can be seen from FIG. 4(b), the NaYF core-shell structure4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+The fluorescence intensity of the nano particle is higher than that of NaYF with a naked core structure4:Yb3+/Tm3+The strength is about 7 times, and the shell layer overcomes the surface defects of the core nano particles after the active shell is coated,so that the fluorescence intensity of the core-shell structure nano particles is stronger than that of the nano particles with a naked core structure. Also noteworthy is NaYF4:Yb3+/Er3+As a shell layer of a core-shell structure and a naked core structure NaYF4:Yb3+/Er3+In contrast, the surface defects were also present, but as can be seen from fig. 4(b), the fluorescence intensity was about 4 times stronger than that of the bare core structure. This is due to the naked nuclear structure NaYF4:Yb3+/Er3+Specific surface area of nano particle to shell NaYF4:Yb3+/Er3+The surface relative atomic number is increased, so that the coordination of surface atoms is insufficient, unsaturated bonds and dangling bonds are increased, the surface effect can cause large surface energy and activity of the nanoparticles, further cause electron transportation and structural change on the surface of the nanoparticles, and simultaneously cause the surface electron spinning phenomenon and the change of an electron energy spectrum, so that a nonlinear optical effect is generated, the nonradiative transition is increased, and the fluorescence intensity is reduced. This indicates that the core-shell structure NaYF4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+The nano particles have great application potential in the aspect of fluorescence imaging. NaYF with core-shell structure4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+The fluorescence spectrum of (18/xmol%) (x ═ 0.3/0.5/0.7%) nanoparticles is shown in fig. 4(d), and Tm can be seen in conjunction with fig. 4(e) and 4(h)3+The main emission peak of 475nm of the fluorescent intensity is along with Er3+Increased and decreased content of Er3+538nm fluorescence intensity of main emission peak along with Er3+Is increased and enhanced. This is due to the following Er3+The increase of the content promotes more electrons to be arranged in the two-photon transition4S3/2Energy level thereby greatly increasing4S3/2→4I15/2Radiation transition of Er 3+538 nm. In contrast, when the shell sensitizer ion Yb3+After 980nm exciting light is absorbed, most of the exciting light is transmitted to the shell luminous ion Er through energy transfer3+Further reducing the slave shell Yb3+To the nucleus layer Yb3+Resulting in a nuclear layer emitting light ion Tm3+Receive a sensitizer Yb3+The energy of the ion continues to decrease, resulting in Tm3+The main emission peak of (2) has a weakened fluorescence intensity at 475 nm. As can be seen from FIG. 4(f), Er3+When the doping concentration is 0.3 mol%, the sample emits blue light; when Er3+When the doping concentration is 0.7 mol%, the sample emits green light; however, when Er3+When the doping concentration is 0.5 mol%, the luminescent color of the sample is between blue and green, and the fluorescence intensity is relatively strong. Therefore, Er is selected in the invention3+The sample with the doping concentration of 0.5 mol% was further investigated for its temperature sensing performance.
As is clear from FIGS. 5(a) and (c), the core-shell structure nanoparticles all have a longer fluorescence lifetime than the bare core structure nanoparticles. Furthermore, as can be seen from FIG. 5(b), Er is associated with3+When the doping concentration is increased from 0.3 mol% to 0.7 mol%, the light-emitting center Tm is3+In1G4The lifetime of the energy level gradually decreased to 0.68ms at 0.5 mol%, whereas the luminescence center Er was seen from FIG. 5(d)3+In4S3/2The energy level lifetime gradually increases to 0.30ms at 0.5 mol%. According to the formula of the fluorescence lifetime,
wherein k isFThe decay constant, sigma k, representing the fluorescence emission rateiRepresenting the attenuation constants of the various radiative processes. For the blue emission peak at 475nm, due to Er3+Increase in doping amount, light emission center Tm3+The probability of radiative transition of (a) is reduced, so that the probability of non-radiative transition is increased, thereby enabling ∑ kiThe fluorescence lifetime becomes shorter as the ratio becomes larger. The opposite is true for the 538nm green emission peak, resulting in an increased fluorescence lifetime. Therefore, the invention selects NaYF with core-shell structure with moderate fluorescent life of 475nm and 538nm blue-green emission peaks4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/0.5 mol%) nanoparticles were investigated further.
Table 1 shows the sensitivity of different samples compared to each other, and table 2 shows the provenance of each material.
TABLE 1 comparison of sensitivity of different samples
Table 2 items 1-9 materials sources
| Item | Go out of |
| 1 | Inventive example 1 |
| 2 | Chem.Phys.Lett.,2016, |
| 3 | PhysicalChemistryChemicalPhysicsPccp,2014,16,22665-22676 |
| 4 | RSCAdvances,2016,55307-55311 |
| 5 | Opt.Mater.,2016 |
| 6 | OPTICALMATERIALS-AMSTERDAM-,2017 |
| 7 | Opt.Mater.,2016,58,449-453 |
| 8 | RSCAdvances,2014,4,6391-6396 |
| 9 | Ceram.Soc.,2015,98,2595-2600 |
The FIR temperature measurement technology needs to meet two conditions, one is that the fluorescence intensity of radiation transition is large enough to avoid the influence of optical noise on temperature measurement; the second is that the two energy levels have opposite downward transition trend of fluorescence intensity change, and the energy level difference between the two energy levels is about 200cm-1-2000cm-1In the meantime. As can be seen from FIGS. 6(a) and 6(b), the 646nm emission peak fluorescence intensity gradually decreased and the 700nm fluorescence intensity gradually increased with increasing temperature. And, as can be found by calculation, Tm3+The energy level difference of the 700nm and 646nm of the central wavelength of the luminescence is 1255cm-1And meets the requirement of thermal coupling energy level. This indicates that the core-shell structure NaYF4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+The nanoparticles can be used for sensitive temperature measurement. According to the formula of the fluorescence intensity ratio of the transition radiation of the electrons of the two thermally coupled energy levels from the high energy level to the low energy level,
wherein FIR is fluorescence intensity ratio, Delta E is energy corresponding to energy level difference, k is Boltzmann constant, and T is Kelvin temperature. A linear fit of the logarithm of the fluorescence intensity ratio of 700nm to 646nm to the reciprocal of the temperature gave good results as shown in FIG. 6 (c). The synthesized nano particles have unique advantages in temperature sensing. As can be seen from the mathematical definition of sensitivity,
SAfor absolute sensitivity, SRFor relative sensitivity, FIR is the fluorescence intensity ratio, Δ E is the energy corresponding to the energy level difference, k is the Boltzmann constant, and T is the Kelvin temperature. The fitted curve is shown in fig. 6(d), and it can be seen that in the temperature measurement range of 295K to 495K, the sample is applied to the absolute sensitivity curve and the relative sensitivity curve obtained by the FIR temperature measurement technology under the excitation of the 980nm laser, the absolute sensitivity curve monotonically increases with the increase of the temperature, and the relative sensitivity curve monotonically decreases with the increase of the temperature. NaYF with core-shell structure4:Yb3 +/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/0.5 mol%) nanoparticles3F3→3H6(700nm) with1G4→3F4Maximum absolute sensitivity of the (646nm) thermally coupled energy level pair reaches 0.0250K at 495K-1The maximum relative sensitivity reaches 2.155 percent K at 295K-1. FIG. 6(e) shows that the FIR cycle is very repeatable and that the FIR at each temperature point tends to stabilize, indicating that it responds sensitively at increasing and decreasing temperatures. On the other hand, as can be seen from Table 1, the material of the present invention is based on Tm in comparison with the current society3+And Er3+The absolute sensitivity of the material is high; on the other hand, as shown in fig. 7, different thermocouple energy levels are used for temperature measurement, and the sensitivity of temperature measurement is different, and it is worth mentioning that the ratio is2H11/2→4I15/2(520nm) with4S3/2→4I15/2The absolute sensitivity of the (538nm) energy level pair is an order of magnitude higher than3F3→3H6(700nm) with3H4→3H6The absolute sensitivity of the (800nm) energy level pair is two orders of magnitude higher, further proves that the 700nm and 646nm thermal coupling energy level pair has more application advantages, and has great application prospect in temperature measurement in modern production and life.
Referring to fig. 6(c) and fig. 8(a) and 8(c), the NaYF having the core-shell structure is shown4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+The fluorescent intensity ratio and the temperature reciprocal of the nano-particlesThe linear fitting degree is superior to that of the naked nuclear structure NaYF4:Yb3+/Tm3+And NaYF4:Yb3+/Er3+Nanoparticles. Comparing fig. 6(d) with fig. 8(b) and 8(d), it is clear that the absolute sensitivity of the core-shell structure nanoparticles is better than that of the bare core structure. With reference to FIG. 4(b), NaYF with core-shell structure4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+Nano particle ratio bare core structure NaYF4:Yb3+/Tm3+、NaYF4:Yb3+/Er3+The fluorescence intensity of the nano particles is about 7 times and 4 times stronger, which shows that the up-conversion fluorescence is enhanced, the absolute sensitivity of a sample is possibly improved, and the core-shell structure NaYF is shown4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+Nanoparticles are more suitable for optical temperature sensing.
The invention aims to research NaYF with a core-shell structure4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+The feasibility and reliability of the application of the nano-particles in the optical fiber temperature sensor construct a simple temperature measuring platform, as shown in fig. 9 (a). The nano particle powder is adsorbed on the end face of the optical fiber and used as a temperature sensing probe of the sensor. The excitation light comes from a 980nm laser and the light propagates along the fiber (yellow arrow) to a Wavelength Division Multiplexer (WDM). The excited nanoparticles produce up-converted fluorescence that will travel along the fiber (red arrow) through the WDM and be received by the spectrometer analyzer (OSA) for analysis. The feasibility of the sensor was evaluated by recording the up-converted fluorescence intensity of the emission peaks at 700nm and 646nm at real-time temperature changes of 295K to 495K for the probe. 9(b) by the formula
The measured temperature (where T is the kelvin temperature, FIR is the fluorescence intensity ratio,
Δ E is the energy corresponding to the energy level difference, K is the boltzmann constant), and compared to the standard temperature, mostly within 5K, indicating thatThe sensor temperature measurement is reliable. Thermodynamic statistics indicate that the population distributed on the thermocouple energy level satisfies the boltzmann distribution, which is temperature dependent and not low excitation power dependent. Thus, the effect of the excitation power on the FIR is as in fig. 9(c), and it is clear that the FIR is stable under low power excitation. To test the repeatability and recyclability of the platform material, the FIR was measured over several heating and cooling cycles of 295K and 495K, as shown in fig. 9(d), from which it can be seen that the numerical fluctuations are small. Therefore, the NaYF with the core-shell structure is adopted4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+The nano particles are used as the optical fiber temperature sensor, and the probe material is feasible, reliable and recyclable, so that a good foundation is provided for further application in the biomedical field and severe environment in the future.
With Er in example 13+The following study was conducted based on the doping molar amount of (A) 0.5%.
Example 2
The difference from example 1 is that NaYF is prepared4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/0.5 mol%) of nanoparticles in step (2), the temperature of the system is raised to 150 ℃, and the reaction is carried out for 60min and then the reaction product is naturally cooled to room temperature. The test was conducted in the same manner as in example 1, and it was found that the fluorescence intensity decreased at 150 ℃ and the absolute sensitivity decreased by 0.0024K-1。
Example 3
The difference from example 1 is that NaYF is prepared4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/0.5 mol%) of nanoparticles in step (2), the temperature of the system is raised to 160 ℃, and the reaction is carried out for 30min and then the reaction product is naturally cooled to room temperature. The test method is the same as that of example 1, and the results show that the fluorescence intensity is reduced and the absolute sensitivity is reduced by 0.0020K when the temperature is kept for 30min-1。
Example 4
The difference from example 1 is that NaYF is prepared4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/0.5 mol%) in step (2), after methanol and cyclohexane are removed, the temperature is rapidly raised to 290 ℃ under the protection of argon and kept for 1.5 h. The test method is the same as that of example 1, and the results show that the fluorescence intensity is reduced and the absolute sensitivity is reduced by 0.0028K at 290 DEG C-1。
Example 5
The difference from example 1 is that NaYF is prepared4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/0.5 mol%) nanoparticles in step (2), after methanol and cyclohexane were removed, the temperature was rapidly raised to 300 ℃ under argon protection and held for 1 h. The test was carried out in the same manner as in example 1, and it was found that the fluorescence intensity decreased and the absolute sensitivity decreased by 0.0032K when the temperature was maintained for 1 hour-1。
Comparative example 1
The difference from example 1 is that NaYF is prepared4:Yb3+/Tm3+(18/0.5mol％)@NaYF4:Yb3+/Er3+(18/0.5 mol%) nanoparticles in step (2), 5mL of a solution containing 1.25mmol of NaOH and 2mmol of NH was added dropwise to the reaction flask4After the methanol solution of F is added, the temperature of the system is raised to 100 ℃ directly under the condition of introducing protective gas argon, the system is not stirred for 30min before the temperature is raised, the test mode is the same as that of example 1, and the result shows that the absolute sensitivity is reduced by 0.0018K-1。
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included therein.
Claims (8)
1. A preparation method of a core-shell double-doped nanoparticle material for improving the sensitivity of a non-contact temperature sensor is characterized by comprising the following steps:
(1) lanthanide series rare earth ion Ln3+Magnetically stirring the aqueous solution, adding oleic acid and octadecene, and maintaining under argon atmosphereHeating to 120 ℃ under protection and keeping for 30min, then raising the temperature to 150-; the Ln3+Is Y3+，Yb3+And Tm3+；
(2) Adding NaOH and NH into the solution obtained in the step (1)4Stirring the methanol solution of F, heating to 120 ℃ under the protection of argon, raising the temperature to 310 ℃ after the methanol is removed, keeping the temperature for 1-2h, and cooling to room temperature to obtain nano particles A;
(3) washing the obtained nano particle A and dissolving the nano particle A in cyclohexane to obtain the NaYF with a naked core structure4:Yb3+/Tm3+Nanoparticles;
(4) lanthanide series rare earth ion Ln3+Magnetically stirring the aqueous solution, adding oleic acid and octadecene, heating to 120 ℃ under the protection of argon, keeping for 30min, then raising the temperature to 150-; the Ln3+Is Y3+，Yb3+And Er3+；
(5) Will contain NaOH and NH4F methanol solution and the naked nuclear structure NaYF dispersed in the cyclohexane in the step (3)4:Yb3+/Tm3+Adding the nanoparticles into the solution obtained in the step (4), stirring, heating to 120 ℃ under the protection of argon, raising the temperature to 310 ℃ after the methanol and the cyclohexane are removed, keeping the temperature for 1-2h, and cooling to room temperature to obtain nanoparticles B;
(6) washing the obtained nano particles B, and then drying for 24h in vacuum to obtain the NaYF with the core-shell structure4:Yb3+/Tm3+@NaYF4:Yb3+/Er3+Nanoparticles.
2. The method according to claim 1, wherein Y in the step (1)3+，Yb3+And Tm3+Are respectively selected from YCl3·6H2O、YbCl3·6H2O and TmCl3·6H2O; y in step (4)3+，Yb3+And Er3+Are respectively selected from YCl3·6H2O、YbCl3·6H2O and ErCl3·6H2O。
3. The method according to claim 2, wherein Y is3+，Yb3+And Tm3+In a molar ratio of 81.5:18: 0.5; said Y is3+，Yb3+And Er3+The molar ratio of (1) to (2) is (81.3-81.7) to (18) (0.3-0.7).
4. The method according to claim 1, wherein the volume ratio of oleic acid to octadecene in step (1) is (3.5-4): (7-8); and (4) the volume ratio of the oleic acid to the octadecene is (7-8) to (14-16).
5. The method according to claim 1, wherein Y in the step (2)3+With NaOH and NH4The molar ratio of F is 1 (3.0-3.1) to (4.9-5.0); y in step (5)3+With NaOH and NH4The molar ratio of F is 1 (3.0-3.1) to (4.9-5.0).
6. Core-shell structure NaYF obtained by the preparation method of any one of claims 1-54:Yb3+/Tm3+@NaYF4:Yb3+/Er3+Nanoparticles.
7. The NaYF core-shell structure of claim 64:Yb3+/Tm3+@NaYF4:Yb3+/Er3+Nanoparticles, characterized in that said Er3+The doping molar amount of (A) is 0.3-0.7%.
8. The NaYF with core-shell structure as claimed in claim 6 or 74:Yb3+/Tm3+@NaYF4:Yb3+/Er3+Use of nanoparticles as probes.
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| CN115595140A (en) * | 2022-09-30 | 2023-01-13 | 安徽师范大学（Cn） | Preparation method of DHCA (dehydroepiandrosterone) -modified upconversion luminescent nano material and method for detecting solution and cell temperature by using DHCA-modified upconversion luminescent nano material |
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| CN114656966A (en) * | 2022-04-15 | 2022-06-24 | 中国科学院福建物质结构研究所 | Four-layer core-shell structure nano material and preparation method and application thereof |
| CN115595140A (en) * | 2022-09-30 | 2023-01-13 | 安徽师范大学（Cn） | Preparation method of DHCA (dehydroepiandrosterone) -modified upconversion luminescent nano material and method for detecting solution and cell temperature by using DHCA-modified upconversion luminescent nano material |
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Application publication date: 20220322 Assignee: Guilin Fuankang Medical Products Co.,Ltd. Assignor: GUILIN University OF TECHNOLOGY Contract record no.: X2023980045093 Denomination of invention: A core-shell double doped nanoparticle material for improving the sensitivity of non-contact temperature sensors and its preparation method and application Granted publication date: 20230512 License type: Common License Record date: 20231030 |