Rare earth up-conversion nano fluorescent probe as well as preparation method and application thereof

Abstract

The invention relates to the technical field of fluorescent probes, in particular to a rare earth up-conversion nano fluorescent probe as well as a preparation method and application thereof. The rare earth up-conversion nano fluorescent probe provided by the invention is of a core-shell structure, NaYF4 nano particles doped with Yb < 3 + >, Tm < 3 + > and Er < 3 + > are taken as an inner core, and a NaTmF4 shell is coated outside the inner core. The rare earth up-conversion nano fluorescent probe provided by the invention can respond to the excitation wavelength of 1208 nm under the excitation of the excitation wavelengths of 980 nm and 1208 nm. Under the excitation of the excitation wavelength of 980 nm, laser with the wavelength of 1208 nm is used for exciting the rare earth up-conversion nano fluorescent probe, the peak value of the rare earth up-conversion nano fluorescent probe at the wavelength of 539.87 nm is increased along with the increase of the power of the excitation wavelength of 1208 nm, and then the good linear response of the rare earth up-conversion nano fluorescent probe to the excitation wavelength of 1208 nm is reflected. Therefore, the method can be applied to the detection of the power of a laser with the wavelength of 1208 nm.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorescent probes, and particularly relates to a rare earth upconversion nanophosphor and its preparation method and application. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or any form of implication that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] In recent years, the fluorescence imaging technology in the second near-infrared region (1000 - 1700 nm) has brought new opportunities to the field of biomedical detection. Compared with the traditional short-wavelength fluorescence imaging (400 - 1000 nm), the excitation and emission light in the second near-infrared region has lower scattering and absorption in biological tissues, greatly improving the imaging resolution and penetration depth. 1208 nm belongs to the typical excitation light wavelength in the second near-infrared region. However, there are few reports on fluorescent probe materials responsive to 1208 nm laser currently.

[0004] Currently, common fluorescent probe materials, such as organic dyes, fluorescent proteins, quantum dots, etc., generally use ultraviolet light or visible light as the excitation light source. Their fluorescence emission peaks are wide and asymmetric, with serious tailing, overlapping of various dye spectra, and very strong autofluorescence (background fluorescence) and scattered light in organisms, severely limiting the application of these fluorescent probe materials. In contrast, upconversion nanomaterials (UCNPs) use near-infrared light as the excitation light, causing less light damage, having lower autofluorescence background, stronger penetration depth, multi-wavelength luminescence, almost no toxicity, high fluorescence intensity and high stability in biological tissues. Summary of the Invention

[0005] In order to overcome the above problems, the present invention provides a rare earth upconversion nanophosphor and its preparation method and application.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] In the first aspect of the present invention, a rare earth upconversion nanophosphor is provided, which has a core-shell structure, and uses a NaYF nanoparticle doped with Yb 3+ , Tm 3+ and Er 3+ as the core, and coats a NaTmF shell on the core. 4 4

[0008] In the core, rare earth ions Yb 3+ are used as sensitizers, Er 3+ and Tm 3+As an activator, it is doped in the NaYF 4 matrix; using NaTmF 4 as the shell can protect the luminescence centers (rare earth ions) in the core from interference from the external environment; coating the NaTmF 4 shell layer makes the content of Tm 3+ in the material more, making the material emit stronger light and having a more obvious test effect on the power of a 1208 nm laser. This is because: under the co-excitation of 980 nm and 1208 nm lasers simultaneously, Yb 3+ absorbs 980 nm photons and transitions from the ground state 2 F 7 / 2 to the excited state 2 F 5 / 2 , and the excited state Yb 3+ transfers the energy to Er 3+ , enabling Er 3+ to transition from the ground state 4 I 15 / 2 to the excited state 4 I 11 / 2 ; Er 3+ transitions from 4 I 11 / 2 to 4 I 13 / 2 energy level through non-radiative transition, or transitions to a higher energy level by absorbing another 980 nm photon and then through non-radiative transition to 2 H 11 / 2 and 4 S 3 / 2 energy levels; the excited state Yb 3+ transfers the energy to Tm 3+ , enabling Tm 3+ to transition from the ground state 3 H 6 to 3 F 4 energy level. Moreover, Tm 3+ absorbs 1208 nm photons and transitions from the ground state 3 H 6 to the excited state 3 H 5 , and Tm 3+ transitions from 3 H 5 to 3 F 4 energy level through non-radiative transition; the excited state Tm 3+ transfers the energy to Er 3+ , enabling Er 3+ to transition from the ground state 4 I 15 / 2 to 4 I 9 / 2 energy level; Er 3+Relax to the 4 I 13 / 2 energy level; Er 3+ From 4 I 13 / 2 energy level transition back to 4 I 15 / 2 energy level will emit particles; The power of 980nm and 1208nm lasers directly affects the excitation efficiency of Yb 3+ 、Tm 3+ 、Er 3+ . It can be seen that the stronger the power of the 1208nm laser, the more particles of Er 3+ at the 4 I 13 / 2 energy level, and the stronger the particle intensity emitted by the transition of Er 3+ from 4 I 13 / 2 energy level to 4 I 15 / 2 energy level, and then the power of 1208nm is tested. Coating the NaTmF 4 shell layer makes the content of Tm 3+ in the material more, making the material emit stronger light and the test effect more obvious.

[0009] The rare earth upconversion nanophosphor emits green light at a wavelength of 530nm - 560nm when excited at an excitation wavelength of 980nm.

[0010] The second aspect of the present invention provides a preparation method of a rare earth upconversion nanophosphor, including the following steps:

[0011] (1) Add Y salt, Yb salt, Tm salt and Er salt to a mixed solution of oleic acid, oleylamine and 1-octadecene, and react to obtain a reaction solution containing a Y / Yb / Tm / Er-oleic acid complex precursor;

[0012] (2) Add NaOH and NH 4 F to the reaction solution containing the Y / Yb / Tm / Er-oleic acid complex precursor, and carry out a coprecipitation reaction to synthesize the core, namely NaYF 3+ 、Tm 3+ and Er 3+ doped nanoparticles; 4

[0013] (3) Add Tm salt to a mixed solution of oleic acid, oleylamine and 1-octadecene to obtain a reaction solution containing a Tm-oleic acid complex precursor;

[0014] (4) Add the NaYF 3+ 、Tm 3+ and Er 3+ doped with 4Nanoparticles, NaOH, and NH 4 F are added to the reaction solution containing the Tm-oleic acid complex precursor, and a rare earth upconversion nanophosphor is synthesized by coprecipitation reaction.

[0015] In the third aspect of the present invention, there is provided an application of the rare earth upconversion nanophosphor described in the first aspect in detecting the power of a laser with a detection wavelength of 1208 nm.

[0016] The rare earth upconversion nanophosphor provided by the present invention can achieve a response to an excitation wavelength of 1208 nm under excitation wavelengths of 980 nm and 1208 nm. Under excitation with an excitation wavelength of 980 nm, while simultaneously exciting the rare earth upconversion nanophosphor with a laser having a wavelength of 1208 nm, the peak value of the rare earth upconversion nanophosphor at 539.87 nm becomes stronger as the power of the excitation wavelength of 1208 nm increases, thereby reflecting the good response of the rare earth upconversion nanophosphor to the excitation wavelength of 1208 nm.

[0017] In the fourth aspect of the present invention, there is provided an application of the rare earth upconversion nanophosphor described in the first aspect in the field of temperature sensing.

[0018] The rare earth upconversion nanophosphor provided by the present invention is excited at an excitation wavelength of 980 nm, and this rare earth upconversion nanophosphor is heated (50 - 270 °C). The fluorescence intensity of the rare earth upconversion nanophosphor decreases as the temperature rises, thereby enabling the temperature measurement function.

[0019] In the fifth aspect of the present invention, there is provided an application of the rare earth upconversion nanophosphor described in the first aspect and carbon quantum dots as a dual anti-counterfeiting material.

[0020] The beneficial effects of the present invention are as follows:

[0021] (1) The present invention relates to the technical field of fluorescent probes, and specifically relates to a rare earth upconversion nanophosphor and its preparation method and application. The rare earth upconversion nanophosphor provided by the present invention has a core-shell structure, with NaYF 3+ doped with Yb 3+ , Tm 3+ , and Er 4 nanoparticles as the core, and a NaTmF 4 shell coated on the core. In the core, rare earth ions Yb 3+ are used as sensitizers, and Er 3+ and Tm 3+ are used as activators, and are doped in the NaYF 4 matrix; with NaTmF 4The outer shell can protect the luminescent centers (rare earth ions) in the core from interference from the external environment; coating with a NaTmF 4 shell layer increases the content of Tm 3+ in the material, making the material emit stronger light and having a more obvious effect on the power test of a 1208 nm laser. This is because: under the co-excitation of 980 nm and 1208 nm lasers simultaneously, Yb 3+ absorbs 980 nm photons and transitions from the ground state 2 F 7 / 2 to the excited state 2 F 5 / 2 . The excited Yb 3+ transfers its energy to Er 3+ , causing Er 3+ to transition from the ground state 4 I 15 / 2 to the excited state 4 I 11 / 2 . Er 3+ transitions from 4 I 11 / 2 to 4 I 13 / 2 through non-radiative transitions, or transitions to a higher energy level by absorbing another 980 nm photon and then relaxes to 2 H 11 / 2 and 4 S 3 / 2 through non-radiative transitions; the excited Yb 3+ transfers its energy to Tm 3+ , causing Tm 3+ to transition from the ground state 3 H 6 to 3 F 4 . Moreover, Tm 3 + absorbs 1208 nm photons and transitions from the ground state 3 H 6 to the excited state 3 H 5 . Tm 3+ transitions from 3 H 5 to 3 F 4 through non-radiative transitions; the excited Tm 3+ transfers its energy to Er 3+ , causing Er 3+ to transition from the ground state 4 I 15 / 2 to 4 I 9 / 2 . Er 3+ relaxes to 4 I 13 / 2Energy level; Er 3+ From 4 I 13 / 2 Energy level transition back to 4 I 15 / 2 Energy level will emit particles; The power of 980nm and 1208nm lasers directly affects the excitation efficiency of Yb 3+ , Tm 3+ , Er 3+ . It can be seen that the stronger the laser power of 1208nm, the more particles of Er 3+ in 4 I 13 / 2 energy level, and the stronger the particle intensity emitted by the transition of Er 3+ from 4 I 13 / 2 energy level to 4 I 15 / 2 energy level, thus testing the power of 1208nm. Coating the NaTmF 4 shell layer makes the content of Tm 3+ in the material more, making the material emit stronger light and the test effect more obvious.

[0022] (2) The rare earth upconversion nanophosphor provided by the present invention emits green light at a wavelength of 530nm - 560nm under the excitation of a 980nm excitation wavelength. At the same time, the rare earth upconversion nanophosphor provided by the present invention can respond to a 1208nm excitation wavelength under the excitation of 980nm and 1208nm excitation wavelengths. Under the excitation of a 980nm excitation wavelength, while exciting the rare earth upconversion nanophosphor with a laser of 1208nm wavelength, the peak value of the rare earth upconversion nanophosphor at 539.87nm becomes stronger as the power of the 1208nm excitation wavelength increases, thereby reflecting the good linear response of the rare earth upconversion nanophosphor to the 1208nm excitation wavelength. Therefore, it can be applied to detect the power of a laser with a wavelength of 1208nm.

[0023] (3) Under the excitation of a 980nm excitation wavelength, heating the rare earth upconversion nanophosphor provided by the present invention (50 - 270 °C), the fluorescence intensity of the rare earth upconversion nanophosphor decreases as the temperature rises, and thus the temperature measurement function can be realized.

[0024] (4) The rare earth upconversion nanophosphor provided by the present invention and carbon quantum dots form different luminescent colors under the excitation of different excitation wavelengths, and thus the two can be used as dual anti-counterfeiting materials. Description of the Drawings

[0025] The accompanying drawings of the specification, which form a part of the present invention, are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0026] Figure 1 For the core NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ X-ray diffraction (XRD) pattern;

[0027] Figure 2 For the core NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ Thermogravimetric (TGA) pattern;

[0028] Figure 3 Is the scanning electron microscope image of the rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 ;

[0029] Figure 4 Is the Fourier transform infrared absorption spectrum of the rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 ;

[0030] Figure 5 Rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 X-ray diffraction pattern;

[0031] Figure 6 For the rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 Emission spectrum at an excitation wavelength of 980 nm;

[0032] Figure 7 For the rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm3+ @NaTmF 4 Response to the 1208 nm excitation wavelength under the co-excitation of 980 nm and 1208 nm lasers;

[0033] Figure 8 For the rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 The fluorescence spectrum change curve with temperature for

[0034] Figure 9 is the transmission electron microscopy image of carbon quantum dots;

[0035] Figure 10 is the emission spectrum image of carbon quantum dots (diluted 1:64) under the 365 nm excitation wavelength;

[0036] Figure 11 is the emission spectrum image of carbon quantum dots (diluted 1:128) under the 365 nm excitation wavelength;

[0037] Figure 12 are the luminescent dolphin jumping through the hoop patterns under the excitation of lasers with different wavelengths. Figure a is the color picture under the simultaneous irradiation of 365 nm and 980 nm lasers, and Figure b is the black and white picture of Figure a. Detailed implementation manners

[0038] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0039] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0040] The first typical implementation manner of the present invention provides a rare earth upconversion nanophosphor, which has a core-shell structure. The core is a NaYF nanoparticle doped with Yb 3+ , Tm 3+ and Er 3+ , and the shell is a NaTmF 4 coating outside the core. 4 shell.

[0041] In the core, ytterbium ions (Yb) 3+ are used as sensitizers, erbium (Er) 3+ and thulium (Tm) 3+ are used as activators and are doped in NaYF 4 matrix; NaTmF 4 is used as the shell to protect the luminescence centers (rare earth ions) in the core from external environmental interference; coating with NaTmF 4 shell layer increases the content of Tm in the material, making the material emit stronger light and having a more obvious test effect on the power of a 1208 nm laser. This is because: under the co-excitation of 980 nm and 1208 nm lasers simultaneously, Yb 3+ absorbs 980 nm photons and transitions from the ground state 3+ F 2 to the excited state 7 / 2 F 2 ; the excited state Yb 5 / 2 transfers its energy to Er 3+ and makes Er 3+ transition from the ground state 3+ to the excited state 4 I 15 / 2 ; Er 4 I 11 / 2 transitions from 3+ I 4 to 11 / 2 through non-radiative transitions to 4 I 13 / 2 energy level, or transitions to a higher energy level by absorbing another 980 nm photon and then through non-radiative transitions to 2 H 11 / 2 and 4 S 3 / 2 energy levels; the excited state Yb 3+ transfers its energy to Tm 3+ and makes Tm 3+ transition from the ground state 3 H 6 to 3 F 4 energy level. Moreover, Tm 3+ absorbs 1208 nm photons and transitions from the ground state 3 H 6 to the excited state 3 H 5 ; Tm 3+ transitions from 3 H 5 to 3 F 4 energy level through non-radiative transitions; the excited state Tm 3+ transfers its energy to Er 3+ and makes Er 3+ transition from the ground state4 I 15 / 2 transitions to 4 I 9 / 2 energy level; Er 3+ relaxes to by non-radiative transition to 4 I 13 / 2 energy level; Er 3+ from 4 I 13 / 2 transitions back to the 4 I 15 / 2 energy level will emit particles; the power of the 980 nm and 1208 nm lasers directly affects the excitation efficiency of Yb 3+ , Tm 3+ , Er 3+ . Thus, the stronger the power of the 1208 nm laser, the more particles of Er 3+ in the 4 I 13 / 2 energy level, and the greater the intensity of the particles emitted when Er 3+ transitions from the 4 I 13 / 2 energy level to the 4 I 15 / 2 energy level, thereby testing the power of 1208 nm. Coating the NaTmF 4 shell layer increases the content of Tm 3+ in the material, making the material emit stronger light and the test effect more obvious.

[0042] The rare earth upconversion nanophosphor emits green light at a wavelength of 530 nm to 560 nm when excited by an excitation wavelength of 980 nm.

[0043] In one or more embodiments, the rare earth upconversion nanophosphor is in the shape of a cake, with a thickness of 35 to 40 nm and a width of 70 nm to 80 nm. The core is doped with Yb 3+ , Tm 3+ and Er 3+ NaYF 4 nanoparticles are in the shape of a cake, with a thickness of 20 nm to 40 nm and a width of 70 nm to 80 nm; the NaTmF 4 outer shell layer has a thickness of 6 to 8 nm.

[0044] In one or more embodiments, in the core, the molar ratio of Tm, Er, Yb, and Y is (0.4% to 0.6%): (0.4% to 0.6%): (16% to 20%): (78% to 84%), preferably 0.5%: 0.5%: 18%: 81%.

[0045] The second typical embodiment of the present invention provides a method for preparing the above rare earth upconversion nanophosphor, comprising the following steps:

[0046] (1) Add Y salt, Yb salt, Tm salt and Er salt into the mixed solution of oleic acid, oleylamine and 1-octadecene, and react to obtain a reaction solution containing Y / Yb / Tm / Er-oleic acid complex precursor;

[0047] (2) Add NaOH and NH 4 F into the reaction solution containing Y / Yb / Tm / Er-oleic acid complex precursor, and synthesize the core, i.e., NaYF 3+ doped with Yb 3+ , Tm 3+ and Er 4 nanoparticles by co-precipitation reaction;

[0048] (3) Add Tm salt into the mixed solution of oleic acid, oleylamine and 1-octadecene to obtain a reaction solution containing Tm-oleic acid complex precursor;

[0049] (4) Add the NaYF 3+ nanoparticles doped with Yb 3+ , Tm 3+ and Er 4 , NaOH and NH 4 F into the reaction solution containing Tm-oleic acid complex precursor, and synthesize rare earth upconversion nanophosphor by co-precipitation reaction.

[0050] In one or more embodiments, in step (1), the Y salt is selected from C 6 H 9 O 6 Y·4H 2 O;

[0051] The Yb salt is selected from C 6 H 17 O 10 Yb·4H 2 O;

[0052] The Tm salt is selected from C 6 H 11 O 7 Tm·4H 2 O;

[0053] The Er salt is selected from Er(OOCCH 3 ) 3 ·4H 2 O.

[0054] In one or more embodiments, in step (1), in the mixed solution of oleic acid, oleylamine and 1-octadecene, the volume ratio of oleic acid, oleylamine and 1-octadecene is (5-8):(4-6):(14-16), preferably 6:5:15.

[0055] In one or more embodiments, in step (1), the reaction temperature is 120 to 140 °C, preferably 130 °C, and the reaction time is 30 to 60 min.

[0056] In one or more embodiments, in step (1), the molar ratio of Y salt, Yb salt, Tm salt and Er salt is (78% - 84%):(16% - 20%):(0.4% - 0.6%):(0.4% - 0.6%), preferably 81%:18%:0.5%:0.5%.

[0057] In one or more embodiments, in step (1), the concentration of Y salt is 0.037 to 0.04 mol / L, preferably 0.0385 mol / L.

[0058] In one or more embodiments, in step (2), adding NaOH and NH 4 F to the reaction solution containing the Y / Yb / Tm / Er-oleic acid complex precursor to synthesize the core, i.e., the method for doping Yb 3+ , Tm 3+ and Er 3+ into NaYF 4 nanoparticles includes:

[0059] Dissolving NaOH and NH 4 F in methanol; adding the methanol solution of NaOH and NH 4 F to the reaction solution containing the Y / Yb / Tm / Er-oleic acid complex precursor, heating the mixed solution to 65 - 80 °C, and reacting for 30 - 40 min;

[0060] Then, under the protection of an inert gas, heating the mixed solution to 280 - 350 °C and maintaining for 1 - 2 h to obtain NaYF 3+ doped with Yb 3+ , Tm 3+ and Er 4 nanoparticles.

[0061] In one or more embodiments, in step (3), the Tm salt is selected from C 6 H 11 O 7 Tm·4H 2 O.

[0062] In one or more embodiments, in step (3), in the mixed solution of oleic acid, oleylamine and 1-octadecene, the volume ratio of oleic acid, oleylamine and 1-octadecene is (5 - 8):(4 - 6):(14 - 16), preferably 6:5:15.

[0063] In one or more embodiments, in step (3), the concentration of the Tm salt is 0.038 to 0.057 mol / L, preferably 0.048 mol / L.

[0064] In one or more embodiments, in step (4), the method for synthesizing a rare earth upconversion nanophosphor by coprecipitation reaction by adding NaYF 3+ doped with Yb 3+ , Tm 3+ and Er 4 nanoparticles, NaOH and NH 4 F into the reaction solution containing the Tm-oleic acid complex precursor includes:

[0065] S1. Dissolve the NaYF 3+ nanoparticles doped with Yb 3+ , Tm 3+ and Er 4 in cyclohexane, and centrifuge to collect the supernatant;

[0066] S2. Add the centrifuged supernatant to the reaction solution containing the Tm-oleic acid complex precursor, heat the mixed solution to 65 - 80 °C, and react for 30 - 40 min;

[0067] S3. Dissolve NaOH and NH 4 F in methanol; add the methanol solution of NaOH and NH 4 F to the mixed solution after heating in S2, raise the temperature of the reaction system to 65 - 80 °C, and react for 30 - 40 min;

[0068] S4. Under the protection of an inert gas, heat the mixed solution after the reaction in S3 to 280 - 350 °C, keep it for 1 - 2 h, and react to obtain the rare earth upconversion nanophosphor.

[0069] Preferably, in step S1, the centrifugation power is 4000 - 5000 r / min, preferably 4500 r / min, and the centrifugation time is 4 - 6 min, preferably 5 min.

[0070] The third typical embodiment of the present invention provides an application of the rare earth upconversion nanophosphor described in the first aspect in detecting the power of a laser with a detection wavelength of 1208 nm.

[0071] The rare earth upconversion nanophosphor provided by the present invention can respond to the excitation wavelength of 1208 nm under the excitation of excitation wavelengths of 980 nm and 1208 nm. Under the excitation of the excitation wavelength of 980 nm, while using a laser with a wavelength of 1208 nm to excite the rare earth upconversion nanophosphor, the peak value of the rare earth upconversion nanophosphor at 539.87 nm becomes stronger as the power of the excitation wavelength of 1208 nm increases, thereby reflecting the good response of the rare earth upconversion nanophosphor to the excitation wavelength of 1208 nm.

[0072] The fourth typical embodiment of the present invention provides the application of the rare earth upconversion nanophosphor described in the first aspect in the field of temperature sensing.

[0073] In one or more embodiments, the application is visual non-contact temperature monitoring of the interior of materials or devices.

[0074] The rare earth upconversion nanophosphor provided by the present invention is excited under the excitation wavelength of 980 nm, and this rare earth upconversion nanophosphor is heated (50 - 270 °C). The fluorescence intensity of the rare earth upconversion nanophosphor decreases as the temperature rises, and thus the temperature measurement function can be realized.

[0075] The fifth typical embodiment of the present invention provides the application of the rare earth upconversion nanophosphor described in the first aspect and carbon quantum dots as dual anti-counterfeiting materials.

[0076] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with specific embodiments.

[0077] Example 1

[0078] The core is NaYF 3+ doped with Yb 3+ , Tm 3+ and Er 4 nanoparticles (NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ ) preparation:

[0079] (1) Add C 6 H 9 O 6 Y·4H 2 O (0.81 mmol, 81%) and C 6 H 17 O 10 Yb·4H 2 O (0.18 mmol, 18%) and C 6H 11 O 7 Tm·4H 2 O (0.05 mmol, 0.5%), Er(OOCCH 3 ) 3 ·4H 2 O (0.05 mmol, 0.5%). Then add 6 mL of oleic acid, 5 mL of oleylamine, and 15 mL of 1-octadecene. While stirring, heat the mixture to 130 °C and form a light yellow transparent solution after 45 min. Subsequently, let the solution cool naturally to room temperature to obtain a reaction solution containing the Y / Yb / Tm / Er-oleic acid complex precursor.

[0080] (2) Dissolve 2.5 mmol of NaOH and 4 mmol of NH 4 F in 8 mL of methanol solution. Drop the reaction solution containing the Y / Yb / Tm / Er-oleic acid complex precursor obtained in step (1) into the methanol solution of NaOH and NH 4 F. The solution becomes turbid. Heat the mixed solution to 70 °C and keep it for 30 min to completely evaporate the methanol.

[0081] (3) Under nitrogen protection, heat the mixed solution obtained in step (2) to 300 °C in a closed environment and keep it for 1 h. Subsequently, let the solution cool naturally to room temperature.

[0082] (4) Add an excess of ethanol (40 mL) to the solution obtained from the reaction in step (3). Centrifuge at 10000 r / min for 10 min to obtain the core NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ . Then add 10 mL of cyclohexane. After dissolving the precipitate in cyclohexane, centrifuge at 4500 r / min for 5 min and collect the supernatant.

[0083] Figure 1 is the X-ray diffraction (XRD) pattern of the core NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ . It can be seen from Figure 2 that the XRD pattern of the core NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ is completely consistent with the standard card (PDF#16-0334), indicating that the prepared core NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ upconversion nanoparticles are in pure phase and without any impurities.

[0084] Figure 2 For the core NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ thermogravimetric (TGA) graph, as Figure 3 shown, the core NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ upconversion nanoparticles have the largest decline from 178.9 °C to 539.3 °C, which is 100.14% - 94.17%.

[0085] Example 2

[0086] Rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 Preparation:

[0087] (1) Add C 6 H 11 O 7 Tm·4H 2 O (1 mmol), then add 6 mL of oleic acid, 5 mL of oleylamine and 15 mL of 1-octadecene. While stirring, heat to 130 °C and form a light yellow transparent solution in 45 min. Then let the solution cool naturally to room temperature to obtain a reaction solution containing the Tm-oleic acid complex precursor.

[0088] (2) Drop the supernatant collected by centrifugation in step (4) of Example 1 into the reaction solution containing the Tm-oleic acid complex precursor. Heat the mixed solution to 70 °C and keep it for 30 min to completely volatilize cyclohexane. Then let the solution cool naturally to room temperature.

[0089] (3) Dissolve 2.5 mmol of NaOH and 4 mmol of NH 4 F in 8 mL of methanol solution. Drop the methanol solution of NaOH and NH 4 F into the solution obtained in step (2). The solution becomes turbid. Heat the mixed solution to 70 °C and keep it for 30 min to completely volatilize methanol.

[0090] (4) Heat the mixed solution obtained in step (3) to 300 °C and keep it for 1 h in a closed environment under nitrogen protection. Then let the solution cool naturally to room temperature.

[0091] (5) Add excessive ethanol (40 mL) to the solution obtained from the reaction in step (4), and centrifuge at 10000 r / min for 10 min to obtain the rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 . Then add 10 mL of cyclohexane. After dissolving the precipitate in cyclohexane, centrifuge at 4500 r / min for 5 min and collect the supernatant.

[0092] Figure 3 is the scanning electron microscopy image of the rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 . It can be seen from Figure 4 that the rare earth upconversion nanophosphor is in a disc shape, with a thickness of 35 - 40 nm and a width of 70 - 80 nm.

[0093] Figure 4 is the Fourier transform infrared absorption spectrum of the rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 . It can be known from Figure 5 that the absorption peaks of the surface functional groups of the rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 are 3402 cm -1 , 2925 cm -1 , 2862 cm -1 , 1566 cm -1 , 1463 cm -1 , 1108 cm -1 respectively. The absorption peak at 3402 cm -1 corresponds to the stretching vibration of the N - H bond. The absorption peak at 2925 cm -1 corresponds to the stretching vibration of the O - H bond in the hydroxyl group - OH. The absorption peak at 2862 cm -1 corresponds to the symmetric stretching vibration absorption peak of the C - H bond in the methyl group (-CH 3 ) and the methylene group (-CH 2 -). The absorption peak at 1463 cm -1 corresponds to the methyl group (-CH 3) asymmetric deformation vibration and methylene (-CH 2 -) scissoring vibration absorption peaks, the absorption peak at 1108 cm -1 corresponds to the stretching vibration of the C-O bond.

[0094] Figure 5 Rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 X-ray diffraction pattern of rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 The XRD pattern of rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 is a pure phase and has no impurities.

[0095] Figure 6 Emission spectrum of rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 under the excitation wavelength of 980 nm. When excited at the excitation wavelength of 980 nm, this rare earth upconversion nanophosphor emits green light at a wavelength of 530 nm to 560 nm (specifically 539.87 nm).

[0096] Example 3

[0097] Using rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 to conduct a dual-light response experiment. The specific steps are as follows:

[0098] To the rare earth upconversion nanophosphor NaYF prepared in Example 2 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4Add 10 mL of cyclohexane. After dissolving the precipitate in cyclohexane, centrifuge at 4500 r / min for 5 min and collect the supernatant.

[0099] Take 3 mL of the rare-earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 solution and place it in a standard cuvette with dimensions of 1 cm × 1 cm. Place the cuvette in a spectrometer;

[0100] Under the co-excitation of the excitation wavelengths of 980 nm and 1208 nm, fix the power of the 980-nm laser (specifically 1.5 W), change the power of the 1208-nm laser, and use the spectrometer to measure the fluorescence spectrum of the rare-earth upconversion nanophosphor NaYF 4 :Yb 3 + / Er 3+ / Tm 3+ @NaTmF 4 . Obtain the curve of the fluorescence spectrum changing with the power of the 1208-nm laser, and then the response of this material to the 1208-nm laser can be obtained.

[0101] The results are as Figure 7 shown. The power change range of the 1208-nm laser is 0 - 1.4 W, indicating that the rare-earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 has a good linear response to the excitation wavelength of 1208 nm under the co-excitation of the 980-nm and 1208-nm lasers.

[0102] Example 4

[0103] Application in temperature sensing:

[0104] (1) Wash and dry the rare-earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 material to obtain nanoparticle powder. Take an appropriate amount of the powder and put it into a solid temperature measurement device;

[0105] (2) Use a temperature-varying device to heat the powder. Under the irradiation of a 980-nm laser, use a spectrometer to measure the rare-earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er3+ / Tm 3+ @NaTmF 4 The fluorescence spectrum of @NaTmF was obtained, and the curve of the fluorescence spectrum varying with temperature was obtained. Furthermore, the temperature in the environment where the composite material is located can be calculated using this curve. The results are as Figure 8 shown. The excitation light source used is 980 nm, and the power is 1.4 W. The rare-earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 As the temperature (50 - 270 °C) increases, the fluorescence intensity decreases, thus realizing the temperature measurement function.

[0106] Example 5

[0107] Application of dual anti-counterfeiting:

[0108] (1) Preparation of carbon quantum dots (CDs):

[0109] Weigh 19.212 g of citric acid and add it to a beaker. Add 20 mL of water and stir evenly to obtain an aqueous solution of citric acid (0.1 mol). Then, drip 11.98 mL of an aqueous solution of ethanolamine (0.2 mol) into the aqueous solution of citric acid, and stir vigorously until the solution becomes clear.

[0110] Seal the above clear solution in a reaction kettle, heat it to 180 °C and keep it for 6 h, and then cool it naturally to room temperature to obtain a reddish-brown liquid.

[0111] Add the reddish-brown liquid into a dialysis bag with a molecular weight cut-off of 3500 for dialysis. Change the water every 4 h and dialyze for three days to remove excessive small-molecule products and impurities, obtaining a purified aqueous solution of CDs.

[0112] Take 0.1 mL of the aqueous solution of CDs and dilute it with 6.4 mL of water. Take 0.1 mL of the aqueous solution of CDs and dilute it with 12.8 mL of water.

[0113] Figure 9 is the transmission electron microscope image of the carbon quantum dots prepared in this example;

[0114] Figure 10 is the emission spectrum of the carbon quantum dots (1:64 dilution) prepared in this example under an excitation wavelength of 365 nm. The peak of the carbon quantum dots (1:64 dilution) is located at 570 nm under an excitation wavelength of 365 nm, emitting yellow light.

[0115] Figure 11It is the emission spectrum of the carbon quantum dots prepared in this embodiment (diluted 1:128) under an excitation wavelength of 365 nm. As shown in the figure, the peak of the carbon quantum dots (diluted 1:128) is located at 450 nm under an excitation wavelength of 365 nm, emitting blue light.

[0116] (2) Prepare appropriate cardboard, cover the hollow dolphin jumping through the hoop pattern of appropriate size, and apply the rare earth upconversion nanophosphor NaYF 4 :Yb 3+ / Er 3+ / Tm 3+ @NaTmF 4 cyclohexane solution on the dolphin's eyes; evenly apply the liquid of the carbon quantum dots prepared in this embodiment (diluted 1:64) on the dolphin's body; evenly apply the liquid of the carbon quantum dots prepared in this embodiment (diluted 1:128) on the hula hoop; remove the hollow dolphin jumping through the hoop pattern and wait for it to dry.

[0117] Excite with different wavelengths (365 nm, 980 nm) to obtain Figure 12 the glowing dolphin jumping through the hoop pattern. The excitation light sources used are 365 nm laser (power 4 W) and 980 nm laser (power 1.2 W). As a result, the rare earth upconversion nanophosphor and the carbon quantum dots form different glowing colors under the excitation of different excitation wavelengths respectively, and thus the two can be used as dual anti-counterfeiting materials.

[0118] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A rare earth upconversion nanofluorescent probe, characterized in that: It is a core-shell structure, doped with Yb 3+ 、Tm 3+ and Er 3 + The NaYF4 nanoparticles are the inner core, and the NaTmF4 outer shell is coated on the outer core.

2. The rare earth up-conversion nano fluorescent probe according to claim 1, characterized in that: The rare earth up-conversion nano fluorescent probe is in the shape of a round cake, with a thickness of 35 to 40 nm and a width of 70 to 80 nm; Alternatively, in the core, the molar ratio of Tm, Er, Yb and Y is (0.4% to 0.6%): (0.4% to 0.6%): (16% to 20%): (78% to 84%), preferably 0.5%: 0.5%: 18%: 81%.

3. The method for preparing the rare earth up-conversion nano fluorescent probe according to claim 1 or 2, characterized in that: The steps include: (1) adding Y salt, Yb salt, Tm salt and Er salt to a mixed solution of oleic acid, oleylamine and 1-octadecene to react and obtain a reaction solution containing a Y / Yb / Tm / Er-oleic acid complex precursor; (2) NaOH and NH4F were added to the reaction solution containing the Y / Yb / Tm / Er-oleic acid complex precursor, and the core was synthesized by coprecipitation reaction. 3+ 、Tm 3+ and Er 3+ NaYF4 nanoparticles; (3) adding Tm salt to a mixed solution of oleic acid, oleylamine and 1-octadecene to obtain a reaction solution containing a Tm-oleic acid complex precursor; (4) Yb 3+ 、Tm 3+ and Er 3+ NaYF4 nanoparticles, NaOH and NH4F are added to the reaction solution containing Tm-oleic acid complex precursor, and a co-precipitation reaction is performed to synthesize a rare earth up-conversion nano-fluorescent probe.

4. The preparation method according to claim 3, characterized in that: In step (1), the Y salt is selected from C6H9O6Y·4H2O; the Yb salt is selected from C6H 17 O 10 Yb·4H2O; the Tm salt is selected from C6H 11 O7Tm·4H2O; the Er salt is selected from Er(OOCCH3)3·4H2O; Or, in step (1), in the mixed solution of oleic acid, oleylamine and 1-octadecene, the volume ratio of oleic acid, oleylamine and 1-octadecene is (5-8):(4-6):(14-16), preferably 6:5:15; Or, in step (1), the reaction temperature is 120-140°C, preferably 130°C, and the reaction time is 30-60 min. Or, in step (1), the molar ratio of Y salt, Yb salt, Tm salt and Er salt is (78% to 84%): (16% to 20%): (0.4% to 0.6%): (0.4% to 0.6%), preferably 81%: 18%: 0.5%: 0.5%; Alternatively, in step (1), the concentration of the Y salt is 0.037 to 0.04 mol / L, preferably 0.0385 mol / L.

5. The preparation method according to claim 3, characterized in that: In step (2), NaOH and NH4F are added to the reaction solution containing the Y / Yb / Tm / Er-oleic acid complex precursor, and the coprecipitation reaction synthesizes the core doped with Yb 3+ 、Tm 3+ and Er 3+ The method of preparing NaYF4 nanoparticles includes: Dissolve NaOH and NH4F in methanol; add the methanol solution of NaOH and NH4F to the reaction solution containing the Y / Yb / Tm / Er-oleic acid complex precursor, heat the mixed solution to 65-80°C, and react for 30-40 minutes; The mixed solution is then heated to 280-350°C under the protection of an inert gas and maintained for 1-2 hours to obtain Yb-doped 3+ 、Tm 3+ and Er 3+ NaYF4 nanoparticles.

6. The preparation method according to claim 3, characterized in that: In step (3), the Tm salt is selected from C6H 11 O7Tm·4H2O; Or, in step (3), in the mixed solution of oleic acid, oleylamine and 1-octadecene, the volume ratio of oleic acid, oleylamine and 1-octadecene is (5-8):(4-6):(14-16), preferably 6:5:15; Alternatively, in step (3), the concentration of the Tm salt is 0.038 to 0.057 mol / L, preferably 0.048 mol / L.

7. The preparation method according to claim 3, characterized in that: In step (4), Yb 3+ 、Tm 3+ and Er 3+ The method for synthesizing a rare earth up-conversion nano fluorescent probe by coprecipitation reaction of adding NaYF4 nanoparticles, NaOH and NH4F to a reaction solution containing a Tm-oleic acid complex precursor comprises: S1, doped with Yb 3+ 、Tm 3+ and Er 3+ The NaYF4 nanoparticles were dissolved in cyclohexane and the supernatant was collected by centrifugation; S2, adding the collected supernatant from the centrifugation to the reaction solution containing the Tm-oleic acid complex precursor, heating the mixed solution to 65-80° C., and reacting for 30-40 minutes; S3, dissolving NaOH and NH4F in methanol; adding the methanol solution of NaOH and NH4F to the mixed solution heated in S2, heating the reaction system to 65-80°C, and reacting for 30-40 minutes; S4, heating the mixed solution after the reaction in S3 to 280-350° C. under the protection of an inert gas, maintaining the temperature for 1-2 hours, and reacting to obtain a rare earth up-conversion nano fluorescent probe; Preferably, in step S1, the centrifugal power is 4000-5000 r / min, preferably 4500 r / min, and the centrifugal time is 4-6 min, preferably 5 min.

8. Use of the rare earth up-conversion nano fluorescent probe according to claim 1 or 2 in detecting the power of a laser with a wavelength of 1208 nm.

9. Application of the rare earth up-conversion nano fluorescent probe according to claim 1 or 2 in the field of temperature sensing; Preferably, the application is visual non-contact temperature monitoring inside a material or a device.

10. Use of the rare earth up-conversion nano fluorescent probe and carbon quantum dots as claimed in claim 1 or 2 as dual anti-counterfeiting materials.

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