A degradable nacef4-based up / down conversion luminescent material, a preparation method and application thereof

Abstract

The application discloses a degradable NaCeF4-based up / down conversion luminescent material and a preparation method and application thereof, and belongs to the technical field of luminescent materials. 4+ The molar ratio of Ce 3+ , Yb 3+ , Tm 4+ and Zr is (60-80):(18-22):(0.08-0.12):(2-20). The NaCeF4-based up / down conversion luminescent material has good degradability, high up-conversion emission efficiency, and an up-conversion emission Stokes shift increased to the ultraviolet region; the up-conversion luminescent material can simultaneously emit up-conversion luminescence and down-conversion luminescence under 980nm laser irradiation, and is expected to be used as a contrast agent for fluorescence imaging; and the preparation process is simple, environment-friendly and low in cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of luminescent materials, in particular to a degradable NaCeF4-based upconversion / downconversion luminescent material and a preparation method and application thereof. BACKGROUND

[0002] The information disclosed in the background of the present application is only intended to increase the understanding of the overall background of the present application and should not necessarily be regarded as acknowledging or implying in any form that this information constitutes prior art known to those skilled in the art.

[0003] Rare earth doped upconversion luminescent materials have low toxicity, no background fluorescence, high light penetration depth, etc., and are a good fluorescent contrast agent, which has good application prospects in disease diagnosis, biological detection and imaging. Fluoride has low phonon energy (<400 cm -1 ), high refractive index, strong chemical stability, high optical transparency, narrow emission band, etc., and is a kind of upconversion luminescent matrix material widely used. At present, NaYbF4 has become the object of extensive research by researchers due to its high fluorescence quantum yield and excellent fluorescence performance. However, the traditional NaYbF4 matrix has a stable crystal structure and is difficult to degrade in the body, which can accumulate in the tissue for a long time and cause acute or chronic poisoning. In view of this problem, some researchers prepared upconversion nanoparticles with Na3ZrF7 / K3ZrF7 as the matrix. The arrangement of K3ZrF7 crystal lattice enables Yb 3+ / Er 3+ doped into a high-symmetry matrix, so that a series of red rare earth doped inorganic upconversion nanocrystals (UCNCs) can be prepared. The nanoparticles contain water-soluble [ZrF7] 3- clusters, which can exhibit good degradability under low pH conditions, and the doping of rare earth ions enables upconversion luminescence under near-infrared light excitation. However, the formation of Na3ZrF7 / K3ZrF7 matrix requires doping a large amount of zirconium ions, and the formation of a large amount of [ZrF7] 3- clusters often leads to rapid degradation of the material, uncontrollable degradation, and the synthesis process requires a completely water-free and oxygen-free environment, which is extremely harsh and has poor repeatability. In addition, the composite luminescent material in the prior art often needs to prepare different nanometer wavelength lasers due to the different nanometer wavelength lasers of different luminescent materials, which is expensive and has high experimental cost. Therefore, it is urgent to provide an upconversion / downconversion nanomaterial with controllable degradation, simple preparation method and simultaneous realization of multi-color luminescence. SUMMARY

[0004] Therefore, the application provides a degradable NaCeF4-based up / down conversion luminescent material, a preparation method and application thereof.

[0005] In a first aspect, the application provides a degradable NaCeF4-based up / down conversion luminescent material, which has a chemical formula of NaCeF4:Yb, Tm, Zr, wherein the molar ratio of Ce 3+ , Yb 3+ , Tm 3+ and Zr 4+ is (60-80):(18-22):(0.08-0.12):(2-20).

[0006] In a second aspect, the application provides a preparation method of the degradable NaCeF4-based up / down conversion luminescent material, which comprises the following steps:

[0007] A cerium source, a ytterbium source, an erbium source and a zirconium source are mixed and dissolved in water according to a stoichiometric ratio to obtain a mixed salt solution;

[0008] A fluoride aqueous solution and a sodium hydroxide aqueous solution are added to the mixed salt solution, and then the mixture is stirred uniformly and subjected to a hydrothermal reaction; and the obtained solid product is washed and dried to obtain the degradable NaCeF4-based up / down conversion luminescent material.

[0009] In a third aspect, the application provides an application of the degradable NaCeF4-based up / down conversion luminescent material, which is used for preparing a contrast agent for fluorescence imaging.

[0010] Compared with the prior art, the application has the following beneficial effects:

[0011] (1) The NaCeF4-based up / down conversion luminescent material has good degradability, and the degradation time of the material can be conveniently regulated by regulating the doping ratio of zirconium ions; the material has good dispersibility in an aqueous solution and a PBS solution, has high up-conversion emission efficiency, and has up-conversion emission Stokes shift increased to the ultraviolet region; and the up-conversion luminescent material can simultaneously appear up-conversion luminescence and down-conversion luminescence under 980 nm laser irradiation, and is expected to realize fluorescence imaging in a biological body by using the higher tissue penetration depth of the down-conversion luminescence, and can be used as a contrast agent for fluorescence imaging;

[0012] (2) The preparation method is very simple, does not need harsh anhydrous and anaerobic environment, and can complete material synthesis by using water as a solvent, so that environmental protection and low cost are achieved. BRIEF DESCRIPTION OF DRAWINGS

[0013] The accompanying drawings, which form a part of the specification, are included to provide a further understanding of the application and are incorporated herein in conjunction with the description of the application. Although the drawings represent illustrative embodiments of the application, the drawings are not meant to limit the application to the embodiments represented in the drawings. As will be readily understood, the drawings are meant to be only representative, and that each embodiment can include other embodiments as the skilled artisan will readily recognize.

[0014] Figure 1 is an X-ray diffraction pattern of the NaCeF4:Yb, Tm, Zr material of the embodiment 1 of the application;

[0015] Figure 2 is a transmission electron microscope picture of the NaCeF4:Yb, Tm, Zr material of the embodiment 1 of the application;

[0016] Figure 3 is an up-conversion emission spectrum of the NaCeF4:Yb, Tm, Zr material of the embodiment 1 of the application under excitation of 980 nm laser;

[0017] Figure 4 is a down-conversion emission spectrum of the NaCeF4:Yb, Tm, Zr material of the embodiment 1 of the application under excitation of 980 nm laser;

[0018] Figure 5 is a transmission electron microscope picture of the NaCeF4:Yb, Tm, Zr material of the embodiment 1 of the application after degradation for 48 h;

[0019] Figure 6 is a fluorescence spectrum diagram of the NaCeF4:Yb, Tm, Zr material of the embodiment 1 of the application at different degradation times;

[0020] Figure 7 is a fluorescence intensity picture of the NaCeF4:Yb, Tm, Zr material of the embodiment 1 of the application at different degradation times;

[0021] Figure 8 is a fluorescence spectrum diagram of the material of the embodiment 1~3 and the comparative example 1 of the application after degradation for 48 h;

[0022] Figure 9 is a down-conversion near-infrared two-region fluorescence picture of the NaCeF4:Yb, Tm, Zr material of the embodiment 1 of the application in a PBS solution;

[0023] Figure 10is a down-conversion near-infrared two-region fluorescence picture (A) and a mouse blood vessel section near-infrared two-region imaging (B) of NaCeF4:Yb,Tm,Zr in a mouse after tail vein injection in the test example of the present application. DETAILED DESCRIPTION

[0024] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise defined, 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 application belongs.

[0025] The present application provides a degradable NaCeF4-based up / down conversion luminescent material, which has a chemical formula of NaCeF4:Yb,Tm,Zr, wherein the molar ratio of Ce 3+ , Yb 3+ , Tm 3+ and Zr 4+ is (60-80):(18-22):(0.08-0.12):(2-20).

[0026] The NaCeF4-based up / down conversion luminescent material provided by the present application takes NaCeF4 as a matrix and Yb 3+ , Tm 3+ and Zr 4+ as doping ions, wherein Yb 3+ serves as a sensitized ion, Tm 3+ serves as a luminescent center, and Zr 4+ confers a soft crystal lattice structure on the up-conversion nanocrystal, so that it can be degraded in a physiological environment. In the present application, the total molar amount of Ce 3+ , Yb 3+ , Tm 3+ and Zr 4+ is in a ratio of 1:1 to the molar amount of Na + .

[0027] The NaCeF4-based up / down conversion luminescent material provided by the present application has good degradability, and the degradation time of the material can be conveniently regulated by regulating the doping ratio of zirconium ions. The material has good dispersibility in an aqueous solution and a PBS solution, has high up-conversion emission efficiency, and has an up-conversion emission Stokes shift increased to the ultraviolet region, and can simultaneously exhibit up-conversion luminescence and down-conversion luminescence under 980 nm laser irradiation.

[0028] In the present application, Ce 3+ , Yb 3+ , Tm 3+ and Zr 4+The molar ratio of the above-mentioned components is more preferably (65-75):(19-21):(0.09-0.11):(8-20).

[0029] The application provides a preparation method of the above-mentioned degradable NaCeF4-based up / down conversion luminescent material, which comprises the following steps:

[0030] The cerium source, ytterbium source, thulium source and zirconium source are mixed and dissolved in water in a stoichiometric ratio to obtain a mixed salt solution;

[0031] The mixed salt solution is added with an aqueous fluoride solution and an aqueous sodium hydroxide solution, and then stirred uniformly and subjected to a hydrothermal reaction; and the obtained solid product is washed and dried to obtain the product.

[0032] In the application, the cerium source is selected from one or more of cerium chloride, cerium nitrate or cerium acetate; the ytterbium source is selected from one or more of ytterbium chloride, ytterbium acetate, ytterbium sulfate or ytterbium nitrate; the thulium source is selected from one or two of thulium nitrate or thulium chloride; the zirconium source is selected from one or more of zirconium oxychloride, zirconium chloride, zirconium nitrate or zirconium acetate; and the fluoride is selected from ammonium fluoride or sodium fluoride. In one or more embodiments of the application, the cerium source is selected from cerium chloride heptahydrate, the ytterbium source is selected from ytterbium chloride hexahydrate, the thulium source is selected from thulium chloride hexahydrate, the zirconium source is selected from zirconium nitrate pentahydrate, and the fluoride is selected from ammonium fluoride.

[0033] In the mixed salt solution, the concentration of the cerium source is 0.05-0.2 mol / L, the concentration of the aqueous fluoride solution is 0.5-3 mol / L, and the concentration of the aqueous sodium hydroxide solution is 0.1-1 mol / L. The concentrations of the remaining substances can be calculated according to the set stoichiometric ratio. Suitable concentrations facilitate the hydrothermal reaction.

[0034] In the step of stirring uniformly and then performing the hydrothermal reaction, the stirring time is 10-60 min, and more preferably 20-40 min. During the uniform stirring process, the cerium source, ytterbium source, thulium source and zirconium source react with sodium hydroxide to generate corresponding hydroxide precipitates, and the stirring process can promote the generation of the precipitates.

[0035] In the application, the temperature of the hydrothermal reaction is 100-200℃, and more preferably 140-160℃; and the time of the hydrothermal reaction is 4-15 h, and more preferably 5-10 h. The application does not specially limit the heating rate of the temperature of the hydrothermal reaction, and the application preferably is 3-8℃ / min, and more preferably 4-6℃ / min. The application does not specially limit the cooling rate after the hydrothermal reaction, and the application can be naturally cooled to room temperature or accelerated to room temperature through water cooling, air cooling or the like.

[0036] The present application does not make special restrictions on the process of obtaining the solid product after the hydrothermal reaction, and the commonly used solid-liquid separation method in the art can be used, such as filtration, suction filtration or centrifugation.

[0037] The washing step in the present application is specifically using water and ethanol for washing in sequence, and the number of washing times is 2-5 times. The washing process is to remove the unreacted raw materials and purify the obtained product.

[0038] The present application does not make special restrictions on the drying process, and the present application preferably dries under vacuum at 50-70℃ until the solvent is completely volatilized.

[0039] The preparation method provided by the present application is very simple, does not require harsh anhydrous and anaerobic environment, and can complete the synthesis of the material by using water as the solvent, which is environmentally friendly and low in cost.

[0040] The present application also provides an application of the degradable NaCeF4-based up / down conversion luminescent material, and the application is that the degradable NaCeF4-based up / down conversion luminescent material is used for preparing a contrast agent for fluorescence imaging.

[0041] The present application will be further described in combination with specific examples. The present application does not make special restrictions on the source of the reagents used in the following examples, and commercially available goods known to those skilled in the art can be used.

[0042] Example 1

[0043] The present embodiment provides a preparation method of a degradable NaCeF4-based up / down conversion luminescent material (NaCeF4:Yb, Tm, Zr).

[0044] S1, respectively, 0.699 mmol of CeCl3•7H2O, 0.200 mmol of YbCl3•6H2O, 0.001 mmol of TmCl3•6H2O, 0.100 mmol of Zr(NO3)4•5H2O, 4 mmol of NH4F and 1 mmol of sodium hydroxide are taken as reaction raw materials;

[0045] S2, the weighed CeCl3•7H2O in step S1 is added to a beaker, dissolved with 5 mL of deionized water, and then YbCl3•6H2O, TmCl3•6H2O and Zr(NO3)4•5H2O are added respectively, mixed and stirred at room temperature for 10 min to obtain a mixed salt solution;

[0046] S3, 4 mL of 1 mmol / mL NH4F aqueous solution and 4 mL of 0.25 mmol / mL NaOH aqueous solution are added dropwise to the mixed salt solution in step S2 to form a white precipitate, and the mixture is stirred for 30 min to obtain a precursor dispersion.

[0047] S4, the precursor dispersion obtained in step S3 is added to an autoclave, and then the autoclave is placed in an oven, heated to 150°C at a heating rate of 5°C / min, reacted for 8 h, and then cooled to room temperature to obtain a product;

[0048] S5, the product in step S6 is centrifuged, washed with deionized water and anhydrous ethanol three times in turn, and placed in a 60°C vacuum oven for drying to obtain a NaCeF4:Yb,Tm,Zr powder material.

[0049] Figure 1 is the X-ray diffraction pattern of the NaCeF4:Yb,Tm,Zr material of the present embodiment, and X-ray diffraction (XRD) analysis shows that it is consistent with the standard card data of JCPDS 75-1924, and shows 2θ peaks at about 16.6° (100), 23.5° (001), and 28.9° (110). Figure 2 is the transmission electron microscope picture of the NaCeF4:Yb,Tm,Zr material of the present embodiment, and it can be seen that the NaCeF4 crystals are uniformly arranged in a tetragonal phase.

[0050] Figure 3 is the upconversion emission spectrum of the NaCeF4:Yb,Tm,Zr material of the present embodiment under the excitation of 980 nm laser, Figure 4 is the downconversion emission spectrum thereof under the excitation of 980 nm laser, and it can be seen that the NaCeF4:Yb,Tm,Zr can simultaneously convert 980 nm near-infrared light into multi-wavelength visible light (upconversion emission) and near-infrared two-region light (downconversion emission).

[0051] Example 2

[0052] The present embodiment provides a preparation method of a degradable NaCeF4-based up / down conversion luminescent material (NaCeF4:Yb,Tm,Zr).

[0053] S1, 0.699 mmol of CeCl3•7H2O, 0.200 mmol of YbCl3•6H2O, 0.001 mmol of TmCl3•6H2O, 0.020 mmol of Zr(NO3)4•5H2O, 4 mmol of NH4F, and 1 mmol of sodium hydroxide are weighed as reaction raw materials, respectively;

[0054] S2, the weighed CeCl3•7H2O in step S1 is added to a beaker and dissolved with 5 mL of deionized water, and then YbCl3•6H2O, TmCl3•6H2O, and Zr(NO3)4•5H2O are added and stirred at room temperature for 10 min to obtain a mixed salt solution;

[0055] S3, 4 mL of 1 mmol / mL NH4F aqueous solution and 4 mL of 0.25 mmol / mL NaOH aqueous solution were added dropwise into the mixed salt solution in step S2, white precipitate was generated, stirring for 30 min, to obtain a precursor dispersion;

[0056] S4, the precursor dispersion obtained in step S3 was added into a hydrothermal kettle, then the hydrothermal kettle was put into an oven, heated to 150°C at a heating rate of 5°C / min, reacted for 8 h, then cooled to room temperature, to obtain a product;

[0057] S5, the product in step S6 was centrifuged, then washed with deionized water and anhydrous ethanol for 3 times, and dried in a 60°C vacuum oven, to obtain a NaCeF4:Yb,Tm,Zr powder.

[0058] Example 3

[0059] The embodiment provides a preparation method of a degradable NaCeF4-based up / down conversion luminescent material (NaCeF4:Yb,Tm,Zr).

[0060] S1, 0.699 mmol of CeCl3·7H2O, 0.200 mmol of YbCl3·6H2O, 0.001 mmol of TmCl3·6H2O, 0.200 mmol of Zr(NO3)4·5H2O, 4 mmol of NH4F and 1 mmol of sodium hydroxide were weighed as reaction raw materials respectively;

[0061] S2, the weighed CeCl3·7H2O in step S1 was added into a beaker and dissolved with 5 mL of deionized water, then YbCl3·6H2O, TmCl3·6H2O and Zr(NO3)4·5H2O were added respectively, and stirred at room temperature for 10 min, to obtain a mixed salt solution;

[0062] S3, 4 mL of 1 mmol / mL NH4F aqueous solution and 4 mL of 0.25 mmol / mL NaOH aqueous solution were added dropwise into the mixed salt solution in step S2, white precipitate was generated, stirring for 30 min, to obtain a precursor dispersion;

[0063] S4, the precursor dispersion obtained in step S3 was added into a hydrothermal kettle, then the hydrothermal kettle was put into an oven, heated to 150°C at a heating rate of 5°C / min, reacted for 8 h, then cooled to room temperature, to obtain a product;

[0064] S5, the product in step S6 was centrifuged, then washed with deionized water and anhydrous ethanol for 3 times, and dried in a 60°C vacuum oven, to obtain a NaCeF4:Yb,Tm,Zr powder.

[0065] Comparative Example

[0066] The present comparative example is compared with Example 1, the difference being that the present comparative example does not add Zr(NO3)4·5H2O.

[0067] Test Example

[0068] 1. Degradation experiment of the NaCeF4:Yb,Tm,Zr material of Example 1:

[0069] 5 mg of NaCeF4:Yb,Tm,Zr was accurately weighed and dissolved in 10 mL of PBS solution, and after uniform dissolution, the solution was placed in a 37°C vacuum oven, and the fluorescence intensity value of the solution was measured at 0 h, 1 h, 3 h, 6 h, 12 h, 18 h, 24 h and 48 h, respectively. Figure 5 The transmission electron microscope picture of the NaCeF4:Yb,Tm,Zr material after degradation for 48 h can be seen, and the nanoparticles gradually degrade into debris after 48 h. Figure 6 The fluorescence spectrum of the NaCeF4:Yb,Tm,Zr material at different degradation times can be seen, and the signal intensity of each peak gradually decreases as the degradation time increases. Figure 7 The fluorescence intensity picture of the NaCeF4:Yb,Tm,Zr material at different degradation times can be seen, and the fluorescence intensity gradually decreases as the time increases.

[0070] Figure 8 The fluorescence spectrum of the materials of Examples 1-3 and Comparative Example 1 after degradation for 48 h can be seen, and it is found that the fluorescence intensity of the material of Comparative Example 1 (Zr doping amount is 0) does not decrease significantly, indicating that the material does not degrade, and the materials of Examples 1 and 3 both degrade significantly, and the fluorescence intensity of the material of Example 2 decreases, which shows that the degradation time can be controlled by adjusting the doping amount of Zr.

[0071] 2. Fluorescence imaging experiment:

[0072] In order to prove the tissue penetration and imaging ability of UCNPs in mice, the PBS solution of NaCeF4:Yb,Tm,Zr was injected into the tail vein of mice, and the fluorescence characteristics of the material in the mouse body were observed, Figure 9 The down-conversion near-infrared two-region fluorescence picture of NaCeF4:Yb,Tm,Zr in PBS solution can be seen, and it can be seen that it has good dispersibility in PBS solution; the near-infrared two-region fluorescence imaging of the living body was carried out, as shown in Figure 10 It can be seen that NaCeF4:Yb,Tm,Zr emits bright fluorescence signals in the mouse body, proving that the degradable NaCeF4-based upconversion / luminescent material can be used to prepare contrast agents for fluorescence imaging.

[0073] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application. The present application can have various changes and modifications for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A biodegradable NaCeF4-based up / downconversion luminescent material, characterized in that, Its chemical formula is NaCeF4:Yb,Tm,Zr, where Ce 3+ Yb 3+ Tm 3+ and Zr 4+ The molar ratio is (60~80): (18~22): (0.08~0.12): (2~20); Ce 3+ Yb 3+ Tm 3+ and Zr 4+ Total molar amount and Na + The molar ratio is 1:

1.

2. The biodegradable NaCeF4-based up / downconversion luminescent material as described in claim 1, characterized in that, Ce 3+ Yb 3+ Tm 3+ and Zr 4+ The molar ratio is (65~75): (19~21): (0.09~0.11): (8~20).

3. The method for preparing the biodegradable NaCeF4-based up / downconversion luminescent material according to any one of claims 1 to 2, characterized in that, Includes the following steps: Cerium source, ytterbium source, thulium source and zirconium source are mixed and dissolved in water according to stoichiometric ratio to obtain a mixed salt solution; Add aqueous solutions of fluoride and sodium hydroxide to a mixed salt solution, stir until homogeneous, and then carry out a hydrothermal reaction. The resulting solid product is then washed and dried.

4. The preparation method according to claim 3, characterized in that, The cerium source is selected from one or more of cerium chloride, cerium nitrate, or cerium acetate; the ytterbium source is selected from one or more of ytterbium chloride, ytterbium acetate, ytterbium sulfate, or ytterbium nitrate; the thulium source is selected from one or two of thulium nitrate or thulium chloride; the zirconium source is selected from one or more of zirconium oxychloride, zirconium chloride, zirconium nitrate, or zirconium acetate; and the fluoride is selected from ammonium fluoride or sodium fluoride.

5. The preparation method according to claim 3, characterized in that, In the mixed salt solution, the concentration of the cerium source is 0.05~0.2 mol / L; the concentration of the fluoride aqueous solution is 0.5~3 mol / L; and the concentration of the sodium hydroxide aqueous solution is 0.1~1 mol / L.

6. The preparation method according to claim 3, characterized in that, In the step of carrying out the hydrothermal reaction after stirring evenly, the stirring time is 10~60 min.

7. The preparation method according to claim 3, characterized in that, The hydrothermal reaction temperature is 100~200 ℃, and the hydrothermal reaction time is 4~15 h.

8. The preparation method according to claim 7, characterized in that, The hydrothermal reaction temperature is 140~160 ℃, and the hydrothermal reaction time is 5~10 h.

9. The preparation method according to claim 3, characterized in that, The washing process involves washing with water and ethanol sequentially, repeating the washing process 2 to 5 times.

10. The application of the biodegradable NaCeF4-based up / downconversion luminescent material according to any one of claims 1-2 or the biodegradable NaCeF4-based up / downconversion luminescent material prepared by the preparation method according to any one of claims 3-9, characterized in that, The biodegradable NaCeF4-based up / downconversion luminescent material is used to prepare a contrast agent for fluorescence imaging.

Images