A rare earth doped M3ScF6 nanocrystal and a preparation method thereof

Abstract

This invention belongs to the field of rare earth doped fluoride preparation technology, specifically relating to a rare earth doped M3ScF6 nanocrystal and its preparation method. To address the problems of numerous operational steps, inherent risks, high costs, and poor product quality in the preparation of rare earth doped M3ScF6, this invention uses rare earth acetates (such as (CH3COO)3Sc, (CH3COO)3Er, (CH3COO)3Yb, etc.), CH3COOM (where M is a monovalent alkali metal, such as Na or K), and NH4F as the main raw materials, with ethylene glycol as the solvent. The process involves dissolving and mixing the materials, heating and stirring at low temperature under normal pressure, followed by washing, centrifugation, and drying to obtain the rare earth doped M3ScF6 nanocrystals.

Description

[0001] The application belongs to the technical field of preparation of rare earth doped fluoride, and particularly relates to a rare earth doped M3ScF6 nanocrystal and a preparation method thereof. BACKGROUND

[0002] Rare earth doped luminescent materials can convert near-infrared light into visible light and near-infrared light due to their unique energy conversion mechanism, and show great application potential in the fields of solar cells, solid-state lasers, color displays, biological imaging and the like. Scandium (Sc) element has a unique position in the classification of rare earth elements, which is located at the starting position of the third sub-group and is also the beginning of the transition element sequence, and the radius of scandium ion is the smallest among all rare earth elements. This unique structural position and size characteristic makes scandium-based materials significantly different from yttrium (Y), gadolinium (Gd) and lutetium (Lu) based materials in physical and chemical properties. M3ScF6 as a kind of matrix material is an ideal choice for a new type of high-efficiency up-conversion luminescent matrix material due to its characteristics of stable chemical properties and low phonon energy, and the successful preparation of high-quality M3ScF6 luminescent nanocrystals is imminent in the application of various fields such as solid-state lasers.

[0003] At present, the preparation methods of rare earth doped M3ScF6 materials mainly include high temperature solid phase method, coprecipitation method, solvothermal method and so on. These methods have their own advantages and disadvantages, but they all have certain limitations. The solid phase synthesis method mixes the solid sodium source, scandium source and fluorine source and other raw materials according to a certain stoichiometric ratio, uses high temperature to make the atoms or ions on the surface of the raw material particles have enough energy for diffusion and reaction ability, and directly synthesizes Na3ScF6. The chemical coprecipitation method is to prepare a mixed aqueous solution of metal salts such as sodium nitrate and scandium nitrate to a certain concentration, and also prepare a solution of fluorine source such as hydrofluoric acid or ammonium fluoride. Under stirring conditions, the fluorine source solution is slowly added to the metal salt mixed solution, and by adjusting the reaction temperature, pH value and dropping speed, the precipitation reaction is fully carried out. This method has rapid reaction process, can realize precise control and has low reaction temperature, which reduces the equipment investment cost and energy consumption. However, this method uses HF with strong chemical corrosion in its preparation process, which has the risk of production safety accidents and waste liquid treatment problems. The principle of the solvothermal method is to use the special properties of organic solvents at high temperature and high pressure to add metal salts (such as scandium chloride, sodium acetate), fluorine sources (such as potassium fluoride, ammonium fluoride) and organic solvents (such as ethylene glycol, diethylene glycol) into the reaction kettle in a certain proportion, seal it and put it into an oven or other heating equipment, and react at a set temperature and time to obtain the expected product. The advantages are that the morphology and size of the product can be accurately controlled, and high-crystallinity and well-dispersed nanoparticles can be synthesized, and the optical performance of the product is often good. The disadvantages are that the reaction process is carried out in a closed system, which has certain safety risks, and the recovery and treatment of organic solvents are complex, which increases the production cost and process difficulty. Therefore, it is of great significance to explore new preparation methods to improve the performance and application prospect of rare earth doped M3ScF6 materials. SUMMARY

[0004] In order to solve the problems of multiple operation steps, danger, high cost and poor product quality in the preparation method of rare earth doped M3ScF6, the present application provides a kind of rare earth doped M3ScF6 nanocrystal and its preparation method. The present application prepares M3ScF6 material with excellent near-infrared response luminescence performance by means of low temperature synthesis method. This method not only realizes the near-infrared response and luminescence stability of M3ScF6 material, but also reduces the preparation cost, providing strong support for the wide application of rare earth doped conversion luminescent materials.

[0005] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0006] The present application provides a preparation method of rare earth doped M3ScF6 nanocrystal, comprising the following steps:

[0007] The rare earth acetate, CH3COOM and NH4F are respectively fully dissolved in ethylene glycol solvent, mixed and then stirred to prepare the nanocrystals.

[0008] Further, the preparation method is specifically as follows:

[0009] Step 1, at normal temperature and pressure, the rare earth acetate and CH3COOM powder are mixed in ethylene glycol solvent, and are strongly stirred until fully dissolved to obtain a mixed solution A;

[0010] Step 2, at normal temperature and pressure, the NH4F solid powder is dissolved in ethylene glycol solvent, and is strongly stirred until fully dissolved to obtain a mixed solution B;

[0011] Step 3, the mixed solution A and the mixed solution B are mixed and stirred to prepare a nanocrystal sample;

[0012] Step 4, the nanocrystal sample is washed, and the obtained nanocrystal sample is collected by centrifugation and dried to obtain the nanocrystal.

[0013] Further, the rare earth acetate in the step 1 is (CH3COO)3Sc and CH3COOLn, the Ln in CH3COOLn is one or both of Er and Yb, and the M in the CH3COOM powder is Na or K.

[0014] Further, the molar ratio of the rare earth acetate, the CH3COOM powder and the NH4F solid powder is 1:30:6.

[0015] Further, the specific conditions of the mixing and stirring reaction in the step 3 are as follows:

[0016] At normal pressure and in an environment of 100-150 DEG C, the stirring speed is controlled at 600-700 rpm, and heating is maintained for 1 hour.

[0017] Further, the drying temperature in the step 4 is 60 DEG C, and the time is 24 h.

[0018] The application further provides a rare earth doped M3ScF6 nanocrystal prepared by the preparation method of the rare earth doped M3ScF6 nanocrystal.

[0019] Further, the composition of the nanocrystal is M3ScF6 and Ln, the M is Na or K, the Ln is one or both of Er and Yb, the crystal structure of the nanocrystal is monoclinic crystal structure, and the nanocrystal is a spherical-like particle.

[0020] Further, the nanocrystals can produce double optical responses of visible up-conversion emission and near-infrared two-region down-conversion emission under excitation of a 980 nm laser at room temperature.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] The process for preparing the rare earth doped M3ScF6 up-conversion nanocrystals by the method is simple, does not need inert gas protection, does not need precursor grinding, does not need corrosive dangerous solvents, does not need high pressure environment, has lower energy consumption, and is convenient for popularization.

[0023] The present application fully dissolves fluorine source and rare earth acetate by ethylene glycol (EG) respectively, and forms spherical morphology under normal pressure condition, and the reaction can be completed under the condition that the reaction temperature is controlled at 100-150 DEG C and the reaction time is one hour. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is the XRD pattern of Na3ScF6:Er nanocrystals obtained in Example 1 of the present application;

[0025] Figure 2 is the TEM pattern of Na3ScF6:Er nanocrystals obtained in Example 1 of the present application;

[0026] Figure 3 is the visible light emission spectrum pattern of Na3ScF6:Er nanocrystals obtained in Example 1 of the present application;

[0027] Figure 4 is the near-infrared emission spectrum pattern of Na3ScF6:Er nanocrystals obtained in Example 1 of the present application;

[0028] Figure 5 is the XRD pattern of K3ScF6:Yb / Er nanocrystals obtained in Example 2 of the present application;

[0029] Figure 6 is the TEM pattern of K3ScF6:Yb / Er nanocrystals obtained in Example 2 of the present application;

[0030] Figure 7 is the visible light emission spectrum pattern of K3ScF6:Yb / Er nanocrystals obtained in Example 2 of the present application;

[0031] Figure 8 is the near-infrared emission spectrum pattern of K3ScF6:Yb / Er nanocrystals obtained in Example 2 of the present application. DETAILED DESCRIPTION

[0032] In order to further illustrate the technical scheme of the present application, the present application is further illustrated by the following examples. Example 1

[0033] The embodiment provides a preparation method of a rare earth doped M3ScF6 nanocrystal, and comprises the following steps:

[0034] Step 1, under normal temperature and pressure, 1 mmol of rare earth acetate (0.98 mmol (CH3COO)3Sc and 0.02 mmol (CH3COO)3Er) is mixed with 30 mmol of CH3COONa powder in 10 mL of ethylene glycol (EG) solvent to be stirred intensively until being dissolved completely, to obtain a transparent mixed solution A;

[0035] Step 2, under normal temperature and pressure, 6 mmol of NH4F solid powder is added into 10 mL of ethylene glycol (EG) solvent to be stirred intensively until being dissolved completely, to obtain a transparent mixed solution B;

[0036] Step 3, solution A and solution B are transferred into a conical flask to be mixed and stirred, and the stirring speed is controlled at 600 rpm under normal pressure and at 150 DEG C, and heating is kept for 1 hour, to prepare a nanocrystal sample;

[0037] Step 4, the nanocrystal sample is washed with anhydrous ethanol for 3-5 times, the obtained nanocrystal sample is collected by centrifugation, and is placed in a drying box to be dried at 60 DEG C for 24 hours, to obtain Na3ScF6:Er nanocrystal.

[0038] X-ray diffraction (XRD) method and transmission electron microscopy (TEM) are used to analyze the phase and morphology of the prepared Na3ScF6:Er nanocrystal sample. The results are shown in Figure 1 It is shown that the positions of the diffraction peaks of the sample are consistent with those of the Na3ScF6 standard card (PDF #20-1153), and no impurity peak is detected, which indicates that the synthesized sample is a pure phase monoclinic crystal structure and has high crystallinity. The TEM characterization results are shown in Figure 2 It is shown that the nanocrystal has a spherical morphology and a uniform particle size distribution.

[0039] The prepared Na3ScF6:Er nanocrystal sample is further tested for up-conversion and down-conversion luminescence performance under 980 nm laser excitation. The up-conversion emission spectrum of the nanocrystal is shown in Figure 3 It is shown that obvious red emission bands appear in the range of 640-710 nm, and relatively weak green emission bands can be observed in the range of 510-570 nm, which are respectively attributed to Er 3+ ions 4 F9 / 2→ 4 I 15 / 2 and ( 2 H 11 / 2, 4 S3 / 2)→4 I 15 / 2 characteristic transition. Downconversion emission spectrum ( Figure 4 The results show that there is significant near-infrared emission in the 1450-1650 nm band, with a central peak at approximately 1530 nm, corresponding to Er. 3+ ion 4 I 13 / 2→ 4 I 15 / 2 energy level transition. The above results clearly demonstrate that the sample can achieve efficient emission in the near-infrared II (NIR-II) band, providing a basis for its potential advantages in bioimaging and related optical applications. Example 2

[0040] This embodiment provides a method for preparing rare earth-doped M3ScF6 nanocrystals, including the following steps:

[0041] Step 1: At room temperature and pressure, 1 mmol of rare earth acetate (0.78 mmol (CH3COO)3Sc, 0.02 mmol (CH3COO)3Er, 0.20 mmol (CH3COO)3Yb) and 30 mmol CH3COOK powder were vigorously stirred in 10 mL of EG solvent until fully dissolved to obtain a transparent mixed solution A;

[0042] Step 2: At room temperature and pressure, dissolve 6 mmol of NH4F solid powder in 10 mL of EG solvent and stir vigorously until fully dissolved to obtain a transparent mixed solution B;

[0043] Step 3: Transfer solution A and solution B to an Erlenmeyer flask, mix them, stir and react them. Keep the flask open at normal pressure and 100°C, control the stirring speed at 700 rpm, and keep heating for 1 hour to prepare nanocrystalline samples.

[0044] Step 4: Wash the nanocrystal sample with anhydrous ethanol 3-5 times, collect the obtained nanocrystal sample by centrifugation, and dry it in a drying oven at 60°C for 24 hours to obtain K3ScF6:Yb / Er nanocrystals.

[0045] Figure 5 and Figure 6 The XRD and TEM results for K3ScF6:Yb / Er nanocrystals are shown below. The results show that the obtained XRD pattern is highly consistent with the simulated pattern of the K3ScF6 standard card (PDF#79-0770), and no other impurity peaks were detected, indicating that K3ScF6:Yb / Er nanocrystals possess high phase purity and a stable crystal structure. TEM images are shown below. Figure 6As shown, the sample morphology is spherical, and the particle size distribution is uniform. The up-conversion emission spectrum of the nanocrystal under 980nm laser excitation is shown in Figure 2. Figure 7 It can be observed that there is a strong red emission band in the wavelength range of 640-710nm, and a relatively weak green emission band in the range of 450-570nm, which correspond to the characteristic transitions of Er 3+ ions, respectively.

[0046] Figure 8 The down-conversion emission spectrum of Yb 3+ / Er 3+ co-doped K3ScF6 nanocrystal under 980nm laser excitation is shown in Figure 3. The results show that there is an obvious near-infrared emission band in the wavelength range of 1450-1650nm, with a center wavelength of about 1530nm. The emission is derived from the energy level transition of Er 3+ ions. 4 I 13 / 2→ 4 I 15 / 2 energy level transition, in which Yb 3+ ions act as a sensitizer to absorb 980nm photons, and effectively excite Er 3+ ions through energy transfer process, thereby enhancing the near-infrared emission.

[0047] In summary, the preparation method of the present application is unique, and (CH3COO)3Sc is selected as the key raw material. (CH3COO)3Sc has the characteristics of stable chemical properties, easy to obtain and suitable reaction activity, which lays a good foundation for the smooth progress of subsequent reactions. In the entire preparation process, there is no need for inert gas protection, no need for precursor grinding, no need for corrosive hazardous solvents, no need for high pressure environment, and the core operation is only simple heating and stirring. The prepared nanocrystal performs well in terms of morphology uniformity, crystalline quality and luminescent performance.

[0048] The main features and advantages of the present application are shown and described above, and it is obvious for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and can be realized in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application.

[0049] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a rare earth doped M3ScF6 nanocrystal, characterized in that, The method comprises the following steps: The nanocrystals are prepared by fully dissolving rare earth acetate, CH3COOM and NH4F in ethylene glycol solvent respectively, mixing and then stirring, without inert gas protection, without precursor grinding, without corrosive dangerous solvents, without high pressure environment, and the preparation method is specifically as follows: Step 1, under normal temperature and pressure, mixing rare earth acetate and CH3COOM powder in ethylene glycol solvent, and strongly stirring until fully dissolved to obtain mixed solution A; Step 2, under normal temperature and pressure, dissolving NH4F solid powder in ethylene glycol solvent, and strongly stirring until fully dissolved to obtain mixed solution B; Step 3, mixing mixed solution A and mixed solution B, and stirring under normal pressure and at 100-150 DEG C to prepare nanocrystal samples; Step 4, cleaning the nanocrystal samples, collecting the obtained nanocrystal samples by centrifugation, and drying to obtain the nanocrystals; in step 1, the rare earth acetate is (CH3COO)3Sc and CH3COOLn, Ln in CH3COOLn is one or both of Er and Yb, and M in CH3COOM powder is Na or K.

2. The method according to claim 1, wherein the method is characterized by, The molar ratio of the rare earth acetate, CH3COOM powder and NH4F solid powder is 1:30:

6.

3. The method according to claim 1, wherein the method is characterized by, In step 3, the specific conditions of the stirring reaction are as follows: The stirring speed is controlled at 600-700 rpm, and heating is maintained for 1 hour.

4. The method of claim 1, wherein the method is characterized by: In step 4, the drying temperature is 60 DEG C, and the time is 24 h.

5. The rare earth doped M3ScF6 nanocrystals prepared by the preparation method of the rare earth doped M3ScF6 nanocrystals according to any one of claims 1-4.

6. The rare earth doped M3ScF6 nanocrystal of claim 5, wherein M is selected from the group consisting of Y, Gd, La, Lu, and combinations thereof. The composition of the nanocrystals is M3ScF6 and Ln, M is Na or K, and Ln is Er or Yb, the crystal structure of the nanocrystals is monoclinic crystal structure, and the nanocrystals are spherical particles.

7. The rare earth doped M3ScF6 nanocrystal of claim 5, wherein M is selected from the group consisting of Y, Gd, La, Lu, and combinations thereof. The nanocrystals simultaneously produce visible up-conversion emission and near-infrared two-zone down-conversion emission under the excitation of 980 nm laser at room temperature.

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