Upconversion luminescent material and preparation method and application thereof

Abstract

The present invention relates to the field of nanomaterial synthesis, and discloses an upconversion luminescent material, a preparation method thereof, and an application thereof. The preparation method of the upconversion luminescent material comprises: (1) first stirring an ytterbium salt solution, an ammonium molybdate tetrahydrate solution, and a rare earth metal salt solution to obtain an intermediate I; the rare earth metal salt in the rare earth metal salt solution is selected from at least one of an erbium salt, a holmium salt, a praseodymium salt, and a europium salt; (2) subjecting the intermediate I to a hydrothermal reaction in a hydrothermal reactor to obtain an intermediate II; and (3) sequentially subjecting the intermediate II to a drying treatment and a calcination treatment to obtain the upconversion luminescent material. The upconversion luminescent material particles prepared by the method of the present invention have an average particle size of nanometer level, a good degree of crystallinity, and good reverse thermal quenching performance.

Description

Technical Field

[0001] The present invention relates to the field of nanomaterial synthesis, and in particular to up-conversion luminescent materials, preparation methods and applications thereof. Background Art

[0002] Upconversion luminescent materials are anti-Stokes luminescent materials. They absorb two or more long-wavelength, low-energy photons and emit short-wavelength, high-energy photons. They can also absorb near-infrared light and emit visible light. Compared with traditional luminescent materials, upconversion luminescent materials offer advantages such as long fluorescence lifetimes, rich emission energy levels, and narrow emission spectra. They are widely used in temperature sensors, biomedical probes, information encryption and anti-counterfeiting, solar cells, and 3D imaging.

[0003] Upconversion luminescent materials are composed of base materials, sensitizers and activators. The base materials can be fluorides, oxides, bromides, etc., and the sensitizers and activators are mostly rare earth ions.

[0004] Currently, the preparation of upconversion luminescent materials often requires high-temperature reactions, resulting in high energy consumption and large particle sizes. Furthermore, upconversion luminescent materials suffer from low luminescence efficiency and are subject to issues such as thermal quenching and concentration quenching, which significantly limit their practical application and hinder their industrialization.

[0005] CN105778911A discloses a rare earth-doped photoluminescent material based on YbMoO4. The material is obtained by reacting erbium nitrate, ytterbium nitrate, and ammonium heptamolybdate. The preparation method for the luminescent material comprises dissolving erbium nitrate and ytterbium nitrate in ethanol to obtain a solution A, dissolving ammonium heptamolybdate in deionized water to obtain a solution B, adjusting the pH of solution B to 7.0 with a 1M NaOH solution, then slowly pouring the solution into solution A and stirring for one hour. The solution is dried at 100°C for 12 hours, then heated in a muffle furnace to 500-800°C at a rate of 8°C / min, and cooled in the furnace for two hours to obtain the rare earth-doped photoluminescent material based on YbMoO4. The method of the present invention is simple, easy to operate, and low-cost. The rare-earth-doped photoluminescent material prepared has high luminous efficiency and excellent optical temperature sensing properties. However, this method requires high energy consumption, has a long reaction time, and is not fully reactive. The resulting particles are large and unevenly distributed, and the luminous efficiency decreases with increasing temperature, significantly limiting the application of upconversion luminescent materials in high-temperature regions.

[0006] Therefore, it is of great significance to develop a new upconversion luminescent material. Summary of the Invention

[0007] The purpose of the present invention is to provide an up-conversion luminescent material with nanometer-level average particle size, good crystallinity and reverse thermal quenching performance.

[0008] In order to achieve the above object, the first aspect of the present invention provides a method for preparing an upconversion luminescent material, the method comprising:

[0009] (1) stirring an ytterbium salt solution, an ammonium molybdate tetrahydrate solution, and a rare earth metal salt solution to obtain an intermediate I; the rare earth metal salt in the rare earth metal salt solution is selected from at least one of an erbium salt, a holmium salt, a praseodymium salt, and a europium salt;

[0010] (2) subjecting the intermediate I to a hydrothermal reaction in a hydrothermal reactor to obtain an intermediate II; the hydrothermal reaction conditions include: a temperature of 130-180° C. and a time of 1.5-2.5 h;

[0011] (3) drying and calcining the intermediate II in sequence to obtain the upconversion luminescent material;

[0012] In step (1), in the mixed solution at the start of the first stirring, Yb 3+ The concentration of is 0.2-0.32 mol / L, the concentration of ammonium molybdate tetrahydrate is 0.15-0.22 mol / L, and the concentration of rare earth metal ions is 0.004-0.02 mol / L.

[0013] The second aspect of the present invention provides an up-conversion luminescent material prepared by the method described in the first aspect.

[0014] The third aspect of the present invention provides the use of the upconversion luminescent material described in the second aspect in biomedical diagnosis, information encryption storage or solar cells.

[0015] The technical solution provided by the present invention has at least the following advantages over the prior art:

[0016] (1) The upconversion luminescent material provided by the present invention has good crystallinity, high purity, easy to control morphology and reverse thermal quenching performance.

[0017] (2) The present invention adopts a hydrothermal reaction method to prepare upconversion luminescent materials, which has a simple preparation process, low reaction temperature, short reaction time, low energy consumption, sufficient reaction, low material synthesis cost, and no need to use organic solvents, which is more environmentally friendly.

[0018] (3) The upconversion luminescent material particles provided by the present invention have an average particle size of nanometer level, a small particle size, and a uniform size distribution of the nanomaterials, which can be applied in the field of nanomaterials, thus expanding the application range of upconversion luminescent materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a scanning electron microscope image of the upconversion luminescent material S1;

[0020] Figure 2 The X-ray diffraction spectra of up-conversion luminescent materials S1, S2, S3, S4, DS1, DS2 and DS3 are shown in FIG. 1 , wherein the left part shows the X-ray diffraction spectra of S1, S2, S3 and S4, and the right part shows the X-ray diffraction spectra of DS1, DS2 and DS3;

[0021] Figure 3 This is the upconversion luminescence spectrum of the upconversion luminescent material S1 at different temperatures under 980nm laser excitation;

[0022] Figure 4 This is the upconversion luminescence spectrum of the upconversion luminescent material S2 at different temperatures under 980nm laser excitation;

[0023] Figure 5 This is the upconversion luminescence spectrum of the upconversion luminescent material S3 at different temperatures under 980nm laser excitation;

[0024] Figure 6 This is the upconversion luminescence spectrum of the upconversion luminescent material S4 at different temperatures under 980nm laser excitation;

[0025] Figure 7 This is the upconversion luminescence spectrum of the upconversion luminescent material DS1 under 980nm laser excitation;

[0026] Figure 8 This is the upconversion luminescence spectrum of the upconversion luminescent material DS2 under 980nm laser excitation;

[0027] Figure 9 This is the upconversion luminescence spectrum of the upconversion luminescent material DS3 at different temperatures under 980nm laser excitation. DETAILED DESCRIPTION

[0028] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0029] As mentioned above, the first aspect of the present invention provides a method for preparing an upconversion luminescent material, the method comprising:

[0030] (1) stirring an ytterbium salt solution, an ammonium molybdate tetrahydrate solution, and a rare earth metal salt solution to obtain an intermediate I; the rare earth metal salt in the rare earth metal salt solution is selected from at least one of an erbium salt, a holmium salt, a praseodymium salt, and a europium salt;

[0031] (2) subjecting the intermediate I to a hydrothermal reaction in a hydrothermal reactor to obtain an intermediate II; the hydrothermal reaction conditions include: a temperature of 130-180° C. and a time of 1.5-2.5 h;

[0032] (3) drying and calcining the intermediate II in sequence to obtain the upconversion luminescent material;

[0033] In step (1), in the mixed solution at the start of the first stirring, Yb 3+ The concentration of is 0.2-0.32 mol / L, the concentration of ammonium molybdate tetrahydrate is 0.15-0.22 mol / L, and the concentration of rare earth metal ions is 0.004-0.02 mol / L.

[0034] It should be noted that, in the present invention, there is no special requirement for the ytterbium salt and the rare earth metal salt, as long as the Yb 3+ and the rare earth metal ion. For example, the ytterbium salt is ytterbium nitrate, and the rare earth metal salt is selected from at least one of erbium nitrate, holmium nitrate, praseodymium nitrate and europium nitrate.

[0035] Preferably, in step (1), the Yb in the ytterbium salt solution is 3+ The molar ratio of the amount of the ammonium molybdate tetrahydrate in the ammonium molybdate tetrahydrate solution calculated on a dry basis is 1:0.7-0.9 mol.

[0036] Preferably, in step (1), the Yb 3+ and the total molar amount of rare earth metal ions in the rare earth metal salt solution are used as the basis, the Yb in the ytterbium salt solution 3+ The amount of the rare earth metal salt solution is 92-98 mol%, and the amount of the rare earth metal ions in the rare earth metal salt solution is 2-8 mol%. The inventors of the present invention have found that in this preferred embodiment, the up-conversion luminescent material provided by the present invention has better reverse thermal quenching performance.

[0037] Preferably, in step (2), the conditions of the hydrothermal reaction include: a temperature of 130-150° C. The inventors of the present invention have found that under this preferred condition, the up-conversion luminescent material provided by the present invention has a better degree of crystallinity.

[0038] Preferably, in step (1), the Yb in the ytterbium salt solution is 3+ The concentration is 0.5-0.7mol / L.

[0039] Preferably, in step (1), the concentration of the ammonium molybdate tetrahydrate solution is 0.25-0.35 mol / L.

[0040] Preferably, in step (1), the concentration of rare earth metal ions in the rare earth metal salt solution is 0.5-3.5 mol / L. The inventors of the present invention have found that under this preferred condition, the upconversion luminescent material provided by the present invention has better reverse thermal quenching performance.

[0041] Preferably, in step (1), the first stirring conditions include: a temperature of 10-30° C. and a time of 1.5-2.5 h. The inventors of the present invention have found that, in this preferred embodiment, the particle size of the upconversion luminescent material provided by the present invention is smaller and the reverse thermal quenching performance is better.

[0042] It should be noted that in step (2), the method further includes, before the drying treatment, washing the intermediate II at least once, centrifuging, and the like, and then subjecting the resulting precipitate to the drying treatment. The present invention has no special requirements for the washing and centrifuging, and methods known in the art may be used. For example, the present invention uses deionized water for washing and a centrifuge for centrifugation, and the centrifugation conditions include at least: a centrifuge speed of 6000-7000 rpm and a centrifugation time of 6-10 min.

[0043] Preferably, in step (3), the drying treatment conditions include: temperature of 70-90° C. and time of 3-5 h.

[0044] Preferably, in step (3), the calcination treatment conditions include: temperature of 810-900° C. and time of 1.5-2.5 h.

[0045] More preferably, in step (3), the calcination treatment conditions include: a temperature of 810-850° C. The inventors of the present invention have found that in this preferred embodiment, the particle size of the upconversion luminescent material provided by the present invention is smaller and the degree of crystallinity is higher.

[0046] As mentioned above, the second aspect of the present invention provides an up-conversion luminescent material prepared by the method described in the first aspect.

[0047] Preferably, the average particle size of the upconversion luminescent material is 40 nm to 210 nm.

[0048] As mentioned above, the third aspect of the present invention provides the use of the upconversion luminescent material described in the second aspect in biomedical diagnosis, information encryption storage or solar cells.

[0049] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the instruments, reagents, materials, etc. involved are all conventional instruments, reagents, materials, etc., which can be obtained through regular commercial channels. In particular, unless otherwise specified, the reagents used are all commercially available analytical grade products.

[0050] Ytterbium salt: Ytterbium (III) nitrate pentahydrate, purchased from Adamas Beta (Shanghai) Chemical Reagent Co., Ltd., analytical grade;

[0051] Ammonium molybdate tetrahydrate: purchased from Adamas Beta (Shanghai) Chemical Reagent Co., Ltd., analytical grade;

[0052] Rare earth metal salts: Erbium nitrate, purchased from Adamas Beta (Shanghai) Chemical Reagent Co., Ltd., analytical grade;

[0053] Hydrothermal reactor: 50 mL, model CYKH-50ML, purchased from Xi'an Changyi Instrument Equipment Co., Ltd.

[0054] Example 1

[0055] (1) stirring an ytterbium salt solution, an ammonium molybdate tetrahydrate solution, and a rare earth metal salt solution to obtain an intermediate I;

[0056] (2) subjecting the intermediate I to a hydrothermal reaction in a hydrothermal reactor to obtain intermediate II;

[0057] (3) The intermediate II was washed with deionized water and then centrifuged (the centrifuge speed was 6750 rpm and the centrifugation time was 7 min). The above operation was repeated 3 times, and the obtained precipitate was dried and calcined in sequence to obtain the upconversion luminescent material S1.

[0058] The specific raw material dosages and concentrations and process parameters of Example 1 are shown in Table 1. Unless otherwise specified, the remaining examples are carried out using the same process as Example 1, except that the raw material concentrations and dosages and process parameters used are different. Please refer to Table 1 for details.

[0059] Table 1

[0060] Example 1 Example 2 Step (1) <![CDATA[The concentration (mol / L) of Yb in ytterbium salt solution]]> 3+ > 0.6 0.5 Amount of ytterbium salt solution / mL 7.84 8.1 Concentration of ammonium molybdate tetrahydrate solution (mol / L) 0.3 0.32 Dosage of ammonium molybdate tetrahydrate solution / mL 12 10 Concentration of rare earth ions in rare earth metal salt solution (mol / L) 0.6 0.7 Amount of rare earth metal salt solution / mL 0.16 0.4 First stirring Temperature / ℃ 25 30 Time / h 2 1.5 Step (2) hydrothermal reaction Temperature / ℃ 140 130 Time / h 2 2.5 Step (3) Drying Temperature / ℃ 85 75 Time / h 3.5 4 Calcination treatment Temperature / ℃ 830 820 Time / h 1.5 2 name S1 S2

[0061] Example 3

[0062] This example is carried out using a method similar to that of Example 1, except that in this example, the concentration of the ammonium molybdate tetrahydrate solution is adjusted to 0.35 mol / L, and the volume used remains unchanged to obtain the upconversion luminescent material S3.

[0063] Example 4

[0064] This embodiment is carried out using a method similar to that of embodiment 1, except that the temperature of the hydrothermal reaction in step (2) of this embodiment is adjusted to 170° C. to obtain the up-conversion luminescent material S4.

[0065] Comparative Example 1

[0066] Step (1) is the same as in Example 1;

[0067] Step (2): The intermediate I was reacted in a beaker in a water bath at 80°C for 2 h to obtain the intermediate II;

[0068] Step (3) is the same as in Example 1 to obtain the up-conversion luminescent material DS1.

[0069] Comparative Example 2

[0070] This comparative example was carried out using a method similar to that of Example 1, except that the concentration of rare earth ions in the rare earth metal salt solution in this comparative example was adjusted to 3.2 mol / L, and the volume used remained unchanged to obtain the upconversion luminescent material DS2.

[0071] Comparative Example 3

[0072] This comparative example was carried out in a similar manner to Example 1, except that the Yb 3+ The concentration was adjusted to 4 mol / L, and the volume remained unchanged to obtain the upconversion luminescent material DS3.

[0073] Test Case

[0074] The present invention exemplarily selects the up-conversion luminescent material S1 obtained in the above example to perform morphology testing using a scanning electron microscope. The results are shown in FIG. Figure 1 .

[0075] The phase composition of the up-conversion luminescent materials S1, S2, S3, S4, DS1, DS2 and DS3 obtained in the above examples was analyzed by X-ray diffraction. Figure 2 . Figure 2 The left part is the X-ray diffraction spectrum of S1, S2, S3, and S4, and the right part is the X-ray diffraction spectrum of DS1, DS2, and DS3.

[0076] The upconversion luminescent material obtained in the above example was optically tested using a fluorescence spectrophotometer under the following test conditions: at a temperature of 37°C to 397°C and excited by a 980nm laser. The temperature-dependent upconversion luminescence spectrum of the upconversion luminescent material provided by the present invention under 980nm excitation is shown in FIG. Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 and Figure 9 .

[0077] from Figure 1 It can be seen that the average particle size of the up-conversion luminescent material prepared by the method provided by the present invention is 117 nm, and the shape is blocky.

[0078] from Figure 2 It can be seen that the up-conversion luminescent materials S1, S2, S3 and S4 provided by the present invention have a high degree of crystallinity and no impurities appear. By comparing the up-conversion luminescent materials with the standard cards, it can be seen that the up-conversion luminescent materials S1, S2, S3, S4 and DS2 have high crystallinity, the DS3 material has a low crystallinity, and DS1 has no diffraction peak.

[0079] from Figure 3 It can be seen that the upconversion luminescent material S2 has green light emission peaks at wavelengths of 524nm and 559nm, which is mainly due to the erbium ions in the luminescent center. 2 H 11 / 2 → 4 I 15 / 2 and 4 S 3 / 2 → 4 I 15 / 2 It can also be seen from the figure that increasing the temperature from 37°C to 377°C does not affect the luminescence intensity of the conversion luminescent material S2. The highest emission intensity is at 377°C, and its luminescence intensity continues to increase with increasing temperature, indicating that the material has great application potential in high temperature areas.

[0080] from Figure 4 It can be seen that the up-conversion luminescent material S2 has a green light emission peak at a wavelength of 450nm to 700nm, which is mainly due to the erbium ion in the luminescent center. 2 H 11 / 2 → 4 I 15 / 2 、 4 S 3 / 2 → 4 I 15 / 2 and 4 F 9 / 2 → 4 I 15 / 2 It can also be seen from the figure that increasing the temperature from 37℃ to 377℃ does not affect the luminescence intensity of the conversion luminescent material S2. It has the highest emission intensity at 377℃, and its luminescence intensity continues to increase with the increase of temperature, indicating that the material has great application potential in high temperature areas.

[0081] from Figure 5 It can be seen that the up-conversion luminescent material S3 has a green light emission peak at a wavelength of 450nm to 700nm, which is mainly due to the erbium ion in the luminescent center.2 H 11 / 2 → 4 I 15 / 2 、 4 S 3 / 2 → 4 I 15 / 2 and 4 F 9 / 2 → 4 I 15 / 2 It can also be seen from the figure that increasing the temperature from 37°C to 377°C does not affect the luminescence intensity of the conversion luminescent material S3. The highest emission intensity is at 377°C, and its luminescence intensity continues to increase with increasing temperature, indicating that the material has great application potential in high temperature areas.

[0082] from Figure 6 It can be seen that the upconversion luminescent material S4 has green light emission peaks at wavelengths of 524nm and 559nm, which is mainly due to the erbium ions in the luminescent center. 2 H 11 / 2 → 4 I 15 / 2 and 4 S 3 / 2 → 4 I 15 / 2 It can also be seen from the figure that the highest emission intensity is at 277℃, indicating that the material has great application potential in high temperature areas.

[0083] from Figure 7 It can be seen that the emission peak of the up-conversion luminescent material DS1 is not detected, indicating that the up-conversion luminescent material prepared without adopting the method provided by the present invention does not have luminescent properties.

[0084] from Figure 8 It can be seen that the emission peak of the up-conversion luminescent material DS2 is not detected, indicating that the up-conversion luminescent material prepared without adopting the method provided by the present invention does not have luminescent properties.

[0085] from Figure 9 It can be seen that the upconversion luminescent material DS3 has a green light emission peak at 450nm~700nm, which is mainly due to the erbium ion in the luminescent center. 2 H 11 / 2 → 4 I 15 / 2 and 4 S 3 / 2 → 4 I 15 / 2 It can also be seen from the figure that when the temperature rises from 37℃ to 377℃, the highest emission intensity is at 37℃, and the luminescence intensity of the upconversion luminescent material DS3 decreases with the increase of temperature.

[0086] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing an upconversion luminescent material, characterized in that: The method includes: (1) A ytterbium salt solution, an ammonium molybdate tetrahydrate solution, and a rare earth metal salt solution are first stirred to obtain an intermediate I; the rare earth metal salt in the rare earth metal salt solution is an erbium salt; (2) subjecting the intermediate I to a hydrothermal reaction in a hydrothermal reactor to obtain the intermediate II; the hydrothermal reaction conditions include: a temperature of 130-150° C. and a time of 1.5-2.5 h; (3) drying and calcining the intermediate II in sequence to obtain the upconversion luminescent material; the calcination conditions include: temperature of 810-900° C. and time of 1.5-2.5 h; In step (1), in the mixed solution at the start of the first stirring, Yb 3+ The concentration of is 0.2-0.32 mol / L, the concentration of ammonium molybdate tetrahydrate is 0.15-0.22 mol / L, and the concentration of rare earth metal ions is 0.004-0.02 mol / L; Yb in the ytterbium salt solution 3+ The molar ratio of the amount of ammonium molybdate tetrahydrate in the ammonium molybdate tetrahydrate solution calculated on a dry basis is 1:0.7-0.9; The Yb in the ytterbium salt solution 3+ and the total molar amount of rare earth metal ions in the rare earth metal salt solution are used as the basis, the Yb in the ytterbium salt solution 3+ The amount of rare earth metal ions in the rare earth metal salt solution is 92-98 mol%.

2. The method according to claim 1, wherein In step (1), the Yb in the ytterbium salt solution 3+ The concentration is 0.5-0.7mol / L.

3. The method according to claim 1, wherein In step (1), the concentration of the ammonium molybdate tetrahydrate solution is 0.25-0.35 mol / L.

4. The method according to claim 1, wherein In step (1), the concentration of rare earth metal ions in the rare earth metal salt solution is 0.5-0.7 mol / L.

5. The method according to claim 1, wherein In step (1), the first stirring conditions include: temperature of 10-30° C. and time of 1.5-2.5 h.

6. The method according to claim 1, wherein In step (3), the drying conditions include: temperature of 70-90°C and time of 3-5 hours.

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