A boron phosphate near-infrared second window fluorescence material, its preparation method and applications

Abstract

The present invention discloses a boron phosphate near-infrared second-region fluorescent material, its preparation method and application. The chemical composition of the fluorescent material is Ba3BP 1‑x O7:xMn 5+ , where Mn 5+ is the activator, and x = 0.001 to 0.03 in the formula. The preparation method adopted in the present invention is the high-temperature solid-phase method. Weigh the Ba source, B source, P source, and Mn source according to the stoichiometric ratio. After mixing the raw materials evenly, sinter them at high temperature in an air atmosphere, and naturally cool them to room temperature to obtain the sintered product. Grind it to obtain the boron phosphate near-infrared second-region fluorescent material. The fluorescent material of the present invention can be effectively excited by a commercial red LED chip and form a narrow-band emission in the near-infrared second region. This boron phosphate near-infrared second-region fluorescent material has good physical and chemical stability, is simple to prepare, does not require an oxidizing atmosphere, and can form Mn 5+ in the air, and has a relatively low cost and is easy to be mass-produced industrially.

Description

Technical Field

[0001] The present invention relates to the technical field of near-infrared fluorescent materials, and particularly relates to a borophosphate near-infrared second-region fluorescent material, a preparation method thereof, and an application thereof. Technical Background

[0002] Generally speaking, near-infrared light is divided into three bands, the NIR-I region (700 - 1000 nm), the NIR-II region (1000 - 1700 nm), and the scarcely developed NIR-III region (1700 - 2500 nm). Compared with the NIR-I region, the NIR-II region is less prone to scattering and absorption, so the light in the NIR-II region is more suitable for long-distance transmission. For NIR-II region fluorescence, narrow-band emission is less prone to scattering and absorption than broadband emission, which is more conducive to depth imaging and long-distance communication. However, spin and parity forbiddenness result in a small absorption cross-section and relatively low fluorescence efficiency for rare-earth ion-doped fluorescent materials. In order to be used in depth imaging and long-distance communication, stable and efficient NIR-II region phosphors need to be developed.

[0003] Due to the tetrahedral coordination with low symmetry and spin-allowed excitation transitions, transition metal Mn 5+ ions exhibit a larger absorption cross-section than rare-earth ions, and its 3 A2→ 3 T1( 3 F) transition forms a strong absorption spanning the entire first biological window. The strong crystal field formed by short bond lengths and high valence states enables Mn 5+ to form a strong narrow-band emission in the near-infrared II region (resulting from 1 E→ 3 A2 transition), and the highest quantum efficiency exceeding 40% is obtained in Ba3(PO4)2:Mn 5+ . However, compared with Mn 2+ and Mn 4+ , Mn 5+ is metastable, which poses more restrictions on the structure and composition of the Mn 5+ -doped matrix, and affects the fluorescence efficiency of Mn 5+ by reducing effective doping and multi-valence state energy transfer, etc. Therefore, finding a stable matrix for Mn 5+ , improving the effective doping amount of Mn 5+ and reducing the formation of other valence state Mn ions, thereby improving the luminescence performance of the Mn 5+ -doped narrow-band near-infrared II region fluorescent material, promoting the application of Mn 5+ in imaging and communication, and reducing the dependence on rare-earth materials has very important practical significance. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to overcome the metastable characteristics of Mn 5+ and provide a novel borophosphate near-infrared second-region fluorescent material with simple preparation conditions, stable Mn 5+ , high efficiency fluorescence, and its preparation method and application.

[0005] The purpose of the present invention is achieved through the following solutions:

[0006] A borophosphate near-infrared second-region fluorescent material, with a chemical composition of Ba3BP 1-x O7:xMn 5+ , where Mn 5+ is the activator, and in the formula x = 0.001 to 0.03.

[0007] Preferably, x = 0.0025 to 0.03.

[0008] More preferably, x = 0.005.

[0009] Preferably, the fluorescent material can be excited by ultraviolet-visible light of 300 - 450 nm and visible-near infrared light in the range of 450 - 890 nm, and emits near-infrared light in the range of 1100 - 1400 nm.

[0010] The preparation method of the above-mentioned borophosphate near-infrared second-region fluorescent material, the preparation method is the high-temperature solid-phase method.

[0011] Preferably, it includes the following steps:

[0012] Weigh the Ba source, B source, P source, and Mn source according to the stoichiometric ratio. After mixing the raw materials evenly, sinter them at high temperature in an air atmosphere, and naturally cool them to room temperature to obtain a sintered product, and grind it to obtain the borophosphate near-infrared second-region fluorescent material.

[0013] More preferably, the Ba source is BaCO3, the B source is H3BO3, the P source is NH4H2PO4, and the Mn source is MnCO3.

[0014] More preferably, the molar ratio of P to Mn in the P source and Mn source is 0.001 - 0.03:0.97 - 0.999;

[0015] More preferably, the molar ratio of Ba, B, P+Mn in the Ba source, B source, P source, and Mn source is 3:1:1.

[0016] More preferably, the conditions for the high-temperature sintering are: temperature 1200 - 1300 °C, sintering time 2 - 8 h, and the number of sintering times is 1 time.

[0017] More preferably, the conditions for the high-temperature sintering are as follows: temperature 1250 °C, sintering time 5 h.

[0018] Use of the above-mentioned boron phosphate near-infrared second-region fluorescent material in the preparation of a narrow-band near-infrared fluorescence conversion type LED device.

[0019] Mn of the present invention 5+ doped boron phosphate near-infrared second-region fluorescent material, with Ba3BPO7 as the matrix and Mn 5+ as the activator, with the chemical composition of Ba3BPO7:Mn 5+ , Mn 5+ partially substituting P 5+ , Mn 5+ The molar doping concentration of which is 0.1%-3%. This fluorescent material can be excited by ultraviolet-visible light in the range of 300-450 nm and visible-near-infrared light in the range of 450-890 nm, and emits near-infrared light in the range of 1100-1400 nm.

[0020] Compared with the prior art, the present invention has the following advantages and effects:

[0021] (1) The matrix material Ba3BPO7 of the present invention does not contain precious metal elements such as rare earth, Ti or Ge, the raw materials are cheap and easily available, and the cost is low.

[0022] (2) The preparation of the boron phosphate near-infrared second-region fluorescent material of the present invention is simple and does not require calcination in an oxygen atmosphere to obtain Mn 5+ .

[0023] (3) Compared with the reported Mn 5+ doped near-infrared second-region fluorescent materials such as Ba3(PO4)2, etc., the absorption efficiency in the visible light region is higher, and the emitted near-infrared red light is stronger. Description of the Drawings

[0024] Figure 1 is the XRD powder diffraction pattern and the calculated diffraction pattern of the boron phosphate near-infrared second-region fluorescent material Ba3BPO7:0.005Mn of Example 2 of the present invention 5+ ;

[0025] Figure 2 is the room temperature absorption, excitation and emission spectra of the boron phosphate near-infrared second-region fluorescent material Ba3BPO7:0.005Mn of Example 2 of the present invention 5+ ;

[0026] Figure 3 is the quantum efficiency of the XRD powder of the boron phosphate near-infrared second-region fluorescent material Ba3BPO7:0.005Mn of Example 2 of the present invention 5+ ;

[0027] Figure 4 is the near-infrared second near-infrared fluorescent material Ba3BPO7:Mn of Embodiment 2 of the present invention 5+ and the phosphate near-infrared second near-infrared fluorescent material Ba3(PO4)2:Mn of Comparative Example 1 5+ , the boron phosphate orange fluorescent material Ba3BPO7:Sm of Comparative Example 2 3+ and the phosphate orange fluorescent material Ba3(PO4)2:Sm of Comparative Example 3 3+ luminance intensity comparison chart. Specific embodiments

[0028] The technical solution of the present invention will be further described below in conjunction with specific embodiments and drawings. The following embodiments are only for strengthening the description of the technical solution of the present invention and are not used as a limitation on the scope of the claimed invention. Any improvement and equivalent replacement based on the present invention are within the protection scope of the present invention.

[0029] The Mn described in the present invention 5+ The preparation method of the doped boron phosphate near-infrared second near-infrared fluorescent material is as follows: using the high-temperature solid-phase method, a certain amount of BaCO3, H3BO3, NH4H2PO4 and MnCO3 are weighed according to the stoichiometric ratio, and the raw materials are mixed evenly and ground thoroughly for 20 min to obtain raw material powder. The raw material powder is placed in a corundum crucible and sintered in an air atmosphere at 1250 °C for 5 hours, and then naturally cooled to room temperature to obtain a sintered product, which is ground to obtain Mn 5+ doped boron phosphate near-infrared second near-infrared fluorescent material.

[0030] Example 1

[0031] A kind of Mn 5+ doped boron phosphate near-infrared second near-infrared fluorescent material (Ba3BPO7:0.0025Mn 5+ ) preparation:

[0032] Precisely weigh 3 mmol BaCO3, 1 mmol H3BO3, 0.9975 mmol NH4H2PO4 and 0.0025 mmol MnCO3, mix the raw materials evenly and grind them thoroughly for 20 min to obtain raw material powder; place the raw material powder in a corundum crucible and sinter it in an air atmosphere at 1250 °C for 5 hours, and then naturally cool it to room temperature to obtain a sintered product, which is ground to obtain the boron phosphate near-infrared second near-infrared fluorescent material.

[0033] The absorption spectrum, excitation spectrum and emission spectrum of this example are the same as Figure 2Similarly, the fluorescent material can be excited by ultraviolet-visible light in the range of 300 - 450 nm and visible-near-infrared light in the range of 450 - 890 nm, and emits near-infrared light in the range of 1100 - 1400 nm.

[0034] Example 2

[0035] A kind of Mn 5+ doped borophosphate near-infrared second-region fluorescent material (Ba3BPO7:0.005Mn 5+ ) Preparation: Accurately weigh 3 mmol BaCO3, 1 mmol H3BO3, 0.995 mmol NH4H2PO4 and 0.005 mmol MnCO3. Mix the raw materials evenly and grind them thoroughly for 20 min to obtain raw material powder; place the raw material powder in a corundum crucible and sinter it in an air atmosphere at 1250 °C for 5 hours, and then cool it naturally to room temperature to obtain a sintered product. Grind it to obtain the borophosphate near-infrared second-region fluorescent material.

[0036] Figure 1 XRD powder diffraction pattern of the Ba3BPO7:0.005Mn 5+ fluorescent material prepared for this example. The diffraction peaks of the sample correspond exactly to the spectrum calculated from the cif file of Ba3BPO7, and no diffraction peak signals of any impurity phases are observed, indicating that the synthesized Ba3BPO7:0.005Mn Figure 1 fluorescent material is a pure phase. 5+

[0037] Figure 2 Absorption spectrum, excitation spectrum and emission spectrum of the Ba3BPO7:0.005Mn 5+ fluorescent material prepared for this example. As shown in the figure, the fluorescent material can be excited by ultraviolet-visible light in the range of 300 - 450 nm and visible-near-infrared light in the range of 450 - 890 nm, and emits near-infrared light in the range of 1100 - 1400 nm.

[0038] Figure 3 Quantum efficiency of the Ba3BPO7:0.005Mn 5+ fluorescent material prepared for this example. Under the excitation of 660 nm red light, the fluorescent material obtains an internal quantum efficiency of 50.6% and an absorption efficiency of 60.3%.

[0039] Example 3

[0040] A kind of Mn 5+ doped borophosphate near-infrared second-region fluorescent material (Ba3BPO7:0.01Mn 5+Preparation: Accurately weigh 3 mmol of BaCO3, 1 mmol of H3BO3, 0.99 mmol of NH4H2PO4, and 0.01 mmol of MnCO3. Mix the raw materials evenly and grind them thoroughly for 20 minutes to obtain raw material powder. Place the raw material powder in a corundum crucible and sinter it in an air atmosphere at 1250 °C for 5 hours. Naturally cool it to room temperature to obtain a sintered product, and grind it to obtain a borophosphate near-infrared second-region fluorescent material.

[0041] The absorption spectrum, excitation spectrum, and emission spectrum of this example are similar to Figure 2 those. This fluorescent material can be excited by ultraviolet-visible light in the range of 300 - 450 nm and visible-near-infrared light in the range of 450 - 890 nm, and emits near-infrared light in the range of 1100 - 1400 nm.

[0042] Example 4

[0043] A Mn 5+ -doped borophosphate near-infrared second-region fluorescent material (Ba3BPO7:0.02Mn 5+ ) Preparation: Accurately weigh 3 mmol of BaCO3, 1 mmol of H3BO3, 0.98 mmol of NH4H2PO4, and 0.02 mmol of MnCO3. Mix the raw materials evenly and grind them thoroughly for 20 minutes to obtain raw material powder. Place the raw material powder in a corundum crucible and sinter it in an air atmosphere at 1250 °C for 5 hours. Naturally cool it to room temperature to obtain a sintered product, and grind it to obtain a borophosphate near-infrared second-region fluorescent material.

[0044] The absorption spectrum, excitation spectrum, and emission spectrum of this example are similar to Figure 2 those. This fluorescent material can be excited by ultraviolet-visible light in the range of 300 - 450 nm and visible-near-infrared light in the range of 450 - 890 nm, and emits near-infrared light in the range of 1100 - 1400 nm.

[0045] Example 5

[0046] A Mn 5+ -doped borophosphate near-infrared second-region fluorescent material (Ba3BPO7:0.03Mn 5+ ) Preparation: Accurately weigh 3 mmol of BaCO3, 1 mmol of H3BO3, 0.97 mmol of NH4H2PO4, and 0.03 mmol of MnCO3. Mix the raw materials evenly and grind them thoroughly for 20 minutes to obtain raw material powder. Place the raw material powder in a corundum crucible and sinter it in an air atmosphere at 1250 °C for 5 hours. Naturally cool it to room temperature to obtain a sintered product, and grind it to obtain a borophosphate near-infrared second-region fluorescent material.

[0047] The absorption spectrum, excitation spectrum, and emission spectrum of this example are similar to Figure 2 those. This fluorescent material can be excited by ultraviolet-visible light in the range of 300 - 450 nm and visible-near-infrared light in the range of 450 - 890 nm, and emits near-infrared light in the range of 1100 - 1400 nm.

[0048] The comparison of the full width at half maximum and relative integral intensity of the fluorescent materials synthesized in Examples 1 - 5 and Comparative Examples 1 - 3 is shown in Table 1 below (the excitation wavelength of the fluorescent materials synthesized in Examples 1 - 5 is 660 nm; the excitation wavelength of the fluorescent material synthesized in Comparative Example 1 is 690 nm; the excitation wavelength of the fluorescent material synthesized in Comparative Example 2 is 404 nm, and the excitation wavelength of the fluorescent material synthesized in Comparative Example 3 is 402 nm, and the power of the excitation light is the same).

[0049] Table 1

[0050] The Ba3BPO7:Mn 5+ near-infrared II-region fluorescent material of borophosphate synthesized in the examples and the Ba3(PO4)2:Mn 5+ near-infrared II-region fluorescent material of phosphate synthesized in the comparative examples, Ba3BPO7:Sm 3+ orange fluorescent material of borophosphate and Ba3(PO4)2:Sm 3+ orange fluorescent material of phosphate in terms of the full width at half maximum and relative integral intensity.

[0051] Sample number Chemical formula Full width at half maximum (nm) Relative integrated intensity Example 1 <![CDATA[Ba3BPO7:0.0025Mn 5+ > 24 0.87 Example 2 <![CDATA[Ba3BPO7:0.005Mn 5+ > 24 1 Example 3 <![CDATA[Ba3BPO7:0.01Mn 5+ > 26 0.92 Example 4 <![CDATA[Ba3BPO7:0.02Mn 5+ > 25.5 0.83 Example 5 <![CDATA[Ba3BPO7:0.03Mn 5+ > 25.5 0.81 Comparative example 1 <![CDATA[Ba3(PO4)2:0.02Mn 5+ > 6 0.48 Comparative example 2 <![CDATA[Ba3BPO7:0.03Sm 3+ > 50 0.064 Comparative example 3 <![CDATA[Ba3(PO4)2:0.06Sm 3+ > 3 0.38

[0052] The Ba3BPO7:Mn 5+ near-infrared II-region fluorescent material of borophosphate synthesized in Example 2 and the Ba3(PO4)2:Mn 5+ near-infrared II-region fluorescent material of phosphate synthesized in Comparative Example 1, Ba3BPO7:Sm 3+ orange fluorescent material of borophosphate synthesized in Comparative Example 2 and Ba3(PO4)2:Sm 3+ orange fluorescent material of phosphate synthesized in Comparative Example 3 in terms of the luminous intensity comparison is shown in Figure 4 .

[0053] It can be seen that the Ba3BPO7:Mn 5+ near-infrared II-region fluorescent material of borophosphate synthesized by the above high-temperature solid-phase method is more excellent than Ba3(PO4)2:Mn 5+ in terms of fluorescence quantum yield, specifically, the integral luminous intensity of the near-infrared II-region fluorescent material of borophosphate is higher. In the present invention, by doping Mn 5+ into Ba3BPO7 as the matrix, a near-infrared II-region fluorescent material with a relatively wide full width at half maximum and high luminous intensity is obtained. On the contrary, Ba3(PO4)2:Sm synthesized by the high-temperature solid-phase method3+ is more excellent than Ba3BPO7:Sm in terms of fluorescence quantum yield 3+ Specifically, the luminescence intensity of the phosphate orange fluorescent material is higher. Comparative experiments show that borophosphate fluorescent materials are not necessarily superior to phosphate fluorescent materials, and both the matrix and doped ions affect the luminescence performance.

[0054] The synthesis methods of the comparative fluorescent materials in the above table are introduced in detail below.

[0055] Comparative Example 1

[0056] Ba3(PO4)2:Mn 5+ The synthesis method of the phosphate near-infrared second-region fluorescent material is as follows:

[0057] Accurately weigh 3 mmol of BaCl2, 1.98 mmol of NH4H2PO4, and 0.02 mmol of MnCO3. Mix the raw materials evenly and grind them thoroughly for 20 minutes to obtain raw material powder; place the raw material powder in a corundum crucible and calcine it in an air atmosphere at 400 °C for 3 hours, then sinter it in an air atmosphere at 1000 °C for 12 hours, and naturally cool it to room temperature to obtain a sintered product. Grind it to obtain Ba3(PO4)2:Mn 5+ Phosphate near-infrared second-region fluorescent material.

[0058] According to the literature [Cao RP, et al. Near-infrared emission Ba3(PO4)2:Mn 5+ phosphor and potential application in vivo fluorescence imaging[J]. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014, 128, 671.], this is the optimal sintering scheme and optimal doping concentration for this fluorescent powder system, and the luminescence performance is the best.

[0059] Comparative Example 2

[0060] Ba3BPO7:Sm 3+ The synthesis method of the borophosphate orange fluorescent material is as follows:

[0061] Accurately weigh 2.94 mmol of BaCO3, 1 mmol of H3BO3, 1 mmol of NH4H2PO4, 0.015 mmol of Sm2O3 and 0.015 mmol of Na2CO3. Mix the raw materials evenly and grind them thoroughly for 20 minutes to obtain the raw material powder. Place the raw material powder in a corundum crucible and sinter it in an air atmosphere at 1150 °C for 15 hours. Naturally cool it to room temperature to obtain the sintered product, and grind it to obtain the borophosphate orange fluorescent material.

[0062] According to the literature [Zhang J, Chen C, Zhang XG, et al. Photoluminescence properties of Sm3+ doped barium borophosphate phosphors [J]. Optik, 2018, 158, 1499.], this is the optimal sintering scheme and optimal doping concentration for this phosphor system, with the best luminescence performance.

[0063] Comparative Example 3

[0064] Ba3(PO4)2:Sm 3+ The synthesis method of the phosphate orange fluorescent material is as follows:

[0065] Accurately weigh 0.75 g of Ba(NO3)2, 0.0014 g of LiNO3, 0.027 g of Sm(NO3)3·6H2O and 0.05 g of C 19 H 42 BrN is dissolved in 50 ml of deionized water to form solution A. Weigh 0.26 g of NH4H2PO4 and dissolve it in 50 ml of deionized water to form solution B. Slowly add solution B dropwise to solution A and stir for 10 minutes. Add 10 M NaOH solution to adjust the alkalinity of the reaction medium to pH ~ 13, and stir these solutions at room temperature for 10 minutes. Heat the reaction solution to 80 °C, keep it in a water bath for 8 hours, cool it to room temperature, centrifuge the final solution product, wash it successively with ethanol and deionized water, and dry it in vacuo at 60 °C to obtain the phosphate orange fluorescent material.

[0066] According to the literature [Babu Ballipalli C, Rajavaram R, Naresh V, et al. Synthesis and photoluminescent characteristics of Sm 3+-doped Ba3(PO4)2 phosphor hierarchical architectures[J]. Materials Science and Engineering: B, 2021, 264: 114979.], which is the optimal preparation scheme and optimal doping concentration of this phosphor system, and has the optimal luminescence performance.

[0067] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A boron phosphate near-infrared second-region fluorescent material, characterized in that: The chemical composition is Ba3BP 1-x O7:xMn 5+ , where Mn 5+ is the activator, and in the formula x = 0.001 to 0.

03.

2. The near-infrared second-region fluorescent material of borophosphate according to claim 1, characterized in that, x＝0.0025～0.03。 3. The near-infrared second-region fluorescent material based on boron phosphate according to claim 2, wherein x＝0.005。 4. The near-infrared second-region fluorescent material of borophosphate according to claim 1, characterized in that, The fluorescent material can be excited by ultraviolet-visible light in the range of 300-450 nm and visible-near-infrared light in the range of 450-890 nm, and emits near-infrared light in the range of 1100-1400 nm.

5. The preparation method of the borophosphate near-infrared second-region fluorescent material according to any one of claims 1 to 4, characterized in that, The preparation method is the high-temperature solid-phase method.

6. The preparation method according to claim 5, characterized in that, It includes the following steps: Weigh the Ba source, B source, P source, and Mn source according to the stoichiometric ratio. After mixing the raw materials evenly, sinter them at high temperature in an air atmosphere, and naturally cool them to room temperature to obtain a sintered product. Grind it to obtain the near-infrared second-region fluorescent material of boron phosphate.

7. The preparation method according to claim 6, characterized in that, The Ba source is BaCO3, the B source is H3BO3, the P source is NH4H2PO4, and the Mn source is MnCO3.

8. The preparation method according to claim 6, wherein The molar ratio of P to Mn in the P source and Mn source is 0.001-0.03:0.97-0.999; The molar ratio of Ba, B, P+Mn in the Ba source, B source, P source, and Mn source is 3:1:

1.

9. The preparation method according to claim 6, characterized in that, The conditions for the high-temperature sintering are: temperature 1200-1300 °C, sintering time 2-8 h, and the number of sintering times is 1 time.

10. Application of the near-infrared second-region fluorescent material of boron phosphate according to any one of claims 1 to 4 in the preparation of a narrow-band near-infrared fluorescence conversion type LED device.

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