A Cr 3+ Hexafluoride-doped near-infrared fluorescent material and preparation method and application thereof

Abstract

The present invention discloses a Cr 3+ -doped hexafluoride near-infrared fluorescent material and a preparation method thereof. The chemical composition formula of the material is: K2LiMF6:xCr 3+ , where M is one of Al, Ga or In, and x is the molar percentage coefficient of the doped Cr 3+ ions relative to the M 3+ ions, and 0 < x ≤ 0.09. The fluorescent material K2LiMF6:xCr 3+ disclosed by the present invention has a stable cubic double perovskite structure and can achieve broadband near-infrared emission with ultra-high thermal stability under visible light excitation. It can be used to prepare a broadband near-infrared light source device to realize the functions of night vision and vein imaging. The preparation method of the K2LiMF6:xCr 3+ material disclosed by the present invention is a hydrothermal method, which is carried out in an aqueous solution. This method has simple operation and mild reaction conditions and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the field of near-infrared fluorescent materials, and in particular to a Cr 3+ Hexafluoride-doped near-infrared fluorescent material, preparation method and application thereof. Background Art

[0002] As near-infrared spectroscopy technology has been widely used in plant lighting, food quality testing, medical diagnosis, night vision and anti-counterfeiting, near-infrared fluorescence converted LED (NIR pc-LED) has the characteristics of small size, high efficiency, adjustable wavelength and broadband emission compared with traditional near-infrared light sources. It has very obvious advantages in the application of portable near-infrared detection equipment and is therefore receiving more and more attention.

[0003] Transition Metal Cr 3+ With Mn 2+ 、Ni 2+ , Yb 3+ Compared with the conventional octahedral nanostructured carbon nanotubes, it is easy to generate broadband near-infrared emission under the weak crystal field of the octahedron. It also has the advantages of matching the excitation area with the blue light chip, adjustable broadband near-infrared emission range and high quantum yield. 3+ Doped near-infrared phosphors have been developed and reported one after another. For example, LiScP 2 O 7 :Cr 3+ , ScBO 3 :Cr 3 + , ScF 3 :Cr 3+ , Na 3 S F 6 :Cr 3+ However, although oxides have a large half-peak width, their thermal stability is difficult to reach more than 80%, which cannot meet the application of near-infrared light sources. Fluorides have low phonon energy and relatively weak electron-phonon coupling effect, which makes Cr 3+ Fluoride-doped near-infrared fluorescent materials can have excellent thermal stability. However, in the preparation process of fluoride phosphors, most researchers use highly volatile and corrosive hydrofluoric acid as the reaction solution. Improper use can cause harm to the human body and pollute the environment, which is not conducive to large-scale industrial application.

[0004] Therefore, it is of great significance to provide a green and mild synthetic method to prepare broadband near-infrared fluorescent materials with excellent thermal stability to expand their large-scale applications in the near-infrared field. Summary of the invention

[0005] The present invention aims to provide a Cr 3+Hexafluoride-doped near-infrared fluorescent material and preparation method thereof, the fluorescent material K provided by the invention 2 LiMF 6 :xCr 3+ (M=Al,Ga,In) can be excited by visible light to achieve broadband near-infrared emission, and has good thermal stability at 150°C. The near-infrared light source device prepared by it can achieve functions such as night vision and vein imaging. The present invention adopts a hydrothermal method to prepare in an aqueous solution, and the reaction conditions are mild, which effectively reduces the risk of experimental safety accidents, and the preparation process is simple, which is conducive to its large-scale production.

[0006] The invention discloses a Cr 3+ Doped hexafluoride near-infrared fluorescent material, the chemical composition formula of the material is: K 2 LiMF 6 :xCr 3+ , where M is any one of Al, Ga or In, and x is doped Cr 3+ Ion relative M 3+ The molar percentage coefficient of the ion, 0 <x≤0.09。

[0007] Preferably, the material is a cubic double perovskite crystal structure.

[0008] Preferably, the material can be excited by visible light to emit near-infrared light, the wavelength of visible light is 400-700 nm, and the wavelength of near-infrared light is 650-1000 nm.

[0009] Preferably, the visible light is blue light and red light.

[0010] The present invention also discloses a Cr 3+ The preparation method of the hexafluoride-doped near-infrared fluorescent material comprises the following steps:

[0011] Step 1: weighing raw materials according to the stoichiometric ratio of the chemical composition formula: potassium bifluoride, lithium salt, M salt, and ammonium hexafluorochromate; the lithium salt is any one or a combination of lithium chloride and lithium nitrate; the M salt is any one or a combination of M chloride and nitrate;

[0012] Step 2: dissolving potassium bifluoride, lithium salt and M salt in water to form an aqueous solution, stirring the solution for the first time at room temperature, adding ammonium hexafluorochromate to the aqueous solution, stirring the solution for the second time at room temperature to obtain solution A;

[0013] Step 3: Heat the solution A obtained in step 2 in a sealed manner to obtain a precipitate;

[0014] Step 4: Wash, centrifuge and dry the precipitate to obtain K 2 LiMF 6 :xCr3+ .

[0015] Preferably, in step 1, the weighed raw materials and the chemical quantities are as follows: the amount of potassium bifluoride is 0.0225 mol, the lithium salt is lithium chloride, the amount of lithium chloride is 0.0025 mol, the M salt is anhydrous aluminum chloride, the amount of anhydrous aluminum chloride is 0.0025 mol, the amount of ammonium hexafluorochromate is 2.5×10 -5 -2.25×10 -4 mol; in step 4, the K 2 LiMF 6 :xCr 3+ K 2 LiF 6 :xCr 3+ .

[0016] Preferably, in step 1, the weighed raw materials and the chemical quantities are as follows: the amount of potassium bifluoride is 0.0075 mol, the lithium salt is lithium nitrate, the amount of lithium nitrate is 0.0025 mol, the M salt is gallium nitrate hydrate, the amount of gallium nitrate hydrate is 0.0025 mol, and the amount of ammonium hexafluorochromate is 2.5×10 -5 -2.25×10 -4 mol; in step 4, the K 2 LiMF 6 :xCr 3+ K 2 LiGaF 6 :xCr 3+ .

[0017] Preferably, in step 1, the weighed raw materials and the chemical quantities are as follows: the amount of potassium bifluoride is 0.0375 mol, the lithium salt is lithium chloride, the amount of lithium chloride is 0.0025 mol, the M salt is indium trichloride tetrahydrate, the amount of indium trichloride tetrahydrate is 0.0025 mol, and the amount of ammonium hexafluorochromate is 2.5×10 -5 -2.25×10 -4 mol; in step 4, the K 2 LiMF 6 :xCr 3+ K 2 InF 6 :xCr 3+ .

[0018] Preferably, in step 2, the first and second stirring times are both 10-20 minutes, and the rotation speed is 600 rpm.

[0019] Preferably, in step 3, the sealed heating comprises: placing the solution A into a sealed reactor, wherein the inner lining of the reactor is para-polyphenol.

[0020] In step 3, the temperature of the sealed heating is 180° C. and the heating time is 6 hours.

[0021] Preferably, in step 4, the washing method is to wash with deionized water for 2-5 times; the centrifugation is controlled at 4000-5000 rpm, and the drying method is to dry in a vacuum drying oven at 60° C. for 6-10 hours.

[0022] The present invention also provides a Cr 3+ The application of the hexafluoride doped near-infrared fluorescent material in the near-infrared light excitation of visible light is to irradiate the Cr with visible light under the condition of less than or equal to 150°C. 3+ Doped hexafluoride near-infrared fluorescent material; the visible light wavelength is 400-700nm; the Cr 3+ The near-infrared light excited by the hexafluoride-doped near-infrared fluorescent material has a wavelength of 650 to 1000 nm. Under the environmental condition of 150°C, the Cr 3+ The emission intensity of the near-infrared light of the hexafluoride-doped near-infrared fluorescent material can be maintained at more than 75% at 25°C.

[0023] Beneficial effects of the present invention:

[0024] 1. Material K provided by the present invention 2 LiMF 6 :xCr 3+ It can be excited by visible light (blue light, red light) to achieve broadband near-infrared emission and has ultra-high thermal stability at 150°C. Using it to prepare near-infrared light source devices can achieve night vision and venous imaging functions, which has research significance and application value.

[0025] 2. The present invention adopts a hydrothermal method to prepare K in aqueous solution 2 LiMF 6 :xCr 3+ The reaction conditions are green and mild, which effectively reduces the risk of experimental safety accidents. The preparation process is simple, which is conducive to its large-scale production.

[0026] 3. The present invention provides a Cr 3+ The application of hexafluoride-doped near-infrared fluorescent materials in visible light-excited near-infrared light shows good thermal stability at up to 150°C, making it suitable for use in high-temperature scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is K in Example 1 2 LiF6 :Cr 3+ XRD diffraction pattern of .

[0028] Figure 2 is K in Example 6 2 LiGaF 6 :Cr 3+ XRD diffraction pattern of .

[0029] Figure 3 is K in Example 11 2 InF 6 :Cr 3+ XRD diffraction pattern of .

[0030] Figure 4 is K in Example 1 2 LiF 6 :Cr 3+ Room temperature excitation spectrum (monitoring wavelength is 755nm) and emission spectrum (excitation wavelength is 431nm).

[0031] Figure 5 is K in Example 1-5 2 LiF 6 :Cr 3+ Room temperature emission spectrum.

[0032] Figure 6 is K in Example 6 2 LiGaF 6 :Cr 3+ Room temperature excitation spectrum (monitoring wavelength is 755nm) and emission spectrum (excitation wavelength is 433nm).

[0033] Figure 7 is K in Example 6-10 2 LiGaF 6 :Cr 3+ Room temperature emission spectrum.

[0034] Figure 8 is K in Example 11 2 InF 6 :Cr 3+ Room temperature excitation spectrum (monitoring wavelength is 780nm) and emission spectrum (excitation wavelength is 436nm).

[0035] Fig. 9 K in Examples 11-15 2 InF 6 :Cr 3+ Room temperature emission spectrum.

[0036] Fig.10 is K in Example 3 2LiF 6 :Cr 3+ Temperature spectrum in the range of 25-250°C (monitoring wavelength is 755nm).

[0037] Fig.11 is K in Example 8 2 LiGaF 6 :Cr 3+ Temperature spectrum in the range of 25-250°C (monitoring wavelength is 755nm).

[0038] Fig.12 is K in Example 14 2 InF 6 :Cr 3+ Temperature spectrum in the range of 25-250℃ (monitoring wavelength is 780nm). DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. Those skilled in the art should understand that the embodiments are only used to explain the present invention and are not used to limit the scope of the present invention.

[0040] Example 1

[0041] Weigh 1.7573 g potassium bifluoride, 0.1060 g lithium chloride and 0.3334 g anhydrous aluminum chloride and dissolve them in 15 ml deionized water, and stir at room temperature for 20 minutes. Then add 0.0055 g ammonium hexafluorochromate to the solution and stir at room temperature for 20 minutes. Then put the resulting solution into an oven and react at 180°C for 6 hours. The resulting precipitate is washed twice with deionized water and finally dried in a vacuum drying oven at 60°C for 6 hours. The resulting light green powder is the final product K 2 LiF 6 :Cr 3+ .

[0042] The XRD diffraction pattern of this phosphor is as follows Figure 1 As shown, the diffraction peaks of the sample are consistent with the matrix K 2 LiF 6 The standard card JCPDS86-2057 is completely consistent, and no diffraction peaks of other impurity phases are observed, which indicates that the synthesized sample has high purity and a cubic crystal structure.

[0043] Figure 4 K is shown 2 LiF 6 :Cr 3+The room temperature excitation spectrum (monitoring wavelength is 755nm) and emission spectrum (excitation wavelength is 431nm). The embodiments of the present invention have strong broadband excitation in the blue light region (400-500nm) and the red light region (600-700nm), which can be well matched with the blue light chip. Under 431nm excitation, it has broadband near-infrared emission with a wavelength from 650-950nm, and the emission peak is at 755nm, and the half-peak width is 115nm.

[0044] Example 2

[0045] Weigh 1.7573 g potassium bifluoride, 0.1060 g lithium chloride and 0.3334 g anhydrous aluminum chloride and dissolve them in 15 ml deionized water, and stir at room temperature for 20 minutes. Add 0.0165 g ammonium hexafluorochromate to the solution and stir at room temperature for 20 minutes. Then put the resulting solution into an oven and react at 180°C for 6 hours. Wash the resulting precipitate twice with deionized water, and finally dry it in a vacuum drying oven at 60°C for 6 hours. The resulting light green powder is the final product K. 2 LiF 6 :Cr 3+ .

[0046] Example 3

[0047] Weigh 1.7573 g potassium bifluoride, 0.1060 g lithium chloride and 0.3334 g anhydrous aluminum chloride and dissolve them in 15 ml deionized water, and stir at room temperature for 20 minutes. Add 0.0275 g ammonium hexafluorochromate to the solution and stir at room temperature for 20 minutes. Then put the resulting solution into an oven and react at 180°C for 6 hours. Wash the resulting precipitate twice with deionized water, and finally dry it in a vacuum drying oven at 60°C for 6 hours. The resulting light green powder is the final product K. 2 LiF 6 :Cr 3+ .

[0048] Fig.10 The temperature spectrum of the phosphor of this example is shown in the range of 25-250° C. At 150° C., its emission intensity can maintain 102.34% of that at 25° C., indicating that the phosphor has ultra-high thermal stability.

[0049] Example 4

[0050] Weigh 1.7573 g potassium bifluoride, 0.1060 g lithium chloride and 0.3334 g anhydrous aluminum chloride and dissolve them in 15 ml deionized water, and stir at room temperature for 20 minutes. Add 0.0385 g ammonium hexafluorochromate to the solution and stir at room temperature for 20 minutes. Then put the resulting solution into an oven and react at 180°C for 6 hours. Wash the resulting precipitate twice with deionized water, and finally dry it in a vacuum drying oven at 60°C for 6 hours. The resulting light green powder is the final product K. 2 LiF 6 :Cr 3+ .

[0051] Example 5

[0052] Weigh 1.7573 g potassium bifluoride, 0.1060 g lithium chloride and 0.3334 g anhydrous aluminum chloride and dissolve them in 15 ml deionized water, and stir at room temperature for 20 minutes. Add 0.0495 g ammonium hexafluorochromate to the solution and stir at room temperature for 20 minutes. Then put the resulting solution into an oven and react at 180°C for 6 hours. Wash the resulting precipitate twice with deionized water, and finally dry it in a vacuum drying oven at 60°C for 6 hours. The resulting light green powder is the final product K. 2 LiF 6 :Cr 3+ .

[0053] Figure 5 is K in Example 1-5 2 LiF 6 :Cr 3+ The room temperature emission spectrum of (x=0.01-0.09) has a strong broadband near-infrared emission with a wavelength from 650-950nm under 431nm excitation.

[0054] Example 6

[0055] Weigh 0.5857 g potassium bifluoride, 0.1723 g lithium nitrate and 0.6393 g gallium nitrate hydrate and dissolve them in 15 ml deionized water, and stir at room temperature for 20 minutes. Then add 0.0055 g ammonium hexafluorochromate to the solution and stir at room temperature for 20 minutes. Then put the resulting solution into an oven and react at 180°C for 6 hours. The resulting precipitate is washed twice with deionized water and finally dried in a vacuum drying oven at 60°C for 6 hours. The resulting light green powder is the final product K 2 LiGaF 6 :Cr 3+ .

[0056] The XRD diffraction pattern of this phosphor is as follows Figure 2 As shown, the diffraction peaks of the sample are consistent with the matrix K 2 LiGaF 6The standard card JCPDS22-1225 is completely consistent, and no diffraction peaks of other impurity phases are observed, which indicates that the synthesized sample has high purity and a cubic crystal structure.

[0057] Figure 6 K is shown 2 LiGaF 6 :Cr 3+ The room temperature excitation spectrum (monitoring wavelength is 755nm) and emission spectrum (excitation wavelength is 433nm). The embodiments of the present invention have strong broadband excitation in the blue light region (400-500nm) and the red light region (600-700nm), which can be well matched with the blue light chip. Under 433nm excitation, it has broadband near-infrared emission with a wavelength from 650-950nm, and the emission peak is at 755nm, and the half-peak width is 118nm.

[0058] Example 7

[0059] Weigh 0.5857 g potassium bifluoride, 0.1723 g lithium nitrate and 0.6393 g gallium nitrate hydrate and dissolve them in 15 ml deionized water, and stir at room temperature for 20 minutes. Then add 0.0165 g ammonium hexafluorochromate to the solution and stir at room temperature for 20 minutes. Then put the resulting solution into an oven and react at 180°C for 6 hours. The resulting precipitate is washed twice with deionized water and finally dried in a vacuum drying oven at 60°C for 6 hours. The resulting light green powder is the final product K 2 LiGaF 6 :Cr 3+ .

[0060] Example 8

[0061] Weigh 0.5857 g potassium bifluoride, 0.1723 g lithium nitrate and 0.6393 g gallium nitrate hydrate and dissolve them in 15 ml deionized water, and stir at room temperature for 20 minutes. Then add 0.0275 g ammonium hexafluorochromate to the solution and stir at room temperature for 20 minutes. Then put the resulting solution into an oven and react at 180°C for 6 hours. The resulting precipitate is washed twice with deionized water and finally dried in a vacuum drying oven at 60°C for 6 hours. The resulting light green powder is the final product K 2 LiGaF 6 :Cr 3+ .

[0062] Fig.11 The temperature spectrum of the phosphor of this example is shown in the range of 25-250° C. At 150° C., its emission intensity can maintain 91.82% of that at 25° C., indicating that the phosphor has ultra-high thermal stability.

[0063] Example 9

[0064] Weigh 0.5857 g potassium bifluoride, 0.1723 g lithium nitrate and 0.6393 g gallium nitrate hydrate and dissolve them in 15 ml deionized water, and stir at room temperature for 20 minutes. Then add 0.0385 g ammonium hexafluorochromate to the solution and stir at room temperature for 20 minutes. Then put the resulting solution into an oven and react at 180°C for 6 hours. The resulting precipitate is washed twice with deionized water and finally dried in a vacuum drying oven at 60°C for 6 hours. The resulting light green powder is the final product K 2 LiGaF 6 :Cr 3+ .

[0065] Example 10

[0066] Weigh 0.5857 g potassium bifluoride, 0.1723 g lithium nitrate and 0.6393 g gallium nitrate hydrate and dissolve them in 15 ml deionized water, and stir at room temperature for 20 minutes. Then add 0.0495 g ammonium hexafluorochromate to the solution and stir at room temperature for 20 minutes. Then put the resulting solution into an oven and react at 180°C for 6 hours. The resulting precipitate is washed twice with deionized water and finally dried in a vacuum drying oven at 60°C for 6 hours. The resulting light green powder is the final product K 2 LiGaF 6 :Cr 3+ .

[0067] Figure 7 is K in Example 6-10 2 LiGaF 6 :Cr 3+ The room temperature emission spectrum of (x=0.01-0.09) has a strong broadband near-infrared emission with a wavelength from 650-950nm under 433nm excitation.

[0068] Embodiment 11

[0069] Weigh 2.9287 g potassium bifluoride, 0.1060 g lithium chloride and 0.7331 g indium trichloride tetrahydrate and dissolve them in 15 ml deionized water, and stir at room temperature for 20 minutes. Add 0.0055 g ammonium hexafluorochromate to the solution and stir at room temperature for 20 minutes. Then put the resulting solution into an oven and react at 180°C for 6 hours. Wash the resulting precipitate twice with deionized water, and finally dry it in a vacuum drying oven at 60°C for 6 hours. The resulting light green powder is the final product K 2 InF 6 :Cr 3+ .

[0070] The XRD diffraction pattern of this phosphor is as follows Figure 3 As shown, the diffraction peaks of the sample are consistent with the matrix K 2 InF 6The results are completely consistent, and no diffraction peaks of other impurity phases were observed, which indicates that the synthesized sample has high purity and a cubic crystal structure.

[0071] Figure 8 K is shown 2 InF 6 :Cr 3+ The room temperature excitation spectrum (monitoring wavelength is 780nm) and emission spectrum (excitation wavelength is 436nm). The embodiments of the present invention have strong broadband excitation in the blue light region (400-500nm) and the red light region (600-700nm), which can be well matched with the blue light chip. Under 436nm excitation, it has broadband near-infrared emission with a wavelength from 650-950nm, and the emission peak is at 780nm, and the half-peak width is 125nm.

[0072] Example 12

[0073] Weigh 2.9287 g potassium bifluoride, 0.1060 g lithium chloride and 0.7331 g indium trichloride tetrahydrate and dissolve them in 15 ml deionized water, and stir at room temperature for 20 minutes. Add 0.0165 g ammonium hexafluorochromate to the solution and stir at room temperature for 20 minutes. Then put the resulting solution into an oven and react at 180°C for 6 hours. Wash the resulting precipitate twice with deionized water, and finally dry it in a vacuum drying oven at 60°C for 6 hours. The resulting light green powder is the final product K. 2 InF 6 :Cr 3+ .

[0074] Example 13

[0075] Weigh 2.9287 g potassium bifluoride, 0.1060 g lithium chloride and 0.7331 g indium trichloride tetrahydrate and dissolve them in 15 ml deionized water, and stir at room temperature for 20 minutes. Add 0.0275 g ammonium hexafluorochromate to the solution and stir at room temperature for 20 minutes. Then put the resulting solution into an oven and react at 180°C for 6 hours. Wash the resulting precipitate twice with deionized water, and finally dry it in a vacuum drying oven at 60°C for 6 hours. The resulting light green powder is the final product K. 2 InF 6 :Cr 3+ .

[0076] Embodiment 14

[0077] Weigh 2.9287 g potassium bifluoride, 0.1060 g lithium chloride and 0.7331 g indium trichloride tetrahydrate and dissolve them in 15 ml deionized water, and stir at room temperature for 20 minutes. Add 0.0385 g ammonium hexafluorochromate to the solution and stir at room temperature for 20 minutes. Then put the resulting solution into an oven and react at 180°C for 6 hours. Wash the resulting precipitate twice with deionized water, and finally dry it in a vacuum drying oven at 60°C for 6 hours. The resulting light green powder is the final product K. 2 InF 6 :Cr 3+ .

[0078] Fig.12 The temperature spectrum of the phosphor of this example is shown in the range of 25-250° C. At 150° C., its emission intensity can maintain 77.43% of that at 25° C., indicating that the phosphor has ultra-high thermal stability.

[0079] Embodiment 15

[0080] Weigh 2.9287 g potassium bifluoride, 0.1060 g lithium chloride and 0.7331 g indium trichloride tetrahydrate and dissolve them in 15 ml deionized water, and stir at room temperature for 20 minutes. Add 0.0495 g ammonium hexafluorochromate to the solution and stir at room temperature for 20 minutes. Then put the resulting solution into an oven and react at 180°C for 6 hours. Wash the resulting precipitate twice with deionized water, and finally dry it in a vacuum drying oven at 60°C for 6 hours. The resulting light green powder is the final product K. 2 InF 6 :Cr 3+ .

[0081] Fig. 9 K in Examples 11-15 2 InF 6 :Cr 3+ The room temperature emission spectrum of (x=0.01-0.09) has a strong broadband near-infrared emission with a wavelength from 650-950nm under 436nm excitation.

[0082] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A Cr 3+ Preparation method of hexafluoride-doped near-infrared fluorescent material, It is characterized in that: It includes the following steps: Step 1: Weigh raw materials according to the stoichiometric ratio of the chemical composition formula: potassium bifluoride, lithium salt, M salt, ammonium hexafluorochromate; the lithium salt is any one or a combination of two of lithium chloride and lithium nitrate; the M salt is any one or a combination of two of the chloride and nitrate of M; Step 2: Dissolve potassium bifluoride, lithium salt, and M salt in water to form an aqueous solution, stir for the first time at room temperature, then add ammonium hexafluorochromate to the aqueous solution and stir for the second time at room temperature to obtain solution A; Step 3: Heat the solution A obtained in Step 2 in a closed manner to obtain a precipitate; Step 4: Wash, centrifuge and dry the precipitate to obtain K 2 LiMF 6 :xCr 3+ ; In step 1, the raw materials and the chemical quantities weighed are as follows: the amount of potassium bifluoride is 0.0225 mol, the lithium salt is lithium chloride, the amount of lithium chloride is 0.0025 mol, the M salt is anhydrous aluminum chloride, the amount of anhydrous aluminum chloride is 0.0025 mol, the amount of ammonium hexafluorochromate is 1.25×10 -5 mol; in step 4, the K 2 LiMF 6 :xCr 3+ K 2 LiF 6 :xCr 3+ , where x = 0.05, the Cr 3+ The hexafluoride-doped near-infrared fluorescent material has a cubic double perovskite crystal structure; at 150°C, its emission intensity can maintain 102.34% of that at 25°C; In Step 2, the time for both the first and second stirrings is 10 - 20 minutes, and the stirring speed is 600 revolutions per minute; In Step 3, the closed heating includes: putting the solution A into a closed reaction kettle, the inner lining of the reaction kettle is p - polyphenol; the temperature of the closed heating is 180 °C, and the heating time is 6 hours; In Step 4, the washing includes: washing 2 - 5 times with deionized water; the centrifugation speed is 4000 - 5000 revolutions per minute, and the drying method is drying in a vacuum drying oven at 60 °C for 6 - 10 hours.

2. The Cr as claimed in claim 1 3+ Preparation method of hexafluoride-doped near-infrared fluorescent material 3+ Application of hexafluoride-doped near-infrared fluorescent materials in visible light excitation of near-infrared light.

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