Self-activated near-infrared fluorescent powder, preparation method and application thereof

Abstract

The application discloses self-activated near-infrared fluorescent powder and a preparation method and application thereof, and belongs to the near-infrared luminescent material field.The self-activated near-infrared fluorescent powder has a chemical general formula of BaAl2B2O7:xLi + Wherein, x represents the molar number of the doped monovalent lithium ion, 0 < x <= 0.10.The application adopts a high-temperature solid-phase method, has simple preparation process, easily obtained synthesis raw materials, is easy to operate, has low preparation cost, is environment-friendly and low in cost.The self-activated near-infrared fluorescent powder prepared by the application generates lattice defects in the borate matrix material by introducing Li + , regulates the concentration of the interstitial oxygen defects (increases the defect concentration), enhances the emission intensity through defect engineering, exhibits adjustable emission in the range of 710-780 nm, greatly improves the thermal stability, and can better meet the actual requirements of NIR LED application.

Description

Technical Field

[0001] The present invention relates to the field of near-infrared luminescent materials, and in particular to a self-activated near-infrared phosphor and a preparation method and application thereof. Background Art

[0002] Near-infrared luminescent materials have important research significance among light-conversion luminescent materials. They are fast, non-invasive and non-destructive, and are widely used in food quality assessment, drug component analysis, medical imaging, night vision and other fields. Traditional near-infrared light sources, such as halogen lamps and tungsten-halogen lamps, have disadvantages such as large size, low efficiency, high cost and narrow emission peak, which limit their application. At present, the emergence of near-infrared light-emitting diodes (NIRpc-LEDs) has overcome the wavelength limitations of traditional infrared light sources. They are efficient, durable and environmentally friendly, and are expected to become a substitute for traditional light sources. NIR pc-LEDs are integrated with LED chips by near-infrared phosphors. The near-infrared phosphors determine the performance of NIRpc-LEDs. Therefore, the development of high-performance, broadband near-infrared phosphors is crucial for this technology.

[0003] Currently, the reported near-infrared luminescent phosphors are mainly doped with rare earth ions and transition metal ions as activators. 3+ 、Nd 3+ 、Yb 3+ The phosphors doped with Cr, etc. are not only expensive, but also have problems such as weak absorption and narrow emission band. 3+ and Mn 4+ Although Cr phosphors have lower cost and broader near-infrared emission spectra, their luminescence is highly dependent on the crystal field strength within the host lattice, which makes it challenging to control their emission wavelength. 3+ and Mn 4+ It is not suitable for certain fields with high safety requirements. Nowadays, the demand for non-toxic and low-cost near-infrared luminescent materials is increasing.

[0004] Unlike doped phosphors, self-activated phosphors derive their luminescence from structural defect-type luminescence centers directly formed in the matrix. These phosphors, characterized by low cost, high excitation threshold, minimal reabsorption overlap, and low sintering temperature, are attracting increasing attention. Currently, some progress has been made in the development of near-infrared self-activated phosphors, such as CaLaMgTaO6, SrLaMgTaO6, and Na2ZrTeO6. However, these phosphors have drawbacks, such as relatively low emission efficiency, a single emission wavelength, and poor thermal stability, making them difficult to meet the requirements for practical application in near-infrared PC-LED devices.

[0005] Therefore, how to obtain a self-activated near-infrared phosphor with high luminous efficiency, adjustable spectrum and good thermal stability is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0006] In order to solve the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a self-activated near-infrared phosphor and its preparation method and application, which can effectively solve the problems of low luminous efficiency, single emission wavelength and poor thermal stability of the phosphor in the prior art.

[0007] In order to achieve the above purpose or other purposes, the present invention is implemented through the following technical solutions.

[0008] A self-activated near-infrared phosphor with the general chemical formula BaAl2B2O7:xLi + , where x represents the molar number of monovalent lithium ion doping, 0<x≤0.10.

[0009] Preferably, x is selected from any one of 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 and 0.10.

[0010] A method for preparing a self-activated near-infrared phosphor comprises the following steps:

[0011] (1) Chemical formula BaAl2B2O7:xLi + , 0<x≤0.10, according to the chemical formula Ba 2+ 、Al 3+ , BO3 3- 、Li + The stoichiometric ratio of Ba 2+ Compounds containing Al 3+ Compounds containing BO3 3- Compounds containing Li + The compound is added with anhydrous ethanol, mixed and ground to obtain a mixture;

[0012] (2) The mixture obtained in step (1) is calcined and ground in an air atmosphere to obtain a self-activated near-infrared phosphor.

[0013] Preferably, the Ba-containing 2+ The compound is selected from one or more of BaCO3, Ba(OH)2, and Ba(NO3)2. More preferably, the Ba-containing 2+ The compound is selected from BaCO3.

[0014] Preferably, the Al-containing 3+ The compound is selected from one or more of Al2O3, Al(NO3)3, and Al(OH)3. More preferably, the Al-containing3+ The compound is selected from Al2O3 or Al(OH)3.

[0015] Preferably, the Li-containing + The compound is selected from one or more of Li2O, Li2CO3, and Li(OH). More preferably, the Li-containing + The compound is selected from Li2O and / or Li2CO3. More preferably, the Li-containing + The compound is selected from Li2CO3.

[0016] Preferably, the BO3 3- The compound is selected from H3BO3 and / or K2B4O7·10H2O. More preferably, the compound containing BO3 3- The compound is selected from H3BO3.

[0017] Preferably, the amount of anhydrous ethanol added in step (1) is 20-70% of the total mass of the compound raw material. More preferably, the amount of anhydrous ethanol added is 30-60% of the total mass of the compound raw material. More preferably, the amount of anhydrous ethanol added is 40-50% of the total mass of the compound raw material.

[0018] Preferably, the grinding time in step (1) is 20 to 40 minutes. More preferably, the grinding time in step (1) is 25 to 35 minutes. More preferably, the grinding time in step (1) is 28 to 33 minutes. In the present invention, in order to reduce the particle size and improve the mixing uniformity in step (1), grinding is performed after mixing, which not only increases the contact area of ​​the reactants and shortens the diffusion distance, but also improves the mixing uniformity, promotes crystallization and reduces agglomeration. Preferably, the particle size of the mixture obtained by grinding is less than 50 μm.

[0019] Preferably, the calcination temperature in step (2) is 600-900°C, and the calcination time is 6-12 hours. More preferably, the calcination temperature in step (2) is 650-850°C, and the calcination time is 7-11 hours. More preferably, the calcination temperature in step (2) is 700-800°C, and the calcination time is 8-10 hours.

[0020] The present invention also provides an application of the self-activated near-infrared phosphor in the field of near-infrared luminescent materials.

[0021] The present invention utilizes a high-temperature solid-phase method, resulting in a simple preparation process and readily available synthetic raw materials, easy operation, and low production cost. Furthermore, the use of toxic organic solvents and the resulting wastewater pollution are effectively avoided, making it both environmentally friendly and cost-effective. The present invention utilizes borate as a host material, which exhibits a simple preparation process, low synthesis temperature, good light transmittance, a high optical damage threshold, excellent thermal stability, a rich and diverse structure, and a wide range of selectable properties, making it an excellent luminescent host material.

[0022] The self-activated near-infrared phosphor prepared by the present invention is prepared by introducing Li + , lattice defects are generated in the borate matrix material, the concentration of interstitial oxygen defects is regulated (the defect concentration increases), the emission intensity is enhanced through defect engineering, and adjustable emission is exhibited in the range of 710-780nm. The thermal stability is also greatly improved. The prepared self-activated near-infrared phosphor can better meet the actual requirements of NIR LED applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a SEM image of the near-infrared phosphor prepared in Comparative Example 1;

[0024] Figure 2 This is a SEM image of the self-activated near-infrared phosphor prepared in Example 7;

[0025] Figure 3 X-ray diffraction spectra of the self-activated near-infrared phosphors prepared in Comparative Example 1 and Examples 1 to 7;

[0026] Figure 4 Excitation spectra of the self-activated near-infrared phosphors prepared in Comparative Example 1 and Examples 1 to 7 at emission wavelengths of 780 nm and 720 nm, respectively;

[0027] Figure 5 Emission spectra of the self-activated near-infrared phosphors prepared in Comparative Example 1 and Examples 1 to 7 at excitation wavelengths of 330 nm and 270 nm, respectively;

[0028] Figure 6 Emission spectra of the near-infrared phosphor prepared in Comparative Example 1 at different temperatures (excitation wavelength is 330 nm);

[0029] Figure 7 Emission spectra of the self-activated near-infrared phosphor prepared in Example 1 at different temperatures (excitation wavelength is 270 nm);

[0030] Figure 8 Emission spectra of the self-activated near-infrared phosphor prepared in Example 7 at different temperatures (excitation wavelength is 270 nm);

[0031] Figure 9 Electron paramagnetic resonance spectra of the self-activated near-infrared phosphors prepared in Comparative Example 1, Example 1, and Example 7 obtained under 254 nm irradiation;

[0032] Figure 10 Thermoluminescence spectra of the self-activated near-infrared phosphors prepared in Comparative Example 1 and Example 7;

[0033] Figure 11 This is the application of the self-activated near-infrared phosphor prepared in Example 7. DETAILED DESCRIPTION

[0034] The following describes the embodiments of the present invention through specific embodiments. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0035] It should be noted that, unless there is a conflict, the features in the following examples and embodiments may be combined with each other. It should also be understood that the terms used in the examples of the present invention are intended to describe specific embodiments and are not intended to limit the scope of protection of the present invention. The test methods in the following examples, where specific conditions are not specified, are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0036] When numerical ranges are given in the examples, it should be understood that unless otherwise specified herein, both endpoints of each numerical range and any value between the two endpoints may be used. Unless otherwise defined, all technical and scientific terms used herein are consistent with the prior art as understood by those skilled in the art and the description of the present invention. Any prior art methods, devices, and materials similar or equivalent to those described in the examples of the present invention may also be used to implement the present invention.

[0037] Example 1:

[0038] BaAl2B2O7:0.04Li +

[0039] Ba(OH)2, Al2O3, Li2CO3, and H3BO3 are weighed according to the molar weights expressed in the chemical formula and ground. Anhydrous ethanol (40% by weight of the total weight) is added and the mixture is ground for 30 minutes to thoroughly combine. The mixture is then calcined at 750°C in air for 10 hours. The mixture is then cooled to room temperature, and the resulting block sample is ground into a powder to obtain the desired self-activated near-infrared phosphor.

[0040] Example 2

[0041] BaAl2B2O7:0.05Li +

[0042] Ba(NO3)2, Al(NO3)3, Li2CO3, and H3BO3 are weighed according to the molar amounts expressed in the chemical formula and placed in an agate mortar. Anhydrous ethanol (30% of the total weight of the raw materials) is added and ground for 28 minutes to thoroughly mix the materials. The mixed reactants are then calcined at 700°C in air for 8 hours. After cooling to room temperature in a high-temperature tube furnace, the resulting block sample is ground into a powder in an agate mortar to obtain the desired self-activated near-infrared phosphor.

[0043] Example 3

[0044] BaAl2B2O7:0.06Li +

[0045] BaCO₃, Al(OH)₃, Li₂O, and H₃BO₃ are weighed according to the molar amounts expressed in the chemical formula and placed in an agate mortar. Anhydrous ethanol (45% of the total weight of the raw materials) is added and ground for 25 minutes to thoroughly mix the materials. The mixed reactants are then calcined at 800°C in air for 10 hours. After cooling to room temperature in a high-temperature tube furnace, the resulting block sample is ground into a powder in an agate mortar to obtain the desired self-activated near-infrared phosphor.

[0046] Example 4

[0047] BaAl2B2O7:0.07Li +

[0048] BaCO₃, Al(OH)₃, Li₂CO₃, and H₃BO₃ are weighed according to the molar amounts expressed in the chemical formula and placed in an agate mortar. Anhydrous ethanol, representing 60% of the total weight of the raw materials, is added and ground for 33 minutes to thoroughly mix the materials. The resulting mixture is then calcined at 650°C in air for 9 hours. After cooling to room temperature in a high-temperature tube furnace, the resulting block sample is ground into a powder in an agate mortar to obtain the desired self-activated near-infrared phosphor.

[0049] Example 5

[0050] BaAl2B2O7:0.08Li +

[0051] BaCO₃, Al(OH)₃, Li₂CO₃, and H₃BO₃ are weighed according to the molar amounts expressed in the chemical formula and placed in an agate mortar. Anhydrous ethanol (45% of the total weight of the raw materials) is added and ground for 35 minutes to thoroughly mix the materials. The homogenized reactants are calcined at 800°C in air for 11 hours. After cooling to room temperature in a high-temperature tube furnace, the resulting block sample is ground into a powder in an agate mortar to obtain the desired self-activated near-infrared phosphor.

[0052] Example 6

[0053] BaAl2B2O7:0.09Li +

[0054] BaCO₃, Al(OH)₃, Li₂CO₃, and H₃BO₃ are weighed according to the molar amounts expressed in the chemical formula and placed in an agate mortar. Anhydrous ethanol (20% of the total weight of the raw materials) is added and ground for 20 minutes to thoroughly mix the materials. The mixed reactants are then calcined at 600°C in air for 7 hours. After cooling to room temperature in a high-temperature tube furnace, the resulting block sample is ground into a powder in an agate mortar to obtain the desired self-activated near-infrared phosphor.

[0055] Example 7

[0056] BaAl2B2O7:0.10Li +

[0057] BaCO₃, Al(OH)₃, Li₂CO₃, and H₃BO₃ are weighed according to the molar amounts expressed in the chemical formula and placed in an agate mortar. Anhydrous ethanol, representing 50% of the total weight of the raw materials, is added and ground for 40 minutes to thoroughly mix the materials. The resulting mixture is calcined at 850°C in air for 11 hours. After cooling to room temperature in a high-temperature tube furnace, the resulting block sample is ground into a powder in an agate mortar to obtain the desired self-activated near-infrared phosphor.

[0058] Example 8

[0059] BaAl2B2O7:0.10Li +

[0060] BaCO₃, Al(OH)₃, Li(OH), and K₂B₄O₇·10H₂O were weighed according to the molar amounts expressed in the chemical formula and placed in an agate mortar. Anhydrous ethanol, representing 70% of the total weight of the raw materials, was added and ground for 40 minutes to thoroughly mix the materials. The homogenized reactants were calcined at 900°C in air for 11 hours. After cooling to room temperature in a high-temperature tube furnace, the resulting block sample was ground into a powder in an agate mortar to obtain the desired self-activated near-infrared phosphor.

[0061] Comparative Example 1

[0062] BaAl2B2O7

[0063] Ba2CO3, Al(OH)3, and H3BO3 are weighed according to the molar amounts expressed in the chemical formula. Anhydrous ethanol (50% of the total weight of the raw materials) is added and ground for 20 minutes to thoroughly mix the materials. The mixture is then calcined at 750°C in air for 7 hours. After cooling to room temperature in a high-temperature tube furnace, the resulting block sample is ground into a powder in an agate mortar to obtain the desired phosphor.

[0064] Performance Testing

[0065] 1. Take the phosphor of comparative example 1 and the self-activated near-infrared phosphor obtained in example 7 and conduct SEM test. The obtained spectra are as follows: Figure 1 、 2 As shown in the figure, the phosphors obtained in both Comparative Example 1 and Example 7 consist of irregularly shaped particles clustered together with good interparticle spacing, indicating good crystal growth. However, the self-activated near-infrared phosphor obtained in Example 7 has a finer particle size, ranging from 5 to 10 microns, which is more conducive to improving luminous efficiency, dispersion, and uniformity.

[0066] 2. The phosphor of Comparative Example 1 and the self-activated near-infrared phosphors improved by defect engineering prepared in Examples 1 to 7 were subjected to X-ray diffraction tests. The obtained patterns are as follows: Figure 3 As shown in the figure, it can be seen that the diffraction peaks of the obtained phosphor are in good agreement with those of the standard card, and no impurity peaks appear. + The phosphor is a pure phase, wherein x represents the molar number of monovalent lithium ions doped, and 0≤x≤0.10.

[0067] 3. The excitation spectra of the phosphor of Comparative Example 1 and the self-activated near-infrared phosphors improved by defect engineering prepared in Examples 1 to 7 were measured at emission wavelengths of 780 nm and 720 nm, respectively. Figure 4 As shown; the emission spectrum was measured at excitation wavelengths of 270nm and 330nm, as shown Figure 5 As shown in the figure, it can be seen that the self-activated near-infrared phosphors improved by defect engineering in Examples 1 to 7 are + The fluorescence intensity increases with the increase of the doping content, and the strongest emission is obtained when x = 0.10. In particular, when the fluorescence intensity of the self-activated near-infrared phosphor increases, the peak position shows a continuous blue shift, accompanied by a widening of the peak width. Compared with the BaAl2B2O7 matrix, the representative BaAl2B2O7:0.10Li +The PL intensity of the phosphor increased approximately 8-fold, with the PL peak position showing a blue shift of approximately 69 nm and a widening of the full width at half maximum from 85.4 nm to 102.8 nm. Excitation spectra measured at the strongest emission wavelength also showed a continuous blue shift in the excitation peaks of the defect-engineered self-activated near-infrared phosphors prepared in Examples 1-7, reaching a maximum intensity at x = 0.10.

[0068] 4. The phosphor of comparative example 1 and the self-activated near-infrared phosphors improved by defect engineering prepared in Examples 1 and 7 were subjected to variable temperature emission spectrum tests (test temperatures were 25°C, 50°C, 75°C, 100°C, 125°C, and 150°C, respectively). The test results are as follows: Figure 6 、 Figure 7 and Figure 8 As shown. Figure 6 、 Figure 7 and Figure 8 It can be seen that as the temperature increases, the intensity of the emission band of the phosphor BaAl2B2O7 prepared in Comparative Example 1 decreases sharply, and the emission intensity at 150°C is only 37% of the emission intensity at room temperature. In contrast, the self-activated near-infrared phosphor BaAl2B2O7:0.04Li prepared in Examples 1 and 7 with improved defect engineering + and BaAl2B2O7:0.10Li + Thermal stability is greatly enhanced. At 150℃, BaAl2B2O7:0.04Li + and BaAl2B2O7:0.10Li + The emission intensity of the powders is 81% and 86% of the room temperature emission intensity, respectively, and the thermal stability is improved by 44% and 52% compared with BaAl2B2O7 phosphors.

[0069] 5. The phosphor of comparative example 1 and the self-activated near-infrared phosphors improved by defect engineering prepared in examples 1 and 7 were tested by electron paramagnetic resonance spectroscopy. The results are as follows: Figure 9 As shown. Figure 9 It can be seen that in all three samples, a characteristic peak of interstitial oxygen defect with a signal value of 2.005 is observed at 3510 Gauss. + As the concentration increases, the concentration of interstitial oxygen defects increases.

[0070] 6. The phosphor of Comparative Example 1 and the self-activated near-infrared phosphor with improved defect engineering prepared in Example 7 were subjected to thermoluminescence spectrum test. Figure 10 As shown. Figure 10 It can be seen that compared with Comparative Example 1, the thermoluminescence spectrum intensity of the self-activated near-infrared phosphor improved by defect engineering in Example 7 is significantly enhanced, and the main peak position moves toward the high temperature direction. This change indicates that Li +Doping increases the trap depth and the density of trapped charge carriers in deep traps. The shape of the thermoluminescence spectrum curve is composed of traps of different depths. + The peak shape changes when L is doped, indicating that the trap distribution changes. By fitting the TL curves of the comparative example 1 and the example 7 samples with Gaussian peaks, two broad bands (trap 1 and trap 2) can be clearly observed in the comparative example 1, with peaks at 355K and 423K respectively; three broad bands (trap 1, trap 2, trap 3) can be clearly observed in the example 7, with peaks at around 381K, 449K and 536K respectively. i+ Finally, a new defect energy level trap 3 was introduced.

[0071] 7. Take the self-activated near-infrared phosphor obtained in Example 7 and prepare LED by conventional technology. Prepare ultraviolet LED chip (wavelength 280nm), BaAl2B2O7:0.10Li + Phosphor (Example 7) and two-component PDMS silica gel (main agent and curing agent). Weigh BaAl2B2O7:0.10Li + 0.2g of phosphor, 1.62g of main agent and 0.18g of curing agent were stirred evenly for 15min, and then a pipette with a range of 100-1000μL was used to draw two dots on the LED chip. The LED chip was then dried in a 75℃ oven for 2-3h to obtain the BaAl2B2O7:0.10Li obtained in Example 7. + A near-infrared LED made of self-activated near-infrared phosphor was used to observe an orange, a human body, and a picture covered by a 720nm filter, respectively, using a near-infrared camera and the prepared near-infrared LED. Figure 11 As shown, from Figure 11 As can be seen in the figure, the detailed features of the orange (such as shape, spots, etc.) can be clearly observed using the near-infrared camera and the near-infrared LED prepared by the phosphor of Example 7, showing its night vision ability. Under the near-infrared LED illumination, the blood vessels in the hand can be clearly observed, which shows that the device has great potential in biological imaging. Finally, the school badge image covered with a 720nm filter has no visible mark under the near-infrared camera; however, under BaAl2B2O7:0.10Li + Under the illumination of a near-infrared LED made from self-activated near-infrared phosphor, the school badge is clearly visible, indicating that it can be used for the safe detection of invisible markers.

[0072] As can be seen from the above examples, the present invention provides a self-activated near-infrared phosphor improved by defect engineering and a preparation method thereof. Compared with the matrix, the peak intensity of the phosphor improved by defect engineering is enhanced, the peak position is blue-shifted, the half-peak width is widened, and the thermal stability is enhanced. The self-activated near-infrared phosphor improved by defect engineering of the present invention can be effectively excited by short-wave ultraviolet light and exhibits strong emission in the range of 650 to 800 nm. The prepared phosphor has broad application prospects as a near-infrared emission component in various fields (such as night vision, biological imaging, and concealed security mark detection).

[0073] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A self-activated near-infrared phosphor, characterized in that: Its general chemical formula is BaAl2B2O7:xLi + , where x represents the molar number of monovalent lithium ion doping, 0<x≤0.

10.

2. The self-activated near-infrared phosphor according to claim 1, wherein: x is selected from any one of 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, and 0.

10.

3. A method for preparing the self-activated near-infrared phosphor according to claim 1 or 2, characterized in that: The following steps are involved: (1) Chemical formula BaAl2B2O7:xLi + , according to the chemical formula Ba 2+ 、Al 3+ , BO3 3- 、Li + The stoichiometric ratio of Ba 2+ Compounds containing Al 3+ Compounds containing BO3 3- Compounds containing Li + The compound is added with anhydrous ethanol, mixed and ground to obtain a mixture; (2) The mixture obtained in step (1) is calcined and ground in an air atmosphere to obtain a self-activated near-infrared phosphor.

4. The method according to claim 3, wherein The Ba-containing 2+ The compound is selected from one or more of BaCO3, Ba(OH)2, and Ba(NO3)2.

5. The method according to claim 3, wherein The Al-containing 3+ The compound is selected from one or more of Al2O3, Al(NO3)3, and Al(OH)3.

6. The method according to claim 3, wherein The Li-containing + The compound is selected from one or more of Li2O, Li2CO3, and Li(OH).

7. The method according to claim 3, wherein The BO3 3- The compound is selected from H3BO3 and / or K2B4O7·10H2O.

8. The method according to claim 3, wherein The amount of anhydrous ethanol added in step (1) is 20-70% of the total mass of the compound raw material.

9. The method according to claim 3, wherein In step (2), the calcination temperature is 600-900° C., and the calcination time is 6-12 h.

10. Use of the self-activated near-infrared phosphor according to claim 1 or 2 in the field of near-infrared luminescent materials.

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