A self-activated fluorescent material and a preparation method thereof

Abstract

The present invention relates to a self-activated fluorescent material and a preparation method thereof, belonging to the technical field of rare earth luminescent materials. The self-activated fluorescent material of the present invention has a general chemical formula of A2Zn x GeO4:0.01M; where A is Li, Na, K, Rb or Cs, and M is Eu 3+ 、Sm 3+ , Tb 3+ or Pr 3+ , 0.9≤x≤1.2, and under ultraviolet light excitation, it emits blue-violet light in the wavelength range of 300-420nm; when ultraviolet light excitation is stopped, it emits afterglow in the wavelength range of 300-420nm; under the action of mechanical force, it emits ultraviolet light in the wavelength range of 300-420nm. The fluorescent material of the present invention has good chemical stability, high excitation efficiency, and high thermal stability.

Description

Technical Field

[0001] The invention relates to a self-activated fluorescent material and a preparation method thereof, belonging to the technical field of rare earth luminescent materials. Background Art

[0002] Ultraviolet (UVA) light, emitting in the 320nm to 400nm wavelength range, has significant applications in microbial inactivation, photocatalysis, drug delivery, and photodynamic therapy. In particular, UVA emission with afterglow behavior, with its unique light storage capability, enables sustained light output, opening up new possibilities for multidimensional information storage, anti-counterfeiting, and long-lasting phototherapy. Long-lasting luminescent materials typically store excited carriers in traps constructed within the material. When the excitation light source is removed, these trapped carriers are released from the traps due to thermal agitation, resulting in sustained afterglow emission. Furthermore, mechanoluminescence (ML), induced by mechanical forces (including but not limited to compression, tension, shear, and friction) on fluorescent materials, offers new possibilities for UVA applications. However, for both photoluminescence and afterglow luminescence, only a small number of rare-earth-doped aluminates and aluminosilicates have been reported to exhibit UV luminescence, and mechanoluminescent (ML) materials often reside in the visible light region. Therefore, suitable fluorescent materials in the ultraviolet light region (320nm-400nm) have yet to be developed. Summary of the Invention

[0003] Aiming at the lack of fluorescent materials in the ultraviolet (320nm-400nm) region, the present invention proposes a self-activated fluorescent material and a preparation method thereof. The self-activated fluorescent material of the present invention has the general chemical formula of A2Zn x GeO4: 0.01M; under ultraviolet light excitation, it emits blue-violet light in the 300-420nm wavelength range; when UV excitation is stopped, it emits an afterglow in the 300-420nm wavelength range; under mechanical force, it emits ultraviolet light in the 300-420nm wavelength range. Adjusting the Zn ion concentration can control the self-activation process, and the introduction of rare earth ions can enhance the intensity and duration of the UVA afterglow. Under mechanical force stimulation, this material can exhibit mechanoluminescence in the ultraviolet region. The fluorescent material of this invention has good chemical stability, high excitation efficiency, and high thermal stability.

[0004] A self-activated fluorescent material with the general chemical formula A2Zn x GeO4:0.01M; where A is Li, Na, K, Rb or Cs, and M is Eu 3+ 、Sm 3+ , Tb 3+ or Pr 3+, 0.9≤x≤1.2, under ultraviolet light excitation, it emits blue-violet light with a wavelength of 300-420nm; when ultraviolet light excitation is stopped, it emits afterglow with a wavelength of 300-420nm; under the action of mechanical force, it emits ultraviolet light with a wavelength of 300-420nm.

[0005] The preparation method of the self-activated fluorescent material comprises the following specific steps:

[0006] (1) The carbonate of A, zinc oxide, germanium oxide and the oxide of M are uniformly mixed and ground for 25 to 35 minutes to obtain a mixed powder;

[0007] (2) pre-calcining the mixed powder at a temperature of 800-1000° C. for 2-4 hours, and naturally cooling it to room temperature to obtain a pre-calcined powder;

[0008] (3) Grind the pre-fired powder, then heat it to 1000-1200℃ and calcine it for 4-8h, cool it naturally to room temperature, and grind it to obtain the self-activated fluorescent material A2Zn x GeO4:0.01M.

[0009] Preferably, the grinding in step (1) is performed by adding anhydrous ethanol and then performing wet grinding, and the amount of anhydrous ethanol added is 80% to 120% of the volume of the mixture of the carbonate of A, zinc oxide, germanium oxide and the oxide of M.

[0010] The principle of self-activated fluorescent materials emitting light in the ultraviolet light (320nm ~ 400nm) region: A self-activated fluorescent material was successfully synthesized using a high-temperature solid-phase method: A2Zn x GeO4:0.01M; where A is Li, Na, K, Rb or Cs, and M is Eu 3+ 、Sm 3+ , Tb 3+ or Pr 3+ , 0.9≤x≤1.2. The carbonate of A, zinc oxide, germanium oxide and oxide of M are mixed evenly and ground for 25 to 35 minutes to obtain a mixed powder, which is then placed in a muffle furnace and pre-baked in an air atmosphere at a temperature of 800 to 1000°C for 2 to 4 hours. The pre-baked powder is ground and placed in a muffle furnace, and then heated to 1000 to 1200°C in an air atmosphere and baked for 4 to 8 hours. The powder is then naturally cooled to room temperature and ground to obtain the self-activated fluorescent material A2Zn xGeO4: 0.01M. Under ultraviolet light excitation, this material emits blue-violet light in the 300-420nm band; when ultraviolet light excitation stops, it emits afterglow in the 300-420nm band; under the action of mechanical force, it emits ultraviolet light in the 300-420nm band. Its mechanism is that under ultraviolet light excitation, electrons are excited to the conduction band and holes are generated in the valence band of the matrix; some excited electrons jump to the excited state through the conduction band, and some holes freely pass through the valence band to reach the ground state; then the recombination of electrons and holes leads to purple emission; among them, some excited electrons are captured by traps; under the action of thermal perturbations, these trapped electrons can escape from their respective traps to the conduction band at a slower speed and move to the excited energy level, thereby generating purple long afterglow emission; when the material is excited by external force, the trapped electrons are released and recombine with the luminescence center to produce ML.

[0011] The beneficial effects of the present invention are:

[0012] (1) The luminescence of the present invention originates from the intrinsic defects of the material and does not require doping with activators such as rare earth ions, thereby avoiding the use of large amounts of rare earth metal elements;

[0013] (2) The present invention can achieve regulation of the self-activation process by adjusting the Zn ion concentration, and the introduction of rare earth ions can enhance the intensity and duration of UVA afterglow; the material can exhibit mechanoluminescence in the ultraviolet UVA region under mechanical stimulation;

[0014] (3) The self-activated fluorescent material of the present invention can emit blue-violet light in the UVA band under UVC band excitation. Its emission band range is 300-420nm. The spectral intensity within this range can be optimized by regulating the matrix. The doping of a small amount of rare earth ions can effectively improve its light storage performance, and the corresponding afterglow luminescence and mechanoluminescence are enhanced.

[0015] (4) The light emitted by the self-activated fluorescent material of the present invention has good penetrability and is easy to observe. After being treated under different environmental conditions, the light emission changes alternately between bright and dark (the emission wavelength remains unchanged), with good repeatability. The light emission intensity does not decrease with the number of repetitions, showing strong stability.

[0016] (5) The self-activated fluorescent material of the present invention can be applied to fields such as photodynamic therapy, photocatalysis, anti-counterfeiting and information storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the XRD pattern of the Li2ZnGeO4 material obtained in Example 1;

[0018] Figure 2 This is the excitation spectrum of Li2ZnGeO4 obtained in Example 1;

[0019] Figure 3 The emission spectrum of Li2ZnGeO4 obtained in Example 1;

[0020] Figure 4 This is the long afterglow spectrum of Li2ZnGeO4 obtained in Example 1;

[0021] Figure 5 This is the color coordinate diagram of Li2ZnGeO4 obtained in Example 1;

[0022] Figure 6 Li2Zn obtained in Example 2-4 x Excitation spectrum of GeO4;

[0023] Figure 7 Li2Zn obtained in Example 2-4 x Emission spectrum of GeO4;

[0024] Figure 8 A2Zn obtained in Example 5-8 x GeO4:0.01M, M is Eu 3+ 、Sm 3+ , Tb 3+ 、Pr 3+ The long afterglow spectrum of

[0025] Figure 9 This is the ML photograph of the Li2ZnGeO4 material obtained in Example 1. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0027] Example 1: A method for preparing a self-activated fluorescent material Li2ZnGeO4, the specific steps are as follows:

[0028] (1) 0.2463 g of lithium carbonate, 0.3488 g of gallium oxide, and 0.2714 g of zinc oxide were uniformly mixed to obtain a mixture, and anhydrous ethanol was added to the mixture and ground for 25 minutes to obtain a mixed powder; the amount of anhydrous ethanol added was 120% of the volume of the mixture;

[0029] (2) pre-calcining the mixed powder at 800°C for 4 hours to remove impurities and unstable structures in the material and make the crystal structure more stable. Then, naturally cooling to room temperature to obtain pre-calcined powder;

[0030] (3) Grinding the pre-calcined powder, then heating it to 1200°C and calcining it for 8 hours, naturally cooling it to room temperature, and grinding it to obtain the self-activated fluorescent material Li2ZnGeO4;

[0031] The XRD pattern of the Li2ZnGeO4 material in this embodiment is shown in Figure 1 ,from Figure 1 It can be seen that the diffraction pattern in the figure corresponds to that of the standard PDF card, and there is no stray peak, indicating that the synthesized material is a single phase;

[0032] The excitation spectrum of Li2ZnGeO4 obtained in this example is shown in Figure 2 ,from Figure 2 It can be seen that when monitoring emission at 368 nm, a broad excitation band of 200–260 nm can be observed, with a maximum at 238 nm;

[0033] The emission spectrum of Li2ZnGeO4 obtained in this example is shown in Figure 3 ,from Figure 3 It can be seen that under the excitation of 254nm, a broad emission band of 300-420nm can be observed, and the main peak of the emission spectrum is at 365nm, emitting bright blue-ultraviolet light;

[0034] The long afterglow spectrum of Li2ZnGeO4 obtained in this example is shown in Figure 4 ,from Figure 4 It can be seen that when the ultraviolet light excitation is stopped, the afterglow with a wavelength of 300-420nm is emitted;

[0035] The color coordinate diagram of Li2ZnGeO4 obtained in this embodiment is shown in FIG. Figure 5 ,from Figure 5 It can be seen that the fluorescent pink color coordinates are (0.2050, 0.1642);

[0036] ML photo of the Li2ZnGeO4 material obtained in this example Figure 9 ,from Figure 9 It can be seen that under the action of mechanical force, the material emits bright ultraviolet light.

[0037] Example 2: A self-activated fluorescent material Li2Zn 0.9 The preparation method of GeO4, the specific steps are as follows:

[0038] (1) 0.2463 g of lithium carbonate, 0.3488 g of gallium oxide, and 0.2633 g of zinc oxide were uniformly mixed to obtain a mixture, and anhydrous ethanol was added to the mixture and ground for 28 minutes to obtain a mixed powder; the amount of anhydrous ethanol added was 100% of the volume of the mixture;

[0039] (2) pre-calcining the mixed powder at 700°C for 4 hours to remove impurities and unstable structures in the material and make the crystal structure more stable, and then naturally cooling to room temperature to obtain pre-calcined powder;

[0040] (3) The pre-calcined powder was ground, then heated to 1250 ° C and calcined for 8 h, and naturally cooled to room temperature. The self-activated fluorescent material Li2Zn was obtained by grinding. 0.97 GeO4.

[0041] Example 3: A self-activated fluorescent material (Li2Zn 1.1 The preparation method of GeO4) comprises the following steps:

[0042] (1) 0.2463 g of lithium carbonate, 0.3488 g of gallium oxide, and 0.2850 g of zinc oxide were uniformly mixed to obtain a mixture, and anhydrous ethanol was added to the mixture and ground for 30 minutes to obtain a mixed powder; the amount of anhydrous ethanol added was 110% of the volume of the mixture;

[0043] (2) pre-calcining the mixed powder at 900°C for 5 hours to remove impurities and unstable structures in the material and make the crystal structure more stable, and then naturally cooling to room temperature to obtain pre-calcined powder;

[0044] (3) The pre-calcined powder was ground, then heated to 1200 ° C and calcined for 8 h, and naturally cooled to room temperature. The self-activated fluorescent material Li2Zn was obtained by grinding. 1.05 GeO4.

[0045] Example 4: A self-activated fluorescent material Li2Zn 1.2 The preparation method of GeO4, the specific steps are as follows:

[0046] (1) 0.2463 g of lithium carbonate, 0.3488 g of gallium oxide, and 0.2903 g of zinc oxide were uniformly mixed to obtain a mixture, and anhydrous ethanol was added to the mixture and ground for 35 minutes to obtain a mixed powder; the amount of anhydrous ethanol added was 105% of the volume of the mixture;

[0047] (2) pre-calcining the mixed powder at 800°C for 5 hours to remove impurities and unstable structures in the material and make the crystal structure more stable, and then naturally cooling to room temperature to obtain pre-calcined powder;

[0048] (3) The pre-calcined powder was ground, then heated to 1200 ° C and calcined for 7 hours, and naturally cooled to room temperature. The self-activated fluorescent material Li2Zn was obtained by grinding. 1.07 GeO4;

[0049] Li2Zn obtained in Example 2-4 x The excitation spectrum of GeO4 is shown in Figure 6 ,from Figure 6 It can be seen that when monitoring emission at 368 nm, a broad excitation band of 200-260 nm can be observed. 2+ As the luminescence of the material increases,

[0050] Li2Zn obtained in Example 2-4 x The emission spectrum of GeO4 is shown in Figure 7 ,from Figure 7 It can be seen that under the excitation of 254nm, a broad emission band of 300-420nm can be observed. 2+ The increase of the emission light intensity proves that the Zn 2+ By adjusting the concentration, the self-activation process can be regulated.

[0051] Example 5: A self-activated fluorescent material (Li2Zn 0.99 GeO4:0.01Eu 3+ ), the specific steps are as follows:

[0052] (1) 0.2463 g of lithium carbonate, 0.3488 g of gallium oxide, 0.2633 g of zinc oxide, and 0.0059 g of europium oxide were uniformly mixed to obtain a mixture, and anhydrous ethanol was added to the mixture and ground for 25 minutes to obtain a mixed powder; the amount of anhydrous ethanol added was 115% of the volume of the mixture; Eu 3+ The doping amount of Li2ZnGeO4 is 0.6%;

[0053] (2) pre-calcining the mixed powder at 950°C for 4 hours to remove impurities and unstable structures in the material and make the crystal structure more stable, and then naturally cooling to room temperature to obtain pre-calcined powder;

[0054] (3) The pre-calcined powder was ground, then heated to 1150 ° C and calcined for 8 h, and naturally cooled to room temperature. The self-activated fluorescent material Li2ZnGeO4:Eu was obtained by grinding. 3+ .

[0055] Example 6: A self-activated fluorescent material (Li2Zn 0.99 GeO4:0.01Sm 3+ ), the specific steps are as follows:

[0056] (1) 0.2463 g of lithium carbonate, 0.3488 g of gallium oxide, 0.2633 g of zinc oxide, and 0.0058 g of samarium oxide were uniformly mixed to obtain a mixture, and anhydrous ethanol was added to the mixture and ground for 30 min to obtain a mixed powder; the amount of anhydrous ethanol added was 120% of the volume of the mixture; Sm 3+ The doping amount of Li2ZnGeO4 is 0.6%;

[0057] (2) pre-calcining the mixed powder at 800°C for 4 hours to remove impurities and unstable structures in the material and make the crystal structure more stable, and then naturally cooling to room temperature to obtain pre-calcined powder;

[0058] (3) The pre-calcined powder was ground, then heated to 1200 ° C and calcined for 8 h, and naturally cooled to room temperature, and the self-activated fluorescent material Li2ZnGeO4:Sm was obtained by grinding. 3+ .

[0059] Example 7: A self-activated fluorescent material (Li2Zn 0.99 GeO4:0.01Tb 3+ ), the specific steps are as follows:

[0060] (1) 0.2463 g of lithium carbonate, 0.3488 g of gallium oxide, 0.2633 g of zinc oxide, and 0.0062 g of terbium oxide were uniformly mixed to obtain a mixture, and anhydrous ethanol was added to the mixture and ground for 35 minutes to obtain a mixed powder; the amount of anhydrous ethanol added was 110% of the volume of the mixture; Tb 3+ The doping amount of Li2ZnGeO4 is 0.7%;

[0061] (2) pre-calcining the mixed powder at 950°C for 4 hours to remove impurities and unstable structures in the material and make the crystal structure more stable, and then naturally cooling to room temperature to obtain pre-calcined powder;

[0062] (3) The pre-calcined powder was ground, then heated to 1150 ° C and calcined for 8 h, and naturally cooled to room temperature. The self-activated fluorescent material Li2ZnGeO4:Tb was obtained by grinding. 3+ .

[0063] Example 8: A self-activated fluorescent material (Li2Zn 0.99 GeO4:0.01Pr 3+ ), the specific steps are as follows:

[0064] (1) 0.2463 g of lithium carbonate, 0.3488 g of gallium oxide, 0.2633 g of zinc oxide, and 0.0055 g of praseodymium oxide were uniformly mixed to obtain a mixture, and anhydrous ethanol was added to the mixture and ground for 35 minutes to obtain a mixed powder; the amount of anhydrous ethanol added was 115% of the volume of the mixture; Pr 3+ The doping amount of Li2ZnGeO4 is 0.6%;

[0065] (2) pre-calcining the mixed powder at 800°C for 4 hours to remove impurities and unstable structures in the material and make the crystal structure more stable, and then naturally cooling to room temperature to obtain pre-calcined powder;

[0066] (3) The pre-calcined powder was ground, then heated to 1200 ° C and calcined for 8 h, and naturally cooled to room temperature. The self-activated fluorescent material Li2ZnGeO4:Pr 3+ ;

[0067] A2ZnGeO4 obtained in Example 5-8: 0.01M, M is Eu 3+ 、Sm 3+ , Tb 3+ 、Pr 3+ The long afterglow spectrum of Figure 8 ,from Figure 8 It can be seen that after the ultraviolet light excitation is stopped, the afterglow with a wavelength of 300-420nm is emitted, and the Eu-doped 3+ 、Sm 3+ , Tb 3+ 、Pr 3+ The afterglow intensity of the samples was enhanced. This proves that the afterglow process can be effectively enhanced by doping with rare earth ions.

[0068] The above describes the specific embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

Claims

1. A self-activated fluorescent material, characterized in that: The general chemical formula is A2Zn x GeO4:0.01M; where A is Li, Na, K, Rb or Cs, and M is Eu 3+ 、Sm 3+ , Tb 3+ or Pr 3+ , 0.9≤x≤1.2, under ultraviolet light excitation, it emits blue-violet light with a wavelength of 300-420nm; when ultraviolet light excitation is stopped, it emits afterglow with a wavelength of 300-420nm; under the action of mechanical force, it emits ultraviolet light with a wavelength of 300-420nm.

2. The method for preparing the self-activated fluorescent material according to claim 1, wherein: The specific steps are as follows: (1) The carbonate of A, zinc oxide, germanium oxide and the oxide of M are uniformly mixed and ground for 25 to 35 minutes to obtain a mixed powder; (2) pre-calcining the mixed powder at a temperature of 800-1000° C. for 2-4 hours, and naturally cooling it to room temperature to obtain a pre-calcined powder; (3) Grind the pre-fired powder, then heat it to 1000-1200℃ and calcine it for 4-8h, cool it naturally to room temperature, and grind it to obtain the self-activated fluorescent material A2Zn x GeO4:0.01M.

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