Germanate-based long-afterglow luminescent material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of inorganic luminescent materials, and discloses a germanate-based long-afterglow luminescent material as well as a preparation method and application thereof. The luminescent material is obtained by taking MReGeO4 (M = Li or Na, Re = Y, Lu or Gd) as a matrix and introducing doping ions Bi < 3 + > and Ln < 3 + >, the chemical formula of the luminescent material is M < 1-x > Re < 1-y > GeO4: xBi < 3 + >, yLn < 3 + >. Wherein x is the molar doping concentration of the doping ion Bi < 3 + > in the alkali metal ion Li < + > or Na < + > in the matrix, and x is more than 0 and less than or equal to 0.010; y is the molar doping concentration of doped Ln < 3 + > ions (Ln = one of Eu, Tb, Pr or Yb) in Re < 3 + > in the matrix, and y is more than or equal to 0 and less than or equal to 0.001. Based on trap engineering and band gap engineering, regulation and control of multi-mode fluorescence properties such as photoluminescence, afterglow and light / thermal excitation fluorescence are achieved, particularly, multi-color multi-mode fluorescent printing dynamic information storage and encryption are achieved, and a material basis and a physical prototype are provided for next-generation fluorescent printing information storage and anti-counterfeiting technologies.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic luminescent materials, and particularly relates to a deep-trap germanate-based long-afterglow luminescent material applied to information storage and encryption, a preparation method thereof, and uses thereof. Background Art

[0002] According to the "DATA.AGE 2025" report, it is estimated that by 2025, the global data will reach 163 ZB, with more than 20,000 GB per capita. However, the traditional hybrid hard disk storage technology has an information storage crisis due to its two-dimensional spatial resolution and high energy consumption limitations. Therefore, there is an urgent need for new storage materials and technologies with high capacity and non-volatile storage capabilities. Storage phosphors with photo / thermal stimulated luminescence (PSL / TSL) are considered the most promising fourth-generation optical information storage materials due to their ultra-fast speed and low energy consumption. Under high-energy radiation (such as X-rays or ultraviolet light), information can be quickly written, and then the information can be extracted under thermal / light and other stimulations to complete the information access work. As a representative example, BaFBr:Eu 2+ As a photo-stimulated phosphor has been successfully used as an imaging plate in computed radiography. In addition, in order to further improve the optical information storage capacity of afterglow materials, based on photon multiplexing technology, some typical strategies such as wavelength multiplexing technology, intensity multiplexing technology, polarization multiplexing technology, and spatial agent and multi-layer multiplexing technology have been developed to further improve the information storage capacity. Although some progress has been made, the stimulated fluorescence intensity has not reached the threshold of information storage applications. In particular, the stored energy dissipates naturally over time in the form of afterglow, directly affecting the storage lifetime of the signal and the resolution of the extracted signal. The key core reason is the lack of control over trap states. The development of new-performance long-afterglow materials is still carried out through continuous trial and error.

[0003] So far, the recognized co-doping is the most effective method to improve the trap density and distribution. A milestone work is the energy level distribution schematic model for predicting the trap depth of lanthanide-doped ions in the matrix based on the vacuum or matrix binding energy (VRBE), which is used to explain the positions of lanthanide-doped inorganic compounds as luminescence centers and trap centers in the bandgap. It enables people to compare the positions of defect energy levels in different matrices in the matrix energy bandgap under the same reference energy. This model can guide the selection of the types and properties of doping ions as defects in the matrix.

[0004] Having (Xe)4f 14 5d 10 6s 2 6p 1 Configuration of Bi 3+Ions are excellent activators and sensitizers for luminescent materials. There are few reports on the afterglow luminescence phenomenon of bismuth. 3+ Doped afterglow phosphors were discovered. Few reports discuss Bi 3+ The mechanism of the capture and release of charge carriers in doped phosphors has always been an open question, which directly hinders the development of efficient afterglow materials. 5-x Ga x O 12 :0.005Ce 3+ ,0.005Bi 3+ Medium, Bi 3+ As an electron trap. In recent research reports, Bi 3+ In NaLuGeO4:0.05Bi 3+ ,0.005Cr 3+ In long afterglow materials, Bi 3+ As a hole trap center. Therefore, it can be inferred that Bi 3+ As electron traps or hole traps are related to the local environment of the matrix, this provides a new idea for trap regulation. Based on this, in order to further increase the trap density and distribution, and thus increase the storage capacity of multi-color and multi-mode fluorescence information, the present invention intends to provide a new long afterglow luminescent material. Summary of the invention

[0005] Aiming at the problem of insufficient information storage capacity in afterglow materials, the present invention designs and constructs Bi based on trap engineering and bandgap engineering. 3+ and Ln 3+ The electron-hole pair trap structure is further enriched and deepened, providing a high-density deep-trap germanate-based long afterglow luminescent material and its preparation method for information storage and encryption. The present invention greatly improves the encrypted information storage capacity by regulating the energy storage trap of the long afterglow material and allowing the conduction band and the valence band to participate in the long-distance transport of carriers at the same time. It not only has theoretical significance, but also has economic value and social significance.

[0006] In order to achieve the above technical objectives, the specific technical solutions provided by the present invention are as follows:

[0007] In a first aspect, the present invention provides a germanate-based long afterglow luminescent material, wherein the luminescent material is based on MReGeO4 and is doped with Bi 3+ and Ln 3+ The chemical formula of the luminescent material is M 1-x Re 1-y GeO4:xBi 3+ ,yLn 3+ ;

[0008] Among them, M is Li or Na, Re is Y, Lu or Gd, and Ln is one of Eu, Tb, Pr or Yb; 0 < x ≤ 0.010, 0 ≤ y ≤ 0.001.

[0009] In the second aspect of the present invention, a preparation method of the luminescent material is provided, including the following steps:

[0010] According to the chemical formula of the luminescent material M 1-x Re 1-y GeO4:xBi 3+ ,yLn 3+ in stoichiometric ratio, weigh the M source, Re source, Ge source, O source, Bi source and Ln source, mix them to obtain a mixed powder, and calcine it to obtain the luminescent material. Among them, the M source is a Na or Li source, and the Re source is one of a Lu source, a Y source or a Gd source.

[0011] Preferably, the M source, Re source, Ge source, Bi source and Ln source are all oxygen-containing compounds containing the corresponding elements;

[0012] The O source is jointly provided by the oxygen-containing compounds.

[0013] Preferably, the oxygen-containing compound is any one or more of oxides or nitrates.

[0014] Preferably, the calcination is carried out in an air atmosphere, heated to 1300 - 1400 °C at a heating rate of 2 - 4 °C / min, and calcined for 8 - 10 h. Preferably, the preparation raw materials are ground for 0.5 - 1 h during mixing.

[0015] In the third aspect of the present invention, a use of the luminescent material as a material for information storage or encryption is provided.

[0016] Preferably, the luminescent material is used for multi-dimensional visual information storage or encryption.

[0017] Preferably, the information storage or encryption is achieved by irradiating with ultraviolet light for information writing.

[0018] Preferably, the information storage or encryption is achieved by controlling to receive light or heat again at a specific time frame after ultraviolet pre-irradiation.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. The present invention selects germanate capable of providing three different cation sites as the matrix. Bi 3+ has a radius similar to that of Na + and a valence similar to that of Lu 3+ and can serve as both a luminescence center and an electron / hole defect center. Typical Ln 3+(Ln = Eu, Tb, Pr or Yb) as Bi 3+ The paired objects of hole / electron defects of electron / hole defects, a series of electron-hole defect pairs M 1-x Re 1-y GeO4:xBi 3+ ,yLn 3+ with enhanced trap density and controllable afterglow emission have been successfully synthesized. Based on the construction of Bi 3+ -Ln 3+ electron-hole defect pairs, both the conduction band and valence band participate in the remote carrier transport process, improving the M 1-x Re 1-y GeO4:xBi 3+ ,yLn 3+ afterglow phosphor's effective trap density and afterglow characteristics, and storage and encryption have been successfully achieved.

[0021] 2. Based on the afterglow fluorescence mechanism of carrier capture and release mediated by electron-hole defect pairs, using Bi 3+ and Ln 3+ simultaneously as trap makers and fluorescence centers, the synthesized long afterglow luminescent materials have tunable afterglow luminescence, excellent multi-color and multi-mode afterglow, and can meet specific requirements.

[0022] 3. The Ln 3+ co-doped M 1-x Re 1-y GeO4:xBi 3+ ,yLn 3+ phosphor not only significantly increases the trap density but also regulates the trap distribution, making the M 1-x Re 1-y GeO4:xBi 3+ ,yLn 3+ phosphor more suitable for information storage and encryption. At the same time, by controlling the ultraviolet pre-irradiation temperature, multi-dimensional visual information storage has been recorded on a single-layer phosphor film.

[0023] 4. The present invention proposes a multi-level trap multiplexing for storing different optical data recording and encryption. By storing multiple individual addressable dynamic encryption patterns in the same fluorescence recording layer, it provides new ideas and technical prototypes for the design and preparation of next-generation optical information storage and encryption materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 are the XRD patterns and standard data (PDF#02-3479) of the phosphors in Example 1 and Example 5;

[0025] Figure 2Schematic diagram of [MO6] and [LuO6] octahedra for Comparative Example 1;

[0026] Figure 3 SEM photograph and elemental mapping of the phosphor in Example 1, crystal structure of the unit cell, and comparison of the coordination environments of Bi 3+ ions and Ln 3+ ion substitution;

[0027] Figure 4 Comparison of thermoluminescence spectra of the phosphors in Examples 1 to 5;

[0028] Figure 5 Thermoluminescence curves (A) of the phosphors in Examples 9 to 11 and thermoluminescence curves (B) of the phosphors in Examples 12 to 14;

[0029] Figure 6 Thermoluminescence spectra of the phosphors in Examples 6 to 8;

[0030] Figure 7 Photoluminescence excitation spectrum (A), emission spectrum (B), afterglow emission spectrum (C), and afterglow decay curve (D) of the phosphors in Examples 1 to 5;

[0031] Figure 8 Variable-temperature afterglow emission spectrum of the phosphor in Example 1;

[0032] Figure 9 Variable-temperature thermoluminescence curve of the phosphor in Example 1;

[0033] Figure 10 Time-delayed thermoluminescence curve of the phosphor in Example 1;

[0034] Figure 11 Variable-temperature thermoluminescence curves of the phosphors in Example 2 (A), Example 3 (B), and Example 4 (C);

[0035] Figure 12 Curves showing the alternating appearance of excitation fluorescence and excitation afterglow fluorescence under pulsed infrared laser excitation on the natural decay curves of the phosphors in Example 1, Example 2 (A), Example 3 (B), and Example 4 (C);

[0036] Figure 13 Photoluminescence excitation spectrum and afterglow excitation spectrum of the phosphor in Example 1;

[0037] Figure 14 High-resolution xps spectra of Bi 3+ :4f for the phosphors in Example 1 (A) and Example 5 (B);

[0038] Figure 15 PL, PersL, TSL, and PSL mechanisms of the Bi-Ln electron-hole pair trap material under ultraviolet light irradiation;

[0039] Figure 16 The multi-modal fluorescent pattern of the "Butterfly Loves Flower" pattern printed with the phosphors of Examples 1-4 is used for information storage and encryption; a. Structure diagram of the phosphor "Butterfly Loves Flower" pattern; b. Photoluminescent multicolor pattern under the excitation of light sources selected from ultraviolet to blue; c. Afterglow dynamic encryption pattern at different delay times after charging with 254 nm ultraviolet light; d. Photo-excitation pattern information extracted under the irradiation of 980 nm or 808 nm near-infrared laser at a certain time frame after the afterglow disappears after ultraviolet light charging; e. Thermally excited multicolor fluorescent pattern information extracted under different thermal assistance; f. Different information is stored in different depth traps by controlling the temperature switch. The specific storage process is described as follows: only deep traps are selected to be filled under the thermal assistance of 130 °C, deep traps and intermediate-depth traps are selected to be filled under the thermal assistance of 100 °C, and all traps are filled at room temperature. Combining the different trap distributions of the four phosphor materials, the butterfly is read out at room temperature, the butterfly and the leaf are read out under the temperature excitation of 80 °C (353 K), and finally, at 150 °C (423 K), the butterfly, the leaf and the rose are read out, realizing the storage of multi-dimensional information in a single physical phosphor recording layer. Among them, the butterfly is charged at T charge = RT, the leaf at T charge = 353 K, the rose flower T charge = 423 K.

[0040] Figure 17 The multi-modal image of the "Flower" pattern printed with the phosphor of Example 6 is used for information storage and encryption; a. Flower pattern under sunlight; b. PL image obtained under the irradiation of 236 nm ultraviolet light, and pure blue and pure red images are obtained with the assistance of a filter; c. PersL image at different delay times after charging with 236 nm ultraviolet light; d. PSL image under the irradiation of 980 nm or 808 nm near-infrared laser (0.6 W); e. TSL image pre-irradiated with 236 nm; f. Multi-dimensional information stored in a single recording layer by controlling the temperature; the above information is written under the irradiation of 236 nm ultraviolet lamp at different temperatures. Among them, the leaf is at T charge = RT, the small flower at T charge = 353 K, the large flower at T charge = 423 K. Detailed implementation manners

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0042] The present invention provides a deep-trap long-afterglow luminescent material, which is obtained by using MReGeO4 as a matrix and introducing doping ions Bi and Ln 3+ and the chemical formula of the luminescent material is M 1-x Re 1-y GeO4:xBi3+ , yLn 3+ ;

[0043] Among them, M is Li or Na, Re is Y, Lu or Gd, and Ln is one of Eu, Tb, Pr or Yb;

[0044] x is the doping ion Bi 3+ occupying M 1-x Re 1-y in NaReGeO4, and 0 < x ≤ 0.010; y is the doping ion Ln 3+ occupying Na 1-x Lu 1-y in NaLuGeO4, and 0 ≤ y ≤ 0.001.

[0045] The preparation method of the luminescent material provided by the present invention is as follows:

[0046] According to the stoichiometric ratio in the chemical formula M 1-x Re 1-y GeO4:xBi 3+ , yLn 3+ , weigh the corresponding masses of each raw material for preparation, namely the Na / Li source, Re source, Ge source, O source, Bi source, and Ln source; the Re source is one of the Lu source, Y source or Gd source;

[0047] After mixing the weighed Na / Li source, Re source, Ge source, O source, and the doping ion Bi source and Ln source, grind and mix them thoroughly to obtain a mixed powder;

[0048] Calcine the mixed powder in an air atmosphere at 1000 - 1300 °C, grind it into powder to obtain the luminescent material.

[0049] It should be noted that in order to avoid introducing other elements and impurities in the present invention, preferably the Na / Li source, Re source, Ge source, and the doping ion Bi source and Ln source are all oxygen-containing compounds containing the corresponding elements; the O source is provided jointly by each oxygen-containing compound containing the corresponding elements. Among them, the oxygen-containing compound is any one or more of oxides, carbonates and nitrates.

[0050] Considering factors such as minimizing impurity introduction, good chemical stability and moderate price, the present invention more preferably uses Na2CO3 as the Na source, rare earth oxides as the Re source, and GeO2 as the Ge source.

[0051] By regulating the type of doping ion Ln and the molar doping concentration of doping ion Ln in Re in the germanate matrix, the fluorescence properties of the luminescent material are regulated, realizing the regulation of fluorescence properties such as photoluminescence, afterglow, and thermally stimulated fluorescence. In particular, the abnormal thermal quenching phenomenon and thermally enhanced trap filling phenomenon of the prepared phosphor are realized, achieving high-capacity information writing and multi-level information reading, providing a material basis and technical solution for the fourth-generation optical information storage.

[0052] In order to fully mix the raw materials for preparation, the present invention preferably adopts ball milling or manual grinding to mix the raw materials, and the grinding duration is about 0.5 - 1 h. The obtained mixed powder is delicate and has a size of 1 - 2 μm.

[0053] The present invention uses a direct calcination method to calcine the above-mentioned mixed powder. In an air atmosphere, it is calcined at 1000 - 1300 °C for 4 - 8 h, and the heating rate during calcination is 2 - 4 °C / min to ensure that the material can be heated sufficiently and evenly, thereby achieving the best crystallinity.

[0054] Example 1

[0055] This example provides a germanate-based long afterglow luminescent material. In this example, M is Li, Re is Lu, Ln is Eu, and x and y are 1.0% and 0.1% respectively. Therefore, the molecular formula of the luminescent material in this example is Li 0.99 Lu 0.999 GeO4:1.0% Bi 3+ ,0.1% Eu 3+ . And its preparation method is as follows:

[0056] Weigh 0.0732 g of Li2CO3, 0.3975 g of Lu2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3, and 0.0004 g of Eu2O3 solids according to the molar mass ratio of the above chemical formula, mix them in an agate mortar and grind them for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, sinter it at 1250 °C for 6 h, and then grind it thoroughly to obtain the molecular formula Li 0.99 Lu 0.999 GeO4:1.0% Bi 3+ ,0.1% Eu 3+ luminescent material.

[0057] Example 2

[0058] This embodiment provides a germanate-based long afterglow luminescent material. In this embodiment, M is Li, Re is Lu, Ln is Tb, and x and y are 1.0% and 0.1% respectively. Therefore, the molecular formula of the luminescent material in this embodiment is Li 0.99 Lu 0.999 GeO4: 1.0% Bi 3+ , 0.1% Tb 3+ . And its preparation method is as follows:

[0059] Weigh 0.0732 g of Li2CO3, 0.3975 g of Lu2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3 and 0.0004 g of Tb4O7 solids according to the molar mass ratio of the above chemical formula, mix them in an agate mortar and grind them thoroughly for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, sinter it at 1250 °C for 6 h and then grind it thoroughly to obtain the molecular formula of Li 0.99 Lu 0.999 GeO4: 1.0% Bi 3+ , 0.1% Tb 3+ luminescent material.

[0060] Example 3

[0061] This embodiment provides a germanate-based long afterglow luminescent material. In this embodiment, M is Li, Re is Lu, Ln is Pr, and x and y are 1.0% and 0.1% respectively. Therefore, the molecular formula of the luminescent material in this embodiment is Li 0.99 Lu 0.999 GeO4: 1.0% Bi 3+ , 0.1% Pr 3+ . And its preparation method is as follows:

[0062] Weigh 0.0732 g of Li2CO3, 0.3975 g of Lu2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3 and 0.0004 g of Pr6O 11 solids, mix them in an agate mortar and grind them thoroughly for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, sinter it at 1250 °C for 6 h and then grind it thoroughly to obtain the molecular formula of Li 0.99 Lu 0.999 GeO4: 1.0% Bi 3+ , 0.1% Pr 3+ luminescent material.

[0063] Example 4

[0064] This embodiment provides a germanate-based long afterglow luminescent material. In this embodiment, M is Li, Re is Lu, Ln is Yb, and x and y are 1.0% and 0.1% respectively. Therefore, the molecular formula of the luminescent material in this embodiment is Li 0.99 Lu 0.999 GeO4: 1.0% Bi 3+ , 0.1% Yb 3+ . And its preparation method is as follows:

[0065] Weigh 0.0732 g of Li2CO3, 0.3975 g of Lu2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3 and 0.0004 g of Yb2O3 solids according to the molar mass ratio of the above chemical formula, mix them, and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, and sinter it at 1250 °C for 6 h and then grind it thoroughly to obtain the molecular formula of Li 0.99 Lu 0.999 GeO4: 1.0% Bi 3+ , 0.1% Yb 3+ luminescent material.

[0066] Example 5

[0067] This embodiment provides a germanate-based long afterglow luminescent material. In this embodiment, M is Li, Re is Lu, and x is 1.0%. Therefore, the molecular formula of the luminescent material in this embodiment is Li 0.99 LuGeO4: 1.0% Bi 3+ . And its preparation method is as follows:

[0068] Weigh 0.0732 g of Li2CO3, 0.3979 g of Lu2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3 solids according to the molar mass ratio of the above chemical formula, mix them, and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, and sinter it at 1250 °C for 6 h and then grind it thoroughly to obtain the molecular formula of Li 0.99 LuGeO4: 1.0% Bi 3+ luminescent material.

[0069] Example 6

[0070] This embodiment provides a germanate-based long afterglow luminescent material. In this embodiment, M is Na, Re is Lu, Ln is Eu, and x and y are 1.0% and 0.1% respectively. Therefore, the molecular formula of the luminescent material in this embodiment is Na 0.99 Lu 0.999GeO4:1.0%Bi 3+ ,0.1%Eu 3+ . And its preparation method is as follows:

[0071] 0.1049 g Na2CO3, 0.3979 g Lu2O3, 0.2133 g GeO2, 0.0047 g Bi2O3 and 0.0004 g Eu2O3 solids were weighed and mixed according to the molar mass ratio of the above chemical formula, and fully ground in an agate mortar for 1 hour to obtain a mixed powder; the mixed powder was placed in a crucible, heated to 1250°C at a heating rate of 2°C / min in an air atmosphere, sintered at 1250°C for 6 hours, and then fully ground to obtain a molecule with the molecular formula of Na 0.99 Lu 0.999 GeO4:1.0%Bi 3+ ,0.1%Eu 3+ of luminous material.

[0072] Example 7

[0073] This embodiment provides a germanate-based long afterglow luminescent material. In this embodiment, M is Na, Re is Lu, Ln is Tb, x and y are 1.0% and 0.1% respectively, so the molecular formula of the luminescent material in this embodiment is Na 0.99 Lu 0.999 GeO4:1.0%Bi 3+ ,0.1%Tb 3+ . And its preparation method is as follows:

[0074] 0.1049 g Na2CO3, 0.3979 g Lu2O3, 0.2133 g GeO2, 0.0047 g Bi2O3 and 0.0004 g Tb4O7 solids were weighed and mixed according to the molar mass ratio of the above chemical formula, and fully ground in an agate mortar for 1 hour to obtain a mixed powder; the mixed powder was placed in a crucible, heated to 1250°C at a heating rate of 2°C / min in an air atmosphere, sintered at 1250°C for 6 hours, and then fully ground to obtain a molecule with the molecular formula of Na 0.99 Lu 0.999 GeO4:1.0%Bi 3+ ,0.1%Tb 3+ of luminous material.

[0075] Example 8

[0076] This embodiment provides a germanate-based long afterglow luminescent material. In this embodiment, M is Na, Re is Lu, and x is 1.0%. Therefore, the molecular formula of the luminescent material in this embodiment is Na 0.99 LuGeO4:1.0%Bi 3+ . And its preparation method is as follows:

[0077] Weigh 0.1049 g of Na2CO3, 0.3979 g of Lu2O3, 0.2133 g of GeO2 and 0.0047 g of Bi2O3 solids according to the molar mass ratio of the above chemical formula. After mixing, grind them in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, and calcine it at 1250 °C for 6 h and then grind it into powder to obtain Na 0.99 LuGeO4: 1.0% Bi 3+ luminescent material.

[0078] Example 9

[0079] This example provides a germanate-based long afterglow luminescent material. In this example, M is Li, Re is Y, Ln is Eu, and x and y are 1.0% and 0.1% respectively. Therefore, the chemical formula of the luminescent material in this example is Li 0.99 Y 0.999 GeO4: 1.0% Bi 3 + , 0.1% Eu 3+ . And its preparation method is as follows:

[0080] Weigh 0.0732 g of Li2CO3, 0.2256 g of Y2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3 and 0.0004 g of Eu2O3 solids according to the molar mass ratio of the above chemical formula. Mix them and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, and calcine it at 1250 °C for 6 h and then grind it thoroughly to obtain the chemical formula of Li 0.99 Y 0.999 GeO4: 1.0% Bi 3+ , 0.1% Eu 3+ luminescent material.

[0081] Example 10

[0082] This example provides a germanate-based long afterglow luminescent material. In this example, M is Li, Re is Y, Ln is Tb, and x and y are 1.0% and 0.1% respectively. Therefore, the chemical formula of the luminescent material in this example is Li 0.99 Y 0.999 GeO4: 1.0% Bi 3 + , 0.1% Tb 3+ . And its preparation method is as follows:

[0083] Weigh 0.0732 g of Li2CO3, 0.2256 g of Y2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3 and 0.0004 g of Tb4O7 solids according to the molar mass ratio of the above chemical formula, mix them, and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, sinter it at 1250 °C for 6 h, and then grind it thoroughly to obtain a luminous material with the molecular formula Li 0.99 Y 0.999 GeO4: 1.0% Bi 3+ , 0.1% Tb 3+ .

[0084] Example 11

[0085] This example provides a germanate-based long-afterglow luminous material. In this example, M is Li, Re is Y, and x is 1.0%. Therefore, the molecular formula of the luminous material in this example is Li 0.99 YGeO4: 1.0% Bi 3+ . And its preparation method is as follows:

[0086] Weigh 0.0732 g of Li2CO3, 0.2258 g of Y2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3 solids according to the molar mass ratio of the above chemical formula, mix them, and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, sinter it at 1250 °C for 6 h, and then grind it thoroughly to obtain a luminous material with the molecular formula Li 0.99 YGeO4: 1.0% Bi 3+ .

[0087] Example 12

[0088] This example provides a germanate-based long-afterglow luminous material. In this example, M is Li, Re is Gd, Ln is Eu, and x and y are 1.0% and 0.1% respectively. Therefore, the molecular formula of the luminous material in this example is Li 0.99 Gd 0.999 GeO4: 1.0% Bi 3+ , 0.1% Eu 3+ . And its preparation method is as follows:

[0089] Weigh 0.0732 g of Li2CO3, 0.3623 g of Gd2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3 and 0.0004 g of Eu2O3 solids according to the molar mass ratio of the above chemical formula, mix them, and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, and sinter it at 1250 °C for 6 h and then grind it thoroughly to obtain a luminous material with the chemical formula Li 0.99 Gd 0.999 GeO4: 1.0% Bi 3+ , 0.1% Eu 3+ .

[0090] Example 13

[0091] This example provides a germanate-based long afterglow luminescent material. In this example, M is Li, Re is Gd, Ln is Tb, and x and y are 1.0% and 0.1% respectively. Therefore, the chemical formula of the luminescent material in this example is Li 0.99 Gd 0.999 GeO4: 1.0% Bi 3+ , 0.1% Tb 3+ . And its preparation method is as follows:

[0092] Weigh 0.0732 g of Li2CO3, 0.3623 g of Gd2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3 and 0.0004 g of Tb4O7 solids according to the molar mass ratio of the above chemical formula, mix them, and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, and sinter it at 1250 °C for 6 h and then grind it thoroughly to obtain a luminous material with the chemical formula Li 0.99 Gd 0.999 GeO4: 1.0% Bi 3+ , 0.1% Tb 3+ .

[0093] Example 14

[0094] This example provides a germanate-based long afterglow luminescent material. In this example, M is Li, Re is Gd, and x is 1.0%. Therefore, the chemical formula of the luminescent material in this example is Li 0.99 GdGeO4: 1.0% Bi 3+ . And its preparation method is as follows:

[0095] Weigh 0.0732 g of Li2CO3, 0.3626 g of Gd2O3, 0.2133 g of GeO2, and 0.0047 g of Bi2O3 solids according to the molar mass ratio of the above chemical formula, mix them, and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, and sinter it at 1250 °C for 6 h and then grind it thoroughly to obtain a luminescent material with the molecular formula Li 0.99 GdGeO4: 1.0% Bi 3+ .

[0096] Example 15

[0097] This example provides a germanate-based long-afterglow luminescent material. In this example, M is Li, Re is Lu, Ln is Eu, and x and y are 0.1% and 0.1% respectively. Therefore, the molecular formula of the luminescent material in this example is Li 0.999 Lu 0.999 GeO4: 0.1% Bi 3+ , 0.1% Eu 3+ . And its preparation method is as follows:

[0098] Weigh 0.0732 g of Li2CO3, 0.3975 g of Lu2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3, and 0.0004 g of Eu2O3 solids according to the molar mass ratio of the above chemical formula, mix them, and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, and sinter it at 1250 °C for 6 h and then grind it thoroughly to obtain a luminescent material with the molecular formula Li 0.999 Lu 0.999 GeO4: 0.1% Bi 3+ , 0.1% Eu 3+ .

[0099] Example 16

[0100] This example provides a germanate-based long-afterglow luminescent material. In this example, M is Li, Re is Lu, Ln is Eu, and x and y are 0.1% and 0.01% respectively. Therefore, the molecular formula of the luminescent material in this example is Li 0.999 Lu 0.9999 GeO4: 0.1% Bi 3+ , 0.01% Eu 3+ . And its preparation method is as follows:

[0101] Weigh 0.0732 g of Li2CO3, 0.3975 g of Lu2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3 and 0.0004 g of Eu2O3 solids according to the molar mass ratio of the above chemical formula, mix them, and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, and calcine it at 1250 °C for 6 h and then grind it thoroughly to obtain a luminescent material with the molecular formula Li 0.999 Lu 0.9999 GeO4: 0.1% Bi 3+ , 0.01% Eu 3+ .

[0102] Example 17

[0103] This example provides a germanate-based long afterglow luminescent material. In this example, M is Li, Re is Lu, Ln is Eu, and x and y are 1.0% and 0.01% respectively. Therefore, the molecular formula of the luminescent material in this example is Li 0.99 Lu 0.9999 GeO4: 1.0% Bi 3+ , 0.01% Eu 3+ . And its preparation method is as follows:

[0104] Weigh 0.0732 g of Li2CO3, 0.3975 g of Lu2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3 and 0.0004 g of Eu2O3 solids according to the molar mass ratio of the above chemical formula, mix them, and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, and calcine it at 1250 °C for 6 h and then grind it thoroughly to obtain a luminescent material with the molecular formula Li 0.99 Lu 0.9999 GeO4: 1.0% Bi 3+ , 0.01% Eu 3+ .

[0105] Example 18

[0106] This example provides a germanate-based long afterglow luminescent material. In this example, M is Li, Re is Lu, Ln is Eu, and x and y are 0.5% and 0.05% respectively. Therefore, the molecular formula of the luminescent material in this example is Li 0.995 Lu 0.9995 GeO4: 0.5% Bi 3+ , 0.05% Eu 3+ . And its preparation method is as follows:

[0107] Weigh 0.0732 g of Li2CO3, 0.3975 g of Lu2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3 and 0.0004 g of Eu2O3 solids according to the molar mass ratio of the above chemical formula, mix them, and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, sinter it at 1250 °C for 6 h, and then grind it thoroughly to obtain a luminescent material with the molecular formula Li 0.995 Lu 0.9995 GeO4: 0.5% Bi 3+ , 0.05% Eu 3+ .

[0108] Example 19

[0109] This example provides a germanate-based long afterglow luminescent material. In this example, M is Na, Re is Lu, Ln is Eu, and x and y are 0.5% and 0.05% respectively. Therefore, the molecular formula of the luminescent material in this example is Na 0.995 Lu 0.9995 GeO4: 0.5% Bi 3+ , 0.05% Eu 3+ . And its preparation method is as follows:

[0110] Weigh 0.0732 g of Na2CO3, 0.3975 g of Lu2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3 and 0.0004 g of Eu2O3 solids according to the molar mass ratio of the above chemical formula, mix them, and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, sinter it at 1250 °C for 6 h, and then grind it thoroughly to obtain a luminescent material with the molecular formula Na 0.995 Lu 0.9995 GeO4: 0.5% Bi 3+ , 0.05% Eu 3+ .

[0111] Example 20

[0112] This example provides a germanate-based long afterglow luminescent material. In this example, M is Na, Re is Lu, Ln is Pr, and x and y are 0.5% and 0.05% respectively. Therefore, the molecular formula of the luminescent material in this example is Na 0.995 Lu 0.9995 GeO4: 0.5% Bi 3+ , 0.05% Pr 3+ . And its preparation method is as follows:

[0113] Weigh 0.0732 g of Na2CO3, 0.3975 g of Lu2O3, 0.2133 g of GeO2, 0.0047 g of Bi2O3 and 0.0004 g of Pr6O according to the molar mass ratio of the above chemical formula. 11 Mix the solids and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, and calcine it at 1250 °C for 6 h and then grind it thoroughly to obtain a luminescent material with the chemical formula Na 0.995 Lu 0.9995 GeO4: 0.5% Bi 3+ , 0.05% Pr 3+ .

[0114] Comparative Example 1

[0115] A luminescent material for information storage, where M is Li and Re is Lu, and the chemical formula of the luminescent material is LiLuGeO4. And its preparation method is as follows:

[0116] Weigh 0.0739 g of Li2CO3, 0.3979 g of Lu2O3, and 0.2133 g of GeO2 solids according to the molar mass ratio of the above chemical formula, mix them, and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, and calcine it at 1250 °C for 6 h and then grind it thoroughly to obtain a luminescent material with the chemical formula LiLuGeO4.

[0117] Comparative Example 2

[0118] A luminescent material for information storage, where M is Na and Re is Lu, and the chemical formula of the luminescent material is NaLuGeO4. And its preparation method is as follows:

[0119] Weigh 0.1061 g of Na2CO3, 0.3979 g of Lu2O3, and 0.2133 g of GeO2 solids respectively according to the molar mass ratio of the above chemical formula, mix them, and then grind them using an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, and calcine it at 1250 °C for 6 h and then grind it into powder to obtain the NaLuGeO4 luminescent material.

[0120] Comparative Example 3

[0121] A luminescent material for information storage, where M is Li and Re is Y, and the chemical formula of the luminescent material is LiYGeO4. And its preparation method is as follows:

[0122] Weigh 0.0739 g of Li2CO3, 0.2258 g of Y2O3, and 0.2133 g of GeO2 solids according to the molar mass ratio of the above chemical formula, mix them, and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, sinter it at 1250 °C for 6 h, and then grind it thoroughly to obtain a luminescent material with the molecular formula LiYGeO4.

[0123] Comparative Example 4

[0124] A luminescent material for information storage, where M is Li and Re is Gd, and the molecular formula of the luminescent material is LiGdGeO4. And its preparation method is as follows:

[0125] Weigh 0.0739 g of Li2CO3, 0.3626 g of Gd2O3, and 0.2133 g of GeO2 solids according to the molar mass ratio of the above chemical formula, mix them, and grind them thoroughly in an agate mortar for 1 h to obtain a mixed powder; place the above mixed powder in a crucible, and in an air atmosphere, heat it to 1250 °C at a heating rate of 2 °C / min, sinter it at 1250 °C for 6 h, and then grind it thoroughly to obtain a luminescent material with the molecular formula LiGdGeO4.

[0126] Since the properties of the phosphors prepared in Examples 15 - 20 have similar examples in Examples 1 - 14, such as the properties of the phosphors prepared in Examples 15 - 18 are similar to those of the phosphor provided in Example 1, and the properties of the phosphors prepared in Examples 19 - 20 are similar to those of the phosphor prepared in Example 6, the following only takes the phosphors provided in Examples 1 - 14 as examples for effect description.

[0127] (I) Structure analysis

[0128] The standard X-ray diffraction (XRD) data of the phosphor in Example 1 (labeled as PDF#02 - 3479) is shown in Figure 1 . All the diffraction peaks ( Figure 1 ) of the luminescent materials provided in the synthesized Example 1 and Example 5 are consistent with the standard data of PDF#02 - 3479, indicating that Bi 3+ and Ln 3+ are doped into the matrix, and there is no obvious influence on the matrix structure. Figure 2 The crystal structure of Comparative Example 1 is given. LiLuGeO4 belongs to the orthorhombic system, the space group is Pnma(62), and there are obviously two six-coordinate sites of M + and Re 3+ ( Figure 2 ). As is well known, ionic radius and valence play a very important role in pair substitution. In this case, The ionic radius of CN=6 is closer to the doped element in the examples than the rare earth ionic radius CN=6). Therefore, in Examples 1-20, the doped element Bi 3+ occupies the M + lattice site. According to Hume-Rothery's rule, the ionic radius difference between Ln 3+ and Bi 3+ exceeds the threshold of 15%. Therefore, we prefer Bi 3+ ions to occupy the M + site. However, considering the valence state, the substitution of Bi 3+ for Lu 3+ cannot be excluded. Ln 3+ ions undoubtedly occupy the lattice site of the Re 3+ polyhedron.

[0129] The surface morphology and size of the particles will affect the afterglow performance of the luminescent material to a certain extent. The SEM and elemental mapping images of Example 1 are shown in Figure 3 . The elemental mapping images show that the elements Li, Lu, Ge, O, Bi, and Eu are evenly distributed in the sample.

[0130] (II) Fluorescence Performance Analysis

[0131] According to the trap engineering, we first introduced two typical Ln 3+ ions, including Eu 3+ that often acts as an electron trap, Yb 3+ and Tb 3+ that often acts as a hole trap, Pr 3+ into the M 1-x Re 1-y GeO4:xBi 3+ ,yLn 3+ luminescent material to adjust the trap distribution and fluorescence characteristics. Figure 4 shows the thermoluminescence curves of the phosphor samples in Examples 1-5. Among these phosphors, Example 1 exhibits the maximum thermoluminescence peak intensity, and the integral intensity of the curve (representing the trap density) is 2-20 times that of other samples, which implies that the phosphor in Example 1 has the maximum information storage capacity. In addition to the doping of Eu 3+ greatly increases the trap density and depth, the doping of Yb 3+ also increases the trap density. While the doping of Tb and Pr reduces the trap density. These experimental results imply that Bi 3+ may prefer to act as a hole trap and Eu 3+ / Yb 3+ acts as an electron trap to form deep electron-hole pair traps, increasing the trap density while deepening the traps.

[0132] To further regulate the trap density and depth, M 1-x Re 1-y GeO4:xBi 3+ ,yLn 3+ the alkali metal ion Li in it is replaced by Na + to obtain the phosphors of Examples 6 - 8. Figure 5 The thermoluminescence curves of the phosphors of Examples 6 - 8 are shown. Compared with the Bi 3+ single - doped sample, the doping of Eu 3+ greatly increases the trap density, but the trap depth seems to have a tendency to become shallower. While the doping of Tb 3+ completely quenches the afterglow luminescence of Bi 3+ .

[0133] Similarly, the Lu 1-x Re 1-y GeO4:xBi 3+ ,yLn 3+ ion in it is replaced by Y or Gd to obtain the phosphors of Examples 9 - 14. As 3+ shown, the doping of Eu Figure 6 in the germanate - series phosphors increases the trap density, while the doping of Tb 3+ does not have the same effect. Based on the thermoluminescence curve, the depth of the electron trap can be estimated according to the formula E = T 3+ / 500(K), where E and T max are the average trap depth and the peak temperature of the thermoluminescence curve respectively. The trap depth of all the samples in the examples is in the range of 0.5 - 1.1 eV. Previous studies have shown that a trap depth in the range of 0.5 - 0.7 eV is suitable for afterglow display applications, while a trap depth in the range of 0.7 - 1.0 eV is especially suitable for information storage. max

[0134] In Examples 1 and 6, the doping of Eu deepens the trap, making it more suitable for information storage and controllable - excitation fluorescence. To further describe the fluorescence properties of these phosphors, taking the Li 0.99 Lu 0.999 GeO4:1.0%Bi 3+ ,0.1%Eu 3+ phosphor in Example 1 as an example, Figure 7 the photoluminescence emission spectra, excitation spectra, afterglow emission spectra and afterglow decay curves of Examples 1 - 5 are shown. As Figure 7 shown in A, under the excitation of 312 nm ultraviolet light, all samples have a similar blue - light emission band in the range of 330 - 500 nm, which is attributed to the 3+ 3 P 1，0 → 1 S0 transition of Bi​​3+ In addition to the blue light emission, the Eu in Example 1 3+ of 5 D0→ 7 F2, and the Tb in Example 2 3+ of 5 D4→ 7 F0 and other characteristic transitions of Ln 3+ can also be observed.

[0135] Figure 7 In B, the monitored PLE spectrum obtained at 370 nm shows that large doublets generated by the S0→P transition of Bi split by the Jahn-Teller effect are observed on the broadband background at 312 nm and 356 nm. A weak absorption peak is accompanied at the left shoulder (236 nm), which is attributed to the transition from the valence band (VB) to the conduction band (CB) of the matrix. 3+ of 1 S0→ 3 P 1,0 transition. A weak absorption peak is accompanied at the left shoulder (236 nm), which is attributed to the transition from the valence band (VB) to the conduction band (CB) of the matrix. Figure 7 C shows the afterglow phenomenon of the phosphors in Examples 1-5 after being charged with 236 nm ultraviolet light. All the afterglow spectra are similar to their PL spectra, mainly dominated by the blue light emission band of Bi, and accompanied by weak typical emissions of Ln. These spectral results indicate that the afterglow and photoluminescence originate from the same luminescence center. Among them, the phosphors in Examples 4 and 5 have better room temperature afterglow performance, while Example 1 has almost no room temperature afterglow, which is consistent with its deep trap characteristics. 3+ of 3+ These spectral results indicate that the afterglow and photoluminescence originate from the same luminescence center. Among them, the phosphors in Examples 4 and 5 have better room temperature afterglow performance, while Example 1 has almost no room temperature afterglow, which is consistent with its deep trap characteristics. Figure 7 D shows that in addition to Example 2 and Example 1, Examples 3-5 all show shorter afterglow durations.

[0136] Figure 8 shows the variable temperature afterglow characteristics of the phosphor in Example 1. We can clearly see that the afterglow intensity increases with the temperature rising from room temperature to 110 °C, the excitation fluorescence intensity reaches the peak, and then decreases slowly with the temperature continuing to increase, indicating that the afterglow intensity depends on the temperature. Figure 9 shows the changes in the blue excitation fluorescence intensity and red excitation fluorescence intensity of the phosphor in Example 1 with the increase of the charging temperature. Obviously, the blue excitation fluorescence from Bi increases with the increase of temperature, reaches the best charging state in the range of 50-80 °C, forming an abnormal thermal capacity increase phenomenon. The red excitation decreases slightly with the increase of temperature as the trap filling deepens. Particularly interestingly, after the phosphor in Example 1 is charged, the information seems to condense at room temperature. After 5 days, the thermoluminescence curve ( 3+ ) is measured, and the trap filling capacity hardly dissipates at room temperature, indicating the non-volatile information retention characteristic. Figure 10 ) is measured, and the trap filling capacity hardly dissipates at room temperature, indicating the non-volatile information retention characteristic.

[0137] The thermally variable thermoluminescence curves of Examples 2 to 4 are shown in Figure 11 . Among them, Example 2 ( Figure 11 A) and Example 4 ( Figure 11 B) both show a certain high-temperature information storage capacity, while Example 3 ( Figure 11 C) only exhibits room-temperature information writing ability.

[0138] Figure 12 The photo-stimulated fluorescence characteristics of the phosphors of Examples 1 to 4 were confirmed. Under near-infrared laser excitation, all samples exhibited good photo-stimulated fluorescence characteristics, indicating that the written information can be read out by photo-stimulation. Figure 13 The photoluminescence excitation spectrum and afterglow excitation spectrum of the phosphor of Example 1 are shown. The maximum excitation peaks of the two do not overlap. The maximum position of the afterglow excitation spectrum is at the valence band to conduction band transition peak. The photoluminescence excitation peak is mainly due to the internal energy level electron transition of the doped ions. Therefore, we can control and suppress the energy consumed by photoluminescence by reasonably selecting the charging wavelength. Figure 14 Shows the high-resolution photoelectron spectrum of Bi in Examples 1 and 5 3+ . Comparing Figure 14 A and B, it is not difficult to find that after Eu 3+ doping, it induces a change in the valence of Bi 3+ , which may lead to an increase in the trap density and distribution.

[0139] Considering the above experimental results, we propose a possible schematic diagram of the photoluminescence, afterglow, photo / thermal-stimulated fluorescence, and photo-stimulated afterglow fluorescence of Examples 1 to 14 mediated by the deep trap structure of hole-electron pairs, and it is shown in Figure 15 . When the sample is irradiated with ultraviolet light, electrons are excited from the ground state to the conduction band (CB), leaving holes in the ground state. Holes and a part of the electrons are trapped by hole / electron traps through VB / CB, and the other part of the electrons are released in the form of blue light, and then return to the ground state after rapid energy transfer and non-radiative relaxation to the red fluorescence energy level, generating the photoluminescence of Bi 3+ and the typical fluorescence emission of Ln 3+ . The released electrons / holes combine with luminescence centers such as Bi 3+ / Yb 3+ / Eu 3+ / Tb 3+ under external stimulation, generating afterglow, thermally stimulated / photo-stimulated fluorescence, and most of the electrons in the traps are released from the CB to the blue light state. The 980 nm laser accelerates energy transfer and non-radiative relaxation or multi-phonon relaxation, presenting bright red stimulated fluorescence. During the luminescence process of Bi 3+ , the energy transfer from Bi 3+ to Ln 3+ is effective. Under photo-thermal induction, charge carriers are carried by Bi3+ and Ln 3+ are trapped and released by the traps, along with Bi 3+ and Ln 3+ accompanied by changes in the ionic valence states of Bi and Ln. For example, under 236 nm ultraviolet light irradiation, the conduction band electrons generated by the photoionization process of the charge transfer band can be trapped by Eu 3+ to form Eu 3+ , while the holes leaving Bi 2+ can be trapped by Bi 3+ to form Bi 2+ . Under photo / thermal excitation, electrons are gradually released from Eu 3+ to the conduction band, and then recombine with the Bi 2+ + holes, finally generating Bi 3+ P0- 3+3 S0 emission with a peak located at 408 nm. 1

[0140] (III) Applications in optical information storage anti-counterfeiting

[0141] Considering the excellent performance of the phosphors in Examples 1 to 4, dynamic luminescent patterns for multi-dimensional information storage and encryption were designed, as Figure 16 shown.

[0142] Figure 16 Figure a is the structural diagram of the fluorescent "Butterfly in Love with Flowers" pattern, and each part is composed of different phosphors in Examples 1 to 4. Under selective excitation from ultraviolet to visible light, the blue emission of Bi 3+ and the characteristic emission of Ln 3+ make each phosphor present colorful changes, as Figure 16 shown in Figure b. After charging with 254 nm ultraviolet light, the colored afterglow pattern of the Butterfly in Love with Flowers is visible to the naked eye. As time prolongs, each part gradually disappears. Until 20 minutes later, the green leaves completely disappear ( Figure 16 Figure c). When the afterglow pattern disappears, using an 808 / 980 nm laser diode or thermal-assisted illumination pattern, the latent pattern can be restored and extracted again ( Figure 16 Figures d - e).

[0143] More interestingly, by consciously controlling the temperature of ultraviolet pre-irradiation, multi-dimensional information storage can be recorded on a single-layer luminescent material film. For example, Figure 16 the rose in Figure f is written through a hollow rose mask under 254 nm ultraviolet light irradiation at 423 K. Subsequently, the ultraviolet light ground leaf pattern is stored at 353 K. Finally, the butterfly is written at room temperature under 254 nm light irradiation using an ultraviolet light mask pattern. Therefore, three different patterns are stored in traps at different depths. As Figure 16 ​As shown in Fig. f, the pre-stored 'rose' is only stored in the deep trap, the 'leaf' is stored in the medium-depth trap, while the 'butterfly' is stored in traps of various depths. Different patterns can be visualized through temperature management. For example, by reading the above information through the temperature sequence of RT, 353, and 423 K, the dynamic pattern information can be read out in the spatial domain ( Figure 16 f). As Figure 16 shown in Fig. f, the recorded 'butterfly' is read out separately and clearly at RT. When the temperature is raised to 353 K, the 'butterfly' and 'leaf' can be clearly identified. Further raising the temperature to 423 K, the entire pattern including the 'butterfly', 'leaf', and 'rose' can be observed. In this way, multi-dimensional information can be stored and read out, increasing the information storage capacity.

[0144] Figure 17 is the 'flower' image stored as a fluorescent medium material based on Example 6 ( Figure 17 a). Under the irradiation of 236 nm ultraviolet light, the mixture of the blue emission of Bi 3+ and the red emission of Eu 3+ makes the 'flower' appear purplish-red, and pure blue and red 'flower' photos can be obtained with the assistance of a filter ( Figure 17 b). After stopping the 236 nm ultraviolet light irradiation, the flower emits a purplish-red afterglow, which can last for more than 30 minutes ( Figure 17 c). As time further elapses, the flower disappears first. When the afterglow pattern disappears, the latent pattern can be restored and extracted again by illuminating or heating the pattern with 808 / 980 nm laser ( Figure 17 d - e). Similarly, by controlling the temperature of the ultraviolet pre-irradiation, multi-dimensional information storage can be recorded on a single-layer luminescent material film. For example, Figure 17 the large flower pattern in Fig. f is written by irradiating with 236 nm ultraviolet light at 423 K through a hollow large flower photomask. Subsequently, by covering the printed entire pattern with a hollow small flower photomask, the small flower pattern is stored at 353 K. Finally, the leaf pattern is written at room temperature under the irradiation of 236 nm light using the pattern of the hollow leaf photomask. Therefore, three different patterns are stored in traps of different depths. As Figure 17 shown in Fig. f, the pre-stored 'leaf' is stored in the shallow trap, the'small flower' is stored in the medium-depth trap, while the 'large flower' is only stored in the local deep trap, and visualization can be achieved through temperature management. Then, by reading the above information through the temperature sequence of RT, 353, and 423 K, the dynamic pattern information can be read out in the spatial domain ( Figure 17 f). As Figure 17As shown in Figure 5, the recorded leaf shape is read out separately and clearly in RT. When the temperature is raised to 353K, the leaves and florets can be clearly identified. Further raising the temperature to 423K, the entire pattern including 'leaves', 'florets' and 'large flowers' can be observed. In this way, multi-dimensional information can be stored and read out, increasing the storage capacity of information.

[0145] Aiming at the needs of potential multifunctional applications, the present invention has successfully designed a variety of multi-color emission long afterglow luminescent materials based on luminescence mechanism, defect engineering, band gap engineering and site occupancy rules. Experimental results confirm that Bi 3+ , Ln 3+ The co-doped germanate-based luminescent materials have excellent multicolor and multimode fluorescence properties that can meet specific requirements. The trapping properties have been extensively studied through excitation temperature-dependent thermoluminescence analysis experiments, the fluorescence mechanism has been elucidated, and the Ln 3+ Co-doping plays a key role. Among these luminescent materials, MReGeO4:Bi 3+ ,Ln 3+ This work not only verifies the utility of deep trap afterglow in potential multifunctional applications, but also establishes a design concept applicable to new afterglow materials.

[0146] Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. A germanate-based long afterglow luminescent material, characterized in that, The luminescent material uses MReGeO4 as the matrix and introduces doping ions Bi and Ln 3+ to obtain, and the chemical formula of the luminescent material is M 1-x Re 1-y GeO4:xBi 3+ ,yLn 3+ ; Among them, M is Li or Na, Re is Y, Lu or Gd, and Ln is one of Eu, Tb, Pr or Yb; 0 < x ≤ 0.010, 0 ≤ y ≤ 0.

001.

2. A method for preparing the luminescent material according to claim 1, characterized in that, It includes the following steps: According to the stoichiometric ratio of the luminescent material with the chemical formula M 1-x Re 1-y GeO4:xBi 3+ ,yLn 3+ , weigh the M source, Re source, Ge source, O source, Bi source and Ln source, mix them, and calcine them to obtain the luminescent material.

3. The preparation method according to claim 2, characterized in that The M source, Re source, Ge source, Bi source and Ln source are all oxygen-containing compounds containing the corresponding elements; The O source is jointly provided by the oxygen-containing compounds.

4. The preparation method according to claim 3, wherein, The oxygen-containing compound is any one or more of oxides, carbonates or nitrates.

5. The preparation method according to claim 2, characterized in that, The calcination is carried out in an air atmosphere, heated to 1000 - 1300 °C at a heating rate of 2 - 4 °C / min, and calcined for 4 - 8 h.

6. The preparation method according to claim 2, wherein During mixing, the preparation raw materials are ground for 0.5 - 1 h.

7. Use of the luminescent material according to claim 1 as a material for information storage or encryption.

8. The use according to claim 7, characterized in that, The luminescent material is used for multi-dimensional visual information storage and encryption.

9. The use according to claim 7, characterized in that, The information storage or encryption is assisted by ultraviolet light irradiation.

10. The use according to claim 7, characterized in that, The information storage or encryption is achieved by controlling the luminescent material to receive light or heat again at a specific time frame after ultraviolet pre-irradiation.

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