A kind of Ce 3+ activated blue long afterglow material and its preparation method

Abstract

The present invention relates to the technical field of long afterglow phosphors, and specifically to a Ce 3+ -activated blue long afterglow material and a preparation method thereof. The chemical composition formula of the material is: Rb 3w Gd (1‑y‑x) Sc y Si2O7:Ce x , where 0.95 ≤ w ≤ 0.98, 0.005 ≤ x ≤ 0.05, and 0.001 ≤ y ≤ 0.002. The material prepared by the present invention can exhibit a photochromic effect of changing from white to cyan-gray after absorbing ultraviolet light; after turning off the light source, the material emits blue long afterglow, and the afterglow decay time can reach 30 h; when the afterglow disappears, after being excited again by 980 nm near-infrared light, regenerative up-conversion long afterglow luminescence can be achieved, and the afterglow decay time is about 4 h. The material of the present invention is expected to realize multifunctional applications such as information storage, fluorescence anti-counterfeiting, and bio-optical imaging.

Description

Technical Field

[0001] The present invention relates to the technical field of luminescent materials, and particularly to a Ce 3+ -activated blue long afterglow material and a preparation method thereof. Background Technique

[0002] Since long afterglow luminescent materials can still emit light continuously and stably after the excitation of external light sources stops, they are considered as an energy-saving and green material, and are widely used in fields such as night lighting, safety indication, night vision surveillance, fluorescence anti-counterfeiting, etc. They even have great application prospects in high-tech fields such as bio-optical imaging, solar energy utilization, photocatalysis, high-energy ray detection, and optical information storage.

[0003] The first generation of artificial long afterglow luminescent materials came out in the nineteenth century, mainly metal sulfide systems, and the typical representatives are activated ion-doped ZnS and CaS. The advantages of this system are diverse luminescent colors, but there are problems such as poor chemical stability, short afterglow time (about 0.5 - 2h), and low initial afterglow brightness. In the 1990s, people conducted a large number of studies on rare earth ion-doped aluminate long afterglow materials with good luminescent properties and afterglow characteristics (such as SrAl2O4:Eu 2+ ,Dy 3+ , CaAl2O4:Eu 2+ ,Nd 3+ , etc.). This system belongs to the second generation of long afterglow materials, and is significantly superior to sulfide system products in terms of luminescent brightness, afterglow time, and chemical stability, etc., and has been widely used. However, such materials face problems such as insufficiently rich luminescent colors, poor water resistance, and high production costs. Due to the above-mentioned disadvantages of the aluminate system being difficult to improve, researchers began to develop and explore long afterglow luminescent materials based on silicate matrices, and successfully developed Sr2MgSi2O7:Eu 2+ ,Dy 3+ , Ca2MgSi2O7:Eu 2+ ,Dy 3+ , etc. silicate long afterglow materials. At present, although the water resistance of silicate long afterglow materials is better than that of aluminate long afterglow materials, there are still problems such as single afterglow color and insufficiently long afterglow time. Generally speaking, the current research mainly focuses on developing materials that can achieve long-term stable long afterglow luminescence in the blue, green, red, or near-infrared light regions after energy storage by ultraviolet light excitation.

[0004] However, with the expansion of the application of long afterglow materials in high-tech fields, it is urgent to develop long afterglow materials with multi-mode optical properties. For example, in the field of intelligent fluorescent anti-counterfeiting, the coupling and integration of multiple optical modes such as long afterglow luminescence, photochromism, and photoluminescence can help improve the anti-counterfeiting level and expand the anti-counterfeiting capacity. Another example is in the field of bio-optical imaging, where there is an urgent need to develop materials that can achieve near-infrared excitation and then regenerate long afterglow luminescence. This is because conventional long afterglow luminescent materials are mainly effective after ultraviolet light excitation. Since ultraviolet light has a weak penetration ability into biological tissues and can damage normal cells, when such long afterglow materials are used as probes and enter the body, once the afterglow disappears, they cannot be excited and recharged anymore, resulting in an observation window that is usually less than a few hours and difficult to meet the need to track cells in the body for several days or even weeks. To solve the above problems, new materials that can be effectively recharged under 980 nm near-infrared light excitation and then achieve long afterglow luminescence again are needed. In summary, developing a single matrix luminescent material with characteristics such as ultra-long afterglow luminescence, near-infrared excitation and regeneration of afterglow luminescence, and photochromism can meet many application requirements and has important research significance and application value. Summary of the Invention

[0005] Aiming at the deficiencies of the above-mentioned existing technologies, an object of the present invention is to provide a silicate long afterglow luminescent material that can be excited by ultraviolet light to obtain blue long afterglow luminescence and photochromic properties, and at the same time can achieve near-infrared excitation and regeneration of long afterglow luminescence. Another object of the invention is to provide a preparation method of the above material.

[0006] The blue long afterglow material proposed by the present invention is a Ce 3+ -activated blue long afterglow material, which is a silicate compound containing Ce 3+ , Rb + , Gd 3+ , Sc 3+ , Si 4+ cations, and its chemical composition expression is Rb 3w Gd (1-y-x) Sc y Si2O7:Ce x , where 0.95 ≤ w ≤ 0.98, 0.005 ≤ x ≤ 0.05, 0.001 ≤ y ≤ 0.002.

[0007] The preparation method of the long afterglow luminescent material of the present invention is as follows:

[0008] (1) Mix and stir the solutions of RbNO3, Gd(NO3)3, Sc(NO3)3 and Ce(NO3)3, usually stir for 20 min; gradually drop concentrated nitric acid into the mixed solution to adjust the pH value of the solution to 1 - 3, and continue to stir for 10 - 15 min until it becomes a transparent solution;

[0009] (2) Mix tetraethyl orthosilicate and absolute ethanol and stir, usually for 30 min; dropwise add the obtained mixed solution into the nitrate solution prepared in the above step (1) to make the Ce 3+ , Rb + , Gd 3+ , Sc 3+ , Si 4+ ions meet the designed stoichiometric ratio; then, add a certain amount of citric acid into the above mixed solution and stir well;

[0010] (3) Place the mixed solution obtained in the above step (2) in a constant-temperature oven, keep it at 80 - 90 °C for 8 - 14 h to obtain a wet gel; then dry the wet gel at 100 - 120 °C for 12 - 16 h to obtain a dry gel;

[0011] (4) After grinding the dry gel, keep it at 350 - 500 °C for 2 - 3 h in an air atmosphere; after the obtained precursor is cooled to room temperature, take it out and grind it, and then calcine it at 700 - 900 °C for 3 - 5 h (in an air atmosphere); after natural cooling to room temperature, fully grind the obtained white powder to obtain the final product.

[0012] In the above technical solution, further, the concentration of Gd(NO3)3 in the mixed solution in step (1) is 0.2 - 0.3 mol / L, and the volume ratio of tetraethyl orthosilicate to absolute ethanol in step (2) is 1:3 - 1:6.

[0013] Further, the molar ratio of citric acid to metal ions in step (2) is 1:1 - 6:1.

[0014] Further, in the above step (4), the heating rate during the heat treatment process is 5 - 10 °C / min.

[0015] After the material of the present invention is excited by ultraviolet light (especially ultraviolet light with a wavelength of 314 nm), the color of the material changes from white to cyan-gray and returns to white again after about 30 - 60 min, that is, it exhibits photochromic properties; at excitation wavelengths of 290 - 340 nm and 340 - 390 nm (corresponding to the 4f→5d1 and 4f→5d2 transitions of Ce 3+ ions), the material can emit blue light with a wavelength located at 400 - 600 nm and a peak position at 455 - 458 nm (corresponding to the 5d1→ 3+ of Ce 2 F 5 / 2 / 2 F 7 / 2Upon excitation, it exhibits photoluminescence properties. Additionally, after being excited by ultraviolet light for 5 - 10 minutes and then the excitation is stopped, the material shows blue long - persistent luminescence with a persistent time of up to 30 hours. When the persistent luminescence disappears and then it is excited by 980 nm near - infrared light, the material can re - emit blue up - conversion luminescence, and after the excitation is stopped, the blue persistent luminescence can last for 4 hours. That is, the material has the properties of long - persistent luminescence and near - infrared - excited re - growth of persistent luminescence.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] (1) The Rb 3w Gd (1-y-x) Sc y Si2O7:Ce x material provided by the present invention is fired in an air environment. Among many rare - earth ions, Ce ions are one of the ions with the smallest optical electronegativity, and its standard reduction potential E value (Ce 4+ →Ce 3+ ) is about 2.14. Therefore, under the preparation conditions of the present invention, the doped Ce 3+ ions are easily partially oxidized to Ce 4+ ions. That is, in Rb 3w Gd (1-y-x) Sc y Si2O7, Ce ions exist in the form of co - existence of trivalent Ce 3+ and tetravalent Ce 4+ . Among them, Ce 3+ ions are the luminescence centers. Under ultraviolet light excitation, their 5d1→ 2 F 5 / 2 / 2 F 7 / 2 transition can generate blue - light emission. Although Ce 4+ ions are optically inert and do not undergo radiative luminescence, after they occupy the lattice sites of trivalent Gd 3+ ions, due to the imbalance of their valence states, it will lead to and V″ O and other point defects are generated, realizing the construction of corresponding trap energy levels. At the same time, by making the content of Rb + ions in the matrix lower than the standard stoichiometric ratio, V′ Rb and and other defects can be formed, thus forming additional trap energy levels in the band gap.

[0018] Under ultraviolet light excitation, the trap levels in the material can capture electrons to store energy; after the light source excitation stops, the defect levels can release some of the captured electrons under the perturbation of external energy. After the electrons return to the luminescence center, radiative transition generates blue long afterglow luminescence. In addition, due to the different depths of the trap levels of different types of defects in this material, under 980 nm near-infrared light excitation, electrons can migrate from deep trap levels to shallow trap levels and finally return to the luminescence center to achieve renewable long afterglow luminescence. On the other hand, under ultraviolet light irradiation, the valence electrons in the matrix are excited to the conduction band and then relax to the trap levels, which can lead to the generation of color centers, making the material exhibit photochromic properties with the color changing from white to cyan-gray. Therefore, through the selection of reasonable component ratios and preparation conditions, this material has successfully achieved the coupling of multimodal optical properties such as photoluminescence, photochromism, long afterglow luminescence, and near-infrared excitation regenerated long afterglow luminescence.

[0019] (2) For the long afterglow material provided by the present invention, after the ultraviolet light excitation stops, the blue long afterglow time can reach about 30 h, which is longer than that of most silicate long afterglow luminescent materials; when re-excited with 980 nm near-infrared light, the regenerated upconversion afterglow time can also reach about 4 h, showing certain application potential in the fields of fluorescent anti-counterfeiting marks, biological fluorescence imaging, information storage, and night light display. Description of the Drawings

[0020] Figure 1 Rb prepared for Example 1 2.85 Gd 0.948 Sc 0.002 Si2O7:Ce 0.05 X-ray diffraction pattern of the long afterglow material;

[0021] Figure 2 Rb prepared for Example 1 2.85 Gd 0.948 Sc 0.002 Si2O7:Ce 0.05 Ce ion X-ray photoelectron spectroscopy pattern of the long afterglow material;

[0022] Figure 3 Rb prepared for Example 1 2.85 Gd 0.948 Sc 0.002 Si2O7:Ce 0.05 Excitation spectrum of the long afterglow material;

[0023] Figure 4 Rb prepared for Example 1 2.85 Gd 0.948 Sc 0.002 Si2O7:Ce 0.05Fluorescence spectrum of the long-afterglow material under 314 nm ultraviolet light excitation;

[0024] Figure 5 Rb prepared for Example 1 2.85 Gd 0.948 Sc 0.002 Si2O7:Ce 0.05 Photos of the long-afterglow material before ultraviolet light excitation and after 5 minutes of excitation; For easy observation, the powder is pressed in the sample cell;

[0025] Figure 6 Rb prepared for Example 1 2.85 Gd 0.948 Sc 0.002 Si2O7:Ce 0.05 Afterglow decay curve of the long-afterglow material after 5 minutes of ultraviolet light excitation;

[0026] Figure 7 Rb prepared for Example 1 2.85 Gd 0.948 Sc 0.002 Si2O7:Ce 0.05 Afterglow decay curve of the regenerated long-afterglow material after 5 minutes of 980 nm near-infrared light excitation after the afterglow disappears; The inset is the upconversion luminescence spectrum under 980 nm excitation;

[0027] Figure 8 Rb3Gd prepared for Comparative Example 1 0.948 Sc 0.002 Si2O7:Ce 0.05 Afterglow decay curve of the material after 5 minutes of ultraviolet light excitation. Detailed implementation mode

[0028] The present invention will be further described below by way of examples.

[0029] Example 1

[0030] Weigh 28.5 mL, 9.48 mL, 0.02 mL, and 0.5 mL of aqueous solutions of RbNO3, Gd(NO3)3, Sc(NO3)3, and Ce(NO3)3 with a concentration of 0.2 mol / L each and place them in a beaker for mixing. Continuously stir the mixture on a magnetic stirrer for 20 min. Then, while maintaining the stirring state, slowly drip concentrated nitric acid into the mixed solution to adjust the pH value to 1, and continue stirring for 15 min to form a transparent solution for standby. After mixing 0.8968 mL of tetraethyl orthosilicate with 2.6904 mL of absolute ethanol and stirring for 30 min, slowly drip this solution into the prepared nitrate solution. After stirring evenly, add 2.2489 g of citric acid and fully stir at 50 °C for 30 min to completely dissolve the citric acid. Subsequently, place the mixed solution in a constant-temperature oven, keep it at 80 °C for 14 h to obtain a wet gel, and then raise the temperature to 100 °C and dry it for 16 h to form a dry gel. Place the obtained dry gel in a corundum crucible, put it into a muffle furnace, and under an air atmosphere, keep it at 350 °C for 3 h to obtain a precursor powder. After the precursor powder is cooled to room temperature, take it out, grind it, put it into the muffle furnace, and calcine it at 900 °C for 3 h. After cooling to room temperature with the furnace, take it out, grind it to obtain the final product Rb 2.85 Gd 0.948 Sc 0.002 Si2O7:Ce 0.05 .

[0031] Figure 1 Figure 12 is the X-ray diffraction pattern of the above product. It can be seen that its pattern is relatively close to that of Gd2Si2O7 pyrosilicate, and the diffraction peaks are sharp, indicating that the crystallinity of the sample is high. The valence state of Ce ions was detected by X-ray photoelectron spectroscopy. As shown in Figure 13 Figure 2 , it can be seen that the doped Ce element remains in the state of coexistence of Ce 3+ and Ce 4+ . The excitation and emission spectra of this product are shown in Figures 15 Figure 3 and 4 . Under the excitation of 314 nm, blue light emission with wavelengths ranging from 400 nm to 575 nm (centered at 458 nm) is emitted. After being excited by 314 nm light for 5 minutes, the color of the powder changes from white to cyan-gray (Figure 17 Figure 5 ); when the excitation light source is removed, bright blue afterglow can be observed by the naked eye. From the afterglow decay curve, it can be seen that the afterglow time of this product can reach 30 h (Figure 18 Figure 6 ). When the afterglow disappears, under the excitation of 980 nm light, this product can emit upconverted blue light (Figure 19 Figure 7 , inset); after continuous excitation for 5 minutes and then turning off the 980 nm laser light source, the regenerated blue light afterglow can last for about 4 h (Figure 20 Figure 7 ).

[0032] Comparative Example 1

[0033] Weigh 30 mL, 9.48 mL, 0.02 mL, and 0.5 mL of aqueous solutions of RbNO3, Gd(NO3)3, Sc(NO3)3, and Ce(NO3)3 with a concentration of 0.2 mol / L each, place them in a beaker and mix. Continuously stir on a magnetic stirrer for 20 min. Then, while maintaining the stirring state, slowly add concentrated nitric acid drop by drop to the mixed solution to adjust the pH value to 1, and continue stirring for 15 min to form a transparent solution for standby. After mixing 0.8968 mL of tetraethyl orthosilicate and 2.6904 mL of absolute ethanol and stirring for 30 min, slowly add this solution drop by drop to the prepared nitrate solution. After stirring evenly, add 2.2489 g of citric acid and stir thoroughly at 50 °C for 30 min to completely dissolve the citric acid. Subsequently, place the mixed solution in a constant-temperature oven, keep it at 80 °C for 14 h to obtain a wet gel, and then raise the temperature to 100 °C and dry it for 16 h to form a dry gel. Place the obtained dry gel in a corundum crucible, put it into a pit furnace, and keep it at 350 °C for 3 h to obtain a precursor powder. After the precursor powder is cooled to room temperature, take it out, grind it, put it into a tube furnace, and calcine it at 900 °C for 3 h under the protection of a reducing gas of 10% H2 + 90% N2. After cooling to room temperature with the furnace, take it out, grind it to obtain the final product Rb3Gd 0.948 Sc 0.002 Si2O7:Ce 0.05 .

[0034] When excited at 314 nm, this product can emit bright blue light. However, after being excited by 314 nm light for 5 minutes, when the excitation light source is removed, the luminescence decays rapidly and no obvious afterglow phenomenon is presented ( Figure 8 ). Through comparison, it is not difficult to find that making the content of Rb + lower than the standard stoichiometric ratio and calcining in an air environment contribute to generating appropriate trap energy levels in the matrix and enabling the material to exhibit an afterglow phenomenon.

[0035] Example 2

[0036] Weigh 29.1 mL, 9.735 mL, 0.015 mL, and 0.25 mL of aqueous solutions of RbNO3, Gd(NO3)3, Sc(NO3)3, and Ce(NO3)3 with a concentration of 0.2 mol / L each and place them in a beaker for mixing. Continuously stir the mixture on a magnetic stirrer for 20 min. Then, while maintaining the stirring state, slowly drop concentrated nitric acid into the mixed solution to adjust the pH value to 2, and continue stirring for 12 min to form a transparent solution for standby. After mixing 0.8968 mL of tetraethyl orthosilicate and 4.0356 mL of absolute ethanol and stirring for 30 min, slowly drop this solution into the prepared nitrate solution. After stirring evenly, add 6.813 g of citric acid and fully stir at 50 °C for 45 min until the citric acid is completely dissolved. Subsequently, place the mixed solution in a constant-temperature oven, keep it at 90 °C for 8 h to obtain a wet gel, and then raise the temperature to 110 °C and dry it for 14 h to form a dry gel. Place the obtained dry gel in a corundum crucible, put it into a muffle furnace, and keep it at 400 °C for 2.5 h in an air atmosphere. After the obtained precursor powder is cooled to room temperature, take it out, grind it, put it into a muffle furnace, and calcine it at 700 °C for 5 h. After cooling to room temperature with the furnace and taking it out, grind it to obtain the final product Rb 2.91 Gd 0.9735 Sc 0.0015 Si2O7:Ce 0.025 。

[0037] Detected by X-ray diffraction, the X-ray diffraction pattern of the obtained product is relatively close to that of Gd2Si2O7 pyrosilicate, and the crystallinity of the sample is high. It is confirmed by X-ray photoelectron spectroscopy that the doped Ce ions in the product remain in the state of Ce 3+ and Ce 4+ coexisting state. Under 314 nm excitation, the product emits blue light with wavelengths ranging from 400 nm to 575 nm (centered at 456 nm). After being excited by 314 nm light for 5 minutes, the color of the powder changes from white to bluish-gray; when the excitation light source is removed, a bright blue afterglow can be observed by the human eye; the afterglow decay curve shows that the afterglow time of this product can reach 30 h. When the afterglow disappears, re-excite the powder with 980 nm light for 5 minutes, and then turn off the 980 nm excitation light source, and its regenerated blue afterglow can last for about 4 h.

[0038] Example 3

[0039] Weigh 29.4 mL, 9.94 mL, 0.01 mL, and 0.05 mL of aqueous solutions of RbNO3, Gd(NO3)3, Sc(NO3)3, and Ce(NO3)3 with a concentration of 0.3 mol / L each and place them in a beaker for mixing. Continuously stir the mixture on a magnetic stirrer for 20 min. Then, while maintaining the stirring state, slowly add concentrated nitric acid dropwise to the mixed solution to adjust the pH value to 3, and continue stirring for 10 min to form a transparent solution for standby. After mixing 0.8968 mL of tetraethyl orthosilicate and 5.3808 mL of absolute ethanol and stirring for 30 min, drop this mixed solution into the prepared nitrate solution. After stirring evenly, add 13.696 g of citric acid and stir thoroughly at 50 °C for 60 min until the citric acid is completely dissolved. Subsequently, place the mixed solution in a constant-temperature oven, keep it at 85 °C for 11 h to obtain a wet gel, and then raise the temperature to 120 °C and dry it for 12 h to form a dry gel. Place the obtained dry gel in a corundum crucible, put it into a muffle furnace, and keep it at 500 °C for 2 h in an air atmosphere. After the powder is cooled to room temperature, take it out and grind it, then put it into the muffle furnace and calcine it at 800 °C for 4 h. After cooling to room temperature with the furnace, take it out and grind it to obtain the final product Rb 2.94 Gd 0.994 Sc 0.001 Si2O7:Ce 0.005 。

[0040] Detected by X-ray diffraction, the X-ray diffraction pattern of the obtained product is relatively close to that of Gd2Si2O7 pyrosilicate, and the crystallinity of the sample is high. It is confirmed by X-ray photoelectron spectroscopy that the doped Ce ions in the product are Ce 3+ and Ce 4+ coexist. Under 314 nm excitation, blue light emission with wavelengths ranging from 400 nm to 575 nm (centered at 455 nm) is emitted. After being excited by 314 nm light for 5 minutes, the color of the powder changes from white to cyan-gray; when the excitation light source is removed, bright blue afterglow can be observed by the naked eye. The afterglow decay curve test shows that the afterglow time of this product can reach 30 h. When the afterglow disappears, re-excite the material with 980 nm light for 5 minutes, and then turn off the 980 nm excitation light source, and its regenerated blue afterglow can last for about 4 h.

Claims

1. A Ce 3+ activated blue long afterglow material, characterized in that: The material is a silicate compound containing Ce 3+ , Rb + , Gd 3+ , Sc 3+ , Si 4+ cations, and its chemical composition expression is: Rb 3w Gd (1-y-x) Sc y Si2O7:Ce x , where 0.95 ≤ w ≤ 0.98, 0.005 ≤ x ≤ 0.05, 0.001 ≤ y ≤ 0.

002.

2. A method for preparing a Ce 3+ activated blue long afterglow material as claimed in claim 1, characterized in that It includes the following steps: (1) Mix and stir the solutions of RbNO3, Gd(NO3)3, Sc(NO3)3 and Ce(NO3)3, drop concentrated nitric acid into the mixed solution to adjust the pH value of the solution to 1 - 3, and continuously stir until it becomes a transparent solution; (2) Mixing ethyl orthosilicate and anhydrous ethanol and stirring; dripping the obtained mixed solution dropwise into the solution obtained in step (1) to make Ce 3+ , Rb + 、Gd 3+ Sc 3+ 、Si 4+ ions satisfy the designed stoichiometric ratio; then citric acid is added to the resulting mixture and stirred thoroughly; (3) Place the mixed solution obtained in the above step (2) in a constant temperature oven, keep it at 80 - 90 °C for 8 - 14 h to obtain a gel; then dry the gel at 100 - 120 °C for 12 - 16 h to obtain a dry gel; (4) After grinding the dry gel obtained in the above step (3), keep it at 350 - 500 °C for 2 - 3 h in an air atmosphere. After cooling to room temperature, grind the powder, and then calcine it at 700 - 900 °C for 3 - 5 h; finally, after natural cooling to room temperature, grind the obtained white powder to obtain a blue long - persistent phosphor material.

3. A preparation method of a Ce 3+ activated blue long afterglow material, characterized in that: In step (1), the concentration of Gd(NO3)3 in the mixed solution is 0.2 - 0.3 mol / L, and in step (2), the volume ratio of tetraethyl orthosilicate to absolute ethanol is 1:3 - 1:

6.

4. The preparation method of an activated blue light long afterglow material as claimed in claim 2, characterized in that: 3+ In step (2), the molar ratio of citric acid to metal ions is 1:1 - 6:

1.

5. The preparation method of a Ce 3+ activated blue long afterglow material according to claim 2, characterized in that: In the heat treatment process in step (4), the heating rate is 5 - 10 °C / min.

6. A Ce 3+ activated blue long afterglow material, characterized in that: This material has multiple characteristics including photochromism, photoluminescence, long - persistent luminescence, and near - infrared excitation - regenerated long - persistent luminescence.

7. A Ce 3+ activated blue long afterglow material, characterized in that: Its photochromic property is manifested as that after being excited by ultraviolet light, the color of this long - persistent phosphor material will change from white to bluish - gray and then return to white after 30 - 60 min; The photoluminescence characteristics show that the excitation wavelength ranges of the long-afterglow material are 290 - 340 nm and 340 - 390 nm respectively, corresponding to the 4f→5d1 and 4f→5d2 transitions of Ce 3+ ions. The emission wavelength of the long-afterglow material is located in the range of 400 - 600 nm, and the peak position is 455 - 458 nm, showing blue luminescence, corresponding to the 5d1→ 3+ F 2 / 5 / 2 F 2 transition of Ce 7 / 2 ; The long - persistent luminescence property is manifested as that after being excited by ultraviolet light for 5 - 10 min and then stopping the excitation, this material shows blue long - persistent luminescence with a persistent time of up to 30 h; The near - infrared excitation - regenerated long - persistent luminescence is manifested as follows: when the afterglow disappears and then it is excited by 980 nm near - infrared light, this material can re - emit blue up - conversion luminescence, and after stopping the excitation, the blue afterglow can last for 4 h.

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