WO2021227284A1 - Rare-earth-doped fluoride long-afterglow particle, preparation method therefor and use thereof - Google Patents

Abstract

A rare-earth-doped fluoride long-afterglow particle, comprising a fluoride matrix and a rare earth doping ion, i.e. Ln³⁺, doped in the fluoride matrix. The fluoride matrix is selected from AReF₄ or BaF₂, wherein A is selected from alkali metals, and Re is selected from one or more of Y, La, Gd and Lu. The rare earth doping ion, Ln³⁺, is selected from one or more of Pr³⁺, Sm³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tb³⁺, Nd³⁺ and Tm³⁺. The afterglow time of the fluoride long-afterglow particle after X-ray irradiation can be up to 150 days.

Description

Rare earth doped fluoride long afterglow particles and preparation method and application thereof

This application claims the priority of a Chinese patent application filed with the Chinese Patent Office on May 15, 2020, the application number is 202010411734.4, and the invention title is "a rare earth-doped fluoride long afterglow particle and its preparation method and application". The entire content is incorporated into this application by reference.

Technical field

The invention belongs to the technical field of luminescent materials, and specifically relates to a rare earth-doped fluoride long afterglow particle and a preparation method and application thereof.

Background technique

Long afterglow materials are a type of photoluminescent materials that can store excitation energy in material defects, and slowly release the stored energy in the form of radioluminescence after the excitation light stops. Due to its unique luminescence properties, long afterglow materials are widely used in security warnings, night decorations, security and anti-counterfeiting, in vivo imaging, photodynamic therapy, bioanalysis, photocatalysis, and solar cells. Most of the traditional long-lasting materials are chalcogenide compounds. Among them, SrAl ₂ O ₄ :Eu ²⁺ /Dy ³⁺ , ZnS:Cu, and ZnGa ₂ O ₄ :Cr are representative long-lasting materials. In the past few decades, in order to induce the formation of inherent defects in materials, long afterglow materials are usually synthesized by high-temperature solid-phase methods at a temperature higher than 1000°C. Although the high-temperature solid-phase method is conducive to the synthesis of high-efficiency luminescent long-lasting materials, the high-temperature synthesis is not conducive to the morphology control and surface modification of the materials, which greatly hinders its application in the fields of biomedicine and flexible electronic devices. The top-down synthesis method destroys the surface structure of the material by grinding the bulk material into a nano-scale material, resulting in a decrease in its luminous efficiency and afterglow life. In recent years, the nano-scale long afterglow materials synthesized by low-temperature hydrothermal method have controllable morphology and easy surface modification, but the low temperature is not conducive to the generation of defects, its luminous efficiency is low, and the afterglow time is short. Therefore, there are still major challenges in synthesizing high-efficiency colloidal long afterglow particles with controllable morphology, size, and surface.

Summary of the invention

In view of this, the technical problem to be solved by the present invention is to provide a rare earth-doped fluoride long afterglow particle and its preparation method and application. The present invention can realize the synthesis of controllable morphology, size and surface chemistry at low temperature. High-efficiency long afterglow particles for X-ray detection, display and imaging.

The present invention provides a rare earth-doped fluoride long afterglow particle, comprising a fluoride matrix and a rare earth doped ion Ln ³⁺ doped in the fluoride matrix, and the fluoride matrix is selected from AReF ₄ or BaF ₂ ;

Wherein, said A is selected from alkali metals;

The Re is selected from one or more of Y, La, Gd and Lu;

The rare earth doped ion Ln ^{3+ is} selected from one or more of ^{Pr 3+} , Sm ³⁺ , Dy ³⁺ , Ho ³⁺ , Er ³⁺ , Tb ³⁺ , Nd ³⁺ and Tm ^3+;

The doping amount of the rare earth doped ions is 0.1-20 mol%;

The afterglow time of the fluoride long afterglow particles after X-ray irradiation can be as high as 150 days.

Preferably, the particle size of the long afterglow particles is adjustable from 10 nm to 150 μm.

Preferably, the emission wavelength of the long afterglow particles is tunable from 350 to 1600 nm.

Preferably, it further comprises a coating layer coated on the surface of the fluoride substrate, the coating layer is selected from fluoride, and the fluoride is selected from AReF ₄ or BaF ₂ ;

Wherein, the A is selected from alkali metals, and the Re is selected from one or more of Lu, Y, Gd and La.

Preferably, the long afterglow particles are selected from NaY _0.8 Gd _0.05 F ₄ : Tb _0.15 , NaLu _0.8 Gd _0.05 F ₄ : Tb _{0.15 , or NaLu 0.8} Gd _0.05 F ₄ : Tb _0.15 @NaYF ₄ having a core-shell structure.

The present invention also provides a method for preparing the above-mentioned long afterglow particles, which includes the following steps:

A) Adding rare earth salt to the two-phase solvent of oleic acid and octadecene, stirring and mixing, and performing heating reaction under vacuum conditions to obtain a reaction liquid;

B) Adding lye and ammonium fluoride to the reaction solution for preheating reaction, removing the solvent, and then performing heating reaction to obtain long afterglow particles.

Preferably, in step A), the temperature of the heating reaction is 130-180°C, and the time is 10-30 min;

In step B), the temperature of the preheating reaction is 30-60°C, and the time is 20-60 min;

The heating reaction is to raise the temperature to 260-320°C at a rate of 10-30°C/min, and react for 0.5-2h.

The present invention also provides a method for preparing the above-mentioned long afterglow particles, which includes the following steps:

After sodium citrate, rare earth salt, sodium fluoride and water are mixed and stirred, the hydrothermal reaction is carried out under airtight conditions to obtain long afterglow particles.

Preferably, the temperature of the hydrothermal reaction is 180-240°C, and the time is 2-24h.

The present invention also provides an application of the rare earth-doped fluoride long afterglow particles in biomarking, X-ray detection, display and imaging.

Compared with the prior art, the present invention provides a rare earth-doped fluoride long afterglow particle, comprising a fluoride matrix and a rare earth doped ion Ln ³⁺ doped in the fluoride matrix. The fluoride The matrix is selected from AReF ₄ or BaF ₂ ; wherein, the A is selected from alkali metals, the Re is selected from one or more of Y, La, Gd and Lu; the rare earth doped ion Ln ^{3+ is} selected from One or more of Pr ³⁺ , Sm ³⁺ , Dy ³⁺ , Ho ³⁺ , Er ³⁺ , Tb ³⁺ , Nd ³⁺ and Tm ³⁺ ; the fluoride long afterglow particles are exposed to X-rays The afterglow time can be as high as 150 days. The rare earth-doped fluoride long afterglow particles provided by the present invention have easy-to-control morphology, uniform size, good dispersibility, very excellent long afterglow luminescence performance, and good cycle stability. It solves the contradiction between the uncontrollable morphology of traditional high-temperature solid-phase synthesis of long afterglow and the low luminous efficiency of low-temperature hydrothermal synthesis, and provides a guiding method for the synthesis of new long-lasting particles and the exploration of their luminescence mechanism. The long afterglow synthesized by the invention shows great potential in the fields of flexible electronic equipment, biomedicine, high-energy physics and artificial intelligence. The rare earth-doped fluoride long afterglow particles prepared by the present invention show good long afterglow luminescence performance after X-rays are stopped, that is, it has memory function for X-rays, so it can be used for X-ray marking, detection, display and imaging And other fields.

Description of the drawings

Figure 1 shows the synthesis method ^{of Tb 3+ doped fluoride nanoparticles;}

Figure 2 shows the morphology characterization ^{of Tb 3+ doped fluoride nanoparticles;}

Figure 3 shows the XRD and long afterglow decay curves ^{of Tb 3+ doped fluoride nanoparticles;}

Figure 4 shows the XRD and long afterglow decay curves of fluoride nanoparticles doped with different concentrations of Tb ^3+;

Figure 5 shows the comparison of optical properties of fluoride long afterglow materials with different substrates;

Figure 6 shows the optical performance characterization ^{of Tb 3+ doped fluoride nanoparticles;}

Figure 7 is a ^{picture of long afterglow attenuation of Tb 3+} doped liquid-phase fluoride nanoparticles;

Figure 8 ^{shows the afterglow performance comparison between Tb 3+} doped fluoride nanoparticles and traditional commercial long-lasting materials;

Figure 9 shows the luminescence of solid powders of fluoride materials doped with different rare earth luminescence centers;

Figure 10 shows the morphological characterization of traditional commercial long-lasting materials;

Figure 11 ^{shows the comparison of optical properties between Tb 3+} -doped fluoride nanoparticles and traditional commercial long-lasting materials;

Figure 12 shows the morphology of fluoride long afterglow nanoparticles doped with different rare earth ion luminescence centers;

Figure 13 is a photophysical characterization of fluoride long afterglow nanoparticles doped with different rare earth ion luminescence centers;

Figure 14 ^{shows the luminescence performance test of Tb 3+} doped fluoride nanoparticles under different X-ray doses, different time and temperature conditions;

Figure 15 ^{shows the optical and thermal excitation of Tb 3+} -doped fluoride long-lasting nanoparticles;

Figure 16 shows the optical characterization of rare earth fluoride long-lasting nanoparticles with core-shell structure;

_{Figure 17 shows the morphology characterization of NaLuF 4} :Tb ³⁺ /Gd ³⁺ (15/5mol%) microdisks synthesized by hydrothermal method;

_{Figure 18 is the long afterglow decay curve of BaF 2} :Tb (15 mol%) synthesized by the co-precipitation method.

Detailed ways

The present invention provides a rare earth-doped fluoride long afterglow particle, comprising a fluoride matrix and a rare earth doped ion Ln ³⁺ doped in the fluoride matrix, and the fluoride matrix is selected from AReF ₄ or BaF ₂ ;

Wherein, the A is selected from alkali metals, and the Re is selected from one or more of Y, La, Gd and Lu;

The rare earth doping ion Ln ^{3+ is} selected from one or more of ^{Pr 3+} , Sm ³⁺ , Dy ³⁺ , Ho ³⁺ , Er ³⁺ , Tb ³⁺ , Nd ³⁺ and Tm ^3+;

The afterglow time of the fluoride long afterglow particles after X-ray irradiation can be as high as 150 days.

The rare earth-doped fluoride long afterglow particles provided by the present invention include a fluoride matrix, and the fluoride matrix is selected from AReF ₄ or BaF ₂ ;

When the fluoride matrix is selected from AReF ₄ , the chemical formula of the rare earth-doped fluoride long afterglow particles is ARe _(1-x) F ₄ : Ln ³⁺ _x , where x takes a value of 0.001 to 0.2, Preferably it is 0.05-0.15.

The A is selected from alkali metals, namely one or more of Na, Li, K, Rb and Cs. In the present invention, when A is Na, the luminescence of the rare earth-doped fluoride long afterglow particles The best performance.

The Re is selected from one or more of Y, La, Gd and Lu. In some specific embodiments of the present invention, the Re is selected from Y; in some specific embodiments of the present invention, the Re Is selected from Lu; in some specific embodiments of the present invention, the Re is selected from Gd; in some specific embodiments of the present invention, the Re is selected from Lu and Gd.

The doping amount of the rare earth doping ion is 0.1-20 mol%; the rare earth doping ion Ln ^{3+ is} selected from Pr ³⁺ , Sm ³⁺ , Dy ³⁺ , Ho ³⁺ , Er ³⁺ , Tb ³⁺ One or more of Nd ³⁺ and Tm ^{3+ , preferably Tb 3+} ; when the rare earth doping ion is selected from Tb ³⁺ , the performance of the rare earth doped fluoride long afterglow particles is the best. The afterglow time after radiation can be as high as 150 days.

When the fluoride is BaF ₂ , the chemical formula of the rare earth doped fluoride long afterglow particles is BaF ₂ : Ln ³⁺ _x ; x is 0.001 to 0.2. Wherein, x represents the ratio of the doping amount of rare earth elements to the total amount of the Ba element and the doped rare earth elements.

Compared with the fluoride matrix selected from AReF ₄ , the use of rare earth materials as the matrix is avoided, and the cost of raw materials is effectively reduced.

Wherein, the doping amount x of the rare earth doping ion is 15 mol%; the rare earth doping ion Ln ^{3+ is} selected from Pr ³⁺ , Sm ³⁺ , Dy ³⁺ , Ho ³⁺ , Er ³⁺ , Tb ³ One or more of ⁺ , Nd ³⁺ and Tm ^{3+ is preferably Tb 3+} .

In some specific embodiments of the present invention, the long afterglow particles are selected from particles with a chemical formula of NaY _0.8 Gd _0.05 F ₄ : Tb _0.15 or NaLu _0.8 Gd _0.05 F ₄ : Tb _0.15 . Compared with particles of other chemical formulas, the particles have Stronger afterglow intensity (1 to 2 orders of magnitude higher) and longer afterglow time (afterglow time can be as high as 150 days).

In the present invention, the long afterglow particles can also be long afterglow particles with a core-shell structure, that is, the particles described above are cores, and a coating layer is coated on the surface thereof, and the coating layer is optional From fluoride, the fluoride is selected from AReF ₄ or BaF ₂ ;

Wherein, the A is selected from alkali metals, that is, one or more of Na, Li, K, Rb and Cs, and the Re is selected from two or more of Lu, Y, Gd and La.

Among them, the long afterglow particles with a core-shell structure can effectively passivate surface defects and prevent the quenching of luminescence by polar molecules such as water and ethanol in the solution.

In some specific embodiments of the present invention, the long afterglow particles are NaLuF ₄ :Ln ³⁺ /Gd ³⁺ @NaYF ₄ , NaLuF ₄ :Ln ³⁺ /Gd ³⁺ @NaLuF ₄ or NaLuF ₄ :Ln ³⁺ /Gd ³⁺ @CaF ₂ and other core-shell structures.

In some specific embodiments of the present invention, the chemical formula of the long afterglow particles with a core-shell structure is: NaLu _0.8 Gd _0.05 F ₄ :Tb _0.15 @NaYF ₄ , compared with particles without an inert shell layer, Because it can effectively passivate surface defects and prevent the quenching of light by polar molecules such as water and ethanol in the solution, it has stronger long afterglow intensity (5 times the intensity) and long afterglow time.

In the present invention, the particle size of the long afterglow particles is 10 nm to 150 μm. Wherein, in the present invention, the particle size and morphology of the long afterglow particles can be controlled by adjusting the process parameters of the preparation method, so as to obtain long afterglow particles with uniform particle size and good dispersibility. According to the present invention, the particle size of the long afterglow particles can be controlled at the nanometer level or the micrometer level according to needs, so as to obtain corresponding nanoparticles or microparticles.

The emission wavelength of the long afterglow particles can be adjusted from 350 to 1600 nm. In some specific embodiments of the present invention, the emission wavelength of the long afterglow particles is adjustable from 350 to 800 nm.

In some specific embodiments of the present invention, the emission wavelength is adjusted ^{by doping different rare earth luminescent ions Ln 3+.}

In the present invention, the afterglow time of the long afterglow particles after X-ray irradiation can be as high as 150 days, and the minimum can be as high as 14 days. Among them, the performance of Tb-doped fluoride long afterglow particles is superior to that of other kinds of rare earth elements. In some specific embodiments of the present invention, NaLuF ₄ : Tb (15 mol%) (the chemical formula indicates that in _{the long afterglow particles with NaLuF 4} as the matrix, Tb is the doping element, and the doping amount of Tb accounts for the total moles of Tb and Lu 15 mol% of the amount, the afterglow time of other chemical formulas in the present invention can last at least 20 days. In some specific embodiments of the present invention, _{the particles with the chemical formula NaLu 0.8} Gd _0.05 F ₄ :Tb _{0.15 have} a afterglow time of up to 150 days after X-ray irradiation.

The X-ray irradiation intensity and time affect the long afterglow performance of the particles prepared by the present invention. As the X-ray irradiation intensity and time increase, the long afterglow luminescence intensity and time of the prepared material increase. When the X-ray irradiation time (50kV, 80μA) is 300 seconds, the long afterglow emission spectrum can still be measured by the spectrometer at 150 days.

Due to the low-phonon vibration energy of the host crystal and the unique ff orbital transition of the lanthanide rare earth ion in the lattice, the alkali metal lanthanide rare earth fluoride (NaLnF ₄ ) crystal is an ideal material for studying nonlinear optics. High-energy X-ray photons collide with atoms in the lattice of alkali metal lanthanide rare earth fluorides (such as fluorine atoms) through momentum and energy transfer and elastically collide, which is easy to produce a new electron trap defect (Frenkel defect) ). Unlike the traditional thiooxy group long afterglow that can only induce defect formation under high-temperature reactions, fluoride materials undergo X-ray radiation, fluoride ions migrate from the initial position to the lattice to generate anion vacancies (V _F ) and interstitial ions ( I _F ). Anion vacancies and interstitial ions can slowly recombine and release energy under the action of heat, light or mechanical energy and transfer to the luminescence center to produce long afterglow luminescence, which is a new type of long afterglow luminescence phenomenon. Rare earth fluorides based on alkali metal lanthanides can be synthesized by low-temperature co-precipitation or hydrothermal methods. This synthesis method can synthesize high-efficiency long afterglow particles with controllable morphology, size, and surface chemistry at low temperatures for use in X Radiation detection, display and imaging.

The present invention also provides a preparation method of the above-mentioned rare earth-doped fluoride long afterglow particles. The preparation method may be a hydrothermal method or a co-precipitation method.

Wherein, the co-precipitation method is prepared according to the following method:

A) Add the rare earth salt to the two-phase solvent of oleic acid and octadecene, and conduct a heating reaction under vacuum to obtain a reaction liquid;

B) Adding lye and ammonium fluoride to the reaction solution for preheating reaction, removing the solvent, and then performing heating reaction to obtain long afterglow particles.

Among them, the volume ratio of oleic acid to octadecene is (3-10): (5-15).

The rare earth salt is selected from rare earth acetate, rare earth chloride, and rare earth nitrate.

The temperature of the heating reaction is 130-180°C, preferably 150-160°C; the time is 10-30 min;

The lye is a methanol solution of sodium hydroxide;

The temperature of the preheating reaction is 30-60°C, preferably 40-50°C, and the time is 20-60 min;

The solvent removal after preheating reaction is mainly to remove methanol and water. The specific method is as follows:

Raise the temperature to 70°C and steam methanol for 10-20 minutes, then raise the temperature to 100-120°C to remove water for 20-60 minutes;

After the water is removed, the heating reaction is carried out. Specifically, the reaction system is heated at a rate of 10-30°C/min, preferably 15-25°C/min to 260-320°C, preferably 280-300°C, and the reaction is 0.5- 2h, preferably 1.0 to 1.5h.

After the reaction, it is cooled to room temperature; the reaction product is washed with a mixed solution of cyclohexane and ethanol for 2 to 4 times and then dissolved in cyclohexane or toluene for later use.

The present invention regulates the concentration of doped ions, the ratio of oleic acid and octadecene during the synthesis process, and the synthesized particle size can be adjusted between 10nm and 150um, and the particles are all hexagonal crystal phases.

The hydrothermal method is prepared according to the following method:

After sodium citrate, rare earth salt, sodium fluoride and water are mixed and stirred, the hydrothermal reaction is carried out under airtight conditions to obtain long afterglow particles.

Specifically, in the present invention, after mixing an aqueous solution of sodium citrate, an aqueous solution of rare earth salts, and an aqueous solution of sodium fluoride, the hydrothermal reaction is performed under airtight conditions;

The temperature of the hydrothermal reaction is 180-240°C, preferably 200-220°C, and the reaction time is 2-24 hours, preferably 12 hours.

After the hydrothermal reaction is completed, the reaction product is washed 2 to 4 times with a mixed solution of water and ethanol and then dissolved in cyclohexane or toluene.

In the present invention, the rare earth-doped fluoride long afterglow particles with a core-shell structure take the rare earth-doped fluoride long afterglow particles as the core, and the surface is coated with a fluoride inert shell layer.

The rare earth-doped fluoride long afterglow particles with a core-shell structure can be prepared by a co-precipitation method, and the specific method is:

Add the rare earth salt to the two-phase solvent of oleic acid and octadecene, and perform heating reaction under vacuum conditions to obtain a reaction liquid;

Then, the rare earth-doped fluoride long afterglow particles prepared above are added, the lye and ammonium fluoride are preheated and the solvent is removed, and then the heating reaction is performed to obtain the long afterglow particles.

Among them, the volume ratio of oleic acid to octadecene is (3-10): (5-15).

The rare earth salt is selected from rare earth acetate, rare earth chloride, and rare earth nitrate;

The temperature of the heating reaction is 130-180°C, preferably 150-160°C; the time is 10-30 min;

The lye is a methanol solution of sodium hydroxide;

The temperature of the preheating reaction is 30-60°C, preferably 40-50°C, and the time is 20-60 min.

The solvent removal after preheating reaction is mainly to remove methanol and water. The specific method is as follows:

Raise the temperature to 70°C and steam methanol for 10-20 minutes, then raise the temperature to 100-120°C to remove water for 20-60 minutes;

After the water is removed, the heating reaction is carried out. Specifically, the reaction system is heated at a rate of 10-30°C/min, preferably 15-25°C/min to 260-320°C, preferably 280-300°C, and the reaction is 0.5- 2h, preferably 1.0 to 1.5h.

After the reaction is completed, it is cooled to room temperature; the reaction product is washed 2-4 times with a mixed solution of cyclohexane and ethanol and then dissolved in cyclohexane or toluene for later use.

Through the co-precipitation synthesis method, an inert layer can be coated on the surface of the nanomaterial to enhance the luminescence intensity and long afterglow emission time of the material under X-ray excitation. The composition of a material can be NaReF ₄ :Ln ³⁺ @ NaReF ₄ core-shell structure, Re in the core structure and Re in the coating structure can independently be one or more of Y, Gd, La and Lu.

In the present invention, organic acid is used as surface ligand, unsaturated olefin is used as reaction solvent, and a series of novel fluoride long afterglow particles with different emission wavelengths and adjustable particle size are prepared by low-temperature co-precipitation method and hydrothermal preparation.

The long afterglow particles prepared by the present invention have the characteristic of long afterglow luminescence after X-ray irradiation. After the luminescence is attenuated, thermal excitation or light excitation can be used to promote the recovery of the Frenkel defect to stimulate the generation of long afterglow.

Thermal excitation or optical excitation is used to realize the application of long afterglow particles in biomarking, X-ray detection, display and imaging.

(1) The present invention provides a method for preparing rare earth fluoride long afterglow particles, which adopts a low-temperature solution method to prepare a series of long afterglow particles with tunable emission wavelengths from 350 to 1600 nm by doping different rare earth luminescent ions. The particle size of the long afterglow luminescent material prepared by the method is in the range of 10 nm to 150 μm, and the morphology and size of the long afterglow luminescent material are uniform and the dispersibility is good.

(2) The present invention overcomes the contradiction between the traditional long afterglow high-temperature calcination morphology and size unevenness and low-temperature hydrothermal synthesis of low luminous efficiency, and proposes a low-temperature wet chemical synthesis (thermal co-precipitation method or hydrothermal method) A series of high-efficiency long afterglow luminous particles, the afterglow time can reach more than 150 days. Lanthanide fluorescent particles have good stability and strong anti-interference ability in complex biological environment;

(3) The fluoride long afterglow material prepared by the present invention has the properties of long afterglow luminescence after the X-ray excitation is stopped, and also has the optical properties of light excitation and thermal excitation, that is, the use of X-ray (>1keV), ultraviolet light (200 ～400nm), visible light (400～700nm), near-infrared (700～1100nm) or heating (30-400℃) can promote the release of electrons in the defect to the center of the luminescent ion, resulting in a strong afterglow phenomenon. This phenomenon It has practical application value in X-ray imaging, X-ray detection and display.

(4) The fluoride long afterglow material prepared by the present invention has the advantages of uniform particle preparation, low cost, controllable morphology, etc., and has applications in the preparation of flexible devices and transparent devices. Because the material produces long afterglow under the action of X-rays, it can be used in biomarkers, X-ray treatment, X-ray detection, X-ray display, X-ray imaging and other fields.

In order to further understand the present invention, the rare earth-doped fluoride long afterglow particles provided by the present invention and the preparation method and application thereof will be described below in conjunction with examples. The protection scope of the present invention is not limited by the following examples.

Example 1

Synthesis of Rare Earth Fluoride Long Afterglow Nanomaterials NaLuF ₄ :Tb ³⁺ /Gd ^3+:

This method adopts the thermal co-precipitation method (Figure 1 the schematic flow diagram of the thermal co-precipitation method for synthesizing different rare earth fluoride long afterglow nano materials) to synthesize fluoride long afterglow nanoparticles of different sizes and doped with different rare earth ions. Take Tb ³⁺ as the luminous center as an example:

A total of 0.5 mmol of rare earth acetate (terbium acetate, gadolinium acetate, and lutetium acetate, the specific ratio of the three is shown in Figure 3) was added to 5 mL of oleic acid and 7.5 mL of octadecene. Stir in a double-necked round-bottom flask, vacuum and heat to 160°C; react for 15 minutes to form a rare earth oleic acid complex. After the reaction was cooled to room temperature, 10 mL of methanol dissolved 1.25 mmol sodium hydroxide solution and 2 mmol ammonium fluoride solution were added. The temperature was raised to 50°C and stirred and mixed for 30 minutes. The temperature was raised to 70°C to evaporate methanol and then to 100°C to remove water vapor. After the start of pumping for 20 minutes, the air was exchanged 3 times. Heat to 300°C and react for 1h. After the obtained rare earth particles were purified with ethanol/cyclohexane (precipitation/dispersion) three times, the product was dispersed in cyclohexane for further use.

Figure 2 shows the structure and morphology ^{of Tb 3+ doped fluoride nanoparticles.}

In Figure 2, a to e are electron microscope images and corresponding particle size distribution diagrams of nanoparticles doped with different luminescent rare earth ions;

Among them, a is NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/35mol%), and its particle size is 14.96±0.66nm;

b is NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/25mol%), and its particle size is 21.86±0.96nm;

c is NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/15mol%), and its particle size is 49.57±1.54nm;

d is NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/5mol%), and its particle size is 111.0±3.3nm;

e is NaLuF ₄ : Tb ³⁺ (15mol%), and its particle size is 129.3±8.8nm;

It can be seen from the figures a to e that the size of the nanoparticles can be adjusted by doping.

f is the size control statistics of the rare earth fluoride nanoparticles mentioned above. It can be seen from the figure f that as the doping amount of lutetium element increases, the particle size gradually increases;

Figure 3a shows the X-ray powder diffraction pattern (XRD) characterization of rare earth fluoride long afterglow nanoparticles;

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (15/35mol%) means that the molar ratio of Lu:Tb:Gd is 50:15:35;

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (15/25mol%) means that the molar ratio of Lu:Tb:Gd is 60:15:25;

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (15/15mol%) means that the molar ratio of Lu:Tb:Gd is 70:15:15;

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (15/5mol%) means that the molar ratio of Lu:Tb:Gd is 80:15:5;

NaLuF ₄ :Tb ³⁺ (15mol%) means that the molar ratio of Lu:Tb is 85:15;

Figure 3b shows the long afterglow luminescence decay curve of Tb-doped nanoparticles. The lines in Figure 3b from top to bottom are NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/5mol%), NaLuF ₄ : Tb ³⁺ (15mol%), NaLuF ₄ : Tb ³⁺ /Gd ³⁺ ( 15/15mol%), NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/25mol%), NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/35mol%)

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (15/35mol%) means that the molar ratio of Lu:Tb:Gd is 50:15:35;

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (15/25mol%) means that the molar ratio of Lu:Tb:Gd is 60:15:25;

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (15/15mol%) means that the molar ratio of Lu:Tb:Gd is 70:15:15;

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (15/5mol%) means that the molar ratio of Lu:Tb:Gd is 80:15:5;

NaLuF ₄ :Tb ³⁺ (15mol%) means that the molar ratio of Lu:Tb is 85:15;

Figure 4 shows the characterization of nanoparticles doped with different concentrations of Tb ³⁺ ions. The long afterglow luminescence properties of nanomaterials can be adjusted by doping concentration. With the increase of terbium element doping, the intensity of afterglow gradually increases. extend. When the Tb ³⁺ doping amount is 15 mol%, its performance is the best. As the amount of Tb ³⁺ ions continues to be doped, ^{cross-relaxation occurs due to the excessively high Tb 3+} concentration, which reduces the afterglow intensity.

In Figure 4, a is the X-ray powder diffraction pattern (XRD) characterization of rare earth fluoride long afterglow nanoparticles;

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (15/5mol%) means that the molar ratio of Lu:Tb:Gd is 80:15:5;

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (10/10mol%) means that the molar ratio of Lu:Tb:Gd is 80:10:10;

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (5/15mol%) means that the molar ratio of Lu:Tb:Gd is 80:5:15;

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (2/18mol%) means that the molar ratio of Lu:Tb:Gd is 80:2:18;

NaLuF ₄ :Tb ³⁺ (20mol%) means that the molar ratio of Lu:Tb is 80:20;

b is the long afterglow luminescence decay curve ^{of Tb 3+ doped nanoparticles.} In Figure 4b, the lines from top to bottom are NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/5mol%), NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (10/10mol%), NaLuF ₄ : Tb ^{3 +} (20mol%), NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (5/15mol%), NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (2/18mol%).

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (15/5mol%) means that the molar ratio of Lu:Tb:Gd is 80:15:5;

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (10/10mol%) means that the molar ratio of Lu:Tb:Gd is 80:10:10;

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (5/15mol%) means that the molar ratio of Lu:Tb:Gd is 80:5:15;

NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (2/18mol%) means that the molar ratio of Lu:Tb:Gd is 80:2:18;

NaLuF ₄ :Tb ³⁺ (20mol%) means that the molar ratio of Lu:Tb is 80:20.

Example 2

Synthesis of rare earth fluoride long afterglow nanomaterials NaYF ₄ :Tb ³⁺ (15mol%) and NaGdF ₄ :Tb ³⁺ (15mol%). The particles of NaYF ₄ :Ln ³⁺ (15 mol%) and NaGdF ₄ :Ln ³⁺ (15 mol%) were synthesized by the thermal co-precipitation method, which was consistent with the method in Example 1.

As shown in Figure 5, as the X-ray absorption capacity of yttrium, gadolinium, and lutetium gradually increases, NaYF ₄ : Tb ³⁺ (15 mol%) and NaGdF ₄ : Tb ³⁺ (15 mol%) and NaLuF ₄ : Tb ³⁺ (15mol%) The emission spectrum under X-ray excitation gradually increases. However, due to the presence of Gd ³⁺ intermediate state, there may exist non-radiative transitions, thus ^{_{NaGdF 4: Tb 3+ (15mol%}} ) as compared to the afterglow decay curve ^{_{NaYF 4: Tb 3+ (15mol%}} ) and NaLuF _4: Tb ^{3 +} (15mol%) Decay faster.

Example 3

The rare earth fluoride long afterglow particles described in the following Examples 4 to 5 are prepared by the hydrothermal method:

Add sodium citrate (0.5mL; 0.3M), Ln(NO ₃ ) ₃ (2mL; 0.2M; the moles of _{Lu(NO 3} ) ₃ , Gd(NO ₃ ) ₃ and Tb(NO ₃ ) _{3 into the beaker} The ratio is 80:5:15) (In other chemical formulas, the specific type and ratio of Ln can be found in the chemical formula). NaF (9.6 mL; 0.5M) was added under stirring at room temperature. The reaction system was stirred at room temperature for 30 minutes. The above reaction solution was poured into the inner bladder of the hydrothermal reactor, the device was screwed tightly, and the reaction was carried out in an oven at 220°C for 12 hours. Wash the reaction product 2-4 times with a mixed solution of cyclohexane and ethanol and then dissolve it in cyclohexane or toluene to obtain the rare earth fluoride long afterglow nanomaterial;

Refer to Figure 17, which is an electron microscope image _{of NaLuF 4} :Tb ³⁺ /Gd ^{3+ (15/5 mol%) microdisks synthesized by hydrothermal method.}

Example 4

Luminescence Test of Rare Earth Fluoride Long Afterglow Materials Excited by X-ray

The luminescence of the rare earth fluoride long afterglow material prepared in Example 3 was characterized by a spectrometer, a digital camera and a CCD. The long afterglow luminescence of the material can be realized by X-ray excitation. This method uses 50kV and 70kV X-ray light sources to test the samples. Put the dried rare earth fluoride long afterglow material in a metal sample cell, turn on the X-ray light source to excite the sample, then stop the X-ray, and test the long afterglow luminescence by a spectrometer.

Figure 6-9 shows the optical characterization of rare earth fluoride long afterglow nanoparticles.

In FIG. 6, a is a transmission electron microscope image of a rare earth fluoride long afterglow particle with _{a chemical composition of NaLuF 4} :Tb ³⁺ /Gd ^{3+ (15/5 mol%) prepared in Example 1.}

b is _{the emission spectrum of NaLuF 4} :Tb ³⁺ /Gd ³⁺ (15/5mol%) particles excited by X-ray, the long afterglow emission spectrum after the X-ray is turned off, and the corresponding long afterglow emission spectrum after 150 days. It can be seen from b that the Tb ³⁺ ion-doped rare earth fluoride long afterglow NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/5mol%) exhibits a characteristic emission peak ^{of Tb 3+ under the excitation of X-rays 5} D ₄ → ⁷ F ₄ (489nm), ⁵ D ₄ → ⁷ F ₅ (546nm) and ⁵ D ₄ → ⁷ F ₆ (584nm). After the X-ray is turned off, the long afterglow spectrum is compared with the emission spectrum under X-ray excitation (50kV, 80μm, 300seconds). The peak shape and peak position have not changed. The long afterglow emission spectrum can still be measured after 150 days. ；

c is the charging process of NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (15/5mol%) long afterglow particles under X-rays and the decay kinetic curve of the long afterglow after charging. It can be seen from c that with NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/5mol%) long afterglow particles have a slow energy storage process under the excitation of X-rays, and their energy reaches saturation within 1.5 hours, and after the X-rays are turned off, their long afterglow intensity and The background still has a difference of 3 orders of magnitude;

Figure 7 shows the liquid long afterglow. It can be seen from d that the NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/5mol%) long afterglow particles in the solution phase can still be seen by the naked eye after one hour after the X-rays are stopped. afterglow;

Figure 8 shows _{the performance comparison between NaLuF 4} : Tb ³⁺ /Gd ³⁺ (15/5mol%) long afterglow particles and traditional long afterglow materials. In Figure 8, the lines from top to bottom are NaGd/LuF ₄ : Tb, SrAl ₂ O ₄ : Eu, Dy, SrAl ₂ O ₄ : Eu, Dy (After grinding), ZnS (ZnS: Cu, Co), ZGO: Cr (After calcination), ZGO: Cr (Before calcination).

In Figure 8:

SrAl ₂ O ₄ : Eu, Dy is: SrAl ₂ O ₄ : Eu ²⁺ , Dy ³⁺ commercial bulk long afterglow material, Eu ²⁺ , Dy ³⁺ doping ratio 1:2;

SrAl ₂ O ₄ : Eu, Dy (After grinding) is a commercialized bulk long afterglow material after grinding of _{SrAl 2} O ₄ : Eu ²⁺ , Dy ^3+;

ZGO:Cr (After calcination) is a traditional near-infrared emission long afterglow particle that is calcined at a high temperature of 950°C by ZGO:Cr NPs (950°C);

ZGO:Cr (Before calcination) is a traditional near-infrared emission long afterglow nanoparticle synthesized by ZGO:Cr NPs (220℃) 220℃ low-temperature hydrothermal method;

ZnS:Cu,Co is a commercialized chalcogenide long afterglow material of ZnS:Cu,Co;

It can be seen from Figure 8 that _{the long afterglow intensity of NaLuF 4} :Tb ³⁺ /Gd ³⁺ (15/5mol%) is 4 times that of the commercial long afterglow particles SrAl ₂ O ₄ :Eu ²⁺ ,Dy ³⁺ _{; SrAl 2} O ₄ : Eu ²⁺ , Dy ³⁺ after grinding, its luminous intensity is greatly reduced due to the destruction of the surface. Although the morphology of ZGO:Cr nanoparticles synthesized by hydrothermal method is uniform and controllable, the low temperature is not conducive to the formation of defects, and the long afterglow intensity is very weak.

Figure 9 shows the fluoride long afterglow nanoparticles doped with different rare earth luminescent ions. From left to right, their compositions are: NaLuF ₄ :Nd ³⁺ /Gd ³⁺ (1/19mol%), NaLuF ₄ :Tm ³⁺ / Gd ³⁺ (1/19mol%), NaLuF ₄ : Dy ³⁺ /Gd ³⁺ (0.5/19.5mol%), NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/5mol%), NaLuF ₄ : Er ^{3 +} /Gd ³⁺ (1/19mol%), NaLuF ₄ :Ho ³⁺ /Gd ³⁺ (1/19mol%), NaLuF ₄ :Sm ³⁺ /Gd ³⁺ (0.5/19.5mol%) and NaLuF ₄ : Pr ³⁺ /Gd ³⁺ (0.5/19.5 mol%) nanoparticles and their corresponding emission wavelength positions.

It can be seen from Figure 6-9 that the long afterglow luminescence signal can still be detected after 150 days. The material is relatively stable under X-rays, and can be dispersed in the solution to achieve stable long-lasting luminescence. The luminescence properties of rare earth fluoride materials have better long-lasting properties than traditional long-lasting luminescent materials under X-ray excitation. The fluoride matrix is used for the doping of different rare earth ions and realizes ultra-long long afterglow luminescence.

Figure 10-11 shows the performance comparison between rare earth fluoride long afterglow nanoparticles and traditional long afterglow nanoparticles;

In Figure 10,

a is SrAl ₂ O ₄ :Eu ²⁺ , Dy ³⁺ bulk crystals,

b is SrAl ₂ O ₄ :Eu ²⁺ ,Dy ³⁺ nano aggregate,

_{c is ZnGa 2} O ₄ :Cr ³⁺ nanoparticles synthesized by hydrothermal method,

_{d is ZnGa 2} O ₄ :Cr ³⁺ nano aggregate calcined at high temperature after hydrothermal method;

A～d in Figure 10 are all commercially available products

_{Figure 11a shows NaLuF 4} : Tb ³⁺ /Gd ³⁺ (15/5mol%) nanoparticles, commercially available SrAl ₂ O ₄ : Eu ²⁺ , Dy ³⁺ bulk crystals, and commercially available SrAl ₂ O prepared in Example 3. ₄ : Eu ²⁺ , Dy ³⁺ nanoparticles, commercially available ZnS: Cu, Co bulk crystals, commercially available ZnGa ₂ O ₄ : Cr ³⁺ (ZGO: Cr) nanoparticles (calcined at 950°C) and ZGO: Cr nanoparticles The emission spectra of particles (synthesized by hydrothermal method at 220°C) under X-ray excitation;

Figure 11b shows the kinetic curves of the above six long afterglow materials under continuous X-ray excitation; in Figure 11b, the lines from top to bottom are NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/5mol%) long afterglow nanometers Particles, ZnS: Cu, Co bulk crystals, ZGO: Cr nanoparticles (After calcination), SrAl ₂ O ₄ : Eu, Dy bulk crystals, SrAl ₂ O ₄ : Eu, Dy nanoparticles (After grinding), ZGO: Cr nanoparticles (Before calcination).

Figure 11c shows the comparison of the afterglow intensity of the above six kinds of long afterglow materials after normalization;

From Figures 10-11, it can be seen that although commercial long-lasting particles have high luminous intensity when synthesized at high temperature, their morphology is uncontrollable; although particles synthesized at low temperature have a controllable morphology, their luminous intensity is weak. The long afterglow of rare earth fluoride synthesized by co-precipitation method and hydrothermal method solves the contradiction between the uncontrollable morphology of traditional long afterglow synthesis at high temperature and the low luminous efficiency of synthesis at low temperature.

Figure 12 shows the morphology of fluoride long-lasting nanoparticles doped with different rare earth luminescence centers.

In FIG. 12, Pr represents NaLuF ₄ :Pr ³⁺ /Gd ³⁺ (0.5/19.5 mol%), which specifically represents long afterglow nanoparticles with a molar ratio of Lu:Pr:Gd of 80:0.5:19.5;

Sm stands for NaLuF ₄ :Sm ³⁺ /Gd ³⁺ (0.5/19.5 mol%), and specifically refers to long-lasting nanoparticles with a molar ratio of Lu:Sm:Gd of 80:0.5:19.5;

Ho stands for NaLuF ₄ :Ho ³⁺ /Gd ³⁺ (1/19mol%), which specifically refers to long-lasting nanoparticles with a molar ratio of Lu:Ho:Gd of 80:1:19;

Er stands for NaLuF ₄ :Er ³⁺ /Gd ³⁺ (1/19mol%), and specifically refers to long-lasting nanoparticles with a molar ratio of Lu:Er:Gd of 80:1:19;

Tb stands for NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (15/5 mol%), and specifically refers to long-lasting nanoparticles with a molar ratio of Lu:Tb:Gd of 80:15:5;

Dy stands for NaLuF ₄ :Dy ³⁺ /Gd ³⁺ (0.5/19.5 mol%), and specifically refers to long-lasting nanoparticles with a molar ratio of Lu:Dy:Gd of 80:0.5:19.5;

Tm stands for NaLuF ₄ : Tm ³⁺ /Gd ³⁺ (1/19 mol%), and specifically refers to long-lasting nanoparticles with a molar ratio of Lu:Tm:Gd of 80:1:19;

Nd stands for NaLuF ₄ :Nd ³⁺ /Gd ³⁺ (1/19mol%), which specifically refers to long-lasting nanoparticles with a molar ratio of Lu:Nd:Gd of 80:1:19;

Figure 12 shows the electron microscope characterization of the above 8 different rare earth ions doped.

Figure 13a is an X-ray powder diffraction pattern (XRD) of the above 8 different rare earth ions doped.

Figure 13b shows the fluoride long afterglow nanoparticles doped with the above 8 different rare earth ions (NaLuF ₄ : Pr ³⁺ /Gd ³⁺ (0.5/19.5mol%), NaLuF ₄ : Sm ³⁺ /Gd ³⁺ (0.5 /19.5mol% _{), NaLuF 4} : Ho ³⁺ /Gd ³⁺ (1/19mol%), NaLuF ₄ : Er ³⁺ /Gd ³⁺ (1/19mol%), NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/5mol%), NaLuF ₄ : Dy ³⁺ /Gd ³⁺ (0.5/19.5mol%), NaLuF ₄ : Tm ³⁺ /Gd ³⁺ (1/19mol%), and NaLuF ₄ : Nd ³⁺ /Gd ³⁺ (1/19mol%)) long afterglow luminescence spectrum characterization;

Figure 13c shows the eight kinds of fluoride long afterglow nanoparticles doped with different rare earth ions (NaLuF ₄ : Pr ³⁺ /Gd ³⁺ (0.5/19.5mol%), NaLuF ₄ : Sm ³⁺ /Gd ³⁺ (0.5/ 19.5mol%), NaLuF ₄ : Ho ³⁺ /Gd ³⁺ (1/19mol%), NaLuF ₄ : Er ³⁺ /Gd ³⁺ (1/19mol%), NaLuF ₄ : Tb ³⁺ /Gd ³⁺ ( 15/5mol%), NaLuF ₄ : Dy ³⁺ /Gd ³⁺ (0.5/19.5mol%), NaLuF ₄ : Tm ³⁺ /Gd ³⁺ (1/19mol%), and NaLuF ₄ : Nd ³⁺ /Gd ^{3 +} (1/19mol%)) color coordinate diagram;

Figure 13d shows the eight kinds of fluoride long afterglow nanoparticles doped with different rare earth ions (NaLuF ₄ : Pr ³⁺ /Gd ³⁺ (0.5/19.5mol%), NaLuF ₄ : Sm ³⁺ /Gd ³⁺ (0.5/ 19.5mol%), NaLuF ₄ : Ho ³⁺ /Gd ³⁺ (1/19mol%), NaLuF ₄ : Er ³⁺ /Gd ³⁺ (1/19mol%), NaLuF ₄ : Dy ³⁺ /Gd ³⁺ ( 0.5/19.5mol%), NaLuF ₄ : Tm ³⁺ /Gd ³⁺ (1/19mol%) and NaLuF ₄ : Nd ³⁺ /Gd ³⁺ (1/19mol%)) long afterglow intensity curve;

In Figure 13d, the lines from top to bottom are Dy, Pr, Er, Ho, Sm, Tm, and Nd.

It can be seen from Figures 12-13 that through the doping of different rare earth emission centers, the emission wavelength of the rare earth fluoride long afterglow particles can be adjusted between 350 and 800 nm.

Example 5

Optical and thermal excitation test of rare earth fluoride long afterglow materials

The light excitation and thermal excitation of the material are processed by X-ray (>1keV), ultraviolet light (200-400nm), visible light (400nm-700nm), near-infrared (700nm-1100nm) or heating (30-400 degrees Celsius). Strong afterglow luminescence phenomenon.

Figure 14 shows _{the luminescence performance test of NaLuF 4} : Tb ³⁺ /Gd ³⁺ (15/5mol%) nanoparticles under different X-ray doses, excitation times, and different temperatures;

a is the linear relationship between X-ray dose and radiation time;

b is _{the long afterglow attenuation curve of NaLuF 4} : Tb ³⁺ /Gd ³⁺ (15/5mol%) nanoparticles at different doses; in b, the top-down line corresponds to the measurement order of 16.263mGy, 10.832mGy, 5.421mGy, 1.355mGy, 0.357mGy, 0.054mGy;

c is _{the long afterglow decay curve of NaLuF 4} :Tb ³⁺ /Gd ³⁺ (15/5mol%) nanoparticles under X-ray excitation at different times; in c, the time corresponding to the top-down line is 300s and 180s respectively , 120s, 60s, 20s, 10s;

d is _{the long afterglow decay curve of NaLuF 4} :Tb ³⁺ /Gd ³⁺ (15/5mol%) nanoparticles at different temperatures. The top-down lines in d correspond to 330K, 280K, 308K, and 430K. , 230K, 180K, 130K, 80K.

It can be seen from Fig. 14 that the energy storage of long afterglow increases as the dose of absorbed X-rays increases and the time of X-ray excitation prolongs. The stronger the long afterglow intensity, the longer the afterglow time. The intensity and afterglow time of the long afterglow are different at different temperatures. At 330K, the long afterglow has the strongest intensity and the longest afterglow time.

Figure 15 shows the optical and thermal excitation phenomena of rare earth fluoride long afterglow nanoparticles _{. The Frenkel defect generated by X-ray excitation of NaLuF 4} :Tb ³⁺ /Gd ³⁺ (15/5mol%) is exposed to light and heat. Gradually recovers under the action of, producing a long afterglow phenomenon stimulated by light and heat.

Figure 15 | Characterization of optical and thermal excitation properties of rare earth fluoride long afterglow nanoparticles.

a is the photoexcitation phenomenon test of 480nm, 530nm, 620nm, 808nm, 980nm or 1064nm excitation light on the rare earth fluoride long afterglow NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/5mol%) nanoparticles; in a, from above The excitation light wavelengths corresponding to the lower line are 480 nm, 530 nm, 620 nm, 808 nm, 980 nm, and 1064 nm.

b is the X-ray dynamic curve of rare earth fluoride long afterglow NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (15/5mol%) nanoparticles under X-ray excitation, X-ray stop, and near-infrared excitation.

c is the luminous intensity and stability test of rare earth fluoride long afterglow NaLuF ₄ : Tb ³⁺ /Gd ³⁺ (15/5mol%) nanoparticles under heating conditions; in c, the inflection point of the broken line in the figure is divided into the upper part and In the lower part, the inflection point of the upper part represents the luminous intensity heated to 353K, and the inflection point of the lower part represents the luminous intensity at 298K after X-ray irradiation.

It can be seen from Figure 15 that the rare earth fluoride long afterglow nanoparticles have the properties of light excitation and thermal excitation. As the energy of the excitation light increases, the better the light excitation effect. Therefore, 480nm light has the strongest light excitation ability. As shown in Figure 15b, after several cycles of light excitation, the effect of light excitation gradually weakens. As shown in Figure 15c, the rare earth fluoride long afterglow nanoparticles have very good thermal excitation cycle stability. After ten cycles of X-ray excitation and thermal excitation, the thermal excitation intensity remains basically unchanged.

Example 6

Rare earth fluoride long afterglow nanomaterial NaLuF ₄ :Tb ³⁺ /Gd ³⁺ (15/5mol%)@NaYF ₄ Synthesis of core-shell structure:

Step 1: Add 1 mmol of rare earth acetate (terbium acetate, gadolinium acetate, lutetium acetate, the specific ratio of the three is 15:80:5) to 10 mL of oleic acid and 15 mL of octadecene. Stir in a double-necked round-bottom flask, vacuum and heat to 160°C; react for 15 minutes to form a rare earth oleic acid complex. The reaction was cooled to 120° C., 2.5 mmol sodium hydroxide solid powder was added to react for 20 minutes, and 4 mmol ammonium fluoride solid was added to react for 15 minutes. After vacuuming for 20 minutes, the air was exchanged three times to remove low-boiling solvents such as water. Heat to 295°C and react for 1h. After the obtained rare earth particles were purified with ethanol/cyclohexane (precipitation/dispersion) three times, the product was dispersed in cyclohexane for further use.

Step 2: Add 0.5mmol yttrium acetate to 4mL oleic acid and 6mL octadecene. Stir in a double-necked round-bottom flask, heat to 150°C; react for 15 minutes, and remove water. The temperature was lowered to 80°C, and the product in step 1 was added and reacted for 30 minutes to remove the cyclohexane solvent. After the reaction was cooled to room temperature, 10 mL of methanol dissolved 1.25 mmol sodium hydroxide solution and 2 mmol ammonium fluoride solution were added. The temperature was raised to 50°C and stirred and mixed for 30 minutes. The temperature was raised to 70°C to evaporate methanol and then to 100°C to remove water vapor. After the start of pumping for 20 minutes, the air was exchanged 3 times. add. Heat to 290°C and react for 1.5h. After the obtained core-shell structure rare earth particles are purified three times with ethanol/cyclohexane (precipitation/dispersion), the product is dispersed in cyclohexane for further use.

As shown in Figure 16b, the rare earth fluoride long afterglow nanomaterial with core-shell structure is coated with an inert shell layer on its surface, which is conducive to the passivation of surface defects and the isolation of polar molecules such as water and ethanol, thereby effectively improving the longevity. The intensity of afterglow is more than 5 times and the afterglow time is prolonged.

Example 7

A total of 1 mmol of rare earth acetate (terbium acetate, barium acetate, the molar ratio of the two is 15:85) was added to 5 mL of oleic acid and 15 mL of octadecene. Stir in a double-necked round-bottom flask, vacuum and heat to 160°C; react for 15 minutes to form a rare earth oleic acid complex. After the reaction was cooled to room temperature, 10 mL of methanol-dissolved 2.5 mmol sodium hydroxide solution and 2.5 mmol ammonium fluoride solution were added. The temperature was raised to 50°C and stirred and mixed for 30 minutes. The temperature was raised to 70°C to evaporate methanol and then to 100°C to remove water vapor. After the start of pumping for 20 minutes, the air was exchanged 3 times. Heat to 300°C and react for 1h. After the obtained rare earth particles were purified with ethanol/cyclohexane (precipitation/dispersion) three times, the product was dispersed in cyclohexane for further use.

As shown in Figure 18, BaF ₂ Tb (15 mol%) also has good long afterglow performance. Compared with the long afterglow of rare earth fluorides _{based on NaYF 4} , NaGdF ₄ and NaLuF _{4, its raw material cost is lower.} In practical applications, it has better potential.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications are also It should be regarded as the protection scope of the present invention.

Claims (10)

1. A rare earth doped fluoride long afterglow particle, which is characterized in that it comprises a fluoride matrix and a rare earth doped ion Ln ³⁺ doped in the fluoride matrix, and the fluoride matrix is selected from AReF ₄ or BaF ₂ ;

   Wherein, said A is selected from alkali metals;

   The Re is selected from one or more of Y, La, Gd and Lu;

   The rare earth doped ion Ln ^{3+ is} selected from one or more of ^{Pr 3+} , Sm ³⁺ , Dy ³⁺ , Ho ³⁺ , Er ³⁺ , Tb ³⁺ , Nd ³⁺ and Tm ^3+;

   The doping amount of the rare earth doped ions is 0.1-20 mol%;

   The afterglow time of the fluoride long afterglow particles after X-ray irradiation can be as high as 150 days.
2. The long afterglow particles according to claim 1, wherein the particle size of the long afterglow particles is adjustable from 10 nm to 150 μm.
3. The long afterglow particles according to claim 1, wherein the emission wavelength of the long afterglow particles is tunable from 350 to 1600 nm.
4. The long afterglow particle according to claim 1, further comprising a coating layer coated on the surface of the fluoride matrix, the coating layer is selected from fluoride, and the fluoride is selected from AReF ₄ or BaF ₂ ;

   Wherein, the A is selected from alkali metals, and the Re is selected from one or more of Lu, Y, Gd and La.
5. The long afterglow particles according to claim 1, wherein the long afterglow particles are selected from NaY _0.8 Gd _0.05 F ₄ : Tb _0.15 , NaLu _0.8 Gd _0.05 F ₄ : Tb _{0.15 , or NaLu 0.8} with a core-shell structure Gd _0.05 F ₄ : Tb _0.15 @NaYF ₄ .
6. A method for preparing long afterglow particles according to claim 1, characterized in that it comprises the following steps:

   A) Adding rare earth salt to the two-phase solvent of oleic acid and octadecene, stirring and mixing, and performing heating reaction under vacuum conditions to obtain a reaction liquid;

   B) Adding lye and ammonium fluoride to the reaction solution for preheating reaction, removing the solvent, and then performing heating reaction to obtain long afterglow particles.
7. The preparation method according to claim 6, characterized in that, in step A), the temperature of the heating reaction is 130-180°C, and the time is 10-30 min;

   In step B), the temperature of the preheating reaction is 30-60°C, and the time is 20-60 min;

   The heating reaction is to raise the temperature to 260-320°C at a rate of 10-30°C/min, and react for 0.5-2h.
8. A method for preparing long afterglow particles according to claim 1, characterized in that it comprises the following steps:

   After sodium citrate, rare earth salt, sodium fluoride and water are mixed and stirred, the hydrothermal reaction is carried out under airtight conditions to obtain long afterglow particles.
9. The preparation method according to claim 8, wherein the temperature of the hydrothermal reaction is 180-240°C, and the time is 2-24h.
10. An application of the rare earth-doped fluoride long afterglow particles as claimed in claim 1 in biomarking, X-ray detection, display and imaging.

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