Preparation method of up / down conversion paramagnetic fluoride rare earth nanoparticles

Abstract

The invention discloses a preparation method of up / down conversion paramagnetic fluoride rare earth nanoparticles, and belongs to the technical field of nano luminescent materials, the preparation method comprises the following steps: weighing 95-99 mmol of metal chloride GdCl3. 6H2O and 1-5 mmol of ErCl3. 6H2O, TbCl3. 6H2O or TmCl3. 6H2O, adding the metal chloride into ethylene glycol, and stirring until the mixture is transparent; the preparation method comprises the following steps: adding ethylene glycol into NH4F to obtain an NH4F solution, adding the NH4F solution into a metal chloride solution, stirring to obtain a precursor solution, transferring the precursor solution into a drying oven, heating, cooling to room temperature, centrifugally collecting a precipitate, and repeatedly centrifugally separating the precipitate to obtain a clear washing solution; the preparation method comprises the following steps: preparing a precursor solution, precipitating, drying in a drying box, annealing the powder in a high-temperature furnace, and cooling to obtain the product, and the product has excellent paramagnetic performance and is applied to the fields of biological imaging, magnetic resonance imaging (MRI) contrast agents, optical sensors, information storage and quantum dot display.

Description

Technical Field

[0001] The present invention belongs to the technical field of nano-luminescent materials, and particularly relates to a preparation method of up / down-conversion paramagnetic fluoride rare earth nanoparticles. Background Art

[0002] Rare earth elements have a wide range of applications in the fields of materials science, energy, information technology, and biomedicine due to their unique optical, electrical, and magnetic properties. Rare earth elements include lanthanide elements (La-Lu), as well as scandium (Sc) and yttrium (Y), a total of 17 elements. These elements have similar chemical properties, but the 4f orbital electron configurations of each rare earth element are different, giving them unique luminescent properties. The 4f-4f electronic transition of rare earth ions is an inter-band transition with narrow spectral linewidth, high emission intensity, and high quantum efficiency. These characteristics enable rare earth materials to show important application potential in the fields of laser technology, fluorescent lamps, display technology, fiber optic amplifiers, and biological imaging.

[0003] In recent years, rare earth doped nanoparticles (RENPs) have become a research hotspot, combining the excellent optical properties of rare earth ions and the unique size effect of nanomaterials. Nanoparticles doped with rare earth ions are suitable for fields such as biomedicine, display technology, optoelectronic sensors, and quantum information processing, and can exhibit up-conversion (UC) and down-conversion (DC) luminescent characteristics. In up-conversion luminescence, the nanoparticles absorb two or more low-energy photons and emit one high-energy photon; while in down-conversion luminescence, the nanoparticles absorb one high-energy photon and emit two or more low-energy photons. By regulating the doping concentration of rare earth ions, the type and morphology of the matrix material, and the preparation process parameters, the up / down-conversion luminescence efficiency can be optimized, and precise control of the emission spectrum can be achieved. However, traditional rare earth doped materials have the following problems: high temperature, high pressure, or harsh chemical conditions are required during the synthesis process, the process is complex and energy-consuming; the size and morphology of the particles are difficult to precisely control, which may lead to non-uniformity of luminescent properties; impurity introduction and matrix lattice defects may reduce the luminescence efficiency and affect the stability of the material. Rare earth fluoride materials (such as GdF3, NaYF4, LiLuF4, etc.) can effectively suppress the multi-phonon non-radiative transition of rare earth ions and significantly improve the luminescence efficiency due to their lattice characteristics of low phonon energy. In addition, their excellent chemical and optical stability makes them important materials for biomedical imaging, laser technology, and optical fiber communication. In these applications, rare earth doped GdF3 nanoparticles have attracted much attention due to their paramagnetic properties (magnetization phenomenon generated by an external magnetic field) and strong up-conversion luminescent characteristics. The paramagnetic properties enable the optical properties of this material to be regulated by an external magnetic field, providing the possibility for magneto-optical coupling devices and magnetic field modulated luminescence technology.

[0004] Currently, the technologies for preparing GdF3 rare earth nanoparticles mainly include the following: Coprecipitation method: By simultaneously adding rare earth ions and fluoride ions in a solution to form a precipitate, and then improving the crystal quality through high-temperature annealing. This method is simple and easy to implement, but the size distribution of the obtained particles is relatively wide and the morphology is difficult to control. Hydrothermal method: Utilize high-temperature and high-pressure conditions to promote crystal growth, usually carried out in a high-pressure autoclave lined with polytetrafluoroethylene. This method can obtain nanoparticles with high crystallinity and uniform morphology, but precise control of temperature and pressure is crucial during the operation process. Thermal decomposition method: Utilize the chemical decomposition reaction of organic ligands and rare earth salts to generate nanoparticles with controllable size and morphology. Although the prepared particles have small size and uniform distribution, the required organic ligands may bring toxicity or high-cost problems. Among the above methods, the hydrothermal method is widely adopted due to its mild reaction conditions and the superiority of high-crystalline products. However, to further improve the optical properties of the material, parameters such as the doping ratio of rare earth ions, the morphology and size distribution of particles need to be optimized. For example, too low doping concentration of rare earth ions may lead to insufficient light intensity, while too high concentration may trigger concentration quenching effect and reduce the luminescence efficiency. The existing preparation technologies have not fully solved problems such as precise control of particle morphology and further improvement of luminescence efficiency. Therefore, developing an economical, efficient and environmentally friendly preparation method and realizing systematic regulation of the properties of GdF3 nanoparticles is an important research direction at present. Summary of the Invention

[0005] Technical problems to be solved:

[0006] In view of the deficiencies of the prior art, this application solves the following technical problems in the prior art: high temperature, high pressure or harsh chemical conditions are required during the synthesis process, the process is complex and energy-consuming; the size and morphology of particles are difficult to precisely control, which may lead to non-uniformity of luminescence performance; the introduction of impurities and matrix lattice defects may reduce the luminescence efficiency and affect the stability of the material, organic ligands may bring toxicity or high cost, too low doping concentration of rare earth ions may lead to insufficient light intensity, while too high concentration may trigger concentration quenching effect and reduce the luminescence efficiency. This application provides a preparation method of up / down-conversion paramagnetic fluoride rare earth nanoparticles. Since Gd has a strong spin magnetic moment, using GdF3 as the matrix and introducing Er 3+ / Tb 3+ / Eu 3+ / Tm 3+ as the luminescent ion center, fluoride nanoparticles with regular morphology and uniform size can be prepared to achieve efficient fluorescence emission of up / down-conversion.

[0007] Technical solutions:

[0008] To achieve the above object, this application is realized through the following technical solutions:

[0009] A method for preparing up / down-conversion paramagnetic fluoride rare earth nanoparticles, specifically including the following steps:

[0010] First step: At room temperature, accurately weigh 95 - 99 mmol of GdCl3·6H2O and 1 - 5 mmol of ErCl3·6H2O, TbCl3·6H2O or TmCl3·6H2O of metal chloride using a clean and dry balance.

[0011] Second step: Take 10 mL of ethylene glycol, pour it into a beaker, ensure that the ethylene glycol is free of moisture, and add the weighed metal chloride into the ethylene glycol.

[0012] Third step: Place the beaker on a magnetic stirrer, put a magnetic stir bar into it, set the stirring speed to medium speed, and stir for 25 - 35 minutes until the solution becomes transparent and free of particles to obtain a metal chloride solution.

[0013] Fourth step: Weigh 4 mmol of NH4F, place it in a clean glass rod or beaker, pour 10 mL of ethylene glycol into another clean beaker, add NH4F, and stir with a glass rod until it is completely dissolved to obtain an NH4F solution.

[0014] Fifth step: Use a dropper to slowly add the NH4F solution drop by drop into the metal chloride solution, control the dropping speed at 1 - 2 drops per second, and keep stirring at a speed of 600 rpm vigorously during the dropping process.

[0015] Sixth step: After the dropping is completed, continue to stir at 600 rpm for 30 minutes to ensure that the two solutions are evenly mixed to form a stable precursor solution, observe the state of the solution to ensure that there is no precipitation or particle suspension.

[0016] Seventh step: Use a pipette to transfer the precursor solution into a polytetrafluoroethylene-lined autoclave, place the autoclave in an oven, set the temperature to 200 °C, and keep it warm for 3 hours to ensure complete internal reaction.

[0017] Eighth step: After the heating is completed, turn off the power of the oven, leave the autoclave in the oven to cool naturally to room temperature. After cooling, take out the autoclave with heat-resistant gloves.

[0018] Ninth step: Pour the cooled precursor solution into a centrifuge tube, set the centrifuge speed to 6000 rpm, and the time to 10 minutes. After centrifugation, collect the precipitate.

[0019] Tenth step: Add 25 mL of ethanol to the precipitate, gently stir with a pipette to suspend the precipitate, and repeat centrifugal separation 3 - 5 times until the washing liquid is clear and free of impurities.

[0020] The eleventh step: Transfer the washed precipitate to a drying dish or a petri dish, place it in a drying oven at 60 °C, and keep it dry for 12 hours to ensure complete removal of the residual solvent;

[0021] The twelfth step: Gently grind the dried powder, evenly spread it in a high-temperature-resistant ceramic crucible with a brush, ensure that the powder does not accumulate, place the crucible in a high-temperature furnace, raise the temperature by 5 °C per minute to the target temperature of 400 °C, and keep it at a constant temperature of 400 °C for 3 hours;

[0022] The thirteenth step: After the annealing is completed, turn off the high-temperature furnace and let the crucible cool naturally to room temperature. After the cooling is completed, take out the crucible with tweezers,

[0023] Carefully collect and store the annealed product, namely the up / down-conversion paramagnetic fluoride rare earth nanoparticles.

[0024] Furthermore, in the first step, the purity of both GdCl3·6H2O and ErCl3·6H2O is >99.9%.

[0025] Furthermore, in the second step, the purity of ethylene glycol is >99.9%.

[0026] Furthermore, in the third step, the stirring speed at medium speed is 600 rpm.

[0027] Furthermore, in the fourth step, the purity of NH4F is >99.9%.

[0028] Furthermore, in the tenth step, the repeated centrifugal separation specifically means dispersing the precipitate in 25 mL of ethanol, centrifuging at 6000 rpm for 10 minutes, and discarding the supernatant.

[0029] Beneficial effects:

[0030] The present application provides a preparation method of up / down-conversion paramagnetic fluoride rare earth nanoparticles. Compared with the prior art, it has the following beneficial effects:

[0031] 1. Using ethylene glycol as a green solvent avoids the use of toxic and harmful reagents in traditional preparation methods;

[0032] 2. The whole process is simple to operate, the process is mild, and the product yield is high, meeting the requirements of modern material preparation for greenness and high efficiency;

[0033] 3. By carrying out the hydrothermal reaction in a polytetrafluoroethylene-lined autoclave, this process promotes the gradual nucleation and growth of crystals under mild conditions, avoiding the problems of particle aggregation or irregular morphology that may occur in traditional methods, thereby preparing paramagnetic fluoride nanoparticles with high crystallinity and monodispersity;

[0034] 4. By performing annealing treatment, the crystal structure and surface properties of the particles are improved; the process of slowly raising the temperature avoids structural damage caused by crystal thermal shock, and the optimization of the annealing temperature improves the optical properties of the rare earth doped nanoparticles, especially the up / down conversion luminescence intensity and efficiency;

[0035] 5. The prepared paramagnetic fluoride rare earth nanoparticles have excellent paramagnetic properties and can be applied to fields such as bioimaging, magnetic resonance imaging (MRI) contrast agents, optical sensors, information storage, and quantum dot displays;

[0036] 6. The structural stability and controllability of the up / down conversion paramagnetic fluoride rare earth nanoparticles prepared in this application lay a good foundation for the development of multifunctional composite materials and further enhance their application value in high-performance materials. Brief Description of the Drawings

[0037] Figure 1 These are the TEM and HRTEM images of the up / down conversion paramagnetic fluoride rare earth nanoparticles prepared by the hydrothermal method in Example 1 of this application. The left figure is the TEM image of the up / down conversion paramagnetic fluoride rare earth nanoparticles; the right figure is the HRTEM image of the up / down conversion paramagnetic fluoride rare earth nanoparticles;

[0038] Figure 2 These are the EDS element mapping distribution diagrams of the up / down conversion paramagnetic fluoride rare earth nanoparticles in Example 1 of this application. The upper left corner is the spatial overlap diagram of the three elements F, Er, and Gd in the rare earth nanoparticles; the upper right corner is the spatial distribution diagram of the Gd element in the rare earth nanoparticles; the lower left corner is the spatial distribution diagram of the F element in the rare earth nanoparticles; the lower right corner is the spatial distribution diagram of the Er element in the rare earth nanoparticles;

[0039] Figure 3 These are the XRD curve diagrams of the up / down conversion paramagnetic fluoride rare earth nanoparticles in Example 1 of this application;

[0040] Figure 4 These are the curve diagrams of the relationship between the magnetization intensity (M) and the applied magnetic field intensity (H) of the up / down conversion paramagnetic fluoride rare earth nanoparticles in Example 1 of this application;

[0041] Figure 5 These are the up / down conversion paramagnetic fluoride GdF3:Er 3+ ultraviolet absorption spectrum diagrams of the nanoparticles;

[0042] Figure 6 These are the up / down conversion paramagnetic fluoride GdF3:Er 3+Up / down-conversion emission spectra of the nanoparticles excited at 808 nm and 527 nm, where the upper figure is the up / down-conversion emission spectrum excited at 808 nm and the lower figure is the up / down-conversion emission spectrum excited at 527 nm;

[0043] Figure 7 This is for GdF3:1% Er in Example 2 of this application 3+ and 5% Er 3+ Up-conversion emission spectrum of the nanoparticles excited at 808 nm;

[0044] Figure 8 This is for GdF3:Tb in Example 3 of this application 3+ Up-conversion emission spectrum of the nanoparticles excited at 808 nm;

[0045] Figure 9 This is for GdF3:Eu in Example 4 of this application 3+ Down-conversion emission spectrum of the nanoparticles excited at 527 nm;

[0046] Figure 10 This is for GdF3:Tm in Example 5 of this application 3+ Up-conversion emission spectrum of the nanoparticles excited at 808 nm. Detailed implementation manners

[0047] In order to more clearly elaborate the purpose, technical solutions and their advantages of the present invention, the following will be described through specific examples. However, these examples are only used to explain the present invention and do not constitute any limitation to its patent scope. Without departing from the spirit and basic principles of the present invention, any modification, substitution or improvement should be regarded as a reasonable extension of the present invention and covered by its patent protection scope.

[0048] Example 1:

[0049] A preparation method of up / down-conversion paramagnetic rare-earth fluoride nanoparticles GdF3:Er 3+ is specifically as follows:

[0050] The first step: At room temperature, use a clean and dry balance to accurately weigh 99 mmol of GdCl3·6H2O and 1 mmol of ErCl3·6H2O of metal chlorides, avoiding contamination by impurities or moisture; the purity of both GdCl3·6H2O and ErCl3·6H2O is >99.9%;

[0051] The second step: Take 10 mL of ethylene glycol, pour it into a beaker, ensure that the ethylene glycol has no moisture, and add the weighed metal chlorides to the ethylene glycol, avoiding powder scattering; the purity of the ethylene glycol is >99.9%;

[0052] Step 3: Place the beaker on a magnetic stirrer, add a magnetic stir bar, set the stirring speed to 600 rpm, and stir for 30

[0053] minutes until a transparent and homogeneous solution is formed. Ensure that there are no particle residues in the solution to avoid uneven subsequent reactions due to incomplete dissolution, and obtain a metal chloride solution;

[0054] Step 4: Weigh 4 mmol of NH4F, place it in a clean glass rod or beaker to avoid moisture absorption. Pour 10 mL of ethylene glycol into another clean beaker. After adding NH4F, stir with a glass rod until it completely dissolves to obtain an NH4F solution; the purity of NH4F > 99.9%;

[0055] Step 5: Dropwise add the NH4F solution to the metal chloride solution using a dropper, control the dropping speed at 1 - 2 drops per second, and keep stirring vigorously at 600 rpm during the dropping process to avoid local reactions causing precipitation lumps;

[0056] Step 6: After the addition is complete, continue to stir at 600 rpm for 30 minutes to ensure that the two solutions are evenly mixed to form a stable precursor solution. Observe the solution state to ensure that there is no precipitation or particle suspension;

[0057] Step 7: Transfer the precursor solution to a Teflon - lined autoclave using a pipette, ensure that the autoclave is well - sealed to prevent solution leakage. Place the autoclave in an oven, set the temperature to 200 °C, and keep it at this temperature for 3 hours to ensure complete internal reaction;

[0058] Step 8: After heating is completed, turn off the power of the oven, leave the autoclave in the oven to cool naturally to room temperature. After cooling, remove the autoclave with heat - resistant gloves and gently open it to avoid a sudden drop in pressure;

[0059] Step 9: Pour the cooled precursor solution into a centrifuge tube, ensure that the liquid and solid are completely transferred. Set the centrifuge speed to 6000 rpm and the time to 10 minutes. After centrifugation, collect the precipitate and carefully pour off the supernatant to avoid losing the precipitate;

[0060] Step 10: Add 25 mL of ethanol to the precipitate, gently stir with a pipette to suspend the precipitate, and repeat the centrifugation and separation 3 - 5 times to remove unreacted precursors and other impurities until the washing liquid is clear and free of impurities;

[0061] Step 11: Transfer the washed precipitate to a drying dish or petri dish, place it in a drying oven at 60 °C, and keep it dry for 12 hours to ensure complete removal of residual solvents;

[0062] Step 12: The dried GdF3:Er 3+The nano-powder is gently ground and evenly spread in a high-temperature resistant ceramic crucible with a brush to ensure that the powder does not accumulate, so as to be heated evenly during the annealing process. Place the crucible in a high-temperature furnace and heat it at a rate of 5 °C per minute to the target temperature of 400 °C, and keep it at a constant temperature of 400 °C for 3 hours. Avoid opening the high-temperature furnace or removing the crucible.

[0063] Step 13: After annealing is completed, turn off the high-temperature furnace and let the crucible cool naturally to room temperature. After cooling is completed, use tweezers to take out the crucible, and carefully collect and store the annealed product, namely the up / down-conversion paramagnetic GdF3:Er 3+ rare earth nanoparticles.

[0064] For the nanoparticles obtained through the above steps, the transmission electron microscope (TEM) images show that the obtained GdF3:Er 3+ nanoparticles are evenly dispersed in the matrix, presenting a regular rod-like morphology, with uniform particle size and smooth surface, as Figure 1 shown. High-resolution transmission electron microscope (HRTEM) further reveals clear lattice fringes, indicating its highly crystalline characteristics. To verify the chemical composition of the GdF3:Er 3+ nanoparticles, elemental analysis is carried out using X-ray photoelectron spectroscopy. The XPS spectrum clearly reveals the characteristic peaks of Gd, Er, and F, and the distribution of each element is uniform. No other impurity peaks are observed, indicating the high purity and doping uniformity of the material, as Figure 2 shown. The crystal phase structure of the sample is analyzed by X-ray diffraction test, as Figure 3 shown. All the main diffraction peaks can match the diffraction pattern of standard GdF3, indicating that the material belongs to the orthorhombic crystal system and is highly consistent with the standard structure of the Pnma space group. To study the magnetic behavior of the sample, the magnetization curve is measured at room temperature using a vibrating sample magnetometer (VSM), as Figure 4 shown. The results show that the magnetization intensity of the GdF3:Er 3+ nanoparticles increases linearly with the increase of the applied magnetic field, indicating its typical paramagnetism. This property is mainly attributed to the unpaired electron spin magnetic moment contributed by Gd 3+ ions (4f 7 electronic configuration). To study the optical properties of the GdF3:Er 3+ nanoparticles, first, the absorption spectrum of the sample is measured using a UV-Vis spectrophotometer, as Figure 5 shown. Subsequently, under the excitation of an 808 nm near-infrared laser and a 527 nm green laser, the emission spectrum is measured using a fluorescence spectrometer, as Figure 6 shown. The experimental results show that the sample can achieve effective up-conversion and down-conversion luminescence.

[0065] Example 2:

[0066] A method for preparing up / down-conversion paramagnetic fluoride rare earth nanoparticles, specifically including the following steps:

[0067] First step: At room temperature, use a clean and dry balance to accurately weigh 95 mmol of GdCl3·6H2O and 5 mmol of ErCl3·6H2O of metal chloride, avoiding contamination by impurities or moisture; the purity of both GdCl3·6H2O and ErCl3·6H2O is >99.9%;

[0068] Second step: Take 10 mL of ethylene glycol, pour it into a beaker, ensure that the ethylene glycol has no moisture, add the weighed metal chloride to the ethylene glycol, avoiding powder scattering; the purity of the ethylene glycol is >99.9%;

[0069] Third step: Place the beaker on a magnetic stirrer, put a magnetic stir bar, set the stirring speed to 600 rpm, and stir for 30

[0070] minutes until a transparent and homogeneous solution is formed, ensuring that there are no particle residues in the solution and avoiding uneven subsequent reactions due to incomplete dissolution, to obtain a metal chloride solution;

[0071] Fourth step: Weigh 4 mmol of NH4F, place it in a clean glass rod or beaker to avoid moisture absorption, pour 10 mL of ethylene glycol into another clean beaker, add NH4F, and stir with a glass rod until it is completely dissolved to obtain an NH4F solution; the purity of NH4F is >99.9%;

[0072] Fifth step: Use a dropper to slowly add the NH4F solution drop by drop to the metal chloride solution, control the dropping speed at 1 - 2 drops per second, and keep stirring at a speed of 600 rpm during the dropping process to avoid local reactions causing precipitation blocks;

[0073] Sixth step: After the dropping is completed, continue to stir at 600 rpm for 30 minutes to ensure that the two solutions are evenly mixed to form a stable precursor solution, observe the state of the solution, and ensure that there is no precipitation or particle suspension;

[0074] Seventh step: Use a pipette to transfer the precursor solution to a polytetrafluoroethylene-lined autoclave, ensure that the autoclave is sealed properly to prevent solution leakage, place the autoclave in an oven, set the temperature to 200 °C, and keep it warm for 3 hours to ensure complete internal reaction;

[0075] Eighth step: After heating is completed, turn off the power of the oven, leave the autoclave in the oven to cool naturally to room temperature. After cooling, take out the autoclave with heat-resistant gloves and gently open it to avoid a sudden drop in pressure;

[0076] Step 9: Pour the cooled precursor solution into a centrifuge tube, ensure that the liquid and solid are completely transferred, set the centrifuge speed to 6000 rpm and the time to 10 minutes. After centrifugation, collect the precipitate and carefully pour off the supernatant, avoiding loss of the precipitate.

[0077] Step 10: Add 25 mL of ethanol to the precipitate, gently stir with a pipette to suspend the precipitate, and repeat centrifugal separation 3 - 5 times to remove unreacted precursors and other impurities until the washing liquid is clear and free of impurities.

[0078] Step 11: Transfer the washed precipitate to a drying dish or petri dish, place it in an oven at 60 °C, and keep it dry for 12 hours to ensure complete removal of residual solvent.

[0079] Step 12: Gently grind the dried GdF3:Er 3+ nano - powder, evenly spread it in a high - temperature - resistant ceramic crucible with a brush, ensure that the powder does not accumulate, so as to be heated evenly during the annealing process. Place the crucible in a high - temperature furnace, raise the temperature by 5 °C per minute to the target temperature of 400 °C, and keep it at 400 °C for 3 hours. Avoid opening the high - temperature furnace or removing the crucible.

[0080] Step 13: After annealing is completed, turn off the high - temperature furnace and let the crucible cool naturally to room temperature. After cooling, use tweezers to take out the crucible, carefully collect and store the annealed product, namely the up / down - conversion paramagnetic GdF3:Er 3+ rare - earth nanoparticles.

[0081] To characterize the optical properties of the up / down - conversion paramagnetic GdF3:Er 3+ nanoparticles, the emission spectrum was measured using a spectrometer under 808 nm laser excitation, and it was compared with the emission spectrum of 1% concentration GdF3:Er 3+ nanoparticles, as Figure 7 shown.

[0082] Example 3:

[0083] A preparation method of up / down - conversion paramagnetic fluoride rare - earth nanoparticles GdF3:Tb 3+ specifically includes the following steps:

[0084] Step 1: At room temperature, use a clean and dry balance to accurately weigh 99 mmol of GdCl3·6H2O and 1 mmol of TbCl3·6H2O of metal chlorides, avoiding contamination by impurities or moisture; the purity of both GdCl3·6H2O and TbCl3·6H2O is > 99.9%.

[0085] Step 2: Take 10 mL of ethylene glycol, pour it into a beaker, ensure that the ethylene glycol is free of moisture, add the weighed metal chloride to the ethylene glycol, and avoid powder scattering; the purity of the ethylene glycol > 99.9%;

[0086] Step 3: Place the beaker on a magnetic stirrer, put in a magnetic stir bar, set the stirring speed to 600 rpm, and stir for 30 minutes until a transparent homogeneous solution is formed, ensure that there are no particle residues in the solution, and avoid uneven subsequent reactions caused by incomplete dissolution to obtain a metal chloride solution;

[0087] Step 4: Weigh 4 mmol of NH4F, place it in a clean glass rod or beaker to avoid moisture absorption, pour 10 mL of ethylene glycol into another clean beaker, after adding NH4F, stir with a glass rod until it is completely dissolved to obtain an NH4F solution; the purity of NH4F > 99.9%;

[0088] Step 5: Use a dropper to slowly add the NH4F solution drop by drop to the metal chloride solution, control the dropping speed at 1 - 2 drops per second, and keep stirring vigorously at 600 rpm during the dropping process to avoid local reactions causing precipitation blocks;

[0089] Step 6: After the dropping is completed, continue to stir at 600 rpm for 30 minutes to ensure that the two solutions are evenly mixed to form a stable precursor solution, observe the solution state to ensure that there is no precipitation or particle suspension;

[0090] Step 7: Use a pipette to transfer the precursor solution to a polytetrafluoroethylene-lined autoclave, ensure that the autoclave is sealed properly to prevent solution leakage, place the autoclave in an oven, set the temperature to 200 °C, and keep it warm for 3 hours to ensure complete internal reaction;

[0091] Step 8: After the heating is completed, turn off the power of the oven, leave the autoclave in the oven to cool naturally to room temperature, after cooling, use heat-resistant gloves to take out the autoclave and gently open it to avoid a sudden drop in pressure;

[0092] Step 9: Pour the cooled precursor solution into a centrifuge tube, ensure that the liquid and solid are completely transferred, set the centrifuge speed to 6000 rpm, and the time to 10 minutes. After centrifugation, collect the precipitate and carefully pour out the supernatant to avoid losing the precipitate;

[0093] Step 10: Add 25 mL of ethanol to the precipitate, gently stir with a pipette to suspend the precipitate, repeat the centrifugation separation 3 - 5 times to remove unreacted precursors and other impurities until the washing liquid is clear and free of impurities;

[0094] Step 11: Transfer the washed precipitate to a drying dish or petri dish, place it in a drying oven at 60 °C, and keep it dry for 12 hours to ensure complete removal of residual solvents;

[0095] Step 12: The dried GdF3:Er 3+ nanopowder was gently ground and evenly spread in a high-temperature resistant ceramic crucible with a brush, ensuring that the powder did not accumulate so as to be heated evenly during the annealing process. The crucible was placed in a high-temperature furnace and heated at a rate of 5 °C per minute to the target temperature of 400 °C, and held at 400 °C for 3 hours, avoiding opening the high-temperature furnace or removing the crucible;

[0096] Step 13: After the annealing was completed, the high-temperature furnace was turned off and the crucible was allowed to cool naturally to room temperature. After cooling was completed, the crucible was taken out with tweezers, and the annealed product, i.e., the up / down-conversion paramagnetic GdF3:Tb 3+ rare earth nanoparticles, was carefully collected and stored.

[0097] To characterize the optical properties of the up / down-conversion paramagnetic GdF3:Tb 3+ nanoparticles, the emission spectrum was measured using a spectrometer under 808 nm laser excitation subsequently. The results showed that the sample could achieve efficient up-conversion luminescence.

[0098] Example 4:

[0099] A preparation method of up / down-conversion paramagnetic rare earth fluoride nanoparticles GdF3:Eu 3+ is as follows:

[0100] Step 1: At room temperature, 99 mmol of GdCl3·6H2O and 1 mmol of EuCl3·6H2O of metal chlorides were accurately weighed using a clean and dry balance, avoiding contamination by impurities or moisture; the purity of both GdCl3·6H2O and EuCl3·6H2O was >99.9%;

[0101] Step 2: Take 10 mL of ethylene glycol, pour it into a beaker, ensure that the ethylene glycol is free of moisture, and add the weighed metal chlorides to the ethylene glycol, avoiding powder scattering; the purity of the ethylene glycol was >99.9%;

[0102] Step 3: Place the beaker on a magnetic stirrer, put a magnetic stir bar in it, set the stirring speed to 600 rpm, and stir for 30

[0103] minutes until a transparent and homogeneous solution was formed, ensuring that there were no particles remaining in the solution to avoid uneven subsequent reactions due to incomplete dissolution, and a metal chloride solution was obtained;

[0104] Step 4: Weigh 4 mmol of NH4F, place it in a clean glass rod or beaker to avoid moisture absorption. Pour 10 mL of ethylene glycol into another clean beaker, add NH4F, and stir with a glass rod until it was completely dissolved to obtain an NH4F solution; the purity of NH4F was >99.9%;

[0105] Step 5: Dropwise add the NH4F solution to the metal chloride solution using a dropper, controlling the dropping speed at 1 - 2 drops per second. During the dropping process, maintain a strong stirring speed of 600 rpm to avoid the formation of precipitate lumps due to local reactions.

[0106] Step 6: After the addition is complete, continue stirring at 600 rpm for 30 minutes to ensure the uniform mixing of the two solutions to form a stable precursor solution. Observe the state of the solution to ensure that there is no precipitate or particle suspension.

[0107] Step 7: Transfer the precursor solution to a polytetrafluoroethylene-lined autoclave using a pipette, ensuring that the autoclave is well-sealed to prevent solution leakage. Place the autoclave in an oven, set the temperature to 200 °C, and keep it at this temperature for 3 hours to ensure complete internal reaction.

[0108] Step 8: After heating is completed, turn off the power of the oven and leave the autoclave in the oven to cool naturally to room temperature. After cooling, remove the autoclave with heat-resistant gloves and gently open it to avoid a sudden drop in pressure.

[0109] Step 9: Pour the cooled precursor solution into a centrifuge tube, ensuring complete transfer of the liquid and solid. Set the centrifuge speed to 6000 rpm and the time to 10 minutes. After centrifugation, collect the precipitate and carefully pour off the supernatant to avoid loss of the precipitate.

[0110] Step 10: Add 25 mL of ethanol to the precipitate and gently stir with a pipette to suspend the precipitate. Repeat the centrifugation and separation 3 - 5 times to remove unreacted precursors and other impurities until the washing liquid is clear and free of impurities.

[0111] Step 11: Transfer the washed precipitate to a drying dish or petri dish and place it in a drying oven at 60 °C for 12 hours to ensure complete removal of residual solvent.

[0112] Step 12: Gently grind the dried GdF3:Er 3+ nano powder and evenly spread it in a high-temperature resistant ceramic crucible with a brush, ensuring that the powder does not accumulate for uniform heating during the annealing process. Place the crucible in a high-temperature furnace and increase the temperature by 5 °C per minute to the target temperature of 400 °C, and maintain a constant temperature of 400 °C for 3 hours, avoiding opening the high-temperature furnace or removing the crucible.

[0113] Step 13: After annealing is completed, turn off the high-temperature furnace and let the crucible cool naturally to room temperature. After cooling, remove the crucible with tweezers and carefully collect and store the annealed product, namely the up / down-conversion paramagnetic GdF3:Eu 3+ rare earth nanoparticles.

[0114] In order to characterize the down-conversion paramagnetic GdF3:Eu 3+The optical properties of the nanoparticles were then measured by a spectrometer under the excitation of a 527 nm laser. The results showed that the sample could achieve efficient down-conversion luminescence.

[0115] Example 5:

[0116] A preparation method of up / down-conversion paramagnetic fluoride rare earth nanoparticles GdF3:Tm 3+ comprises the following steps:

[0117] First step: At room temperature, accurately weigh 99 mmol of GdCl3·6H2O and 1 mmol of TmCl3·6H2O of metal chloride using a clean and dry balance to avoid contamination by impurities or moisture; the purity of both GdCl3·6H2O and TmCl3·6H2O is >99.9%;

[0118] Second step: Take 10 mL of ethylene glycol, pour it into a beaker, ensure that the ethylene glycol is free of moisture, and add the weighed metal chloride into the ethylene glycol to avoid powder scattering; the purity of the ethylene glycol is >99.9%;

[0119] Third step: Place the beaker on a magnetic stirrer, put a magnetic stir bar into it, set the stirring speed to 600 rpm, and stir for 30

[0120] minutes until a transparent and homogeneous solution is formed, ensure that there are no particle residues in the solution, and avoid uneven subsequent reactions caused by incomplete dissolution to obtain a metal chloride solution;

[0121] Fourth step: Weigh 4 mmol of NH4F, place it in a clean glass rod or beaker to avoid moisture absorption, pour 10 mL of ethylene glycol into another clean beaker, add NH4F, and stir with a glass rod until it is completely dissolved to obtain an NH4F solution; the purity of NH4F is >99.9%;

[0122] Fifth step: Use a dropper to slowly add the NH4F solution drop by drop to the metal chloride solution, control the dropping speed at 1-2 drops per second, and keep stirring at a speed of 600 rpm during the dropping process to avoid local reactions causing precipitation blocks;

[0123] Sixth step: After the dropping is completed, continue to stir at 600 rpm for 30 minutes to ensure that the two solutions are evenly mixed to form a stable precursor solution, observe the solution state, and ensure that there is no precipitation or particle suspension;

[0124] Seventh step: Use a pipette to transfer the precursor solution to a polytetrafluoroethylene-lined autoclave, ensure that the autoclave is sealed properly to prevent solution leakage, place the autoclave in an oven, set the temperature to 200 °C, and keep it warm for 3 hours to ensure complete internal reaction;

[0125] Step 8: After heating is completed, turn off the power of the oven, leave the autoclave in the oven to cool naturally to room temperature. After cooling, use heat-resistant gloves to take out the autoclave and gently open it to avoid a sudden drop in pressure;

[0126] Step 9: Pour the cooled precursor solution into a centrifuge tube, ensure that the liquid and solid are completely transferred, set the centrifuge speed to 6000 rpm and the time to 10 minutes. After centrifugation, collect the precipitate and carefully pour out the supernatant to avoid loss of the precipitate;

[0127] Step 10: Add 25 mL of ethanol to the precipitate, gently stir with a pipette to suspend the precipitate, and repeat centrifugal separation 3 - 5 times to remove unreacted precursors and other impurities until the washing liquid is clear and free of impurities;

[0128] Step 11: Transfer the washed precipitate to a drying dish or petri dish, place it in a drying oven at 60 °C, and keep it dry for 12 hours to ensure complete removal of residual solvents;

[0129] Step 12: The dried GdF3:Er 3+ nanopowder is gently ground and evenly spread in a high-temperature resistant ceramic crucible with a brush, ensuring that the powder does not accumulate so as to be uniformly heated during the annealing process. Place the crucible in a high-temperature furnace and raise the temperature by 5 °C per minute to the target temperature of 400 °C, and keep it at 400 °C for 3 hours without opening the high-temperature furnace or removing the crucible;

[0130] Step 13: After annealing is completed, turn off the high-temperature furnace and let the crucible cool naturally to room temperature. After cooling is completed, use tweezers to take out the crucible, carefully collect and store the annealed product, namely the up / down-conversion paramagnetic GdF3:Tm 3+ rare earth nanoparticles.

[0131] To characterize the optical properties of the down-conversion paramagnetic GdF3:Tm 3+ nanoparticles, the emission spectrum was measured using a spectrometer under 808 nm laser excitation. The results show that the sample can achieve efficient up-conversion luminescence.

[0132] The above has given an exemplary description of the present invention. It should be noted that without departing from the core of the present invention, any simple deformation, modification or equivalent substitution that can be made by those skilled in the art without creative labor falls within the protection scope of the present invention.

Claims

1. A method for preparing up / down-conversion paramagnetic fluoride rare earth nanoparticles, characterized in that, Specifically, it includes the following steps: Step 1: At room temperature, accurately weigh 95 - 99 mmol of GdCl3·6H2O and 1 - 5 mmol of ErCl3·6H2O, TbCl3·6H2O or TmCl3·6H2O of metal chloride using a clean and dry balance; Step 2: Take 10 mL of ethylene glycol, pour it into a beaker, ensure that the ethylene glycol is free of moisture, and add the weighed metal chloride into the ethylene glycol; Step 3: Place the beaker on a magnetic stirrer, put a magnetic stir bar into it, set the stirring speed to medium speed, stir for 25 - 35 minutes until the solution becomes transparent and free of particles, obtaining a metal chloride solution; Step 4: Weigh 4 mmol of NH4F, place it in a clean glass rod or beaker, pour 10 mL of ethylene glycol into another clean beaker, after adding NH4F, stir with a glass rod until it completely dissolves to obtain an NH4F solution; Step 5: Use a dropper to slowly drop the NH4F solution into the metal chloride solution, control the dropping speed at 1 - 2 drops per second, and keep stirring at a speed of 600 rpm vigorously during the dropping process; Step 6: After the dropping is completed, continue to stir at 600 rpm for 30 minutes to ensure that the two solutions are evenly mixed to form a stable precursor solution, observe the state of the solution to ensure that there is no precipitation or particle suspension; Step 7: Use a pipette to transfer the precursor solution into a polytetrafluoroethylene-lined autoclave, place the autoclave in an oven, set the temperature to 200 °C, and keep it warm for 3 hours to ensure complete internal reaction; Step 8: After heating is completed, turn off the power of the oven, leave the autoclave in the oven to cool naturally to room temperature, after cooling, take out the autoclave with heat-resistant gloves; Step 9: Pour the cooled precursor solution into a centrifuge tube, set the centrifuge speed to 6000 rpm, and the time to 10 minutes, Collect the precipitate after centrifugation; Step 10: Add 25 mL of ethanol to the precipitate, gently stir with a pipette to suspend the precipitate, repeat centrifugal separation 3 - 5 times, Until the washing liquid is clear and free of impurities; Step 11: Transfer the washed precipitate to a drying dish or petri dish, place it in a drying oven at 60 °C, and keep it dry for 12 hours to ensure complete removal of the residual solvent; Step 12: Gently grind the dried powder, evenly spread it in a high-temperature resistant ceramic crucible with a brush to ensure that the powder does not accumulate, Place the crucible in a high-temperature furnace, raise the temperature by 5 °C per minute to the target temperature of 400 °C, and keep it at 400 °C for 3 hours; Step 13: After annealing is completed, turn off the high-temperature furnace, let the crucible cool naturally to room temperature, after cooling is completed, take out the crucible with tweezers, carefully collect and store the annealed product, namely the up / down conversion paramagnetic fluoride rare earth nanoparticles.

2. The preparation method of the up / down-conversion paramagnetic fluoride rare earth nanoparticles according to claim 1, characterized in that, In the first step, the purity of both GdCl3·6H2O and ErCl3·6H2O is > 99.9%.

3. The preparation method of the up / down-conversion paramagnetic fluoride rare earth nanoparticles according to claim 1, characterized in that: In the second step, the purity of ethylene glycol is > 99.9%.

4. The preparation method of the up / down-conversion paramagnetic fluoride rare earth nanoparticles according to claim 1, wherein: In the third step, the medium stirring speed is 600 rpm.

5. The preparation method of the up / down-conversion paramagnetic fluoride rare earth nanoparticles according to claim 1, characterized in that: In the fourth step, the purity of NH4F is > 99.9%.

6. The method for preparing the up / down-conversion paramagnetic fluoride rare earth nanoparticles according to claim 1, wherein: In the tenth step, the repeated centrifugal separation specifically means dispersing the precipitate into 25 mL of ethanol, centrifuging at 6000 rpm for 10 minutes, and discarding the supernatant.

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