Rare earth nano luminescent probe with core-shell structure as well as preparation method and application of rare earth nano luminescent probe
The synthesis of core-shell structure rare earth nanoluminescent probes through high-temperature thermal decomposition of thermal injection cores has solved the problem of insufficient luminescence performance of core-shell nanoparticles, achieved significant improvement in luminescence intensity and enhanced structural stability, and is suitable for a variety of application scenarios.
Patent Information
- Application Number
- CN202510486781.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-18
- Publication Date
- 2025-07-18
AI Technical Summary
The core-shell structure rare earth nanoparticles synthesized by the prior art have problems with reduced luminescence intensity and quantum efficiency caused by fluorescence quenching, especially in small-sized nanomaterials with obvious impact on the surface quenching center.
The core-shell structure rare earth nanoluminescent probe was synthesized by the high-temperature thermal decomposition method of thermal injection core. By injecting the core particle solution into the high-temperature reaction solution, the core dissolution and ion mixing were inhibited, the doped ion distribution of core-shell nanoparticles was optimized, and an inert shell layer was formed to protect the luminescence center.
It improves the structural stability and luminous performance of nanoprobes, significantly enhances the luminous intensity, and has a wide range of applicability. It is suitable for high-resolution bioimaging, small-scale temperature sensing, photothermal therapy and metal ion or specific biomolecule detection.
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Figure CN120329946A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of luminescent probes, and in particular to a core-shell structured rare earth nano-luminescent probe and its preparation method and application. Background Art
[0002] The f-f transitions of rare earth ions have characteristics such as line spectra, little influence by temperature and matrix, small concentration and temperature quenching effects, etc. The advantages of rare earth luminescent nanomaterials doped with lanthanide ions include large Stokes shifts, rich energy level structures, rich emission bands and almost unchanged positions; fluorescence lifetimes ranging from nanoseconds to milliseconds, spanning 6 orders of magnitude; stable physical and chemical properties, etc. Rare earth nanomaterials are widely used in the field of luminescent probes.
[0003] The luminescence centers of rare earth luminescent nanomaterials mainly consist of sensitizers (such as Yb 3+ and Nd 3+ ) and activators (such as Er 3+ , Tm 3+ and Eu 3+ , etc.), where the sensitizer absorbs incident light and transfers the energy to the activator to generate luminescence. However, for small-sized nano-luminescent materials, their large specific surface areas may have more quenching centers (such as surface defects, surface oscillators, etc.). When the luminescence centers are directly exposed to the solution, the absorbed energy will be directly transferred to quenching centers such as solvent molecules on the surface, resulting in fluorescence quenching. The core-shell structure with an inert shell layer is still considered the most effective method to improve its luminescence performance, because the inert shell layer can maintain the optical integrity of the luminescence centers and effectively reduce the emission loss caused by the surface quenching effect. The methods for synthesizing core-shell structured rare earth nanoparticles include synthesizing core particles using the solvothermal method or the high-temperature thermal decomposition method, and synthesizing core-shell nanoparticles using the high-temperature thermal decomposition method, that is, heating the core particles and the shell precursor together in a solution to the reaction temperature to synthesize core-shell nanoparticles. However, the core-shell nanoparticles synthesized by this method still have the risk of reduced luminescence intensity and quantum efficiency due to fluorescence quenching, and the luminescence performance of the nanoparticles still needs to be further improved. Summary of the Invention
[0004] The purpose of the present invention is to provide a core-shell structured rare earth nano-luminescent probe and its preparation method and application to improve the luminescence performance of the luminescent probe.
[0005] The purpose of the present invention can be achieved by the following technical solutions: A core-shell structured rare earth nano-luminescent probe, comprising a core and one or more shell layers coated on the core, the core structure is AREF4, and the shell layer structure is AREF4 or CaF2, where A is selected from one or more of alkali metals, and RE is a rare earth element;
[0006] The core-shell structured rare earth nano-luminescent probe is synthesized by a thermal injection core high-temperature thermal decomposition method.
[0007] In the present invention, the nano-probe is a nano-particle having a core and a shell layer, the shell layer is one or more layers, the shell layer coats the core, the core is synthesized by a solvothermal method or a high-temperature thermal decomposition method, and the core-shell nano-particle is synthesized by a thermal injection core high-temperature thermal decomposition method.
[0008] The thermal injection core high-temperature thermal decomposition method refers to injecting a core particle solution into a high-temperature reaction solution of a shell precursor to synthesize a nano-particle having a core and a shell layer.
[0009] Preferably, the alkali metal is selected from one or more of Li, Na, and K.
[0010] Preferably, the rare earth element is selected from one or more of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
[0011] Preferably, each shell layer of the core-shell structured rare earth nano-luminescent probe is the same as or different from the core or the previous shell layer.
[0012] Preferably, the nano-luminescent probe has a hexagonal phase or cubic phase structure.
[0013] Preferably, the particle size of the core is 3-50 nm, and the shell layer thickness is 0.1-20 nm.
[0014] Preferably, the core is synthesized by a solvothermal method or a high-temperature thermal decomposition method.
[0015] In the present invention, by the above method, the core particles can be synthesized simply and quickly.
[0016] Preferably, the solvothermal method for preparing the core includes the following steps: adding a rare earth salt to a solvent, heating at 100-150 °C for 10 minutes to 2 hours, and adding an alkali metal compound and ammonium fluoride during this process; then, heating at 220-320 °C for 5 minutes to 4 hours in a protective atmosphere, adding ethanol and / or cyclohexane after cooling, centrifuging to collect the precipitate, and dispersing it in octadecene to obtain a core nano-particle dispersion.
[0017] More preferably, ethanol and cyclohexane are added after cooling.
[0018] More preferably, the rare earth salt is selected from one or more of rare earth chlorides, rare earth nitrates, and rare earth acetates.
[0019] More preferably, the alkali metal compound is an alkali metal hydroxide or an alkali metal oleate.
[0020] More preferably, the solvent is selected from oleic acid, linoleic acid, ricinoleic acid, stearic acid, oleylamine, and 1-octadecene.
[0021] More preferably, the solvothermal method for preparing the core specifically includes the following steps: adding a rare earth salt into a solvent, performing a first heating under evacuation, adding an alkali metal compound and ammonium fluoride during the first heating, performing a second heating under a protective atmosphere, adding ethanol and / or cyclohexane after cooling, collecting the precipitate by centrifugation, and dispersing it in 1-octadecene; the temperature of the first heating is 100-150 °C, and the time is 10 minutes to 2 hours; the temperature of the second heating is 220-320 °C, and the time is 5 minutes to 4 hours.
[0022] Even more preferably, the solvothermal method for preparing the core specifically includes the following steps: adding a rare earth chloride or rare earth nitrate or rare earth acetate into a solvent selected from oleic acid, linoleic acid, ricinoleic acid, stearic acid, oleylamine, and 1-octadecene, performing a first heating under evacuation, adding an alkali metal hydroxide or oleate and ammonium fluoride during the first heating, performing a second heating under a protective atmosphere, adding ethanol and / or cyclohexane after cooling, collecting the precipitate by centrifugation, and dispersing it in 1-octadecene.
[0023] Preferably, the method for preparing the core by high-temperature thermal decomposition includes the following steps: adding a rare earth trifluoroacetate and an alkali metal trifluoroacetate into a solvent, heating at 100-150 °C for 10 minutes to 2 hours; then, heating at 220-320 °C for 5 minutes to 4 hours in a protective atmosphere, adding ethanol and / or cyclohexane after cooling, collecting the precipitate by centrifugation, and dispersing it in 1-octadecene to obtain a dispersion of core nanoparticles.
[0024] More preferably, the solvent is selected from oleic acid, linoleic acid, ricinoleic acid, stearic acid, oleylamine, and 1-octadecene.
[0025] More preferably, the method for preparing the core by high-temperature thermal decomposition specifically includes the following steps: adding a rare earth trifluoroacetate and an alkali metal trifluoroacetate into a solvent, performing a first heating under evacuation, performing a second heating under a protective atmosphere, adding ethanol and / or cyclohexane after cooling, collecting the precipitate by centrifugation, and dispersing it in 1-octadecene; the temperature of the first heating is 100-150 °C, and the time is 10 minutes to 2 hours; the temperature of the second heating is 220-320 °C, and the time is 5 minutes to 4 hours.
[0026] Preferably, the method for synthesizing the shell of the nano-luminescent probe comprises the following steps: subject the core nanoparticle dispersion to an anhydrous and anaerobic treatment and then add it to a syringe. Take rare earth trifluoroacetate and trifluoroacetate of an alkali metal or calcium and add them to a solvent. Conduct a third heating under evacuation, and conduct a fourth heating under a protective atmosphere. After 0 to 15 minutes from the start of the fourth heating, inject and add the core solution to the reaction solution. After cooling, add ethanol and / or cyclohexane, collect the precipitate by centrifugation, and disperse it in octadecene or cyclohexane. The solvent is selected from oleic acid, linoleic acid, ricinoleic acid, stearic acid, oleylamine, and octadecene. The temperature of the third heating is 100 - 150 °C, and the time is 10 minutes to 2 hours; the temperature of the fourth heating is 220 - 320 °C, and the time is 5 minutes to 4 hours.
[0027] Preferably, the method for synthesizing the shell of the nano-luminescent probe comprises the following steps: subject the nanoparticle dispersion having a core and one or more shell layers to an anhydrous and anaerobic treatment and then add it to a syringe. Take rare earth trifluoroacetate and trifluoroacetate of an alkali metal or calcium and add them to a solvent. Conduct a fifth heating under evacuation, and conduct a sixth heating under a protective atmosphere. After 0 to 15 minutes from the start of the sixth heating, inject and add the nanoparticle dispersion having a core and one or more shell layers to the reaction solution. After cooling, add ethanol and / or cyclohexane, collect the precipitate by centrifugation, and disperse it in octadecene or cyclohexane. The solvent is selected from oleic acid, linoleic acid, ricinoleic acid, stearic acid, oleylamine, and octadecene. The temperature of the fifth heating is 100 - 150 °C, and the time is 10 minutes to 2 hours; the temperature of the sixth heating is 220 - 320 °C, and the time is 5 minutes to 4 hours.
[0028] A method for preparing the above core-shell structured rare earth nano-luminescent probe, heat the reaction solution having only the shell precursor to the reaction temperature and then inject and add the core dispersion or the nanoparticle dispersion having a core and one or more shell layers (i.e., the core-shell structured rare earth nano-luminescent probe).
[0029] The nano-probe of the present invention can be synthesized by the hot injection core high-temperature thermal decomposition method. The hot injection core high-temperature thermal decomposition method refers to injecting the core particle solution into the reaction solution at the reaction temperature to inhibit the dissolution of the core and the mixing of ions, and synthesize a nano-probe having a core and one or more shell layer structures.
[0030] Preferably, the shell precursor includes rare earth trifluoroacetate, trifluoroacetate of an alkali metal or calcium.
[0031] Preferably, the reaction temperature is 220 - 320 °C.
[0032] In the present invention, trifluoroacetates of alkali metals or calcium are used to provide alkali metal or calcium ions and fluoride ions in the nanoparticle shell. If the target shell structure is AREF4, an alkali metal trifluoroacetate is added; if the target shell structure is CaF2, calcium trifluoroacetate is added. Rare earth trifluoroacetates are used to provide rare earth ions and fluoride ions in the nanoparticle shell.
[0033] In the present invention, a solution containing only the shell precursor trifluoroacetate is first heated to a temperature suitable for the shelling reaction to occur. At this temperature, the trifluoroacetate decomposes, releasing a large number of free ions, and their concentration rapidly reaches the saturation concentration. At this time, the core nanoparticle dispersion is injected, which can inhibit the dissolution of the core and ion mixing, optimize the doped ion distribution of the core-shell nanoparticles, and better synthesize the core-shell nanoparticles. For nanoparticles coated with an inert shell, inhibiting the dissolution of the core and ion mixing enables the inert shell to better protect the luminescent center and reduce the surface quenching effect, thereby improving the luminescence performance of the nanoparticles. The present invention improves the structural stability and luminescence performance of the nanoprobe.
[0034] Preferably, the solvent of the reaction solution is selected from oleic acid, linoleic acid, ricinoleic acid, stearic acid, oleylamine, and octadecene.
[0035] Preferably, the method for preparing the core-shell structured rare earth nano-luminescent probe includes the following steps:
[0036] (1) Heating the reaction solution containing only the shell precursor at 100 - 150 °C for 10 minutes to 2 hours;
[0037] (2) Continuing to heat in a protective atmosphere at 220 - 320 °C for 5 minutes to 4 hours. After 0 to 15 minutes from the start of heating, the core dispersion or the nanoparticle dispersion having a core and one or more layers of shells is injected into the reaction solution at one time. After cooling, ethanol and / or cyclohexane are added, and the precipitate is collected by centrifugation and dispersed in octadecene or cyclohexane.
[0038] In the present invention, when the core dispersion is injected into the reaction solution in step (2), nanoparticles having a core and one layer of shell are obtained.
[0039] When the nanoparticle dispersion having a core and one layer of shell is injected into the reaction solution in step (2), nanoparticles having a core and multiple layers of shells are obtained.
[0040] When the nanoparticle dispersion having a core and multiple layers of shells is injected into the reaction solution in step (2), nanoparticles having a core and multiple layers of shells with one more layer of shell are obtained.
[0041] By the method of the present invention, a shell layer can be epitaxially grown on the core particles or core-shell particles. Through multiple reactions, multiple shell layers can be grown, and finally the target nano-probe with a core and multiple shell layers can be obtained.
[0042] By the method of the present invention, the nano-probe with a core and one or more shell layer structures can be simply and quickly synthesized.
[0043] In the present invention, the thermal decomposition temperature of the shell precursor trifluoroacetate is about 200 °C. The heating temperature in step (2) is higher than the thermal decomposition temperature of the shell precursor. At this time, the trifluoroacetate decomposes rapidly, generating alkali metal ions or calcium ions, rare earth ions and fluoride ions. The concentration of AREF4 or CaF2 monomers in the solution rises rapidly, exceeding the saturation concentration and the nucleation concentration, and small kinetically stable cubic phase nanoparticles begin to form in the solution. After the core dispersion liquid is added by thermal injection, the supersaturated monomer concentration in the reaction solution can effectively inhibit the dissolution of the added core particles and inhibit the ion mixing caused by the dissolution of the core. The small kinetically stable cubic phase nanoparticles in the reaction solution will gradually dissolve and epitaxially grow on the surface of the thermodynamically stable core particles injected, so as to obtain the nanoparticles with a core and one shell layer. The purpose of injecting the core particle solution into the reaction solution 0 to 15 minutes after the start of the fourth heating is to ensure that the reaction solution is a saturated solution when added, and the small kinetically stable cubic phase nanoparticles formed in the solution will not be converted into thermodynamically stable hexagonal phase particles, resulting in the failure to obtain core-shell particles.
[0044] Preferably, the core dispersion liquid or the dispersion liquid of the nanoparticles with a core and one or more shell layers is subjected to anhydrous and anaerobic treatment before injection and then added to the syringe.
[0045] Further preferably, the anhydrous and anaerobic treatment includes evacuation and / or heating.
[0046] Further preferably, the dispersion liquid after anhydrous and anaerobic treatment is pumped into the syringe under the protection of an inert gas atmosphere.
[0047] Preferably, the preparation method of the core-shell structure rare earth nano-luminescent probe specifically includes the following steps: the core nanoparticle dispersion liquid is subjected to anhydrous and anaerobic treatment and then added to the syringe. Take rare earth trifluoroacetate and trifluoroacetate of alkali metal or calcium and add them to a solvent selected from oleic acid, linoleic acid, ricinoleic acid, stearic acid, oleylamine, and octadecene. Perform the third heating under evacuation and the fourth heating under the protection of an inert gas atmosphere. 0 to 15 minutes after the start of the fourth heating, inject the core solution into the reaction solution. After cooling, add ethanol and / or cyclohexane, centrifuge to collect the precipitate, and disperse it in octadecene or cyclohexane.
[0048] Further preferably, the third heating temperature is 100 - 150 °C, and the time is 10 minutes to 2 hours; the fourth heating temperature is 220 - 320 °C, and the time is 5 minutes to 4 hours.
[0049] Further preferably, the nanoparticles with a core and one or more shell layers are further coated to synthesize nanoprobes with a core and multiple shell layers. The synthesis method includes the following steps: After subjecting the dispersion of nanoparticles with a core and one or more shell layers to an anhydrous and anaerobic treatment, it is added to a syringe. Take rare earth trifluoroacetate and trifluoroacetate of an alkali metal or calcium and add them to a solvent selected from oleic acid, linoleic acid, ricinoleic acid, stearic acid, oleylamine, and octadecene. Perform a fifth heating under evacuation, and perform a sixth heating under a protective atmosphere. After 0 to 15 minutes from the start of the sixth heating, inject and add the dispersion of nanoparticles with a core and one or more shell layers into the reaction solution. After cooling, add ethanol and / or cyclohexane, centrifuge to collect the precipitate, and disperse it in octadecene or cyclohexane.
[0050] The fifth heating temperature is 100 - 150 °C, and the time is 30 minutes to 2 hours; the sixth heating temperature is 220 - 320 °C, and the time is 5 minutes to 4 hours.
[0051] An application of the above core-shell structured rare earth nanoluminescent probe, using the nanoluminescent probe for high-resolution bioimaging, small-scale temperature sensing, photothermal therapy, detection of metal ions or specific biomolecules and proteins.
[0052] In the prior art, the current process for synthesizing core-shell nanoparticles mostly includes heating the core particles and the shell precursor together in a solution to the reaction temperature. However, the shell precursor trifluoroacetate can only decompose above 200 °C to release sodium ions, fluoride ions, and shell rare earth ions. Before the temperature reaches the reaction temperature, part of the core particles will dissolve, and the dissolved core elements and the subsequent generated shell elements will grow together in the shell, resulting in the mixing of doped ions in different layers of the core-shell nanoparticles and affecting the structure and luminescence performance of the nanoparticles. For nanoparticles coated with an inert shell, the dissolution of the core and ion mixing lead to the fact that during the coating process, the shell is not completely composed of optically inert elements, but is doped with a small amount of luminescent center elements, forming an energy transfer network, which may transfer the energy absorbed by the luminescent center to the quenching center on the surface of the nanoparticles, reducing its luminescence intensity and quantum efficiency.
[0053] The present invention develops a new synthesis method for core-shell structured nanoparticles to inhibit ion mixing and improve the luminescence performance of rare earth luminescent probes.
[0054] Compared with the prior art, the present invention has the following beneficial effects:
[0055] 1. The present invention provides a method for synthesizing core-shell structured rare-earth nanophosphors by a thermal injection core method, which can inhibit the dissolution of the core and ion mixing, optimize the distribution of doped ions in the core-shell nanoparticles, and better synthesize the core-shell nanoparticles.
[0056] 2. The reaction solution with only the shell precursor is heated to the reaction temperature in the present invention. At this time, it has decomposed to generate corresponding ions and produced kinetically stable α-phase particles, which is a supersaturated solution of rare-earth fluoride double salts. Adding the core at this time can inhibit the dissolution of the core, and then the Ostwald ripening process occurs. The kinetically stable α-phase particles generated in the early stage dissolve and grow on the added core to obtain the core-shell material, improving the structural stability and luminescence performance of the nanophosphor.
[0057] 3. The present invention can be used to synthesize nanomaterials doped with various rare-earth elements. Another ion can also be one or more of Li / Na / K. Materials with one or more shell layers can be synthesized, materials with various doping or core-shell ratios can be synthesized, and the solvents, reactants, and reaction conditions used are also more extensive, with strong applicability.
[0058] 4. The method of the present invention can simply and quickly synthesize nanophosphors with a core and one or more shell layer structures.
[0059] 5. The core-shell rare-earth nanophosphors synthesized by the thermal injection core method of the present invention can be used for high-resolution bioimaging, small-scale temperature sensing, photothermal therapy, detection of metal ions or specific biomolecules and proteins, etc., and have broad application prospects.
[0060] 6. The present invention has high generality and universality, can synthesize various types of nanoparticles, and can reduce the luminescence loss caused by ion diffusion during the synthesis of core-shell materials. BRIEF DESCRIPTION OF THE DRAWINGS
[0061] Figure 1 is a schematic diagram of the method for synthesizing nanophosphors with a core-shell structure by the thermal injection core high-temperature thermal decomposition method of the present invention;
[0062] Figure 2 is a transmission electron microscopy image of the core particles NaYbF4:2%Er in Example 1 of the present invention;
[0063] Figure 3 is a transmission electron microscopy image of the nanophosphor NaYbF4:2%Er@NaYF4(1:1) in Example 2 of the present invention;
[0064] Figure 4 is a transmission electron microscopy image of the nanophosphor NaYbF4:2%Er@NaYF4(1:2) in Example 3 of the present invention;
[0065] Figure 5 Schematic diagram of the detection results of the luminescence intensities of the core particles NaYbF4: 2% Er, the nanoprobes NaYbF4: 2% Er@NaYF4(1:1), and the nanoprobes NaYbF4: 2% Er@NaYF4(1:2) in Embodiments 1-3 of the present invention;
[0066] Figure 6 Transmission electron microscopy image of the core particle NaYF4: 20% Er in Embodiment 4 of the present invention;
[0067] Figure 7 Transmission electron microscopy image of the core-shell particle NaYF4: 20% Er@NaYF4(1:1) in Embodiment 5 of the present invention;
[0068] Figure 8 Transmission electron microscopy image of the nanoprobe NaYF4: 20% Er@NaYF4@NaYF4@30% Nd(1:1:1) in Embodiment 6 of the present invention;
[0069] Figure 9 Schematic diagram of the detection results of the luminescence intensities of the core particle NaYF4: 20% Er, the core-shell particle NaYF4: 20% Er@NaYF4(1:1), and the nanoprobe NaYF4: 20% Er@NaYF4@NaYF4@30% Nd(1:1:1) in Embodiments 4-6 of the present invention;
[0070] Figure 10 Transmission electron microscopy image of the nanoprobe NaYbF4: 2% Er@NaYF4(1:1) in Comparative Example 1;
[0071] Figure 11 Transmission electron microscopy image of the nanoprobe NaYbF4: 2% Er@NaYF4(1:2) in Comparative Example 2;
[0072] Figure 12 Schematic diagram of the detection results of the luminescence intensities of the core particle NaYbF4: 2% Er, the nanoprobe NaYbF4: 2% Er@NaYF4(1:1), and the nanoprobe NaYbF4: 2% Er@NaYF4(1:2) in Embodiment 1 of the present invention and Comparative Examples 1-2; Detailed implementation manners
[0073] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention will be introduced in conjunction with preferred embodiments, this does not mean that the features of this invention are limited to this implementation manner. On the contrary, the purpose of introducing the invention in conjunction with the implementation manner is to cover other alternatives or modifications that may be extended based on the claims of the present invention. In order to provide a deep understanding of the present invention, many specific details will be included in the following description. The present invention can also be implemented without using these details. In addition, in order to avoid confusing or obscuring the key points of the present invention, some specific details will be omitted in the description. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.
[0074] It should be noted that in this specification, similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.
[0075] The terms "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.
[0076] To make the purpose, technical solutions and advantages of the present invention clearer, the implementation manners of the present invention will be further described in detail below with reference to the drawings.
[0077] The implementation manner of the present invention discloses a synthesis method of a luminescent nanoprobe. The nanoprobe has a nanoparticle with a core and one or more shell layer structures, and the shell layer coats the core. The core is synthesized by a solvothermal method or a high-temperature thermal decomposition method, and the core-shell nanoparticles are synthesized by a thermal injection core high-temperature thermal decomposition method.
[0078] In some specific implementation manners of the present invention, as Figure 1 shown, the preparation method of the nanoprobe is: heating a reaction solution having only a shell precursor, the shell precursor decomposes to release corresponding ions, and a core dispersion is injected under the shell growth condition to synthesize a nanoprobe having a core and a shell.
[0079] In some specific implementation manners of the present invention, the core structure of the nanoprobe is AREF4, where A is selected from one or more of the alkali metals Li, Na, and K; RE is a rare earth element selected from one or more of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The shell structure of the nanoparticle is AREF4 or CaF2, and each shell layer is the same as or different from the core or the previous shell layer. The nanoprobe has a hexagonal or cubic phase structure, the particle size of the core is 3 - 50 nm, and the shell thickness is 0.1 - 20 nm.
[0080] In some specific embodiments of the present invention, the core of the nanoprobe is synthesized by a solvothermal method. The specific synthesis method comprises the following steps: Add a rare earth salt into a three-necked flask. The rare earth salt can be a salt of one or more rare earth elements, and the rare earth salt is one of chloride salts, nitrate salts or acetate salts. Add a solvent selected from oleic acid, linoleic acid, ricinoleic acid, stearic acid, oleylamine, and octadecene into the three-necked flask. Conduct a first heating under evacuation for anhydrous and anaerobic treatment. After the solution becomes clear and bubble-free, add a hydroxide or oleate of an alkali metal under the protection of an inert atmosphere. Evacuate again. After the solution becomes clear and bubble-free, add ammonium fluoride under the protection of an inert atmosphere. Evacuate, and then conduct an evacuation and gas replacement treatment. Repeatedly introduce the inert atmosphere into the solution and evacuate again, repeating 3 to 6 times. The temperature of the first heating is 100-150°C, and the time is 10 minutes to 2 hours. Introduce the inert atmosphere into the solution, quickly raise the temperature of the solution, and conduct a second heating on the solution. The temperature of the second heating is 220-320°C, and the time is 5 minutes to 4 hours. After the second heating is completed, cool the solution to room temperature, add ethanol and / or cyclohexane to precipitate the nanoparticles, collect the precipitate by centrifugation, and disperse it in octadecene.
[0081] In some specific embodiments of the present invention, the core of the nanoprobe is synthesized by high-temperature thermal decomposition. The specific synthesis method comprises the following steps: Add a rare earth trifluoroacetate into a three-necked flask, and add an alkali metal trifluoroacetate into the three-necked flask. Add a solvent selected from oleic acid, linoleic acid, ricinoleic acid, stearic acid, oleylamine, and octadecene into the three-necked flask. Conduct a first heating under evacuation for anhydrous and anaerobic treatment. After the solution becomes clear and bubble-free, conduct an evacuation and gas replacement treatment. Repeatedly introduce the inert atmosphere into the solution and evacuate again, repeating 3 to 6 times to ensure that water and other low-boiling substances in the reaction solution are completely removed. The temperature of the first heating is 100-150°C, and the time is 10 minutes to 2 hours. Introduce the inert atmosphere into the solution, quickly raise the temperature of the solution, and conduct a second heating on the solution. The temperature of the second heating is 220-320°C, and the time is 5 minutes to 4 hours. After the second heating is completed, cool the solution to room temperature, add ethanol and / or cyclohexane to precipitate the nanoparticles, collect the precipitate by centrifugation, and disperse it in octadecene.
[0082] In some specific embodiments of the present invention, the nanoprobe having a core and a shell layer is synthesized by the thermal decomposition method of the hot injection core at high temperature. The specific synthesis method comprises the following steps: After subjecting the core nanoparticle dispersion to an anhydrous and anaerobic treatment, it is added to a syringe. Take rare earth trifluoroacetate and alkali metal trifluoroacetate and add them to a solvent selected from oleic acid, linoleic acid, ricinoleic acid, stearic acid, oleylamine, and octadecene. Perform a third heating under evacuation, and perform a fourth heating under a protective atmosphere. After 0 to 15 minutes from the start of the fourth heating, inject the core dispersion into the reaction solution. After cooling, add ethanol and / or cyclohexane, centrifuge to collect the precipitate, and disperse it in octadecene or cyclohexane.
[0083] In some specific embodiments of the present invention, add rare earth trifluoroacetate to a three-necked flask. The rare earth trifluoroacetate can be a trifluoroacetate of one or more rare earth elements, and is used to provide rare earth ions and fluoride ions in the nanoparticle shell layer. Add the trifluoroacetate of an alkali metal or calcium to the three-necked flask. The trifluoroacetate of an alkali metal or calcium is used to provide alkali metal or calcium ions and fluoride ions in the nanoparticle shell layer. If the target shell structure is AREF4, then add alkali metal trifluoroacetate. If the target shell structure is CaF2, then add calcium trifluoroacetate. Add the solvent to the three-necked flask. The solvent is selected from oleic acid, linoleic acid, ricinoleic acid, stearic acid, oleylamine, and octadecene; oleic acid, linoleic acid, ricinoleic acid, stearic acid, or oleylamine can dissolve the added salt and coordinate with rare earth ions to provide protection. Octadecene is an inert solvent used to dilute the solution, adjust the ligand concentration, and avoid the solution from being too viscous. By controlling the ratio of the amounts of each solvent added, nanoparticles with a specific shape and particle size can be synthesized. The above solution is called the reaction solution.
[0084] In some specific embodiments of the present invention, perform an anhydrous and anaerobic treatment on the core dispersion. The core dispersion is an octadecene dispersion of the synthesized core. Octadecene has no coordination ability. Selecting octadecene as a dispersant can avoid the dissolution of the core during the anhydrous and anaerobic treatment. The anhydrous and anaerobic treatment includes evacuation and / or heating to remove water and other low-boiling substances in the core solution, avoid introducing water or other low-boiling solvents during subsequent hot injection, and ensure the uniformity and structural stability of the synthesized nanoprobe. Under the protection of a protective atmosphere, draw the core dispersion into a syringe.
[0085] In some specific embodiments of the present invention, the reaction solution is subjected to a third heating under evacuation for anhydrous and anaerobic treatment to remove water and other low-boiling substances in the reaction solution, ensuring the uniformity and structural stability of the synthesized nanoprobes. After the solution becomes clear and bubble-free, evacuation and gas replacement treatment are carried out. The protective atmosphere is repeatedly introduced into the solution and then evacuated again, and this is repeated 3 to 6 times to ensure the complete removal of water and other low-boiling substances in the reaction solution. The temperature of the third heating is 100 - 150 °C, and the time is 10 minutes to 2 hours. These conditions can ensure the complete dissolution of the trifluoroacetate salt and the complete removal of low-boiling substances.
[0086] In some specific embodiments of the present invention, a protective atmosphere is introduced into the solution, and the solution is rapidly heated to carry out a fourth heating on the solution. The temperature of the fourth heating is 220 - 320 °C, and the time is 5 minutes to 4 hours. Selecting a specific fourth heating temperature can synthesize nanoprobes with specific morphology and particle size. After 0 to 15 minutes from the start of the fourth heating, the core dispersion liquid is injected into the reaction solution at one time. The thermal decomposition temperature of the shell precursor trifluoroacetate salt is around 200 °C. Since the fourth heating temperature is higher than the thermal decomposition temperature of the shell precursor, the trifluoroacetate salt has undergone rapid decomposition at this time, generating alkali metal ions or calcium ions, rare earth ions, and fluoride ions. The concentration of AREF4 or CaF2 monomers in the solution rapidly increases, exceeding the saturation concentration and the nucleation concentration, and small kinetically stable cubic-phase nanoparticles begin to form in the solution. After the core solution is added by thermal injection, the supersaturated monomer concentration in the reaction solution can effectively inhibit the dissolution of the added core particles and inhibit the ion mixing caused by the dissolution of the core. The kinetically stable small cubic-phase nanoparticles in the reaction solution will gradually dissolve and epitaxially grow on the surface of the thermodynamically stable core particles injected, to obtain nanoparticles with a core and a single shell layer. The purpose of injecting the core particle solution into the reaction solution 0 to 15 minutes after the start of the fourth heating is to ensure that the reaction solution is a saturated solution when added, and the small kinetically stable cubic-phase nanoparticles formed in the solution will not transform into thermodynamically stable hexagonal-phase particles, resulting in the failure to obtain core-shell particles.
[0087] In some specific embodiments of the present invention, after the fourth heating is completed, the solution is cooled to room temperature, and ethanol and / or cyclohexane are added to precipitate the nanoparticles. After centrifugation, the precipitate is collected and dispersed in octadecene or cyclohexane.
[0088] In some specific embodiments of the present invention, the nanoprobe with a core and multiple shell layers is synthesized by the high-temperature thermal decomposition method of the hot injection core. The synthesis method is the same as that of the nanoprobe with a core and a single shell layer, except that the injected dispersion liquid is a specific nanoparticle dispersion liquid with a core and one or more shell layers. By using the high-temperature thermal decomposition method of the hot injection core, a shell layer can be epitaxially grown on the core particles or core-shell particles, and multiple shell layers can be grown through multiple reactions, finally obtaining the target nanoprobe with a core and multiple shell layers.
[0089] The following are examples of the specific embodiments of the present invention. The raw materials therein are all known compounds, which can be obtained through commercial channels or prepared according to methods known in the art.
[0090] Example 1
[0091] Synthesis of core particles β-NaYbF4:2% Er:
[0092] The β-NaYbF4:2% Er core nanoparticles are synthesized by the solvothermal method. 0.98 mmol of ytterbium chloride and 0.02 mmol of erbium chloride are added to a 100 mL three-necked flask; 25 mmol of oleic acid and 47 mmol of octadecene are added to the three-necked flask. After the mixed solution is evacuated until there are no bubbles under stirring, it is heated to 120 °C for the first heating, and heated and stirred until the solid is completely dissolved. After the solution becomes clear, 2.5 mmol of sodium hydroxide is added under nitrogen protection, heated and evacuated until the sodium hydroxide is completely dissolved, 4 mmol of ammonium fluoride is added under nitrogen protection, heated and evacuated for 10 minutes, and evacuated and replaced 5 times. Under nitrogen protection, the solution is quickly heated to 300 °C for the second heating, and the reaction is carried out for 50 minutes. After the reaction is completed, when the solution is cooled to room temperature, 40 mL of ethanol is added, and the mixture is centrifuged at a speed of 11000 rpm for 10 minutes. The precipitate is taken and dissolved in 4 mL of octadecene to obtain the β-NaYbF4:2% Er core particle dispersion liquid.
[0093] The transmission electron microscopy image of the core particles NaYbF4:2% Er prepared in this example is as Figure 2 shown, and it can be seen that they are spherical, uniform, and monodisperse nanoparticles with a particle size of about 17.3 nm.
[0094] Example 2
[0095] Synthesis of the nanoprobe β-NaYbF4:2% Er@NaYF4(1:1):
[0096] The nano-probe β-NaYbF4:2%Er@NaYF4(1:1) was synthesized by the hot injection high-temperature thermal decomposition method for the core. 4 mL of the core dispersion was added to a 100 mL three-necked flask, and the temperature was raised to 100 °C under evacuation and maintained for 10 minutes. Nitrogen was introduced, and after the solution cooled to room temperature, 1 mL of the β-NaYbF4:2%Er core dispersion was drawn with a syringe under nitrogen protection. 0.25 mmol of yttrium trifluoroacetate and 0.25 mmol of sodium trifluoroacetate were added to a 100 mL three-necked flask; 20 mmol of oleic acid and 17 mmol of octadecene were added to the three-necked flask. After the mixed solution was evacuated until there were no bubbles under stirring, it was heated to 120 °C for the third heating, and heated and stirred until the solid was completely dissolved. After the solution became clear, the gas was evacuated and replaced 5 times. Under nitrogen protection, the solution was quickly heated to 300 °C for the fourth heating. 5 minutes after the start of the fourth heating, the core dispersion was injected into the reaction solution at one time, and the reaction was carried out for 45 minutes. After the reaction was completed, after the solution cooled to room temperature, 20 mL of ethanol was added, and the mixture was centrifuged at a speed of 11000 rpm for 10 minutes. The precipitate was taken and dissolved in 5 mL of cyclohexane to obtain the nano-probe β-NaYbF4:2%Er@NaYF4(1:1) dispersion.
[0097] The transmission electron microscopy imaging photograph of the nano-probe NaYbF4:2%Er@NaYF4(1:1) prepared in this example is as Figure 3 shown, and it can be seen that it is spherical, uniform, and monodisperse nanoparticles with a particle size of about 19.7 nm.
[0098] Example 3
[0099] Synthesis of the nano-probe β-NaYbF4:2%Er@NaYF4(1:2):
[0100] The nano-probe β-NaYbF4:2% Er@NaYF4(1:2) was synthesized by the thermal injection core high-temperature thermal decomposition method. 4 mL of the β-NaYbF4:2% Er core dispersion was added to a 100 mL three-necked flask. The temperature was raised to 100 °C under air extraction and maintained for 10 minutes. Nitrogen was introduced. After the solution was cooled to room temperature, 1 mL of the β-NaYbF4:2% Er core dispersion was drawn with a syringe under nitrogen protection. 0.5 mmol of yttrium trifluoroacetate and 0.5 mmol of sodium trifluoroacetate were added to the 100 mL three-necked flask; 20 mmol of oleic acid and 17 mmol of octadecene were added to the three-necked flask. After the mixed solution was evacuated until there were no bubbles under stirring, it was heated to 120 °C for the third heating, and heated and stirred until the solid was completely dissolved. After the solution became clear, the gas was evacuated and replaced 5 times. Under nitrogen protection, the solution was quickly heated to 300 °C for the fourth heating. 5 minutes after the start of the fourth heating, the core dispersion was injected into the reaction solution at one time, and the reaction was carried out for 45 minutes. After the reaction was completed, the solution was cooled to room temperature, 20 mL of ethanol was added, and the mixture was centrifuged at a speed of 11000 rpm for 10 minutes. The precipitate was taken and dissolved in 5 mL of cyclohexane to obtain the nano-probe β-NaYbF4:2% Er@NaYF4(1:2) dispersion.
[0101] The transmission electron microscopy image of the nano-probe NaYbF4:2% Er@NaYF4(1:2) prepared in this example is as Figure 4 shown. It can be seen that it is spherical, uniform, and monodisperse nanoparticles with a particle size of about 22.3 nm.
[0102] Figure 5 is a schematic diagram of the detection results of the luminescence intensities of the core particles NaYbF4:2% Er, the nano-probes NaYbF4:2% Er@NaYF4(1:1), and the nano-probes NaYbF4:2% Er@NaYF4(1:2) in Examples 1-3. It can be seen from the figure that the luminescence intensity of the nano-probe NaYbF4:2% Er@NaYF4(1:1) at 541 nm is about 25 times that of the core NaYbF4:2% Er, and the luminescence intensity of the nano-probe NaYbF4:2% Er@NaYF4(1:2) at 541 nm is about 110 times that of the core NaYbF4:2% Er. The synthesis of the core-shell structured rare-earth nano-luminescent probe by the thermal injection core high-temperature thermal decomposition method greatly improves its luminescence performance.
[0103] Example 4
[0104] Synthesis of the core particles β-NaYF4:20% Er:
[0105] The β-NaYF4:20%Er core nanoparticles were synthesized by the solvothermal method. 0.8 mmol of yttrium chloride and 0.2 mmol of erbium chloride were added to a 100 mL three-necked flask; 25 mmol of oleic acid and 47 mmol of octadecene were added to the three-necked flask. After the mixed solution was evacuated until there were no bubbles under stirring, it was heated to 120 °C for the first heating, and heated and stirred until the solid was completely dissolved. After the solution became clear, 2.5 mmol of sodium hydroxide was added under nitrogen protection, and it was heated and evacuated until the sodium hydroxide was completely dissolved. 4 mmol of ammonium fluoride was added under nitrogen protection, and it was heated and evacuated for 10 minutes, and the gas was replaced 5 times. Under nitrogen protection, the solution was quickly heated to 300 °C for the second heating, and the reaction was carried out for 50 minutes. After the reaction was completed, when the solution was cooled to room temperature, 40 mL of ethanol was added, and the mixture was centrifuged at a speed of 11000 rpm for 10 minutes. The precipitate was taken and dissolved in 4 mL of octadecene to obtain the β-NaYF4:20%Er core particle dispersion.
[0106] The transmission electron microscopy image of the core particles NaYF4:20%Er prepared in this example is as Figure 6 shown. It can be seen that they are spherical, uniform, and monodisperse nanoparticles with a particle size of about 18.6 nm.
[0107] Example 5
[0108] Synthesis of the nanoprobe β-NaYF4:20%Er@NaYF4(1:1):
[0109] The nanoprobe β-NaYF4:20%Er@NaYF4(1:1) was synthesized by the hot injection core high-temperature pyrolysis method. 4 mL of the β-NaYF4:20%Er core dispersion was added to a 100 mL three-necked flask, and it was heated to 100 °C under evacuation and maintained for 10 minutes. Nitrogen was introduced, and when the solution was cooled to room temperature, 2 mL of the β-NaYF4:20%Er core dispersion was drawn with a syringe under nitrogen protection. 0.5 mmol of yttrium trifluoroacetate and 0.5 mmol of sodium trifluoroacetate were added to a 100 mL three-necked flask; 20 mmol of oleic acid and 14 mmol of octadecene were added to the three-necked flask. After the mixed solution was evacuated until there were no bubbles under stirring, it was heated to 120 °C for the third heating, and heated and stirred until the solid was completely dissolved. After the solution became clear, the gas was replaced 5 times. Under nitrogen protection, the solution was quickly heated to 300 °C for the fourth heating. 5 minutes after the start of the fourth heating, the core dispersion was injected into the reaction solution at one time, and the reaction was carried out for 45 minutes. After the reaction was completed, when the solution was cooled to room temperature, 20 mL of ethanol was added, and the mixture was centrifuged at a speed of 11000 rpm for 10 minutes. The precipitate was taken and dissolved in 4 mL of octadecene to obtain the nanoprobe β-NaYF4:20%Er@NaYF4(1:1) dispersion.
[0110] The transmission electron microscopy image of the core-shell particles NaYF4:20% Er@NaYF4 (1:1) prepared in this example is as follows Figure 7 shown. It can be seen that they are spherical, uniform, and monodisperse nanoparticles with a particle size of approximately 21.2 nm.
[0111] Example 6
[0112] Synthesis of the nanoprobe β-NaYF4:20% Er@NaYF4@NaYF4@30% Nd (1:1:1):
[0113] The nanoprobe β-NaYF4:20% Er@NaYF4@NaYF4@30% Nd (1:1:1) was synthesized by the hot injection core high-temperature pyrolysis method. Add 2 mL of the β-NaYF4:20% Er@NaYF4 (1:1) nanoparticle dispersion into a 100 mL three-necked flask, heat it to 100 °C under vacuum for 10 minutes, introduce nitrogen, and wait for the solution to cool to room temperature. Under nitrogen protection, use a syringe to extract 2 mL of the β-NaYF4:20% Er@NaYF4 (1:1) dispersion. Add 0.175 mmol of yttrium trifluoroacetate, 0.075 mmol of neodymium trifluoroacetate, and 0.25 mmol of sodium trifluoroacetate into the 100 mL three-necked flask; add 20 mmol of oleic acid and 14 mmol of octadecene into the three-necked flask. After the mixture is evacuated to no bubbles under stirring, heat it to 120 °C for the fifth heating, heat and stir until the solid is completely dissolved, and evacuate and replace the gas 5 times after the solution becomes clear. Under nitrogen protection, quickly heat the solution to 300 °C for the sixth heating. Five minutes after the start of the sixth heating, inject the β-NaYF4:20% Er@NaYF4 (1:1) dispersion into the reaction solution at one time, and react for 45 minutes. After the reaction is completed, wait for the solution to cool to room temperature, add 20 mL of ethanol, centrifuge the mixture at a speed of 11000 rpm for 10 minutes, and dissolve the precipitate in 5 mL of cyclohexane to obtain the nanoprobe β-NaYF4:20% Er@NaYF4@NaYF4@30% Nd (1:1:1) dispersion.
[0114] The transmission electron microscopy image of the nanoprobe NaYF4:20% Er@NaYF4@NaYF4@30% Nd (1:1:1) prepared in this example is as follows Figure 8 shown. It can be seen that they are spherical, uniform, and monodisperse nanoparticles with a particle size of approximately 24.3 nm.
[0115] Figure 9Schematic diagram of the detection results of the luminescence intensities of the core particles NaYF4: 20% Er, core-shell particles NaYF4: 20% Er@NaYF4(1:1), and nanoprobes NaYF4: 20% Er@NaYF4@NaYF4@30% Nd(1:1:1) in Examples 4-6 of the present invention. It can be seen from the figure that the luminescence intensity of the nanoprobe NaYF4: 20% Er@NaYF4(1:1) at 541 nm is about 43 times that of the core NaYF4: 20% Er, and the luminescence intensity of the nanoprobe NaYF4: 20% Er@NaYF4@NaYF4@30% Nd(1:1:1) at 541 nm is about 176 times that of the core NaYF4: 20% Er. The synthesis of core-shell structured rare earth nano-luminescent probes by the thermal injection core high-temperature thermal decomposition method significantly improves their luminescence performance.
[0116] Comparative Example 1
[0117] Synthesis of the nanoprobe β-NaYbF4: 2% Er@NaYF4(1:1) (using the high-temperature thermal decomposition method of heating the core and shell precursors together in solution):
[0118] The nanoprobe β-NaYbF4: 2% Er@NaYF4(1:1) was synthesized by the high-temperature thermal decomposition method. 0.25 mmol of yttrium trifluoroacetate and 0.25 mmol of sodium trifluoroacetate were added to a 100 mL three-necked flask; 1 mL of the core dispersion was added to the 100 mL three-necked flask; 20 mmol of oleic acid and 17 mmol of octadecene were added to the three-necked flask. After the mixed solution was evacuated to no bubbles under stirring, it was heated to 120 °C for the third heating, and heated and stirred until the solid was completely dissolved. After the solution became clear, it was evacuated and replaced with gas 5 times. Under nitrogen protection, the solution was quickly heated to 300 °C for the fourth heating, and the reaction was carried out for 45 minutes. After the reaction was completed, when the solution cooled to room temperature, 20 mL of ethanol was added, and the mixture was centrifuged at a speed of 11000 rpm for 10 minutes. The precipitate was taken and dissolved in 5 mL of cyclohexane to obtain the nanoprobe β-NaYbF4: 2% Er@NaYF4(1:1) dispersion.
[0119] The transmission electron microscopy image of the nanoprobe NaYbF4: 2% Er@NaYF4(1:1) prepared in this comparative example is as Figure 10 shown, and it can be seen that it is spherical, uniform, and monodispersed nanoparticles with a particle size of about 19.8 nm.
[0120] Comparative Example 2
[0121] Synthesis of the nanoprobe β-NaYbF4: 2% Er@NaYF4(1:2) (using the high-temperature thermal decomposition method of heating the core and shell precursors together in solution):
[0122] The nanosensor β-NaYbF4:2%Er@NaYF4(1:2) was synthesized by the high-temperature thermal decomposition method. 0.5 mmol of yttrium trifluoroacetate and 0.5 mmol of sodium trifluoroacetate were added to a 100 mL three-necked flask; 1 mL of the core dispersion was added to the 100 mL three-necked flask; 20 mmol of oleic acid and 17 mmol of octadecene were added to the three-necked flask. After the mixed solution was evacuated until there were no bubbles under stirring, it was heated to 120 °C for the third heating, and heated with stirring until the solid was completely dissolved. After the solution became clear, it was evacuated and replaced with gas 5 times. Under nitrogen protection, the solution was quickly heated to 300 °C for the fourth heating, and the reaction was carried out for 45 minutes. After the reaction ended, when the solution cooled to room temperature, 20 mL of ethanol was added, and the mixture was centrifuged at a speed of 11000 rpm for 10 minutes. The precipitate was taken and dissolved in 5 mL of cyclohexane to obtain the nanosensor β-NaYbF4:2%Er@NaYF4(1:1) dispersion.
[0123] The transmission electron microscopy image of the nanosensor NaYbF4:2%Er@NaYF4(1:2) prepared in this comparative example is as Figure 11 shown. It can be seen that it is spherical, uniform, and monodisperse nanoparticles with a particle size of about 22.3 nm.
[0124] By comparing Examples 2-3 with Comparative Examples 1-2, it can be found that for the nanoparticles synthesized by the thermal injection core high-temperature thermal decomposition method, when the feeding ratio and other reaction conditions are the same, core-shell nanoparticles with the same morphology and particle size as those synthesized by the common method of heating the core and shell precursors together in solution by the high-temperature thermal decomposition method can be stably synthesized, with high feasibility, universality, implementability, and repeatability.
[0125] Figure 12It is a schematic diagram of the detection results of the luminescence intensities of the core particles NaYbF4: 2% Er, the nanoprobes NaYbF4: 2% Er@NaYF4(1:1), and the nanoprobes NaYbF4: 2% Er@NaYF4(1:2) in Example 1 and Comparative Examples 1-2. It can be seen from the figure that the luminescence intensity of the nanoprobe NaYbF4: 2% Er@NaYF4(1:1) synthesized by the high-temperature thermal decomposition method of heating the core and the shell precursor together in solution at 541 nm is about 16 times that of the core NaYbF4: 2% Er, and the luminescence intensity of the nanoprobe NaYbF4: 2% Er@NaYF4(1:2) at 541 nm is about 70 times that of the core NaYbF4: 2% Er. By comparing Examples 1-3 with Comparative Examples 1-2, it can be found that for the two core-shell structured rare-earth nano-luminescent probes synthesized by the thermal injection core high-temperature thermal decomposition method with the same feed ratio and other reaction conditions, the luminescence performances are 1.56 times and 1.57 times respectively of those of the nanoprobes synthesized by the high-temperature thermal decomposition method of heating the core and the shell precursor together in solution. This shows that for the core-shell structured rare-earth nano-luminescent probes synthesized by the thermal injection core high-temperature thermal decomposition method, compared with the high-temperature thermal decomposition method of heating the core and the shell precursor together in solution, it can inhibit the dissolution of the core and the ion mixing during the reaction process and improve the luminescence performance of the nanoprobe.
[0126] The above description of the embodiments is to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and all improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.
Claims
1. A core-shell structured rare earth nano luminescent probe, characterized in that It includes a core and one or more shell layers coated on the core. The core structure is AREF4, and the shell layer structure is AREF4 or CaF2, where A is selected from one or more of alkali metals, and RE is a rare earth element; The core-shell structured rare earth nanophosphor is synthesized by the thermal injection core high-temperature thermal decomposition method.
2. The core-shell structured rare earth nano luminescent probe according to claim 1, characterized in that, The alkali metal is selected from one or more of Li, Na, and K; The rare earth element is selected from one or more of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; Each shell layer is the same as or different from the core or the previous shell layer.
3. The core-shell structured rare earth nanophosphor probe according to claim 1, wherein The core is synthesized by the solvothermal method or the high-temperature thermal decomposition method; The nanophosphor has a hexagonal or cubic phase structure. The particle size of the core is 3 - 50 nm, and the shell layer thickness is 0.1 - 20 nm.
4. The core-shell structured rare earth nano luminescent probe according to claim 1, characterized in that, The preparation method of the core includes the following steps: Add a rare earth salt to a solvent, heat it at 100 - 150 °C for 10 minutes to 2 hours, and add an alkali metal compound and ammonium fluoride during this process; then, heat it at 220 - 320 °C for 5 minutes to 4 hours in a protective atmosphere, add ethanol and / or cyclohexane after cooling, collect the precipitate by centrifugation, and disperse it in octadecene; The rare earth salt is selected from one or more of rare earth chlorides, rare earth nitrates, and rare earth acetates; The alkali metal compound is an alkali metal hydroxide or an alkali metal oleate; The solvent is selected from oleic acid, linoleic acid, ricinoleic acid, stearic acid, oleylamine, and octadecene.
5. The core-shell structured rare earth nano luminescent probe according to claim 1, wherein The preparation method of the core includes the following steps: Add a rare earth trifluoroacetate and an alkali metal trifluoroacetate to a solvent, heat it at 100 - 150 °C for 10 minutes to 2 hours; then, heat it at 220 - 320 °C for 5 minutes to 4 hours in a protective atmosphere, add ethanol and / or cyclohexane after cooling, collect the precipitate by centrifugation, and disperse it in octadecene; The solvent is selected from oleic acid, linoleic acid, ricinoleic acid, stearic acid, oleylamine, and octadecene.
6. A method for preparing the core-shell structured rare earth nano luminescent probe according to any one of claims 1 to 5, characterized in that, Heat the reaction solution with only the shell precursor to the reaction temperature, and then inject and add the core nanoparticle dispersion or the nanoparticle dispersion with a core and one or more shell layers.
7. The preparation method of the core-shell structured rare earth nano luminescent probe according to claim 6, characterized in that, The shell precursor includes a rare earth trifluoroacetate, a trifluoroacetate of an alkali metal or calcium. The solvent of the reaction solution is selected from oleic acid, linoleic acid, ricinoleic acid, stearic acid, oleylamine, and octadecene.
8. The preparation method of the core-shell structured rare earth nano luminescent probe according to claim 6, characterized in that, It includes the following steps: (1) Heat the reaction solution with only the shell precursor at 100 - 150 °C for 10 minutes to 2 hours; (2) Continue to heat it at 220 - 320 °C for 5 minutes to 4 hours in a protective atmosphere. After 0 to 15 minutes from the start of heating, inject and add the core nanoparticle dispersion or the nanoparticle dispersion with a core and one or more shell layers to the reaction solution. Add ethanol and / or cyclohexane after cooling, collect the precipitate by centrifugation, and disperse it in octadecene or cyclohexane.
9. The preparation method of the core-shell structured rare earth nano luminescent probe according to claim 6, characterized in that, The core nanoparticle dispersion or the nanoparticle dispersion with a core and one or more shell layers is subjected to anhydrous and anaerobic treatment before injection and then added to a syringe.
10. Use of the core-shell structured rare earth nanophosphor probe according to any one of claims 1 to 5, characterized in that, The nanoluminous probe is used for high-resolution biological imaging, small-scale temperature sensing, photothermal therapy, detection of metal ions or specific biomolecules and proteins.