A small-particle composite material, its preparation method, and its application in fluorescence imaging

Abstract

The present invention relates to the technical field of luminescent composite nanomaterials, and in particular to a small-particle composite material, a preparation method thereof, and its application in fluorescence imaging. The small-particle composite material comprises carbon quantum dots and CsMnCl3 nanoparticles. The carbon quantum dots are surface-modified with carboxyl groups, and the carbon quantum dots and CsMnCl3 nanoparticles are connected via an amide bond formed by dehydration condensation of amino groups and carboxyl groups. The small-particle composite material provided by the present invention exhibits a blue light emission peak at 440 to 500 nm under an excitation wavelength of 360 to 400 nm. It not only has high fluorescence emission intensity, making it suitable for use as a fluorescent dye, but also addresses the aforementioned issues and exhibits temperature sensing capabilities, thus providing a wide range of applications.

Description

Technical Field

[0001] The present invention relates to the technical field of luminescent composite nanomaterials, and in particular to a small-particle composite material, a preparation method thereof, and application thereof in fluorescence imaging. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Nanomaterials are already used in many aspects of daily life. However, existing nanomaterials struggle to meet the requirements of certain specialized applications. Traditional fluorescent imaging materials, such as organic fluorescent dyes, suffer from poor photostability and susceptibility to photobleaching. This leads to severe signal attenuation during long-term imaging, compromising observation accuracy. While some quantum dots exhibit excellent fluorescence properties, they contain heavy metals and are biotoxic, limiting their application in in vivo imaging. Summary of the Invention

[0004] In order to solve the problems of poor stability, easy photobleaching and biological toxicity in existing fluorescent imaging materials, the purpose of the present invention is to provide a small-particle composite material, its preparation method and its application in fluorescent imaging. The small-particle composite material provided by the present invention not only has a high fluorescence emission intensity and can be used as a fluorescent dye, but also can solve the above-mentioned problems and has temperature sensing performance, and has a wide range of applications.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] In a first aspect, a small-particle composite material comprises carbon quantum dots and CsMnCl3 nanoparticles, wherein the carbon quantum dots are surface-modified with carboxyl groups, and the carbon quantum dots and the CsMnCl3 nanoparticles are connected via amide bonds formed by dehydration condensation of amino groups and carboxyl groups.

[0007] In a second aspect, a method for preparing the above-mentioned small-particle composite material comprises the following steps:

[0008] CsMnCl3 nanoparticles were reacted with polyethyleneimine in water to obtain CsMnCl3 nanoparticles with surface modified amino groups;

[0009] The carbon quantum dots with carboxyl groups modified on the surface and the CsMnCl3 nanoparticles with amino groups modified on the surface are subjected to a dehydration condensation reaction of the carboxyl groups and the amino groups to obtain the product.

[0010] In a third aspect, a fluorescent dye comprises the above-mentioned small-particle composite material and auxiliary materials.

[0011] In a fourth aspect, the present invention provides applications of the above-mentioned small-particle composite material in fluorescence imaging, temperature sensing or anti-counterfeiting.

[0012] The beneficial effects of the present invention are:

[0013] (1) The small-particle composite material provided by the present invention has a small particle size and a high fluorescence emission intensity. Only a small amount of addition is required for mixing to produce a significant luminescence effect. The detection method is simple and can effectively reduce the industrial detection process.

[0014] (2) The small-particle composite material provided by the present invention has a simple preparation process and low cost, which is conducive to industrial large-scale production.

[0015] (3) The small-particle composite material prepared by the present invention can be used not only in bioluminescence imaging, but also in temperature sensing, anti-counterfeiting and other fields, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0017] Figure 1 is a transmission electron microscope (TEM) image of CsMnCl3 of Example 1 of the present invention;

[0018] Figure 2 is a transmission electron microscope (TEM) image of CDs prepared in Example 2 of the present invention;

[0019] Figure 3 is a scanning electron microscope (SEM) image of CsMnCl3-CDs nanoparticles prepared in Example 3 of the present invention;

[0020] Figure 4 1 is an X-ray diffraction pattern of CsMnCl3 prepared in Example 1 of the present invention and CsMnCl3-CDs nanoparticles prepared in Example 3;

[0021] Figure 5 1 is an emission spectrum of CsMnCl3 prepared in Example 1 of the present invention, CDs prepared in Example 2, and CsMnCl3-CDs prepared in Example 3;

[0022] Figure 6 FTIR spectra of CDs prepared in Example 1, CsMnCl3-PEI and CsMnCl3-CDs prepared in Example 3 of the present invention;

[0023] Figure 7 This is the emission spectrum of the diluted CDs (1:64) prepared in Example 2 of the present invention under 365nm laser excitation;

[0024] Figure 8 This is a bright field and dark field overlay image of the CsMnCl3-CDs nanoparticles biological imaging prepared in Example 3 of the present invention;

[0025] Figure 9 This is a bright field image of biological imaging of CsMnCl3-CDs nanoparticles prepared in Example 3 of the present invention;

[0026] Figure 10 This is a dark field image of biological imaging of CsMnCl3-CDs nanoparticles prepared in Example 3 of the present invention;

[0027] Figure 11 This is a nuclear staining image of cells stained with DAPI solution during bioimaging of CsMnCl3-CDs nanoparticles prepared in Example 3 of the present invention;

[0028] Figure 12 This is a linear fitting diagram of the CsMnCl3-CDs nanoparticles prepared in Example 3 of the present invention at 467 nm and temperature;

[0029] Figure 13 Anti-counterfeiting images of CDs prepared in Example 2 of the present invention and CsMnCl3-CDs nanoparticles prepared in Example 3 excited at 365nm. DETAILED DESCRIPTION

[0030] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0032] As described in the background, existing traditional fluorescent imaging materials suffer from poor photostability and susceptibility to photobleaching. There is an urgent need to develop novel nanomaterials with excellent photostability, low toxicity, and the ability to achieve in vivo fluorescent imaging. In light of this, the present invention proposes a small-particle composite material, its preparation method, and its application in fluorescent imaging.

[0033] A typical embodiment of the present invention provides a small-particle composite material, including carbon quantum dots and CsMnCl3 nanoparticles, wherein the surface of the CsMnCl3 nanoparticles is modified with amino groups, and the surface of the carbon quantum dots is modified with carboxyl groups. The carbon quantum dots and the CsMnCl3 nanoparticles are connected through amide bonds formed by dehydration condensation of amino groups and carboxyl groups.

[0034] In some embodiments, CsMnCl 3 nanoparticles are reacted with polyethyleneimine so that the surface of the CsMnCl 3 nanoparticles is modified with amino groups.

[0035] The present invention imposes no particular limitation on the carbon quantum dots. In some embodiments, the carbon quantum dots are obtained by hydrothermal synthesis of ethanolamine and citric acid. Specifically, the molar ratio of ethanolamine to citric acid is 1.9 to 2.3:1, preferably 2:1. The synthesized carbon quantum dots have good luminescence properties.

[0036] In some embodiments, the mass ratio of carbon quantum dots to CsMnCl3 nanoparticles is 58.0-72.0:1.

[0037] In some embodiments, the small-particle composite material has a blue light emission peak at 450-550 nm under an excitation wavelength of 360-400 nm.

[0038] A second embodiment of the present invention provides a method for preparing the above-mentioned small-particle composite material, comprising the following steps:

[0039] CsMnCl3 nanoparticles were reacted with polyethyleneimine in water to obtain CsMnCl3 nanoparticles with surface modified amino groups;

[0040] The carbon quantum dots with carboxyl groups modified on the surface and the CsMnCl3 nanoparticles with amino groups modified on the surface are subjected to a dehydration condensation reaction of the carboxyl groups and the amino groups to obtain the product.

[0041] In some embodiments, during the dehydration condensation reaction, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) are added to activate the carboxyl groups on the surface of the carbon quantum dots, which then react with the amino groups to form amide bonds. Specifically, the activation time is 1 to 2.5 hours.

[0042] In some embodiments, the preparation process of CsMnCl3 nanoparticles is as follows: cesium acetate and manganese acetate are mixed with octadecene, oleic acid, oleylamine, and acetic acid to undergo a solvothermal reaction; then, under inert atmosphere, the temperature is raised to 190-210°C and trimethylchlorosilane (TMCS) is added, and the reaction is cooled in an ice bath and cooled to room temperature.

[0043] Specifically, the conditions for the solvent thermal synthesis reaction are: a temperature of 110-130° C., preferably 120° C., and a reaction time of 0.5-2 h, preferably 0.5 h, under vacuum; and a molar ratio of cesium acetate to manganese acetate of (0.9-1.1):(0.9-1.1), preferably 1:1.

[0044] The present invention does not impose any particular limitation on the purification method of CsMnCl3 nanoparticles, and a common purification method in the art can be used. The purification method of the present invention is to centrifuge the liquid after the reaction and wash it with cyclohexane.

[0045] The present invention does not impose any special restrictions on the preparation method of carbon quantum dots, and the preparation method of carbon quantum dots can be prepared by the hydrothermal method for synthesizing carbon quantum dots commonly used in the art. In some embodiments, the preparation process of carbon quantum dots is as follows: ethanolamine and citric acid are subjected to a hydrothermal synthesis reaction at 170 to 190°C for 5 to 7 hours. Specifically, ethanolamine is added dropwise to an aqueous solution of citric acid, stirred vigorously until clear, and then a hydrothermal synthesis reaction is carried out. The hydrothermal synthesis reaction described in the present invention refers to a synthesis reaction carried out under closed conditions, using water as a solvent, heating the reaction system to a high-pressure state, and performing the reaction in this state. The temperature of the hydrothermal synthesis reaction is preferably 180°C. The time of the hydrothermal synthesis reaction is preferably 6 hours.

[0046] A third embodiment of the present invention provides a fluorescent dye comprising the above-mentioned small-particle composite material and auxiliary materials.

[0047] In some embodiments, the auxiliary materials include water and / or polyvinyl alcohol.

[0048] A fourth embodiment of the present invention provides an application of the above-mentioned small-particle composite material or fluorescent dye in fluorescence imaging, temperature sensing or anti-counterfeiting.

[0049] The small-particle composite material prepared by the present invention can realize blue fluorescence emission under the excitation of 365nm excitation light, and the diluted CDs (1:64) can realize yellow fluorescence emission under the excitation of 365nm excitation light, thereby realizing anti-counterfeiting function; after the small-particle composite material is incubated with cells for 2 hours, the composite nanomaterial will enter the cells, thereby realizing intracellular fluorescence imaging.

[0050] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0051] The reagents used in the following examples are all commercially available products known to those skilled in the art.

[0052] Example 1

[0053] This embodiment provides the preparation of CsMnCl3, comprising the following steps:

[0054] (1) Weigh 0.1919 g of CH3COOCs and 0.2451 g of (CH3COO)2Mn·4H2O into a four-necked flask, then add 10 mL of octadecene, 2.5 mL of oleic acid, 0.5 mL of oleylamine, and 0.5 mL of acetic acid.

[0055] (2) The above mixture was reacted at 120°C under vacuum for 30 min and stirred until the reactants were dissolved.

[0056] (3) Nitrogen was introduced, the temperature was raised to 200°C, 0.4 mL of TMCS was rapidly injected, and the reaction was cooled in an ice bath after 10 s, and the solution was cooled to room temperature.

[0057] (4) Centrifuge at 8000 r / min for 10 min, discard the supernatant, disperse the precipitate in 10 mL of cyclohexane, and centrifuge at 10000 r / min for 10 min. Keep the supernatant and discard the precipitate.

[0058] Figure 1 This is a transmission image of CsMnCl3 in this example, which shows that the particle size of CsMnCl3 is small and uniformly distributed. Figure 4 The X-ray diffraction pattern of this embodiment shows that CsMnCl3 nanoparticles were successfully prepared. The emission spectrum of CsMnCl3 was measured, as shown in FIG. Figure 5 As shown, the emission peak is at 471 nm and the excitation light source used is 365 nm.

[0059] Example 2

[0060] This embodiment provides the preparation of CDs, comprising the following steps:

[0061] (1) Weigh 19.21 g (0.1 mol) of citric acid into a beaker, add 20 mL of water and stir evenly to obtain a 5 mol / L citric acid aqueous solution. Then, add 11.98 mL of ethanolamine (0.2 mol) aqueous solution dropwise into the citric acid aqueous solution and stir vigorously until the solution is clear.

[0062] (2) The clear solution was placed in a high-pressure reactor, reacted at 180°C for 6 h, and naturally cooled to room temperature to obtain a reddish-brown liquid, i.e., a CDs aqueous solution (concentration of 2.5705 g / mL).

[0063] Figure 2 This is a transmission image of the carbon dots prepared in this example. The particle size is small and the distribution is uniform. Take 0.1 mL of CDs aqueous solution, add 6.4 mL of water to dilute (1:64), and measure its emission spectrum. Figure 7 As shown, the emission peak is at 571 nm.

[0064] Example 3

[0065] This example provides the preparation of CsMnCl3-CDs nanoparticles, and the specific steps are as follows:

[0066] (1) Take a 50 mL centrifuge tube, add 6 mL of cyclohexane and 10 mL of N,N-dimethylformamide (DMF) for 2 minutes.

[0067] (2) Add 400 mg of nitrosotetrafluoroborate and stir for 10 minutes. Add 5 mL of CsMnCl3 dispersed in cyclohexane and stir for about 40 minutes. After stirring, irradiate with a laser. If the upper part glows, continue stirring.

[0068] (3) Centrifuge at 12,000 rpm for 10 min, take 111 mg of the precipitate (CsMnCl3), add 5 mL of DMF, and sonicate to disperse it evenly. Weigh 150 mg of PEI into a beaker, add 10 mL of DMF, sonicate, add 5 mL of DMF-dispersed CsMnCl3, and stir overnight; centrifuge at 12,000 rpm for 10 min, wash once, and disperse in 20 mL of water.

[0069] (4) Weigh 40 mg of EDS and 20 mg of NHS, add 5 mL of diluted carbon dot solution (volume ratio of 1:128), and stir for 2 h.

[0070] (5) 5 mL of the CsMnCl3-PEI solution dispersed in water prepared in (3) was added, stirred overnight, centrifuged at 12000 rpm for 15 min, washed once, and dispersed in 20 mL of water to obtain an aqueous solution of CsMnCl3-CDs nanoparticles (8.244 mg / mL).

[0071] Figure 3 This is a scanning electron microscope image of the CsMnCl3-CDs nanoparticles prepared in this example. Figure 5 This is the emission spectrum of CsMnCl3-CDs and carbon dots prepared in this example under 365 nm excitation. At an excitation wavelength of 365 nm, the emission peak of CsMnCl3-CDs is 468 nm, and the emission peak of CDs is 458 nm, emitting blue light. Figure 6 The Fourier transform infrared absorption spectra (FTIR) of activated CDs, CsMnCl3-PEI and CsMnCl3-CDs prepared in Example 3 are shown in FIG. Figure 6 It can be seen that the absorption peak of CDs surface functional groups is 1704 cm -1 The absorption peak of the surface functional group of CsMnCl3-PEI is 1465 cm -1 、2917cm -1The absorption peak of the surface functional group of CsMnCl3-CDs is 1657 cm -1 , the existence of amide bonds indicates the successful connection between nanoparticles CsMnCl3 and carbon dots.

[0072] Example 4

[0073] This example provides the preparation of CsMnCl3-CDs nanoparticles, and the specific steps are as follows:

[0074] (1) Take a 50 mL centrifuge tube, add 6 mL of cyclohexane and 10 mL of N,N-dimethylformamide (DMF) for 2 minutes.

[0075] (2) Add 400 mg of nitrosotetrafluoroborate and stir for 10 minutes. Add 5 mL of CsMnCl3 dispersed in cyclohexane and stir for about 40 minutes. After stirring, irradiate with a laser. If the upper part glows, continue stirring.

[0076] (3) Centrifuge at 12,000 rpm for 10 min, take 74 mg of the precipitate (CsMnCl3), add 5 mL of DMF, and sonicate to disperse it evenly. Weigh 100 mg of PEI into a beaker, add 10 mL of DMF, sonicate, add 5 mL of DMF-dispersed CsMnCl3, and stir overnight; centrifuge at 12,000 rpm for 10 min, wash once, and disperse in 20 mL of water.

[0077] (4) Weigh 40 mg of EDS and 20 mg of NHS, add 5 mL of diluted carbon dot solution (volume ratio of 1:128), and stir for 2 h.

[0078] (5) 5 mL of the CsMnCl3-PEI solution dispersed in water prepared in (3) was added, stirred overnight, centrifuged at 12000 rpm for 15 min, washed once, and dispersed in 20 mL of water to obtain an aqueous solution of CsMnCl3-CDs nanoparticles (7.7815 mg / mL).

[0079] Example 5

[0080] This example provides the preparation of CsMnCl3-CDs nanoparticles, and the specific steps are as follows:

[0081] (1) Take a 50 mL centrifuge tube, add 6 mL of cyclohexane and 10 mL of N,N-dimethylformamide (DMF) for 2 minutes.

[0082] (2) Add 400 mg of nitrosotetrafluoroborate and stir for 10 minutes. Add 5 mL of CsMnCl3 dispersed in cyclohexane and stir for about 40 minutes. After stirring, irradiate with a laser. If the upper part glows, continue stirring.

[0083] (3) Centrifuge at 12,000 rpm for 10 min, remove 147 mg of the precipitate (CsMnCl3), add 5 mL of DMF, and sonicate to disperse it evenly. Weigh 200 mg of PEI into a beaker, add 10 mL of DMF, sonicate, add 5 mL of DMF-dispersed CsMnCl3, and stir overnight; centrifuge at 12,000 rpm for 10 min, wash once, and disperse in 20 mL of water.

[0084] (4) Weigh 40 mg of EDS and 20 mg of NHS, add 5 mL of diluted carbon dot solution (volume ratio of 1:128), and stir for 2 h.

[0085] (5) 5 mL of the CsMnCl3-PEI solution dispersed in water prepared in (3) was added, stirred overnight, centrifuged at 12000 rpm for 15 min, washed once, and dispersed in 20 mL of water to obtain an aqueous solution of CsMnCl3-CDs nanoparticles (8.694 mg / mL).

[0086] Application Example 1

[0087] The materials in Example 3 were used in a fluorescence imaging experiment, and the specific steps were as follows:

[0088] (1) The prepared CsMnCl3-CDs composite nanomaterial (5 mL) was sterilized by ultraviolet light and dispersed in 15 mL of Hela cell culture medium DMEM.

[0089] (2) HeLa cells were cultured at 5×10 3 The cells were seeded at a density of 1000 μg / well in a 96-well plate and incubated overnight in a 5% CO2, 37°C environment to ensure cell attachment. 200 μL of DMEM culture medium containing CsMnCl3-CDs composite nanomaterials was added to each well and incubated for 2 h.

[0090] (3) The cells were fixed with 4% paraformaldehyde, and the bright field and ultraviolet channels of an inverted fluorescence microscope were used to respectively achieve bright field imaging of Hela cells and fluorescence imaging of CsMnCl3-CDs composite nanomaterials in cells.

[0091] Figure 8 This is the bright field and dark field overlay of the CsMnCl3-CDs nanoparticles bioimaging prepared in Example 3. Figure 9 For biological imaging bright field images, Figure 10 For biological imaging dark field images, Figure 11 This is a nuclear staining image of cells after staining with DAPI solution, indicating the fluorescence properties of CsMnCl3-CDs composite nanomaterials in cell imaging.

[0092] Application Example 2

[0093] The material in Example 3 was used in a temperature sensing experiment, and the specific steps were as follows:

[0094] (1) Place the dried powder of CsMnCl3-CDs nanomaterial in a temperature measuring device;

[0095] (2) The temperature-variable device is heated, and the emission spectrum of the CsMnCl3-CDs composite nanomaterial is measured using a spectrometer under 365nm laser irradiation to obtain a curve of the emission spectrum changing with temperature. This curve can then be used to calculate the temperature of the environment in which the composite material is located, such as Figure 12 As shown, the excitation light source used is 365 nm, indicating that the fluorescence emission intensity of the CsMnCl3-CDs composite nanomaterial decreases with increasing temperature.

[0096] Application Example 3

[0097] The materials in Example 3 were used in an anti-counterfeiting experiment, and the specific steps were as follows:

[0098] (1) Weigh 0.1 g of polyvinyl alcohol, add 7 mL of an aqueous solution containing dispersed CsMnCl3-CDs small-particle composite materials, and stir evenly until the mixed solution becomes a viscous colloid.

[0099] (2) Prepare black cardboard, cover it with a hollow label of appropriate size, apply the colloid obtained above, dry it and remove the hollow label to obtain the corresponding pattern. Figure 13 The anti-counterfeiting pattern of the CsMnCl3-CDs small-particle composite material prepared in Example 3 and the diluted carbon dots (1:64) prepared in Example 2 under 365nm excitation light. When irradiated with 365nm excitation light, the above nanoparticles can be used as the raw material of the anti-counterfeiting label, using the optical properties of the material to achieve anti-counterfeiting. Figure 13 The outermost shell pattern is yellow, and the inner pattern is blue.

[0100] Application Example 4

[0101] The materials in Example 3 were used in an anti-counterfeiting experiment, and the specific steps were as follows:

[0102] (1) Weigh 0.2 g of polyvinyl alcohol, add 7 mL of an aqueous solution containing dispersed CsMnCl3-CDs small-particle composite materials, and stir evenly until the mixed solution becomes a viscous colloid.

[0103] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A small-particle composite material, characterized in that: The method comprises carbon quantum dots and CsMnCl3 nanoparticles, wherein the surfaces of the CsMnCl3 nanoparticles are modified with amino groups, the surfaces of the carbon quantum dots are modified with carboxyl groups, and the carbon quantum dots and the CsMnCl3 nanoparticles are connected via amide bonds formed by dehydration condensation of the amino groups and the carboxyl groups; The preparation process of the CsMnCl3 nanoparticles is as follows: cesium acetate and manganese acetate are mixed with octadecene, oleic acid, oleylamine, and acetic acid to undergo a solvothermal reaction; then, under inert atmosphere, the temperature is raised to 190-210°C and trimethylsilyl chloride is added, followed by cooling the reaction in an ice bath and cooling to room temperature to obtain the obtained particles. The CsMnCl3 nanoparticles react with polyethyleneimine so that the surfaces of the CsMnCl3 nanoparticles are modified with amino groups.

2. The small-particle composite material according to claim 1, wherein: The carbon quantum dots are obtained by hydrothermal synthesis of ethanolamine and citric acid.

3. The small-particle composite material according to claim 1, wherein: The molar ratio of ethanolamine to citric acid is 1.9-2.3:

1.

4. The small-particle composite material according to claim 1, wherein: The mass ratio of carbon quantum dots to CsMnCl3 nanoparticles is 58.0~72.0:

1.

5. A method for preparing the small-particle composite material according to claim 1, characterized in that: The steps include: CsMnCl3 nanoparticles were reacted with polyethyleneimine in water to obtain CsMnCl3 nanoparticles with surface modified amino groups; The carbon quantum dots with carboxyl groups modified on the surface and the CsMnCl3 nanoparticles with amino groups modified on the surface are subjected to a dehydration condensation reaction of the carboxyl groups and the amino groups to obtain the product.

6. The preparation method according to claim 5, characterized in that: During the dehydration condensation reaction, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide are added to activate the carboxyl groups on the surface of the carbon quantum dots, and then the carboxyl groups react with the amino groups modified on the surface of the CsMnCl3 nanoparticles to form amide bonds.

7. The preparation method according to claim 6, wherein the carboxyl activation time is 1 to 2.5 hours.

8. The preparation method according to claim 5, characterized in that: The solvothermal reaction conditions for the preparation of CsMnCl3 nanoparticles are: a temperature of 110-130°C under vacuum, a reaction time of 0.5-2 hours, and a molar ratio of cesium acetate to manganese acetate of (0.9-1.1):(0.9-1.1). Alternatively, the preparation process of carbon quantum dots is as follows: ethanolamine and citric acid are subjected to a hydrothermal synthesis reaction at 170-190° C. for 5-7 hours to obtain the obtained carbon quantum dots.

9. The preparation method according to claim 8, wherein the solvent thermal synthesis reaction conditions during the preparation of CsMnCl3 nanoparticles are: a temperature of 120°C under vacuum.

10. The preparation method according to claim 8, wherein the solvent thermal synthesis reaction conditions during the preparation of CsMnCl3 nanoparticles are: vacuum time for 0.5 h.

11. The preparation method according to claim 8, wherein the conditions for the solvothermal synthesis reaction in the preparation process of CsMnCl3 nanoparticles are: the molar ratio of cesium acetate to manganese acetate is 1:

1.

12. A fluorescent dye, characterized in that: The invention comprises the small-particle composite material and auxiliary materials as described in any one of claims 1 to 4.

13. The fluorescent dye according to claim 12, wherein The auxiliary materials include water and / or polyvinyl alcohol.

14. Use of the small-particle composite material according to any one of claims 1 to 4 or the fluorescent dye according to claim 12 or 13 in fluorescence imaging, temperature sensing or anti-counterfeiting.

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