Small-particle-size composite material, preparation method thereof and application of small-particle-size composite material in fluorescence imaging

Abstract

The invention relates to the technical field of luminescent composite nano materials, in particular to a small-particle-size composite material, a preparation method thereof and application of the small-particle-size composite material in fluorescence imaging. The small-particle-size composite material comprises carbon quantum dots and CsMnCl3 nanoparticles, the surfaces of the carbon quantum dots are modified with carboxyl groups, and the carbon quantum dots and the CsMnCl3 nanoparticles are connected through amido bonds formed by dehydration condensation of amino groups and carboxyl groups. The small-particle-size composite material provided by the invention has a blue light emission peak at the excitation wavelength of 360-400nm and the wavelength of 440-500nm, not only has higher fluorescence emission intensity and can be used as a fluorescent dye, but also can solve the problems, has temperature sensing performance and is wide in application range.

Description

Technical Field

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

[0002] The information disclosed in this background technology section is only intended to enhance the 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 a person skilled in the art.

[0003] Currently, nanomaterials have been used in many aspects of daily life, but for some special fields, existing nanomaterials are difficult to meet the requirements. Traditional fluorescent imaging materials, such as organic fluorescent dyes, have problems such as poor photostability and easy photobleaching. During long-term imaging, the signal attenuation is serious, affecting the accuracy of observation. Although some quantum dots have good fluorescence properties, they contain heavy metals and have biological toxicity, which limits their application in in vivo biological 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 and a preparation method thereof 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 problems and has temperature sensing performance and 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 surface of the carbon quantum dots is 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] The CsMnCl3 nanoparticles are reacted with polyethyleneimine in water to obtain CsMnCl3 nanoparticles with amino groups modified on the surface;

[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 dehydration condensation reaction of carboxyl groups and amino groups to obtain the nanoparticles.

[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 an obvious 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 in the specification, 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 is the X-ray diffraction pattern of the CsMnCl3 prepared in Example 1 of the present invention and the CsMnCl3-CDs nanoparticles prepared in Example 3;

[0021] Figure 5 1 is an emission spectrum diagram 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 It is a Fourier infrared absorption spectrum (FTIR) diagram of CDs prepared in Example 1 of the present invention, CsMnCl3-PEI and CsMnCl3-CDs prepared in Example 3;

[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 biological imaging of CsMnCl3-CDs nanoparticles prepared in Example 3 of the present invention;

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

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

[0027] Fig.11 This is a cell nucleus staining image of the CsMnCl3-CDs nanoparticles prepared in Example 3 of the present invention after the cells are stained with DAPI solution during biological imaging;

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

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

[0030] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those 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 exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0032] As described in the background technology, existing traditional fluorescent imaging materials have the problems of poor photostability and easy photobleaching. At present, there is an urgent need to develop a new type of nanomaterial with excellent photostability and low toxicity that can realize the needs of fluorescent imaging in vivo. In view of this, the present invention proposes a small-particle composite material and 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, and 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, CsMnCl3 nanoparticles are reacted with polyethyleneimine so that the surface of the CsMnCl3 nanoparticles is modified with amino groups.

[0035] The present invention does not impose any particular restrictions on 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, and 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] The CsMnCl3 nanoparticles are reacted with polyethyleneimine in water to obtain CsMnCl3 nanoparticles with amino groups modified on the surface;

[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 dehydration condensation reaction of carboxyl groups and amino groups to obtain the nanoparticles.

[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, and then the carboxyl groups 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, manganese acetate, octadecene, oleic acid, oleylamine, and acetic acid are mixed to carry out a solvent thermal reaction; then, under inert atmosphere conditions, the temperature is raised to 190-210°C and trimethylchlorosilane (TMCS) is added, and then the reaction is cooled in an ice bath and cooled to room temperature.

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

[0044] The present invention does not impose any special restrictions on the purification method of CsMnCl3 nanoparticles, and the 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 synthesized by the hydrothermal method commonly used in the art can be used. 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 the 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 in conjunction with 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 CH3COOCs and 0.2451 g (CH3COO)2Mn·4H2O into a four-necked flask, and add 10 mL octadecene, 2.5 mL oleic acid, 0.5 mL oleylamine, and 0.5 mL 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 and the temperature was raised to 200 °C. 0.4 mL of TMCS was rapidly injected. After 10 s, the reaction was cooled in an ice bath 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 the distribution is uniform. Figure 4 The X-ray diffraction diagram of this example shows that CsMnCl3 nanoparticles were successfully prepared. 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 drop 11.98 mL of ethanolamine (0.2 mol) aqueous solution 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 the 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 cyclohexane and 10 mL N,N-dimethylformamide (DMF) for 2 min.

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

[0068] (3) Centrifuge at 12000 r / min for 10 min, take 111 mg of precipitate (CsMnCl3), add 5 mL of DMF, and disperse evenly by sonication. Weigh 150 mg of PEI into a beaker, add 10 mL of DMF, sonicate, add 5 mL of CsMnCl3 dispersed in DMF, and stir overnight; centrifuge at 12000 r / min for 10 min, wash once, and disperse in 20 mL of water.

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

[0070] (5) Add 5 mL of the CsMnCl3-PEI solution dispersed in water prepared in (3), stir overnight, centrifuge at 12000 r / min for 15 min, wash once with water, and disperse 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. Under the 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 the CDs surface functional group 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 cyclohexane and 10 mL N,N-dimethylformamide (DMF) for 2 min.

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

[0076] (3) Centrifuge at 12000 r / min for 10 min, take 74 mg of precipitate (CsMnCl3), add 5 mL of DMF, and disperse it evenly by sonication. Weigh 100 mg of PEI into a beaker, add 10 mL of DMF, sonicate, add 5 mL of CsMnCl3 dispersed in DMF, stir overnight; centrifuge at 12000 r / min for 10 min, wash once, and disperse in 20 mL of water.

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

[0078] (5) Add 5 mL of the CsMnCl3-PEI solution dispersed in water prepared in (3), stir overnight, centrifuge at 12000 r / min for 15 min, wash once with water, and disperse 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 cyclohexane and 10 mL N,N-dimethylformamide (DMF) for 2 min.

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

[0083] (3) Centrifuge at 12000 r / min for 10 min, take 147 mg of precipitate (CsMnCl3), add 5 mL of DMF, and disperse it evenly by sonication. Weigh 200 mg of PEI into a beaker, add 10 mL of DMF, sonicate, add 5 mL of CsMnCl3 dispersed in DMF, stir overnight; centrifuge at 12000 r / min for 10 min, wash once, and disperse in 20 mL of water.

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

[0085] (5) Add 5 mL of the CsMnCl3-PEI solution dispersed in water prepared in (3), stir overnight, centrifuge at 12000 r / min for 15 min, wash once with water, and disperse 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 the 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 100 cells / well in a 96-well plate and incubated overnight in a 5% CO2, 37°C environment to ensure cell adhesion. 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 the CsMnCl3-CDs composite nanomaterials in cells.

[0091] Figure 8 This is the bright and dark field overlay image of the biological imaging of CsMnCl3-CDs nanoparticles prepared in Example 3. Fig. 9 For biological imaging bright field images, Fig.10 For biological imaging dark field images, Fig.11 This is a nuclear staining image of cells after being stained 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) taking the dried powder of CsMnCl3-CDs nanomaterial and placing it in a temperature measuring device;

[0095] (2) The temperature-variable device is heated, and the emission spectrum of the CsMnCl3-CDs composite nanomaterial is tested by a spectrometer under 365 nm 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 Fig.12 As shown, the excitation light source used is 365nm, 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 the 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 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 a corresponding pattern. Fig.13 The anti-counterfeiting image 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 irradiation. When irradiated with 365nm excitation light, the above nanoparticles can be used as the raw material of the anti-counterfeiting label, and the optical properties of the material are used to achieve anti-counterfeiting. Fig.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 the 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 CsMnCl3-CDs small-particle composite materials, and stir evenly until the mixed solution becomes a viscous colloid.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A small-particle composite material, characterized in that: The invention comprises carbon quantum dots and CsMnCl3 nanoparticles. 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 through amide bonds formed by dehydration condensation of the amino groups and the carboxyl groups.

2. The small-particle composite material according to claim 1, characterized in that: The CsMnCl3 nanoparticles react with polyethyleneimine so that the surface of the CsMnCl3 nanoparticles is modified with amino groups.

3. The small-particle composite material according to claim 1, characterized in that: The carbon quantum dots are obtained by hydrothermal synthesis of ethanolamine and citric acid; preferably, the molar ratio of ethanolamine to citric acid is 1.9-2.3:

1.

4. The small-particle composite material according to claim 1, characterized in that: 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: The CsMnCl3 nanoparticles are reacted with polyethyleneimine in water to obtain CsMnCl3 nanoparticles with amino groups modified on the surface; 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 dehydration condensation reaction of the carboxyl groups and the amino groups to obtain the nanoparticles.

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 to form amide bonds; preferably, the activation time is 1 to 2.5 hours.

7. The preparation method according to claim 5, characterized in that: The preparation process of CsMnCl3 nanoparticles is as follows: cesium acetate, manganese acetate, octadecene, oleic acid, oleylamine, and acetic acid are mixed to undergo a solvent thermal reaction; then, under inert atmosphere conditions, 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 nanoparticles; Preferably, the conditions of the solvent thermal synthesis reaction are: the temperature under vacuum is 110-130° C., preferably 120° C., the time is 0.5-2 h, preferably 0.5 h; the molar ratio of cesium acetate to manganese acetate is (0.9-1.1):(0.9-1.1), preferably 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 carbon quantum dots.

8. 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.

9. The fluorescent dye according to claim 8, characterized in that: The auxiliary materials include water and / or polyvinyl alcohol.

10. Use of the small-particle composite material according to any one of claims 1 to 4 or the fluorescent dye according to claim 8 or 9 in fluorescent imaging, temperature sensing or anti-counterfeiting.

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