Fluorescence intensity enhanced aggregation-induced emission carbon dots, preparation method and application

Abstract

The invention discloses a preparation method of fluorescence intensity enhanced aggregation-induced emission carbon dots, which comprises the following steps: dissolving 2, 2-dithiobenzoic acid in acetic acid, and uniformly stirring and mixing to obtain a mixed solution; sequentially adding PEG (Polyethylene Glycol) and triethylamine into the mixed solution, uniformly stirring, heating and reacting to obtain a carbon dot solution; and cooling the carbon dot solution to room temperature, standing, removing supernate, washing and drying to obtain the fluorescence intensity enhanced aggregation-induced emission carbon dots (AIE-CDs). 2, 2-dithiodibenzoic acid is used as a raw material to prepare AIE-CDs, PEG is introduced as a passivating agent, the fluorescence intensity of the prepared AIE-CDs can be remarkably improved, the problem that the traditional AIE-CDs are low in luminous efficiency in an aggregation state is solved, meanwhile, the hydrophobicity of the AIE-CDs is improved through PEG modification, the AIE-CDs have better stability and dispersity in a biological environment, and the application range of the AIE-CDs is widened. And an ideal fluorescent marker is provided for cell imaging.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of materials, in particular to an aggregation-induced emission carbon dot with enhanced fluorescence intensity, a preparation method and application. BACKGROUND

[0002] In recent years, carbon dots (CDs) have attracted extensive attention due to their excellent fluorescence and electronic properties, such as achieving ultra-high fluorescence quantum yield, very narrow half-peak width, ultra-long room temperature phosphorescence, and the like. These fascinating luminescent properties open up a wide range of potential application fields for CDs, including optoelectronic devices, solar cells, biomedical and other fields. However, due to the accumulation of π-π conjugated systems or excessive resonance energy transfer, most CDs can emit bright fluorescence in solution state, but when they are processed into solid powders, the aggregation-induced quenching (ACQ) effect caused by aggregation often occurs, resulting in fluorescence quenching, which greatly limits the application of CDs in biological imaging and analysis.

[0003] To solve the ACQ effect of CDs in the aggregation state, researchers have proposed various methods. The Chinese patent document with publication number CN108455564A discloses a method for preparing yellow or green carbon dots, comprising the following steps: (1) dispersing a carbon source, a passivation agent and a reducing agent in ultrapure water, then stirring under the protection of a protective gas to obtain a mixed solution; (2) heating the mixed solution obtained in step (1) in a reaction container to obtain a carbon dot solution; (3) directly placing the carbon dot solution obtained in step (2) in an ultrafiltration tube or mixing it with an organic reagent, then centrifuging and drying to obtain solid carbon dots. Based on the synergistic effect of the passivation agent and the reducing agent, the prepared carbon dots have enhanced fluorescence intensity.

[0004] Therefore, during the preparation of CDs, a surface passivation agent (such as PEG, etc.) is introduced, which isolates the carbon dot luminophore through the steric hindrance effect of the flexible long chain of PEG, prevents the formation of dense π-π stacking in the aggregation state (avoids the formation of quenching type H-aggregates), and passivates the carbon dot surface defect state using the terminal functional groups (such as -NH2 / -OH) to reduce non-radiative recombination centers and form a hydrophilic solvation layer to shield environmental quenching factors (such as O2 / H2O), finally converting the traditional ACQ tight quenching state into a loose radiation dominant state (such as J-aggregates or restricted aggregates), forcing the excitation energy to release through radiation transition, and realizing the abnormal enhancement of fluorescence in aggregation. Or, CDs are loaded on the surface of particles, polymer matrix, etc., and the CDs obtained by the above method can effectively inhibit the ACQ effect, but cannot reverse the aggregation-induced quenching phenomenon of carbon dots.

[0005] Tang et al. discovered the aggregation-induced emission (AIE) phenomenon in hexaphenylsilole in 2001 (Luo Jingdong, et al. Aggregation-induced emission of 1-methyl-1,2,3,4,5-pentaphenylsilole, Chem Commun, 2001, (18) 1740-1. DOI: 10.1039 / B105159H.), contrary to the traditional ACQ phenomenon, the molecules with AIE characteristics do not emit light or emit weak fluorescence in the single molecular dispersion state; while in the aggregated state or solid state, they have a phenomenon of significant fluorescence enhancement. Unlike the planar conjugated ACQ fluorescent molecules, AIE molecules usually have a helical or twisted spatial structure, so that the intramolecular free rotation (RIR) is restricted in space in the aggregated state, thereby reducing the energy loss of the non-radiative decay process, significantly improving the efficiency of radiative transition, and showing strong fluorescence emission. Therefore, by introducing a strong rigid structure into the CDs, CDs with aggregation-induced emission characteristics can be obtained.

[0006] Cell imaging requires that the fluorescent nanoprobes have good water dispersibility, light stability, high definition and biocompatibility. As a new member of the carbon dot material family, aggregation-induced emission carbon dots (AIE-CDs) have attracted much attention due to their aggregation-induced emission optical properties and simple preparation process. Unlike metal-doped inorganic quantum dots, AIE-CDs have no risk of heavy metal ion leakage, and compared with traditional carbon dots that enhance fluorescence intensity by using a passivation agent, traditional carbon dots are not true aggregation-induced emission materials and cannot exhibit aggregation-induced emission characteristics. Therefore, AIE-CDs have the potential to improve the sensitivity of biological imaging and are ideal fluorescent markers for cell imaging.

[0007] Currently, research in this field mainly focuses on the control of the emission wavelength of AIE-CDs, while there is less research on enhancing the fluorescence emission, hydrophilicity and stability in biological environments of AIE-CDs. Moreover, the luminescent efficiency of traditional AIE-CDs in the aggregated state is low. Therefore, it is urgent to find a preparation method of AIE-CDs with enhanced fluorescence intensity, which can be applied to cell imaging technology and improve the sensitivity and accuracy of cell imaging. SUMMARY

[0008] To solve the above technical problems, the present application provides a preparation method of aggregation-induced emission carbon dots with enhanced fluorescence intensity, which introduces PEG as a passivation agent to significantly improve the fluorescence intensity of the prepared AIE-CDs, solving the problem of low luminescent efficiency of traditional AIE-CDs in the aggregated state.

[0009] A preparation method of an aggregation-induced emission enhancement carbon dot, comprising the following steps: (1) 2,2-dithiodibenzoic acid (DTSA) is dissolved in acetic acid, and after stirring and mixing uniformly, a mixed solution is obtained; (2) PEG and triethylamine are sequentially added to the mixed solution, and after stirring and heating and reaction, a carbon dot solution is obtained; (3) After the carbon dot solution is cooled to room temperature, it is poured into boiling water, and after standing, the supernatant is removed, the precipitate is washed and dried, and an aggregation-induced emission enhancement carbon dot with enhanced fluorescence intensity is obtained.

[0010] In the application, 2,2-dithiodibenzoic acid is used as a raw material to prepare AIE-CDs, PEG is introduced as a passivation agent, the intramolecular motion of the carbon dot luminescent group is limited by the steric hindrance of the flexible long chain of PEG, the non-radiative energy dissipation channel is reduced in the aggregated state, and the end functional groups (such as -NH2 / -OH) passivate the surface defect state, repair the energy trap, and form a hydrophilic shield to isolate the environmental quenching factor, forcing the excitation energy to be efficiently released through radiation transition, thereby significantly amplifying the AIE effect. Therefore, the addition of PEG can significantly improve the fluorescence intensity of AIE-CDs, solving the problem of low luminescent efficiency of traditional AIE-CDs in the aggregated state.

[0011] Preferably, in step (1), the concentration of 2,2-dithiodibenzoic acid in acetic acid is 10-40 mg / mL.

[0012] Preferably, in step (2), the molecular weight of PEG is 200-600.

[0013] In the application, as the molecular weight of PEG increases, the fluorescence intensity of the prepared AIE-CDs first increases and then decreases, and when the molecular weight of PEG is controlled within the above range, the functional groups on the surface of the carbon dots can interact with each other to form a stable passivation layer, reduce the surface defect state, and enhance the fluorescence emission.

[0014] Preferably, the volume ratio of PEG to acetic acid is 0.05-0.4:1.

[0015] In the application, as the volume ratio of PEG in the mixed solution gradually increases, the fluorescence intensity of the prepared AIE-CDs first increases and then decreases, and when the volume ratio of PEG is controlled within the above range, the defect state on the surface of the carbon dots can be effectively repaired, the quantum confinement effect is enhanced, and the fluorescence intensity is significantly improved. If the volume ratio of PEG is too large, the excess PEG may form a too thick passivation layer on the surface of the carbon dots, which will increase the scattering and absorption of photons inside the carbon dots, resulting in a decrease in fluorescence intensity.

[0016] Further preferably, the PEG has a molecular weight of 400-600, and the volume ratio of PEG to acetic acid is 0.1-0.2:1.

[0017] Preferably, in step (2), the volume ratio of triethylamine to the mixed solution is 0.02-0.23:1.

[0018] Preferably, in step (2), the heating reaction is carried out at a temperature of 180-210 ℃ for 8-12 h.

[0019] The application also provides the AIE-CDs with enhanced fluorescence intensity prepared by the above preparation method.

[0020] Preferably, the AIE-CDs with enhanced fluorescence intensity have the characteristics of aggregation-induced emission red light enhancement and red shift.

[0021] Preferably, the AIE-CDs with enhanced fluorescence intensity, in an aggregated state, present red fluorescence of different fluorescence intensities after excitation light irradiation; and in a dispersed state, present blue fluorescence after excitation light irradiation.

[0022] In the application, in an acetic acid water system, with the increase of the volume fraction of the poor solvent water, the AIE-CDs gradually aggregate and precipitate as nanoparticles, and the emission of blue light in the dispersed state and the emission of enhanced red light in the aggregated state can be observed.

[0023] The application also provides the application of the AIE-CDs with enhanced fluorescence intensity in cell imaging.

[0024] Preferably, the AIE-CDs with enhanced fluorescence intensity are used to distinguish 4T1 cells and Jurkat cells.

[0025] In the application, the modification of PEG also improves the hydrophobicity of AIE-CDs, so that the AIE-CDs have better stability and dispersibility in a biological environment, and are successfully used to distinguish 4T1 cells and Jurkat cells, thereby providing an ideal fluorescent marker for cell imaging, and hopefully improving the sensitivity and accuracy of biological imaging.

[0026] Compared with the prior art, the application has the following beneficial effects: By introducing PEG as a passivating agent, the application can significantly improve the fluorescence intensity of the prepared AIE-CDs, solve the problem of low light-emitting efficiency of traditional AIE-CDs in an aggregated state, and improve the hydrophobicity of AIE-CDs, so that the AIE-CDs have better stability and dispersibility in a biological environment, are successfully used to distinguish 4T1 cells and Jurkat cells, thereby providing an ideal fluorescent marker for cell imaging, and hopefully improving the sensitivity and accuracy of biological imaging. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Photos of the fluorescent intensity enhanced AIE-CDs prepared in Example 2 in solid state and in water under daylight and 365 nm UV light irradiation, respectively.

[0028] Figure 2 Infrared spectrum of the fluorescent intensity enhanced AIE-CDs prepared in Example 2.

[0029] Figure 3 UV-Vis absorption spectrum of the fluorescent intensity enhanced AIE-CDs prepared in Example 2.

[0030] Figure 4 Fluorescence emission spectra of the fluorescent intensity enhanced AIE-CDs prepared in Example 2 under different excitation wavelengths.

[0031] Figure 5 Optimal excitation and emission spectra of the fluorescent intensity enhanced AIE-CDs prepared in Example 2.

[0032] Figure 6 Fluorescence emission spectra of the fluorescent intensity enhanced AIE-CDs prepared in Example 2 and AIE-CDs prepared in Comparative Example 1 under 560 nm excitation wavelength.

[0033] Figure 7 Photos of the fluorescent intensity enhanced AIE-CDs prepared in Example 2 dispersed in different solvents under daylight and 365 nm UV light irradiation.

[0034] Figure 8 Fluorescence emission spectra of the fluorescent intensity enhanced AIE-CDs prepared in Example 2 dispersed in different solvents under 560 nm excitation wavelength.

[0035] Figure 9 Photos of the fluorescent intensity enhanced AIE-CDs prepared in Example 2 dispersed in acetic acid solutions with different water contents under daylight and 365 nm UV light irradiation.

[0036] Figure 10 Fluorescence emission intensity change line graph of the fluorescent intensity enhanced AIE-CDs prepared in Example 2 dispersed in acetic acid solutions with different water contents at 448 nm and 604 nm peak positions.

[0037] Figure 11 Fluorescence emission spectra of AIE-CDs prepared in Comparative Example 1, Examples 1-3.

[0038] Figure 12The fluorescence emission spectrum of the AIE-CDs prepared for Comparative Example 1, Example 2, and Examples 4-8.

[0039] Figure 13 The fluorescence imaging diagram of the AIE-CDs prepared for Example 2 in 4T1 cells and Jurkat cells. DETAILED DESCRIPTION

[0040] The application will be further described in detail below with reference to examples, but the embodiments of the application are not limited to the following examples.

[0041] The raw materials used in the application are commercially available.

[0042] Example 1 (1) 122 mg of 2,2-dithiodibenzoic acid (DTSA) was dissolved in 10 mL of acetic acid, stirred at room temperature for 1 h, and a milky white mixed solution was obtained after uniform mixing; (2) 200 μL of PEG-200 was added to the milky white mixed solution, stirred for 30 min, and then 112 μL of triethylamine was continuously added, stirred for 30 min, and then transferred to a 25 mL stainless steel reactor, heated at 200 ℃ for 10 h, and a carbon dot solution was obtained; (3) The carbon dot solution was cooled to room temperature, poured into 250 mL of boiling water, and ultrasonically treated for 5 min, and then the precipitate was allowed to stand and separate, the supernatant was removed, resuspended with water, and centrifuged at 11000 rpm, and the washing was repeated three times, and then freeze-dried to obtain the AIE-CDs with enhanced fluorescence intensity.

[0043] Examples 2-8 The preparation method is the same as that of Example 1, and the differences are shown in the following table.

[0044] Table 1: Differences in preparation methods of Examples 1-8

[0045] Comparative Example 1 The preparation method is the same as that of Example 1, and the difference is only that no PEG is added as a dopant to obtain AIE-CDs.

[0046] Sample Analysis The AIE-CDs with enhanced fluorescence intensity prepared in Example 2 were characterized and analyzed for optical properties.

[0047] Figure 1The photos of the fluorescence intensity enhanced AIE-CDs prepared in Example 2 under sunlight and 365 nm ultraviolet light irradiation respectively when the AIE-CDs are in solid state and in water are shown in the figure, the fluorescence intensity enhanced AIE-CDs prepared in Example 2 present reddish brown under sunlight when in dry solid powder state, and the solid powder can emit bright red fluorescence under 365 nm ultraviolet light irradiation, while the AIE-CDs powder is added into pure water, the carbon dots powder presents suspended and dispersed state in pure water, and settles after standing for a while, and can also emit bright red fluorescence under 365 nm ultraviolet excitation.

[0048] Figure 2 The infrared absorption spectrum of the fluorescence intensity enhanced AIE-CDs prepared in Example 2, wherein, the absorption peak at 3500~2900 cm -1 corresponds to the stretching vibration of O-H chemical bond in carboxyl group, the absorption peak at 3427 cm -1 corresponds to the stretching vibration of N-H. The absorption peak at 2655 cm -1 corresponds to the stretching vibration of S-H bond in raw material DTSA, the strong absorption at 1681 cm -1 corresponds to the stretching vibration of amide bond, and the absorption at 1260 cm -1 corresponds to the stretching vibration of C-N bond. In addition, the absorption at 551 cm -1 corresponds to the S-S bond absorption in raw material DTSA, and the absorption at 693 cm -1 corresponds to the stretching vibration of C-S bond.

[0049] Figure 3 The ultraviolet-visible absorption spectrum of the fluorescence intensity enhanced AIE-CDs prepared in Example 2 is shown in the figure, the three absorption peaks at 219 nm, 254 nm and 326 nm are relatively strong, which mainly correspond to the π-π * electronic transition of C=C group in the carbon core of Example 2. Different from the three absorption peaks, Example 2 not only presents relatively wide ultraviolet absorption characteristics in the visible light wavelength range (370~530 nm), but also has a wide absorption peak at 420 nm and a strong absorption peak at 550 nm, which is mainly due to the wide absorption characteristics of the surface state of the material, indicating that the fluorescence emission of AIE-CDs is determined by the core and the surface state.

[0050] Figure 4The fluorescence emission spectra of the fluorescence intensity enhanced AIE-CDs prepared in Example 2 under different excitation wavelengths are shown in the figure. The fluorescence emission peak of the fluorescence intensity enhanced AIE-CDs prepared in Example 2 is always stable at 604 nm under excitation in the wavelength range of 520-585 nm, and the results show that the prepared AIE-CDs exhibit excitation wavelength independent properties.

[0051] Figure 5 The fluorescence excitation and emission spectra of the fluorescence intensity enhanced AIE-CDs prepared in Example 2 are shown in the figure. As shown in the figure, the fluorescence emission intensity of the fluorescence intensity enhanced AIE-CDs prepared in Example 2 is as high as 10 to the power of 6. Under excitation at the optimal excitation wavelength of 560 nm, it can emit the strongest red fluorescence at 604 nm.

[0052] Figure 6 The fluorescence emission spectra of the fluorescence intensity enhanced AIE-CDs prepared in Example 2 and the AIE-CDs prepared in Comparative Example 1 under excitation at 560 nm are shown in the figure. As shown in the figure, the fluorescence intensity of the AIE-CDs without adding PEG is weak, and the fluorescence intensity of the AIE-CDs prepared by adding PEG is significantly enhanced at the same concentration, which shows that the addition of PEG can passivate and enhance the fluorescence performance.

[0053] Figure 7 The photographs of the fluorescence intensity enhanced AIE-CDs prepared in Example 2 dispersed in different solvents under sunlight and 365 nm ultraviolet light radiation are shown in the figure. As shown in the figure, the solubility and fluorescence emission of the fluorescence intensity enhanced AIE-CDs prepared in Example 2 in different solvents are different, which shows the influence of solvents on the fluorescence performance of the carbon dots. As shown in the figure, 1 mg of Example 2 is added to 4 mL of different solvents (ethanol, acetic acid, DMF, DMSO and water). Under sunlight, it can be seen that the AIE-CDs only present a solid precipitation and uneven particle dispersion state in water, and present excellent dispersibility in the remaining four solvents. When irradiated by 365 nm ultraviolet light, the AIE-CDs dispersed well in ethanol, acetic acid, DMF and DMSO present obvious blue fluorescence, and the AIE-CDs particles suspended in water solution present bright red fluorescence.

[0054] Figure 8Photographs of the AIE-CDs prepared in Example 2 dispersed in different solvents under sunlight and 365 nm UV irradiation. As shown in the figure, under 560 nm excitation, the AIE-CDs dispersed in HAC and DMSO emit almost no fluorescence at 604 nm, only emit weak red fluorescence in EtOH, and the fluorescence emission in DMF is enhanced, while the red fluorescence emission of the AIE-CDs dispersed in water is the strongest, which can be attributed to the largest degree of aggregation of Example 2 in water.

[0055] Figure 9 Photographs of the AIE-CDs prepared in Example 2 dispersed in different water content acetic acid solutions under sunlight and 365 nm UV irradiation. As shown in the figure, first prepare a 5 mg / mL AIE-CDs acetic acid solution, ultrasonically dissolve 15 mg of AIE-CDs in 3 mL of acetic acid, then add 0.3 mL of the prepared AIE-CDs acetic acid solution to each EP tube, and then add acetic acid 2.7 mL, 2.4 mL, 2.1 mL, 1.8 mL, 1.5 mL, 1.2 mL, 0.9 mL, 0.6 mL, 0.3 mL, 0 mL, and water solution 0 mL, 0.3 mL, 0.6 mL, 0.9 mL, 1.2 mL, 1.5 mL, 1.8 mL, 2.1 mL, 2.4 mL, 2.7 mL in order. Finally, the AIE-CDs concentration is 0.3 mg / mL, and the water volume fraction in the acetic acid water system is 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90%, respectively. From the photographs under sunlight, it can be clearly observed that with the increase of the water volume fraction, the whole system gradually changes from clear and transparent to turbid, which indicates that the AIE-CDs are gradually precipitated and the degree of aggregation increases. Under 365 nm UV irradiation, with the gradual increase of the water volume fraction in the acetic acid water system, the fluorescence emission of the AIE-CDs prepared in Example 2 gradually changes from blue light to red light, when the water volume fraction is 60%, the blue fluorescence of the AIE-CDs is obviously weakened, and a weak red fluorescence appears, and when the water volume fraction continues to increase to 90%, the red fluorescence is obviously enhanced, which indicates that the AIE-CDs can emit blue fluorescence in a dispersed state, and emit bright red fluorescence in an aggregated state, and the red fluorescence enhancement of the AIE-CDs is due to the increase of the aggregation degree in the poor solvent acetic acid, which is consistent with the AIE characteristics of carbon dots.

[0056] Figure 10When the AIE-CDs with enhanced fluorescence intensity prepared in Example 2 are dispersed in acetic acid solutions with different water contents, the fluorescence emission intensity changes at the peak positions of 448 nm and 604 nm are shown in a broken line graph. As shown in the figure, as the water volume fraction increases, the blue fluorescence at 448 nm shows a decreasing trend as a whole. When the water volume fraction reaches 50%, the blue fluorescence intensity drops sharply. The peak fluorescence emission intensity at 604 nm slowly increases in the early stage and then suddenly increases after reaching 60%. The above phenomenon can be attributed to the fact that as the degree of aggregation of AIE-CDs nanoparticles increases, the intramolecular rotation and vibration of AIE-CDs are restricted, which reduces the probability of non-radiative transitions, resulting in enhanced fluorescence emission, which meets the typical characteristics of AIE-CDs.

[0057] Figure 11 Figures 2 and 3 show the fluorescence emission spectra of AIE-CDs prepared in Comparative Example 1 and Examples 1-3. The effect of the molecular weight of the passivating agent PEG on the fluorescence enhancement of AIE-CDs was investigated. The fluorescence emission of Examples 1-3 exhibited varying degrees of enhancement compared to Comparative Example 1. At an excitation wavelength of 560 nm, as the PEG molecular weight increased from 200 to 600, the fluorescence of the materials first increased and then decreased, with the AIE-CDs prepared in Example 2 exhibiting the greatest fluorescence enhancement. Therefore, a moderate PEG molecular weight allows for optimal interaction with the functional groups on the carbon dot surface, forming a stable passivation layer, reducing surface defects, and enhancing fluorescence emission.

[0058] Figure 12 The fluorescence emission spectra of AIE-CDs prepared in Comparative Example 1, Examples 2, and 4-8 are shown. The effect of the PEG-400 doping level on the fluorescence enhancement of AIE-CDs is investigated. As shown in the figure, as the PEG-400 doping level increases from 50 μL to 400 μL, the fluorescence emission of the AIE-CDs initially increases and then decreases (Ex = 560 nm), with the AIE-CDs prepared in Example 2 achieving the maximum enhancement. This indicates that excessive PEG usage can form an excessively thick passivation layer on the carbon dot surface, increasing photon scattering and absorption within the AIE-CDs and leading to a decrease in fluorescence intensity. Therefore, an appropriate amount of PEG doping can effectively repair surface defect states in AIE-CDs, enhancing the quantum confinement effect and significantly improving fluorescence intensity.

[0059] Figure 13Figure 2 shows fluorescence imaging of 4T1 and Jurkat cells using the fluorescence-enhanced AIE-CDs prepared in Example 2. Jurkat and 4T1 cells were first washed with Tris (10 mM, pH 6.5) buffer. After evacuating the Tris (10 mM, pH 6.5), 2 mL of 4% paraformaldehyde fixative was added to each of the EP tube and confocal culture dish. Jurkat and 4T1 cells were fixed at room temperature for 15 minutes and observed microscopically. The fixative was then removed, and the cells were washed twice with Tris buffer by centrifugation. 5% BSA blocking solution was added and blocked at room temperature for 1 hour. The BSA blocking solution was then removed by centrifugation, and the cells were washed twice with Tris-HCl buffer. Finally, 1 mL of 100 ppm Example 2 was added to the Jurkat cells, resuspended, and mixed thoroughly. The cells were then transferred to the 4T1 cell dish and incubated at room temperature for 30 minutes in the dark. Finally, the Jurkat cells and 4T1 cells were washed twice with Tris, and the washed Jurkat cell suspension was transferred to the confocal dish corresponding to the 4T1 cells. The difference in fluorescent staining of the two cells in Example 2 was verified using a confocal fluorescence microscope.

[0060] like Figure 13 As shown in the figure, when Jurkat cells were mixed and cultured with the AIE-CDs solution, only weak red fluorescence was observed. However, when 4T1 cells were mixed and cultured with the AIE-CDs solution, strong red fluorescence was observed in the 4T1 cells. Subsequently, AIE-CDs were added to a mixed system of Jurkat and 4T1 cells and cultured. It was found that only the 4T1 cells expressed bright red fluorescence, mainly due to the aggregation-induced red light emission of the carbon dots, but no red fluorescence was observed on the Jurkat cells. These results indicate that the AIE-CDs prepared in Example 2 have high specificity for 4T1 cells and can specifically identify 4T1 cells in a mixed solution with Jurkat cells, achieving differentiation between tumor cells and white blood cells.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing aggregation-induced emission carbon dots with enhanced fluorescence intensity, characterized in that: The following steps are involved: (1) dissolving 2,2-dithiodibenzoic acid in acetic acid, stirring and mixing to obtain a mixed solution; (2) PEG and triethylamine were added to the mixed solution in sequence, stirred evenly, and heated to react to obtain a carbon dot solution; (3) After the carbon dot solution is cooled to room temperature, it is poured into boiling water and allowed to stand. After removing the supernatant, the precipitate is washed and dried to obtain aggregation-induced emission carbon dots with enhanced fluorescence intensity.

2. The method for preparing aggregation-induced emission carbon dots with enhanced fluorescence intensity according to claim 1, characterized in that: In step (1), the concentration of the 2,2-dithiodibenzoic acid in acetic acid is 10-40 mg / mL.

3. The method for preparing aggregation-induced emission carbon dots with enhanced fluorescence intensity according to claim 1, characterized in that: In step (2), the molecular weight of the PEG is 200-600.

4. The method for preparing aggregation-induced emission carbon dots with enhanced fluorescence intensity according to claim 1, wherein: The volume ratio of PEG to acetic acid is 0.05-0.4:

1.

5. The method for preparing aggregation-induced emission carbon dots with enhanced fluorescence intensity according to claim 1, characterized in that: The volume ratio of triethylamine to acetic acid is 0.02-0.23:

1.

6. The method for preparing aggregation-induced emission carbon dots with enhanced fluorescence intensity according to claim 1, characterized in that: In step (2), the heating reaction temperature is 180-210°C and the time is 8-12 hours.

7. Aggregation-induced emission carbon dots with enhanced fluorescence intensity obtained according to the preparation method according to any one of claims 1 to 6.

8. The aggregation-induced emission carbon dots with enhanced fluorescence intensity according to claim 7, characterized in that: The aggregation-induced luminescence carbon dots with enhanced fluorescence intensity exhibit red fluorescence of different fluorescence intensities when irradiated with excitation light in an aggregated state; and exhibit blue fluorescence when irradiated with excitation light in a dispersed state.

9. Use of the aggregation-induced emission carbon dots with enhanced fluorescence intensity according to claim 6 or 7 in cell imaging.

10. The use according to claim 9, characterized in that The aggregation-induced emission carbon dots with enhanced fluorescence intensity are used to distinguish 4T1 cells from Jurkat cells.

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