1. A carbon dot precursor based on aggregation-induced emission effect is characterized in that the carbon dot precursor is tetraphenylethylene derivative, the phenylethene derivative is a compound shown as a formula (I) and/or a stereoisomer of the compound shown as the formula (I),

in the formula (I), R₁、R₂、R₃And R₄Can be respectively and independently hydrogen, amino, hydroxyl, carboxyl, cyano, fluorine, chlorine, bromine, iodine, C_1-6Alkyl radical, C_1-6Alkoxy, amino substituted C_1-6Alkyl, amino substituted C_1-6Alkoxy, hydroxy-substituted C_1-6Alkyl, hydroxy substituted C_1-6Alkoxy, carboxy substituted C_1-6Alkyl or carboxyl substituted C_1-6An alkoxy group.

2. A carbon dot precursor based on aggregation-induced emission effect is characterized in that the carbon dot precursor is tetraphenylpyrazine derivative, the tetraphenylpyrazine derivative is a compound shown as a formula (II) and/or a stereoisomer of the compound shown as the formula (II),

in the formula (II), R₁、R₂、R₃And R₄Can be respectively and independently hydrogen, amino, hydroxyl, carboxyl, cyano, fluorine, chlorine, bromine, iodine, C_1-6Alkyl radical, C_1-6Alkoxy, amino substituted C_1-6Alkyl, amino substituted C_1-6Alkoxy, hydroxy-substituted C_1-6Alkyl, hydroxy substituted C_1-6Alkoxy, carboxy substituted C_1-6Alkyl or carboxyl substituted C_1-6An alkoxy group.

3. A carbon dot precursor based on aggregation-induced emission effect is characterized in that the carbon dot precursor is a cyano-substituted diphenylethylene derivative, the cyano-substituted diphenylethylene derivative is a compound shown in a formula (III) and/or a stereoisomer of the compound shown in the formula (III),

in the formula (III), R₁And R₂Can be respectively and independently hydrogen, amino, hydroxyl, carboxyl, cyano, fluorine, chlorine, bromine, iodine, C_1-6Alkyl radical, C_1-6Alkoxy, amino substituted C_1-6Alkyl, amino substituted C_1-6Alkoxy, hydroxy-substituted C_1-6Alkyl, hydroxy substituted C_1-6Alkoxy, carboxy substituted C_1-6Alkyl or carboxyl substituted C_1-6An alkoxy group.

4. A carbon dot precursor based on aggregation-induced emission effect is characterized in that the carbon dot precursor is a diphenyl anthracene derivative, the diphenyl anthracene derivative is a compound shown in a formula (IV) and/or a stereoisomer of the compound shown in the formula (IV),

in the formula (IV), R₁And R₂Can be respectively and independently hydrogen, amino, hydroxyl, carboxyl, cyano, fluorine, chlorine, bromine, iodine, C_1-6Alkyl radical, C_1-6Alkoxy, amino substituted C_1-6Alkyl, amino substituted C_1-6Alkoxy, hydroxy-substituted C_1-6Alkyl, hydroxy substituted C_1-6Alkoxy, carboxy substituted C_1-6Alkyl or carboxyl substituted C_1-6An alkoxy group.

5. A method of preparing a carbon dot having aggregation-induced emission characteristics, comprising:

(1) mixing the carbon dot precursor according to at least one of claims 1 to 4 with an organic solvent and ultrasonically dispersing the mixture to obtain a mixed solution;

(2) putting the mixed solution into a reaction kettle for solvothermal reaction;

(3) and (3) adding water to dilute the reaction solution obtained in the step (2), extracting with dichloromethane, performing column chromatography and spin-drying to obtain a carbon point.

6. The method for producing a carbon dot having an aggregation-induced emission characteristic according to claim 5, wherein the step (1) satisfies at least one of the following conditions:

the carbon dot precursor is a tetraphenylethylene derivative;

the carbon dots are at least one selected from 1- (4-aminobenzene) -1,2, 2-triphenylethylene, 1, 2-bis (4-aminobenzene) -1, 2-diphenylethylene and 1, 2-bis (4-hydroxybenzene) -1, 2-diphenylethylene;

the organic solvent is at least one selected from acetic acid, ethanol, tetrahydrofuran, N-dimethylformamide, cyclohexane, toluene and dimethyl sulfoxide.

7. The method for preparing carbon dots with aggregation-induced emission characteristics according to claim 5, wherein in the step (2), the solvothermal reaction is performed at a temperature of 120-260 ℃ for 6-24 hours.

8. The method for producing a carbon dot having aggregation-induced emission characteristics according to claim 5, wherein the step (3) comprises: cooling the reaction liquid to room temperature, adding water for dilution, and extracting with dichloromethane for 2-4 times to obtain an organic phase; drying the organic phase over anhydrous magnesium sulfate, filtering and rotary evaporating to remove the organic solvent; the resulting product was subjected to column chromatography, gradient eluted with dichloromethane/methanol, and spin-dried to obtain the carbon dots.

9. A carbon dot prepared by the method for preparing a carbon dot having aggregation-induced emission characteristics according to any one of claims 5 to 8.

10. The aggregation-induced emission effect-based carbon dot precursor according to any one of claims 1 to 4 and/or the method for preparing a carbon dot having aggregation-induced emission characteristics according to any one of claims 5 to 8 and/or the use of the carbon dot according to claim 9 in the fields of bioimaging, disease research, luminescent display, electronic ink and anti-counterfeiting.

Background

Carbon Dots (CDs) are novel zero-dimensional carbon materials which are widely concerned in recent years, generally have a spheroidal structure with the diameter of less than 10nm, and have the advantages of unique fluorescence, optical stability, biocompatibility and the like. Compared with the traditional metal semiconductor quantum dots and organic dyes, the carbon dots not only keep excellent fluorescence performance, but also overcome the defects of poor light stability, high toxicity, complex preparation process and the like, so the carbon dots are rapidly taken as research hotspots at home and abroad since the first report in 2004. CDs are considered by researchers to be ideal materials for replacing semiconductor quantum dots and organic dyes, and have wide application prospects in multiple fields of biological imaging, disease treatment, photoelectric devices, catalysis, sensing, printing ink and the like. The research on carbon dots has been greatly advanced at present, but still faces many problems to be solved, and designing a carbon dot for synthetic solid state light emission is one of the focuses of current researchers.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, the invention aims to provide a carbon dot precursor based on aggregation-induced emission effect, a carbon dot and a preparation method and application thereof. The carbon dots prepared by the preparation method of the carbon dot precursor and/or the carbon dots have high fluorescence quantum yield, stable luminescence and obvious aggregation-induced luminescence property, can effectively solve the self-quenching problem of the carbon dots under high concentration and solid state, and can be widely applied to the fields of cell imaging, luminescence display, electronic ink, anti-counterfeiting and the like.

The present application is primarily based on the following problems and findings:

most of CDs reported in the literature only emit light in solution state, but have self-quenching effect at high concentration and in solid state, which limits the practical application of CDs. It is believed that the effect of CDs in self-quenching at high concentrations as well as in the solid state is caused by direct pi-pi interactions or Fluorescence Resonance Energy Transfer (FRET). In order to realize solid-state luminescence of carbon dots, most researches have been carried out to disperse the carbon dots in a solid matrix, for example, the solid matrix can be polymer, inorganic substance and starch, which belongs to a physical method that the distance between carbon dot particles is increased, so that the carbon dots are uniformly dispersed, and the self-quenching of the carbon dots is avoided. In these cases, the dispersion matrix acts as a medium to disperse the carbon dots, and the presence of polymer chains on the surface of the carbon dots is evident from their FT-IR spectrum, for example, currently, organosilane functionalized carbon dots (Si-CDs) are obtained using Citric Acid (CA) and N- (beta-aminoethyl) -gamma-aminopropyltrimethoxysilane (KH-792), the Quantum Yield (QY) of Si-CDs in solid state is 2.5 times that of the solution state, indicating that it has a strong solid state luminescence phenomenon, and the FT-IR spectrum indicates the functionalization of organosilanes on the surface of Si-CDs, since KH-792 long chains have significant steric hindrance, maintaining proper spacing between the prepared Si-CDs, weakening aggregation and reducing pi-pi interactions. In addition, there are methods for producing highly luminescent carbon dots using spatially limited vacuum heating synthesis in CaCl₂In the presence of citric acid and urea, the mixture is heated under vacuum to form an expanded foam, which is transformed into carbon dots of uniform size by dehydration and carbonization processes carried out in a narrow ultra-thin space of the foam wall, the functional groups (containing O and N groups) and the uniform size on the surface of the carbon dots preventing sp of the carbon core in the aggregate²Pi-pi stacking of domains to avoid aggregation induced quenching (ACQ). However, the above two methods do not effectively solve the self-quenching phenomenon of CDs at high concentration and in solid state, CDs still has the problem of self-quenching or unstable luminescence at high concentrations.

To this end, according to a first aspect of the invention, the invention proposes a carbon dot precursor based on aggregation-induced emission effects. According to an embodiment of the present invention, the carbon point precursor is a tetraphenylethylene derivative, said phenylethene derivative being a compound of formula (I) and/or a stereoisomer of a compound of formula (I),

wherein, in the formula (I), R₁、R₂、R₃And R₄Can be respectively and independently hydrogen, amino, hydroxyl, carboxyl, cyano, fluorine, chlorine, bromine, iodine, C_1-6Alkyl radical, C_1-6Alkoxy, amino substituted C_1-6Alkyl, amino substituted C_1-6Alkoxy, hydroxy-substituted C_1-6Alkyl, hydroxy substituted C_1-6Alkoxy, carboxy substituted C_1-6Alkyl or carboxyl substituted C_1-6An alkoxy group.

According to a second aspect of the present invention, the present invention proposes yet another carbon dot precursor based on aggregation-induced emission effects. According to an embodiment of the present invention, the carbon dot precursor is a tetraphenylpyrazine derivative which is a compound represented by formula (II) and/or a stereoisomer of a compound represented by formula (II),

wherein, in the formula (II), R₁、R₂、R₃And R₄Can be respectively and independently hydrogen, amino, hydroxyl, carboxyl, cyano, fluorine, chlorine, bromine, iodine, C_1-6Alkyl radical, C_1-6Alkoxy, amino substituted C_1-6Alkyl, amino substituted C_1-6Alkoxy, hydroxy-substituted C_1-6Alkyl, hydroxy substituted C_1-6Alkoxy, carboxyl substitutionC of (A)_1-6Alkyl or carboxyl substituted C_1-6An alkoxy group.

According to a third aspect of the present invention, the present invention proposes a further carbon dot precursor based on aggregation-induced emission effect. According to an embodiment of the present invention, the carbon point precursor is a cyano-substituted diphenylethylene derivative, which is a compound represented by formula (III) and/or a stereoisomer of the compound represented by formula (III),

wherein, in the formula (III), R₁And R₂Can be respectively and independently hydrogen, amino, hydroxyl, carboxyl, cyano, fluorine, chlorine, bromine, iodine, C_1-6Alkyl radical, C_1-6Alkoxy, amino substituted C_1-6Alkyl, amino substituted C_1-6Alkoxy, hydroxy-substituted C_1-6Alkyl, hydroxy substituted C_1-6Alkoxy, carboxy substituted C_1-6Alkyl or carboxyl substituted C_1-6An alkoxy group.

According to a fourth aspect of the present invention, the present invention proposes a further carbon dot precursor based on aggregation-induced emission effect. According to an embodiment of the present invention, the carbon dot precursor is a diphenylanthracene derivative, which is a compound represented by formula (IV) and/or a stereoisomer of the compound represented by formula (IV),

wherein, in the formula (IV), R₁And R₂Can be respectively and independently hydrogen, amino, hydroxyl, carboxyl, cyano, fluorine, chlorine, bromine, iodine, C_1-6Alkyl radical, C_1-6Alkoxy, amino substituted C_1-6Alkyl, amino substituted C_1-6Alkoxy, hydroxy-substituted C_1-6Alkyl, hydroxy substituted C_1-6Alkoxy, carboxy substituted C_1-6Alkyl or carboxyl substitutionC of (A)_1-6An alkoxy group.

The four carbon dot precursors based on aggregation-induced emission effect have the following advantages: the inventor finds that, compared with the existing carbon dot precursor materials, the above four carbon dot precursors, namely tetraphenyl ethylene derivatives, tetraphenyl pyrazine derivatives, cyano-substituted diphenyl ethylene derivatives and diphenyl anthracene derivatives, all have a "propeller" configuration, for example, the central structure of the compound shown in formula (I) or formula (II) is surrounded by four peripheral benzene ring rotors (benzene rings), the central structure of the compound shown in formula (III) or formula (IV) is surrounded by two peripheral benzene ring rotors (benzene rings), and in a solution state, the benzene rings of the peripheral structure can freely rotate around a double bond or the central structure through a single bond, and the process consumes energy of an excited state through non-radiative transition, resulting in reduction or quenching of fluorescence; and when the aggregate is formed, the propeller configuration of the carbon dot precursor can prevent pi-pi accumulation so as to inhibit fluorescence quenching, and meanwhile, due to space limitation, the intramolecular rotation of the carbon dot precursor is inhibited, and the energy of an excited state is consumed in a radiation transition mode, so that the fluorescence is enhanced. Based on the above findings, the inventors have conducted a great deal of experiments and verified that when a carbon dot is prepared by using at least one of the above four carbon dot precursors, the carbon dot can be maintained in the above "propeller" configuration, and in an aggregation state or a solid state, the "propeller" configuration of the carbon dot can not only prevent pi-pi accumulation, but also limit vibration or rotation of aromatic rings on the surface thereof, suppress non-radiative transition, and enhance radiative transition, so that the intensity of the carbon dot light can be increased to different extents, and thus, not only can the problem of self-quenching of the carbon dot at high concentration and in a solid state be effectively solved, but also the stability of the carbon dot light emission can be improved.

According to a fifth aspect of the present invention, there is provided a method of preparing a carbon dot having aggregation-induced emission characteristics. According to an embodiment of the invention, the method comprises:

(1) mixing at least one of the four carbon point precursors with an organic solvent and carrying out ultrasonic dispersion so as to obtain a mixed solution;

(2) putting the mixed solution into a reaction kettle for solvothermal reaction;

(3) and (3) adding water to dilute the reaction solution obtained in the step (2), extracting with dichloromethane, performing column chromatography and spin-drying to obtain a carbon point.

According to the method for preparing the carbon dots with aggregation-induced emission characteristics, the mixed solution of the carbon dot precursor and the organic solvent is subjected to solvothermal reaction, so that intermolecular dehydration and dehydrogenation of the mixed solution can be performed, and further rearrangement, polymerization, aromatization and carbonization can be performed on the mixed solution to obtain the carbon dots, and the purity and the emission stability of the carbon dots can be further improved by extracting the reaction solution and purifying the reaction solution by column chromatography. In conclusion, the method has the advantages of few steps and simple operation, and the prepared carbon dots have high fluorescence quantum yield, high purity, stable luminescence and obvious aggregation-induced luminescence property, can effectively solve the self-quenching problem of the carbon dots under high concentration and solid state, can be widely applied to the fields of cell imaging, luminescent display, electronic ink, anti-counterfeiting and the like, and simultaneously provides a new carbon dot solid state luminescence mechanism, namely the intramolecular motion is limited, thereby providing a new direction for solving the self-quenching problem of the carbon dots under high concentration and solid state.

In addition, the method for preparing the carbon dots having aggregation-induced emission characteristics according to the above-described embodiment of the present invention may further have the following additional technical features:

in some embodiments of the invention, in step (1), the carbon dot precursor is a tetraphenylethylene derivative.

In some embodiments of the invention, in step (1), the carbon site is at least one selected from the group consisting of 1- (4-aminobenzene) -1,2, 2-triphenylethylene, 1, 2-bis (4-aminobenzene) -1, 2-diphenylethylene, and 1, 2-bis (4-hydroxybenzene) -1, 2-diphenylethylene.

In some embodiments of the present invention, in the step (1), the organic solvent is at least one selected from the group consisting of acetic acid, ethanol, tetrahydrofuran, N-dimethylformamide, cyclohexane, toluene, and dimethyl sulfoxide.

In some embodiments of the present invention, in the step (2), the temperature of the solvothermal reaction is 120-260 ℃ for 6-24 hours.

In some embodiments of the invention, step (3) comprises: cooling the reaction liquid to room temperature, adding water for dilution, and extracting with dichloromethane for 2-4 times to obtain an organic phase; drying the organic phase over anhydrous magnesium sulfate, filtering and rotary evaporating to remove the organic solvent; the resulting product was subjected to column chromatography, gradient eluted with dichloromethane/methanol, and spin-dried to obtain the carbon dots.

According to a sixth aspect of the invention, a carbon dot is provided. According to an embodiment of the present invention, the carbon dot is manufactured using the above-described method of manufacturing a carbon dot having aggregation-induced emission characteristics. Compared with the prior art, the carbon dots are stable in luminescence, have obvious aggregation-induced luminescence properties, are more stable in luminescence in an aggregation state or in a solid state, and can be widely applied to the fields of cell imaging, luminescence display, electronic ink, anti-counterfeiting and the like.

According to a seventh aspect of the present invention, the present invention proposes various carbon dot precursors based on aggregation-induced emission effects as described above and/or the above method for preparing a carbon dot having aggregation-induced emission characteristics and/or the use of the above carbon dot in the fields of bio-imaging, disease research, luminescent display, electronic ink, and anti-counterfeiting. Compared with the prior art, the carbon dot precursor, the preparation method or the carbon dot used for the purpose has stronger applicability, better effect and more stability.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 shows CDs-TPE-NH prepared in example 1 of the present invention₂(corresponding to FIG. 1(a)) and CDs-TPE-2NH obtained in example 2₂(corresponding to FIG. 1(b)) is a transmission electron micrograph.

FIG. 2 shows CDs-TPE-NH prepared in example 1 of the present invention₂(corresponding to FIG. 2(a)) and CDs-TPE-2NH obtained in example 2₂(corresponding to FIG. 2(b)) is the particle size distribution diagram.

FIG. 3 shows CDs-TPE-NH prepared in example 1 of the present invention₂(corresponding to FIG. 3(a)) and CDs-TPE-2NH obtained in example 2₂X-ray diffraction pattern (XRD) (corresponding to fig. 3 (b)).

FIG. 4 shows TPE-NH in example 1 of the present invention₂、CDs-TPE-NH₂(corresponding to FIG. 4(a)) and TPE-2NH in example 2₂、CDs-TPE-2NH₂(corresponding to FIG. 4(b)) is an infrared absorption spectrum (FT-IR).

FIG. 5 shows CDs-TPE-NH prepared in example 1 of the present invention₂(corresponding to FIG. 5(a)) and CDs-TPE-2NH obtained in example 2₂(corresponding to FIG. 5(b)) nuclear magnetic hydrogen spectrum diagram (¹H NMR)。

FIG. 6 shows CDs-TPE-NH prepared in example 1 of the present invention₂(corresponding to FIGS. 6(a), (c), (d), (e)) and CDs-TPE-2NH obtained in example 2₂(corresponding to FIGS. 6(b), (f), (g), (h)) in X-ray photoelectron spectroscopy (XPS).

FIG. 7 shows CDs-TPE-NH prepared in example 1 of the present invention₂And CDs-TPE-2NH prepared in example 2₂The ultraviolet-visible absorption spectrum and the fluorescence spectrum of (1), wherein FIG. 7(a) is 0.004mg/mL of CDs-TPE-NH₂Uv-vis absorption spectra in different solvents; FIG. 7(b) shows CDs-TPE-NH₂Ultraviolet-visible absorption spectrum and fluorescence spectrum (lambda) of the powder_ex363nm, slit: 1.5 nm); FIG. 7(c) shows CDs-TPE-NH₂Fluorescence spectra of the powder at different excitation wavelengths; FIG. 7(d) CDs-TPE-2NH at 0.004mg/mL₂Uv-vis absorption spectra in different solvents; FIG. 7(e) shows CDs-TPE-2NH₂Ultraviolet-visible absorption spectrum and fluorescence spectrum (lambda) of the powder_ex300nm, slit: 1.5 nm); FIG. 7(f) shows CDs-TPE-2NH₂Fluorescence spectra of the powder at different excitation wavelengths.

FIG. 8 is a Transmission Electron Micrograph (TEM) and a particle size distribution (FIG. 8(b)) of CDs-TPE-2OH obtained in example 3 of the present invention.

FIG. 9 is an X-ray diffraction pattern (XRD) of CDs-TPE-2OH obtained from example 3 of the present invention.

FIG. 10 is a graph of the infrared absorption spectra (FT-IR) of TPE-2OH and CDs-TPE-2OH in example 3 of the present invention.

FIG. 11 is an X-ray photoelectron spectrum (XPS) of CDs-TPE-2OH prepared in example 3 of the present invention.

FIG. 12 shows the nuclear magnetic hydrogen spectrum (C) (2 OH) of CDs-TPE-2OH prepared in example 3 of the present invention¹H NMR)。

FIG. 13 shows the UV-visible absorption spectrum and the fluorescence spectrum of CDs-TPE-2OH prepared in example 3 of the present invention, wherein FIG. 13(a) shows the UV-visible absorption spectrum of CDs-TPE-2OH in different solvents at 0.004 mg/mL; FIG. 13(b) shows the UV-visible absorption spectrum and fluorescence spectrum (. lamda.) of CDs-TPE-2OH powder_ex363nm, slit: 1.5 nm); FIG. 13(c) is the fluorescence spectrum of CDs-TPE-2OH powder at different excitation wavelengths.

FIG. 14 shows TPE-NH of example 1 of the present invention₂(corresponding to FIG. 14(a)), CDs-TPE-NH₂(corresponding to FIG. 14(b)) and TPE-2NH in example 2₂(corresponding to FIG. 14(c)), CDs-TPE-2NH₂(corresponding to FIG. 14(d)) is a graph comparing stability of ink against acid.

FIG. 15 is an image of cells of CDs-TPE-NH2 (top row in FIG. 15) obtained in example 1 and CDs-TPE-2NH2 (bottom row in FIG. 15) obtained in example 2.

FIG. 16 shows CDs-TPE-NH prepared in example 1₂(corresponding to FIGS. 16(a), (b)) DMSO/water mixed solvent system CDs-TPE-NH of different water content₂Fluorescence change pattern of (A), and CDs-TPE-2NH prepared in example 2₂(corresponding to FIGS. 16(c), (d)) CDs-TPE-2NH in DMSO/water mixed solvent system at different water contents₂Fluorescence change pattern of (2).

FIG. 17 shows CDs-TPE-NH prepared in example 1₂Distribution of hydrated particle size in DMSO/water mixed solvent system with water content of 0%, 50%, 90% (corresponding to FIGS. 17(e), (f), (g)), and CDs-TPE-2NH prepared in example 2₂Distribution of hydrated particle size in DMSO/water mixed solvent system with water content of 0%, 50%, 90% (corresponding to FIGS. 17(h), (i), (j)).

Fig. 18 is a flowchart of a method of preparing a carbon dot having aggregation-induced emission characteristics according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

The inventive concept of the present invention mainly derives from: the inventor finds that Tetraphenylethylene (TPE) is a molecule with aggregation-induced emission characteristics (AIE), the central olefin of the TPE molecule is surrounded by four peripheral benzene ring rotors (benzene rings), and in a solution state, the four benzene rings in the TPE molecule can freely rotate around a double bond through a single bond, and the process consumes the energy of an excited state in a non-radiative transition, so that the fluorescence is weakened or quenched; and when the aggregate is formed, the 'propeller' configuration of the TPE molecules can prevent pi-pi accumulation so as to inhibit fluorescence quenching, and meanwhile, due to space limitation, intramolecular rotation of the TPE molecules is inhibited, and the energy of an excited state is consumed in a radiation transition mode, so that fluorescence is enhanced. For this reason, the inventors conceived and verified a lot of experiments to find that the carbon dots can be prepared by using a compound having a "propeller" configuration as a carbon dot precursor to effectively solve the problem of self-quenching of the carbon dots at high concentration and in a solid state, wherein the compound having the "propeller" configuration may be specifically at least one selected from the group consisting of tetraphenyl ethylene derivatives, tetraphenyl pyrazine derivatives, cyano-substituted diphenyl ethylene derivatives and diphenyl anthracene derivatives, and the carbon dots prepared by using the above carbon dot precursor based on aggregation-induced emission effect are non-luminescent in a non-aggregated state or have an extremely small particle diameter in a solution state, and have a significant fluorescence characteristic in an aggregated state or a solid state, for example, the prepared carbon dots have a significant fluorescence characteristic in a case where the volume of water is high when dispersed in water, due to hydrophobicity of the prepared carbon dots, can aggregate in water to produce fluorescent properties.

To this end, according to a first aspect of the invention, the invention proposes a carbon dot front based on aggregation-induced emission effectsAnd (4) driving the body. According to an embodiment of the present invention, the carbon dot precursor is a tetraphenylethylene derivative, and the phenylethene derivative is a compound represented by formula (I) and/or a stereoisomer of the compound represented by formula (I), wherein in formula (I), R is₁、R₂、R₃And R₄Can be respectively and independently hydrogen, amino, hydroxyl, carboxyl, cyano, fluorine, chlorine, bromine, iodine, C_1-6Alkyl radical, C_1-6Alkoxy, amino substituted C_1-6Alkyl, amino substituted C_1-6Alkoxy, hydroxy-substituted C_1-6Alkyl, hydroxy substituted C_1-6Alkoxy, carboxy substituted C_1-6Alkyl or carboxyl substituted C_1-6An alkoxy group,

according to one embodiment of the invention, the tetraphenylethylene derivative may be 1- (4-aminophenyl) -1,2, 2-triphenylethylene (TPE-NH)₂) 1, 2-bis (4-aminophenyl) -1, 2-diphenylethylene (TPE-2 NH)₂) Or a substituted tetraphenylethylene derivative such as 1, 2-bis (4-hydroxyphenyl) -1, 2-diphenylethylene (TPE-2 OH).

According to a second aspect of the present invention, the present invention proposes yet another carbon dot precursor based on aggregation-induced emission effects. According to an embodiment of the present invention, the carbon dot precursor is a tetraphenylpyrazine derivative, and the tetraphenylpyrazine derivative is a compound represented by formula (II) and/or a stereoisomer of the compound represented by formula (II), wherein in formula (II), R is₁、R₂、R₃And R₄Can be respectively and independently hydrogen, amino, hydroxyl, carboxyl, cyano, fluorine, chlorine, bromine, iodine, C_1-6Alkyl radical, C_1-6Alkoxy, amino substituted C_1-6Alkyl, amino substituted C_1-6Alkoxy, hydroxy-substituted C_1-6Alkyl, hydroxy substituted C_1-6Alkoxy, carboxy substituted C_1-6Alkyl or carboxyl substituted C_1-6An alkoxy group,

according to a third aspect of the present invention, the present invention proposes a further carbon dot precursor based on aggregation-induced emission effect. According to an embodiment of the present invention, the carbon point precursor is a cyano-substituted diphenylethylene derivative, and the cyano-substituted diphenylethylene derivative is a compound represented by formula (III) and/or a stereoisomer of the compound represented by formula (III), wherein in formula (III), R is₁And R₂Can be respectively and independently hydrogen, amino, hydroxyl, carboxyl, cyano, fluorine, chlorine, bromine, iodine, C_1-6Alkyl radical, C_1-6Alkoxy, amino substituted C_1-6Alkyl, amino substituted C_1-6Alkoxy, hydroxy-substituted C_1-6Alkyl, hydroxy substituted C_1-6Alkoxy, carboxy substituted C_1-6Alkyl or carboxyl substituted C_1-6An alkoxy group,

according to a fourth aspect of the present invention, the present invention proposes a further carbon dot precursor based on aggregation-induced emission effect. According to an embodiment of the present invention, the carbon dot precursor is a diphenylanthracene derivative, and the diphenylanthracene derivative is a compound represented by formula (IV) and/or a stereoisomer of the compound represented by formula (IV), wherein in formula (IV), R is₁And R₂Can be respectively and independently hydrogen, amino, hydroxyl, carboxyl, cyano, fluorine, chlorine, bromine, iodine, C_1-6Alkyl radical, C_1-6Alkoxy, amino substituted C_1-6Alkyl, amino substituted C_1-6Alkoxy, hydroxy-substituted C_1-6Alkyl, hydroxy substituted C_1-6Alkoxy, carboxy substituted C_1-6Alkyl or carboxyl substituted C_1-6An alkoxy group,

the inventor finds that the four carbon dot precursors based on aggregation-induced emission effect have the following advantages compared with the existing carbon dot precursor materials: the above four carbon point precursors, i.e. tetraphenylethylene derivative, tetraphenylpyrazine derivative, cyano-substituted diphenylethylene derivative and diphenylanthracene derivative, all have a "propeller" configuration, for example, the central structure of the compound shown in formula (I) or formula (II) is surrounded by four peripheral benzene ring rotors (benzene rings), the central structure of the compound shown in formula (III) or formula (IV) is surrounded by two peripheral benzene ring rotors (benzene rings), in a solution state, the benzene rings of the peripheral structure can freely rotate around a double bond or the central structure through a single bond, and the process consumes energy in an excited state with non-radiative transition, resulting in attenuation or quenching of fluorescence; and when the aggregate is formed, the propeller configuration of the carbon dot precursor can prevent pi-pi accumulation so as to inhibit fluorescence quenching, and meanwhile, due to space limitation, the intramolecular rotation of the carbon dot precursor is inhibited, and the energy of an excited state is consumed in a radiation transition mode, so that the fluorescence is enhanced. When at least one of the four carbon dot precursors is adopted to prepare the carbon dot, the carbon dot can be kept in the propeller configuration, in an aggregation state or a solid state, the propeller configuration of the carbon dot can prevent pi-pi accumulation, the vibration or rotation of the surface aromatic ring is limited, the non-radiative transition is inhibited, and the radiative transition is enhanced, so that the light intensity of the carbon dot is increased to different degrees, and therefore, the problem of self-quenching of the carbon dot in a high concentration and a solid state can be effectively solved, and the stability of the light emission of the carbon dot can be improved.

According to a fifth aspect of the present invention, there is provided a method of preparing a carbon dot having aggregation-induced emission characteristics. According to an embodiment of the invention, as shown with reference to fig. 18, the method comprises: (1) mixing at least one of the four carbon dot precursors of the tetraphenylethylene derivative, the tetraphenylpyrazine derivative, the cyano-substituted diphenylethylene derivative and the diphenylanthracene derivative with an organic solvent and carrying out ultrasonic dispersion to obtain a mixed solution, wherein the ultrasonic dispersion can improve the dissolving efficiency of the carbon dot precursors and the uniformity of the mixed solution; (2) placing the mixed solution in a reaction kettle for solvothermal reaction, so that intermolecular dehydration and dehydrogenation are carried out, and further rearrangement, polymerization, aromatization and carbonization are carried out to obtain carbon dots; (3) and (3) adding water to dilute the reaction solution obtained in the step (2), extracting with dichloromethane, performing column chromatography and spin-drying to obtain a solid carbon dot, specifically, cooling the reaction solution to room temperature, adding water to dilute the reaction solution, extracting with dichloromethane for 2-4 times to obtain an organic phase, adding anhydrous magnesium sulfate to the organic phase, drying, filtering, performing spin-steaming to remove an organic solvent, performing column chromatography to the obtained product, performing gradient elution with dichloromethane/methanol, and performing spin-drying to obtain a carbon dot with high purity, wherein the light-emitting stability of the carbon dot can be further improved by improving the purity of the carbon dot. The method is simple in process and operation, and the prepared carbon dot fluorescence quantum has high yield, high purity, stable luminescence and obvious aggregation-induced luminescence property, and can effectively solve the self-quenching problem of the carbon dot under high concentration and solid state. The method for preparing the carbon dot having aggregation-induced emission characteristics is described in detail below.

According to an embodiment of the present invention, in the step (1), the carbon dot precursor may be a tetraphenylethylene derivative, and preferably, the tetraphenylethylene derivative may be selected from 1- (4-aminobenzene) -1,2, 2-triphenylethylene (TPE-NH)₂) 1, 2-bis (4-aminophenyl) -1, 2-diphenylethylene (TPE-2 NH)₂) And at least one of 1, 2-bis (4-hydroxyphenyl) -1, 2-diphenylethylene (TPE-2OH), wherein acetic acid can be selected as the organic solvent, so that the carbon dots which are stable in luminescence and have obvious aggregation-induced luminescence properties can be successfully prepared, and the yield of the carbon dots can be improved. More preferably, the carbon dot precursor may be 1- (4-aminophenyl) -1,2, 2-triphenylethylene (TPE-NH)₂) And/or 1, 2-bis (4-hydroxyphenyl) -1, 2-diphenylethylene (TPE-2OH), whereby the yield of carbon spots can be further improved.

According to still another embodiment of the present invention, in the step (1), the organic solvent may be at least one selected from the group consisting of acetic acid, ethanol, tetrahydrofuran, N-dimethylformamide, cyclohexane, toluene and dimethylsulfoxide. The carbon dot precursor selected in the invention is insoluble in water, and the organic solvent can effectively dissolve the carbon dot precursor and promote the smooth proceeding of the solvothermal reaction. It should be noted that, the type of the carbon dot precursor selected in the present invention is different, and the type of the selected organic solvent may also be changed, and those skilled in the art can select the carbon dot according to actual needs as long as the carbon dot can be successfully prepared.

According to another embodiment of the present invention, in the step (2), the temperature of the solvothermal reaction may be 120 to 260 ℃, the time may be 6 to 24 hours, for example, the temperature may be 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, 210 ℃, 220 ℃, 230 ℃, 240 ℃ or 250 ℃, and the time may be 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours or 22 hours, and the inventors found that if the temperature of the solvothermal reaction is too low or the time is too short, not only the preparation efficiency is low, but also the yield of the carbon dots is low, and in the present invention, by controlling the above solvothermal reaction conditions, the smooth preparation of the carbon dots can be ensured, and the preparation efficiency and the yield of the carbon dots can also be improved.

According to a specific example of the invention, in step (3), for 60mL of reaction solution, 300mL of water may be added for dilution, extraction is performed for 3 times with dichloromethane, the amount of dichloromethane used for each extraction is 30mL, anhydrous magnesium sulfate is added to the obtained organic phase for drying for 1h, filtration is performed, the organic solvent is removed by rotary evaporation, and silica gel column chromatography is performed to obtain carbon dots with aggregation-induced emission characteristics, and the inventors found that the higher the purity of the carbon dots, the better the emission performance is, the higher the purity of the carbon dots can be, the higher the volume ratio of dichloromethane/methanol can be gradually increased in the gradient elution process, for example.

According to the embodiments of the present invention, the inventors have found that the carbon dots obtained by the above-described method for preparing carbon dots having aggregation-induced emission characteristics do not emit light when they exist in a non-aggregated state in a solution state or have an extremely small particle size, and have good fluorescence properties in an aggregated state or a solid state, for example, the prepared carbon dots have a remarkable fluorescence characteristic when they are dispersed in water at a high water volume (for example, the volume ratio of water may be not less than 70%), since the prepared carbon dots have hydrophobicity and can aggregate in water to generate fluorescence.

In summary, according to the method for preparing a carbon dot with aggregation-induced emission characteristics according to the above embodiments of the present invention, a mixed solution of a carbon dot precursor and an organic solvent is subjected to a solvothermal reaction, so that the mixed solution can undergo intermolecular dehydration and dehydrogenation, and further undergo rearrangement, polymerization, aromatization, and carbonization, so as to obtain a carbon dot, and the reaction solution is subjected to extraction and column chromatography purification, so that the purity and the emission stability of the carbon dot can be further improved. In conclusion, the method has the advantages of few steps and simple operation, and the prepared carbon dots have high fluorescence quantum yield, high purity, stable luminescence and obvious aggregation-induced luminescence property, can effectively solve the self-quenching problem of the carbon dots under high concentration and solid state, can be widely applied to the fields of cell imaging, luminescent display, electronic ink, anti-counterfeiting and the like, and simultaneously provides a new carbon dot solid state luminescence mechanism, namely the intramolecular motion is limited, thereby providing a new direction for solving the self-quenching problem of the carbon dots under high concentration and solid state. It should be noted that the features and effects described for the above four aggregation-induced emission effect-based carbon dot precursors are also applicable to the method for preparing a carbon dot with aggregation-induced emission characteristics, and are not repeated herein.

According to a sixth aspect of the invention, a carbon dot is provided. According to an embodiment of the present invention, the carbon dot is manufactured using the above-described method of manufacturing a carbon dot having aggregation-induced emission characteristics. Compared with the prior art, the carbon dots are stable in luminescence, have obvious aggregation-induced luminescence properties, are more stable in luminescence in an aggregation state or in a solid state, and can be widely applied to the fields of cell imaging, luminescence display, electronic ink, anti-counterfeiting and the like. It should be noted that the features and effects described for the above method for preparing a carbon dot with aggregation-induced emission characteristics are also applicable to the carbon dot, and are not described in detail herein.

According to a seventh aspect of the present invention, the present invention proposes various carbon dot precursors based on aggregation-induced emission effects as described above and/or the above method for preparing a carbon dot having aggregation-induced emission characteristics and/or the use of the above carbon dot in the fields of bio-imaging, disease research, luminescent display, electronic ink, and anti-counterfeiting. For example, the carbon dots can be used in an ink, and the volume of water in the ink is preferably not less than 70%, for example, not less than 75%, 80%, 85%, or 90%, so that aggregation of the carbon dots and generation of fluorescence can be more facilitated, and the ink can be used for specific applications such as luminescent coloration or forgery prevention. Compared with the prior art, the carbon dot precursor, the preparation method or the carbon dot used for the purpose has stronger applicability, better effect and more stability. It should be noted that the features and effects described for the carbon dot precursor based on aggregation-induced emission effect, the method for preparing the carbon dot with aggregation-induced emission characteristics, and the carbon dot are also applicable to the application, and are not repeated herein.

The following describes embodiments of the present invention in detail. The following examples are illustrative only and are not to be construed as limiting the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

Example 1

Weighing TPE-NH₂(0.35g, 1mmol) and 60mL of acetic acid were placed in a 100mL conical flask, stirred ultrasonically for 30min, transferred to a 100mL polytetrafluoroethylene-lined reaction kettle, and then the reaction kettle was placed in an electrothermal constant temperature forced air drying oven at 180 ℃ for reaction for 12 h. The reaction solution was extracted with dichloromethane and a large amount of deionized water to remove a large amount of acetic acid, and the organic phase was dried over anhydrous magnesium sulfate, filtered by suction, and spin-dried. Performing column chromatography separation with dichloromethane/methanol of different ratios as eluent, and spin-drying to obtain purified off-white carbon dot powder named as CDs-TPE-NH₂。

Example 2

Weighing TPE-2NH₂(0.37g, 1mmol) and 60mL of acetic acid were placed in a 100mL Erlenmeyer flask, ultrasonically stirred for 30min, transferred to a 100mL Teflon lined reactor, and then allowed to standThen the reaction kettle is placed in an electric heating constant temperature air blast drying oven at 180 ℃ for reaction for 12 hours. The reaction solution was extracted with dichloromethane and a large amount of deionized water to remove a large amount of acetic acid, and the organic phase was dried over anhydrous magnesium sulfate, filtered by suction, and spin-dried. Performing column chromatography with dichloromethane/methanol of different ratios as eluent, and spin-drying to obtain yellow purified carbon dot powder named as CDs-TPE-2NH₂。

For CDs-TPE-NH in examples 1 and 2₂And CDs-TPE-2NH₂And performing characterization on a transmission electron microscope, X-ray diffraction, infrared spectrum, X-ray photoelectron spectrum and fluorescence spectrum.

Transmission Electron microscopy and high resolution Transmission Electron microscopy (HR-TEM) on CDs-TPE-NH₂And CDs-TPE-2NH₂Basic structural characterization was performed. As can be seen from FIGS. 1-2, CDs-TPE-NH₂And CDs-TPE-2NH₂All are uniform monodisperse spheres, but the average particle sizes are different and are respectively 6.8nm and 4.2 nm. There are more lattice fringes under HR-TEM and well-resolved lattice fringes can be seen from the interpolated plot, with lattice spacings of 0.315nm and 0.246nm, respectively, consistent with the (002) and (100) planes of the graphitic structure. As shown in FIG. 3((a) and (b)), there are many sharp diffraction peaks with different sizes on the XRD pattern, indicating CDs-TPE-NH₂And CDs-TPE-2NH₂Has high crystallinity. The analysis results of TEM and XRD are combined to show that the two carbon points are graphite-like structures.

Using FT-IR spectroscopy, XPS spectroscopy and¹the H NMR spectrum was further analyzed for chemical structure and surface state of the carbon dots. Starting material (TPE-NH)₂And TPE-2NH₂) And carbon dots (CDs-TPE-NH)₂And CDs-TPE-2NH₂) The FT-IR spectrum of (a) is shown in FIG. 4((a) and (b)), at 1675cm^-1The newly appeared absorption peak was attributed to the C ═ O stretching vibration peak in the amide, indicating that the starting material (TPE-NH)₂And TPE-2NH₂) The amino group in the intermediate and a solvent acetic acid have dehydration condensation reaction; 3000cm^-1And 1600/1500cm^-1The left and right aromatic rings C-H and C ═ C tensile vibration absorption peaks are present in the raw material and carbon points, indicating that CDs-TPE-NH₂And CDs-TPE-2NH₂Containing TPE-NH₂And TPE-2NH₂So that CDs-TPE-NH are present₂And CDs-TPE-2NH₂Also has hydrophobic properties. TPE-NH₂The amino group of (B) is mainly embodied at 3400cm^-1Two stretching vibration absorption peaks at N-H and 1618cm^-1The absorption peak of N-H bending vibration is shown, and CDs-TPE-NH is obtained after amidation and carbonization₂The absence of the vibration absorption peak of the amino group indicates that the carbon dot does not contain the amino group, while the carbon dot in FIG. 4(b) still contains the absorption peak related to the amino group, thereby indicating that CDs-TPE-2NH₂The surface contains amino groups. CDs-TPE-NH₂And CDs-TPE-2NH₂Also has hydrophobic properties.

With DMSO-d6 (CD)₃SOCD₃) Used as deuterated solvent to measure CDs-TPE-NH₂And CDs-TPE-2NH₂Is/are as follows¹H NMR and nuclear magnetic hydrogen spectrum As shown in FIG. 5, the peak at 11.96ppm was attributed to hydroxyl hydrogen, the peak at 9.85ppm was attributed to carboxyl hydrogen, and the strong peak between 6.5 and 7.5ppm was attributed to aromatic hydrogen. TPE-NH as raw material₂The amino group in (A) almost disappeared after amidation and carbonization, indicating that CDs-TPE-NH₂Does not contain amino groups, while the peak between 5 and 6ppm in FIG. 5(b) is an amino hydrogen, which indicates that CDs-TPE-2NH₂Contains amino groups.

XPS analysis of CDs-TPE-NH₂And CDs-TPE-2NH₂Chemical composition and morphology. It can be seen from FIG. 6((a) - (b)) that the two carbon dot surfaces contain C, N and O, wherein the O content is not much different, and the main difference is in the C and N contents, which is reflected in the CDs-TPE-2NH₂The surface N content was 6.1%, while CDs-TPE-NH₂The N content of (A) is only 3.6%, probably due to TPE-2NH₂Is in itself better than TPE-NH₂Contains more than one amino group, but does not participate in the reaction. Referring to FIGS. 6(c) and (f), CDs-TPE-NH₂And CDs-TPE-2NH₂C1s was mainly divided into three peaks at 284.1eV, 285.1eV (285.3eV) and 291.5eV (290.4eV), respectively, and corresponded to C/C-C, C-O and C ═ O. Referring to FIGS. 6(d) and (g), CDs-TPE-NH₂And CDs-TPE-2NH₂There are some differences in the high resolution N1s spectra, 398.6eV, 399.8/399.5eV and 400.7eV for pyridine N (pyridinic N), pyrrole N (pyrolic N) and amino N (amino N), respectively, thus demonstrating thatCDs-TPE-2NH₂The surface contains amino groups. Referring to fig. 6(e) and (h), in the high-resolution spectrum of O1s, peaks located at 531.9eV (531.2eV) and 532.9eV (532.0eV) correspond to C ═ O and C — O. Combining FT-IR spectroscopy, XPS spectroscopy and¹the analysis result of the H NMR spectrum shows that the prepared CDs-TPE-NH₂And CDs-TPE-2NH₂The surface of the material is rich in O/N-containing groups, CDs-TPE-NH₂The surface contains a large amount of hydroxyl and carboxyl, CDs-TPE-2NH₂Hydroxyl, carboxyl and amino groups contained on the surface.

CDs-TPE-NH₂And CDs-TPE-2NH₂The UV-visible absorption spectrum and the fluorescence spectrum of the sample are shown in FIG. 7, and it can be seen from FIGS. 7(a) and (d) that CDs-TPE-NH is present₂And CDs-TPE-2NH₂Has a maximum absorption wavelength of about 319nm and 325nm, respectively, which can be attributed to n-pi transition of C ═ O bond (") and the change of solvent to CDs-TPE-NH₂And CDs-TPE-2NH₂Does not change significantly. As can be seen from the fluorescence spectra (FIGS. 7(c) and (f)), CDs-TPE-NH were observed when the excitation wavelength was varied between 300 and 410nm₂The fluorescence emission of the powder was maintained at about 459nm, and it was judged that it had excitation-independent fluorescence characteristics, and the Quantum Yield (QY) of the powder was 34.7%. When the excitation wavelength is increased from 290nm to 370nm, CDs-TPE-2NH₂The emission peak is kept at 458nm, which is similar to that of CDs-TPE-NH₂While the excitation wavelength continues to increase to 430nm, the position of the emission peak is red-shifted to some extent, with a relatively low QY.

Example 3

TPE-2OH (0.37g, 1mmol) and 60mL of acetic acid are weighed into a 100mL conical flask, stirred ultrasonically for 30min, transferred into a 100mL reaction kettle with a polytetrafluoroethylene lining, and then placed in an electric heating constant-temperature air drying oven at 180 ℃ for reaction for 12 h. The reaction solution was extracted with dichloromethane and a large amount of deionized water to remove a large amount of acetic acid, and the organic phase was dried over anhydrous magnesium sulfate, filtered by suction, and spin-dried. Performing column chromatography separation by using dichloromethane/methanol with different ratios as eluent, and spin-drying to obtain purified off-white powder, which is named as CDs-TPE-2 OH.

FIGS. 8(a) and 8(b) are transmission electron micrograph and particle size distribution plots, respectively, of CDs-TPE-2OH, showing that the samples were well dispersed and similar in average particle size, about 5 nm. There were fewer lattice fringes under HR-TEM with a lattice spacing of 0.300nm, corresponding to the (100) in-plane lattice of graphene. The XRD pattern of CDs-TPE-2OH (fig. 9) has a broad diffraction peak at 2 θ ═ 20 °. This indicates that CDs-TPE-2OH is an amorphous structure with graphite clusters.

FIG. 10 is a graph showing FT-TR spectra for TPE-2OH and CDs-TPE-2OH, CDs-TPE-2OH at 1750cm compared to TPE-2OH^-1A new absorption peak appears, and the expansion vibration peak of C ═ O which is proved to belong to an ester bond proves that TPE-2OH and acetic acid have dehydration reaction under the catalysis of solvent acetic acid. 3435. 3000, 1600-1500, 1200cm^-1The absorption peaks are respectively O-H stretching vibration peak, C-H stretching vibration peak on aromatic ring, C ═ C stretching vibration peak on aromatic hydrocarbon and C-O stretching vibration peak, and the four obvious absorption peaks exist in TPE-2OH and CDs-TPE-2OH, which shows that CDs-TPE-2OH contains most functional groups in TPE-2OH, so that CDs-TPE-2OH and TPE-2OH have hydrophobicity as well. CDs-TPE-2OH contains both C and O elements and its C1s spectrum can be decomposed into three components with binding energies of about 284.1, 285.5, and 288.7eV, respectively, due to C/C-C, C-O and C ═ O, respectively (fig. 11). XPS and FT-IR analysis results on the chemical components of the CDs-TPE-2OH surface are consistent, and the surface of the carbon dot contains a large number of aromatic rings, carboxyl and hydroxyl. The presence of these groups renders the carbon dots hydrophobic and also offers the possibility of aggregation-induced fluorescence enhancement properties of the carbon dots, since rotational vibration of these groups in organic solvents is suppressed. With DMSO-d6 (CD)₃SOCD₃) Used as deuterated solvent to detect CDs-TPE-2OH¹H NMR (FIG. 12), peaks between 8 and 10ppm are carboxyl hydrogens, and strong peaks between 6.0 and 7.5ppm are aromatic ring hydrogens. Integration of all FT-IR, XPS and¹as a result of analysis of the H NMR spectrum, the CDs-TPE-2OH surface contains a large number of aromatic rings, hydroxyl groups and carboxyl groups.

The UV-visible absorption spectrum of CDs-TPE-2OH in different solvents (FIG. 13(a)) shows that the absorption spectrum shape of the carbon dot under different polarities does not change significantly, and the maximum absorption wavelength is locatedApproximately around 305 nm. The CDs-TPE-2OH powder emits blue light under 365nm ultraviolet lamp irradiation, and the quantum yield is 10.2%. As shown in FIG. 13(c), the emission peak of CDs-TPE-2OH shows a property (λ. lambda. independently of the excitation wavelength) when the excitation wavelength is increased from 300nm to 470nm_em485nm) and the maximum fluorescence intensity was obtained at an excitation wavelength of 370 nm.

CDs-TPE-2NH prepared in examples 1 and 2₂The performance test was carried out, and the specific test was as follows:

1. stability to acid test

Preparation of 0.004mg/mL TPE-NH₂、TPE-2NH₂、CDs-TPE-NH₂And CDs-TPE-2NH₂THF solution of (D) as fluorescent ink was written on a thin layer chromatography silica gel plate (written sequentially as T-NH)₂、T-2NH₂、C-NH₂And C-2NH₂). From FIG. 14, it can be seen that TPE-NH is present on solar thin layer chromatography silica gel plates₂、CDs-TPE-NH₂And CDs-TPE-2NH₂Are all colorless, and TPE-2NH₂Is light yellow; and all the fluorescent materials fluoresce under 365nm UV excitation. After being fumigated by trifluoroacetic acid (TFA), TPE-NH₂And TPE-2NH₂Fluorescence quenching occurred, but CDs-TPE-NH₂And CDs-TPE-2NH₂The fluorescence of (A) has no obvious change within 5min, TPE-NH₂And TPE-2NH₂Leave a yellow mark (TPE-2 NH) in the daylight₂More yellow in color), CDs-TPE-2NH₂It also has a slight yellow color due to CDs-TPE-2NH₂The amino group contained on the surface reacts with acid, thereby illustrating that CDs-TPE-NH₂Has higher acid stability.

2. Cellular imaging

CDs-TPE-NH using confocal microscopy₂And CDs-TPE-2NH₂HepG2 cells were introduced for in vitro bioimaging. HepG2 cells were mixed with 15.625mg/mL CDs-TPE-NH, respectively₂And CDs-TPE-2NH₂Incubate for 24h and wash three times with PBS. As shown in FIG. 15, under 405nm laser excitation, blue fluorescence was observed in the cells, which was mainly present in the cytoplasmic region but not observed on the nucleus, indicating that CDs-TPE-NH₂And CDs-TPE-2NH₂Can be used for the marking of HepG 2.

CDs-TPE-NH prepared in examples 1 and 2₂And CDs-TPE-2NH₂The luminescence mechanism of (a) is analyzed as follows:

CDs-TPE-NH₂and CDs-TPE-2NH₂The fluorescence change patterns in the DMSO/water mixed solvent are shown in FIGS. 16((a) - (d)), respectively. CDs-TPE-NH₂The fluorescence intensity begins to increase as the water content increases to 70% by volume, and still increases as the water content continues to increase. And CDs-TPE-2NH₂At a water content of 90% by volume, the fluorescence intensity begins to increase and also shows a tendency to increase. Both of them show AIE (aggregation induced emission) property, but the intensity of the emitted light is greatly different, CDs-TPE-NH₂And CDs-TPE-2NH₂This is also demonstrated by the solid state Quantum Yield (QY) of (a). For CDs-TPE-NH with water volume content of 0%, 50% and 90%₂And CDs-TPE-2NH₂Dynamic light scattering particle size analysis was performed (FIGS. 17(e) - (j)), and the particle size gradually increased with increasing water volume content, indicating that increasing water content resulted in CDs-TPE-NH₂And CDs-TPE-2NH₂Aggregation occurs to a certain extent, fluorescence begins to be generated, and the same is reflected by the fact that the fluorescence is generated by the CDs-TPE-NH₂And CDs-TPE-2NH₂Is hydrophobic. From the FT-IR spectrum, CDs-TPE-NH₂And CDs-TPE-2NH₂The surface contains a large number of aromatic rings which can freely vibrate or rotate in an organic solvent, and the energy of an excited state is consumed in this way; in the aggregation state or solid state, the movement of the aromatic ring on the surface of the carbon dot is limited, so that the CDs-TPE-NH₂And CDs-TPE-2NH₂Is suppressed, radiative transition is enhanced, CDs-TPE-NH₂And CDs-TPE-2NH₂The luminous intensity of (a) is increased to various degrees.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.