Method for large-scale preparation of different fluorescence emission carbon dots in solvent engineering

Abstract

The invention discloses a method for large-scale preparation of different fluorescence emission carbon dots in solvent engineering, which comprises the following steps: by taking aromatic anhydride derivatives and aromatic amine derivatives as raw materials, regulating and controlling the proportion and reaction time of the raw materials through a one-step microwave-assisted method to prepare four CDs emitted from blue fluorescence to red fluorescence; the fluorescence quantum yields are respectively 28.6%, 26.8%, 20.9% and 7.8%. The CDs can be prepared on a large scale under normal pressure through amplification of reactants, and large-scale production of the fluorescent CDs with different wavelengths is achieved. The prepared fluorescent CDs with different wavelengths have rich surface functional groups, high fluorescence quantum yield, uniform particle size distribution and biocompatibility, can be massively synthesized in a short time, and can be widely applied to the fields of analysis and detection, information encryption, cell imaging, disease diagnosis and treatment and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of zero-dimensional carbon quantum dot nanomaterials, and specifically relates to a method for preparing different fluorescent emission carbon dots on a large scale by solvent engineering. Background Art

[0002] Carbon dots (CDs) are a type of carbon nanomaterial with a size of nanometers, usually less than 10 nm. They exhibit fluorescent properties and have good chemical stability. They have application potential in many fields such as optoelectronic devices, biological imaging, analytical detection, and disease diagnosis and treatment.

[0003] Traditional fluorescent nanomaterials, such as organic fluorescent molecules and semiconductor quantum dots, contain toxic substances such as heavy metals, and long-term reactions under high temperature and high pressure lead to high production costs and low production efficiency, which limits their large-scale production and application. As an ideal substitute, the large-scale synthesis of CDs has become a research hotspot. With the continuous deepening of theoretical research on the luminescence mechanism of CDs, such as the discovery of the aggregation-induced emission effect, theoretical guidance has been provided for the large-scale synthesis of CDs with specific luminescence properties, which helps to achieve controllable preparation of different luminescent CDs by controlling reaction conditions. It provides technical support and innovative ideas for the large-scale synthesis of different luminescent CDs, which can accelerate the research and development process, reduce costs, and accurately control the luminescence mechanism.

[0004] The current preparation methods of CDs have the problems of cumbersome preparation process, long reaction time and low fluorescence quantum yield; therefore, there is an urgent need for a method for large-scale synthesis of highly fluorescent CDs emitting at different wavelengths. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing different fluorescent emission carbon dots on a large scale by solvent engineering, which has simple steps, low-cost and readily available raw materials, simple purification steps, short reaction time, high fluorescence quantum yield, can be prepared on a large scale, and has broad application prospects.

[0006] The present invention provides a method for preparing different fluorescent emission carbon dots on a large scale by solvent engineering, comprising the following steps:

[0007] S1. The aromatic anhydride derivatives and aromatic amine derivatives are dissolved in a predetermined ratio of the dispersion system to obtain a dispersion;

[0008] S2. Ultrasonic treatment of the dispersion obtained in step S1 for a preset time to obtain an ultrasonic dispersion;

[0009] S3. The dispersion obtained in step S2 after ultrasonic treatment is subjected to microwave-assisted heating. After the reaction time is preset, it is cooled to room temperature, an aprotic solvent is added, and the dispersion is centrifuged and filtered. Ultrapure water is then added to the supernatant, and the precipitate is collected to obtain fluorescent carbon dots (CDs).

[0010] Specifically, in step S1, the aromatic anhydride derivatives include one or more of benzoic anhydride, benzoic anhydride, p-toluic anhydride, 4-chlorobenzoic anhydride, 1,2,4,5-pyromellitic anhydride, 2,4,6-trimethylbenzoic anhydride, 2,3,4,5,6-pentafluorobenzoic anhydride, 3-methylbenzene-1-carboxylic anhydride, tetraiodo-2-sulfonic acid benzoic anhydride, 3-dimethylaminobenzoic anhydride, 4-trifluoromethylbenzoic anhydride and biphenyl anhydride.

[0011] Furthermore, the aromatic anhydride derivative is preferably 1,2,4,5-pyromellitic anhydride.

[0012] The aromatic amine derivatives include one or more of aniline, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-toluenediamine, toluenediamine, 3,4-toluenediamine, 4-fluoro-o-phenylenediamine, and 2-chloro-1,4-p-phenylenediamine.

[0013] Furthermore, the aromatic amine derivative is preferably o-phenylenediamine.

[0014] The molar ratio of the benzoic anhydride derivative to the aniline derivative is (100-1):1.

[0015] When the target product is blue light carbon dots, the molar ratio of the benzoic anhydride derivative to the aniline derivative is (100:1-20:1);

[0016] When the target product is green carbon dots, the molar ratio of the benzoic anhydride derivative to the aniline derivative is (20:1-10:1);

[0017] When the target product is yellow carbon dots, the molar ratio of the benzoic anhydride derivative to the aniline derivative is (10:1-5:2);

[0018] When the target product is red-light carbon dots, the molar ratio of the benzoic anhydride derivative to the aniline derivative is (5:2-1:1).

[0019] The dispersion system includes one or more of an ethanol and water dispersion system, a methanol and water dispersion system, a tetrahydrofuran and water dispersion system, an acetonitrile and water dispersion system, a formamide and water dispersion system, and an N,N-dimethylformamide and water dispersion system.

[0020] Furthermore, the dispersion system is preferably an ethanol and water dispersion system.

[0021] Specifically, in step S2, the preset time of the ultrasonic treatment is 0 to 1 hour.

[0022] In step S3, the reaction temperature of the microwave-assisted heating is 100 to 250° C., and the reaction time is 0 to 30 min;

[0023] The aprotic solvent includes one or more of diethyl ether, tetrahydrofuran, dioxane, chloroform, dichloromethane, carbon tetrachloride, acetone, pyridine, acetonitrile, formamide, and dimethyl sulfoxide.

[0024] Furthermore, the aprotic solvent is preferably DMSO.

[0025] Specifically, the process conditions of the centrifugal filtration are: a centrifugal speed of 100 to 9000 rpm, a centrifugal time of 0.1 to 1 h; an organic phase microporous filter membrane is used for filtration; and the pore size of the organic phase microporous filter membrane is 0.22 to 0.45 μm.

[0026] Furthermore, the centrifugal speed is preferably 3000 rpm, the centrifugal time is preferably 10 min, and the pore size of the organic phase microporous filter membrane is preferably 0.22 μm.

[0027] Beneficial effects of the present invention:

[0028] (1) The present invention discloses a method for preparing carbon dots with different fluorescence emission by solvent engineering on a large scale. By adjusting the ratio of aromatic anhydride derivatives and aromatic amine derivatives, the reaction time and the reaction temperature, the emission wavelength of the prepared CDs is changed to prepare four narrow emission CDs with different fluorescence, thereby realizing the large-scale preparation of blue, green, yellow and red CDs.

[0029] (2) The raw materials used in the method of the present invention are green, safe and easy to obtain, the reaction conditions are mild, the preparation steps are simple, the reaction time is short, the post-treatment is convenient and fast, and the equipment requirements are low;

[0030] (3) The CDs prepared by the method of the present invention have high yield and fluorescence quantum yield, uniform size, rich surface functional groups and good photostability;

[0031] (4) The CDs of the present invention can be synthesized in large quantities in a short time and can be widely used in the fields of analysis and detection, information encryption, cell imaging, disease diagnosis and treatment, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of transmission electron microscopy of four narrow emission CDs emitting blue light, green light, yellow light and red light synthesized in Example 1;

[0033] Figure 2 This is a luminescence image of the narrow emission CDs synthesized in Example 1 under ultraviolet light irradiation;

[0034] Figure 3 is the UV-visible absorption spectrum of the narrow emission CDs synthesized in Example 1;

[0035] Figure 4is the fluorescence spectrum of the narrow emission CDs synthesized in Example 1;

[0036] Figure 5 is the wavelength-dependent fluorescence spectrum of the narrow emission CDs synthesized in Example 1;

[0037] Figure 6 The narrow emission CDs synthesized in Example 1 were illuminated by a xenon lamp (2 W / cm -2 ) photostability test chart;

[0038] Figure 7 This is a graph showing the cytotoxicity test results of the narrow emission CDs synthesized in Example 1. DETAILED DESCRIPTION

[0039] The present invention is further described below with reference to an embodiment:

[0040] Four groups of 1,2,4,5-pyromellitic anhydride and o-phenylenediamine in different ratios were dissolved in a dispersion solution (300 mL) of ethanol and water at room temperature;

[0041] In the first group, 1,2,4,5-pyromellitic anhydride is 100 g and o-phenylenediamine is 5 g; the mixed dispersion is subjected to ultrasonic treatment for 10 min, then subjected to microwave reaction at 200°C for 10 min, and then naturally cooled to room temperature;

[0042] In the second group, 1,2,4,5-pyromellitic anhydride was 100 g and o-phenylenediamine was 6 g; the mixed dispersion was subjected to ultrasonic treatment for 10 min, then subjected to microwave reaction at 200°C for 12 min, and then naturally cooled to room temperature;

[0043] In the third group, 1,2,4,5-pyromellitic anhydride was 100 g and o-phenylenediamine was 10 g; the mixed dispersion was subjected to ultrasonic treatment for 10 min, then subjected to microwave reaction at 200°C for 16 min, and then naturally cooled to room temperature;

[0044] In the fourth group, 1,2,4,5-benzenetetracarboxylic anhydride is 100 g and o-phenylenediamine is 45 g; the mixed dispersion is subjected to ultrasonic treatment for 10 min, then subjected to microwave reaction at 200° C. for 20 min, and then naturally cooled to room temperature;

[0045] After the four groups of reactions were completed, the solvent was evaporated and dissolved in DMSO. The obtained solution was then centrifuged and filtered at a speed of 3000 rpm for 10 min. The obtained supernatant was filtered through a 0.22 μm organic phase microporous filter membrane, and pure water was added to collect the precipitate to obtain four groups of carbon dots.

[0046] The carbon dots obtained in the first group were B-CDs; the carbon dots obtained in the second group were G-CDs; the carbon dots obtained in the third group were G-CDs; and the carbon dots obtained in the fourth group were R-CDs.

[0047] The fluorescence quantum yields of B-CDs, G-CDs, Y-CDs and R-CDs were 28.6%, 26.8%, 20.9% and 7.8%, respectively.

[0048] The four groups of narrow emission CDs prepared were observed by transmission electron microscope, and the transmission electron microscope images were obtained, such as Figure 1 It can be seen that the size of B-CDs is about 2.1 nm, the size of G-CDs is about 3.2 nm, the size of Y-CDs is about 2.8 nm, and the size of R-CDs is about 3.0 nm, and they are evenly distributed.

[0049] The four groups of narrow emission CDs prepared were excited by ultraviolet light, as shown in the photo. Figure 2 It can be seen that under the excitation of ultraviolet light, the emission of the four narrow emission CDs are blue light, green light, yellow light and red light respectively.

[0050] The prepared four groups of narrow emission CDs were subjected to UV-visible absorption detection to obtain UV-visible absorption spectra, such as Figure 3 UV-visible absorption showed that the main absorption peaks of B-CDs were located at 236nm and 276nm, the main absorption peaks of G-CDs were located at 237nm, 270nm and 410nm, the absorption peak of Y-CDs was located at 400nm, and the absorption peaks of R-CDs were located at 640nm and 670nm.

[0051] The fluorescence spectra of the four groups of narrow emission CDs prepared were detected, and the fluorescence spectra were obtained, such as Figure 4 The results showed that the fluorescence emission peak of B-CDs was located at 430nm, with a half-peak width of 53nm; the fluorescence emission peak of G-CDs was located at 480nm, with a half-peak width of 36nm; the fluorescence emission peak of Y-CDs was located at 530nm, with a half-peak width of 72nm; and the fluorescence emission peak of R-CDs was located at 680nm, with a half-peak width of 26nm.

[0052] The wavelength-dependent fluorescence spectra of the prepared four groups of narrow emission CDs were detected to obtain wavelength-dependent fluorescence spectra, such as Figure 5 The results show that the four CDs show no wavelength dependence.

[0053] The photostability of the four groups of narrow emission CDs prepared was tested. Figure 6 As shown in Figure 2, compared with sodium fluorescein, it can be seen that the four CDs have good photostability.

[0054] The four groups of narrow emission CDs prepared were tested for cytotoxicity, and the results were as follows: Figure 7 As shown in Figure 4, all four CDs have good biosafety.

Claims

1. A method for preparing carbon dots with different fluorescence emission by solvent engineering on a large scale, characterized in that: The following steps are involved: S1. The aromatic anhydride derivatives and aromatic amine derivatives are dissolved in a predetermined ratio of the dispersion system to obtain a dispersion; S2. ultrasonically treating the dispersion obtained in step S1 for a predetermined time to obtain an ultrasonically treated dispersion; S3. The dispersion obtained in step S2 after ultrasonic treatment is subjected to microwave-assisted heating. After the reaction time is preset, it is cooled to room temperature, a non-protonic solvent is added, centrifuged and filtered, ultrapure water is added to the supernatant, and the precipitate is collected to obtain fluorescent emitting carbon dots.

2. The method for preparing carbon dots with different fluorescence emission by solvent engineering on a large scale according to claim 1, characterized in that: In step S1, the aromatic anhydride derivatives include one or more of benzoic anhydride, benzoic anhydride, p-toluic anhydride, 4-chlorobenzoic anhydride, 1,2,4,5-pyromellitic anhydride, 2,4,6-trimethylbenzoic anhydride, 2,3,4,5,6-pentafluorobenzoic anhydride, 3-methylbenzene-1-carboxylic anhydride, tetraiodo-2-sulfonic acid benzoic anhydride, 3-dimethylaminobenzoic anhydride, 4-trifluoromethylbenzoic anhydride and biphenyl anhydride.

3. The method for preparing carbon dots with different fluorescence emission by solvent engineering on a large scale according to claim 1, characterized in that: In step S1, the aromatic amine derivatives include one or more of aniline, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-toluenediamine, toluenediamine, 3,4-toluenediamine, 4-fluoro-o-phenylenediamine, and 2-chloro-1,4-p-phenylenediamine.

4. The method for preparing carbon dots with different fluorescence emission by solvent engineering on a large scale according to claim 1, characterized in that: In step S1, the dispersion system includes one or more of an ethanol and water dispersion system, a methanol and water dispersion system, a tetrahydrofuran and water dispersion system, an acetonitrile and water dispersion system, a formamide and water dispersion system, and an N,N-dimethylformamide and water dispersion system.

5. The method for preparing carbon dots with different fluorescence emission by solvent engineering on a large scale according to claim 1, characterized in that: In step S2, the preset time of the ultrasonic treatment is 0 to 1 hour.

6. The method for preparing carbon dots with different fluorescence emission by solvent engineering on a large scale according to claim 1, characterized in that: The molar ratio of the benzoic anhydride derivative to the aniline derivative is (100-1):

1.

7. The method for preparing carbon dots with different fluorescence emission by solvent engineering on a large scale according to claim 1, characterized in that: When the target product is blue light carbon dots, the molar ratio of the benzoic anhydride derivative to the aniline derivative is (100:1-20:1); When the target product is green carbon dots, the molar ratio of the benzoic anhydride derivative to the aniline derivative is (20:1-10:1); When the target product is yellow carbon dots, the molar ratio of the benzoic anhydride derivative to the aniline derivative is (10:1-5:2); When the target product is red-light carbon dots, the molar ratio of the benzoic anhydride derivative to the aniline derivative is (5:2-1:1).

8. The method for preparing carbon dots with different fluorescence emission by solvent engineering on a large scale according to claim 1, characterized in that: In step S3, the reaction temperature of the microwave-assisted heating is 100-250° C., and the reaction time is 0-30 min.

9. The method for preparing carbon dots with different fluorescence emission by solvent engineering on a large scale according to claim 1, characterized in that: In step S3, the aprotic solvent includes one or more of diethyl ether, tetrahydrofuran, dioxane, chloroform, dichloromethane, carbon tetrachloride, acetone, pyridine, acetonitrile, formamide, and dimethyl sulfoxide.

10. The method for preparing carbon dots with different fluorescence emission by solvent engineering on a large scale according to claim 1, characterized in that: The process conditions of the centrifugal filtration are: a centrifugal speed of 100 to 9000 rpm, a centrifugal time of 0.1 to 1 h; an organic phase microporous filter membrane is used for filtration; and the pore size of the organic phase microporous filter membrane is 0.22 to 0.45 μm.

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