Full-spectrum fluorescent carbon dots as well as preparation method and application thereof

Abstract

The invention provides a full-spectrum fluorescent carbon dot as well as a preparation method and application thereof, and the preparation method of the full-spectrum fluorescent carbon dot comprises the following steps: under an acidic condition, carrying out solvothermal reaction on cyclodextrin and o-phenylenediamine to obtain an initial carbon dot mixed solution; and performing post-treatment on the initial carbon dot mixed liquid to obtain the full-spectrum carbon dots.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of full-spectrum carbon dots, and relates to full-spectrum fluorescent carbon dots and a preparation method and application thereof. Background Art

[0002] Tunable photoluminescence-derived multicolor emitting materials have attracted extensive research interests due to their potential applications in micro-lasers, optical detection, and bio-imaging. Among them, bio-imaging has attracted much attention due to its good photostability and co-localization properties in optical imaging analysis instruments, electrophysiology-related surgical devices, and next-generation imaging devices in our daily lives. Typical materials developed in this field include organic dyes, rare earth compounds, and semiconductor quantum dots (SQDs). However, single wavelength, low quantum yield, and complex and expensive synthesis processes limit the widespread application and development of these materials.

[0003] Carbon dots are a new type of zero-dimensional carbon nanomaterial with luminescent properties. Due to their rich precursor sources, easy surface functionalization, and excellent physical and chemical properties, they are widely used in bioimaging, anti-counterfeiting, optoelectronic devices and other fields. In these applications, the synthesis of multicolor fluorescent carbon dots has an important impact on multi-channel luminescence and multicolor imaging. Although many current research results have obtained bright photoluminescent multicolor fluorescent carbon dots, they require multi-step preparation processes and different reaction conditions. These complex reaction processes limit the actual development of multicolor fluorescent carbon dots and the study of emission mechanisms. Therefore, there is an urgent need for a one-step method for preparing full-spectrum carbon dots to reduce costs and raw material losses.

[0004] In general, carbon dots have become the focus of current research due to their superior physical and chemical properties and excellent biocompatibility. So far, no work has reported the synthesis of full-spectrum photoluminescent carbon dots with multicolor fluorescence using a one-step method. Therefore, it is necessary to develop a simple one-step synthesis method to prepare full-spectrum fluorescent carbon dots to reduce costs and loss of raw materials. Summary of the invention

[0005] In view of the deficiencies of the prior art, the object of the present invention is to provide a full-spectrum fluorescent carbon dot and a preparation method and application thereof. The full-spectrum fluorescent carbon dot of the present invention has high sensitivity, good biocompatibility, and a simple preparation method. The full-spectrum fluorescent carbon dot of the present invention can emit five kinds of fluorescence, namely, purple, blue, green, yellow and red, under different excitations (340, 350, 390, 410 and 540 nm). The full-spectrum fluorescent carbon dot of the present invention has good stability under treatments of different time, different salt concentrations and different pH values.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In one aspect, the present invention provides a method for preparing full-spectrum fluorescent carbon dots, the preparation method comprising the following steps:

[0008] Under acidic conditions, cyclodextrin and o-phenylenediamine (O-PDA) are subjected to a solvothermal reaction to obtain an initial carbon dot mixed liquid; the initial carbon dot mixed liquid is post-treated to obtain the full-spectrum carbon dots.

[0009] Preferably, the acidic condition is an acidic condition with a pH value of 2-3 (eg, 2, 2.3, 2.5, 2.8 or 3).

[0010] Preferably, the acidic substance providing the acidic condition is any one of hydrochloric acid, sulfuric acid or acetic acid, preferably acetic acid. In the present invention, the main elements of the carbon dots are carbon and hydrogen. The use of acetic acid can reduce the doping of elements as little as possible. Although the use of hydrochloric acid and sulfuric acid can also produce the same effect, they will be doped with heteroatoms. Therefore, in the present invention, acetic acid is preferred.

[0011] Preferably, the cyclodextrin is any one of α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin, or a combination of at least two of them.

[0012] Preferably, the mass ratio of cyclodextrin to o-phenylenediamine is 2:1-8:1, for example, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 7:1 or 8:1.

[0013] Preferably, the solvent used in the solvothermal reaction is N,N-dimethylformamide.

[0014] Preferably, the temperature of the solvothermal reaction is 180-200°C (e.g., 180°C, 185°C, 188°C, 190°C, 193°C, 195°C, 198°C or 200°C), and the reaction time is 8-12h (e.g., 8h, 8.5h, 9h, 9.5h, 10h, 11h or 12h).

[0015] Preferably, the post-treatment comprises centrifuging the initial carbon dot mixture, and then filtering the supernatant through a chemical analysis filter paper, or spinning and / or freeze-drying the supernatant to obtain the full-spectrum carbon dots.

[0016] Preferably, after the spin drying and / or freeze drying, high-purity water is used to dissolve the mixture to obtain the full-spectrum carbon dot solution.

[0017] On the other hand, the present invention provides full-spectrum fluorescent carbon dots prepared by the preparation method described above.

[0018] On the other hand, the present invention provides the use of the full-spectrum fluorescent carbon dots as described above in the preparation of biological imaging materials, anti-counterfeiting materials, optical detection materials, micro-laser materials or optoelectronic devices.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The fluorescent carbon dots prepared by the present invention have excellent biocompatibility, are easy to be surface functionalized, have good physical and chemical properties, and have a simple preparation method. Full-spectrum carbon dots are prepared by a one-step preparation method. The preparation process is simple, the cost is low, the operation is easy, and the prepared fluorescent carbon dots have good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 1 is the fluorescence emission diagram of the carbon dots prepared in Example 2 under different excitations;

[0022] Figure 2 The effect of time on the fluorescence emission of carbon dots prepared in Example 2 under different excitations;

[0023] Figure 3 The fluorescence emission of carbon dots prepared in Example 2 under different excitations is affected by different salt concentrations;

[0024] Figure 4 The fluorescence emission effect diagram of the carbon dots prepared in Example 2 at different pH under different excitations;

[0025] Figure 5 The fluorescence emission graphs of the carbon dots prepared in Comparative Example 6 under different excitations;

[0026] Figure 6 The fluorescence emission diagram of the carbon dots prepared in Comparative Example 7 under different excitations. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0028] Example 1

[0029] 1.2 g of β-cyclodextrin and 0.15 g of o-phenylenediamine (O-PDA) were mixed and dissolved in 4 mL of a solution (3.5 mL of DMF and 0.5 mL of (1%) acetic acid). The mixed solution was then transferred to a polytetrafluoroethylene-lined autoclave, heated to 180°C for 8 h, and after the solution was cooled to room temperature, it was centrifuged in a centrifuge to remove impurities to obtain a mixed liquid, which was then spin-dried and freeze-dried to obtain a solid, and then dissolved in high-purity water to obtain a purified carbon dot solution with a concentration of 1 mg / mL.

[0030] Example 2

[0031] 0.6 g of β-cyclodextrin and 0.15 g of o-phenylenediamine (O-PDA) were mixed and dissolved in 4 mL of a solution (3.5 mL of DMF and 0.5 mL of (1%) acetic acid). The mixed solution was then transferred to a polytetrafluoroethylene-lined autoclave, heated to 180°C for 8 h, and after the solution was cooled to room temperature, it was centrifuged in a centrifuge to remove impurities to obtain a mixed liquid, which was then spin-dried and freeze-dried to obtain a solid, and then dissolved in high-purity water to obtain a purified carbon dot solution with a concentration of 1 mg / mL.

[0032] Example 3

[0033] 0.3 g of β-cyclodextrin and 0.15 g of o-phenylenediamine (O-PDA) were mixed and dissolved in 4 mL of a solution (3.5 mL of DMF and 0.5 mL of (1%) acetic acid). The mixed solution was then transferred to a polytetrafluoroethylene-lined autoclave, heated to 180°C for 8 h, and after the solution was cooled to room temperature, it was centrifuged in a centrifuge to remove impurities to obtain a mixed liquid, which was then spin-dried and freeze-dried to obtain a solid, and then dissolved in high-purity water to obtain a purified carbon dot solution with a concentration of 1 mg / mL.

[0034] Example 4

[0035] 0.6 g of β-cyclodextrin and 0.15 g of o-phenylenediamine (O-PDA) were mixed and dissolved in 4 mL of a solution (3.5 mL of DMF and 0.5 mL of (1%) acetic acid). The mixed solution was then transferred to a polytetrafluoroethylene-lined autoclave, heated to 180°C for 16 h, and after the solution was cooled to room temperature, it was centrifuged in a centrifuge to remove impurities to obtain a mixed liquid, which was then spin-dried and freeze-dried to obtain a solid, and then dissolved in high-purity water to obtain a purified carbon dot solution with a concentration of 1 mg / mL.

[0036] Example 5

[0037] 0.6 g of β-cyclodextrin and 0.15 g of o-phenylenediamine (O-PDA) were mixed and dissolved in 4 mL of a solution (3.5 mL of DMF and 0.5 mL of (1%) acetic acid). The mixed solution was then transferred to a polytetrafluoroethylene-lined autoclave, heated to 180°C for 4 h, and after the solution was cooled to room temperature, it was centrifuged in a centrifuge to remove impurities to obtain a mixed liquid, which was then spin-dried and freeze-dried to obtain a solid, and then dissolved in high-purity water to obtain a purified carbon dot solution with a concentration of 1 mg / mL.

[0038] Example 6

[0039] 0.6 g of β-cyclodextrin and 0.15 g of o-phenylenediamine (O-PDA) were mixed and dissolved in 8 mL of a solution (7 mL of DMF and 1 mL of (1%) acetic acid). The mixed solution was then transferred to a polytetrafluoroethylene-lined autoclave, heated to 180°C for 8 h, and after the solution was cooled to room temperature, it was centrifuged in a centrifuge to remove impurities to obtain a mixed liquid, which was then spin-dried and freeze-dried to obtain a solid, and then dissolved in high-purity water to obtain a purified carbon dot solution with a concentration of 1 mg / mL.

[0040] Example 7

[0041] 100 μL of the carbon dot solution prepared in Examples 1-6 was taken, and high-purity water was added to prepare a carbon dot solution with a concentration of 0.5 mg / mL. The carbon dot solution was placed in a fluorescence spectrometer to detect the fluorescence.

[0042] The carbon dots of Examples 1-6 can produce multi-color fluorescence.

[0043] Example 8

[0044] 100 μL of the carbon dot solution prepared in Example 2 was taken and high-purity water was added to prepare a carbon dot solution with a concentration of 0.5 mg / ml. The fluorescence intensity of the carbon dot solution was measured by a fluorescence spectrophotometer at room temperature to observe the change in fluorescence intensity over time.

[0045] Figure 1 The fluorescence emission diagram of carbon dots under different excitations was obtained in Example 2. Figure 1 It can be seen that the carbon dots have multicolor fluorescence emission peaks in the range of 380nm to 613nm under different excitation conditions, indicating that the prepared carbon dots have full-spectrum characteristics and can produce a variety of fluorescence.

[0046] like Figure 2 As shown, the analysis results found that under different excitation wavelengths, the fluorescence intensity of the β-cyclodextrin-derived full-spectrum fluorescent carbon dots remained unchanged as time increased, indicating that the carbon dots had good photostability.

[0047] Example 9

[0048] 100 μL of the carbon dot solution prepared in Example 2 was taken to prepare a carbon dot solution with a concentration of 0.5 mg / ml. At room temperature, the carbon dot solution was measured by fluorescence spectrophotometer. Different concentrations of salt solution (0, 0.02, 0.04, 0.06, 0.08, 0.10 mol / L) were added to the carbon dot solution to observe the change in the fluorescence intensity of the carbon dots. Figure 3 As shown, the analysis results show that under different excitation wavelengths, the fluorescence intensity of the full-spectrum fluorescent carbon dots derived from β-cyclodextrin fluctuates within a narrow range as the concentration of the salt solution increases when excited at different excitation wavelengths, which also indicates that the carbon dots have good photostability.

[0049] Example 10

[0050] 100 μL of the carbon dots prepared in Example 2 was taken to prepare carbon dots with a concentration of 0.5 mg / ml. At room temperature, solutions with different pH values ​​(1 to 14) were added to the carbon dot solution to observe the change in the fluorescence intensity of the carbon dots using a fluorescence spectrophotometer. Figure 4 As shown, the analysis results found that under different excitation wavelengths, the fluorescence intensity of the β-cyclodextrin-derived full-spectrum fluorescent carbon dots remained stable, indicating that the carbon dots had good photostability.

[0051] Embodiment 11

[0052] 0.6 g of β-cyclodextrin and 0.15 g of o-phenylenediamine (O-PDA) were mixed and dissolved in 4 mL of a solution (3.5 mL of DMF and 0.5 mL of (1%) acetic acid). The mixed solution was then transferred to a polytetrafluoroethylene-lined autoclave, heated to the temperature shown in Table 1, and reacted for 8 h. After the solution was cooled to room temperature, it was centrifuged in a centrifuge to remove impurities to obtain a mixed liquid, which was then spin-dried and freeze-dried to obtain a solid, and then dissolved in high-purity water to obtain a purified carbon dot solution.

[0053] The obtained carbon dot solution was adjusted to a concentration of 0.5 mg / ml. The fluorescence quantum yield of the carbon dot solution at different excitation wavelengths was measured by a fluorescence spectrophotometer at room temperature. Table 1 shows the fluorescence quantum yield of the carbon dot solution.

[0054] Table 1

[0055]

[0056] Example 12

[0057] 0.6 g of β-cyclodextrin and 0.15 g of o-phenylenediamine (O-PDA) were mixed and dissolved in 4 mL of a solution (3.5 mL of DMF and 0.5 mL of (1%) acetic acid). The mixed solution was then transferred to a polytetrafluoroethylene-lined autoclave, heated to 180° C., and reacted for the time shown in Table 2. After the solution was cooled to room temperature, it was centrifuged in a centrifuge to remove impurities to obtain a mixed liquid, which was then spin-dried and freeze-dried to obtain a solid, which was then dissolved in high-purity water to obtain a purified carbon dot solution.

[0058] The obtained carbon dot solution was adjusted to a concentration of 0.5 mg / ml. The fluorescence quantum yield of the carbon dot solution at different excitation wavelengths was measured by a fluorescence spectrophotometer at room temperature. Table 2 shows the fluorescence quantum yield of the carbon dot solution.

[0059] Table 2

[0060]

[0061]

[0062] Comparative Example 1

[0063] Blue fluorescent o-phenylenediamine functionalized carbon quantum dots were synthesized by reacting citric acid with o-phenylenediamine at 185°C for 5 hours (for example, reported by Wenxian Wang et al. in Ultrasensitive and selective fluorescence recognition of selenite by o-phenylenediamine functionalized carbon quantumdots, New J.Chem., 2022, 46, 19712-19721); it produces monochromatic fluorescent carbon dots.

[0064] Comparative Example 2

[0065] Yellow fluorescent carbon quantum dots can be synthesized by reacting taurine and o-phenylenediamine at 200°C for 8 h in a pH 7.0 system (for example, Anqi Hu et al. reported in o-phenylenediamine Derived Fluorescent Carbon Quantum dots for Detection of Hg(II) in Environmental Water, Journal of Fluorescence, 2024, 34, 905-913), and the obtained carbon dots are monochromatic fluorescent.

[0066] Comparative Example 3

[0067] Yellow fluorescent carbon quantum dots can be synthesized by reacting dicyandiamide and o-phenylenediamine at 200°C for 9 hours (for example, as reported by MinTian et al. in Yellow-emitting carbon dots for selective detecting 4-NP in aqueousmedia and living biological imaging, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2019, 220(5), 117117). Monochromatic fluorescent carbon dots are obtained.

[0068] Comparative Example 4

[0069] Blue fluorescent carbon quantum dots can be synthesized by reacting β-cyclodextrin and citric acid at 140°C for 12 hours (for example, as reported by Wenxian Wang et al. in Ultrasensitive and selective fluorescence recognition of selenite by o-phenylenediamine functionalized carbon quantum dots, RSC Adv., 2022, 12, 30104-30112), which are monochromatic fluorescent carbon dots.

[0070] Comparative Example 5

[0071] Blue fluorescent carbon dots were synthesized by using β-cyclodextrin and phenylboronic acid at 180°C for 4 hours (reported by Meijuan Liang et al., Surface engineering of carbon dots for highly sensitive α-glucosidase and inhibition evaluation, Chinese Chemical Letters, 2024, 35(3), 108573), which are monochromatic fluorescent carbon dots.

[0072] Comparative Example 6

[0073] In this comparative example, only β-cyclodextrin was used to prepare carbon dots, and the preparation method was as follows:

[0074] 1.2 g of β-cyclodextrin was dissolved in 4 mL of solution (3.5 mL of DMF and 0.5 mL of (1%) acetic acid) and stirred for 5 min to form a uniform mixed solution. The mixed solution was then transferred to a stainless steel autoclave lined with polytetrafluoroethylene and heated to 180 ° C for 8 h. After the solution was cooled to room temperature, the resulting solution was centrifuged to remove the solid black precipitate and dried using a rotary evaporator to obtain CDs-3 solid.

[0075] CDs-3 solid was added to high-purity water to prepare a 0.5 mg / mL carbon dot solution, and the carbon dot solution was placed in a fluorescence spectrometer to detect the fluorescence. The results are as follows: Figure 5 As shown, it can be seen that it cannot produce multi-color fluorescence.

[0076] Comparative Example 7

[0077] In this comparative example, only o-phenylenediamine was used to prepare carbon dots, and the preparation method was as follows:

[0078] Briefly, 0.3 g of o-phenylenediamine was dissolved in 4 mL of a solution (3.5 mL of DMF and 0.5 mL of (1%) acetic acid) and stirred for 5 min to form a uniform mixture. Subsequently, the solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and heated to 180 ° C for 8 h. After cooling to room temperature, the solution was centrifuged at 11000 rpm for 10 min to remove the precipitate, and then the solution was dried using a rotary evaporator to obtain CDs-1 solid.

[0079] CDs-1 solid was added to high-purity water to prepare a 0.5 mg / mL carbon dot solution, and the carbon dot solution was placed in a fluorescence spectrometer to detect the fluorescence. The results are as follows: Figure 6 As shown, it can be seen that it can produce two kinds of fluorescence, which is not as much as the fluorescence produced by Example 2.

[0080] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate the full-spectrum fluorescent carbon dots and the preparation method and application thereof, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing full-spectrum fluorescent carbon dots, characterized in that: The preparation method comprises the following steps: Under acidic conditions, cyclodextrin and o-phenylenediamine are subjected to a solvothermal reaction to obtain an initial carbon dot mixed liquid; the initial carbon dot mixed liquid is post-treated to obtain the full-spectrum carbon dots.

2. The preparation method according to claim 1, characterized in that: The acidic condition is an acidic condition with a pH value of 2-3; Preferably, the acidic substance providing the acidic condition is any one of hydrochloric acid, sulfuric acid or acetic acid, preferably acetic acid.

3. The preparation method according to claim 1 or 2, characterized in that: The cyclodextrin is any one of α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin, or a combination of at least two of them.

4. The preparation method according to any one of claims 1 to 3, characterized in that The mass ratio of the cyclodextrin to o-phenylenediamine is 2:1-8:

1.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The solvent used in the solvothermal reaction is N,N-dimethylformamide.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The temperature of the solvent thermal reaction is 180-200° C., and the reaction time is 8-12 hours.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The post-treatment includes centrifuging the initial carbon dot mixture, and then filtering the supernatant through chemical analysis filter paper, or spinning and / or freeze-drying the supernatant to obtain the full-spectrum carbon dots.

8. The preparation method according to claim 7, characterized in that: After the spin drying and / or freeze drying, the solution is dissolved in high-purity water to obtain the full-spectrum carbon dot solution.

9. The full-spectrum fluorescent carbon dots prepared according to the preparation method according to any one of claims 1 to 8.

10. Use of the full-spectrum fluorescent carbon dots according to claim 9 in the preparation of biological imaging materials, anti-counterfeiting materials, optical detection materials, micro-laser materials or optoelectronic devices.

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