Method for synthesizing multicolor fluorescent carbon dots in one pot by taking radix saposhnikoviae as carbon source

Abstract

The invention belongs to the field of luminescent carbon nanomaterials, and provides a method for synthesizing multicolor fluorescent carbon dots in one pot by taking radix saposhnikoviae as a carbon source. According to the method, divaricate saposhnikovia root is taken as a carbon source, p-phenylenediamine is taken as a nitrogen source, ethanol and hydrochloric acid are taken as solvents for synthesis reaction, and operation is convenient. The obtained multicolor fluorescent carbon dots are extremely high in stability and do not have excitation dependence, an emission spectrum covers the whole visible light area, and complete separation of different fluorescent colors can be achieved only through column chromatography.

Description

Technical Field

[0001] The invention belongs to the field of luminescent carbon nanomaterials, and particularly relates to a method for synthesizing multicolor fluorescent carbon dots in one pot by using windproof as a carbon source. Background Art

[0002] In the current field of materials science, carbon dots (CDs), as a new type of nanomaterial, have received extensive attention and in-depth research due to their unique optical properties, good biocompatibility and low toxicity. Traditional carbon dot synthesis methods often have problems such as cumbersome steps, high costs, and the use of toxic and hazardous chemical reagents, which to some extent limit their large-scale application and development.

[0003] With the continuous pursuit of sustainable development and green chemistry concepts, the use of biomass as a carbon source to synthesize carbon dots has gradually become a research hotspot. Biomass resources are abundant, renewable and environmentally friendly, and are an ideal alternative carbon source. However, the existing biomass-based synthesis of CDs technologies has some limitations, such as difficulty in achieving full-color regulation, complex synthesis process, unstable performance of the obtained products, low fluorescence intensity, excitation dependence, and difficulty in purification.

[0004] The demand for multicolor fluorescent carbon dots is becoming increasingly prominent in many fields, such as display technology, bio-imaging, photocatalysis, etc. Therefore, providing a new biomass to synthesize carbon dots with full-color luminescence performance will greatly promote the application expansion of carbon dot materials and bring new development opportunities to related industries. Summary of the invention

[0005] The purpose of the present invention is to provide a method for synthesizing multicolor fluorescent carbon dots in one pot using silanol as a carbon source. The method has a simple synthesis process and can obtain multicolor fluorescent carbon dots with stable emission and covering the visible light region without further modification.

[0006] To achieve the above objectives, the present invention provides the following technical solutions: A method for synthesizing multicolor fluorescent carbon dots in one pot using bromine as a carbon source comprises the following steps: The windproof and p-phenylenediamine are dissolved in a mixed solvent of ethanol and hydrochloric acid, stirred evenly, and transferred to a reactor for a solvothermal reaction; after the solvothermal reaction is completed, the reaction product is cooled to room temperature, taken out and separated by column chromatography to obtain multicolor fluorescent carbon dots.

[0007] Furthermore, the mass ratio of windproof and p-phenylenediamine is (0.24-0.66):0.33, preferably (0.33-0.42):0.33.

[0008] Furthermore, the windproof is in the form of windproof sheets or powder.

[0009] Furthermore, the volume ratio of ethanol to hydrochloric acid in the mixed solvent is 9:(0.5-2).

[0010] Furthermore, the mass volume ratio of the sum of the mass of windproof and p-phenylenediamine to the mass volume ratio of the mixed solvent of ethanol and hydrochloric acid is (0.57-0.99) g: (9.5-11) ml.

[0011] Furthermore, the temperature of the solvent thermal reaction is 160-220° C., and the reaction time is 8-12 hours.

[0012] Furthermore, the polarity of the eluent used in the column chromatography method is small at first and then large, and changes with the separation of the carbon dots. Preferably, petroleum ether, ethyl acetate, acetone, and ethanol are used as eluents in sequence for separation by column chromatography.

[0013] The present invention also provides multicolor fluorescent carbon dots prepared by the above method.

[0014] The carbon dots prepared by the present invention have a variety of fluorescent colors. The fluorescent carbon dots with a luminescent peak at 430-750nm can be separated by column chromatography, covering the visible light region, including blue, light blue, green, yellow, and red fluorescence. The multicolor fluorescent carbon dots are in liquid state and have a relatively stable emission wavelength. Under the excitation of 250-700nm excitation wavelength, the emission peak does not substantially redshift or blueshift with the increase of the excitation wavelength, and it can be dissolved in most solvents such as petroleum ether, ethyl acetate, butyl acetate, ethanol, toluene, etc.

[0015] The beneficial effects of the present invention are: The present invention uses a new biomass material, windproof, as a carbon source, p-diphenylamine as a nitrogen source, ethanol and hydrochloric acid as solvents, and synthesizes multicolor fluorescent carbon dots through a one-pot method. The method has low raw material cost and a simple preparation process. All carbon dots covering the visible light region can be synthesized at one time, which saves a lot of time in changing the fluorescent color through various controls while saving costs. The obtained multicolor fluorescent carbon dots are extremely stable and have no excitation dependence. The emission spectrum covers the entire visible light region. Only by column chromatography, different fluorescent colors can be completely separated. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Normalized emission spectra of the multicolor fluorescent carbon dot solution prepared in Example 1 at different excitation wavelengths (the excitation wavelengths from left to right are 380 nm, 380 nm, 450 nm, 463 nm, 513 nm, and 620 nm, respectively).

[0017] Figure 2Actual pictures of the blue, green, yellow and red fluorescent carbon dots separated from the multicolor fluorescent carbon dots prepared in Example 1 under typical daylight (Figure a) and under excitation of a flashlight with different excitation levels (Figure b), from left to right are blue, green, yellow and red fluorescent carbon dots.

[0018] Figure 3 The stability test results of the blue, green, yellow and red fluorescent carbon dots separated from the multicolor fluorescent carbon dots prepared in Example 1 under continuous irradiation with an external light source for 12 hours are shown in Figures (a), (b), (c) and (d) are emission spectrum change diagrams of the blue, green, yellow and red fluorescent carbon dots under different irradiation times (irradiation time t is 0, 1.5, 3, 4.5, 6, 7.5, 9, 10.5 and 12 hours respectively); Figures (e), (f), (g) and (h) are emission intensity change diagrams of the blue, green, yellow and red fluorescent carbon dots respectively.

[0019] Figure 4 Emission spectra of blue (Figure a), green (Figure b), yellow (Figure c), and red (Figure d) fluorescent carbon dots separated from the multicolor fluorescent carbon dots prepared in Example 1 under different excitations.

[0020] Figure 5 This is the XPS overall spectrum of the blue, green, yellow and red fluorescent carbon dots separated from the multicolor fluorescent carbon dots prepared in Example 1.

[0021] Figure 6 This is a Fourier infrared spectrum of the blue, green, yellow and red fluorescent carbon dots separated from the multi-color fluorescent carbon dots prepared in Example 1.

[0022] Figure 7 This is a fluorescence lifetime fitting diagram of the blue (Figure a), green (Figure b), yellow (Figure c), and red (Figure d) fluorescent carbon dots separated from the multicolor fluorescent carbon dots prepared in Example 1.

[0023] Figure 8 The emission spectra of multicolor fluorescent carbon dots prepared under different feed ratios under 380nm wavelength ultraviolet light excitation. DETAILED DESCRIPTION

[0024] The following will be combined with embodiments to clearly and completely describe the technical solution of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Embodiments, and all other embodiments obtained by ordinary technicians in this field without making creative work, are within the scope of protection of the present invention.

[0025] Example 1 Weigh 0.33g of windproof and 0.33g of p-phenylenediamine and add them to 9mL of ethanol and 0.5-2mL of hydrochloric acid, and stir for 15min. Transfer the mixed solution to a polytetrafluoroethylene reactor, seal it with a lid, and put it in a drying oven. The reaction temperature is 160-220℃ and the reaction time is 8-12h. After the reaction product is cooled to room temperature, take it out to obtain a black turbid solution, and test its fluorescence intensity under 380nm wavelength ultraviolet light excitation. Petroleum ether, ethyl acetate, acetone, and ethanol are used as eluents in turn, and the solution is separated by column chromatography. The separated solution is evaporated to dryness and then redissolved in acetone for further characterization.

[0026] The emission spectrum of the multicolor fluorescent carbon dot solution was tested using a fluorescence spectrophotometer (F-7000, Hitachi). Figure 1 As shown, it can be seen that the multicolor fluorescent carbon dot solution can separate fluorescent carbon dots with luminescence peaks at 430-750nm, covering the entire visible light region, including blue, light blue, green, yellow, and red fluorescence.

[0027] Four typical carbon dots with different fluorescent colors, blue, green, yellow, and red, were selected for further emission spectrum testing as follows.

[0028] like Figure 2 Shown are physical images of blue, green, yellow and red fluorescent carbon dots separated from the multicolor fluorescent carbon dots prepared in this example under typical sunlight and under excitation by a flashlight at different excitation levels.

[0029] Stability test: The carbon dot solutions with different fluorescent colors were placed under external light sources (with their respective optimal excitation wavelengths) for continuous irradiation for 12 hours. Figure 3 and Figure 4 As shown, it can be seen that the luminescence peak position and fluorescence intensity of these carbon dots are well stable, and the fluorescence peak exhibits excitation-independent emission characteristics.

[0030] Elemental composition: In order to explore the elemental composition of these carbon dots in more detail, XPS tests were performed on the material, such as Figure 5 As shown, it can be seen that these carbon dots mainly contain three elements: C, N, and O.

[0031] Functional group information: In order to explore the functional group information of these carbon dots, the material was tested by Fourier transform infrared spectroscopy, such as Figure 6 As shown, it can be seen that there are a large number of functional groups such as C=C, C=O, and CO bonds in these carbon dots, proving that their surface states are extremely rich.

[0032] Fluorescence lifetime test: Figure 7 As shown, these carbon dots have a fluorescence lifetime of nanoseconds and do not have phosphorescence or afterglow.

[0033] Example 2 Weigh 0.42g of fennel and 0.33g of p-phenylenediamine and add them to 9mL of ethanol and 1mL of hydrochloric acid, and stir for 15min. Transfer the mixed solution to a polytetrafluoroethylene reactor, seal it with a lid, and put it in a drying oven. The reaction temperature is 200℃ and the reaction time is 12h. After the reaction product is cooled to room temperature, take it out to obtain a black turbid solution, and test its fluorescence intensity under 380nm wavelength ultraviolet light excitation.

[0034] Example 3 Weigh 0.60g of fennel and 0.33g of p-phenylenediamine and add them to 9mL of ethanol and 1mL of hydrochloric acid, and stir for 15min. Transfer the mixed solution to a polytetrafluoroethylene reactor, seal it with a lid, and put it in a drying oven. The reaction temperature is 200℃ and the reaction time is 12h. After the reaction product is cooled to room temperature, take it out to obtain a black turbid solution, and test its fluorescence intensity under 380nm wavelength ultraviolet light excitation.

[0035] Example 4 Weigh 0.18g of fennel and 0.33g of p-phenylenediamine and add them to 9mL of ethanol and 1mL of hydrochloric acid, and stir for 15min. Transfer the mixed solution to a polytetrafluoroethylene reactor, seal it with a lid, and put it in a drying oven. The reaction temperature is 200℃ and the reaction time is 12h. After the reaction product is cooled to room temperature, take it out to obtain a black turbid solution, and test its fluorescence intensity under 380nm wavelength ultraviolet light excitation.

[0036] Example 5 Weigh 0.12g of fennel and 0.33g of p-phenylenediamine and add them to 9mL of ethanol and 1mL of hydrochloric acid, and stir for 15min. Transfer the mixed solution to a polytetrafluoroethylene reactor, seal it with a lid, and put it in a drying oven. The reaction temperature is 200℃ and the reaction time is 12h. After the reaction product is cooled to room temperature, take it out to obtain a black turbid solution, and test its fluorescence intensity under 380nm wavelength ultraviolet light excitation.

[0037] Example 6 Weigh 0.06g of fennel and 0.33g of p-phenylenediamine and add them to 9mL of ethanol and 1mL of hydrochloric acid, and stir for 15min. Transfer the mixed solution to a polytetrafluoroethylene reactor, seal it with a lid, and put it in a drying oven. The reaction temperature is 200℃ and the reaction time is 12h. After the reaction product is cooled to room temperature, take it out to obtain a black turbid solution, and test its fluorescence intensity under 380nm wavelength ultraviolet light excitation.

[0038] Example 7 Weigh 0.24g of fennel and 0.33g of p-phenylenediamine and add them to 9mL of ethanol and 1mL of hydrochloric acid, and stir for 15min. Transfer the mixed solution to a polytetrafluoroethylene reactor, seal it with a lid, and put it in a drying oven. The reaction temperature is 200℃ and the reaction time is 12h. After the reaction product is cooled to room temperature, take it out to obtain a black turbid solution, and test its fluorescence intensity under 380nm wavelength ultraviolet light excitation.

[0039] Example 8 Weigh 0.66g of windproof and 0.33g of p-phenylenediamine and add them to 9mL of ethanol and 1mL of hydrochloric acid, and stir for 15min. Transfer the mixed solution to a polytetrafluoroethylene reactor, seal it with a lid, and put it in a drying oven. The reaction temperature is 200℃ and the reaction time is 12h. After the reaction product is cooled to room temperature, take it out to obtain a black turbid solution, and test its fluorescence intensity under 380nm wavelength ultraviolet light excitation.

[0040] like Figure 8 The emission spectra of the multicolor fluorescent carbon dots prepared under different feed ratios under 380nm wavelength ultraviolet light excitation are shown in Examples 1 to 8. It can be seen that when the mass ratio of windproof and p-phenylenediamine is (0.33-0.66):0.33, the fluorescence intensity of the prepared multicolor fluorescent carbon dots is relatively strong.

Claims

1. A method for synthesizing multicolor fluorescent carbon dots in one pot using windproof as a carbon source, characterized in that: The following steps are involved: The windproof and p-phenylenediamine are dissolved in a mixed solvent of ethanol and hydrochloric acid, stirred evenly, and transferred to a reaction kettle for solvent thermal reaction; after the reaction product is cooled to room temperature, it is taken out and separated by column chromatography to obtain multicolor fluorescent carbon dots.

2. The method for synthesizing multicolor fluorescent carbon dots in one pot using windproof as a carbon source according to claim 1, characterized in that: The mass ratio of the windproof and p-phenylenediamine is (0.24-0.66):0.

33.

3. The method for synthesizing multicolor fluorescent carbon dots in one pot using windproof as a carbon source according to claim 1, characterized in that: The volume ratio of ethanol to hydrochloric acid in the mixed solvent is 9:(0.5-2).

4. The method for synthesizing multicolor fluorescent carbon dots in one pot using windproof as a carbon source according to claim 1, characterized in that: The mass volume ratio of the sum of the mass of the windproof and p-phenylenediamine to the mass volume ratio of the mixed solvent of ethanol and hydrochloric acid is (0.57-0.99) g: (9.5-11) ml.

5. The method for synthesizing multicolor fluorescent carbon dots in one pot using windproof as a carbon source according to claim 1, characterized in that: The temperature of the solvent thermal reaction is 160-220° C., and the reaction time is 8-12 hours.

6. The method for synthesizing multicolor fluorescent carbon dots in one pot using windproof as a carbon source according to claim 1, characterized in that: The eluents used in the column chromatography method are petroleum ether, ethyl acetate, acetone and ethanol in sequence.

7. Multicolor fluorescent carbon dots prepared by the method according to any one of claims 1 to 6.

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