CN109095453B - Preparation method of tea-based fluorescent carbon dots and fluorescent carbon dots prepared by preparation method - Google Patents
Preparation method of tea-based fluorescent carbon dots and fluorescent carbon dots prepared by preparation method Download PDFInfo
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Abstract
The invention relates to a preparation method of a tea-based fluorescent carbon dot and a fluorescent carbon dot prepared by the preparation method, and the method comprises the following steps: grinding tea leaves into powder, extracting with absolute ethanol as an extraction solvent, filtering to remove tea residues, and collecting the obtained extract; adding water into the obtained extracting solution, transferring the extracting solution into a reaction kettle for hydrothermal carbonization, and naturally cooling to room temperature; and (3) under the irradiation of an ultraviolet lamp, carrying out column chromatography separation on the obtained product, collecting fluorescent carbon dot solutions with different fluorescent colors, and carrying out rotary evaporation to remove the solvent to obtain the fluorescent carbon dots. Drying and crushing the tea leaves obtained after extraction, then directly carbonizing at high temperature, naturally cooling to room temperature, adding deionized water into the obtained product, then carrying out ultrasonic treatment, microfiltration membrane filtration, centrifugal treatment and dialysis to obtain a fluorescent carbon dot solution, and carrying out freeze drying to obtain the fluorescent carbon dots. The method has the advantages of high yield of all the fluorescent carbon dots, good stability, simplicity, environmental protection, low cost and easy realization of large-scale and industrial production.
Description
Technical Field
The invention relates to a carbon nano material, in particular to a preparation method of a tea-based fluorescent carbon dot and a fluorescent carbon dot prepared by the preparation method.
Background
Fluorescent carbon quantum dots, carbon dots for short, are a new carbon nanomaterial in recent years, and have very important significance in the aspects of cell imaging, biological detection, photocatalytic degradation of organic pollutants, photoelectric energy storage and the like due to excellent low biotoxicity and good luminous performance. Compared with semiconductor quantum dots, the carbon dots are more suitable for the fields of cell imaging and the like, are more diverse in raw material selection, and are beneficial to promoting the development of the carbon dots.
Many carbon sources can be used for preparing the fluorescent carbon dots, and inorganic (various carbon materials) and organic (organic micromolecules, macromolecules and biomass) materials can be used for preparing the fluorescent carbon dots. At present, many reports are reported on the preparation of carbon dots by using biomass materials as carbon sources, but most of the carbon dots emit blue light, and the adopted carbon sources are citrus peels (Chinese patent application No. 201410841970.4); corncobs (chinese patent application No. 201510147558.7); shaddock (chinese patent application No. 201511004717.4), and the like, and there are few reports of carbon dots with various fluorescent colors prepared by using biomass as a carbon source.
The tea contains various components such as tea polyphenol, protein, theanine, alkaloid, tea pigment, tea polysaccharide, cellulose and the like, even tea leaves obtained after extracting effective components are rich in components such as cellulose, protein, polyphenol, organic acid and the like, and the tea leaves are ideal carbon sources for preparing fluorescent carbon dots. Some reports have been made, such as that dried green tea leaves are ground into powder and directly carbonized at 300 ℃ for 2 hours to obtain fluorescent carbon dots [ Journal of Materials Chemistry B,2013,1,1774-1781 ]; xi and the like take black tea leaves and water as reactants, and prepare a fluorescent carbon point [ RSC Advances,2017,7, 28637-one 28646] through a hydrothermal reaction for 5 hours at 200 ℃; the tea leaves and the like directly adopt the Tieguanyin green tea leaves as a carbon source and prepare fluorescent carbon dots through microwave hydrothermal reaction (proceedings of the Ningde academy of academic, 2017, 29, 356-plus 360), but the prepared carbon dots are single blue fluorescent carbon dots, a solvent used in the hydrothermal method is single water, the participation of other effective components in the tea leaves is not facilitated, and the systematic research on the preparation of the carbon dots by adopting the tea leaves and the tea leaves is lacked.
Disclosure of Invention
The invention aims to provide a preparation method of tea-based fluorescent carbon dots and the prepared fluorescent carbon dots, which can prepare fluorescent carbon dot solutions with different fluorescent colors from extracts of tea leaves, and the preparation method is simple, environment-friendly, low in cost and easy to realize large-scale and industrial production.
In order to achieve the above object, the present invention provides a method for preparing a tea-based fluorescent carbon dot, comprising the steps of:
(1) grinding tea leaves into powder, taking absolute ethyl alcohol as an extraction solvent, filtering to remove tea leaves after extraction, and collecting the obtained extracting solution;
(2) adding water into the extracting solution obtained in the step (1), transferring the extracting solution into a reaction kettle, performing hydrothermal carbonization, and naturally cooling to room temperature;
(3) and (3) under the irradiation of an ultraviolet lamp, performing column chromatography separation on the product obtained in the step (2), collecting fluorescent carbon dot solutions with different fluorescent colors, and performing rotary evaporation to remove the solvent to obtain the fluorescent carbon dots.
In the step (1), the extraction temperature of tea extraction is 20-80 ℃, the extraction time is not less than 1h, and the solid-to-liquid ratio is 1g: 20-50 mL.
In the step (2), the volume ratio of the extracting solution to water is 1: 0-1, the temperature of hydrothermal carbonization is 120-180 ℃, and the time is 2-8 h.
In the step (3), the stationary phase of the column chromatography is 200-300 mesh silica gel, the mobile phase is determined by thin-layer chromatography, and the fluorescent carbon dot solutions with different fluorescent colors at least comprise red, yellow and blue.
The preparation method of the tea-based fluorescent carbon dots further comprises the following steps:
(4) drying, crushing and directly carbonizing the tea leaves obtained in the step (1) at high temperature in sequence, and naturally cooling to room temperature;
(5) and (4) adding deionized water into the product obtained in the step (4), sequentially carrying out ultrasonic treatment, microporous membrane filtration, centrifugal treatment and dialysis to obtain a fluorescent carbon dot solution, and carrying out freeze drying to obtain the fluorescent carbon dots.
The high-temperature direct carbonization in the step (4) is carried out in a high-temperature furnace, the treatment temperature is 150-300 ℃, and the reaction time is 2-15 h.
In the step (5), the ultrasonic power is 500W, and the ultrasonic time is 10-120 min; the aperture of the microporous filter membrane is 0.22 mu m; the centrifugation speed is 1000-10000rpm, and the centrifugation time is 5-60 min; a dialysis bag of 1000-3500Da is adopted for dialysis, and the dialysis time is 6-36 h; the freeze-drying temperature was-50 ℃.
The tea adopted in the preparation method of the tea-based fluorescent carbon dots is green tea, black tea or black tea and the like.
In order to achieve the purpose, the invention also provides a fluorescent carbon dot prepared by the preparation method of the tea-based fluorescent carbon dot.
The method is based on tea leaves, absolute ethyl alcohol is used as an extracting agent, fluorescent carbon dot solutions with various fluorescent colors such as red, yellow and blue are prepared from an extracting solution of the tea leaves through simple hydrothermal carbonization, blue light carbon dots are also prepared from tea residues obtained after extraction through direct high-temperature carbonization, the preparation method is simple, green and environment-friendly, the cost is low, large-scale and industrial production of the carbon dots is easy to realize, and all the obtained fluorescent carbon dots are high in yield and good in stability. The grain size of the prepared red carbon dots is small and is about 2.6 nm.
Drawings
FIG. 1 is a transmission electron micrograph (20 nm on scale) of red light carbon dots prepared from tea extract according to the present invention.
FIG. 2 is a graph of the UV-Vis spectrum, the optimal excitation and the optimal emission fluorescence spectrum of the red carbon quantum dots prepared by the tea extract of the present invention.
FIG. 3 is a graph showing the fluorescence spectra of carbon dots of different fluorescence colors at 360nm prepared from tea extract according to the present invention (1 is blue light, 2 is green light, 3 is orange light, and 4 is red light).
FIG. 4 is a UV-VIS spectrum, an optimal excitation and an optimal emission fluorescence spectrum of blue light carbon dots prepared from the extracted tea leaves of the present invention.
Detailed Description
The present invention will be further described with reference to the following examples.
Example 1
Weighing 2g of powdered green tea leaves, adding 50mL of absolute ethyl alcohol, sealing and soaking at room temperature for 12h, filtering to remove tea residues, putting 8mL of extracting solution and 2mL of deionized water in a 25mL reaction kettle, heating at 160 ℃ for 3h, cooling to room temperature, transferring the solution into a filled silica gel column, performing column chromatography under the irradiation of an ultraviolet lamp by using petroleum ether and ethyl acetate as eluents, respectively collecting fluorescent carbon dot solutions with different fluorescent colors, and performing rotary evaporation to remove the solvent to obtain the fluorescent carbon dots. Taking 1g of the dried tea residue obtained after extraction, putting the dried tea residue into a porcelain boat, heating the porcelain boat for 5h at 180 ℃, taking out the generated black powder, putting the black powder into a beaker, adding 10mL of ultrapure water for ultrasonic treatment for 30min, filtering the mixture by a 0.22-micron membrane to obtain a reddish brown solution, centrifuging the solution for 5min at 8000rpm, putting the supernatant into a 3500Da dialysis bag for dialysis for 24h to obtain a blue light carbon dot solution, and freeze-drying the blue light carbon dot solution to obtain a fluorescent carbon dot solution.
Example 2
Example 2 differs from example 1 in that 2g of powdered black tea leaves are weighed, 50mL of absolute ethanol is added, reflux extraction is carried out at 80 ℃ for 105min, filter residue is removed while the tea leaves are hot, 9mL of extract and 1mL of deionized water are immediately taken in a 25mL reaction kettle, heating is carried out at 160 ℃ for 3h, cooling is carried out to room temperature, the solution is transferred into a filled silica gel column, column chromatography is carried out under the irradiation of an ultraviolet lamp by taking petroleum ether and ethyl acetate as eluents, fluorescent carbon dot solutions with different fluorescent colors are respectively collected, and the fluorescent carbon dots are obtained after solvents are removed by rotary evaporation. Taking 1g of the dried tea residue obtained after extraction, putting the dried tea residue into a porcelain boat, heating the porcelain boat for 6h at 160 ℃, taking out the generated black powder, putting the black powder into a beaker, adding 10mL of ultrapure water for ultrasonic treatment for 20min, filtering the mixture by a 0.22-micron membrane to obtain a reddish brown solution, centrifuging the solution at 9000rpm for 5min, taking the supernatant, putting the supernatant into a 3500Da dialysis bag for dialysis for 24h to obtain a blue light carbon dot solution, and freeze-drying the blue light carbon dot solution to obtain a fluorescent carbon dot solution.
Example 3
Example 3 differs from example 1 in that 2g of powdered black tea leaves are weighed, 50mL of absolute ethanol is added, reflux extraction is carried out for 120min at 80 ℃, filter residue is removed while the tea leaves are hot, 10mL of extract is immediately taken out and put into a 25mL reaction kettle, heating is carried out for 6h at 180 ℃, cooling is carried out to room temperature, the solution is transferred into a filled silica gel column, column chromatography is carried out under the irradiation of an ultraviolet lamp by using petroleum ether and ethyl acetate as eluents, fluorescent carbon dot solutions with different fluorescent colors are respectively collected, and the fluorescent carbon dots are obtained after the solvent is removed by rotary evaporation. Taking 1g of the dried tea residue obtained after extraction, putting the dried tea residue into a porcelain boat, heating the porcelain boat for 8h at 180 ℃, taking out the generated black powder, putting the black powder into a beaker, adding 20mL of ultrapure water for ultrasonic treatment for 30min, filtering the mixture by a 0.22-micron membrane to obtain a reddish brown solution, centrifuging the solution at 6000rpm for 5min, taking the supernatant, putting the supernatant into a 3500Da dialysis bag for dialysis for 24h to obtain a blue light carbon dot solution, and freeze-drying the blue light carbon dot solution to obtain a fluorescent carbon dot solution.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (9)
1. A preparation method of a tea-based fluorescent carbon dot is characterized by comprising the following steps:
(1) grinding tea leaves into powder, taking absolute ethyl alcohol as an extraction solvent, filtering to remove tea leaves after extraction, and collecting the obtained extracting solution;
(2) adding water into the extracting solution obtained in the step (1), transferring the extracting solution into a reaction kettle, performing hydrothermal carbonization, and naturally cooling to room temperature;
(3) and (3) under the irradiation of an ultraviolet lamp, performing column chromatography separation on the product obtained in the step (2), collecting fluorescent carbon dot solutions with different fluorescent colors, and performing rotary evaporation to remove the solvent to obtain the fluorescent carbon dots.
2. The preparation method of the tea-based fluorescent carbon dots according to claim 1, wherein the tea extraction temperature in the step (1) is 20-80 ℃, the extraction time is not less than 1h, and the solid-to-liquid ratio is 1g: 20-50 mL.
3. The preparation method of tea-based fluorescent carbon dots according to claim 1, wherein the volume ratio of the extracting solution to water in the step (2) is 1: 0-1, the temperature of the hydrothermal carbonization is 120-180 ℃, and the time is 2-8 h.
4. The preparation method of tea-based fluorescent carbon dots according to claim 1, wherein the stationary phase of the column chromatography in the step (3) is 200-300 mesh silica gel, the mobile phase is determined by thin layer chromatography, and the fluorescent carbon dot solutions with different fluorescent colors at least comprise red, yellow and blue.
5. The method for preparing a tea-based fluorescent carbon dot as set forth in claim 1, further comprising:
(4) drying, crushing and directly carbonizing the tea leaves obtained in the step (1) at high temperature in sequence, and naturally cooling to room temperature;
(5) and (4) adding deionized water into the product obtained in the step (4), sequentially carrying out ultrasonic treatment, microporous membrane filtration, centrifugal treatment and dialysis to obtain a fluorescent carbon dot solution, and carrying out freeze drying to obtain the fluorescent carbon dots.
6. The method for preparing a fluorescent carbon dot based on tea as claimed in claim 5, wherein the high temperature direct carbonization in the step (4) is performed in a high temperature furnace at a treatment temperature of 150 ℃ to 300 ℃ for a reaction time of 2-15 h.
7. The preparation method of tea-based fluorescent carbon dots according to claim 5, wherein the ultrasonic power in the step (5) is 500W, and the ultrasonic time is 10-120 min; the aperture of the microporous filter membrane is 0.22 mu m; the centrifugation speed is 1000-10000rpm, and the centrifugation time is 5-60 min; a dialysis bag of 1000-3500Da is adopted for dialysis, and the dialysis time is 6-36 h; the freeze-drying temperature was-50 ℃.
8. The method for preparing tea-based fluorescent carbon dots according to claim 1, wherein the tea leaves are green tea, black tea or dark tea.
9. The fluorescent carbon dot manufactured by the tea-based fluorescent carbon dot manufacturing method according to any one of claims 1 to 8.
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| CN109593525A (en) * | 2019-01-04 | 2019-04-09 | 浙江工业大学 | It is a kind of using Longjing tea as carbon quantum dot of carbon source and its preparation method and application |
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| CN109913211A (en) * | 2019-04-08 | 2019-06-21 | 东北林业大学 | Carbon quantum dot and preparation method thereof, membrane material of carbon containing quantum dot and its preparation method and application |
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| CN111773287B (en) * | 2020-06-30 | 2022-03-29 | 湖北大学 | Preparation method and application of tea nanoclusters |
| CN111892036A (en) * | 2020-07-10 | 2020-11-06 | 山西大学 | Method for preparing carbon quantum dots by using waste green tea residues and application thereof |
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| CN113390840A (en) * | 2021-06-12 | 2021-09-14 | 宁德师范学院 | Method for synthesizing carbon dots and detecting copper ions in water body |
| CN116144355A (en) * | 2023-03-09 | 2023-05-23 | 郑州大学 | Ultra-long-time near-infrared water-soluble afterglow luminous carbon dot and preparation method and application thereof |
| CN116590009B (en) * | 2023-05-30 | 2024-03-01 | 聊城大学 | Composite film capable of being excited by blue light to generate white fluorescence and preparation method and application thereof |
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