Preparation method and application of dual-wavelength fluorescent carbon dots

Abstract

The invention discloses a preparation method and application of dual-wavelength fluorescent carbon dots. The preparation method comprises the following steps: step 1, pretreatment of apple raw materials; step 2, pre-drying treatment; and step 3, differential pressure flash drying coupled infrared pulse jet treatment: putting the material obtained in the step 2 into a closed puffing tank, keeping for 10 minutes at 90 DEG C, then introducing saturated hot steam to increase the pressure in the puffing tank to 0.6 PMa, keeping for 30 seconds, then instantaneously reducing the pressure to reduce the pressure in the puffing tank to 0.003-0.005 MPa, simultaneously performing pulse infrared treatment, and then vacuumizing and drying to obtain the finished product. Opening a vent valve to recover the pressure in the puffing tank to atmospheric pressure, and collecting the obtained material; and 4, separating and purifying the fluorescent carbon dots. The invention solves the problems of high synthesis cost, low safety, complex process and the like of the existing fluorescent carbon dots. The obtained fluorescent carbon dots have dual wavelengths, and the accuracy and sensitivity of the fluorescent carbon dots in chlorogenic acid detection can be improved.

Description

Technical Field

[0001] The present invention relates to the field of food chemistry and more specifically to a preparation method and application of dual-wavelength fluorescent carbon dots. Background Art

[0002] Fluorescent carbon dots are a new type of material discovered in recent years. They usually have the advantages of small size, controllable surface chemistry, good water dispersibility, good biocompatibility, low environmental impact, high fluorescence stability, etc. They are widely used in in vivo and in vitro imaging, drug delivery, and biological detection. At present, there are two main methods for preparing fluorescent carbon dots: "top-down" and "bottom-up".

[0003] The industrial synthesis of fluorescent carbon dots usually has long reaction times, high energy consumption, and involves a variety of chemical reagents. There are many chemical pollution and safety issues, which will limit its application in the food field.

[0004] Food-derived fluorescent carbon dots have begun to attract widespread attention due to their safety and low cost.

[0005] At present, food-derived fluorescent carbon dots are mainly obtained from high-temperature, fried foods, such as roast duck and barbecue. This often involves high preparation temperatures, resulting in low safety in the preparation process and high raw material costs. Therefore, it is very important to invent a simple, cheap and safe method for preparing edible fluorescent carbon dots.

[0006] Chlorogenic acid is an active substance commonly found in fruits and vegetables. Currently, the detection of chlorogenic acid is mainly carried out by ultraviolet colorimetry, liquid chromatography and other methods, which are cumbersome and have low accuracy. Therefore, it is necessary to develop fluorescent carbon dots with high sensitivity to chlorogenic acid. Summary of the invention

[0007] The purpose of the present invention is to provide a preparation method and application of dual-wavelength fluorescent carbon dots, which solves the problems of high synthesis cost, low safety, and complex process of fluorescent carbon dots. At the same time, the obtained fluorescent carbon dots have dual wavelengths, which can improve their accuracy and sensitivity in chlorogenic acid detection.

[0008] In order to achieve these objects and other advantages of the present invention, a method for preparing dual-wavelength fluorescent carbon dots is provided, comprising the following steps: Step 1: Pre-treatment of apple raw materials: wash, peel and cut the raw materials into slices; Step 2: Pre-drying: pre-dry the material obtained in step 1; Step 3, differential pressure flash drying coupled with infrared pulse jet treatment: the material obtained in step 2 is placed in a sealed puffing tank, maintained at 80-110°C for 5-15 minutes, then saturated hot steam is introduced to raise the pressure in the puffing tank to 0.6 PMa, maintained for 30 seconds, then the pressure in the puffing tank is reduced to 0.003-0.005 MPa, and pulse infrared treatment is performed at the same time, and then vacuum drying is performed to rapidly puff and dry the apple material, and uniform and high-density fluorescent carbon dots are generated inside the material, and then the vent valve is opened to restore the pressure in the puffing tank to atmospheric pressure, and the obtained material is collected; Step 4: Separation and purification of fluorescent carbon dots: Separate and purify the material obtained in step 3.

[0009] Preferably, in the method for preparing the dual-wavelength fluorescent carbon dots, in the step 1, the raw material is cut into sheets of 5-8 mm.

[0010] Preferably, in the method for preparing dual-wavelength fluorescent carbon dots, in the step 2, the material obtained in the step 1 is placed in an oven and pre-dried at 80-100° C. for 1-2 hours.

[0011] Preferably, in the method for preparing dual-wavelength fluorescent carbon dots, in step 3, after the pulse infrared treatment, the mixture is dried under vacuum at a temperature of 80-110° C. and a pressure of 0.004 MPa for 10-20 min.

[0012] Preferably, in the method for preparing dual-wavelength fluorescent carbon dots, in step three, the pulse infrared treatment is performed for 25 seconds, and the pulse interval is 5 seconds.

[0013] Preferably, in the preparation method of the dual-wavelength fluorescent carbon dots, in the step 4, the specific steps of separating and purifying the fluorescent carbon dots are: adding an ethanol solution with a volume ratio of 10-50% to the material obtained in step 3 to fully dissolve it, then extracting it in a 50°C water bath for 1 h, followed by centrifugation to obtain a supernatant; passing the obtained supernatant through a dialysis bag with a molecular weight cutoff of 1000Da, and dialyzing it for 3 days to obtain a purified fluorescent carbon dot solution; vacuum freeze-drying the purified fluorescent carbon dot solution to obtain a solid powder of the fluorescent carbon dots.

[0014] The method for detecting the concentration of chlorogenic acid using dual-wavelength fluorescent carbon dots comprises the following steps: Step 1), dispersing the solid powder of fluorescent carbon dots in a solvent to prepare a fluorescent carbon dot solution; Step 2), preparing equal volumes of chlorogenic acid solutions of different concentrations, adding equal volumes of the fluorescent carbon dot solutions respectively, mixing and reacting, and obtaining a series of mixed solutions of equal volumes of chlorogenic acid of different concentrations, respectively detecting the fluorescence intensity thereof, and calculating the linear relationship between the ratio F0 / F of the strongest fluorescence intensity F between 400-500 nm and the strongest fluorescence intensity F between 700-800 nm and the chlorogenic acid concentration; Step 3), after adding the fluorescent carbon dot solution to the sample to be tested, mixing and reacting, a mixed solution of the sample to be tested is obtained, and then the fluorescence intensity of the mixed solution of the sample to be tested is detected; Step 4), according to the linear relationship between the ratio of fluorescence intensity F0 / F obtained in step 2) and the concentration of chlorogenic acid, the concentration of chlorogenic acid in the mixed solution of the sample to be tested is obtained; Among them, the concentration of chlorogenic acid solution is 0-1 μg / L; the fluorescence intensity detection parameters are: at an excitation wavelength of 370nm, collect the spectrum with an emission wavelength of 400-800 nm, the excitation and emission slits are 2.5 nm, and the excitation voltage is 700V.

[0015] Preferably, in the method for detecting the concentration of chlorogenic acid using dual-wavelength fluorescent carbon dots, the step 1) is specifically: Preferably, in the method of detecting the concentration of chlorogenic acid using dual-wavelength fluorescent carbon dots, the linear relationship between the fluorescence intensity ratio F0 / F and the concentration of chlorogenic acid is: Y=-0.4457X+1.0147R 2 =0.9708; The linear range of detection was 0-1 μg / L.

[0016] Preferably, in the method for detecting the concentration of chlorogenic acid using dual-wavelength fluorescent carbon dots, the step 1) is specifically: dispersing the solid powder of the fluorescent carbon dots in water and / or ethanol to prepare a fluorescent carbon dot solution with a concentration of 5 mg / mL.

[0017] Preferably, in the method for detecting the concentration of chlorogenic acid using dual-wavelength fluorescent carbon dots, in the step 2), when mixed, the volume ratio of the chlorogenic acid solution to the fluorescent carbon dot solution is 1:3, and in the step 3), the volume ratio of the sample to be tested and the fluorescent carbon dot solution when mixed is 1:3.

[0018] The present invention has at least the following beneficial effects: The present invention uses popular fruits such as apples as raw materials, which are widely available and inexpensive, and no other chemical reagents are added during the preparation process. The prepared fluorescent carbon dots have the advantages of edibility and high safety. At the same time, the obtained fluorescent carbon dots have dual wavelengths, which can improve the accuracy and sensitivity of chlorogenic acid detection.

[0019] The present invention adopts the pressure difference flash evaporation technology, has low preparation time cost, and is suitable for large-scale preparation of fluorescent materials.

[0020] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The ultraviolet spectrum of the fluorescent carbon dots prepared in Example 1 of the present invention; Figure 2 The fluorescence spectrum of the fluorescent carbon dot solution prepared in Example 1 of the present invention and the fluorescence excitation images under sunlight and ultraviolet light (365nm); Figure 3 The fluorescence emission spectra of the fluorescent carbon dots prepared in Example 1 of the present invention to chlorogenic acid solutions of different concentrations at an excitation wavelength of 370 nm, wherein the fluorescence emission lines correspond to 0-1 μg / L from top to bottom, respectively; Figure 4 This is a linear relationship diagram of the fluorescence intensity of the fluorescent carbon dots prepared in Example 1 of the present invention and the chlorogenic acid concentration at different concentrations of chlorogenic acid at an emission wavelength of 750 nm. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0023] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0024] The present invention provides a method for preparing dual-wavelength fluorescent carbon dots, comprising the following steps: Step 1: Pre-treatment of apple raw materials: wash, peel and cut the raw materials into slices; Step 2: Pre-drying: pre-dry the material obtained in step 1; Step three, differential pressure flash drying coupled with infrared pulse jet treatment: through the four-stage differential pressure flash treatment of "heating and pressure increase - instantaneous pressure reduction - pulse infrared - vacuum drying - pressure recovery". The material obtained in step two is placed in a closed puffing tank and maintained at 80-110°C for 5-15 min to ensure that the sample temperature is consistent. Then, saturated hot steam is introduced to raise the pressure in the puffing tank to 0.6 PMa and maintained for 30 s. Then, the instantaneous switch valve is automatically opened to cause an instantaneous pressure drop, so that the pressure in the puffing tank is instantly reduced to 0.003-0.005 MPa within tens of milliseconds. At the same time, pulse infrared treatment is carried out, and then vacuum drying is carried out to quickly puff and dry the apple material, and uniform and high-density fluorescent carbon dots are generated inside the material. Then, the vent valve is opened to restore the pressure in the puffing tank to atmospheric pressure, and the obtained material is collected; Step 4: Separation and purification of fluorescent carbon dots: Separate and purify the material obtained in step 3.

[0025] The present invention uses differential pressure flash evaporation to treat the raw materials to produce fluorescent carbon dots. The differential pressure flash evaporation technology used in the present invention includes four stages: "heating and pressurization - instantaneous pressure reduction - vacuum drying - pressure recovery". In the heating and pressurization stage, the material placed in the tray on the pipe is heated and pressurized (about 0.6 MPa, about 30 seconds) by using a metal pipe with hot steam inside the material bin. In the instantaneous pressure reduction stage, within tens of milliseconds, the pressure in the puffing tank is reduced from 0.6 MPa to about 0.003-0.005 MPa. The huge pressure difference in the process, the impact force, shear force, etc. generated are conducive to the hydrolysis of macromolecular substances such as polysaccharides, proteins, peptides, etc. in fruits, and provide more free small molecule substrates for the subsequent chemical reaction of producing fluorescent substances. The present invention uses differential pressure flash evaporation technology, which greatly improves the preparation efficiency of fluorescent substances and effectively reduces the preparation cost.

[0026] In the process of preparing fluorescent carbon dots, pulse infrared is coupled, and the pulse interval is 5s, which greatly improves the preparation efficiency and uniformity, can reduce energy consumption by 6%, and shorten the drying time by 8%.

[0027] The present invention adopts apple, a food-grade raw material, to prepare fluorescent carbon dots, which effectively improves the safety in the preparation of fluorescent carbon dots and expands the application range thereof.

[0028] The fluorescent carbon dots obtained by the present invention have dual-wavelength (450nm and 750nm) responses to chlorogenic acid and can be used for chlorogenic acid content detection.

[0029] In the method for preparing dual-wavelength fluorescent carbon dots, in step 1, the raw material is cut into sheets of 5-8 mm.

[0030] In the preparation method of dual-wavelength fluorescent carbon dots, in the step 2, the material obtained in the step 1 is placed in an oven and pre-dried at 80-100° C. for 1-2 hours.

[0031] In the preparation method of dual-wavelength fluorescent carbon dots, in step three, after the pulse infrared treatment, the mixture is dried under vacuum for 10-20 minutes at a temperature of 80-110° C. and a pressure of 0.004 MPa.

[0032] In the method for preparing dual-wavelength fluorescent carbon dots, in step three, the pulse infrared treatment is performed for 25 seconds, and the pulse interval is 5 seconds.

[0033] In the preparation method of dual-wavelength fluorescent carbon dots, in step 4, the specific steps of separating and purifying the fluorescent carbon dots are as follows: adding the extraction solvent of the fluorescent carbon dots: 10-50% (v / v) ethanol solution to the material obtained in step 3, fully dissolving it, then extracting it in a 50°C water bath for 1 h, and then centrifuging it to obtain a supernatant; purifying and separating the obtained supernatant, passing it through a dialysis bag with a molecular weight cutoff of 1000Da, and dialyzing it for 3 days to obtain a purified fluorescent carbon dot solution; vacuum freeze-drying the purified fluorescent carbon dot solution to obtain a solid powder of the fluorescent carbon dots.

[0034] The method for detecting the concentration of chlorogenic acid using dual-wavelength fluorescent carbon dots comprises the following steps: Step 1), dispersing the solid powder of fluorescent carbon dots in a solvent to prepare a fluorescent carbon dot solution; Step 2), prepare equal volumes of chlorogenic acid solutions of different concentrations, add equal volumes of fluorescent carbon dot solutions respectively, mix and react, obtain a series of equal volumes of mixed solutions of chlorogenic acid of different concentrations, detect the fluorescence intensity of each solution, and calculate the linear relationship between the ratio F0 / F of the strongest fluorescence intensity F between 400-500 nm and the strongest fluorescence intensity F between 700-800 nm and the chlorogenic acid concentration; Step 3), after adding the fluorescent carbon dot solution to the sample to be tested, mixing and reacting, a mixed solution of the sample to be tested is obtained, and then the fluorescence intensity of the mixed solution of the sample to be tested is detected, and the ratio F0 / F of the strongest fluorescence intensity F0 between 400-500 nm and the strongest fluorescence intensity F between 700-800 nm is calculated; Step 4), according to the linear relationship between the ratio of fluorescence intensity F0 / F obtained in step 2) and the concentration of chlorogenic acid, the concentration of chlorogenic acid in the mixed solution of the sample to be tested is obtained; Among them, the concentration of chlorogenic acid solution is 0-1 μg / L; the fluorescence intensity detection parameters are: at an excitation wavelength of 370nm, collect the spectrum with an emission wavelength of 400-800 nm, the excitation and emission slits are 2.5 nm, and the excitation voltage is 700V.

[0035] In the method of detecting the concentration of chlorogenic acid using dual-wavelength fluorescent carbon dots, the linear relationship between the fluorescence intensity ratio F0 / F and the concentration of chlorogenic acid is: Y=-0.4457X+1.0147R 2 =0.9708; The linear range of detection was 0-1 μg / L.

[0036] In the method for detecting the concentration of chlorogenic acid using dual-wavelength fluorescent carbon dots, the step 1) is specifically: dispersing the solid powder of the fluorescent carbon dots in water and / or ethanol to prepare a fluorescent carbon dot solution with a concentration of 5 mg / mL.

[0037] In the method for detecting the concentration of chlorogenic acid using dual-wavelength fluorescent carbon dots, in the step 2), when mixed, the volume ratio of the chlorogenic acid solution to the fluorescent carbon dot solution is 1:3, and in the step 3), the volume ratio of the sample to be tested and the fluorescent carbon dot solution when mixed is 1:3.

[0038] Example 1 (1) Raw material pretreatment: Wash, peel and cut the apples into 5 mm slices.

[0039] (2) Pre-drying: The material obtained in step (1) was placed in an oven for pre-drying at 90°C for 1.5 h.

[0040] (3) Pressure differential flash drying treatment: The material obtained in step (2) is placed in a sealed expansion tank and maintained at 90°C for 10 minutes to ensure that the sample temperature is consistent. Saturated hot steam is introduced to raise the pressure in the tank to 0.6 PMa and maintained for 30 seconds. The instantaneous switch valve is automatically opened to instantly reduce the pressure, so that the pressure in the expansion tank is instantly reduced to 0.003-0.005MPa within tens of milliseconds. This is one pressure differential flash process. At the same time, pulse infrared treatment is carried out for 25 seconds with a pulse interval of 5 seconds. After vacuum drying at 90°C and a pressure of 0.004 MPa for 20 minutes, the air release valve is opened to restore the pressure in the expansion tank to atmospheric pressure, and the obtained material is collected.

[0041] (4) Isolation and purification of fluorescent carbon dots: Take 10 g of the material obtained in step (3), add 100 mL of 10% (v / v) ethanol solution, extract in a 50°C water bath for 1 h, centrifuge to remove insoluble matter, and obtain a supernatant. The supernatant is passed through a dialysis bag with a molecular weight cutoff of 1000 Da, dialyzed for 3 days, and then freeze-dried to obtain a brown solid powder, which is the fluorescent carbon dots. The yield of fluorescent carbon dots is 92.3% and the purity is 90%.

[0042] (5) Preparation of fluorescent carbon dot solution: The fluorescent carbon dot solid powder prepared in step (4) was dissolved in distilled water at a concentration of 1 mg / mL to prepare a fluorescent carbon dot solution.

[0043] like Figure 1 As shown, the characteristic peak between 250-400 nm is the conjugated structure in the molecule. Figure 2 The fluorescence spectrum data of the fluorescent carbon dot solution shows that the carbon dots have dual wavelength characteristics (450nm and 750nm). Figure 3 These are pictures of fluorescent carbon dot solution under fluorescent light and ultraviolet light.

[0044] Comparative Example 1 (1) Raw material pretreatment: Wash, peel and cut the apples into 5 mm slices.

[0045] (2) Pre-drying: The material obtained in step (1) was placed in an oven for pre-drying at 90°C for 1.5 h.

[0046] (3) Pressure differential flash drying treatment: The material obtained in step (2) is placed in a sealed expansion tank and maintained at 90°C for 10 minutes to ensure that the sample temperature is consistent. Saturated hot steam is introduced to raise the pressure in the tank to 0.6 PMa and maintained for 30 seconds. The instantaneous switch valve is automatically opened to instantly reduce the pressure, so that the pressure in the expansion tank is instantly reduced to 0.003-0.005MPa within tens of milliseconds. This is a pressure differential flash process. After repeating the pressure differential flash once, it is dried under 90°C and a pressure of 0.004 MPa for 20 minutes, and then the air valve is opened to restore the pressure in the expansion tank to atmospheric pressure, and the obtained material is collected.

[0047] (4) Isolation and purification of fluorescent carbon dots: Take 10 g of the material obtained in step (3), add 100 mL of 10% (v / v) ethanol solution, extract in a 50°C water bath for 1 h, centrifuge to remove insoluble matter, and obtain a supernatant. The supernatant is passed through a dialysis bag with a molecular weight cutoff of 1000 Da, dialyzed for 3 days, and freeze-dried to obtain a brown solid powder, which is the fluorescent carbon dots. The yield of fluorescent carbon dots is 84.3% and the purity is 57%.

[0048] Example 2 This example is the application of fluorescent carbon dots in the detection of chlorogenic acid. The steps of detecting chlorogenic acid are as follows: Step 1), dispersing the solid powder of fluorescent carbon dots in deionized water to prepare a fluorescent carbon dot solution with a concentration of 5 mg / mL; Step 2), prepare 0.5 mL of chlorogenic acid solution of different concentrations, add 1.5 mL of fluorescent carbon dot solution respectively, mix and react, obtain a series of mixed solutions of chlorogenic acid of equal volume and different concentrations, detect the fluorescence intensity of each solution, and calculate the linear relationship between the ratio F0 / F of the strongest fluorescence intensity F between 400-500 nm and the strongest fluorescence intensity F between 700-800 nm and the chlorogenic acid concentration; the fluorescence emission spectra of the fluorescent carbon dots after reaction with different concentrations of chlorogenic acid are as follows Figure 3 As shown; Step 3), after adding 1.5 mL of fluorescent carbon dot solution to 0.5 mL of the sample to be tested, mixing and reacting to obtain a mixed solution of the sample to be tested, and then the fluorescence intensity of the mixed solution of the sample to be tested is detected; Step 4), according to the linear relationship between the ratio of fluorescence intensity F0 / F obtained in step 2) and the concentration of chlorogenic acid, the concentration of chlorogenic acid in the mixed solution of the sample to be tested is obtained; Among them, the concentration of chlorogenic acid solution is 0-1 μg / L; the fluorescence intensity detection parameters are: at an excitation wavelength of 370 nm, collect the spectrum with an emission wavelength of 400-800 nm, the excitation and emission slits are 2.5 nm, and the excitation voltage is 700V.

[0049] In the method of detecting the concentration of chlorogenic acid using dual-wavelength fluorescent carbon dots, the linear relationship between the ratio of fluorescence intensity F0 / F and the concentration of chlorogenic acid is as follows: Figure 4 As shown, it can be expressed as: Y=-0.4457X+1.0147R 2 =0.9708.

[0050] Compared with the fluorescent carbon quantum dots and their application in rapid detection of chlorogenic acid in authorization announcement No. CN115368891B, the detection range of chlorogenic acid is 0-0.003uM, and the detection limit of this application is lower and more sensitive.

[0051] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for preparing dual-wavelength fluorescent carbon dots, characterized in that: The following steps are involved: Step 1: Pre-treatment of apple raw materials: wash, peel and cut the raw materials into slices; Step 2: Pre-drying: pre-dry the material obtained in step 1; Step 3, differential pressure flash drying coupled with infrared pulse jet treatment: the material obtained in step 2 is placed in a sealed puffing tank, maintained at 80-110°C for 5-15 min, then saturated hot steam is introduced to raise the pressure in the puffing tank to 0.6 PMa, maintained for 30 s, then the pressure in the puffing tank is reduced to 0.003-0.005 MPa, and pulse infrared treatment is performed at the same time, and then vacuum drying is performed to rapidly puff and dry the apple material, and uniform and high-density fluorescent carbon dots are generated inside the material, and then the vent valve is opened to restore the pressure in the puffing tank to atmospheric pressure, and the obtained material is collected; Step 4: Separation and purification of fluorescent carbon dots: Separate and purify the material obtained in step 3.

2. The method for preparing dual-wavelength fluorescent carbon dots according to claim 1, characterized in that: In the step 1, the raw material is cut into slices of 5-8 mm.

3. The method for preparing dual-wavelength fluorescent carbon dots according to claim 1, characterized in that: In the step 2, the material obtained in the step 1 is placed in an oven and pre-dried at 80-100° C. for 1-2 hours.

4. The method for preparing dual-wavelength fluorescent carbon dots according to claim 1, characterized in that: In the step three, after the pulse infrared treatment, the product is dried under vacuum for 10-20 minutes at a temperature of 80-110° C. and a pressure of 0.004 MPa.

5. The method for preparing dual-wavelength fluorescent carbon dots according to claim 1, characterized in that: In step 3, the pulse infrared treatment is performed for 25 seconds, with a pulse interval of 5 seconds.

6. The method for preparing dual-wavelength fluorescent carbon dots according to claim 1, characterized in that: In the step 4, the specific steps of separating and purifying the fluorescent carbon dots are as follows: adding an ethanol solution with a volume ratio of 10-50% to the material obtained in step 3 to fully dissolve it, then extracting it in a 50°C water bath for 1 h, and then centrifuging it to obtain a supernatant; passing the obtained supernatant through a dialysis bag with a molecular weight cutoff of 1000Da, and dialyzing it for 3 days to obtain a purified fluorescent carbon dot solution; vacuum freeze-drying the purified fluorescent carbon dot solution to obtain a solid powder of the fluorescent carbon dots.

7. A method for detecting the concentration of chlorogenic acid using the dual-wavelength fluorescent carbon dots prepared according to claim 6, characterized in that: The following steps are involved: Step 1), dispersing the solid powder of fluorescent carbon dots in a solvent to prepare a fluorescent carbon dot solution; Step 2), prepare equal volumes of chlorogenic acid solutions of different concentrations, add equal volumes of fluorescent carbon dot solutions respectively, mix and react, obtain a series of equal volumes of mixed solutions of chlorogenic acid of different concentrations, detect the fluorescence intensity of each solution, and calculate the linear relationship between the ratio F0 / F of the strongest fluorescence intensity F between 400-500 nm and the strongest fluorescence intensity F between 700-800 nm and the chlorogenic acid concentration; Step 3), after adding the fluorescent carbon dot solution to the sample to be tested, mixing and reacting, a mixed solution of the sample to be tested is obtained, and then the fluorescence intensity of the mixed solution of the sample to be tested is detected; Step 4), according to the linear relationship between the ratio of fluorescence intensity F0 / F obtained in step 2) and the concentration of chlorogenic acid, the concentration of chlorogenic acid in the mixed solution of the sample to be tested is obtained; Among them, the concentration of chlorogenic acid solution is 0-1 μg / L; the fluorescence intensity detection parameters are: at an excitation wavelength of 370 nm, collect the spectrum with an emission wavelength of 400-800 nm, the excitation and emission slits are 2.5 nm, and the excitation voltage is 700V.

8. The method for detecting the concentration of chlorogenic acid using dual-wavelength fluorescent carbon dots according to claim 7, characterized in that: The linear relationship between the fluorescence intensity ratio F0 / F and the chlorogenic acid concentration is: Y=-0.4457X+1.0147 R 2 =0.9708; The linear range of detection was 0-1 μg / L.

9. The method for detecting the concentration of chlorogenic acid using dual-wavelength fluorescent carbon dots according to claim 7, characterized in that: The step 1) is specifically as follows: dispersing the solid powder of fluorescent carbon dots in water and / or ethanol to prepare a fluorescent carbon dot solution with a concentration of 5 mg / mL.

10. The method for detecting the concentration of chlorogenic acid using dual-wavelength fluorescent carbon dots according to claim 7, characterized in that: In the step 2), when mixed, the volume ratio of the chlorogenic acid solution to the fluorescent carbon dot solution is 1:3, and in the step 3), when the sample to be tested and the fluorescent carbon dot solution are mixed, the volume ratio is 1:3.

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