CN113234443A - Preparation method based on nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dots and application of carbon quantum dots in rapid detection of carmine - Google Patents

Preparation method based on nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dots and application of carbon quantum dots in rapid detection of carmine Download PDF

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CN113234443A
CN113234443A CN202110545771.9A CN202110545771A CN113234443A CN 113234443 A CN113234443 A CN 113234443A CN 202110545771 A CN202110545771 A CN 202110545771A CN 113234443 A CN113234443 A CN 113234443A
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carbon quantum
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胡钦
孙慧娟
刘凌飞
崔义坤
肖丽霞
杨振泉
饶胜其
杨明
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Abstract

A preparation method based on nitrogen, sulfur and chlorine co-doped carbon quantum dots and application thereof in fast detection of carmine relate to the technical field of nano luminescent material preparation and also relate to a detection technology of food. The nitrogen-phosphorus-chlorine-based co-doped carbon quantum dot is prepared by taking cheap glucose, ethylenediamine, phosphoric acid, hydrochloric acid and sulfuric acid as reaction precursors through an acid-base neutralization self-heat release method under the condition of not introducing an external heat sourceN,S,P,Cl-CDs. Based on nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dotsN,S,P,Clthe-CDs are used for CRM detection as fluorescent probes and have the advantages of good selectivity, strong anti-interference performance, high sensitivity and the likeCompared with the traditional CRM detection method, such as spectrophotometry, capillary electrophoresis, high performance liquid chromatography and voltammetry, the method also has the advantages of simplicity, rapidness and low cost.

Description

Preparation method based on nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dots and application of carbon quantum dots in rapid detection of carmine
Technical Field
The invention relates to the technical field of nano luminescent material preparation, and also relates to a food detection technology.
Background
Food colorants are a special food additive that is commonly used to improve the appearance, mouthfeel, aroma and color of food products, making them more attractive. Carmine (CRM) has been widely used in the food industry as an artificial pigment. CRM belongs to a synthetic azo pigment, is granular or powdery and has a color from red to deep red. CRM has been reported to exhibit some carcinogenic and mutagenic effects and to have some genotoxic potential. Thus, many countries strictly regulate the maximum usage limit of CRM in food products. For example, CRM is permitted to be used in china and the european union, and is prohibited from being used in the united states and japan. The food product is specified in CODEX in a limited amount of 50 to 500 mg/kg CRM addition. China allows CRM to be added to fruit juices, hawthorn products, candy, pickles and beverages in limited amounts not exceeding 50 mg/kg or 50 mg/L. The european union has specified a limit of 100 to 200 mg/kg for the use of CRM in food products of the type sausage, jam and red marbled cheese. Although different countries set strict standards for the amount of CRM added to food products, there may still be situations where CRM is added in excess during food processing. Therefore, developing a reliable and convenient method for detecting CRM is crucial to ensuring food safety and human health.
Currently, methods for detecting CRM content include spectrophotometry, capillary electrophoresis, High Performance Liquid Chromatography (HPLC), voltammetry, and the like. However, these analytical methods generally suffer from disadvantages such as complicated sample preparation procedures, expensive instruments, long analysis times and lack of skilled technicians. Therefore, there is a need to develop a method for detecting CRM in a food product in a simple, rapid, and accurate assay.
Carbon quantum dots (CDs) are a novel fluorescent carbon nano material which is similar to a sphere and has the particle size of less than 10 nm, and have the advantages of good water solubility, excellent fluorescence property, low biotoxicity, low cost and the like. In view of the excellent physicochemical properties, the compound shows great application prospects in the aspects of biological imaging, nanoprobes, photoelectric conversion and the like. In addition, because the surface of the CDs is rich in amino and carboxyl groups, the surface of the CDs is easy to functionalize, and therefore, the doped CDs can be prepared by selecting a proper heteroatom (such as nitrogen, sulfur, fluorine and the like) donor, so that the fluorescence quantum yield of the CDs can be improved, and the sensitivity of the CDs on the detection of a target object can be enhanced. At present, a great deal of research shows that the doped CDs have the advantages of high sensitivity and high selectivity in the detection aspect of food additives such as curcumin, melamine, tannic acid and the like. Recent studies have shown that CDs can be used as an effective fluorescence detection method for CRM detection, but work on this aspect is rarely reported so far, and only two documents report this aspect so far. Su et al prepared CDs from dried lemon peel by hydrothermal method and used them for detecting lemon yellow in food sample, with detection limit of 0.28 μ M. Hu et al prepared nitrogen-doped CDs (using m-phenylenediamine as carbon source) ((NCDs) with a limit of detection of tartrazine of 11.2 nM. Therefore, a new path for preparing CDs needs to be searched to improve the sensitivity of a CDs probe to the detection of the tartrazine to the maximum extent, so that a theoretical basis and a technical platform are provided for developing a portable rapid tartrazine detection device.
Disclosure of Invention
Aiming at the defect of the sensitivity of the conventional carmine detection technology based on CDs, the invention provides a preparation method of nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dots.
The technical scheme of the invention is as follows: mixing glucose, ethylenediamine, concentrated phosphoric acid, concentrated hydrochloric acid and concentrated sulfuric acid at normal temperature for reaction, cooling after the reaction is finished, dialyzing by using a dialysis membrane, and freeze-drying to obtain nitrogen, sulfur and chlorine co-doped carbon quantum dots N, S, P, Cl-CDs.
The nitrogen-phosphorus-chlorine-based co-doped carbon quantum dot is prepared by taking cheap glucose, ethylenediamine, phosphoric acid, hydrochloric acid and sulfuric acid as reaction precursors through an acid-base neutralization self-heat release method under the condition of not introducing an external heat sourceN,S,P,Cl-CDs。
According to the process, an external heat source is not required to be introduced, and the carbon source can be carbonized only by acid-base neutralization and self-heat release of reaction raw materials to prepare the nitrogen-phosphorus-chlorine co-doped carbon quantum dot.
Based on nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dotsN,S,P,Clthe-CDs are used as fluorescent probes for CRM detection, not only have the advantages of good selectivity, strong anti-interference performance, high sensitivity and the like, but also have the advantages of simplicity, rapidness and low cost compared with the traditional CRM detection method such as spectrophotometry, capillary electrophoresis, High Performance Liquid Chromatography (HPLC) and voltammetry.
Furthermore, the feeding volume ratio of the glucose, the ethylenediamine, the concentrated phosphoric acid, the concentrated hydrochloric acid and the concentrated sulfuric acid is 0.2 g: 3 mL: 1 mL. Carbon sources and heteroatom donors are required for the synthesis of doped carbon quantum dots. In the present invention, glucose is the carbon source and ethylenediamine, concentrated phosphoric acid, concentrated hydrochloric acid and concentrated sulfuric acid are the donors of N, P, Cl and S atoms, respectively. The ethylenediamine is alkaline, and after being mixed with several strong acids, the ethylenediamine can quickly release heat due to the neutralization of acid and alkali, so that glucose is carbonized, and nitrogen, sulfur and phosphorus chloride co-doped carbon quantum dots can be instantly prepared.
Furthermore, the MWCO of the dialysis membrane is 500-1000 Da. The dialysis membrane was chosen to filter out small molecules in the reaction product, resulting in purified carbon quantum dots. The dialysis membrane with the cut-off molecular weight of 500-1000 Da is of a size commonly used in the literature, and the dialysis membrane with the size is dialyzed in 1L of ultrapure water for 3 days, so that small molecules in a reaction product can be removed.
Further, new ultrapure water was injected every 12 hours during the dialysis, and the dialysis time was 3 days.
During dialysis, a reaction product is filled into a dialysis bag, the mouth of the dialysis bag is screwed down, the dialysis bag is placed into a beaker filled with 1L of ultrapure water, dialysis is carried out for three days, the ultrapure water in the beaker is poured out every 12 hours, and the ultrapure water is replaced by fresh ultrapure water. The reaction product is dialyzed for 3 days in 1L of ultrapure water through a dialysis membrane with the molecular weight cutoff of 500-1000 Da, so that small molecules in the reaction product can be removed.
The invention also aims to provide nitrogen-phosphorus-chlorine co-doped carbon quantum dotsN,S,P,ClThe use of CDs in the rapid detection of carmine.
The invention comprises the following steps:
1) mixing ultrapure water and nitrogen, sulfur and phosphorus-based chlorine co-doped carbon quantum dots N, S, P, Cl-CDs to obtain a N, S, P, Cl-CDs solution;
2) mixing carmine with N, S, P, Cl-CDs solution to obtain at least two mixed solutions with different carmine concentrations, respectively measuring fluorescence intensity of the mixed solutions with different carmine concentrations to obtain fluorescence quenching efficiency F0Linear relationship of/F and CRM concentration in the mixed solution;
3) mixing a sample to be detected with the N, S, P, Cl-CDs solution to obtain a sample mixed solution to be detected, and measuring the fluorescence intensity of the sample mixed solution to be detected;
4) according to fluorescence quenching efficiency F0And obtaining the concentration of the carmine in the mixed solution of the sample to be detected according to the linear relation between the/F and the CRM concentration in the mixed solution.
The invention is based onN,S,P,ClThe fluorescence method of CDs is used for the rapid detection of carmine, and the sensitivity obtained by the method is far higher than that of the existing fluorescence detection method based on CDs. In addition, the method also has the advantages of high selectivity, good anti-interference performance, high accuracy, simple and convenient operation, low cost and the like, and can be used for detecting the carmine in the complex food matrix. The invention solves the problem of the insufficient sensitivity of the existing CDs probe to the carmine detection, and the obtained detection limit is as low as 9.13 nM, which is obviously superior to the existing fluorescence detection method based on CDs. Therefore, the method has good application and popularization values.
Further, theN,S,P,ClConcentration of N, S, P, Cl-CDs based on nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dots in CDs solutionIt was 0.03 mg/mL. The influence of different N, S, P, Cl-CDs concentrations on the detection of CRM is found by examination, and the result is as follows: with varying concentrations of N, S, P, Cl-CDs, F0The concentration of F/F was varied, and when the concentration of N, S, P, Cl-CDs was 0.03mg/mL, F was0the/F increases to a maximum value. Therefore, the preferred concentration of the present invention is 0.03mg/mLN,S,P,ClCDs solution as the optimal N, S, P, Cl-CDs concentration for CRM detection.
Further, the fluorescence intensities in the steps 2) and 3) are respectively at lambdaexIs 380nm, lambdaemMeasured at 453 nm. Repeated experiments prove that the wavelength is selected because of the excitation wavelength lambdaexAt 380nm, the intensity of the emission wavelength is strongest, which is the central position of the emission wavelength, i.e., λemAt 453 nm.
Further, in step 2), the fluorescence intensity was measured 1 min after mixing carmine with N, S, P, Cl-CDs solution. The fluorescence intensity of the reaction system is mixed at different time intervals, the influence of the reaction time on the detection of CRM is repeatedly investigated, and F is found after CRM is added into N, S, P, Cl-CDs solution0the/F rises rapidly within 1.0 min and then remains in steady state. Therefore, the invention selects 1.0 min as the detection time of the optimal fluorescence intensity.
Similarly, in the step 3), the fluorescence intensity is detected 1 min after the sample to be detected is mixed with the N, S, P, Cl-CDs solution.
Drawings
FIG. 1 is a TEM image of nitrogen-phosphorus-chlorine-based co-doped carbon quantum dots N, S, P, Cl-CDs.
FIG. 2 is a particle size distribution histogram of N, S, P, Cl-CDs based on nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dots
FIG. 3 is an FTIR chart based on nitrogen-phosphorus-chlorine co-doped carbon quantum dots N, S, P, Cl-CDs.
FIG. 4 is a diagram of an ultraviolet-visible absorption spectrum, a fluorescence excitation spectrum and an emission spectrum of N, S, P, Cl-CDs based on nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dots.
FIG. 5 is a fluorescence lambda em spectrum diagram of N, S, P, Cl-CDs based on nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dots under different lambda ex.
FIG. 6 is a fluorescence spectrum intensity integral diagram of the absorption intensity of quinine sulfate and nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dots N, S, P, Cl-CDs.
FIG. 7 is a graph showing the effect of CRM concentration on the fluorescence intensity of N, S, P, Cl-CDs based on nitrogen, sulfur and phosphorus co-doped carbon quantum dots.
FIG. 8 is F0Graph of linear dependence of/F on CRM concentration.
FIG. 9 is a graph of selectivity of N, S, P, Cl-CDs to small molecules such as CRM and various amino acids and anions and cations based on nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dots.
FIG. 10 is an anti-interference diagram of N, S, P, Cl-CDs based on nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dots on small molecules such as CRM and various amino acids and anions and cations.
Detailed Description
1. Preparation of nitrogen-phosphorus-chlorine-based co-doped carbon quantum dotN,S,P,Cl-CDs：
0.4 g of glucose was weighed into a 50.0 mL glass beaker, and 6 mL of ethylenediamine and 2 mL of concentrated H were added in that order3PO42 mL concentrated HCl and 2 mL 70% H2SO4. Under the self-exothermic neutralization of the acid and base, the reaction mixture became foamy within seconds. The obtained reaction product is naturally cooled to room temperature, dialyzed and stirred for 3 days by a dialysis membrane (MWCO = 500-1000 Da). Injecting new ultrapure water every 24 h during dialysis to obtainN,S,P,Cl-a CDs solution. Finally, freeze drying is carried out to obtain nitrogen-sulfur-phosphorus-chlorine co-doped carbon quantum dotsN,S,P,Cl-CDs powder.
2. Nitrogen-phosphorus-chlorine-based co-doped carbon quantum dotN,S,P,Cl-CDsThe physical and chemical properties are characterized as follows:
characterization of carbon quantum dots based on nitrogen, sulfur, phosphorus and chlorine co-doping by adopting TEM methodN,S,P,Cl-CDsThe morphology and the size distribution of the prepared nitrogen-phosphorus-chlorine-based co-doped carbon quantum dot are shown in figure 1N,S,P,Cl-CDs have good dispersibility and a sphere-like structure.
Fig. 2 is a particle size distribution histogram obtained by randomly counting the sizes of 90 particles on an electron micrograph. Nitrogen-phosphorus-chlorine-based co-doped carbon quantum dotN,S,P,ClThe particle size distribution range of CDs is 2.0-11.2 nm, and the average particle sizeThe diameter is 5.56 +/-0.3 nm.
Fourier infrared spectrum is adopted to co-doped carbon quantum dots based on nitrogen, sulfur, phosphorus and chlorineN,S,P,ClThe functional groups of the CDs are characterized, as shown in figure 3, by 3500-3350 cm-1And 3150-2760 cm-1The wide absorption peak of the strain belongs to ‒ NH and ‒ OH telescopic vibration, 1670 cm-1Strong absorption peak from C = O stretching vibration, indicating thatN,S,P,ClThe CDs have amino and carboxyl on the surface and have good water solubility. 1250 cm-1The absorption peak at (a) is due to C — O stretching vibrations. 2300. 1500, 1180, 995 and 827 cm-1The strong absorption peaks at (A) were attributed to S-H stretching vibration, N-H bending, C-N stretching, P-O-C bending and C-Cl stretching vibration, respectively, N, P, S and the Cl heteroatom were successfully doped into CDs.
Research on nitrogen, sulfur, phosphorus and chlorine based co-doped carbon quantum dots through ultraviolet visible absorption spectrum (UV-Vis)N,S,P,ClThe UV absorption properties of CDs. As shown in figure 4, based on nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dotsN,S,P,Cl-The UV-Vis spectrum of CDs has two typical absorption peaks in the UV region, 290 nm due to n → pi transition of C = O bond and 385 nm due to surface excited states caused by N, P, S and Cl heteroatoms.
Researches on nitrogen-phosphorus-chlorine co-doped carbon quantum dots by adopting fluorescence spectrumN,S,P,ClThe fluorescence properties of CDs. Nitrogen-phosphorus-chlorine-based co-doped carbon quantum dotN,S,P,ClThe excitation spectrum of CDs is shown in FIG. 4,N,S,P,Clthe excitation peak of CDs is at 380 nm. From FIG. 4N,S,P,ClThe emission spectrum of the CDs shows,N,S,P,Clthe emission peak of CDs when excited at 380nm is 453 nm. FIG. 5 is a drawing showingN,S,P,Cl-CDs at different excitation wavelengths (λ)ex) Fluorescence spectrum of (1). When lambda isexWhen the wavelength is increased from 300 nm to 500 nm,N,S,P,Cl-emission wavelength (λ) of CDsem) Continuously red-shifted in the range of 453 nm to 553 nm, i.e.N,S,P,Cl-λ of CDsemExhibit a typical lambdaexDepending on the behavior.
As shown in FIG. 6, quinine sulfate was used as a reference substance and was measuredN,S,P,Cl-The quantum yield of CDs was 5.80%.
3. Making a linear relationship:
based on nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dotsN,S,P,Cl-CDs powder dissolved in ultrapure water, obtainingN,S,P,ClCDs concentration of 0.03mg/mLN,S,P,Cl-a CDs solution.
We know key experimental conditions that influence fluorescence quenching efficiency, includingN,S,P,ClConcentration of CDs solution, pH value of reaction system and reaction time. When the influence of pH value on detection is studied, the result shows that the fluorescence quenching efficiency F0The difference of the pH value of the ultra-pure water (pH value is about 6.5) and the pH value of the ultra-pure water is not greatly changed within the range of pH = 2.0-11.0. Therefore, in order to simplify the amount of detection work and improve the efficiency of detection work, ultrapure water is selected as the optimal solution for detecting CRM.
CRM was compared with the 2.0 mL obtained aboveN,S,P,ClCDs solution was mixed to obtain mixed solutions having CRM concentrations of 0.1. mu.M, 0.5. mu.M, 1. mu.M, 2. mu.M, 3. mu.M, 4. mu.M, 5. mu.M, 6. mu.M, 7. mu.M, 8. mu.M, 9. mu.M, 10. mu.M, 11. mu.M, 12. mu.M, 13. mu.M, and 14. mu.M, respectively.
At λexIs 380nm, lambdaemThe fluorescence intensity of the above mixed solutions containing different CRM concentrations was measured at 453 nm. Additional measurement of blank without CRM additionN,S,P,Cl-fluorescence intensity of the CDs solution.
Plotting fluorescence quenching efficiency F0Linear plot of/F versus CRM concentration in mixed solution, where F0And F represents blank before CRM additionN,S,P,ClFluorescence intensity of the CDs solution, mixed solution after addition of CRM.
Fig. 7 shows the change in luminescence intensity of the mixed solution in the presence of CRM at different concentrations. As can be seen, when the CRM concentration is increased (curve 0-105 mu M), the fluorescence intensity of the mixed solution is gradually reduced, which shows that CRM can effectively quenchN,S,P,Cl-fluorescence intensity of CDs.
FIG. 8 shows that the concentration of CRM is in the range of 0.01-14.0 mu M, the fluorescence intensity of the mixed solution and the concentration of CRM are in a good linear relationship, and CRM pairsN,S,P,ClThe quenching of-CDs follows the Stern-Volmer equation. The proposed fluorescence method has an LOD of 9.13 nM. Comparing the present invention with the previously reported fluorescence detection method of carmine based on CDs, the results show that the present invention is based onN,S,P,ClThe sensitivity of the detection method of CDs is far lower than that of the previously reported CDs-based cochineal red fluorescence detection method of 11.2 nM, which indicates that the detection method of the invention has high sensitivity.
4. And (3) selectivity:
at 2.0 mLN,S,P,ClThe CDs solution (0.03 mg/mL) was supplemented with interfering substances that may be present in the actual sample, including 15 amino acids (methionine, serine, arginine, threonine, histidine, L-methionine, DL-cysteine, tyrosine, glycine, leucine, glutamic acid, alanine, tryptophan, aspartic acid and phenylalanine), 3 small molecules (GSH, glucose and ascorbic acid), 10 anions (F)-，Br-，I-，Cl-，NO3 -，HCO3 -，CO3 2-，SO4 2-，H2PO4 - And HPO4 2-) And 8 cations (Na)+，Ag+，K+，NH4 +，Mg2+，Zn2+，Fe2+ And Ca2+) The concentration of each interfering substance added was 0.1 mM at lambdaexIs 380nm, lambdaemBefore adding interferents for the measurement at 453 nmN,S,P,ClFluorescence intensity of the CDs solution and the mixed solution after addition of the interferent.
As shown in FIG. 9, only the addition of CRM significantly quenchedN,S,P,ClFluorescence intensity of CDs, interfering substance pairs possibly presentN,S,P,ClThe effect of the fluorescence intensity of CDs is almost negligible, indicating thatN,S,P,ClCDs have a high selectivity for CRM.
5. Anti-interference performance:
the invention investigatesN,S,P,Cl-CDsImmunity to CRM detection.
To the direction ofN,S,P,Cl-CDsCRM was added to the solution (0.1 mg/mL) inN,PThe concentration of the CDs solution is 0.01 mM, and the above possible interfering substances are added to the CDs solution at a concentration of 0.1 mM. At λexIs 380nm, lambdaemBefore adding interferents for the measurement at 453 nmN,S,P,Cl-fluorescence intensity of the CDs solution, mixed solution after addition of interferents.
As shown in fig. 10, in the direction ofN,S,P,ClThe absence of a significant change in fluorescence intensity after addition of the interfering substances possibly present in the mixed system-CDs (0.03 mg/mL)/CRM (0.01 mM) indicatesN,S,P,ClStrong interference immunity of CDs.
6. And (3) actual sample testing:
the CRM-containing food samples for the following experiments, including dried plum, dried peach, sweetened roll, strawberry jam, watermelon frost and functional beverage, were all from local supermarkets.
Firstly, grinding or shearing dried plum, dried peach, sweetened roll, strawberry jam and watermelon frost, then weighing 0.6 g of solid sample, dissolving in 10 mL of ultrapure water, and carrying out ultrasonic treatment for 10 min. The mixture was centrifuged at 10000 rpm for 5 min, and five supernatant samples were collected.
Taking a proper amount of functional beverage, performing ultrasonic treatment for 20 min to remove bubbles in the sample, accurately measuring 5.0 mL, and diluting to 25 mL with ultrapure water to obtain a functional beverage sample.
The five supernatant samples and the functional beverage samples were filtered through cellulose acetate membranes (0.22 μm, 26 mm inner diameter, sold by Tianjin Jinteng Co., Ltd.) respectively to obtain six clear extracts for parallel tests.
Respectively taking 20 mu L of extracting solution and adding 2 mL of extracting solution N,S,P,ClCDs (0.03 mg/mL) in solution, corresponding mixed solutions being obtained, at lambdaexIs 380nm, lambdaemThe fluorescence intensity of each mixed solution was measured at 453 nm.
In addition, a national standard method, namely an HPLC method is adopted to detect the CRM content in the six clear extracting solutions so as to verify the accuracy of the method.
As shown in table 1, CRM contents in the dried plum, the dried nectarine, the sweetened roll, the strawberry jam, the watermelon crystal, and the functional beverage extract were 0.14, 0.11, 0.13, 0.29, 0.17, and 0.12 μ M, respectively. The spiked recovery was determined by spiking the extract of the above sample with four concentration levels of standard solution, showing a spiked recovery in the range of 97.7-104.6% and a Relative Standard Deviation (RSD) of less than 4.15%, indicating a higher accuracy of the method. In addition, the CRM content in the sample is also analyzed by an HPLC (national standard method), and the result shows that the two methods obtain very close results, thereby further proving that the method has high accuracy.
TABLE 1 comparison of CRM assay results in food samples
Figure DEST_PATH_IMAGE001

Claims (9)

1. The preparation method based on nitrogen, sulfur, phosphorus and chlorine co-doped carbon quantum dots is characterized by comprising the following steps: mixing glucose, ethylenediamine, concentrated phosphoric acid, concentrated hydrochloric acid and concentrated sulfuric acid at normal temperature for reaction, cooling after the reaction is finished, dialyzing by using a dialysis membrane, and freeze-drying to obtain nitrogen, sulfur and chlorine co-doped carbon quantum dots N, S, P, Cl-CDs.
2. The method according to claim 1, wherein the feeding volume ratio of the glucose, the ethylenediamine, the concentrated phosphoric acid, the concentrated hydrochloric acid and the concentrated sulfuric acid is 0.2 g: 3 mL: 1 mL.
3. The method according to claim 1, wherein the cut-off molecular weight MWCO of the dialysis membrane is 500-1000 Da.
4. The method according to claim 1, wherein ultrapure water is injected every 12 hours during the dialysis, and the dialysis time is 3 days.
5. The application of the nitrogen-phosphorus-chlorine-based co-doped carbon quantum dot N, S, P, Cl-CDs obtained by the preparation method of claim 1 in the rapid detection of carmine is characterized by comprising the following steps:
1) mixing ultrapure water and nitrogen, sulfur and phosphorus-based chlorine co-doped carbon quantum dots N, S, P, Cl-CDs to obtain a N, S, P, Cl-CDs solution;
2) mixing carmine with N, S, P, Cl-CDs solution to obtain at least two mixed solutions with different carmine concentrations, respectively measuring fluorescence intensity of the mixed solutions with different carmine concentrations to obtain fluorescence quenching efficiency F0Linear relationship of/F and CRM concentration in the mixed solution;
3) mixing a sample to be detected with the N, S, P, Cl-CDs solution to obtain a sample mixed solution to be detected, and measuring the fluorescence intensity of the sample mixed solution to be detected;
4) according to fluorescence quenching efficiency F0And obtaining the concentration of the carmine in the mixed solution of the sample to be detected according to the linear relation between the/F and the CRM concentration in the mixed solution.
6. Use according to claim 5, characterized in that saidN,S,P,ClThe concentration of N, S, P, Cl-CDs based on nitrogen, sulfur and phosphorus co-doped carbon quantum dots in the CDs solution is 0.03 mg/mL.
7. Use according to claim 5, wherein the fluorescence intensity in steps 2) and 3) is at λexIs 380nm, lambdaemMeasured at 453 nm.
8. The use according to claim 5, wherein in step 2) the fluorescence intensity is measured 1 min after mixing the carmine with the N, S, P, Cl-CDs solution.
9. The use according to claim 5, wherein in step 3), the fluorescence intensity is measured 1 min after the sample to be tested is mixed with the N, S, P, Cl-CDs solution.
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