Fluorescent carbon quantum dots, preparation method thereof, and application in atrazine detection

Abstract

The present invention discloses a kind of fluorescent carbon quantum dots and its preparation method and application in atrazine detection, and belongs to the technical field of pesticide residue detection. The carbon quantum dots in the present invention are obtained by hydrothermal reaction, centrifugation, dialysis, nitrogen blowing and freeze drying with citric acid and o-phenylenediamine as raw materials and a mixed solution of ethanol and water as solvent. The preparation method in the present invention has low equipment requirements, simple operation and low cost. The fluorescent carbon quantum dots prepared by the method in the present invention have the characteristics of good fluorescence stability, good water solubility, good selectivity for atrazine and high sensitivity. The detection method in the present invention shows that the fluorescence enhancement degree of the fluorescent carbon quantum dots is linearly correlated with the atrazine concentration, and the detection limit of the detection method is as low as 20ng / L, and the detection result is fast and accurate. Therefore, the present invention can be used for fast, accurate and sensitive detection of atrazine in actual samples.

Description

Technical Field

[0001] The invention belongs to the technical field of pesticide residue detection, and in particular relates to fluorescent carbon quantum dots, a preparation method thereof, and application of the fluorescent carbon quantum dots in atrazine detection. Background Art

[0002] Atrazine, a common triazine herbicide also known as atrazine, chloramphenicol, and chloramphenicol, is widely used for crop growth regulation and weed control. The main hazard of atrazine residues lies in their potential impacts on the environment and human health. While this herbicide plays an important role in agriculture, its residues can lead to soil and water pollution, impacting the balance of ecosystems. Furthermore, long-term exposure to agricultural products containing atrazine residues may pose risks to human health, such as neurological problems and endocrine disruption. Therefore, when applying atrazine, strict adherence to regulatory guidelines is crucial, ensuring proper application and regular residue testing to safeguard food safety and protect the environment. Furthermore, the World Health Organization's International Agency for Research on Cancer listed atrazine as a Group 3 carcinogen in its preliminary list of carcinogens, published on October 27, 2017. Therefore, research on atrazine detection methods is of great significance. Traditional atrazine detection methods include liquid chromatography, gas chromatography, and mass spectrometry. However, these traditional detection methods all have a common problem: the instruments are expensive, the operation steps are cumbersome and time-consuming, the sensitivity is low, and the requirements for operators are high.

[0003] Carbon quantum dot fluorescent probes are a new type of fluorescent material with a narrow fluorescence emission peak, high fluorescence intensity, good chemical stability, and a variety of preparation methods. These characteristics make carbon quantum dots have broad application prospects in the field of fluorescent probes. First, the fluorescence properties of carbon quantum dots are stable and are not easily affected by environmental factors such as pH and temperature. This enables carbon quantum dot fluorescent probes to provide stable fluorescence signals in complex biological environments. Second, carbon quantum dots have good biocompatibility and low toxicity, making them ideal fluorescent probes in the biomedical field. Through surface modification, the water solubility, dispersibility and stability of carbon quantum dots can be further improved, and their fluorescence properties and biocompatibility can also be regulated. In addition, the preparation methods of carbon quantum dot fluorescent probes are diverse, and carbon quantum dots with different morphologies, sizes and optical properties can be obtained through different preparation methods. This provides more possibilities for the research and development of carbon quantum dot fluorescent probes with excellent performance.

[0004] In summary, carbon quantum dot fluorescent probes have promising application prospects and development potential. With the in-depth study of their preparation, modification, properties, and applications, they are expected to play an even more important role in biomedicine, anti-counterfeiting imaging, analytical detection, and other fields in the future. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides a kind of fluorescent carbon quantum dots and its preparation method and application in atrazine detection. The carbon quantum dots in the present invention are obtained by hydrothermal reaction, centrifugation, dialysis, nitrogen blowing and freeze drying with citric acid and o-phenylenediamine as raw materials and a mixed solution of ethanol and water as solvent. The preparation method in the present invention has low equipment requirements, simple operation and low cost. The fluorescent carbon quantum dots prepared using the method in the present invention have the characteristics of good fluorescence stability, good water solubility, good selectivity for atrazine and high sensitivity. The detection method in the present invention shows that the fluorescence enhancement degree of the fluorescent carbon quantum dots is linearly correlated with the atrazine concentration, and the detection limit of the detection method is as low as 20ng / L, and the detection result is fast and accurate. Therefore, the present invention can be used for rapid, accurate and sensitive detection of atrazine in actual samples.

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

[0007] One of the purposes of the present invention is to provide a method for preparing carbon quantum dots. The preparation method uses citric acid, o-phenylenediamine, ethanol and ultrapure water as raw materials and is carried out by a high-temperature hydrothermal method. The specific steps include: first, fully dissolving citric acid and o-phenylenediamine in a mixed solution of ethanol and ultrapure water, then heating at 150-200°C in a high-temperature and high-pressure reactor for 6-16 hours, cooling to room temperature, and then removing large particle impurities and small molecular substances, and finally blowing with nitrogen and freeze-drying to obtain a solid powder, which is the carbon quantum dots.

[0008] Preferably, the volume ratio of the ethanol to the ultrapure water is 1:(0.5-1.5), the dissolved concentration of the citric acid in the mixed solution is 2-6 g / L, and the dissolved concentration of the o-phenylenediamine in the mixed solution is 2-18 g / L.

[0009] More preferably, the usage ratio of the citric acid to the o-phenylenediamine is 1:(1-3).

[0010] More preferably, the amounts of the citric acid and the o-phenylenediamine are 0.2 g and 0.4 g, respectively, and the amounts of the ethanol and the ultrapure water are 20 ml, respectively.

[0011] Preferably, the large particle impurities are removed by filtration, and the small molecular substances are removed by dialysis, wherein the filtration and dialysis are performed by filtering the solution after the heating reaction with a 0.22 μm organic membrane and dialyzing it with a 1000 Da dialysis bag for 48 hours.

[0012] A second object of the present invention is to provide carbon quantum dots, which are prepared by using the preparation method.

[0013] A third object of the present invention is to provide a method for rapid detection of atrazine based on a carbon quantum dot fluorescent probe, wherein the method comprises using the carbon quantum dots and specifically comprises the following steps:

[0014] (1) Preparation of synthetic carbon quantum dots: The preparation method includes using the above-mentioned carbon quantum dot preparation method;

[0015] (2) Establishing a linear standard curve: Take several centrifuge tubes, first add the carbon quantum dot solution prepared in step (1), then add different concentrations of atrazine solution, then add buffer solution and mix well, heat at 38-42°C for 8-12 minutes, then fix the excitation wavelength to 320-420nm to obtain the fluorescence intensity, and finally use the ratio of the fluorescence intensity before and after adding atrazine as the ordinate and the concentration of atrazine as the abscissa to establish a linear relationship, and calculate the corresponding regression equation;

[0016] (3) Eliminate possible interference: Take possible coexisting substances of atrazine and follow step (2);

[0017] (4) Sample pretreatment;

[0018] (5) Determination of atrazine content: Take the carbon quantum dots in step (1) and add buffer solution, then add the pretreatment solution obtained by sample pretreatment in step (4), and then heat at a constant temperature of 38-42°C for 8-12 minutes, fix the excitation wavelength to 320-420nm, the excitation slit to 5nm, and the emission slit to 10nm, and obtain the fluorescence intensity. The fluorescence intensity after adding atrazine at an emission wavelength of 490nm is compared with the fluorescence intensity before adding atrazine and substituted into the equation constructed in step (2) for calculation to obtain the atrazine content in the sample.

[0019] Preferably, the concentration of the carbon quantum dot solution in step (2) is 0.5-1.5×10 -6 g / mL, and the amount added to each centrifuge tube was 3-5 mL.

[0020] Preferably, the concentration of the atrazine solution in step (2) is set to 0, 10, 20, 50, 80, 100, 150, 200, 300, 400, 500, 600, 800, 1000, 1200 ng / L, and the amount added to each centrifuge tube is 280-320 μL.

[0021] Preferably, the buffer in step (2) is acetate buffer, has a pH value of 4-7, and is added in an amount of 4-6 mL.

[0022] When the concentration range of atrazine is 15-800 ng / L, the corresponding linear regression equation is y=0.0085x+1.2827, where x is the concentration of atrazine and the linear regression coefficient R2 =0.9883, and the detection limit is 20 ng / L.

[0023] Preferably, the possible coexisting substances of atrazine in step (3) are imidacloprid, chlorpyrifos, cypermethrin, melamine, triadimenol, pyraclostrobin, Cu 2+ 、Fe 3+ and K + Any one or more of .

[0024] Preferably, when the sample in step (4) is a fruit or vegetable sample, the pretreatment method is: first, juice is squeezed, then a mixed solution of an appropriate amount of acetonitrile and water is added for filtration extraction, and then refrigerated and stored in a low-temperature refrigerator. The filtration is performed by filtering the extract through a 0.22 μm organic membrane.

[0025] Using the method of the present invention, the fluorescence response to atrazine is completed within 8 minutes and can remain stable for a long time.

[0026] A fourth object of the present invention is to provide an application of the preparation method, the carbon quantum dots or the atrazine rapid detection method in atrazine detection.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention utilizes the fluorescence properties of carbon quantum dots to detect atrazine, which can quickly and sensitively measure the concentration of atrazine in the sample without adding other fluorescent groups. It is environmentally friendly and economical, with a relatively fast response, outstanding selectivity and low cost.

[0029] 2. The carbon quantum dots described in this invention have good selectivity, and the common heavy metal ions Cu 2+ 、Fe 3+ and K + Other pesticides, such as imidacloprid, cypermethrin, and triadimenol, have little effect on atrazine detection. Therefore, selective detection of atrazine can be achieved without enzyme labeling, avoiding data discrepancies caused by enzyme inactivation.

[0030] 3. The method provided by the present invention can respond quickly to atrazine, and the stability time after the response is relatively long, and can be continuously stable for more than 90 minutes. This rapid detection method has good application prospects.

[0031] 4. The raw materials used in the present invention are easily available, the preparation method is simple, the prepared material has good stability and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is an infrared spectrum of the carbon quantum dot material in Example 1 of the present invention;

[0033] Figure 2 This is the X-ray photoelectron spectrum of the carbon quantum dots in Example 1 of the present invention;

[0034] Figure 3 The excitation and emission spectra of the carbon quantum dot material in Example 1 of the present invention are shown;

[0035] Figure 4 The fluorescence intensity of the carbon quantum dot material prepared under different experimental conditions in Example 1 of the present invention after combining with atrazine;

[0036] Figure 5 Graph showing the fluorescence intensity response of the carbon quantum dot material to different concentrations of atrazine in Example 2 of the present invention;

[0037] Figure 6 This is the standard curve diagram after fitting in Example 2 of the present invention;

[0038] Figure 7 This is the investigation result of the interaction time between atrazine and the fluorescent probe in Example 3 of the present invention;

[0039] Figure 8 The results of the investigation of atrazine and the fluorescent probe at different pH values ​​in Example 3 of the present invention are shown;

[0040] Figure 9 This is an interference diagram of the fluorescence intensity caused by some common interfering substances in Example 4 of the present invention. DETAILED DESCRIPTION

[0041] The following examples are intended to illustrate the present invention but are not intended to limit the scope of the present invention. Any modifications or substitutions to the methods, steps, or conditions of the present invention without departing from the spirit and essence of the present invention are intended to be within the scope of the present invention. Products, equipment, and the like used in the following examples are commercially available unless otherwise specified, and the methods used are consistent with conventional methods unless otherwise specified.

[0042] The technical solution of the present invention is further elaborated in detail below in conjunction with embodiments.

[0043] Example 1 Preparation process of fluorescent carbon quantum dots

[0044] Carbon quantum dots were prepared using a hydrothermal synthesis method. 0.2g of citric acid and 0.4g of o-phenylenediamine were dissolved in a mixture of 20ml of ethanol and 20ml of ultrapure water. Ultrasonication was then used to fully dissolve the mixture. The mixture was then placed in a 100ml high-temperature, high-pressure reactor and heated at 180°C for 12 hours. After cooling to room temperature, the mixture was filtered through a 0.22μm organic filter membrane to remove large particles. The filtrate was then dialyzed through a 1000Da dialysis bag to remove small molecules. Finally, nitrogen purging and freeze-drying were performed to obtain a solid powder of carbon quantum dots, which was then refrigerated at 4°C for storage.

[0045] The carbon quantum dot material prepared in Example 1 was characterized by infrared spectroscopy. Figure 1 is the infrared spectrum of carbon quantum dot material, Figure 1 It can be seen that there is also a benzene ring structure in the structure, which contains amino, hydroxyl functional groups, CO, and NH groups. Figure 2 This is the X-ray photoelectron spectrum of the prepared carbon quantum dot material. From the peaks at 284.8, 400.4 and 531.7 eV, it can be determined that the material contains C, N, O elements and their approximate content ratios. Figure 3 This is the excitation emission spectrum of carbon quantum dot materials. Figure 4 In order to compare the fluorescence intensity of the materials after combining with atrazine under different experimental conditions during the preparation process, taking the addition of atrazine concentration of 500ng / L as an example, it was found that the fluorescence intensity ratio was optimal when the reaction temperature was 180℃ and the reaction time was 12h.

[0046] Example 2 Construction of fluorescent probe for atrazine pesticide

[0047] Figure 5 The fluorescence response diagram after adding different pesticides. Figure 6 It is a standard curve fitted according to the fluorescence response spectrum. Figure 6 It can be seen that the concentration range of atrazine detected by the established fluorescent probe is 20-1000 ng / L, and the corresponding linear regression equation is y=0.0085x+1.2827, and the linear regression coefficient R 2 R 2 =0.9883.

[0048] Example 3 Response time and stability study of the rapid detection method for atrazine

[0049] In a clean centrifuge tube, add 4 mL of the prepared carbon quantum dot material solution (10 -6 g / mL), 5 mL of sodium acetate buffer (pH = 6) and 300 μL of 200 ng / L atrazine standard solution, fixed the excitation wavelength at 380 nm, and tested its fluorescence intensity at 0, 2, 4, 6, 8, 10, and 12 min using a fluorescence spectrophotometer.

[0050] Figure 7 This is the result of investigating the interaction time between atrazine and the material. It can be seen that the fluorescence intensity of the material remains stable after 10 minutes after the addition of atrazine. Figure 8 The fluorescence intensity of atrazine combined with the material is compared at different pH values ​​when atrazine concentration is 500 ng / L. It can be seen that the fluorescence intensity ratio is at the best value when the pH is 6.

[0051] Example 4 Investigation of the Selectivity of Atrazine Detection

[0052] In order to reflect the selectivity of the fluorescent probe constructed by the present invention, this embodiment selects the effects of some common metal ions and other pesticides on the fluorescence intensity, and adds 4 mL of the prepared fluorescent material solution and 5 mL of sodium acetate buffer solution to each centrifuge tube. Then, imidacloprid, cypermethrin, chlorpyrifos, melamine, triadimenol, sulfonepyraclostrobin, Cu 2+ 、Fe 3+ , K + , heated at 40℃ for 10min, tested the fluorescence intensity, fixed the excitation wavelength at 380nm, recorded the fluorescence intensity at the emission wavelength of 490nm, and calculated F / F0.

[0053] Figure 9 This is a fluorescence response diagram of some common metal ions and other pesticides, where the horizontal axis represents the interfering substance and the vertical axis represents the ratio of the fluorescence intensity after adding the interfering substance to the fluorescence intensity without adding the interfering substance. It can be seen from the figure that some common ions and other pesticides have little effect on the atrazine pesticide, and the invention has a high selectivity for atrazine.

[0054] Comparative Example 1

[0055] This comparative example is the method in patent CN 109781685 A.

[0056] Compared with the invention described in CN 109781685 A, the present invention does not require enzymes as catalytic substrates, the pretreatment process is simple, the detection process is faster, and the requirements for rapid outdoor detection can be better met.

[0057] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A rapid detection method for atrazine based on carbon quantum dot fluorescent probe, characterized in that: The specific steps include: (1) Preparation and synthesis of carbon quantum dots: The carbon quantum dots are prepared using citric acid, o-phenylenediamine, ethanol and ultrapure water as raw materials through a high-temperature hydrothermal method. The specific steps include: firstly, fully dissolving citric acid and o-phenylenediamine in a mixed solution of ethanol and ultrapure water, then heating at 150-200°C in a high-temperature and high-pressure reactor for 6-16 hours, cooling to room temperature, and then removing large particle impurities and small molecular substances, and finally blowing with nitrogen and freeze-drying. The obtained solid powder is the carbon quantum dots; (2) Establish a linear standard curve: Take several centrifuge tubes, first add the carbon quantum dot solution prepared in step (1), then add different concentrations of atrazine solution, then add buffer solution and mix well, heat at 38-42 °C for 8-12 min, then fix the excitation wavelength at 320-420 nm to obtain the fluorescence intensity, and finally use the ratio of the fluorescence intensity before and after adding atrazine as the ordinate and the concentration of atrazine as the abscissa to establish a linear relationship, and calculate the corresponding regression equation; (3) Eliminate interference: Take the coexistence of atrazine and follow step (2); (4) Sample pretreatment; (5) Determination of atrazine content: Take the carbon quantum dots in step (1) and add buffer solution, then add the pretreatment solution obtained by sample pretreatment in step (4), and then heat at a constant temperature of 38-42°C for 8-12 minutes. Fix the excitation wavelength to 320-420 nm, the excitation slit to 5 nm, and the emission slit to 10 nm to obtain the fluorescence intensity. The fluorescence intensity after adding atrazine at an emission wavelength of 490 nm is compared with the fluorescence intensity before adding atrazine and substituted into the equation constructed in step (2) for calculation to obtain the atrazine content in the sample.

2. The atrazine rapid detection method according to claim 1, wherein In the step (1), the volume ratio of ethanol to ultrapure water is 1:(0.5-1.5), the dissolved concentration of citric acid in the mixed solution is 2-6 g / L, and the dissolved concentration of o-phenylenediamine in the mixed solution is 2-18 g / L.

3. The atrazine rapid detection method according to claim 2, wherein The ratio of citric acid to o-phenylenediamine in step (1) is 1:(1-3).

4. The atrazine rapid detection method according to claim 3, wherein The concentration of the carbon quantum dot solution in step (2) is 0.5-1.5×10 -6 g / mL, and the amount added to each centrifuge tube was 3-5 mL.

5. The atrazine rapid detection method according to claim 4, wherein The concentration of atrazine solution in step (2) is set to 0, 10, 20, 50, 80, 100, 150, 200, 300, 400, 500, 600, 800, 1000, and 1200 ng / L, and the amount added to each centrifuge tube is 280-320 μL.

6. The atrazine rapid detection method according to claim 5, wherein The buffer in step (2) is acetate buffer, with a pH value of 4-7, and the amount added is 4-6 mL.

7. The atrazine rapid detection method according to claim 6, wherein The coexisting substances of atrazine in step (3) are imidacloprid, chlorpyrifos, cypermethrin, melamine, triadimenol, sulfonepyraclostrobin, Cu 2+ 、Fe 3+ and K + Any one or more of .

8. Use of the atrazine rapid detection method according to any one of claims 1 to 7 in atrazine detection.

Images