CN114839245B - Carbon quantum dot modified electrode for detecting cyhalothrin and preparation method and application method thereof - Google Patents
Carbon quantum dot modified electrode for detecting cyhalothrin and preparation method and application method thereof Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
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- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/308—Electrodes, e.g. test electrodes; Half-cells at least partially made of carbon
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
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- G01N27/32—Calomel electrodes
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/38—Cleaning of electrodes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/416—Systems
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Abstract
The invention discloses a carbon quantum dot modified electrode for detecting cyhalothrin, a preparation method and an application method thereof, wherein the modified electrode is a carbon quantum dot modified glassy carbon electrode (CQDs/GCE), and the preparation method mainly comprises the following steps: (1) synthesizing Carbon Quantum Dots (CQDs) by a hydrothermal method; (2) And preparing CQDs into suspension, dripping the suspension on a cleaned Glassy Carbon Electrode (GCE), and then drying under an infrared lamp. The prepared modified electrode is applied to trace detection of cyhalothrin in an environmental water sample, and has the advantages of high detection sensitivity, good selectivity, simplicity, convenience, low cost, good stability and the like. The modified electrode prepared by the invention has been successfully applied to detecting the content of the cyhalothrin in the water sample in the living environment.
Description
Technical Field
The invention relates to a carbon quantum dot modified electrode, a preparation method and an application method thereof, in particular to a carbon quantum dot modified electrode for detecting cyhalothrin, a preparation method thereof and an application method for detecting cyhalothrin in an environmental water sample, and belongs to the field of electrochemical analysis and detection.
Background
The carbon quantum dots (Carbon Quantum Dots, CQDs) are novel zero-dimensional carbon nano materials, and are widely applied to the fields of improved biosensors, atomic imaging equipment, tiny light-emitting diodes and the like. Meanwhile, compared with metal quantum dots, CQDs have good biological safety, low environmental hazard and low manufacturing cost. In summary, the research of CQDs has received extensive attention in recent years. And the construction of electrochemical sensors using CQDs has also become a research hotspot.
The high-efficiency cyhalothrin, also known as cyhalothrin, is a pyrethroid pesticide and is widely used in the fields of pest control of crops such as cotton, vegetables, tobacco and the like and daily chemical sanitation. However, it has been reported in the literature that cyhalothrin has an effect on the human central nervous system and interferes with endocrine activity in humans. In recent years, due to the excessive use of cyhalothrin, a large amount of residual liquid flows into soil and environmental water, causing serious environmental pollution. Therefore, the development of a technology for efficiently detecting the cyhalothrin in water has important significance for detecting pesticide residues in the environment.
The current method for testing the cyhalothrin mainly comprises the following steps: gas chromatography, liquid chromatography, thin layer chromatography, and the like. However, these methods are costly to operate, complex in procedure, time consuming, not sensitive enough, and are not suitable for field detection. The novel electrochemical sensor is constructed for detecting the cyhalothrin, so that the advantages of high sensitivity, low cost and less time consumption in the electrochemical technology can be reflected.
Disclosure of Invention
The invention aims to: the first object of the invention is to provide a carbon quantum dot modified electrode for detecting cyhalothrin, which has high sensitivity, low cost and less time consumption; the second object of the invention is to provide a preparation method of the carbon quantum dot modified electrode for detecting cyhalothrin; the invention provides an application method of the carbon quantum dot modified electrode for detecting the concentration of cyhalothrin in a water body.
The technical scheme is as follows: the carbon quantum dot modified electrode for detecting the cyhalothrin is prepared by taking GCE as a carrier and CQDs as a functional material, and then dripping CQDs suspension on the surface of the GCE and drying under an infrared lamp.
The preparation method of the carbon quantum dot modified electrode for detecting cyhalothrin comprises the following steps of:
(1) Dissolving chitosan in acetic acid solution, calcining, cooling to room temperature, centrifuging, freeze-drying the centrifuged solution to obtain CQDs (BCQDs), taking out a proper amount of dried BCQDs, dispersing in deionized water, and performing ultrasonic treatment to obtain BCQDs suspension with uniform dispersion;
(2) Performing polishing treatment on GCE on chamois leather by using alumina polishing powder respectively, washing the GCE cleanly, placing the GCE in a K 3Fe(CN)6 solution for cyclic voltammetry scanning cleaning, performing ultrasonic treatment on the cleaned GCE by using absolute ethyl alcohol and deionized water respectively, and drying the GCE by using nitrogen for later use;
(3) And (3) taking BCQDs suspension drops, putting the suspension drops on the GCE treated in the step (2), and drying under an infrared lamp to obtain the carbon quantum dot modified electrode BCQDs/GCE.
Wherein in the step (1), the ratio of the mass of the chitosan to the volume of the 2wt% acetic acid solution is 1:8-1:12.
Wherein in the step (1), the temperature of the calcination reaction is 180-200 ℃, and the time of the calcination reaction is 6-10h.
In the step (2), the voltage during cyclic voltammetry scanning cleaning is-0.2-0.8V, the standard for judging cleaning is that the oxidation-reduction peak potential difference value is less than 80mV, and the ultrasonic treatment time is 1min.
Wherein, in the step (3), the volume of BCQDs suspension dropped on the GCE treated in the step (2) is 3-7. Mu.L.
The application method of the carbon quantum dot modified electrode for detecting the concentration of the cyhalothrin in the water body comprises the following steps of:
(1) Preparing cyhalothrin standard solutions with different concentrations;
(2) The carbon quantum dot modified electrode is used as a working electrode, a platinum wire is used as a counter electrode, a calomel electrode is used as a reference electrode, the reduction peak current values of the different-concentration cyhalothrin standard solutions prepared in the step (1) are measured through a DPV (differential pulse voltammetry), the reduction peak current values corresponding to the different-concentration cyhalothrin standard solutions are recorded, and a standard curve of the reduction peak current values and the cyhalothrin concentration is established;
(3) Detecting the water sample according to the method of the step (2), and bringing the measured reduction peak current value of the water sample into the standard curve prepared in the step (2) to obtain the concentration of the cyhalothrin in the water sample;
Wherein, in the step (1), the different concentrations are 20nM, 80nM, 100nM, 120nM, 150nM and 200nM.
In the step (2), the standard curve of the reduction peak current value and the concentration of the cyhalothrin is I P＝0.0031C+2.2789;R2 = 0.9883.
In the step (3), the water sample is an environmental water sample.
The beneficial effects are that: compared with the prior art, the invention has the following advantages:
(1) The invention adopts CQDs modified GCE as an electrochemical sensor for quantitative detection of cyhalothrin for the first time.
(2) The modified electrode prepared by the invention has higher selectivity and sensitivity to the cyhalothrin, the linear range of detection concentration is 20-200nM, and the detection limit is 8.9nM. Compared with other detection processes, the detection method provided by the invention has the advantages of less time consumption, high detection sensitivity, good selectivity, simplicity, convenience, low cost, good stability and the like.
Drawings
FIG. 1 is a TEM image of BCQDs;
FIG. 2 is a cyclic voltammogram of different working electrodes BCQDs/GCE, GCQDs/GCE, bare GCE (bare glassy carbon electrode) in a 1mM K 3Fe(CN)6 solution;
FIG. 3 is a Zeta potential diagram of BCQDs and GCQDs;
FIG. 4 is a plot nyquist plot of the different working electrodes BCQDs/GCE, GCQDs/GCE, bare GCE in a 0.1M KCl solution of 10mM [ Fe (CN) 6 3-/4- ] (1:1);
FIG. 5 is a schematic illustration of a stepwise process of CQDs/GCE for the determination of cyhalothrin;
FIG. 6 is a graph of DPV obtained by testing 10nM of cyhalothrin in 0.02M B-R buffer solution at pH=2 for the different working electrodes Bare GCE, BCQDs/GCE, GCQDs/GCE prepared in example three and comparative example one;
FIG. 7 is a graph of DPV of BCQDs/GCE prepared in example 3 at various concentrations of cyhalothrin;
FIG. 8 is a graph of the concentration (C) between peak current (I p, μA) and cyhalothrin over 20-200 nM.
Detailed Description
The technical scheme of the invention is further described below with reference to the accompanying drawings.
Example 1 BCQDs/preparation of GCE
1. BCQDs Synthesis
2G of chitosan was dissolved in 18mL-2wt% acetic acid solution (mass: volume=1:9), then placed in a polytetrafluoroethylene reaction kettle, and reacted in a muffle furnace at 180℃for 10 hours. After the reaction was completed, the solution was cooled to room temperature, and the obtained blackish brown solution was centrifuged at 11000rpm for 15 minutes to remove unreacted impurities, and the average size of the upper brown solution was about 5 nm. The deposited nanoparticles were larger in diameter, about 30-40nm, and after lyophilization of the upper brown solution for 12 hours, about 70mg of pure Black CQDs, namely Black CQDs (BCQDs), were obtained, insoluble in water. 2mg of the prepared BCQDs was dispersed in 10mL of deionized water and sonicated for 2 hours to give a uniformly dispersed 0.2mg/mL BCQDs suspension. And stored at 4 ℃ for use each time as a modified electrode.
2. Cleaning glassy carbon electrode
And (3) polishing GCE on chamois leather by using alumina polishing powder with the particle size of 0.3 mu m and alumina polishing powder with the particle size of 0.05 mu m respectively, washing the GCE, placing the GCE in a 1mM K 3Fe(CN)6 solution, and carrying out cyclic voltammetry scanning within the potential range of-0.2-0.8V to obtain a redox peak potential difference value of less than 80mV, namely the GCE is clean. And then, performing ultrasonic treatment on the GCE in absolute ethyl alcohol and deionized water for 1min, and drying by using nitrogen to obtain a bare glassy carbon electrode (Bare GCE) for standby.
3. Modified electrode
Mu.L of the prepared BCQDs suspension (0.2 mg/mL) was dropped onto Bare GCE and dried under an infrared lamp to successfully prepare the electrode BCQDs/GCE.
The result of electron microscope scanning analysis of BCQDs prepared in this example is shown in fig. 1, and fig. 1 is a TEM of BCQDs. Wherein, a is a TEM (transmission electron microscope) of BCQDs, and b is a HRTEM (high resolution transmission electron microscope) of BCQDs. As is clear from FIG. 1, the carbon dots have good monodispersity and the particle diameter is about 3-5 nm.
Example 2
1. BCQDs Synthesis
2G of chitosan was dissolved in 20mL-2wt% acetic acid solution (mass: volume=1:10), then placed in a polytetrafluoroethylene reaction kettle, and reacted in a muffle furnace at 190℃for 8 hours. After the reaction was completed, the solution was cooled to room temperature, and the obtained blackish brown solution was centrifuged at 11000rpm for 15 minutes to remove unreacted impurities, and the average size of the upper brown solution was about 5 nm. The diameter of the deposited nano particles is larger and is about 30-40nm, and after the upper brown solution is freeze-dried for 12 hours, about 70mg of pure black BCQDs is obtained. 2mg of the prepared BCQDs was dispersed in 10mL of deionized water and sonicated for 2 hours to give a uniformly dispersed 0.2mg/mL BCQDs suspension. And stored at 4 ℃ for use each time as a modified electrode.
2. Cleaning glassy carbon electrode
And (3) polishing GCE on chamois leather by using alumina polishing powder with the particle size of 0.3 mu m and alumina polishing powder with the particle size of 0.05 mu m respectively, washing the GCE, placing the GCE in a 1mM K 3Fe(CN)6 solution, and carrying out cyclic voltammetry scanning within the potential range of-0.2-0.8V to obtain a redox peak potential difference value of less than 80mV, namely the GCE is clean. And then, performing ultrasonic treatment on the GCE in absolute ethyl alcohol and deionized water for 1min, and drying by using nitrogen to obtain a bare glassy carbon electrode (Bare GCE) for standby.
3. Modified electrode
Mu.L of the prepared BCQDs suspension (0.2 mg/mL) was dropped onto Bare GCE and dried under an infrared lamp to successfully prepare the electrode BCQDs/GCE.
Example 3
1. BCQDs Synthesis
2G of chitosan was dissolved in 24mL-2wt% acetic acid solution (mass: volume=1:10), then placed in a polytetrafluoroethylene reaction kettle, and reacted in a muffle furnace at 200℃for 6 hours. After the reaction was completed, the solution was cooled to room temperature, and the obtained blackish brown solution was centrifuged at 11000rpm for 15 minutes to remove unreacted impurities, and the average size of the upper brown solution was about 5 nm. The diameter of the deposited nano particles is larger and is about 30-40nm, and after the upper brown solution is freeze-dried for 12 hours, about 70mg of pure black BCQDs is obtained. 2mg of the prepared BCQDs was dispersed in 10mL of deionized water and sonicated for 2 hours to give a uniformly dispersed 0.2mg/mL BCQDs suspension. And stored at 4 ℃ for use each time as a modified electrode.
2. Cleaning glassy carbon electrode
And (3) polishing GCE on chamois leather by using alumina polishing powder with the particle size of 0.3 mu m and alumina polishing powder with the particle size of 0.05 mu m respectively, washing the GCE, placing the GCE in a 1mM K 3Fe(CN)6 solution, and carrying out cyclic voltammetry scanning within the potential range of-0.2-0.8V to obtain a redox peak potential difference value of less than 80mV, namely the GCE is clean. And then, performing ultrasonic treatment on the GCE in absolute ethyl alcohol and deionized water for 1min, and drying by using nitrogen to obtain a bare glassy carbon electrode (Bare GCE) for standby.
3. Modified electrode
Mu.L of the prepared BCQDs suspension (0.2 mg/mL) was dropped onto Bare GCE and dried under an infrared lamp to successfully prepare the electrode BCQDs/GCE.
Preparation of comparative example 1GCQDs/GCE
1.6G sucrose was dissolved in 40mL deionized water and sonicated for 2min to allow complete dissolution. Then placing the mixture in a polytetrafluoroethylene reaction kettle, and placing the mixture in a muffle furnace for reaction at 180 ℃ for 6 hours. After the reaction is finished, cooling to room temperature, and finally freeze-drying for 24 hours to obtain the green CQDs (GREEN CQDS (GCQDs, which has better water solubility).
2Mg of the prepared GCQDs was dispersed in 10mL of deionized water and sonicated for 2 hours to give a uniformly dispersed 0.2mg/mL GCQDs suspension. And stored at 4 ℃ for use each time as a modified electrode.
The procedure for cleaning the glassy carbon electrode and modifying the electrode was the same as in example 1, and finally an electrode GCQDs/GCE was obtained, which was good in water solubility.
Example 4
The results of electrochemical performance tests of Bare GCE, BCQDs/GCE obtained in example 1 and GCQDs/GCE obtained in comparative example 1 are shown in FIG. 2. FIG. 2 is a cyclic voltammogram of different working electrodes BCQDs/GCE, GCQDs/GCE, bare GCE in 1mM K 3Fe(CN)6 solution. As can be seen from fig. 2, the redox peak current of the electrode after modification of CQDs was significantly reduced compared to the bare electrode, probably because BCQDs and GCQDs were both negatively charged, preventing Fe (CN) 6 3-/4- from being transferred to the electrode surface.
The BCQDs obtained in example 1 and GCQDs obtained in comparative example 1 were subjected to zeta potential test, and the results are shown in FIG. 3. FIG. 3 is a Zeta potential plot of BCQDs and GCQDs, with BCQDs charged at-33.4.+ -. 0.212mV and GCQDs charged at-31.6.+ -. 0.707mV, as seen in FIG. 3. The negative charge value of the two is not very different, and the absolute value of the charge of BCQDs is slightly larger. The reason for the reduction of the redox peak current after the electrode is modified by CQDs in FIG. 2 is also well illustrated.
Impedance analysis was performed on Bare GCE, BCQDs/GCE obtained in example 1 and GCQDs/GCE obtained in comparative example 1, and the results are shown in FIG. 4. FIG. 4 is a plot nyquist plot of the different working electrodes BCQDs/GCE, GCQDs/GCE, bare GCE in a 0.1M KCl solution of 10mM [ Fe (CN) 6 3-/4- ] (1:1). As seen from fig. 4, the three curves are all composed of a semicircle and an inclined straight line, the semicircle represents electrochemical control, the straight line part is a straight line inclined in a low-frequency region and is caused by the wobbe impedance, R ct (charge transfer resistance) of the black carbon quantum dot is 211 Ω, the green carbon quantum dot is 360 Ω, the bare glassy carbon electrode is 394 Ω, and after the carbon quantum dot is modified, the impedance value is obviously reduced because the carbon quantum dot has good electrical activity, and the electron transfer rate between [ Fe (CN) 6 3-/4- ] and the electrode surface is improved.
Example 5 the carbon Quantum dot modified electrode of the invention detects the concentration of cyhalothrin in Water
(1) Preparing different concentrations of cyhalothrin standard solution
The standard solution of cyhalothrin (10 nm, ph=2) was prepared by taking 10 μl from a 10 -5 M sample bottle of cyhalothrin with a pipette into a 10mL volumetric flask and sequentially adding 5mL B-R (0.04M, ph=2), 1mL tetrabutylammonium chloride (TBAC 0.05M) and 3mL methanol, and finally adding an appropriate amount of deionized water to a volume of 10mL and transferring to an electrochemical cell. The concentration of the test solution, cyhalothrin, is 10nM, and a large number of experiments show that the cyhalothrin has the greatest solubility and the best test effect when the volume ratio of water to methanol is 7:3, so the solution is prepared. Prior to voltammetric testing, the solution was stirred with a magnetic stirrer to mix well and deaerated for 5min by bubbling nitrogen gas at a flow rate of 50 mL/min.
Standard test solutions of 20nM,80nM,100nM,120nM,150nM,200nM cyhalothrin were prepared: the preparation procedure was the same as that described above for the preparation of 10nM standard solution of cyhalothrin (pH=2), except that 20. Mu.L, 80. Mu.L, 100. Mu.L, 120. Mu.L, 150. Mu.L, 200. Mu.L of each of the 10mL solutions of different concentrations were added by pipetting from 10 -5 M cyhalothrin sample bottles.
(2) The carbon quantum dot modified electrode CQDs/GCE prepared in example 3 is used as a working electrode, a platinum wire is used as a counter electrode, and a calomel electrode is used as a reference electrode. Measuring different concentrations of the cyhalothrin standard solution by using a DPV (differential pulse voltammetry), recording reduction peak current values corresponding to the different concentrations of the cyhalothrin standard solution, and establishing a standard curve of the reduction peak current values and the cyhalothrin concentration; the stepwise procedure for the determination of cyhalothrin by CQDs/GCE is shown in FIG. 5.
(3) Detecting the water sample according to the method of the step (2), and bringing the measured reduction peak current value of the water sample into the standard curve prepared in the step (2) to obtain the concentration of the cyhalothrin in the water sample;
DPV curve analysis was performed on Bare GCE, BCQDs/GCE obtained in example 3 and GCQDs/GCE obtained in comparative example 1, and the results are shown in FIG. 6. FIG. 6 is a graph of DPV obtained by detection of 10nM cyhalothrin in 0.02M B-R buffer solution at pH=2 for the different working electrodes Bare GCE, BCQDs/GCE, GCQDs/GCE prepared in example 3 and comparative example 1. As can be seen from FIG. 6, the BCQDs modified glassy carbon electrode has a significantly better test effect, and the peak current is larger, about-4.8X10 -6 A, and the increase of the peak current indicates that the CQDs material has catalytic reduction effect on the cyhalothrin. CQDs have good conductivity and high electron transfer rate, and can promote the transfer between ions and electrons.
The electrochemical reaction mechanism diagram of the BCQDs/GCE electrode surface cyhalothrin is as follows:
the cyhalothrin has electrochemical reduction reaction on the electrode surface and the carbon-carbon double bond is reduced into carbon-carbon single bond.
FIG. 7 is a graph of DPV of BCQDs/GCE prepared in example 3 at various concentrations of cyhalothrin (curves a-f with increasing peak current correspond to concentrations of 20nM,80nM,100nM,120nM,150nM,200nM, in order). As shown in fig. 7, as the concentration of cyhalothrin increases, the peak current of DPV also increases, and a linear fit of the peak current of DPV to cyhalothrin is made. FIG. 8 is a graph of the linear relationship between peak current (I p, μA) and concentration (C) of cyhalothrin over 20-200nM, linear regression equation: i P＝0.0031C+2.2789;R2 = 0.9883, limit of detection (LOD) of 8.9nM.
Example 6
The concentrations of cyhalothrin in lake and tap water samples collected from the university of Nanjing, mesona, inc. were measured using BCQDs/GCE prepared in example 3.
(1) Preparing an actual water sample solution: lake water and tap water collected from university of south Beijing was filtered separately using a 0.45 μm filter membrane to avoid suspended substances. And the filtered water sample was stored at 4 ℃ until further analysis. 5mL of water sample was added to 5mL (0.04M) of pH 2B-R buffer solution, and various concentrations of cyhalothrin were added to the solution for measurement.
The actual water samples obtained in step (1), i.e., lake water and tap water, were each measured according to step (2) in example 5, and the results of 5 parallel experiments were shown in table 1.
TABLE 1 use of BCQDs/GCE prepared in example 3 for detection of cyhalothrin in actual lake and tap water samples
As can be seen from Table 1, the recovery rate of the actual water sample is 91.35% -101.72%, and the accuracy is high. The relative standard deviation is between 0.61% and 2.55%, which shows that the chemically modified electrode obtained by the invention has good precision, effectiveness and reliability and great potential in practical application.
Claims (8)
1. The application method of the carbon quantum dot modified electrode for quantitatively detecting the concentration of the cyhalothrin is characterized by comprising the following steps of:
(1) Preparing cyhalothrin standard solutions with different concentrations;
(2) Measuring reduction peak current values of the different-concentration cyhalothrin standard solutions prepared in the step (1) by using a carbon quantum dot modified electrode as a working electrode, a platinum wire as a counter electrode and a calomel electrode as a reference electrode through DPV (differential pulse voltammetry), recording the reduction peak current values corresponding to the different-concentration cyhalothrin standard solutions, and establishing a standard curve of the reduction peak current values and the cyhalothrin concentrations;
(3) Detecting the water sample according to the method of the step (2), and bringing the measured reduction peak current value of the water sample into the standard curve prepared in the step (2) to obtain the concentration of the cyhalothrin in the water sample;
the carbon quantum dot modified electrode is prepared by using GCE as a carrier and CQDs as a functional material and drying CQDs under an infrared lamp after modifying the surface of the GCE.
2. The application method according to claim 1, wherein in the step (2), the preparation method of the carbon quantum dot modified electrode comprises the following steps:
(A) Dissolving chitosan in acetic acid solution, calcining, cooling to room temperature, centrifugally separating, freeze-drying the centrifugally separated solution to obtain black CQDs, taking out a proper amount of dried black CQDs, dispersing in deionized water, and performing ultrasonic treatment to obtain uniformly dispersed black CQDs suspension;
(B) Performing polishing treatment on GCE on chamois leather by using alumina polishing powder respectively, washing the GCE cleanly, placing the GCE in a K 3Fe(CN)6 solution for cyclic voltammetry scanning cleaning, performing ultrasonic treatment on the cleaned GCE by using absolute ethyl alcohol and deionized water respectively, and drying the GCE by using nitrogen for later use;
(C) And (3) taking black CQDs suspension liquid drops on the GCE treated in the step (B), and drying under an infrared lamp to obtain the carbon quantum dot modified electrode black CQDs/GCE.
3. The method of claim 2, wherein in the step (a), the volume ratio of the chitosan mass to the 2wt% acetic acid solution is 1:8-1:12, the temperature of the calcination reaction is 180-200 ℃, and the time of the calcination reaction is 6-10 hours.
4. The method of claim 2, wherein in step (B), the voltage during the cyclic voltammetry sweep is-0.2-0.8V, and the standard for cleaning is that the difference in oxidation-reduction peak potential is less than 80: 80 mV.
5. The method of claim 2, wherein in step (C), the volume of the black CQDs suspension dropped onto the GCE treated in step (B) is 3-7 μl.
6. The method of claim 1, wherein in step (1), the different concentrations are 20 nM, 80 nM, 100 nM, 120 nM, 150 nM, 200 nM.
7. The method of claim 1, wherein in step (2), the standard curve of the reduction peak current value and the concentration of cyhalothrin is I P =0.0031c+2.2789.
8. The method of claim 1, wherein in step (3), the water sample is an environmental water sample.
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