Magnetic composites and methods of making and using, electrochemical sensors and devices

Abstract

The application discloses a kind of magnetic composite material and preparation method and application, electrochemical sensor and device;Among them, the disclosed magnetic composite material has the core-shell structure of CoFe2O4@ZIF-67, CoFe2O4 is magnetic core body, and ZIF-67 is shell layer.Compared with existing electrode modification material, the CoFe2O4@ZIF-67 magnetic composite material disclosed in the application has a larger specific surface area, which can effectively increase its contact area with electrolyte and provide more active centers, thereby facilitating the adsorption of lead ions and better improving the electrochemical performance, so that the electrochemical sensor constructed by it has high detection sensitivity, strong anti-interference ability, and the detection of electrochemical sensor by anions, cations and other impurities in the solution to be measured will not cause interference basically, and can specifically detect lead ions in aqueous solution.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical detection, in particular to a magnetic composite material and a preparation method and application thereof, an electrochemical sensor and a device. BACKGROUND

[0002] There are many harmful heavy metals in industrial wastewater, mainly including pollutants such as mercury, cadmium, chromium and lead with high biological toxicity; these heavy metals can enter the human body through the gastrointestinal tract, especially lead can be directly absorbed through the skin, and after the heavy metals enter the human body, they can destroy and affect the function of cells, thereby interfering with the central nervous system, causing mental disorders, destroying the balance of plasma substances, and possibly damaging important organs such as the lungs, liver and kidneys, aggravating the underlying disease condition, and cannot be degraded in the body.

[0003] At present, the traditional detection methods for lead ions include atomic absorption spectrometry, inductively coupled plasma mass spectrometry, X-ray fluorescence spectrometry, etc., however, these methods are expensive in equipment, complex in operation, time-consuming, and cannot be monitored online. Therefore, developing a rapid, accurate, sensitive and simple method for detecting low-concentration lead ions is an important research topic in recent years.

[0004] Compared with the above-mentioned traditional detection methods, the electrochemical analysis method has the advantages of simple equipment, easy automation, fast response speed, low cost, good stability, strong selectivity and high sensitivity; among them, the key to realizing high sensitivity and low detection limit detection lies in the modification material of the working electrode.

[0005] However, the existing carbon nanotubes, graphene, nano metals and metal oxides and other materials applied to electrode modification have problems such as poor dispersibility, easy aggregation after modification, poor acid-base stability, poor conductivity and the like; therefore, it is necessary to develop a new type of modified electrode material to improve the sensitivity and stability of electrochemical detection of lead. SUMMARY

[0006] The present application discloses a magnetic composite material and a preparation method and application thereof, an electrochemical sensor and a manufacturing method and device thereof, to solve the problems of poor dispersibility, easy aggregation after modification, poor acid-base stability and poor conductivity of the existing carbon nanotubes, graphene, nano metals and metal oxides and other materials applied to electrode modification.

[0007] In order to solve the above problems, the technical scheme adopted by the present application is as follows:

[0008] In a first aspect, the present application provides a magnetic composite material, which has a core-shell structure of CoFe2O4@ZIF-67; wherein CoFe2O4 is a magnetic core, and ZIF-67 is a shell layer.

[0009] In a second aspect, the present application provides a preparation method of the magnetic composite material, comprising the following steps:

[0010] CoFe2O4 and dimethyl imidazole are dispersed in a methanol solution to form solution A; Co(NO3)2·6H2O is added to the methanol solution to form solution B; then, under stirring, the solution B is added dropwise to the solution A to form reaction liquid C after uniform mixing;

[0011] The reaction liquid C is transferred to a reaction kettle for hydrothermal reaction, and after the reaction is completed, the reaction kettle is naturally cooled to room temperature, and the precipitate is collected by magnetic separation; then, the precipitate is washed with ethanol, and dried to prepare the CoFe2O4@ZIF-67 composite material.

[0012] In a third aspect, the present application provides the above-mentioned magnetic composite material for detecting lead ions.

[0013] Optionally, the magnetic composite material is used as an additive for detecting lead ions, comprising the following steps: the magnetic composite material is added to a to-be-tested liquid for mixing, after the magnetic composite material fully adsorbs lead ions in the to-be-tested liquid, an electrochemical sensor is turned on, a magnetic working electrode of the electrochemical sensor adsorbs and fixes the magnetic composite material adsorbing lead ions on the surface of the magnetic working electrode through magnetic force, and lead ion concentration detection is completed.

[0014] Optionally, the magnetic composite material is used as an electrode modification material for detecting lead ions, comprising the following steps: the magnetic composite material is modified on a magnetic working electrode of an electrochemical sensor, and then the electrochemical sensor is used to complete lead ion concentration detection of a to-be-tested liquid.

[0015] In a fourth aspect, the present application provides an electrochemical sensor for detecting lead ions, comprising a working electrode, and a substrate of the working electrode is modified with the above-mentioned magnetic composite material; the substrate is a magnetic glassy carbon electrode, the magnetic composite material forms a CoFe2O4@ZIF-67 structure layer on a working surface of the substrate; the magnetic glassy carbon electrode and the CoFe2O4@ZIF-67 structure layer form a CoFe2O4@ZIF-67 / GCE working electrode.

[0016] Optionally, an outer surface of the CoFe2O4@ZIF-67 structure layer is coated with a Nafion film layer to form a CoFe2O4@ZIF-67 / Nafion / GCE working electrode.

[0017] In a fifth aspect, the application provides a method for manufacturing the electrochemical sensor, which comprises a magnetic composite modification step: dispersing the powder of the magnetic composite described above in deionized water to form a suspension, and then dropping the suspension on the surface of a polished magnetic glassy carbon electrode to form a CoFe2O4@ZIF-67 / GCE working electrode after drying.

[0018] Optionally, the method for manufacturing the electrochemical sensor further comprises a protective material modification step: dropping a Nafion film solution on the surface of the CoFe2O4@ZIF-67 / GCE working electrode to form a CoFe2O4@ZIF-67 / Nafion / GCE working electrode after drying.

[0019] In a sixth aspect, the application provides an electrochemical device for detecting lead ions, which comprises a housing, a micro electrochemical workstation, a liquid feeding device, and the electrochemical sensor described above; the housing is provided with a detection chamber, a mounting cavity, a liquid inlet, and a material inlet; the liquid feeding device is fixedly installed in the mounting cavity, and the liquid inlet end of the liquid feeding device is in communication with the liquid inlet, and the liquid outlet end of the liquid feeding device is in communication with the detection chamber; the micro electrochemical workstation is arranged in the housing and connected with the electrochemical sensor; the electrochemical sensor further comprises a reference electrode and a counter electrode, and the working electrode, the reference electrode, and the counter electrode are arranged in the detection chamber; the material inlet is in communication with the detection chamber, and the material inlet has an open state and a closed state.

[0020] The technical solution adopted by the application can achieve the following beneficial effects:

[0021] In the magnetic composite material, the preparation method and application, the electrochemical sensor and the device disclosed by the application, the magnetic composite material has a core-shell structure of CoFe2O4@ZIF-67; wherein the magnetic core CoFe2O4 is in a rough-surface spherical shape, and the rough surface is composed of regular cubic structures and irregular small particles, thereby effectively increasing the specific surface area of the core to provide sufficient coating sites for ZIF-67, so that ZIF-67 densely wraps the surface of the core in the form of small particles, and the shape of ZIF-67 is a regular dodecahedron. Such structural features avoid the agglomeration problem of ZIF-67 and present an ideal core-shell structure. Therefore, compared with existing electrode modification materials, the magnetic composite material disclosed by the application has a larger specific surface area, can effectively increase the contact area with the electrolyte, and provide more active centers, thereby being beneficial to the adsorption of lead ions and better improving the electrochemical performance, so that the electrochemical sensor constructed by the magnetic composite material has high detection sensitivity and strong anti-interference ability, and the detection of the electrochemical sensor by anions, cations and other impurities in the to-be-measured solution basically does not cause interference, and the electrochemical sensor can specifically detect lead ions in an aqueous solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0023] Figure 1 (a) to (d) are microscopic surface morphologies of the magnetic composite material disclosed in the present invention;

[0024] Figure 2 CV graphs of different modified electrodes;

[0025] Figure 3 DPV curves of different modified electrodes;

[0026] Figure 4 (a) to (b) are the test results of stability (a) and reproducibility (b) of the electrochemical sensor disclosed in the present invention;

[0027] Figure 5 The anti-interference performance test structure of the electrochemical sensor disclosed in the present invention;

[0028] Figure 6 A schematic structural diagram of the electrochemical device disclosed in the present invention;

[0029] Figure 7 is the test result and linear equation of the experimental sample;

[0030] Description of reference numerals:

[0031] 100-shell, 101-liquid inlet, 102-detection chamber, 110-filtration structure, 120-micro peristaltic pump, 121-one-way valve, 130-working electrode, 140-reference electrode, 150-counter electrode, 160-micro electrochemical workstation. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and corresponding drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] The technical solutions disclosed in various embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0034] Example 1

[0035] Preparation and characterization of magnetic composite CoFe2O4@ZIF-67

[0036] 0.2 g of CoFe2O4 was dispersed in 7 g of dimethyl imidazole in 50 mL of methanol solution to prepare solution A.

[0037] 3 g of Co(NO3)2·6H2O was added to 50 mL of methanol solution to prepare solution B; then, the A solution was stirred, and the B solution was slowly and evenly added dropwise into the A solution. After the dropwise addition was completed, the stirring was continued for 1 h to prepare a mixed and uniform reaction solution C.

[0038] The mixed and uniform reaction solution C was transferred to a 100 mL polytetrafluoroethylene-lined reaction kettle. Through a hydrothermal reaction, the reaction was carried out at 75℃ for 135 min. After the reaction was completed, the reaction kettle was naturally cooled to room temperature. The precipitated product after the reaction was collected by magnetic separation, and the precipitate was washed with ethanol and dried at 60℃ for 6 h to prepare the CoFe2O4@ZIF-67 magnetic composite material. CoFe2O4 (cobalt tetraoxy ferrate) is the magnetic core, and ZIF-67 (zeolite imidazole framework-67) is the shell layer.

[0039] The prepared CoFe2O4@ZIF-67 magnetic composite material was characterized by scanning electron microscopy. As shown in Figure 1 , the micro surface morphology and particle size distribution of the magnetic core CoFe2O4 and the magnetic composite material CoFe2O4@ZIF-67 with core-shell structure were known.

[0040] As shown in Figure 1 (a), the magnetic core CoFe2O4 was a rough surface spherical shape. Figure 1 As shown in Figure 1 (b), the rough surface of the magnetic core CoFe2O4 was composed of regular cubic structures and irregular small particles, which could effectively increase the specific surface area of the core and provide sufficient coating sites for ZIF-67. Figure 1 As shown in (c), ZIF-67 was densely wrapped in the form of small particles on the surface of the core layer.

[0041] As shown in (d), the shape of ZIF-67 was a regular dodecahedron, which was distributed on the surface of the magnetic core CoFe2O4. Such structural characteristics avoided the agglomeration problem of ZIF-67 and presented an ideal core-shell structure.

[0041] Therefore, the magnetic composite material disclosed in the embodiment can effectively increase the specific surface area of the material through the core-shell structure of CoFe2O4@ZIF-67, thereby increasing the contact area with the electrolyte and providing more active centers, which is conducive to the adsorption of lead ions and improves the electrochemical performance. At the same time, the preparation method disclosed in the embodiment has the advantage of simple operation.

[0042] Example 2

[0043] The preparation of a working electrode for an electrochemical sensor, comprising the following steps:

[0044] A glassy carbon electrode (GCE for short) with magnetism is polished smooth on a chamois leather with 1.0 μm, 0.3 μm and 0.05 μm polishing powder in sequence, and then cleaned alternately with distilled water and anhydrous ethanol by ultrasonic cleaning; then, the washed glassy carbon electrode is placed in a 0.5 mol / L H2SO4 solution for activation by cyclic voltammetry (CV); the activated glassy carbon electrode is placed in a 5 mmol / L K3[Fe(CN)6] solution (containing KCl, concentration 0.1 mol / L) for CV testing, and the difference between the oxidation and reduction peak potentials is not more than 80 mV in the voltage range of -0.2~0.8 V, which is a treated glassy carbon electrode; it should be noted that the glassy carbon electrode with magnetism is an electrode of existing structure, also known as a magnetic glassy carbon electrode, which usually has a magnet or other magnetic structure in the interior or end of the glassy carbon electrode.

[0045] The CoFe2O4@ZIF-67 magnetic composite material prepared in Example 1 is ground into powder and dispersed in deionized water to form a suspension, which is then drop-coated on the surface of the treated magnetic glassy carbon electrode and dried under an infrared lamp, thereby forming a CoFe2O4@ZIF-67 / GCE working electrode.

[0046] Preferably, in order to prevent the CoFe2O4@ZIF-67 adsorbed and fixed on the working surface of the magnetic glassy carbon electrode from falling off, a Nafion (perfluorosulfonic acid resin) film can also be coated on the surface of the CoFe2O4@ZIF-67 / GCE working electrode, so that the CoFe2O4@ZIF-67 material adsorbed and fixed on the electrode surface can be well protected and reinforced by the coated Nafion film, which is conducive to prolonging the service life of the CoFe2O4@ZIF-67 / GCE working electrode.

[0047] The specific steps are as follows: a Nafion film solution (mass fraction 5%) is drop-coated on the surface of the CoFe2O4@ZIF-67 / GCE working electrode and dried under an infrared lamp, thereby forming a CoFe2O4@ZIF-67 / Nafion / GCE working electrode; it should be noted that the Nafion film solution is a product available on the market, which can be directly purchased, and this embodiment will not be described in detail.

[0048] Example 3

[0049] Electrochemical performance test

[0050] The electrochemical performance test is evaluated by the CHI660E electrochemical workstation connected externally; wherein, the CoFe2O4@ZIF-67 / GCE prepared in Example 2 is taken as the working electrode, Ag / AgCl is taken as the reference electrode, and the platinum wire is taken as the counter electrode, and the three electrodes are respectively connected with the three electrode connecting terminals of the CHI660E electrochemical workstation, and the CV test and the differential pulse voltammetry (DPV) test are carried out.

[0051] The CV test is completed in the electrolyte of 5mmol / L K3[Fe(CN)6] solution (containing KCl, the concentration is 0.1mol / L), the voltage range is-0.2~0.8V, and the scanning speed is 50mV / s; the differential pulse voltammetry (DPV) test is completed in the electrolyte containing Pb 2+ , the test potential interval is-0.9 to-0.1V, the amplitude is 50mV, and the pulse width is 0.2s; all the experimental operations are carried out at room temperature. At the same time, the CV test and the DPV test are used to carry out the electrochemical performance comparative study on different modified electrodes: Bare / GCE, ZIF-67 / GCE, CoFe2O4 / GCE and CoFe2O4@ZIF-67 / GCE.

[0052] As shown in Figure 2 , the CV test curves of various electrodes are shown, and the test results show that compared with the bare electrode Bare / GCE, the oxidation-reduction peaks of ZIF-67 / GCE, CoFe2O4 / GCE and CoFe2O4@ZIF-67 / GCE are increased; and according to the larger oxidation-reduction peak area and the smaller oxidation-reduction potential difference, the conductivity of the electrochemical surface is known, that is, the conductivity of CoFe2O4 / GCE is the best, the conductivity of CoFe2O4@ZIF-67 / GCE is better than that of ZIF-67 / GCE, and is close to the conductivity of CoFe2O4 / GCE, and the conductivity of Bare / GCE is the worst; in addition, the peak value ratio of the oxidation peak current and the reduction peak current of CoFe2O4@ZIF-67 / GCE is also close to 1, which shows that it also has good electron transfer reversibility.

[0053] As shown in Figure 3 , the DPV test curves of various electrodes are shown, and the test results show that the current response signal of CoFe2O4@ZIF-67 / GCE is significantly improved compared with Bare / GCE, CoFe2O4 / GCE and ZIF-67 / GCE, because the functional groups such as -COOH and -OH on the surface of CoFe2O4@ZIF-67 can effectively adsorb Pb 2+ , and the contact surface of the composite material is increased, which provides more adsorption active sites, and can effectively accumulate Pb2+ , making more Pb 2+ Deposited on the electrode surface, thereby enhancing the electrochemical response performance.

[0054] At the same time, the DPV test also added a comparative study of the electrode performance of CoFe2O4@ZIF-67 / Nafion / GCE. Figure 3 It can be seen from the test curve that the current response signal of CoFe2O4@ZIF-67 / Nafion / GCE is better than that of CoFe2O4@ZIF-67 / GCE.

[0055] Example 4

[0056] Stability and reproducibility testing

[0057] CoFe2O4@ZIF-67 / Nafion / GCE was prepared in the presence of 1×10 -5 mol / L of Pb 2+ DPV tests were conducted seven times a week in the electrolyte (0.1 mol / L ABS buffer, pH = 4.5). The test results are as follows Figure 4 As shown in (a) and (b).

[0058] Among them, according to Figure 4 (a) It can be seen that within one week, Pb 2+ The peak current gradually decreased, which may be because there was a small amount of material loss during repeated experiments and storage of the electrode, so the peak current showed a downward trend, but its current response remained above 93.1% of the initial current, and the current response after one week still maintained 91.10% of its initial current, which shows that CoFe2O4@ZIF-67 / Nafion / GCE has good stability; according to Figure 4 (b) It can be seen that the seven measurement results of CoFe2O4@ZIF-67 / Nafion / GCE are basically similar, which shows that the electrode modified with this material has good reproducibility.

[0059] At the same time, the same method was used to test the stability and reproducibility of CoFe2O4@ZIF-67 / GCE. The test results showed that CoFe2O4@ZIF-67 / GCE also has good stability and reproducibility, but it is still slightly worse than CoFe2O4@ZIF-67 / Nafion / GCE. This may be because the CoFe2O4@ZIF-67 material is adsorbed and fixed on the surface of the magnetic glassy carbon electrode through magnetic force, so a small amount of material will detach over time, resulting in a decrease in electrode performance.

[0060] Example 5

[0061] Anti-interference test

[0062] In actual detection, there are often many interfering ions and Pb in the test solution. 2+ Therefore, the anti-interference ability of CoFe2O4@ZIF-67 / GCE was tested in this example. -5 mol / L of Pb 2+ 50 times of Zn 2+ 、Ni 2+ 、Fe 3+ 、Co 2+ 、Mn 2+ Cr 3+ , 20 times the Cd 2 + 、Cu 2+ and 10 times the Hg 2+ Perform DPV test, the measurement structure is as follows Figure 5 shown.

[0063] according to Figure 5 The change of DPV current intensity in the 2+ Pb 2+ The effect of Cu is relatively large, causing its peak current to drop by 10.42%. This is because Cu 2+ With Pb 2+ There is a competitive relationship, Cu 2+ It will rob the active sites on CoFe2O4@ZIF-67 / GCE, thus making Pb 2+ The current response of Zn 2+ 、Ni 2+ 、Fe 3+ 、Co 2+ 、Mn 2+ Cr 3+ 、Cd 2+ Metal ions such as Pb 2+ The effect of the current response is small, and the change of the current response is less than 5%. Therefore, it shows that CoFe2O4@ZIF-67 / GCE has good anti-interference performance and has a good effect on Pb 2+ Has good specificity.

[0064] Example 6

[0065] Please refer to Figure 6The embodiment discloses an electrochemical device, and the disclosed electrochemical device comprises a shell 100, a micro electrochemical workstation 160, a liquid feeding device and an electrochemical sensor; the shell 100 is provided with a detection chamber 102, a mounting cavity and a liquid inlet 101; the mounting cavity provides a setting space for mounting and fixing the liquid feeding device in the shell 100, so that the liquid feeding device can be mounted and fixed in the mounting cavity to realize hidden setting.

[0066] Meanwhile, the liquid inlet end of the liquid feeding device is communicated with the liquid inlet 101, and the liquid outlet end of the liquid feeding device is communicated with the detection chamber 102, so that the liquid to be detected can be transported into the detection chamber 102 through the liquid feeding device. Generally, the liquid feeding device can be selected from existing micro water pumps, but preferably a micro peristaltic pump 120 is selected, so that not only the automatic transportation of the liquid to be detected can be realized, but also the transportation amount of the liquid to be detected can be precisely controlled, which is beneficial to improving the accuracy of the detection structure.

[0067] The micro electrochemical workstation 160 is arranged in the shell 100 and connected with the electrochemical sensor; the electrochemical sensor is a three-electrode system, which comprises a reference electrode 140, a counter electrode 150 and a working electrode 130; specifically, the working electrode 130 is the CoFe2O4@ZIF-67 / Nafion / GCE electrode described above, the reference electrode 140 is an existing Ag / AgCl electrode, and the counter electrode 150 is an existing platinum wire electrode.

[0068] The liquid to be detected fed into the detection chamber 102 can be subjected to relevant electrochemical reactions through the working electrode 130, and the qualitative and quantitative analysis of lead ions can be realized through the micro electrochemical workstation 160 in cooperation with the reference electrode 140 and the counter electrode 150; it should be noted that the structure and principle of the micro electrochemical workstation 160 are prior art, and will not be described in detail.

[0069] The shell 100 is further provided with a material port, and the material port is communicated with the detection chamber 102 and has an open state and a closed state; the structure for switching the open state and the closed state of the material port can adopt an existing rotating type or sliding type opening and closing structure, and the embodiment will not be described in detail. When the material port is in the open state, the liquid to be detected in the detection chamber 102 can be discharged through the material port, and the buffer solution such as phosphate buffer solution or ABS buffer solution can be added into the detection chamber 102 through the material port.

[0070] In order to avoid the influence of impurities in the test liquid on the test results, a filtering structure 110, such as a filter mesh or a filter membrane, can be preferably set at the liquid inlet 101. In order to ensure the filtering effect, the number of layers can be multiple. In addition, in order to avoid the influence of back suction and other phenomena on the liquid delivery accuracy of the micro peristaltic pump 120, a one-way valve 121 is preferably set at the liquid outlet end of the micro peristaltic pump 120. The one-way valve 121 can ensure the normal delivery of the test liquid from the micro peristaltic pump 120 to the detection chamber 102, and prevent the backflow of the test liquid from the detection chamber 102 to the micro peristaltic pump 120.

[0071] It should be noted that, as another possible implementation method, the CoFe2O4@ZIF-67 / Nafion / GCE working electrode in this embodiment can also be replaced by a CoFe2O4@ZIF-67 / GCE working electrode, but this will reduce the service life of the working electrode to a certain extent.

[0072] Example 7

[0073] The electrochemical device in Example 6 was used to measure the Pb content in the actual sample. 2+ The concentration was tested, and the spiked recovery rate was used as the judgment standard. The specific processing process is as follows:

[0074] Selection of test solution: After the lake or river water is still for 48 hours, the supernatant is collected. A portion of the supernatant is filtered through a 0.22µm filter membrane and then the lead ion content in the actual sample is detected by ICP-OES. A portion of the supernatant is diluted 20 times with ABS (pH = 4.5) buffer and prepared into a 1µmol / L Pb 2+ and 10µmol / L Pb 2+ The sample is used as the test solution for concentration measurement.

[0075] Detection process: open the one-way valve 121, start the peristaltic pump to draw a certain amount of detection liquid into the detection chamber 102; then, turn off the peristaltic pump switch, and then close the one-way valve 121, and allow the working electrode in the detection chamber 102 to fully adsorb and combine with the test liquid; after sufficient adsorption, release the excess test solution through the material port, and add buffer to the detection chamber 102 to maintain the pH stability of the detection environment to avoid the influence of pH changes on subsequent detection results; then, turn on the micro electrochemical workstation 160 switch to detect the lead ion concentration; according to the heavy metal ion Pb 2+ The concentration of heavy metal ions Pb in the test solution can be obtained by constructing a linear regression equation based on the relationship between concentration and peak current change.

[0076] Test results: Figure 7 As shown, the electrochemical device was used to 2+The detection result of the standard addition concentration is basically consistent with the detection result of ICP-OES, the linear equation I (muA) = 1.36978c (muM) + 0.38326, the linear correlation coefficient is 0.99996, the detection limit (LOD) is 9.3738*10 -9 M (S / N=3), the sensitivity is 32.17 muA*mM -1 ·cm -2 And the recovery rate of the river water and the lake water is between 99.51-103.42%, and the RSD value is less than 5%; therefore, it is explained that it has wide application prospect in accurately detecting Pb 2+ of the actual sample.

[0077] The above embodiments of the application mainly describe the differences between the various embodiments, and the different optimization features between the various embodiments can be combined to form a better embodiment without contradiction, and the writing is simple, and therefore, it is not repeated here.

[0078] The above only describes the embodiments of the application and is not used to limit the application. The application can have various changes and variations for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the application shall be included in the scope of claims of the application.

Claims

1. An electrochemical sensor for lead ion detection, the electrochemical sensor comprising a working electrode, characterized in that, The base of the working electrode is modified with a magnetic composite material having a CoFe2O4@ZIF-67 core-shell structure, wherein CoFe2O4 is a magnetic core, the CoFe2O4 is in the form of a rough-surfaced spherical shape, and the rough surface is composed of regular cubic structures and irregular small particles, and ZIF-67 is a shell layer, the ZIF-67 densely wraps the core in the form of small particles, and the ZIF-67 has a regular dodecahedron shape; the base is a magnetic glassy carbon electrode, and the magnetic composite material is located on the working surface of the base to form a CoFe2O4@ZIF-67 structure layer; the magnetic glassy carbon electrode and the CoFe2O4@ZIF-67 structure layer form a CoFe2O4@ZIF-67 / GCE working electrode. The magnetic composite material is prepared by the following method: (1) CoFe2O4 and dimethyl imidazole are dispersed in a methanol solution to prepare solution A; Co(NO3)2·6H2O is added to a methanol solution to prepare solution B; Then, under stirring, the solution B is added dropwise to the solution A, and after mixing uniformly, a reaction liquid C is prepared; (2) The reaction liquid C is transferred to a reaction kettle for hydrothermal reaction, and after the reaction is completed, the reaction kettle is naturally cooled to room temperature, and the precipitate is collected by magnetic separation; then the precipitate is washed with ethanol, and the CoFe2O4@ZIF-67 composite material is prepared by drying.

2. The electrochemical sensor for lead ion detection according to claim 1, wherein, The outer surface of the CoFe2O4@ZIF-67 structure layer is coated with a Nafion film layer to form a CoFe2O4@ZIF-67 / Nafion / GCE working electrode.

3. A method for fabricating an electrochemical sensor for lead ion detection, the method comprising: providing a substrate; providing a working electrode; providing a counter electrode; providing a reference electrode; and providing a lead ion selective membrane between the working electrode and the counter electrode. The method comprises a magnetic composite material modification step: the powder of the magnetic composite material is dispersed in deionized water to prepare a suspension, and then the suspension is drop-coated on the surface of a polished magnetic glassy carbon electrode, and after drying, a CoFe2O4@ZIF-67 / GCE working electrode is prepared; the magnetic composite material has a CoFe2O4@ZIF-67 core-shell structure, wherein CoFe2O4 is a magnetic core, the CoFe2O4 is in the form of a rough-surfaced spherical shape, and the rough surface is composed of regular cubic structures and irregular small particles, and ZIF-67 is a shell layer, the ZIF-67 densely wraps the core in the form of small particles, and the ZIF-67 has a regular dodecahedron shape; The magnetic composite material is prepared by the following method: (1) CoFe2O4 and dimethyl imidazole are dispersed in a methanol solution to prepare solution A; Co(NO3)2·6H2O is added to a methanol solution to prepare solution B; Then, under stirring, the solution B is added dropwise to the solution A, and after mixing uniformly, a reaction liquid C is prepared; (2) The reaction liquid C is transferred to a reaction kettle for hydrothermal reaction, and after the reaction is completed, the reaction kettle is naturally cooled to room temperature, and the precipitate is collected by magnetic separation; then the precipitate is washed with ethanol, and the CoFe2O4@ZIF-67 composite material is prepared by drying.

4. An electrochemical device for lead ion detection, characterized by, The electrochemical sensor for detecting lead ions comprises a shell, a micro electrochemical workstation, a liquid feeding device and the electrochemical sensor for detecting lead ions according to claim 1 or 2; the shell is provided with a detection chamber, a mounting cavity, a liquid inlet and a material port; the liquid feeding device is fixedly installed in the mounting cavity, and the liquid inlet of the liquid feeding device is communicated with the liquid inlet, and the liquid outlet of the liquid feeding device is communicated with the detection chamber; the micro electrochemical workstation is arranged in the shell and connected with the electrochemical sensor; the electrochemical sensor further comprises a reference electrode and a counter electrode, and the working electrode, the reference electrode and the counter electrode are arranged in the detection chamber; the material port is communicated with the detection chamber, and the material port has an open state and a closed state.

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