Ionic liquid-based laser-induced graphene portable electrochemical sensor as well as preparation method and application thereof

Abstract

The invention discloses a laser-induced graphene portable electrochemical sensor based on ionic liquid and a preparation method and application thereof, and belongs to the field of electrochemical sensing. According to the invention, polyimide coated with ionic liquid is used as a flexible substrate material, a nitrogen and sulfur co-doped graphene material (N / S (at) LIG) is prepared through one-step laser induction, and the heavy metal ion detection sensor with low detection limit and wide linear range is constructed in combination with an electrochemical sensing technology. The prepared electrode is combined with a portable electrochemical workstation, so that the portable analysis and detection of the content of cadmium ions and lead ions are realized. The preparation method has the characteristics of simple preparation and convenient operation, the prepared electrode does not need additional nanometer material modification, the electrode can be combined with a portable electrochemical workstation for field detection, a new method is provided for detecting heavy metal ions in the field of instant analysis, and the sensor has flexible detection performance and is suitable for popularization and application. The requirements on rapid detection of cadmium ions and lead ions in different scenes can be met.

Description

Technical Field

[0001] The invention belongs to the field of electrochemical sensing, and particularly relates to a laser-induced graphene portable electrochemical sensor based on ionic liquid, and a preparation method and application thereof. Background Art

[0002] Electrochemical sensors are one of the most promising technologies for selectively and sensitively detecting various toxic pollutants. Carbon materials are widely used in electrochemical sensing applications due to their excellent properties such as good electrical conductivity, high temperature resistance, and corrosion resistance. In 2014, the Tour team used a carbon dioxide infrared laser system to directly write laser-induced graphene (LIG) on the surface of a commercial polyimide (PI) film. Compared with traditional electrode materials, LIG ​​has the advantages of high porosity, large specific surface area, strong conductivity, easy manufacturing and low cost. In addition, this process combines large-area graphene preparation with customized patterns, does not require expensive experimental equipment and complex processing, and greatly simplifies the graphene preparation process. Therefore, LIG ​​has become a very promising material for mass production of disposable electrochemical sensors.

[0003] Ionic liquids (ILs) are organic salts that are liquid at or near room temperature and are usually composed of organic cations and inorganic or organic anions. Ionic liquids can be used as carbon precursors and have some significant advantages. First, ionic liquids are rich in carbon elements and can be directly used as carbon sources. Second, ionic liquids have good compatibility with a variety of compounds and can be used to prepare carbon composites. Third, the diversity of ionic liquid structures allows the introduction of element doping into carbon materials. In addition, ionic liquids and sp 2 There is a strong interaction between carbon-based materials (such as graphene), which can effectively prevent the stacking and agglomeration of carbon materials.

[0004] Not all ionic liquids are suitable as carbon sources, because high-temperature treatment of ILs usually leads to complete decomposition. When studying the thermal stability of ILs, Wooster et al. found that ILs containing cyanide anions would not completely decompose into volatile products when heat-treated in an inert gas atmosphere. This is because they have special functional groups that undergo cross-linking reactions during the heat treatment process. However, the traditional process of carbonization of ionic liquids usually requires high temperature, high pressure, and an inert gas environment, which is time-consuming and expensive.

[0005] It is well known that heavy metal accumulation poses a great potential threat to humans and the natural environment. Among various heavy metal ions, cadmium and lead are common highly toxic and harmful environmental pollutants. Cadmium can accumulate in organs such as the lungs, liver, kidneys and bones. Cadmium poisoning can cause muscle atrophy and osteoporosis in the human body. Lead is carcinogenic, and trace exposure can cause damage to many organs, especially the central nervous system and kidneys.

[0006] Considering the accumulation of heavy metal ions in the food chain, it is necessary to quantitatively detect heavy metal ions not only in drinking water but also in water sources to maintain the health of humans and ecosystems. This requires sensors to respond quickly, be cost-effective, portable and easy to use. Electrochemical sensors meet the above requirements, but require special electrode materials to achieve sensitive and specific responses to target analytes. The research of Ahmad et al. showed that nitrogen atoms have five valence electrons around them and usually form three bonds with other atoms, leaving a pair of electrons. This lone pair of electrons acts as an activation site that triggers the interaction between heavy metal ions. At the same time, N doping can produce defect sites by replacing C atoms, thereby improving the electrochemical activity of graphene-based nanomaterials. In addition, the research of Li et al. showed that some metal ions can be fixed on the electrode surface through thiol bonds due to the formation of bonds between metals and thiol groups.

[0007] Traditional heavy metal detection technologies mainly include atomic absorption spectroscopy, inductively coupled plasma mass spectrometry, energy dispersive X-ray fluorescence spectroscopy, etc. Although these traditional detection methods are highly sensitive and selective to trace heavy metals, they are unable to meet the rapid development of this field in terms of manpower and time requirements. Therefore, it is of great significance to develop a fast, low-cost, portable, and highly sensitive heavy metal detection method. The present invention is based on the construction of a portable electrochemical sensor to achieve cadmium ion (Cd 2+ ) and lead ions (Pb 2+ ) on-site effective monitoring. Summary of the invention

[0008] In view of the defects of the traditional ionic liquid carbonization process and the traditional heavy metal detection technology, the purpose of the present invention is to provide a method for preparing a laser-induced nitrogen and sulfur co-doped graphene electrode, and combine it with a portable electrochemical workstation to construct a small electrochemical sensor for rapid on-site detection and analysis of cadmium ions and lead ions. At the same time, the introduction of nitrogen and sulfur elements can enhance the interaction between the graphene electrode and heavy metal ions, and improve the sensitivity and selectivity of heavy metal ion detection.

[0009] The purpose of the present invention is mainly achieved through the following technical means:

[0010] The preparation method of the heteroatom-doped graphene electrode described in the present invention is to combine laser engraving with high-temperature carbonization of ionic liquids, and use the high energy of laser radiation to convert polyimide coated with ionic liquids into graphene materials co-doped with nitrogen and sulfur. Combined with electrochemical sensing technology, the portable three-electrode is combined with a small electrochemical workstation to construct a portable electrochemical sensor for sensitive detection of cadmium ions and lead ions. The specific steps of preparing the portable electrochemical sensor in the present invention are as follows:

[0011] 1) A polydimethylsiloxane (PDMS) polymer solution is coated on the surface of a clean glass sheet and placed in a vacuum drying oven for heating and curing to obtain a PDMS substrate.

[0012] 2) A polyimide PI tape is bonded to a PDMS substrate to obtain a PI / PDMS composite substrate, and then an ionic liquid (1-butyl-3-methylimidazole thiocyanate) is drop-coated on the PI / PDMS composite substrate of a fixed size and allowed to stand to spread evenly.

[0013] 3) Use a computer to draw a three-electrode system pattern and import the pattern into the CO 2 Laser engraving system, using laser induction to produce nitrogen and sulfur co-doped graphene electrodes, denoted as N / S@LIG.

[0014] 4) Paste polyimide insulating tape on the wire area on the electrode surface to isolate the sensing area and the detection area.

[0015] 5) Apply Ag / AgCl ink (purchased from ALS, Japan, product number 011464) at the reference electrode position, bake it under an infrared lamp, and use it as a reference electrode.

[0016] In the step 1), PDMS and a cross-linking agent (purchased from Hebei Moen Biotechnology Co., Ltd., product model Sylgard 184, purchase link http: / / whcg.bjut.edu.cn / Front.aspx?page=cpxq¶m=85849670&settab=1) are mixed in a weight ratio of 10:1, stirred evenly, put into a vacuum drying oven for degassing for 30 minutes, taken out, poured onto a glass plate, and prepared with the aid of a film applicator. A film with a thickness of 0.4 mm was prepared, and then put into the vacuum drying oven again for degassing for 30 minutes, and the temperature was set to 60° C. and the heating time was 90 minutes to completely cure the material.

[0017] In the step 2), the size of the fixed-size PI / PDMS composite substrate is 20cm×2.5cm, the amount of ionic liquid applied is 0.12mL, and the standing time is 10min. In the process of ionic liquid coating, the amount of ionic liquid applied is a key factor. The amount of ionic liquid is optimized in the present invention, and 0.12mL, 0.24mL, and 0.48mL of ionic liquid are selected for testing. The results show that when the amount of ionic liquid is too much (0.48mL), the thickness of the ionic liquid will affect the integrity of the electrode formed by laser engraving; and when the amount of ionic liquid is 0.24mL, although it will not affect the integrity of the electrode, the morphology of the generated graphene is significantly different from that when the amount of ionic liquid is 0.12mL; only when the amount of ionic liquid is 0.12mL, the uniformity of the ionic liquid coating can be maintained, and the generated electrode has a complete morphology and optimal electrochemical performance.

[0018] In step 3), the customized pattern is pre-drawn by CorelLASER 2013.02 software, CO 2 The laser power of the laser engraving system is set to 10.5W, the laser scanning speed is set to 140mm / s, and the laser is set to a focusing state. When preparing the N / S@LIG three-electrode, the laser parameters have a significant effect on the physical and chemical properties of graphene, because laser beams of different energies may affect the doping of N and S atoms and the graphene network structure, thereby affecting the response of the electrode to heavy metal ions. The present invention optimizes the main factors affecting laser energy (laser power and scanning speed), wherein the laser power varies between 9.5W and 11.5W, and the scanning speed varies between 120mm / s and 160mm / s. Finally, 10.5W is selected as the optimal laser power, and 140mm / s is selected as the optimal scanning speed. Under the optimal laser parameters, the generated N / S@LIG three-electrode has holes of different sizes, presenting a fairly dense layered porous structure and a three-dimensional graphene skeleton ( Figure 1 ).

[0019] In the step 4), before the polyimide insulating tape is attached to the wire area on the electrode surface, the electrode surface is first rinsed with ultrapure water to wash away excess ionic liquid, and then blown dry with nitrogen to stabilize the N / S@LIG electrode.

[0020] In the step 5), the amount of Ag / AgCl ink applied is 2 μL, the drying time under the infrared lamp is 5 minutes, and the rated power of the infrared lamp is 800W.

[0021] The method for simultaneous detection of cadmium ions and lead ions based on portable electrochemical sensors is as follows:

[0022] 1) The LIG electrode and N / S@LIG electrode were immersed in 10 mL of 5 mmol / L KCl containing 0.1 mol / L KCl. 3 [Fe(CN) 6 ] solution, and then the two electrodes were subjected to electrochemical cyclic voltammetry scanning and electrochemical impedance spectroscopy measurement. After scanning, the corresponding cyclic voltammetry (CV) graph and electrochemical impedance spectroscopy (EIS) graph were obtained. The scanning rate of CV measurement was 100 mV s -1 , the potential range is -0.2V~0.6V; the frequency of EIS measurement is 0.1Hz~10 6 Hz, with an amplitude of 5mV.

[0023] 2) The prepared electrochemical sensor was immersed in a certain concentration of cadmium ion and lead ion standard solution, and measured by square wave anodic stripping voltammetry (SWASV), and the concentration and SWASV response value were plotted. During the detection, 10mL of 0.1mol / L acetate buffer was selected as the detection base solution, in which the square wave scanning potential range was -1.4V~0.0V, the pulse amplitude was 200mV, the frequency was 25Hz, and the step amplitude was 5mV. The optimized detection conditions include: buffer pH=5, deposition potential of -1.4V, and deposition time of 300s.

[0024] 3) Select K + 、Na + Mg 2+ , Ca 2+ , Cl - and SO 4 2- The selectivity of the N / S@LIG electrochemical sensor was determined as common interfering substances in the environment where cadmium ions and lead ions exist. During the detection, 10 mL of 0.1 mol / L acetate buffer (pH = 5) was used as the detection base solution, the concentration of cadmium ions and lead ions was 2 μmol / L, the molar concentration of other ions was 50 times that of cadmium ions and lead ions, and the solution to be tested contained K + 、Na + Mg 2+ , Ca 2+ , Cl - 、SO 4 2- At least one of .

[0025] Beneficial effects of the present invention: This method creatively develops a one-step laser-induced, low-cost and scalable method for preparing nitrogen and sulfur co-doped graphene electrodes based on ionic liquids, and prepares shape-controllable graphene electrodes (N / S@LIG) uniformly doped with nitrogen and sulfur elements by an in-situ method. Utilizing the high electrocatalytic activity and good conductivity of N / S@LIG, the proposed portable electrochemical sensor has excellent cadmium ion and lead ion sensing performance, and the method combining high-temperature carbonization of ionic liquids with laser engraving has not been reported. The method of preparing N / S@LIG heavy metal ion portable electrochemical sensor by the designed laser direct writing process can provide inspiration for the construction of various heteroatom-doped LIG electrodes for high-performance sensors, highlighting the potential application prospects of portable and wearable health monitoring. The method for preparing laser-induced heteroatom-doped graphene proposed in this study may be an attractive candidate method for mass manufacturing sensors based on the characteristics of laser-induced non-contact and computer-controlled.

[0026] Compared with other electrochemical technologies for detecting cadmium ions and lead ions, the present invention has an integrated portable three-electrode and a small electrochemical workstation equipped with a tablet computer, and the method has a lower detection limit and a wider detection range for cadmium ions and lead ions, and can simultaneously detect two heavy metal ions coexisting in the environment, with good practical performance. In addition, the method realizes the effective and real-time detection and analysis of the content of heavy metal ions using portable components, and has broad development prospects in instant detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings and attached tables, wherein:

[0028] Figure 1 High-resolution SEM image of laser-induced nitrogen-sulfur co-doped graphene electrode (N / S@LIG).

[0029] Figure 2 Laser-induced graphene (LIG) electrode and laser-induced nitrogen-sulfur co-doped graphene (N / S@LIG) electrode were prepared in 5mmol / L KCl solution containing 0.1mol / L KCl. 3 [Fe(CN) 6 ] Cyclic voltammetry (CV) diagrams in solution (a-LIG electrode; b N / S@LIG electrode).

[0030] Figure 3 Laser-induced graphene (LIG) electrode and laser-induced nitrogen-sulfur co-doped graphene (N / S@LIG) electrode were prepared in 5mmol / L KCl solution containing 0.1mol / L KCl. 3 [Fe(CN) 6]Electrochemical impedance spectroscopy (EIS) graphs in solution (a-LIG electrode; b N / S@LIG electrode).

[0031] Figure 4 SWASV diagrams of cadmium and lead ions at different concentrations (0.5-200 μmol / L) detected using N / S@LIG electrode under optimal experimental conditions.

[0033] Figure 5 This is the linear relationship between the SWASV response value of the electrochemical sensor (N / S@LIG) and the cadmium ion concentration.

[0033] Figure 6 This is the linear relationship between the SWASV response value of the electrochemical sensor (N / S@LIG) and the lead ion concentration.

[0034] Table 1 shows the electrochemical sensor (N / S@LIG) at K + 、Na + Mg 2+ , Ca 2+ , Cl - and SO 4 2- The SWASV signal response changes to cadmium ions and lead ions in the presence of 50 times the molar concentration of the interfering substances. The signal response when only cadmium ions and lead ions exist in the system is regarded as 100%. DETAILED DESCRIPTION

[0035] Example 1

[0036] 1. A portable electrochemical sensor, comprising a flexible PI / PDMS polymer substrate and three electrodes arranged on the polymer substrate, wherein the three electrodes include a working electrode, a reference electrode and a counter electrode, and the working electrode, the reference electrode and the counter electrode are all graphene electrodes generated by laser one-step induction.

[0037] 2. The portable electrochemical sensor is characterized in that the working electrode is a nitrogen-sulfur co-doped laser-induced graphene electrode, which is prepared with polyimide coated with ionic liquid as the base material. The nitrogen and sulfur doping can make the laser-induced graphene have more holes, increase the specific surface area of ​​the electrode, provide more active sites for binding analytes, and thus improve the sensitivity and selectivity of the sensor. The portable electrochemical sensor using ionic liquid to prepare nitrogen-sulfur co-doped graphene by one-step laser induction has not been reported so far.

[0038] 3. The portable electrochemical sensor described above is characterized in that the method creatively develops a one-step laser-induced, low-cost and scalable method for preparing nitrogen and sulfur co-doped graphene electrodes, and prepares shape-controllable electrodes (N / S@LIG) uniformly doped with nitrogen and sulfur elements by an in-situ method. Taking advantage of the high electrocatalytic activity of N / S@LIG and the three-dimensional porous structure of N / S@LIG with excellent conductivity, the proposed portable electrochemical sensor has excellent cadmium ion and lead ion sensing performance. In summary, a simple, efficient, single-step laser direct writing process for preparing N / S@LIG heavy metal ion portable electrochemical sensor is designed, which can provide inspiration for the construction of various shape-controllable heteroatom-doped LIG electrodes for high-performance sensors, highlighting the potential application prospects of portable and wearable health monitoring. The method for preparing laser-induced heteroatom-doped graphene proposed in this study may be an attractive candidate method for mass manufacturing sensors based on the characteristics of laser-induced non-contact and computer-controlled.

[0039] The specific steps of preparing the electrochemical sensor for detecting cadmium ions and lead ions in the present invention are as follows:

[0040] 1) Polydimethylsiloxane (PDMS) and crosslinking agent (purchased from Hebei Moen Biotechnology Co., Ltd., product model Sylgard 184, purchase link The mixture was mixed at a weight ratio of 10:1, stirred evenly, and then put into a vacuum drying oven for degassing for 30 minutes, taken out, poured onto a glass plate, and a film with a thickness of 0.4 mm was prepared with the help of a film applicator. The mixture was put into a vacuum drying oven for degassing for 30 minutes, and then the temperature was set at 60° C. and the heating time was 90 minutes to completely cure the material to obtain a PDMS substrate.

[0041] 2) A polyimide tape (PI) was bonded to the cured PDMS, and then 0.12 mL of ionic liquid (1-butyl-3-methylimidazole thiocyanate) was coated on a PI / PDMS composite substrate of a fixed size (20 cm×2.5 cm) and allowed to stand for 10 min to allow it to spread evenly.

[0042] 3) Draw the three-electrode pattern on the computer and import the pattern into the CO 2 Lasers, using CO 2 The laser induced the formation of nitrogen and sulfur co-doped graphene electrodes (N / S@LIG) on the PI film coated with ionic liquid. The laser power was set to 10.5W, the laser scanning speed was 140mm / s, and the laser was adjusted to the focusing mode. After that, the electrode surface was rinsed with ultrapure water to clean off the excess ionic liquid, and dried with nitrogen to stabilize the N / S@LIG electrode.

[0043] 4) Use polyimide insulating tape to encapsulate the wire area of ​​the three-electrode pattern to isolate the sensing area and the reaction area.

[0044] 5) Take 2 μL of Ag / AgCl ink and drop it on the reference electrode surface of LIG, and bake it under an infrared lamp for 5 minutes with a power of 800 W to build its own three-electrode system.

[0045] Example 2

[0046] The portable electrochemical sensor prepared in Example 1 was used for detection:

[0047] 1) The flexible portable electrochemical sensor was immersed in 10 mL of 5 mmol / L KCl containing 0.1 mol / L KCl. 3 [Fe(CN) 6 ] solution, and then the electrochemical sensor is subjected to electrochemical cyclic voltammetry scanning and electrochemical impedance spectroscopy measurement. After scanning, the corresponding cyclic voltammetry diagram ( Figure 2 ) and AC impedance diagram ( Figure 3 The scan rate of CV measurement was 100 mV s -1 , the potential range is -0.2V~0.6V; the frequency of EIS measurement is 0.1Hz~10 6 Hz, with an amplitude of 5mV.

[0048] 2) The prepared electrochemical sensor was immersed in standard solutions of cadmium and lead ions with different concentration gradients (0.5, 5, 10, 20, 30, 40, 60, 75, 100, 125, 150, 175 and 200 μmol / L), and measured by square wave anodic stripping voltammetry (SWASV), and the concentration and SWASV response value were plotted. 10 mL of 0.1 mol / L acetate buffer was used as the detection base solution, with a square wave scanning potential range of -1.4 V to 0.0 V, a pulse amplitude of 200 mV, a frequency of 25 Hz, and a step amplitude of 5 mV. The optimized detection conditions include: buffer pH = 5, deposition potential of -1.4 V, and deposition time of 300 s.

[0049] 3) Select K + 、Na + Mg 2+ , Ca 2+ , Cl - and SO 4 2-The selectivity of the portable electrochemical sensor was determined as a common coexisting interferent in the presence of cadmium ions and lead ions. During the detection, 10 mL of 0.1 mol / L acetate buffer (pH = 5) was used as the detection base solution, the concentration of cadmium ions and lead ions was 2 μmol / L, the molar concentration of other ions was 50 times that of cadmium ions and lead ions, and the solution to be tested contained K + 、Na + Mg 2+ , Ca 2+ , Cl - 、SO 4 2- At least one of .

[0050] As attached Figure 5 As shown in Figure 2, the peak current response Ipa shows a good linear relationship with the concentration of cadmium ions in the range of 0.5μmol / L-60μmol / L and 60μmol / L-200μmol / L, and the linear equations are: Ip(μA)=0.807c(μmol / L)-0.003(R 2 =0.994) and Ip(μA)=0.249c(μmol / L)+36.174(R 2 =0.996), the detection limit (LOD) of this method was calculated to be 0.02 μmol / L (S / N=3). Figure 6 As shown in Figure 2, the peak current response Ipa showed a good linear relationship with the lead ion concentration in the range of 0.5μmol / L-60μmol / L and 60μmol / L-200μmol / L, and the linear equations were: Ip(μA)=1.279c(μmol / L)+0.175(R 2 =0.985) and Ip(μA)=0.298c(μmol / L)+63.658(R 2 =0.996), and the detection limit (LOD) of the method was calculated to be 0.01 μmol / L (S / N=3). Since the N / S@LIG electrode has good electrochemical properties, the sensor proposed in the present invention has a low detection limit and a wide detection range, and can achieve quantitative detection of cadmium ions and lead ions. At the same time, the sensor has good selectivity for common cations and anions in the environment, which shows that the sensor developed by us has potential application prospects in the on-site detection of heavy metal ions.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention. Table 1

Claims

1. A laser-induced graphene portable electrochemical sensor based on ionic liquid, comprising three electrodes, characterized in that: The three electrodes are laser-induced graphene electrodes, which are made of polyimide PI bonded to polydimethylsiloxane (PDMS) as a flexible substrate material, coated with ionic liquids (ILs), and converted into graphene by one-step laser induction; at the same time, the laser carbonizes the ionic liquid to introduce nitrogen and sulfur elements into the graphene electrode; The preparation method comprises the following steps: 1) Mix polydimethylsiloxane (PDMS) and a cross-linking agent in a weight ratio of 10:1, stir evenly, put into a vacuum drying oven for degassing for 30 minutes, take out, pour on a glass plate, use a film applicator to prepare a film with a thickness of 0.4 mm, put into a vacuum drying oven again for degassing for 30 minutes, and then set the temperature to 60°C and the heating time for 90 minutes to completely cure the material; 2) bonding a polyimide PI tape to the cured PDMS, and then coating 0.12 mL of ionic liquid, i.e., 1-butyl-3-methylimidazole thiocyanate, on a PI / PDMS composite substrate of a fixed size of 20 cm × 2.5 cm, and allowing it to stand for 10 min to allow it to spread evenly; 3) Drawing a three-electrode pattern on a computer, importing the pattern into a CO2 laser, and using a CO2 laser to induce the generation of graphene on the PI film coated with an ionic liquid; setting the laser power to 10.5W, the laser scanning speed to 140mm / s, and adjusting the laser to a focusing mode, a nitrogen- and sulfur-co-doped laser-induced graphene electrode N / S@LIG is generated by laser induction in one step; then, the electrode surface is rinsed with ultrapure water to clean off excess ionic liquid, and the N / S@LIG electrode is blown dry with nitrogen to stabilize it; 4) The wire area of ​​the three-electrode pattern was encapsulated with polyimide insulating tape, and 2 μL Ag / AgCl ink was drop-coated on the reference electrode of N / S@LIG to construct its own three-electrode system; then 2 μL Ag / AgCl ink was applied to the reference electrode surface of N / S@LIG and dried under an infrared lamp with a rated power of 800 W for 5 min.

2. A portable electrochemical sensor based on laser-induced nitrogen and sulfur co-doped graphene obtained by the preparation method as claimed in claim 1.

3. Use of the portable electrochemical sensor according to claim 2 in rapid detection of cadmium ions and lead ions, characterized in that: The following steps are involved: 1) The portable electrochemical sensor is immersed in the detection solution, and then the electrochemical cyclic voltammetry and the electrochemical impedance spectroscopy method are used in combination with the portable electrochemical sensor for detection. After scanning, the corresponding cyclic voltammetry (CV) graph and the electrochemical impedance spectroscopy (EIS) graph can be obtained; during the detection, 10 mL of a 5 mmol / L K3[Fe(CN)6] solution containing 0.1 mol / L KCl is selected as the detection base solution, and the scanning rate of the CV measurement is 100 mV s -1 , the potential range is -0.2V~0.6V; the frequency of EIS measurement is 0.1Hz~10 6 Hz, amplitude 5mV; 2) The portable electrochemical sensor was immersed in a standard solution containing cadmium ions and lead ions with different concentration gradients, and measured by square wave anodic stripping voltammetry (SWASV), and the concentration and SWASV response value were plotted; 10 mL of 0.1 mol / L acetate buffer was used as the detection base solution during the detection, wherein the square wave scanning potential range was -1.4 V to 0.0 V, the pulse amplitude was 200 mV, the frequency was 25 Hz, and the step amplitude was 5 mV; the optimized detection conditions included: buffer pH = 5, deposition potential was -1.4 V, and deposition time was 300 s; 3) Select K + 、Na + Mg 2+ , Ca 2+ , Cl - and / or SO4 2- The selectivity of the portable electrochemical sensor was tested as an interferent in the cadmium ion and lead ion detection environment; 10 mL of 0.1 mol / L acetate buffer with a pH of 5 was used as the detection base solution, the concentration of cadmium ions and lead ions was 2 μmol / L, the molar concentration of other ions was 50 times that of cadmium ions and lead ions, and the other ions in the solution to be tested were K + 、Na + Mg 2+ , Ca 2+ , Cl - 、SO4 2- At least one of .

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