Potassium ion sensor based on AuNPs / MXene / SPCE and preparation method thereof

Abstract

The invention discloses a potassium ion sensor based on AuNPs / MXene / SPCE and a preparation method thereof, and belongs to the technical field of electronic components. Comprising a screen-printed carbon electrode SPCE, an MXene layer modified on the surface of a working electrode of the screen-printed carbon electrode, a gold nanoparticle AuNPs layer formed on the surface of the MXene layer through an electrochemical deposition method, a potassium ion selective membrane covering the gold nanoparticle AuNPs layer, and a GO-PVA hydrogel layer coating the surface of the potassium ion selective membrane. According to the prepared sensor, only potassium ions in sweat can pass through the selective membrane, the selectivity of the sensor is improved, meanwhile, due to the application of the AuNPs / MXene composite material, the surface area-volume ratio of a silk-screen printing carbon electrode is greatly improved, more potassium ions participate in ion-electron conversion, the sensitivity of the sensor is improved, and the application range of the sensor is widened. And the detection range is expanded.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic components, and particularly relates to a potassium ion sensor based on AuNPs / MXene / SPCE and a preparation method thereof. Background Art

[0002] Potassium ions, as one of the key electrolytes in the human body, play an important role in maintaining nerve conduction, muscle contraction, and acid-base balance in body fluids. Traditional blood potassium testing relies on invasive blood sampling, which has problems such as complex operation, inability to monitor in real time, and poor patient compliance. This is especially difficult to meet the needs in scenarios such as sports health management, postoperative monitoring, and chronic disease tracking. Sweat, as a body fluid rich in physiological information, provides an ideal medium for in situ non-invasive detection of potassium ions. However, its low ion concentration (0.5-10mmol / L) and complex matrix place extremely high demands on the sensitivity, selectivity, and anti-interference ability of the sensor.

[0003] Traditional liquid ion-selective electrodes rely on internal reference solutions and have drawbacks such as bulky size, easy leakage, and poor stability, making them difficult to integrate into wearable devices. Although solid-state ion-selective electrodes solve the shortcomings of liquid electrodes through solid-solid contact interfaces, they still face challenges such as high interface impedance, slow response speed, and insufficient long-term stability. In recent years, two-dimensional materials MXene (such as Ti3C2T x ) provides an efficient channel for ion transport due to its excellent conductivity, high mechanical strength, good hydrophilicity, large specific surface area and layered structure. At the same time, its large specific surface area can load functional nanomaterials (such as AuNPs), significantly improving the electron transfer efficiency of the sensing interface. Gold nanoparticles (AuNPs) can further amplify electrochemical signals due to their excellent biocompatibility, high catalytic activity and surface plasmon resonance effect, and form a synergistic effect with MXene to optimize the sensitivity and detection limit of the sensor. In addition, screen-printed carbon electrodes (SPCEs) have become ideal carriers for wearable sensors due to their low cost, mass production and adaptability to flexible substrates. However, their intrinsic conductivity and insufficient active sites limit their detection performance.

[0004] Regarding ion-selective membranes, the commonly used ion carrier valinomycin, while highly selective and efficient for potassium ions, suffers from significant toxicity, hindering the long-term application of sensors for sweat testing in contact with human skin. Furthermore, given the poor mechanical strength of the selective membrane, which can lead to peeling and water layer formation during long-term testing, modifying its surface with a GO-PVA (graphene oxide-polyvinyl alcohol) hydrogel has emerged as a promising solution to these challenges. This hydrogel serves to stabilize the selective membrane, prevent valinomycin leakage, and allow permeation of sweat.

[0005] While existing solid-state ion sensors based on single materials (such as graphene and carbon nanotubes) have made some progress, they still face challenges such as insufficient sensitivity (e.g., CN 110192869 A) and poor long-term stability (e.g., CN 111854595 B). The MXene / AuNPs composite system effectively overcomes these bottlenecks through interfacial engineering: MXene's interlayer channels promote ion diffusion, the localized surface of AuNPs forms an ion-electron double-layer capacitance with the electrode, enhancing signal response, the flexible SPCE substrate ensures conformal adhesion to the skin, and GO-PVA prevents detachment of the ion-selective membrane and leakage of valinomycin, enabling in situ dynamic monitoring of sweat. Therefore, the development of a potassium ion sensor based on AuNPs / MXene / SPCE not only overcomes the limitations of traditional detection technologies but also provides high-precision, non-invasive, and real-time monitoring solutions for personalized medicine, sports health management, and other fields. Summary of the Invention

[0006] The purpose of the present invention is to address the above problems and provide an electrochemical sensor for potassium ion detection based on AuNPs / MXene / SPCE with high sensitivity, high stability, high selectivity and repeatability, which can prevent the leakage of valinomycin, and its preparation and detection method, providing a new solution for future safe and efficient flexible wearable devices.

[0007] In order to achieve its purpose, the present invention adopts the following technical solutions:

[0008] A potassium ion sensor based on AuNPs / MXene / SPCE comprises a screen-printed carbon electrode (SPCE), a MXene layer modified on the surface of a working electrode of the screen-printed carbon electrode, a gold nanoparticle (AuNPs) layer formed on the surface of the MXene layer by electrochemical deposition, a potassium ion selective membrane covering the gold nanoparticle (AuNPs) layer, and a GO-PVA hydrogel layer coated on the surface of the potassium ion selective membrane.

[0009] Furthermore, the potassium ion selective membrane comprises valinomycin, potassium tetraphenylborate KB(C6H5)4, polyvinyl chloride PVC and di(2-ethylhexyl) sebacate DOS.

[0010] A preparation method for a potassium ion sensor based on AuNPs / MXene / SPCE comprises the following steps: drop-coating MXene material on the surface of a finished screen-printed carbon electrode to obtain an MXene / SPCE electrode; then depositing a layer of gold nanoparticles on the MXene / SPCE electrode by electrochemical deposition to obtain an AuNPs / MXene / SPCE electrode; then modifying the AuNPs / MXene / SPCE electrode with a potassium ion selective membrane by drop-coating; and finally covering the electrode surface modified with the potassium ion selective membrane with GO-PVA hydrogel by drop-coating to complete the preparation of the electrochemical sensor.

[0011] A method for preparing a potassium ion sensor based on AuNPs / MXene / SPCE specifically comprises the following steps:

[0012] (1) Preparation of MXene dispersion: Ti3C2 multilayer nanosheets were mixed with ethanol and Nafion solution, and ultrasonic treatment was performed to form a uniform dispersion;

[0013] Furthermore, in the step (1), the MXene material is Ti3C2 multilayer nanosheets, the Nafion solution is Nafion117 perfluorinated resin solution; the mass concentration of MXene in ethanol is 50-200 mg / mL; the mass fraction of Nafion117 perfluorinated resin solution is 5%, and the amount of Nafion117 perfluorinated resin solution per gram of MXene is 20-50 μL; the ultrasonic treatment temperature is 5-15°C, the ultrasonic treatment power is 240W-260W, and the ultrasonic treatment time is 30-60 min;

[0014] (2) Preparation of potassium ion selective membrane solution: valinomycin, potassium tetraphenylborate KB(C6H5)4, polyvinyl chloride PVC, and di(2-ethylhexyl) sebacate DOS were dissolved in cyclohexanone and ultrasonically treated.

[0015] Furthermore, in the step (2), the mass concentrations of valinomycin, potassium tetraphenylborate KB(C6H5)4, di(2-ethylhexyl) sebacate DOS, and polyvinyl chloride PVC in cyclohexanone solvent are 0.71-10 mg / mL, 0.29-1.6 mg / mL, 85.71-140 mg / mL, and 35.71-70 mg / mL, respectively; the ultrasonic treatment temperature is 5-15°C, the ultrasonic treatment power is 240W-260W, and the ultrasonic treatment time is 30-60min.

[0016] (3) Preparation of GO-PVA hydrogel: GO dispersion and PVA solution were mixed and stirred;

[0017] Furthermore, the GO dispersion has a concentration of 0.5-2.52 mg / mL; the PVA solution has a mass concentration of 10-20 wt%; the GO dispersion and PVA solution are mixed in a volume ratio of 0.5:1 to 2:1, and the mixing time is 12-36 hours. The GO dispersion can be purchased directly, or the GO can be dispersed in deionized water by ultrasonic treatment at a temperature of 5-15°C, a power of 240W-260W, and a treatment time of 5-60 minutes. The polyvinyl alcohol (PVA) solution is obtained by dissolving PVA powder in deionized water at 75°C-95°C.

[0018] (4) Activation of screen-printed carbon electrodes: The electrodes were activated in sulfuric acid solution using cyclic voltammetry;

[0019] Furthermore, in step (4), the scanning amplitude is -2.0 V to 2.0 V, the scanning rate is 50-200 mV / s, and the number of cycles is 5-10. The concentration of the sulfuric acid solution is 0.2-0.8 mol / L;

[0020] (5) Modification of MXene layer: MXene dispersion was drop-coated on the surface of activated screen-printed carbon electrode and dried;

[0021] Furthermore, in the step (5), each mm 2 The amount of MXene dispersion on the electrode with an effective working area is 0.12 to 0.32 μL; the drying condition is to dry it at room temperature.

[0022] (6) Electrochemical deposition of AuNPs layer: AuNPs were deposited on the surface of MXene-modified electrode;

[0023] Furthermore, in the step (6), the deposition voltage is -0.4V to -1.6V, the deposition time is 90-210 seconds, and the deposition solution is 0.05 mol / L HAuCl4; per mm 2 The amount of 0.05 mol / L HAuCl4 used on the electrode with an effective working area is 2.43 to 4.85 μL.

[0024] (7) Coating the potassium ion selective membrane: drop-coating the potassium ion selective membrane solution onto the surface of the AuNPs / MXene composite layer and drying;

[0025] Furthermore, in the step (7), each mm 2 The amount of potassium ion selective membrane solution used on the electrode with an effective working area is 0.12-0.32 μL; the shade drying time after drop coating is 10-24 hours.

[0026] (8) Covering with GO-PVA hydrogel layer: GO-PVA hydrogel was drop-coated on the surface of the potassium ion selective membrane and dried.

[0027] Furthermore, in the step (8), each mm 2 The amount of GO-PVA hydrogel applied to the electrode with an effective working area is 0.12 to 0.32 μL; the shade drying time after drop coating is 10 to 24 hours.

[0028] The potassium ion sensor electrodes treated in the above steps need to be stored at room temperature for 10 –4 Soak in mol / L KCl solution overnight.

[0029] Working principle of the present invention:

[0030] According to the different transduction mechanisms of the ion-electron transduction layer, it can be mainly divided into the following two categories: redox capacitance transduction mechanism and double-layer capacitance transduction mechanism.

[0031] Solid transduction layers based on the redox capacitive transduction mechanism also achieve ion-electron transduction through redox reactions between the polymer ion-selective membrane and the solid conductive substrate. Taking the conducting polymer transduction layer as an example, the redox reactions that occur during the transduction process are mainly:

[0032]

[0033] Where CP stands for conductive polymer, A – represents the doped anion in the conductive polymer, M + represents the main ion to be measured, R – represents the ionic site in the polymer membrane, and L represents the ion carrier.

[0034] As for the transduction mechanism of the double-layer capacitance used in this experiment, an ion-electron transduction layer with a large double-layer capacitance is introduced between the polymer ion-selective membrane and the solid conductive substrate, which can accelerate the ion-electron conversion rate between the polymer membrane and the conductive substrate and make the interface potential between the two stable.

[0035] Gold nanoparticles have excellent double-layer capacitance, and MXene materials can provide a larger surface area for gold nanoparticles to be deposited on electrodes. Furthermore, the interlayer channels of MXene promote ion diffusion, enhancing signal response and further accelerating ion-electron conversion, thus improving sensor performance.

[0036] Screen printing technology primarily involves printing and firing various pastes onto a flat ceramic or plastic substrate. Commercially available carbon and platinum pastes are used to print the working electrode, while silver / silver chloride pastes are used to print the reference electrode. Carbon paste is a commonly used paste for printing sensors due to its low cost, low background current, and electrical stability over a wide potential range.

[0037] Through the screening of the potassium ion selective membrane, potassium ions in sweat diffuse into the transduction layer of the sensor and form a potential difference between the working electrode and the reference electrode. This potential difference can be transmitted through the Ag electrode to the subsequent voltage acquisition circuit for processing and read out through other methods, thereby achieving the purpose of obtaining the potassium ion concentration in sweat by reading the voltage.

[0038] Beneficial effects of the present invention:

[0039] (1) The present invention adopts the drop coating method and electrochemical deposition method to obtain a composite material of a two-dimensional material (MXene) and a nanomaterial (AuNPs) on a screen-printed carbon electrode. The material properties are stable and efficient, and the preparation process is simple. It is a sensor preparation scheme with a simple process flow and easy optimization.

[0040] (2) The screen-printed carbon electrode prepared by the present invention, which has a potassium ion-selective membrane and is modified with AuNPs / MXene, allows only potassium ions in sweat to pass through the selective membrane, thereby improving the selectivity of the sensor. Furthermore, the application of the AuNPs / MXene composite material greatly increases the surface area-to-volume ratio of the screen-printed carbon electrode, allowing more potassium ions to participate in ion-electron conversion, thereby improving the sensitivity of the sensor and expanding its detection range.

[0041] (3) Based on the potassium ion selective membrane and AuNPs / MXene modification of the screen-printed carbon electrode, the present invention adds a layer of GO-PVA hydrogel, which enhances the mechanical strength and lifespan of the potassium ion selective membrane, delays the aging and shedding of the potassium ion selective membrane during use, and makes the sensor performance more stable. In addition, it effectively prevents the leakage of valinomycin in the potassium ion selective membrane from causing allergies or poisoning to the user, making the sensor suitable for long-term application in health testing and medical care. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a scanning electron microscope microscopic morphology image (10K) of the AuNPs / MXene composite layer of the present invention.

[0043] Figure 2 This is a scanning electron microscope microscopic morphology image (10K) of the GO-PVA hydrogel layer of the present invention.

[0044] Figure 3 This is a schematic diagram of the structure of the present invention, in which: 1: GO-PVA hydrogel; 2: potassium ion selective membrane; 3: gold nanoparticles (AuNPs) layer; 4: MXene (Ti3C2) layer; 5: screen-printed carbon electrode (counter electrode); 6: screen-printed carbon electrode (working electrode); 7: screen-printed silver electrode (reference electrode); 8: ceramic substrate.

[0045] Figure 4 Cyclic voltage gradient characterization test for the sensor.

[0046] Figure 5 This is the cyclic voltage gradient linearity test of the sensor.

[0047] Figure 6 This is the open circuit voltage test of the sensor.

[0048] Figure 7 This is the relationship diagram between potassium ion concentration and open circuit voltage of the sensor.

[0049] Figure 8 This is the electrochemical impedance spectroscopy test diagram of modified MXene / AuNPs materials and ion-selective membranes.

[0050] Figure 9 These are the electrochemical impedance spectroscopy test diagrams of a bare screen-printed carbon electrode, an electrode modified with only MXene material, and an electrode modified with only MXene / AuNPs.

[0051] Figure 10 The results of cyclic voltammetry (CV) characterization of the sensor. DETAILED DESCRIPTION

[0052] In order to further illustrate the present invention, the present invention is described in detail below in conjunction with embodiments, but they should not be understood as limiting the scope of protection of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0053] Unless otherwise specified, the test methods in the following examples are conventional methods.

[0054] Main materials / equipment and sources:

[0055]

[0056] Main equipment:

[0057]

[0058] Example 1:

[0059] (1) Use an electronic balance to measure 100 mg of MXene material and transfer it to a centrifuge tube. Measure 1 mL of 99.7% pure ethanol and add it to the centrifuge tube containing the MXene material. Measure 3 μL of 5% mass fraction Nafion solution and add it to the centrifuge tube containing the MXene material and ethanol. Ultrasonic treatment is performed for 30 minutes at an ultrasonic treatment power of 250 W and an ultrasonic temperature of 10°C to obtain a uniform MXene dispersion without precipitation. Seal it at 4°C for later use.

[0060] (2) Use an electronic balance to measure 2 mg of valinomycin, 0.5 mg of KB(C6H5)4, 32.7 mg of PVC, and 64.7 mg of DOS, respectively, and completely dissolve them in 660 μL of cyclohexanone solvent. Note that valinomycin, KB(C6H5)4, and DOS should be dissolved first and stirred to make them fully and evenly dissolved (not less than 5 minutes), and the PVC powder should be dissolved last. The mixed solution is then ultrasonically treated for 40 minutes at an ultrasonic treatment power of 250 W and an ultrasonic temperature of 10°C to obtain a potassium ion selective membrane solution, which is then sealed at 4°C for later use.

[0061] (3) Use an electronic balance to measure 5 mg of GO, transfer it to a centrifuge tube, add 5 mL of deionized water to dissolve it, and ultrasonically treat the solution at an ultrasonic power of 250 W and an ultrasonic temperature of 10°C for 30 min to obtain a GO dispersion. Then, evaporate the dispersion to a concentration of 2 mg / mL and seal it at 4°C for later use. A GO dispersion with a concentration of 2 mg / mL can also be purchased directly.

[0062] (4) Use an electronic balance to measure 1 g of PVA powder and transfer it to a measuring cup. Add 9 mL of deionized water to dissolve it. Place the measuring cup in a constant temperature magnetic stirrer and stir at 85 °C for 2 h (stirring speed is 450 rpm) until the PVA powder is completely dissolved and there is no precipitation at the bottom of the measuring cup. Cool it naturally and seal it. Store it at 4 °C for later use.

[0063] (5) The GO dispersion prepared in step (3) was ultrasonically treated at an ultrasonic power of 250 W and an ultrasonic temperature of 10° C. for 10 min. The PVA solution prepared in step (4) and the GO dispersion were then mixed in a volume ratio of 1:1 and stirred for 12 h until a uniform GO-PVA hydrogel was obtained. The mixture was sealed at 4° C. for later use.

[0064] (6) Take a bare screen-printed carbon electrode with a working electrode diameter of 4 mm (Metrohm 110 type) and connect it to the electrochemical workstation. Use a pipette to take 50 μL of 0.5 mol / L sulfuric acid solution and drop it onto the surface of the screen-printed carbon electrode, evenly covering the working electrode, counter electrode and reference electrode. Select the cyclic voltammetry mode, set the scan amplitude to -2.0 V-2.0 V, the number of scan cycles to 8 cycles, and the scan rate to 100 mV. Start activating the electrode, rinse the activated electrode, and seal it in a cool place for later use.

[0065] (7) Use a pipette to measure 3 μL of the MXene dispersion prepared in step (1), and evenly apply it to the working electrode surface of the finished screen-printed carbon electrode three times and dry it at room temperature. Seal the electrode modified with MXene material in a cool place for later use.

[0066] (8) Connect the screen-printed carbon electrode of the MXene material modified in step (7) to the electrochemical workstation, use a pipette to measure 50 μL of 0.05 mol / L HAuCl4 solution and drop it onto the surface of the screen-printed carbon electrode, evenly covering the working electrode, counter electrode and reference electrode, select the electrochemical workstation working mode as electrochemical deposition, set the deposition voltage to -1.2 V, the deposition time to 150 s and start deposition, and seal the electrode modified with AuNPs in a cool place for use.

[0067] (9) Use a pipette to measure 3 μL of the potassium ion selective membrane solution prepared in step (2), and evenly apply it to the working electrode surface of the printed carbon electrode modified with AuNPs / MXene material obtained in step (8) in three times, and dry it in the shade at room temperature for 18 hours. The electrode with the modified potassium ion selective membrane is sealed in a cool place for use.

[0068] (10) Use a pipette to measure 3 μL of the GO-PVA hydrogel prepared in step (5) and evenly apply it three times to the working electrode surface of the screen-printed carbon electrode modified with the potassium ion selective membrane and AuNPs / MXene material in step (9), and dry it in the shade at room temperature for 18 h. The electrode modified with GO-PVA hydrogel is sealed in a cool place for later use.

[0069] Example 2:

[0070] The preparation method is the same as that in Example 1, except that the magnetic stirring temperature and time in step (4) of Example 1 are changed to 90°C and 1 h, and the volume ratio of PVA solution to GO dispersion in step (5) is changed to 1:1.5; the conditions of step (6) are changed to: scanning amplitude of -2.0 V to 1.5 V, the number of scanning cycles is 6 cycles, and the scanning rate is 200 mV; the deposition voltage in step (8) is changed to -1.4 V, and the deposition time is changed to 120 s;

[0071] Example 3;

[0072] The preparation method is the same as that of Example 1, except that the mass fraction of 5% Nafion solution in step (1) of Example 1 is changed to 4 μL, and the volume ratio of PVA solution and GO dispersion in step (5) is changed to 1.5:1.

[0073] Example 4: CV gradient characterization test of sensor

[0074] Figure 4 Cyclic voltage gradient characterization test of the sensor prepared in Example 1, Figure 5 This is a cyclic voltage gradient linearity test of the sensor prepared in Example 1.

[0075] The working solution used was a mixed solution of 0.1 mol / L KCl and 5 mmol / L K3[Fe(CN)6] and K4[Fe(CN)6]. The electrochemical workstation was set to CV mode with a potential range of -0.2 V to 0.4 V. The initial direction of the potential scan was forward scanning. The scan rate increased from 0.01 V / s to 0.19 V / s with an increment of 0.02 V / s. The number of scans was 4 and the sensitivity was 10. - 4 A / V.

[0076] Figure 4 and 5 The peak current of the oxidation and reduction reactions increases significantly with the increase of the scan rate. For the reversible electron transfer process of electrochemical reactions involving freely diffusing redox species, the Randles-Sevcik equation describes the peak current Ip (A) as the scan rate ν increases. 1 / 2 The Randles-Sevcik equation can be used to determine whether the reaction is diffusion-controlled and whether the reactants diffuse freely in the solution or undergo adsorption. Since reactants sometimes adsorb to the electrode surface, it is important to assess whether the reactants remain uniform in the solution before analyzing their reactivity. The Randles-Sevcik equation can also be used to calculate the diffusion coefficient.

[0077]

[0078] Where,

[0079] F: Faraday constant;

[0080] n: the number of electrons transferred during the redox process;

[0081] A: electrode area, generally the geometric area;

[0082] C: concentration of ions involved in the reaction;

[0083] D: diffusion coefficient;

[0084] v: Scan rate set for cyclic voltammetry.

[0085] The linear relationship between the oxidation and reduction peak currents and the square root of the scan rate is consistent with the theoretical model described by the Randles-Sevcik equation, further demonstrating the electrochemical performance of the MXene / AuNPs / SPCE-based potassium ion sensor and indicating that the modified electrode is suitable for various electrochemical applications.

[0086] Example 5:

[0087] Open circuit voltage characterization test of sensors

[0088] Figure 6 This is the open circuit voltage method (OCPT) characterization test diagram of the sensor prepared in Example 1. Figure 7 This is a graph showing the relationship between the solution potassium ion concentration and the open circuit voltage of the sensor prepared in Example 1.

[0089] The working solution used was KCl solution. The working mode of the electrochemical workstation was selected as OCPT, the operating time was set to 300 s, the sampling interval was set to 0.1 s, the high potential limit was set to 1 V, and the low potential limit was set to -1 V.

[0090] Measure 15 mL of deionized water into a measuring cup and place it on a constant temperature magnetic stirrer. Set the temperature to 22°C and the speed to 250 rpm.

[0091] Add 5 μL of 3 mol / L KCl solution to deionized water to obtain a 1 mmol / L KCl solution, completely immerse the modified sensor electrode in the 1 mmol / L KCl solution, wait for the KCl solution to be fully mixed, start testing the open circuit voltage for 50 seconds; then add 5 μL of 3 mol / L KCl solution to the measuring cup containing 1 mmol / L KCl solution to obtain a 2 mmol / L KCl solution, wait for the KCl solution to be fully mixed, continue testing the open circuit voltage for 50 seconds; then add 10 μL of 3 mol / L KCl solution to the measuring cup containing 2 mmol / L KCl solution to obtain a 4 mmol / L KCl solution, wait for the KCl solution to be fully mixed, continue testing the open circuit voltage for 50 seconds; then add 10 μL of 3 mol / L KCl solution to the measuring cup containing 2 mmol / L KCl solution to obtain a 4 mmol / L KCl solution, wait for the KCl solution to be fully mixed, continue testing the open circuit voltage for 50 seconds; Add 20 μL of 3 mol / L KCl solution to the measuring cup containing 4 mmol / L KCl solution to obtain 8 mmol / L KCl solution. After the KCl solution is fully mixed, continue to test the open circuit voltage for 50 seconds; then add 40 μL of 3 mol / L KCl solution to the measuring cup containing 8 mmol / L KCl solution to obtain 16 mmol / L KCl solution. After the KCl solution is fully mixed, continue to test the open circuit voltage for 50 seconds; finally, add 80 μL of 3 mol / L KCl solution to the measuring cup containing 16 mmol / L KCl solution to obtain 32 mmol / L KCl solution. After the KCl solution is fully mixed, continue to test the open circuit voltage until the timing ends to obtain the open circuit voltage characterization test of the sensor. Figure 6 .

[0092] In the OCPT characterization system, E is the ion selective electrode potential, E PB is the sum of the potentials generated at the AuNPs / MXene transduction layer-solution interface, i.e., the phase boundary potential, E const is the indicator electrode except for all other potentials of the phase interface potential (this potential change is negligible), then the following relationship exists <4> , under thermodynamic equilibrium conditions, the formula can be derived through further evolution <6> , that is, the potential of the ion selective electrode and the target ion activity in the test solution satisfy the Nernst equation:

[0093] E=E const +E PB <4>

[0094]

[0095] Where,

[0096] R: gas constant;

[0097] T: absolute temperature;

[0098] F: Faraday constant;

[0099] z: ion charge number;

[0100] a1(aq): activity of the ion to be measured in the aqueous phase;

[0101] a1(org): activity of the ion to be measured in the organic (membrane) phase;

[0102] Take the logarithm of the concentration of KCl solution 10 [(K + )mmol / L] as the horizontal axis, and the average value of the open circuit voltage at the corresponding concentration as the vertical axis, to obtain the corresponding relationship between potassium ion concentration and open circuit voltage Figure 7 By fitting, the formula <6> The sensor sensitivity is 0.097 octave.

[0103] Example 6:

[0104] Electrochemical impedance spectroscopy characterization test of sensors

[0105] Figure 8 This is the electrochemical impedance spectroscopy test diagram of the electrode modified with MXene / AuNPs material and ion-selective membrane prepared in steps (1)-(9) of Example 1. Figure 9 These are the electrochemical impedance spectroscopy test graphs of the bare screen-printed carbon electrode, the electrode modified with only MXene material prepared in steps (1)-(7) of Example 1, and the electrode modified with only MXene / AuNPs prepared in steps (1)-(8) of Example 1.

[0106] The working solution used was (0.1 mol / L KCl and 5 mmol / L K3[Fe(CN)6] and K4[Fe(CN)6] mixed solution). The electrochemical workstation was set to IMP-AC mode. The open circuit voltage of the electrode was first measured and used as the initial voltage. The maximum frequency was set to 100,000 Hz, the minimum frequency was set to 0.1 Hz, the amplitude was set to 0.005 V, and the silent time was set to 2 seconds. The test was started and the results were obtained. Figure 8 and Figure 9 .

[0107] Electrochemical impedance spectroscopy characterized the layer-by-layer modification process of the electrode in a mixed solution of 0.1 mol / L KCl and 5 mmol / L K3[Fe(CN)6] and K4[Fe(CN)6]. The charge transfer resistance (Rct) of the electrode modified with AuNPs / MXene (called AuNPs / MXene electrode) was lower than that of the carbon electrode, indicating that the deposited AuNPs can accelerate the electron transfer efficiency. When further modified with K +When the membrane is selected, Rct becomes higher, indicating that the ion-selective membrane is not a conductive material and is equivalent to an ion detector.

[0108] Example 7: Cyclic voltage characterization test of sensor

[0109] Figure 10 These are the cyclic voltammetry (CV) characterization results of the electrode modified only with MXene / AuNPs prepared in steps (1)-(8) of Example 1.

[0110] The working solution used was a mixed solution of 0.1 mol / L KCl and 5 mmol / L K3[Fe(CN)6] and K4[Fe(CN)6]. The electrochemical workstation was set to CV mode with a potential range of -0.2 V to 0.4 V, a forward scan direction, a scan rate of 0.05 V / s, 8 scan cycles, and a sensitivity of 10. -4 A / V.

[0111] Because cyclic voltammetry experiments were performed under static conditions, convection effects did not contribute to the mass transfer of the electroactive species. Furthermore, due to the high concentration of the supporting electrolyte (0.2 M KCl), migration effects were negligible. Therefore, diffusion effects dominated the mass transfer of the electroactive species to the electrode-solution interface. Under these conditions, the peak current of the cyclic voltammetry can be derived from the Randles–Sevcik equation:

[0112]

[0113] Where,

[0114] i p : Peak current;

[0115] n: number of electrons transferred in the redox reaction;

[0116] F: Faraday constant;

[0117] R: gas constant;

[0118] T: temperature;

[0119] D: diffusion coefficient;

[0120] V: scanning rate;

[0121] A: electrode area;

[0122] C: volume concentration.

[0123] In the positive scan from -0.2V to 0.4V, ferricyanide ion (Fe(CN)6 3- ) gains an electron and is reduced to ferrocyanide ion (Fe(CN)6 4-), generating a reduction peak at a certain potential. The reduction current decays exponentially due to the consumption of ferricyanide ions near the electrode-solution interface. Similarly, during the positive scan from a negative voltage, between -0.2 and 0.4 V, previously accumulated ferrocyanide ions lose electrons and are oxidized to ferricyanide ions, generating an oxidation peak at a certain potential. The oxidation current also follows an exponential decay similar to the aforementioned reduction step.

[0124]

[0125] Therefore, the gold nanoparticle coverage area on the working electrode can be calculated by comparing the peak current ratio:

[0126]

[0127] Where,

[0128] i1: reduction peak current of the modified electrode in CV test;

[0129] i2: reduction peak current of bare electrode in CV test;

[0130] d: Diameter of the working electrode of the screen-printed carbon electrode.

[0131] The average value of A was calculated by taking multiple groups of values ​​in Origin, and the effective coverage area of ​​the modified electrode gold nanoparticles was 18.148 mm 2 , the working electrode area of ​​bare screen-printed carbon electrode is 12.566mm 2 Under the same deposition conditions, gold nanoparticles were directly deposited onto the bare screen-printed carbon electrode working electrode, with an effective coverage area of ​​17.891 mm 2 .

Claims

1. A potassium ion sensor based on AuNPs / MXene / SPCE, characterized in that: The AuNPs / MXene / SPCE-based potassium ion sensor includes a screen-printed carbon electrode SPCE, a MXene layer modified on the surface of the working electrode of the screen-printed carbon electrode, a gold nanoparticle AuNPs layer formed on the surface of the MXene layer by electrochemical deposition, a potassium ion selective membrane covering the gold nanoparticle AuNPs layer, and a GO-PVA hydrogel layer coated on the surface of the potassium ion selective membrane.

2. The potassium ion sensor based on AuNPs / MXene / SPCE according to claim 1, characterized in that: The potassium ion selective membrane comprises valinomycin, potassium tetraphenylborate KB(C6H5)4, polyvinyl chloride PVC and di(2-ethylhexyl) sebacate DOS.

3. The method for preparing a potassium ion sensor based on AuNPs / MXene / SPCE according to any one of claims 1-2, characterized in that: The MXene material is drop-coated on the surface of the finished screen-printed carbon electrode to obtain the MXene / SPCE electrode, and then a layer of gold nanoparticles is deposited on the MXene / SPCE electrode by electrochemical deposition to obtain the AuNPs / MXene / SPCE electrode. Then, the potassium ion selective membrane is modified onto the AuNPs / MXene / SPCE electrode by drop-coating. Finally, the GO-PVA hydrogel is covered on the electrode surface modified with the potassium ion selective membrane by drop-coating to complete the preparation of the electrochemical sensor.

4. The method for preparing a potassium ion sensor based on AuNPs / MXene / SPCE according to claim 3, wherein: The specific steps include: (1) Preparation of MXene dispersion: Ti3C2 multilayer nanosheets were mixed with ethanol and Nafion solution, and ultrasonic treatment was performed to form a uniform dispersion; (2) Preparation of potassium ion selective membrane solution: dissolving valinomycin, potassium tetraphenylborate KB(C6H5)4, polyvinyl chloride PVC, and di(2-ethylhexyl) sebacate DOS in cyclohexanone and ultrasonically treating; (3) Preparation of GO-PVA hydrogel: GO dispersion and PVA solution were mixed and stirred; (4) Activation of screen-printed carbon electrodes: The electrodes were activated in sulfuric acid solution using cyclic voltammetry; (5) Modification of MXene layer: MXene dispersion was drop-coated on the surface of activated screen-printed carbon electrode and dried; (6) Electrochemical deposition of AuNPs layer: AuNPs were deposited on the surface of MXene-modified electrode; (7) Coating the potassium ion selective membrane: drop-coating the potassium ion selective membrane solution onto the surface of the AuNPs / MXene composite layer and drying; (8) Covering with GO-PVA hydrogel layer: GO-PVA hydrogel was drop-coated on the surface of the potassium ion selective membrane and dried.

5. The method for preparing a potassium ion sensor based on AuNPs / MXene / SPCE according to claim 4, wherein: In the step (1), the MXene material is Ti3C2 multilayer nanosheets, the Nafion solution is Nafion117 perfluorinated resin solution; the mass concentration of MXene in ethanol is 50-200 mg / mL; the mass fraction of Nafion117 perfluorinated resin solution is 5%, and the amount of Nafion117 perfluorinated resin solution per gram of MXene is 20-50 μL; the ultrasonic treatment temperature is 5-15°C, the ultrasonic treatment power is 240W-260W, and the ultrasonic treatment time is 30-60 min.

6. The method for preparing a potassium ion sensor based on AuNPs / MXene / SPCE according to claim 4, wherein: In the step (2), the mass concentrations of valinomycin, potassium tetraphenylborate KB(C6H5)4, di(2-ethylhexyl) sebacate DOS, and polyvinyl chloride PVC in cyclohexanone solvent are 0.71-10 mg / mL, 0.29-1.6 mg / mL, 85.71-140 mg / mL, and 35.71-70 mg / mL, respectively; the ultrasonic treatment temperature is 5-15°C, the ultrasonic treatment power is 240W-260W, and the ultrasonic treatment time is 30-60min.

7. The method for preparing a potassium ion sensor based on AuNPs / MXene / SPCE according to claim 4, wherein: In the step (3), the concentration of the GO dispersion is 0.5-2.52 mg / mL; the mass concentration of the PVA solution is 10-20 wt%; the GO dispersion and the PVA solution are mixed in a volume ratio of 0.5:1 to 2:1, and the mixing time is 12-36 hours; the GO dispersion can be purchased directly, or the GO is dispersed in deionized water by ultrasonic treatment, the ultrasonic treatment temperature is 5-15 ° C, the ultrasonic treatment power is 240W-260W, and the ultrasonic treatment time is 5-60min; the polyvinyl alcohol PVA solution is obtained by dissolving PVA powder in deionized water at 75 ° C to 95 ° C.

8. The method for preparing a potassium ion sensor based on AuNPs / MXene / SPCE according to claim 4, wherein: In the step (4), the scanning amplitude is -2.0V to 2.0V, the scanning rate is 50-200mV / s, and the number of cycles is 5-10 times; the concentration of the sulfuric acid solution is 0.2-0.8mol / L; in the step (5), each mm 2 The amount of MXene dispersion on the electrode with an effective working area is 0.12 to 0.32 μL; the drying condition is to dry it at room temperature.

9. The method for preparing a potassium ion sensor based on AuNPs / MXene / SPCE according to claim 4, wherein: In the step (6), the deposition voltage is -0.4V to -1.6V, the deposition time is 90-210 seconds, and the deposition solution is 0.05 mol / L HAuCl4; per mm 2 The amount of 0.05 mol / L HAuCl4 used on the electrode with an effective working area is 2.43 to 4.85 μL.

10. The method for preparing a potassium ion sensor based on AuNPs / MXene / SPCE according to claim 4, wherein: In the step (7), each mm 2 The amount of potassium ion selective membrane solution on the electrode with effective working area is 0.12-0.32 μL; the shade drying time after drop coating is 10-24 hours; in the step (8), each mm 2 The amount of GO-PVA hydrogel applied to the electrode with an effective working area is 0.12 to 0.32 μL; the shade drying time after drop coating is 10 to 24 hours.

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