A method for fabricating and applying a miniaturized potentiometric ion sensor

Abstract

This invention relates to electrochemical sensors, specifically a miniaturized potentiometric ion sensor, its fabrication method, and its applications. The potentiometric ion sensor comprises an electrode substrate, an ion-electron transduction layer, and an ion-selective polymer film; wherein the ion-electron transduction layer is formed of a redox-type solid transduction layer material. The ion-electron transduction material used in this invention possesses high specific capacitance and redox activity, which is beneficial for improving electrode stability. Compared to the electrode size of glassy carbon electrodes, the sensor fabricated in this invention is relatively smaller in size, and can be used not only for water sample detection but also for the detection of free ions in plant matter.

Description

Technical Field

[0001] This invention relates to electrochemical sensors, specifically a miniaturized potential-type ion sensor, its preparation method, and its application. Background Technology

[0002] Potentiometric electrochemical sensors are an important class of electrochemical sensors. They convert the chemical signal of the analyte into an electrical signal under zero-current conditions, thus avoiding interference from the analyte during the testing process. Potentiometric electrochemical sensors consist of an electrode substrate, an ion-electron transduction layer material, and an ion-selective polymer membrane. Originating in the 1960s, their detection principle is based on the relationship between the potential response of the ion-selective membrane and the activity of the analyte ions, which conforms to the Nernst equation. They are now widely used in clinical testing, environmental analysis, and process control. With the continuous expansion of analytical application demands, the miniaturization and micro-miniaturization of potentiometric sensors is an important development trend.

[0003] Printed electrodes have advantages such as being thin, flexible, and environmentally friendly, which can initially meet the needs of the miniaturization development of electrochemical sensors. Currently, the solid-state transconducting materials used in ion-selective electrodes constructed based on this type of electrode are mostly the following: (1) carbon materials (graphene, carbon nanotubes, and carbon black); (2) conductive polymers and their derivatives; (3) metals and metal oxides. However, the potential stability of this type of electrode needs to be further improved mainly because the capacitance value of the solid-state transconducting layer material used is relatively low.

[0004] The potential stability and lifespan of electrodes are crucial for obtaining reliable and comprehensive analytical data on the flux of heavy metal ions in plant rhizosphere. The ion-electron transduction layer material, located between the ion-selective membrane and the conductive substrate, not only functions as an ion-electron transducer but also provides a stable interfacial potential for the electrode. Its performance is a key factor affecting the stability of all-solid-state ion-selective microelectrodes. Therefore, obtaining a highly stable miniaturized potential-type ion sensor is a significant challenge. It should be noted that the sensor's stability is primarily related to the specific capacitance of the ion-electron transduction material; therefore, the key to improving the potential stability of all-solid-state ion-selective electrodes lies in developing materials with high stability and theoretical specific capacitance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to construct a miniaturized potential-type ion sensor, its preparation method and application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A miniaturized potentiometric ion sensor is disclosed, comprising an electrode substrate, an ion-electron transduction layer, and an ion-selective polymer film; wherein the ion-electron transduction layer is formed of a redox solid transduction layer material.

[0007] The redox solid transducer material is iron-cobalt sulfide.

[0008] The sulfide is a hollow nanotube iron-cobalt sulfide synthesized from copper nitrate, cobalt nitrate, ammonium fluoride, urea and sodium sulfide as raw materials, with a molar ratio of (1~10):(1~10):(2~20):(10~100):(10~100).

[0009] The sulfide is obtained by dissolving cobalt nitrate, copper nitrate, ammonium fluoride and urea in a mixed solution of water and ethanol according to the above molar ratio, and reacting the resulting solution at 100℃-160℃ for 10-16h to obtain a precursor; then placing it in an aqueous solution of sodium sulfide and continuing to react at 100℃-160℃ for 10-24h to obtain sulfide nanomaterials.

[0010] A method for preparing a miniaturized potential-type ion sensor involves drop-coating a sulfide onto the surface of an electrode substrate as an ion-electron transduction layer. After drying, an ion-selective membrane precursor is drop-coated onto the ion-electron transduction layer to form an ion-selective membrane, thereby obtaining a miniaturized potential-type ion sensor.

[0011] The ion-selective membrane is composed of an ion support, tetra(4-chlorophenyl)borate tetradodecylammonium, polyvinyl chloride, and di-n-octyl sebacate, dissolved in tetrahydrofuran and stirred evenly to obtain the corresponding ion-selective polymer membrane; wherein the mass ratio of the ion support, tetradodecylammonium tetra(4-chlorophenyl)borate, polyvinyl chloride, and di-n-octyl sebacate is 0.5-1.0:0.5-1.0:17-34:32.5-65.

[0012] The ion carrier is one or more of the following: calcium ions, hydrogen ions, sodium ions, potassium ions, nitrate ions, chloride ions, etc.

[0013] Furthermore, taking a screen-printed electrode as the substrate and nitrate ions as the ion carrier as an example, firstly, a redox-type solid transduction layer material is dispersed and dropped onto the surface of the screen-printed electrode. After drying, a printed electrode loaded with an ion-electron transduction layer is obtained. Then, a nitrate ion-selective polymer film is drop-coated onto the surface of the ion-electron transduction layer and dried in a constant temperature and humidity chamber to obtain a miniaturized potential-type ion sensor.

[0014] An application of the miniaturized potentiometric ion sensor described above, specifically its use in the detection of free ions in the environment.

[0015] The environment refers to water bodies, plants, animals, or food. Compared with the prior art, the present invention has the following beneficial effects: This invention employs iron-cobalt sulfide as the ion-electron transduction layer in the sensor, which possesses high theoretical specific capacitance (1000~3000 F / g), good physical and chemical properties, high conductivity, and stability. This material meets the requirements for solid-state transduction layers in miniaturized potential-type ion sensors, and its related electrochemical properties have reliable theoretical and practical basis, specifically: 1. This invention relates to a potential-type ion sensor using sulfides as solid-state transducer materials. These materials provide transducer materials with high theoretical specific capacitance, which can improve electrode stability.

[0016] 2. The miniaturized potential-type ion sensor of the present invention has good selectivity and anti-interference characteristics.

[0017] 3. The miniaturized potentiometric ion sensor constructed in this invention can be used for rapid and sensitive detection of nitrate ions in plants; by changing the membrane composition of the ion-selective membrane, the detection of multiple ions can be achieved. Attached Figure Description

[0018] Figure 1 The images shown are scanning electron microscope (SEM) images of FeCo2S4 prepared according to embodiments of the present invention. In these images, A is a scanning electron microscope image of FeCo2S4, B is an elemental distribution map of Fe, C is an elemental distribution map of Co, and D is an elemental distribution map of S.

[0019] Figure 2 The X-ray diffraction pattern of FeCo2S4 prepared in an embodiment of the present invention.

[0020] Figure 3 The image shows the effect of the miniaturized potential-type ion sensor based on FeCo2S4 according to an embodiment of the present invention; where A is the potential response curve and B is the corresponding calibration curve.

[0021] Figure 4 The figure shows the stability test results of the miniaturized potentiometric ion sensor based on FeCo2S4 according to an embodiment of the present invention.

[0022] Figure 5 The figure shows the effect of light on the potential stability of a miniaturized potential-type ion sensor based on FeCo2S4 according to an embodiment of the present invention. Detailed Implementation

[0023] The following examples further illustrate specific embodiments of the present invention. It should be noted that the specific embodiments described herein are merely for illustration and explanation and are not intended to limit the scope of protection of the present invention.

[0024] The miniaturized potentiometric ion sensor of this invention uses sulfide nanomaterials with large specific capacitance, good conductivity, and redox activity as ion-electron transduction materials, which can improve the stability of the electrode and be applied to the detection of free ions in plants.

[0025] The sulfide nanomaterials were prepared using a solvothermal method. Based on the synergistic effect of bimetallic sulfides and the structure of hollow nanotubes, the sulfides exhibit excellent conductivity and high theoretical specific capacitance, which is beneficial for improving electrode stability. The prepared sulfides were then dispersed in an ethanol solution and drop-coated onto a substrate to obtain a sulfide-loaded electrode. Finally, an ion-selective film was drop-coated onto the printed electrode to fabricate a miniaturized potentiometric ion sensor. This miniaturized potentiometric ion sensor will be used for the detection of free ions in the environment.

[0026] Example 1: Preparation of FeCo2S4 as a solid-state transduction layer material for a miniaturized potentiometric ion sensor.

[0027] Weigh out 1.0 mmol of ferric chloride hexahydrate, 2.0 mmol of cobalt chloride hexahydrate, 5.0 mmol of urea, and 4.0 mmol of NH4F, and dissolve them in water using ultrasonication. Then, transfer the solution to a polytetrafluoroethylene (PTFE) reactor and react at 120 °C for 12 h. After the reaction, allow the reactor to cool naturally to room temperature, and wash five times with water and ethanol by centrifugation to obtain an intermediate. Then, react the intermediate with 35 mL of 0.25 M Na2S aqueous solution at 160 °C for another 12 h; after the reaction, the product FeCo2S4 is obtained (see [link to product description]). Figure 1 and 2 ).

[0028] Depend on Figure 1 The morphology and elemental characterization of FeCo2S4 are shown in the examples, which were observed under a scanning electron microscope. Figure 1 As shown in Figure A, the synthesized FeCo2S4 nanomaterial exhibits a hollow rod-like morphology. This nanostructure increases the specific surface area of ​​the transconducting layer, which is beneficial for improving the capacitance value and facilitating the construction of a highly stable ion-selective electrode. Elemental distribution analysis confirms that the synthesized material contains Fe, Co, and S (BD). X-ray powder diffraction (XRD) analysis revealed that the XRD diffraction peaks of the synthesized material at 19.0°, 26.6°, 31.3°, 38.01°, 46.4°, 50.2°, and 55.13° correspond to the characteristic peaks of FeCo2S4 (PDF-42-1450). Therefore, the synthesized nanomaterial is identified as FeCo2S4.

[0029] Example 2: Preparation of nitrate ion selective membrane.

[0030] Weigh 32.70 wt% PVC (polyvinyl chloride), 1.00 wt% ETH500 [tetra(4-chlorophenyl)borate tetradodecylammonium], 1.00 wt% nitrate ion carrier and 65.30 wt% DOS (dioctyl sebacate), mix them in the above proportions to make the total amount of solute 200 mg, then dissolve them in 2.0 mL tetrahydrofuran and stir well to obtain the nitrate ion selective polymer membrane precursor solution.

[0031] Example 3: Preparation of a printed electrode loaded with FeCo2S4.

[0032] 30 mg of the nanostructured FeCo2S4 prepared in Example 1 was dispersed in 0.75 mL of anhydrous ethanol solution and sonicated for 30 min to obtain a uniform dispersion. Then, the dispersion was drop-coated onto the surface of a printed electrode and dried (by baking under an infrared lamp) to obtain a uniform and dense ion-electron transduction layer. Finally, 30 μL of the nitrate ion-selective polymer film precursor prepared in Example 2 was drop-coated onto the surface of the above-mentioned printed electrode ion-electron transduction layer and dried overnight in a constant temperature and humidity chamber at 25 ℃ to obtain a miniaturized potentiometric nitrate ion sensor.

[0033] Example 4: Experimental case of potential response of miniaturized potential-type nitrate ion sensor.

[0034] Based on the miniaturized potentiometric nitrate ion sensor obtained in Example 3, at 10 -3 The electrode was activated in a KNO3 solution. The activated electrode was then used to detect nitrate ions in the solution, and the corresponding potential-time curve and correction (logarithm of activity versus potential) curve were obtained. (See attached image.) Figure 3 .

[0035] The tested nitrate concentration was 10. -8 M, 10 -7 M, 10 -6 M, 10 -5 M, 10 -4 M, 10 -3 M, 10 -2 M and 10 -1 M. By Figure 3 As can be seen from curve A, the electrode exhibits a fast and stable potential response. From Figure 3 B indicates that the electrode operates at a potassium nitrate concentration of 10... -8 -10 -1 M exhibits a Nernst response in aqueous solution with a slope of -62.3 ± 3.8 mV / dec (n = 5), and the linear range of the Nernst response is 10.-1 - 10 -5 M, the detection limit of the electrode is 1.0 × 10⁻⁶. -6 mol L -1 The results show that this electrode can be used for the detection of nitrate ions in real samples.

[0036] Example 5: Stability test of miniaturized potential-type nitrate ion sensor.

[0037] Based on the stability of the miniaturized potentiometric nitrate ion sensor obtained in Example 3, specifically its short-term stability was characterized by chronopotentiometric analysis. Figure 4 The timing potential comparison diagram is shown.

[0038] Depend on Figure 4 As can be seen, the introduction of the FeCo2S4 transconductance layer resulted in a low potential drift of only 18.2 μV s in the electrode. -1 This can improve the stability of the electrode potential.

[0039] Example 6: Experimental case of miniaturized potential-type nitrate ion sensor resisting light interference.

[0040] Based on the miniaturized potentiometric nitrate ion sensor obtained in Example 3, the effect of switching the light source on the sensor's electrode potential was tested. Specifically, in a 0.1 MKNO3 solution, the constructed electrode was used as the working electrode, and Ag / AgCl was used as the reference electrode to test the open-circuit potential. During the test, the effect of switching the light source on the electrode potential was recorded. Figure 5 As shown.

[0041] Depend on Figure 5 It is evident that light has virtually no effect on the electrode potential.

Claims

1. A miniaturized potentiometric ion sensor, characterized in that, The potentiometric ion sensor consists of an electrode substrate, an ion-electron transduction layer, and an ion-selective polymer film; wherein, the ion-electron transduction layer is formed of a redox solid transduction layer material.

2. The miniaturized potentiometric ion sensor according to claim 1, characterized in that, The redox solid transducer material is iron-cobalt sulfide.

3. The miniaturized potentiometric ion sensor according to claim 2, characterized in that, The sulfide is a hollow nanotube iron-cobalt sulfide synthesized from copper nitrate, cobalt nitrate, ammonium fluoride, urea and sodium sulfide as raw materials, with a molar ratio of (1~10):(1~10):(2~20):(10~100):(10~100).

4. The miniaturized potentiometric ion sensor according to claim 3, characterized in that, The sulfide is obtained by dissolving cobalt nitrate, copper nitrate, ammonium fluoride and urea in a mixed solution of water and ethanol according to the above molar ratio, and reacting the resulting solution at 100℃-160℃ for 10-16h to obtain a precursor; then placing it in an aqueous solution of sodium sulfide and continuing to react at 100℃-160℃ for 10-24h to obtain sulfide nanomaterials.

5. A method for fabricating a miniaturized potentiometric ion sensor as described in claim 1, characterized in that, A sulfide is drop-coated onto the surface of an electrode substrate as an ion-electron transduction layer. After drying, an ion-selective membrane precursor is drop-coated onto the ion-electron transduction layer to form an ion-selective membrane, thereby obtaining a miniaturized potential-type ion sensor.

6. The method for fabricating a miniaturized potentiometric ion sensor according to claim 5, characterized in that, The ion-selective membrane is composed of an ion support, tetra(4-chlorophenyl)borate tetradodecylammonium, polyvinyl chloride, and di-n-octyl sebacate, dissolved in tetrahydrofuran and stirred evenly to obtain the corresponding ion-selective polymer membrane; wherein the mass ratio of the ion support, tetradodecylammonium tetra(4-chlorophenyl)borate, polyvinyl chloride, and di-n-octyl sebacate is 0.5-1.0:0.5-1.0:17-34:32.5-65.

7. An application of the miniaturized potentiometric ion sensor according to claim 1, characterized in that: Application of the miniaturized potentiometric ion sensor in the detection of free ions in the environment.

8. The application of the miniaturized potentiometric ion sensor according to claim 7, characterized in that: The environment refers to water bodies, plants, animals, or food.

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