A chloride ion detection sensor

Abstract

The present invention relates to a chloride ion detection sensor, comprising an insulating substrate and a working electrode, a reference electrode, an auxiliary electrode, and electrode welding points corresponding to each electrode, located on the insulating substrate. The working electrode is located between the reference electrode and the auxiliary electrode. The working electrode, the reference electrode, and the auxiliary electrode are respectively connected to their corresponding electrode welding points via electrode wires, and each electrode wire is independent of each other and covered with an insulating layer. Each electrode welding point is used to connect to an external control circuit to output an electrode change signal. The chloride ion detection sensor of the present invention is a fully solid-state sensor that adopts a three-electrode system, which is conducive to reducing the interference of irrelevant substances and further improving the stability of the sensor and the accuracy of the detection results. In addition, it has the characteristics of small size, fast reaction speed, high sensitivity, and no need for bulky liquid electrodes. It can be integrated with a circuit board and combined with a wireless communication module and a control circuit to achieve fully automatic and unattended online monitoring of chloride ions.

Description

Technical Field

[0001] The invention belongs to the technical field of sensors, and in particular relates to a chloride ion detection sensor. Background Art

[0002] Chloride ions are common inorganic anions in our daily lives, prevalent in industries such as industry, agriculture, and biomedicine. In industry and agriculture, chloride ion concentrations directly affect the corrosion resistance of metal pipes and plant growth. In biomedicine, chloride ion concentrations in human blood, urine, and sweat can be used to diagnose and monitor diseases such as cystic fibrosis and hypochloremic metabolic alkalosis. In the food industry, measuring chloride ion concentrations provides guidance for food processing and quality. Furthermore, studies have shown that changes in chloride ion concentrations in underground fluids are closely related to regional seismic activity. Therefore, the rapid and accurate detection of chloride ion concentrations is of great practical significance.

[0003] Currently, the methods for chloride ion detection include Mohr method, turbidimetry, spectrophotometry, ion chromatography, potentiometric titration, atomic absorption spectrometry, polarography, flow injection analysis, etc. These methods generally have disadvantages such as cumbersome operation steps, expensive instruments, difficulty in portability, and complex maintenance.

[0004] Driven by the Internet of Things (IoT), sensors are gradually developing towards miniaturization, integration, and rapidity. Therefore, there is an urgent need to develop a micro chloride ion detection sensor with fast response speed and high sensitivity. Summary of the Invention

[0005] Based on the above-mentioned shortcomings and deficiencies in the prior art, one of the objects of the present invention is to at least solve one or more of the above-mentioned problems in the prior art. In other words, one of the objects of the present invention is to provide a chloride ion detection sensor that meets one or more of the above-mentioned needs.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0007] A chloride ion detection sensor comprises an insulating substrate and a working electrode, a reference electrode, an auxiliary electrode and electrode welding points corresponding to each electrode located on the insulating substrate, wherein the working electrode is located between the reference electrode and the auxiliary electrode;

[0008] The working electrode, reference electrode and auxiliary electrode are connected to their corresponding electrode welding points through electrode wires, and each electrode wire is independent of each other and covered with an insulating layer;

[0009] Each electrode welding point is used to connect to an external control circuit to output an electrode change signal.

[0010] As a preferred embodiment, the working electrode comprises a first conductive layer and a reaction layer sequentially stacked on an insulating substrate;

[0011] The first conductive layer is an interdigital electrode, which is a conductive Cu film deposited on an insulating substrate by electron beam evaporation vacuum coating.

[0012] The reaction layer includes a conductive nanofiber film layer, an Ag film layer and an AgCl film layer which are sequentially stacked on the first conductive layer.

[0013] As a preferred solution, the conductive nanofiber membrane layer is made by electrostatic spinning using polyvinylidene fluoride polymer as a spinning precursor, and adding conductive active materials and coupling agents.

[0014] As a preferred solution, the conductive active material includes one or more of doped metal nanoparticles, fullerene, graphene, and carbon nanotubes.

[0015] As a preferred solution, the thickness of the first conductive layer is 50nm-1μm, the thickness of the conductive nanofiber film layer is 100nm-5μm, the thickness of the Ag thin film layer is 200nm-5μm, and the thickness of the AgCl thin film layer is 500nm-10μm.

[0016] As a preferred solution, the reference electrode includes a second conductive layer, an Ag thin film layer, an AgCl thin film layer and a hydrogel layer stacked in sequence on an insulating substrate.

[0017] As a preferred embodiment, the second conductive layer is a conductive Cu film deposited on the insulating substrate by electron beam evaporation vacuum coating, with a film thickness of 50nm to 1μm;

[0018] The thickness of the Ag thin film layer is 200nm~5μm;

[0019] The thickness of the AgCl film layer is 500nm~10μm;

[0020] The thickness of the hydrogel layer is 0.5 to 1 μm.

[0021] As a preferred embodiment, the hydrogel layer includes the following components: 2-hydroxyethyl methacrylate, polyvinyl pyrrolidone, 2,2-dimethoxy-2-phenylacetophenone, ethylene glycol dimethacrylate and potassium chloride, and the weight ratio of each component is 5-15:1:0.2-0.6:0.02-0.1:1-4.

[0022] As a preferred solution, the auxiliary electrode comprises a third conductive layer and a Pt thin film layer sequentially stacked on an insulating substrate;

[0023] The third conductive layer is a conductive Cu film deposited on the insulating substrate by electron beam evaporation vacuum coating, with a film thickness of 50nm to 1μm;

[0024] The thickness of the Pt thin film layer is 200 nm to 10 μm.

[0025] As a preferred solution, the insulating substrate is a rigid silicon wafer or a flexible polyimide plastic substrate.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The chloride ion detection sensor of the present invention is a fully solid-state sensor that adopts a three-electrode system, which is beneficial to reducing the interference of irrelevant substances and further improving the stability of the sensor and the accuracy of the detection results. In addition, it has the characteristics of small size, fast response speed, high sensitivity, and no need for bulky liquid electrodes. It can be integrated with a circuit board and combined with a wireless communication module and a control circuit to realize fully automatic and unattended online monitoring of chloride ions.

[0028] (2) The working electrode of the present invention is an Ag / AgCl chloride ion selective electrode. The chloride ions and silver chloride in the test solution form a dynamic equilibrium. When the chloride ion concentration in the solution changes, the potential of the Ag / AgCl electrode also changes accordingly. The reference electrode potential is stable in the test solution. Combined with the Nernst equation, the chloride ion concentration can be obtained. The auxiliary electrode forms a loop with the working electrode to keep the current smooth and stable, so as to ensure that all reactions occur on the working electrode, making the measurement more accurate.

[0029] (3) The chloride ion detection sensor of the present invention uses a flexible polyimide plastic substrate, so that the sensor shape can be changed. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 1 is a schematic structural diagram of a chloride ion detection sensor according to embodiment 1 of the present invention;

[0031] Figure 2 is a cross-sectional view of the working electrode of Example 1 of the present invention;

[0032] Figure 3 This is an exploded view of the structure of the working electrode of Example 1 of the present invention;

[0033] Figure 4 is a cross-sectional view of the reference electrode of Example 1 of the present invention;

[0034] Figure 5 is a cross-sectional view of the auxiliary electrode of Example 1 of the present invention;

[0035] Figure 6 is a schematic structural diagram of a mask according to an embodiment of the present invention;

[0036] Figure 7 Schematic diagram of the structure of the chloride ion detection sensor of Example 2 of the present invention. DETAILED DESCRIPTION

[0037] To more clearly illustrate the embodiments of the present invention, specific embodiments of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings and other embodiments can be obtained based on these drawings without inventive efforts.

[0038] Example 1:

[0039] like Figure 1-5 As shown, the chloride ion detection sensor of this embodiment includes an insulating substrate 7 and a reference electrode 1, a working electrode 2, an auxiliary electrode 3 and electrode welding points 5 corresponding to each electrode located on the insulating substrate 7. The working electrode 2 is located between the reference electrode 1 and the auxiliary electrode 3.

[0040] The insulating substrate 7 of this embodiment is a rigid silicon wafer, ie, an insulating silicon substrate.

[0041] Among them, the working electrode 2, the reference electrode 1 and the auxiliary electrode 3 are respectively connected to the corresponding electrode welding points 5 through the electrode wires 4. Each electrode wire is independent of each other and covered with an insulating layer 6; specifically, silicone rubber is coated on the surface of the electrode wire as the insulating layer 6 to protect the electrode wire.

[0042] Each electrode pad 5 is used to connect to an external control circuit to output an electrode change signal.

[0043] The working electrode 2 of this embodiment includes a first conductive layer 2-1 and a reaction layer 2-2 stacked in sequence on an insulating substrate 7. Specifically, the first conductive layer 2-1 is an interdigitated electrode, which is prepared by a photolithography process. The interdigitated electrode array pattern includes a pair of sparse microelectrodes, each of which has 3 to 10 fingers. Dozens of fingers on the two sparse microelectrodes are arranged crosswise to form interdigitated electrodes; wherein the fingers are 3 to 8 mm long and 5 μm wide, and the spacing between adjacent fingers is 5 μm. The micro-pitch interdigitated strips can amplify the detection signal, further improving the detection sensitivity and accuracy of the sensor. The conductive Cu film is evaporated on the insulating substrate by electron beam evaporation vacuum coating, and the film thickness is 50 nm to 1 μm;

[0044] The reaction layer 2-2 includes a conductive nanofiber film layer 2-2A, an Ag film layer 2-2B, and an AgCl film layer 2-2C, which are sequentially stacked on the first conductive layer 2-1. Specifically, the reaction layer uses an electrospinning method to produce a conductive nanofiber film on the first conductive layer, and then deposits a metallic Ag layer and an AgCl layer on the conductive nanofiber. Due to the high porosity, large specific surface area, and uniform structure of the conductive nanofibers, they can increase the carrying capacity of the substance to be measured, thereby greatly increasing the electrochemical active sites of the sensor. The nanofibers accelerate the transmission and amplification of electrical signals, thereby increasing the sensor's sensitivity to chloride ion detection, shortening detection time, and improving sensor performance.

[0045] Among them, the conductive nanofiber membrane layer 2-2A uses polyvinylidene fluoride polymer as a spinning precursor, and is added with conductive active materials and coupling agents to be made by electrostatic spinning.

[0046] Polyvinylidene fluoride polymer has excellent chemical stability such as corrosion resistance, high temperature resistance, oxidation resistance, and ultraviolet resistance, thereby improving the chemical stability of the chloride ion sensor and extending the life of the chloride ion sensor.

[0047] Conductive active materials include one or more of doped metal nanoparticles, fullerenes, graphene, and carbon nanotubes. The addition of conductive active materials is used to improve the material's ability to transfer electrons. Taking carbon nanotubes doped in nanofibers as an example, carbon nanotubes have excellent mechanical properties, high mechanical strength, high electrical conductivity, and high electrochemical stability, which improve the effective electrical signal generated by the chloride ion reaction layer. Furthermore, carbon nanotubes have good chemical stability, which helps reduce signal fluctuations caused by complex components in the test solution, reduces interference from irrelevant substances, and improves the repeatability and stability of chloride ion detection.

[0048] The coupling agent can be one or a mixture of aminopropyltriethoxysilane (KH550), glycidyloxypropyltrimethoxysilane (KH560), methacryloxypropyltrimethoxysilane (KH570), vinyltriethoxysilane (A151), vinyltriethoxysilane (A171), mercaptopropyltrimethoxysilane (KH580, KH590), ethylenediaminepropyltriethoxysilane (KH792), ethylenediaminepropylmethyldimethoxysilane (KBM602), etc. The addition of the coupling agent increases the bonding strength between the fiber film and the electrode, prevents the film from falling off, and increases the service life of the sensor.

[0049] The thickness of the conductive nanofiber film layer is 100 nm to 5 μm, the thickness of the Ag thin film layer is 200 nm to 5 μm, and the thickness of the AgCl thin film layer is 500 nm to 10 μm.

[0050] The reference electrode 1 of this embodiment includes a second conductive layer 1-1, an Ag thin film layer 1-2, an AgCl thin film layer 1-3, and a hydrogel layer 1-4, which are sequentially stacked on an insulating substrate 7. The second conductive layer 1-1 is a conductive Cu film deposited on the insulating substrate using electron beam evaporation vacuum coating, with a thickness of 50nm to 1μm; the Ag thin film layer 1-2 has a thickness of 200nm to 5μm; the AgCl thin film layer 1-3 has a thickness of 500nm to 10μm; and the hydrogel layer 1-4 has a thickness of 0.5 to 1μm. Specifically, the reference electrode is formed by depositing a conductive Cu film on the insulating substrate, then depositing a layer of Ag thin film on the conductive Cu film, then depositing a layer of AgCl thin film on the Ag thin film layer, and finally coating the AgCl thin film layer with a layer of hydrogel.

[0051] The hydrogel layer includes the following components: 2-hydroxyethyl methacrylate, polyvinyl pyrrolidone, 2,2-dimethoxy-2-phenylacetophenone, ethylene glycol dimethacrylate and potassium chloride, and the weight ratio of each component is 10:1:0.4:0.05:2.75.

[0052] The auxiliary electrode 3 of this embodiment comprises a third conductive layer 3-1 and a Pt thin film layer 3-2, sequentially stacked on an insulating substrate 7. The third conductive layer 3-1 is a conductive Cu film deposited on the insulating substrate 7 using electron beam evaporation, with a thickness of 50 nm to 1 μm. The Pt thin film layer has a thickness of 200 nm to 10 μm. Specifically, the auxiliary electrode is formed by depositing a conductive Cu film on the insulating substrate, followed by a stable Pt thin film deposited on the conductive Cu film.

[0053] The preparation process of the chloride ion detection sensor of this embodiment is as follows:

[0054] (1) Place the insulating silicon substrate in an ultrasonic cleaning machine, clean it with hydrogen peroxide, acetone, and anhydrous ethanol in sequence, and then dry it. In a vacuum device, heat the insulating silicon substrate to 300°C and the vacuum degree reaches 10 -5 Pa, 50nm~1μm Cu film is evaporated on the insulating silicon substrate, and then according to the designed mask (such as Figure 6 As shown), the Cu film is photolithographically processed in a photolithography machine to obtain various conductive layers.

[0055] Among them, the interdigitated electrode array pattern of the working electrode includes a pair of sparse microelectrodes, each of which has 3 to 10 fingers. The 3 to 10 fingers on the two sparse microelectrodes are arranged crosswise to form an interdigitated electrode; the fingers are 3 to 8 mm long and 5 μm wide, and the spacing between adjacent fingers is 5 μm.

[0056] (2) Prepare a layer of conductive nanofibers on the interdigital electrodes by electrospinning: Weigh 2g of polyvinylidene fluoride and dissolve it in 25mL of acetone, stir and dissolve it, then add 0.3g of carbon nanotubes and 0.1g of aminopropyltriethoxysilane (KH550) and stir to obtain a uniform and stable polyvinyl alcohol electrospinning precursor solution; inject an appropriate amount of precursor solution into a syringe, use a stainless steel needle as a spinning nozzle, set the electrostatic high voltage direct current to 18KV~25KV, propel the precursor solution at a speed of 1mL / h~2.5mL / h, and set the spinning time to 5~25s. Under the action of the electric field, the polyvinyl alcohol electrospinning precursor solution forms a layer of 100nm~5μm high specific surface area and high porosity conductive composite fiber film on the interdigital electrodes.

[0057] (3) The fiber film substrate is placed in the vacuum coating chamber again for secondary electron beam evaporation vacuum coating. A layer of Ag film is first evaporated on the film fibers of the reference electrode and the working electrode, respectively, with a coating thickness of 200nm to 5μm; then a layer of AgCl film is evaporated on, with a coating thickness of 500nm to 10μm; a layer of Pt film is evaporated on the auxiliary electrode, with a coating thickness of 200nm to 10μm; the coating method is the same as the evaporation of Cu film.

[0058] (4) The outer surface of the reference electrode is coated with a layer of hydrogel. The hydrogel is composed of 2-hydroxyethyl methacrylate: polyvinyl pyrrolidone: 2,2-dimethoxy-2-phenylacetophenone (DMPAP): ethylene glycol dimethacrylate and potassium chloride in a mass ratio of 10:1:0.4:0.05:2.75.

[0059] (5) Silicone rubber is applied to the surface of the electrode wire as an insulating layer to protect the electrode wire.

[0060] The working electrode of the chloride ion detection sensor of this embodiment is an Ag / AgCl chloride ion selective electrode. The chloride ions and silver chloride in the test solution form a dynamic equilibrium. When the chloride ion concentration in the solution changes, the potential of the Ag / AgCl electrode also changes accordingly; while the reference electrode potential is stable in the test solution. Combined with the Nernst equation, the chloride ion concentration can be obtained; the auxiliary electrode and the working electrode form a loop to maintain smooth and stable current flow to ensure that all reactions occur at the working electrode, making the measurement more accurate.

[0061] Example 2:

[0062] The chloride ion detection sensor of this embodiment is different from that of Example 1 in that:

[0063] The insulating substrate 7 is replaced with a flexible polyimide plastic substrate to achieve a variable shape of the chloride ion detection sensor, such as Figure 7 As shown, the chloride ion detection sensor has a curved structure to meet the needs of different detection applications;

[0064] For other structures and preparation processes, please refer to Example 1.

[0065] Example 3:

[0066] The chloride ion detection sensor of this embodiment is different from that of Example 1 in that:

[0067] The ratio of the hydrogel is different. Specifically, the amount of 2-hydroxyethyl methacrylate, polyvinyl pyrrolidone, 2,2-dimethoxy-2-phenylacetophenone, ethylene glycol dimethacrylate and potassium chloride can be selected within the corresponding range of 5-15:1:0.2-0.6:0.02-0.1:1-4 according to actual application requirements;

[0068] For other structures and preparation processes, please refer to Example 1.

[0069] The above description is only a detailed description of the preferred embodiments and principles of the present invention. For ordinary technicians in this field, based on the ideas provided by the present invention, there may be changes in the specific implementation methods, and these changes should also be considered as the scope of protection of the present invention.

Claims

1. A chloride ion detection sensor, characterized in that: It includes an insulating substrate and a working electrode, a reference electrode, an auxiliary electrode and electrode welding points corresponding to each electrode, the working electrode is located between the reference electrode and the auxiliary electrode; The working electrode, reference electrode and auxiliary electrode are connected to their corresponding electrode welding points through electrode wires, and each electrode wire is independent of each other and covered with an insulating layer; Each electrode welding point is used to connect to an external control circuit to output an electrode change signal; The reference electrode comprises a second conductive layer, an Ag thin film layer, an AgCl thin film layer and a hydrogel layer stacked in sequence on an insulating substrate; The working electrode comprises a first conductive layer and a reaction layer sequentially stacked on an insulating substrate; The first conductive layer is an interdigitated electrode, which is a conductive Cu film deposited on an insulating substrate by electron beam evaporation vacuum coating; The reaction layer comprises a conductive nanofiber film layer, an Ag film layer and an AgCl film layer sequentially stacked on the first conductive layer; The conductive nanofiber membrane layer is made by electrostatic spinning using polyvinylidene fluoride polymer as a spinning precursor and adding conductive active material and coupling agent.

2. The chloride ion detection sensor according to claim 1, characterized in that: The conductive active material includes one or more of doped metal nanoparticles, fullerene, graphene, and carbon nanotubes.

3. The chloride ion detection sensor according to claim 1, characterized in that: The thickness of the first conductive layer is 50 nm to 1 μm, the thickness of the conductive nanofiber film layer is 100 nm to 5 μm, the thickness of the Ag thin film layer is 200 nm to 5 μm, and the thickness of the AgCl thin film layer is 500 nm to 10 μm.

4. The chloride ion detection sensor according to claim 1, characterized in that: The second conductive layer is a conductive Cu film deposited on the insulating substrate by electron beam evaporation vacuum coating, with a film thickness of 50nm to 1μm; The thickness of the Ag thin film layer is 200nm~5μm; The thickness of the AgCl film layer is 500nm~10μm; The thickness of the hydrogel layer is 0.5 to 1 μm.

5. The chloride ion detection sensor according to claim 1, characterized in that: The hydrogel layer comprises the following components: 2-hydroxyethyl methacrylate, polyvinyl pyrrolidone, 2,2-dimethoxy-2-phenylacetophenone, ethylene glycol dimethacrylate and potassium chloride, and the weight ratio of each component is 5-15:1:0.2-0.6:0.02-0.1:1-4.

6. The chloride ion detection sensor according to any one of claims 1 to 3, characterized in that: The auxiliary electrode comprises a third conductive layer and a Pt thin film layer sequentially stacked on an insulating substrate; The third conductive layer is a conductive Cu film deposited on the insulating substrate by electron beam evaporation vacuum coating, with a film thickness of 50nm to 1μm; The thickness of the Pt thin film layer is 200 nm to 10 μm.

7. The chloride ion detection sensor according to any one of claims 1 to 3, characterized in that: The insulating substrate is a rigid silicon wafer or a flexible polyimide plastic substrate.

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