Electrochemical water quality microsensor

Abstract

The invention provides an electrochemical water quality microsensor which can be applied to the technical field of water quality detection sensors. The sensor comprises a substrate, a thin-layer detection cavity structure, a common counter electrode, a common reference electrode, a detection working electrode and a pH regulation and control electrode, and the thin-layer detection cavity structure comprises a groove, a sample inlet and a sample outlet; a cavity is formed between the groove of the thin layer detection cavity structure and the substrate; a sample to be detected flows into the cavity from the sample inlet and flows out from the sample outlet; the pH regulation and control electrode and the detection working electrode form an annular concentric array and are distributed in a double-helix structure. The pH value of a solution in an area close to the working electrode is controlled by adjusting the potential or current applied to the pH regulation electrode, so that the necessary acidification or alkalization operation step during conventional electrochemical detection analysis is avoided, reagent-free or less detection is realized, and the process of detecting pollutants in water by using an electrochemical method is greatly simplified.

Description

Technical Field

[0001] The present disclosure relates to the technical field of water quality detection sensors, and in particular to an electrochemical water quality microsensor. Background Art

[0002] Traditional water quality testing technologies mainly include atomic absorption spectrophotometry, atomic fluorescence spectroscopy, and inductively coupled plasma mass spectrometry. Although traditional technologies can achieve good detection performance, the instruments and equipment are large in size, complex in operation, have long test cycles, high analysis costs, and require the use of pre-concentration and separation technologies (such as solid phase microextraction, dispersed liquid-liquid microextraction, etc.). Therefore, most of them are limited to laboratory deployment and are difficult to use for rapid on-site detection, and are also difficult to respond to sudden water pollution incidents. The field of environmental monitoring has an urgent need for simple, rapid, sensitive, and miniaturized water pollution detection technologies suitable for on-site detection. At the same time, water pollution detection technologies with such characteristics are also an important development direction of current water quality detection technologies.

[0003] Electrochemical sensors refer to devices or apparatuses that can sense (or respond to) biological or chemical quantities and convert them into electrical signals according to certain rules. They can directly convert chemical signals into electrical signals, and have the advantages of high detection sensitivity, low detection limit, simple operation, low equipment cost, and easy miniaturization. They have unique advantages in on-site rapid detection of water quality and are considered to be the most suitable method for on-site rapid detection of water quality. At present, research on the use of electrochemical sensors for the detection of water quality parameters such as pH, dissolved oxygen, nitrate, ammonia nitrogen, chemical oxygen demand, and heavy metals has been widely reported. Related research results have been widely used in sewage treatment, aquaculture, lake monitoring, organic agriculture, environmental monitoring and other fields.

[0004] Under existing technical conditions, the use of electrochemical sensors to detect pollutants in water bodies still relies on the use of a large number of chemical reagents. For example, before using stripping voltammetry to detect heavy metal ions, the water sample to be tested and the sample solution serving as a standard need to be acidified. The required degree of acidification varies depending on the type of heavy metal ions and the detection electrode used. When using carbon electrodes to detect lead, the test solution needs to be adjusted to a weak acidity of pH ≈ 4.5; when using gold electrodes to detect mercury, high-concentration hydrochloric acid needs to be used to acidify the test solution to a strong acid environment of pH = 1. When using copper or silver modified electrodes for electrochemical detection of nitrate in water, it is generally necessary to adjust the test sample to an acidic environment of pH 1~2. When using platinum electrodes for electrochemical detection of ammonia nitrogen in water, it is generally necessary to adjust the test sample to a strong alkalinity (pH>12). This complex and hazardous reagent preparation requirement not only increases the operating steps and increases the detection cost, but also brings additional chemical hazard handling and management issues, and naturally increases the possibility of errors and handling errors. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In order to solve the problems existing in the electrochemical detection of pollutants in water in the prior art, the embodiments of the present disclosure provide an electrochemical water quality microsensor, which is designed by designing two functionalized microelectrodes adjacent to each other and distributed in a double helix structure and a microfluidic sensor with a thin layer detection cell, wherein one of the two functionalized microelectrodes is used as a working electrode for electrochemical detection, and the other is used as an electrode for pH control of the solution in the detection cell. By adjusting the potential or current applied to the pH control electrode, the pH value of the solution in the vicinity of the working electrode is controlled, thereby avoiding the acidification or alkalization operation steps required for conventional electrochemical detection and analysis, realizing reagent-free / low-reagent detection, and greatly simplifying the process of using electrochemical methods to detect pollutants in water. This invention is of great significance to water quality detection, and at the same time has important application value for on-site in-situ analysis and continuous monitoring of pollutants in water by electrochemical sensors.

[0007] (II) Technical solution

[0008] In view of the above problems, an embodiment of the present disclosure provides an electrochemical water quality microsensor.

[0009] According to the first aspect of the present disclosure, an electrochemical water quality microsensor is provided, an electrochemical water quality microsensor, characterized in that it includes: a substrate, a thin layer detection cavity structure, a common counter electrode, a common reference electrode, a detection working electrode and a pH control electrode, wherein the thin layer detection cavity structure includes a groove, an injection port and a sample outlet; a cavity is formed between the groove of the thin layer detection cavity structure and the substrate; the sample to be detected flows into the cavity from the injection port and flows out from the sample outlet; one end of the common counter electrode, the common reference electrode, the detection working electrode and the pH control electrode are located inside the cavity.

[0010] In some exemplary embodiments, the pH controlling electrode and the detection working electrode form a circular concentric array distributed in a double helix structure; the pH controlling electrode is used to control the pH value of the solution, and the pH value of the solution is related to the potential or current applied to the pH controlling electrode; and the distance between the detection working electrode and the pH controlling electrode does not exceed the range in which the pH controlling electrode can control the pH value of the solution.

[0011] In some exemplary embodiments, the geometric dimensions of the detection working electrode are in the order of micrometers; the geometric dimensions of the pH control electrode are in the order of micrometers; and the geometric dimensions of the common counter electrode are in the order of millimeters.

[0012] In some exemplary embodiments, at least one of the following features is included: the height of the cavity is 50μm-400µm; the electrode width of the detection working electrode is 2μm-20µm; the electrode width of the pH control electrode is 2μm-20µm; the spacing between the pH control electrode and the detection working electrode is 1 to 5 times the width of the pH control electrode.

[0013] In some exemplary embodiments, the structure of the common counter electrode is a ring structure; the electrode width of the common counter electrode is 1mm-5mm; the distance between the inner ring of the common counter electrode and the double helix structure formed by the detection working electrode and the pH control electrode is 5mm-25mm; the area of ​​the common counter electrode is greater than 1000 times the area of ​​the detection working electrode.

[0014] In some exemplary embodiments, the common reference electrode includes an on-chip integrated Ag / AgCl solid-state reference electrode, wherein the preparation method of Ag / AgCl includes: preparing it by chlorinating a metal silver film in an acidic solution environment; or preparing it by coating Ag / AgCl slurry on a gold base electrode.

[0015] In some exemplary embodiments, the detection working electrode, the common counter electrode and the common reference electrode form a micro-electrochemical three-electrode system, which can perform electrochemical scanning to achieve identification and detection of pollutants in water bodies; and the pH control electrode, the common counter electrode and the common reference electrode form an electrochemical pH control system, which performs electrochemical constant current and / or constant voltage scanning to maintain the hydrolysis reaction in a specific area of ​​the thin layer detection cavity, so as to achieve the control of the pH value of the solution in the detection area of ​​the detection working electrode.

[0016] In some exemplary embodiments, the material of the substrate includes one of silicon or glass. When the material of the substrate is silicon, an insulating film is grown on the silicon surface, and the material of the insulating film includes silicon oxide and silicon nitride; the material of the pH regulating electrode includes gold; the material of the common counter electrode includes gold; the material of the detection working electrode is related to the type of pollutant to be detected, and the material of the detection working electrode includes one of gold, platinum, silver, copper or carbon.

[0017] In some exemplary embodiments, the surfaces of the pH controlling electrode, the common counter electrode, the detection working electrode and the common reference electrode are covered with an insulating layer, and the material of the insulating layer includes one of silicon oxide, silicon nitride, a composite film composed of silicon oxide and silicon nitride, or a photoresist.

[0018] In some exemplary embodiments, at least one of the following features is included: a thin-layer detection cavity structure is prepared by using a PDMS material using a demolding process; the thin-layer detection cavity structure and the substrate are packaged and formed by an oxygen plasma bonding process; and the preparation method of the detection working electrode, the pH regulating electrode, the common counter electrode and the common reference electrode includes one of a magnetron sputtering method or an electron beam evaporation method.

[0019] (III) Beneficial effects

[0020] It can be seen from the above technical solutions that the electrochemical water quality microsensor provided by the embodiments of the present disclosure has at least one of the following beneficial effects:

[0021] (1) Design two functionalized microelectrodes adjacent to each other and distributed in a double helix structure, and design a microfluidic sensor with a thin layer detection cell, wherein one of the two functionalized microelectrodes is used as a working electrode for electrochemical detection, and the other is used as a pH control electrode for the solution in the detection cell. By adjusting the potential or current applied to the pH control electrode, the pH value of the solution in the vicinity of the working electrode is controlled, thereby avoiding the acidification or alkalization operation steps required for conventional electrochemical detection and analysis, achieving reagent-free / low-reagent detection, and greatly simplifying the process of using electrochemical methods to detect pollutants in water.

[0022] (2) This invention is of great significance to water quality testing, and also has important application value in the on-site in-situ analysis and continuous monitoring of pollutants in water by electrochemical sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above contents and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0024] Figure 1 The overall structure of an electrochemical water quality microsensor according to an embodiment of the present disclosure is schematically shown;

[0025] Figure 2 A schematic diagram of an explosion structure of an electrochemical water quality microsensor according to an embodiment of the present disclosure is shown; and

[0026] Figure 3 A schematic diagram of the planar distribution of an electrochemical water quality microsensor according to an embodiment of the present disclosure is shown schematically.

[0027] Reference numerals:

[0028] 1-thin layer detection cavity structure; 11-inlet; 12-outlet; 13-groove; 2-substrate; 3-cavity; 4-common counter electrode; 5-pH control electrode; 6-detection working electrode; 7-common reference electrode. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present disclosure.

[0030] Figure 1 The overall structure of an electrochemical water quality microsensor according to an embodiment of the present disclosure is schematically shown; Figure 2 A schematic diagram of an explosion structure of an electrochemical water quality microsensor according to an embodiment of the present disclosure is shown; and Figure 3 A schematic diagram of the planar distribution of an electrochemical water quality microsensor according to an embodiment of the present disclosure is shown schematically.

[0031] like Figure 1 , Figure 2 and Figure 3As shown, an electrochemical water quality microsensor according to an embodiment of the present disclosure includes: a substrate 2, a thin layer detection cavity structure 1, a common counter electrode 4, a common reference electrode 7, a detection working electrode 6 and a pH control electrode 5, wherein the thin layer detection cavity structure 1 includes a groove 13, an injection port 11 and a sample outlet 12; a cavity 3 is formed between the groove 13 of the thin layer detection cavity structure 1 and the substrate 2; the sample to be detected flows into the cavity 3 from the injection port 11 and flows out from the sample outlet 12; one end of the common counter electrode 4, the common reference electrode 7, the detection working electrode 6 and the pH control electrode 5 are located inside the cavity 3.

[0032] The microsensor is prepared by micromachining (MEMS) technology, and four functional electrodes are integrated in a thin layer detection cavity, wherein the detection working electrode 6 and the pH control electrode 5 are adjacent to each other and distributed in a double helix structure, see Figure 3 ; The detection working electrode 6, the common counter electrode 4 and the common reference electrode 7 form a micro electrochemical three-electrode system, which can perform electrochemical scanning to detect pollutants in water bodies; and the pH control electrode 5, the common counter electrode 4 and the common reference electrode 7 form an electrochemical pH control system, which performs electrochemical constant current and / or constant voltage scanning to maintain the hydrolysis reaction in the thin layer detection cavity, so as to realize the regulation of the pH value of the solution in the detection area of ​​the detection working electrode 6.

[0033] In some exemplary embodiments, the pH controlling electrode 5 and the detection working electrode 6 form a circular concentric array distributed in a double helix structure; the pH controlling electrode 5 is used to control the pH value of the solution, and the pH value of the solution is related to the potential or current applied to the pH controlling electrode 5; and the distance between the detection working electrode 6 and the pH controlling electrode 5 does not exceed the range of the pH value of the solution that the pH controlling electrode 5 can control.

[0034] By adjusting the potential or current applied to the pH control electrode 5, the pH value of the solution in the vicinity of the working electrode is controlled, thereby avoiding the acidification or alkalization steps required for conventional electrochemical detection and analysis, achieving reagent-free / low-reagent detection, and greatly simplifying the process of using electrochemical methods to detect pollutants in water.

[0035] In some exemplary embodiments, the geometric dimensions of the detection working electrode 6 are in the micrometer range; the geometric dimensions of the pH control electrode 5 are in the micrometer range; and the spacing between the pH control electrode 5 and the detection working electrode 6 is 1-5 times the width of the pH control electrode 5 .

[0036] For example, the electrode width of the detection working electrode 6 is 2 μm-20 μm; the electrode width of the pH control electrode 5 is 2 μm-20 μm.

[0037] In some exemplary embodiments, the structure of the common counter electrode 4 is a ring structure; the geometric size of the common counter electrode 4 is in the micrometer order; the distance between the inner ring of the common counter electrode 4 and the double helix structure formed by the detection working electrode 6 and the pH control electrode 5 is 5 mm to 25 mm; the area of ​​the common counter electrode 4 is greater than 1000 times the area of ​​the detection working electrode 6. Optionally, the electrode width of the common counter electrode 4 is 1 mm to 5 mm.

[0038] In some exemplary embodiments, the material of the substrate 2 includes silicon, glass and the like. When the material of the substrate 2 is a silicon wafer, an insulating film needs to be grown on the surface of the silicon wafer first. Optionally, the insulating film includes silicon oxide and silicon nitride.

[0039] In some exemplary embodiments, the material of the pH control electrode 5 includes gold; the material of the common counter electrode 4 includes gold; the material of the detection working electrode 6 is related to the type of pollutant to be detected, and the material of the detection working electrode 6 includes one of gold, platinum, silver, copper or carbon. Optionally, the preparation method of the detection working electrode 6, the pH control electrode 5, the common reference electrode 7 and the common counter electrode 4 includes one of magnetron sputtering or electron beam evaporation.

[0040] In some exemplary embodiments, the common reference electrode 7 includes an on-chip integrated Ag / AgCl solid-state reference electrode, wherein the preparation method of Ag / AgCl includes: preparing it by chlorinating a metal silver film in an acidic solution environment; or preparing it by coating Ag / AgCl slurry on a gold substrate 2 electrode.

[0041] Optionally, the surface of the electrode layer is covered with an insulating layer, which may be silicon oxide, silicon nitride, a composite film of silicon oxide and silicon nitride, or SU8 photoresist, so as to define the surface of each sensitive electrode and the corresponding pad position.

[0042] In some exemplary embodiments, the thin-layer detection cavity structure 1 is made of PDMS material (polydimethylsiloxane, which is an organic silicon polymer material composed of alternating silicon and oxygen atoms and carries methyl groups. These methyl groups give PDMS good plasticity and elasticity, and its physical and chemical properties can be changed by adjusting the molecular weight and cross-linking degree) using a demolding process, and the thin-layer detection cavity structure 1 and the substrate 2 are encapsulated and formed by an oxygen plasma bonding process. Optionally, the height of the cavity 3 is 50μm-400µm.

[0043] In some exemplary embodiments, the surfaces of the pH control electrode 5, the common counter electrode 4, the detection working electrode 6 and the common reference electrode 7 are covered with an insulating layer, and the material of the insulating layer includes one of silicon oxide, silicon nitride, a composite film composed of silicon oxide and silicon nitride, or a photoresist.

[0044] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. An electrochemical water quality microsensor, characterized in that: include: Substrate, thin layer detection cavity structure, common counter electrode, common reference electrode, detection working electrode and pH control electrode, Wherein, the thin layer detection cavity structure includes a groove, an inlet and an outlet; A cavity is formed between the groove of the thin layer detection cavity structure and the substrate; The sample to be detected flows into the cavity from the sample inlet and flows out from the sample outlet; The common counter electrode, the common reference electrode, the detection working electrode and one end of the pH regulating electrode are located inside the cavity.

2. The electrochemical water quality microsensor according to claim 1, characterized in that: The pH regulating electrode and the detection working electrode form a circular concentric array and are distributed in a double helix structure; The pH control electrode is used to control the pH value of a solution, and the pH value of the solution is related to the potential or current applied to the pH control electrode; as well as The distance between the detection working electrode and the pH regulating electrode does not exceed the range in which the pH regulating electrode can regulate the pH value of the solution.

3. The electrochemical water quality microsensor according to claim 2, characterized in that: The geometric size of the detection working electrode is in the micrometer range; The geometric size of the pH control electrode is in the micrometer range; and The geometrical dimensions of the common counter electrode are in the order of millimeters.

4. The electrochemical water quality microsensor according to claim 3, characterized in that: Include at least one of the following features: The height of the cavity is 50μm-400µm; The electrode width of the detection working electrode is 2μm-20µm; The electrode width of the pH control electrode is 2μm-20μm; The distance between the pH regulating electrode and the detection working electrode is 1 to 5 times the width of the pH regulating electrode.

5. The electrochemical water quality microsensor according to claim 3, characterized in that: The structure of the common counter electrode is a ring structure; The electrode width of the common counter electrode is 1 mm-5 mm; The distance between the inner ring of the common counter electrode and the double helix structure formed by the detection working electrode and the pH control electrode is 5 mm-25 mm; The area of ​​the common counter electrode is 1000 times greater than the area of ​​the detection working electrode.

6. The electrochemical water quality microsensor according to claim 2, characterized in that: The common reference electrode comprises an on-chip integrated Ag / AgCl solid-state reference electrode, wherein the preparation method of the Ag / AgCl comprises: Prepared by chlorinating the metallic silver film in an acidic solution environment; or The Ag / AgCl slurry is coated on the base electrode to prepare it.

7. The electrochemical water quality microsensor according to claim 2, characterized in that: The detection working electrode, the common counter electrode and the common reference electrode form a micro electrochemical three-electrode system, which can perform electrochemical scanning to achieve identification and detection of pollutants in water; and The pH control electrode, the common counter electrode and the common reference electrode form an electrochemical pH control system, and perform electrochemical constant current and / or constant voltage scanning to maintain the hydrolysis reaction in a specific area of ​​the thin layer detection cavity, so as to achieve the control of the pH value of the solution in the detection area of ​​the detection working electrode.

8. The electrochemical water quality microsensor according to any one of claims 1 to 7, characterized in that: The material of the substrate includes one of silicon or glass. When the material of the substrate is silicon, an insulating film is grown on the surface of the silicon. The material of the insulating film includes silicon oxide and silicon nitride. The material of the pH regulating electrode includes gold; The material of the common counter electrode includes gold; The material of the detection working electrode is related to the type of pollutants to be detected, and the material of the detection working electrode includes one of gold, platinum, silver, copper or carbon.

9. The electrochemical water quality microsensor according to claim 8, characterized in that: The surfaces of the pH regulating electrode, the common counter electrode, the detection working electrode and the common reference electrode are covered with an insulating layer, and the material of the insulating layer includes one of silicon oxide, silicon nitride, a composite film composed of silicon oxide and silicon nitride, or a photoresist.

10. The electrochemical water quality microsensor according to any one of claims 1 to 7, characterized in that: Include at least one of the following features: The thin layer detection cavity structure is prepared by using PDMS material and a demoulding process; The thin layer detection cavity structure and the substrate are packaged and formed by an oxygen plasma bonding process; and The preparation method of the detection working electrode, the pH regulating electrode, the common counter electrode and the common reference electrode comprises a magnetron sputtering method or an electron beam evaporation method.

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