Cd-EDTA (Ethylene Diamine Tetraacetic Acid) detection method based on solid nanopore detection technology

Abstract

The invention discloses a Cd-EDTA (Ethylene Diamine Tetraacetic Acid) detection method based on a solid nanopore detection technology, which comprises the following steps: acquiring a nanopore sensor, and preparing nanopores in the nanopore sensor by adopting an electron beam lithography technology; preparing an electrolyte solution; the method comprises the following steps: preparing a Cd-EDTA sample and preparing standard Cd-EDTA solutions with different concentrations; after the electrochemical workstation is configured, applying an alternating current signal, and obtaining a response signal of the nanopore sensor within a preset frequency range to obtain a current blocking signal; the Cu-EDTA detection is realized on the basis of current blocking signals corresponding to the Cd-EDTA sample and the standard Cd-EDTA solutions with different concentrations. According to the invention, the detection sensitivity of the Cd-EDTA compound is improved, and accurate detection can be realized at low concentration. The system realizes real-time and unmarked detection, and is suitable for monitoring pollutants in a complex environment of a mining area.

Description

Technical Field

[0001] The invention belongs to the technical field of rapid detection of environmental pollutants in mining areas, and in particular relates to a Cd-EDTA detection method based on solid-state nanopore detection technology. Background Art

[0002] With the increase of mining activities in mining areas, heavy metal pollution in the environment, especially the pollution of rare metals such as indium (Cd), has gradually become a hot issue in environmental monitoring. Indium is widely used in electronics, photovoltaics, and displays. Its complex with ethylenediaminetetraacetic acid (EDTA) (Cd-EDTA) is relatively common in the environment and has strong mobility and bioaccumulation. Once Cd-EDTA enters the water body, in addition to causing water pollution, it may also pose a long-term threat to the ecosystem and human health. Therefore, accurate and real-time detection of Cd-EDTA complexes has become a key task in environmental pollution monitoring in mining areas.

[0003] At present, although traditional detection methods such as spectroscopy, electrochemistry and chromatography can effectively detect Cd-EDTA in laboratory environments, they are often difficult to provide fast and accurate monitoring results in the complex environment of mining areas, especially when there are many types of pollutants in water and strong background interference. In addition, the cumbersome operation and long processing process also limit its on-site application. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a Cd-EDTA detection method based on solid-state nanopore detection technology to solve the problems existing in the above prior art.

[0005] To achieve the above object, the present invention provides a Cd-EDTA detection method based on solid-state nanopore detection technology, comprising:

[0006] Obtaining a nanopore sensor, wherein the nanopore in the nanopore sensor is prepared by electron beam lithography;

[0007] preparing electrolyte solution; preparing Cd-EDTA samples and preparing standard Cd-EDTA solutions of different concentrations;

[0008] After configuring the electrochemical workstation, an AC signal is applied, and the response signal of the nanopore sensor is obtained within a preset frequency range to obtain a current blockade signal; Cu-EDTA is detected based on the current blockade signal corresponding to the Cd-EDTA sample and the standard Cd-EDTA solution of different concentrations.

[0009] Optionally, the process of preparing the nanopore using electron beam lithography includes:

[0010] After cleaning the Si3N4 substrate, a layer of photoresist is coated on the surface, wherein the thickness of the photoresist is determined based on the aperture requirements of the nanopore; after the photoresist is coated, the uniformity of the photoresist coating is adjusted using a spin coating technique; an electron beam lithography machine scans the photoresist for exposure according to a preset pattern; after exposure, a development process is performed to remove the unexposed photoresist portion; the pattern is transferred to the Si3N4 substrate using a plasma etching technique, and the material in the exposed area is removed by etching to complete the preparation of the nanopore.

[0011] Optionally, the process of obtaining the nanopore sensor further includes:

[0012] Graphene was grown on the surface of a metal catalyst using chemical vapor deposition. The graphene surface was functionalized using oxygen plasma treatment and chemical activation, and then transferred to a Si3N4 substrate using a solution transfer method.

[0013] Optionally, the electrolyte solution is a mixture of ammonia water and methanol, and the pH range of the electrolyte solution is 9.5-11.5.

[0014] Optionally, the process of preparing the Cd-EDTA sample includes:

[0015] The required mass of the Cd-EDTA complex is calculated according to the required concentration and weighed; it is completely dissolved in deionized water and stirred or ultrasonically treated; the Cd-EDTA solution is added to the tailings and stirred evenly until the complex is fully adsorbed on the surface of the tailings, and finally a Cd-EDTA tailings sample of the required concentration is obtained.

[0016] Optionally, the standard Cd-EDTA solution includes four concentrations: 1 mol / L, 2 mol / L, 4 mol / L, and 6 mol / L.

[0017] Optionally, the process of obtaining the current blocking signal of the standard Cd-EDTA solution includes: dropping standard Cd-EDTA solutions of different concentrations onto the surface of the nanopore sensor and maintaining a contact time of 30 minutes.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects:

[0019] The present invention provides a novel device for detecting composite pollutants (Cd-EDTA) in mining areas. The device is based on a nanopore sensor and introduces a two-dimensional material graphene layer to enhance the conductivity and selectivity and improve the detection sensitivity of the Cd-EDTA complex. The nanopores are prepared by electron beam lithography, and graphene is grown on the surface of the metal catalyst by chemical vapor deposition (CVD) and transferred to a Si3N4 substrate. The graphene surface is functionalized and covalently bound to the antibody. The impedance spectrum is measured by an electrochemical workstation, and after applying a small amplitude AC signal, the change in the charge transfer resistance in the Nyquist diagram is analyzed to further evaluate the response characteristics of the sensor to the Cd-EDTA complex. Through the gradient experiment of Cd-EDTA solution with different concentrations, combined with the Nyquist diagram analysis, the sensitivity and detection performance of the sensor can be accurately evaluated, providing effective technical support for the monitoring of heavy metal pollutants in the mining environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0021] Figure 1 is a schematic diagram of a device according to an embodiment of the present invention;

[0022] Figure 2 Schematic diagram of the sample determination principle of an embodiment of the present invention, (a) is a schematic diagram of a nanopore detection device; (b) is a schematic diagram of a reference current; (c) and (d) are schematic diagrams of the blocking current generated by different sizes of analytes passing through the nanopore;

[0023] Figure 3 The figure is a flow chart of a method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0026] Embodiment 1

[0027] like Figure 1-3 As shown, this embodiment provides a Cd-EDTA detection method based on solid-state nanopore detection technology, comprising:

[0028] Obtaining a nanopore sensor, wherein the nanopore in the nanopore sensor is prepared by electron beam lithography;

[0029] Furthermore, the process of preparing the nanopores using electron beam lithography technology includes:

[0030] After cleaning the Si3N4 substrate, a layer of photoresist is coated on the surface, wherein the thickness of the photoresist is determined based on the aperture requirements of the nanopore; after the photoresist is coated, the uniformity of the photoresist coating is adjusted using a spin coating technique; an electron beam lithography machine scans the photoresist for exposure according to a preset pattern; after exposure, a development process is performed to remove the unexposed photoresist portion; the pattern is transferred to the Si3N4 substrate using a plasma etching technique, and the material in the exposed area is removed by etching to complete the preparation of the nanopore.

[0031] Furthermore, the process of obtaining the nanopore sensor also includes:

[0032] Graphene was grown on the surface of a metal catalyst using chemical vapor deposition. The graphene surface was functionalized using oxygen plasma treatment and chemical activation, and then transferred to a Si3N4 substrate using a solution transfer method.

[0033] Specifically, on the basis of the traditional nanopore sensor, a two-dimensional material graphene layer is added to enhance the conductivity and selectivity of the nanopore and improve the detection sensitivity of the Cd-EDTA complex. The nanopore is manufactured using electron beam lithography technology to precisely control the pore size (usually 10-15nm), and the pore pattern is transferred to the Si3N4 substrate by plasma etching. The graphene layer is grown on the surface of the metal catalyst by chemical vapor deposition (CVD) and transferred to the surface of the Si3N4 substrate by solution transfer.

[0034] To improve selectivity, the graphene surface is treated with oxygen plasma to generate oxygen-containing functional groups such as carboxyl and hydroxyl groups. The carboxyl groups are further activated using reagents such as 1-chloro-3-chloromethyl-1,3,5-triazine (CDI), or converted into active esters through EDC / NHS cross-linking reaction, which are then covalently bound to amino groups (such as lysine residues) on the antibody to achieve antibody immobilization.

[0035] preparing electrolyte solution; preparing Cd-EDTA samples and preparing standard Cd-EDTA solutions of different concentrations;

[0036] Furthermore, the electrolyte solution is a mixture of ammonia water and methanol, and the pH range of the electrolyte solution is 9.5-11.5.

[0037] Further, the process of preparing the Cd-EDTA sample includes:

[0038] The required mass of the Cd-EDTA complex is calculated according to the required concentration and weighed; it is completely dissolved in deionized water and stirred or ultrasonically treated; the Cd-EDTA solution is added to the tailings and stirred evenly until the complex is fully adsorbed on the surface of the tailings, and finally a Cd-EDTA tailings sample of the required concentration is obtained.

[0039] Furthermore, the standard Cd-EDTA solution includes four concentrations: 1 mol / L, 2 mol / L, 4 mol / L, and 6 mol / L.

[0040] Specifically, according to the required concentration (1mol / L, 2mol / L, 4mol / L, 6mol / L), the Cd-EDTA complex solution is accurately prepared. The required mass of Cd-EDTA complex is weighed and dissolved in an appropriate amount of deionized water to ensure that the complex is completely dissolved, and the uniformity is ensured by stirring or ultrasonic treatment. Finally, the dissolved Cd-EDTA solution is added to the tailings to ensure that the complex is fully adsorbed on the surface of the tailings to obtain a Cd-EDTA tailings sample of the required concentration.

[0041] Exemplarily, a Cd-EDTA sample is prepared. First, the mass of the required Cd-EDTA complex is calculated according to the required concentration. Next, the required mass of the Cd-EDTA complex is weighed, and you can choose to use a Cd-EDTA standard solution or synthesize the Cd-EDTA complex from Cd(II) and EDTA powder. Then, dissolve it in an appropriate amount of deionized water, ensure that the Cd-EDTA is completely dissolved, and ensure uniformity by stirring or ultrasonic treatment. Finally, add the dissolved Cd-EDTA solution to the tailings, stir evenly, ensure that the complex is fully adsorbed on the surface of the tailings, and finally obtain a Cd-EDTA tailings sample of the required concentration.

[0042] After configuring the electrochemical workstation, an AC signal is applied to both sides of the nanopore sensor, and the response signal of the nanopore sensor is obtained within the preset frequency range to obtain a current blockade signal; Cu-EDTA is detected based on the current blockade signal corresponding to the Cd-EDTA sample and the standard Cd-EDTA solution of different concentrations.

[0043] Furthermore, the process of obtaining the current blocking signal of the standard Cd-EDTA solution includes: dropping standard Cd-EDTA solutions of different concentrations onto the surface of the nanopore sensor and maintaining a contact time of 30 minutes.

[0044] Specifically, the prepared Cd-EDTA solution was added dropwise to the surface of the nanopore sensor for a 30-minute contact reaction. The working electrode, reference electrode, and auxiliary electrode were set up using an electrochemical workstation, and a small-amplitude AC signal (usually 10mV or 50mV) was applied to measure the sensor's response to the signal in a frequency range of 10Hz to 100kHz. The impedance data recorded by the electrochemical workstation was used to analyze the change in charge transfer resistance (Rct) in the impedance spectrum using the Nyquist plot to evaluate the relationship between the Cd-EDTA complex concentration and the sensor response.

[0045] Electrochemical workstation Figure 1 As shown, Figure 1 (d) is a Faraday shielding box, and the nanopore sensor is fixed on Figure 1 (e) is between the fluid pools shown in the figure, and the nanopore on the nanopore sensor becomes the only channel in the fluid pool, and the fluid pool is divided into two independent fluid pools by the nanopore sensor; Figure 1 (b) The power supply shown is used to apply electrical signals to both sides of the nanopore sensor;

[0046] Figure 1 (a) shows a data processing module for Figure 1 (c) The patch clamp amplifier collects the electrical signal of the nanopore sensor and determines the baseline current and time current diagram.

[0047] The impedance data were analyzed using the Nyquist plot, and the relationship between the real part (Z') and the imaginary part (Z") of the impedance was plotted to observe the change of the charge transfer resistance (Rct) with the Cd-EDTA concentration. By comparing the Nyquist plots at different concentrations, the diameter of the semicircle arc or the fitted impedance data were quantified, and the detection performance and sensitivity of the sensor were further analyzed.

[0048] Concentration gradient experiments and performance evaluation

[0049] Replace the Cd-EDTA solution in the fluid cell, add 1mol / L, 2mol / L, 4mol / L, and 6mol / L Cd-EDTA solutions to the positive electrode side of the fluid cell, and add 0.5mol / L Cd-EDTA solution or electrolyte solution to the negative electrode side, and conduct four concentration gradient experiments. By comparing the Nyquist plots of Cd-EDTA solutions of different concentrations, the detection sensitivity and performance of the sensor are further evaluated.

[0050] The present invention improves the detection sensitivity of Cd-EDTA complexes and can achieve accurate detection at low concentrations. It realizes real-time, label-free detection and is suitable for monitoring pollutants in complex environments in mining areas. Through impedance spectrum and Nyquist plot analysis, high-precision, quantitative detection results are provided with good stability and repeatability. The introduction and functionalization of graphene improve the selectivity of the sensor and enhance the ability to capture target pollutants.

[0051] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A Cd-EDTA detection method based on solid-state nanopore detection technology, characterized in that: The following steps are involved: Obtaining a nanopore sensor, wherein the nanopore in the nanopore sensor is prepared by electron beam lithography; preparing electrolyte solution; preparing Cd-EDTA samples and preparing standard Cd-EDTA solutions of different concentrations; After configuring the electrochemical workstation, an AC signal is applied, and the response signal of the nanopore sensor is obtained within a preset frequency range to obtain a current blockade signal; Cu-EDTA is detected based on the current blockade signal corresponding to the Cd-EDTA sample and the standard Cd-EDTA solution of different concentrations.

2. The Cd-EDTA detection method based on solid-state nanopore detection technology according to claim 1, characterized in that: The process of fabricating nanopores using electron beam lithography includes: After cleaning the Si3N4 substrate, a layer of photoresist is coated on the surface, wherein the thickness of the photoresist is determined based on the aperture requirements of the nanopore; after the photoresist is coated, the uniformity of the photoresist coating is adjusted using a spin coating technique; an electron beam lithography machine scans the photoresist for exposure according to a preset pattern; after exposure, a development process is performed to remove the unexposed photoresist portion; the pattern is transferred to the Si3N4 substrate using a plasma etching technique, and the material in the exposed area is removed by etching to complete the preparation of the nanopore.

3. The Cd-EDTA detection method based on solid-state nanopore detection technology according to claim 1, characterized in that: The process of obtaining a nanopore sensor also includes: Graphene was grown on the surface of a metal catalyst using chemical vapor deposition. The graphene surface was functionalized using oxygen plasma treatment and chemical activation, and then transferred to a Si3N4 substrate using a solution transfer method.

4. The Cd-EDTA detection method based on solid-state nanopore detection technology according to claim 1, characterized in that: The electrolyte solution is a mixture of ammonia water and methanol, and the pH range of the electrolyte solution is 9.5-11.

5.

5. The Cd-EDTA detection method based on solid-state nanopore detection technology according to claim 1, characterized in that: The process of preparing Cd-EDTA samples includes: The required mass of the Cd-EDTA complex is calculated according to the required concentration and weighed; it is completely dissolved in deionized water and stirred or ultrasonically treated; the Cd-EDTA solution is added to the tailings and stirred evenly until the complex is fully adsorbed on the surface of the tailings, and finally a Cd-EDTA tailings sample of the required concentration is obtained.

6. The Cd-EDTA detection method based on solid-state nanopore detection technology according to claim 1, characterized in that: The standard Cd-EDTA solution includes four concentrations: 1 mol / L, 2 mol / L, 4 mol / L, and 6 mol / L.

7. The Cd-EDTA detection method based on solid-state nanopore detection technology according to claim 1, characterized in that: The process of obtaining the current blocking signal of the standard Cd-EDTA solution includes: dropping the standard Cd-EDTA solutions of different concentrations onto the surface of the nanopore sensor and maintaining a contact time of 30 minutes.

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