Small molecule detection method in nanoconfined space based on nanoporous adsorption material filling

Abstract

The present invention discloses a method for detecting small molecules in a nano-confined space based on filling with nano-porous adsorption materials. An integrated pipeline electrode IPE is constructed using a membrane material with a pipeline structure; nano-porous adsorption material N‑PAMs is modified on the inner and outer surfaces of the integrated pipeline electrode IPE to form a composite membrane electrode N‑PAMs@IPE; the composite membrane electrode N‑PAMs@IPE is placed in a solution of a small molecule target to be tested for immersion and adsorption, and an electrochemical workstation is used to detect the change in diffusion current before and after immersion and adsorption, and the concentration of the small molecule target is quantitatively detected according to the change in diffusion current. The present invention creates a nano-confined space that is conducive to sensing, can specifically identify and adsorb various small molecule pollutants, and can convert the weak changes caused by the target in the nano-confined space into multiple measurable signals, without the need for an additional large-volume electrode pool, and without the need for additional labeled immune markers.

Description

Technical Field

[0001] The invention relates to a quantitative detection method in the technical field of electrochemical analysis, and in particular to a small molecule detection method in a nano-confined space based on filling of nano-porous adsorption materials. Background Art

[0002] The serious consequences of the growing amount of small molecule chemical pollutants such as pesticides, antibiotics, and biotoxins have attracted global attention. Chemical pollutants not only affect the ecological environment, but also enter the human body through the ecological cycle or food chain, affecting life and health. For example, the long-term use of antibiotics such as tetracycline has led to problems such as bacterial resistance and cross-infection of pathogenic bacteria. Therefore, it is necessary to develop a detection technology that can analyze various small molecule chemical pollutants on-site, quickly and accurately.

[0003] In the field of new sensing materials, various membrane materials with pipeline structures are widely used in biological / chemical sensing, ion / molecule separation, salinity gradient power generation and other fields due to their excellent ion transmission performance. However, in the traditional sensing model that mainly monitors transmembrane ion currents, the ion transmission channel and the sensing electrode are separate systems, ignoring the function of the outer surface of the channel. In this regard, the emergence of integrated electrodes has improved the sensitivity of sensing. However, challenges still exist. Based on the most common steric hindrance effect, integrated pipeline electrodes focus on monitoring ectopic events of cells or macromolecular targets such as DNA and proteins. By monitoring the changes in the size and waveform of the ion current over time, information about the target can be obtained. However, when used for small-volume molecular detection, conventional pipelines do not have specific recognition functions and it is difficult to achieve signal transmission.

[0004] Therefore, there is an urgent need to develop electrode array membranes suitable for small molecule recognition and sensing. Summary of the invention

[0005] To solve the above problems, the present invention provides a method for detecting small molecules in nanoconfined space based on nanoporous adsorption materials. The prepared composite membrane can specifically identify and adsorb various small molecule pollutants, and combined with electrochemical detection based on integrated electrodes, it can convert the weak changes caused by the target in the nanoconfined space into multiple measurable signals, thereby realizing rapid and sensitive sensing of different chemical pollutants.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows:

[0007] 1) Using membrane materials with pipeline structures to construct an integrated pipeline electrode IPE, and subsequently using the integrated pipeline electrode to establish a dual-electrode system for electrochemical detection;

[0008] 2) The nanoporous adsorption material N-PAMs is modified on the inner and outer surfaces of the integrated pipeline electrode IPE to form a composite membrane electrode N-PAMs@IPE, so that the pore diameter of the pipeline structure is greatly reduced, and a nano-confined space is formed in the pipeline structure of the integrated pipeline electrode;

[0009] The inner and outer surfaces of the integrated pipeline electrode refer to the inner wall surface of the pipeline structure and the outer surface of the membrane material.

[0010] The constructed composite membrane electrode can recognize and adsorb small molecule targets.

[0011] 3) The composite membrane electrode N-PAMs@IPE is placed in a solution of the small molecule target to be tested for immersion and adsorption, and the change in diffusion current before and after immersion and adsorption is detected using an electrochemical workstation. The concentration of the small molecule target is quantitatively detected based on the change in diffusion current.

[0012] After the composite membrane electrode of the present invention captures the small molecule target, the inner and outer surface properties of the integrated pipeline electrode change, resulting in a change in the diffusion current of the pipeline structure through the integrated pipeline electrode, that is, a change in the diffusion current in the nano-confined space. This feature is used to detect the concentration of the small molecule target solution.

[0013] The integrated pipeline electrode is specifically prepared by depositing conductive layers of the same thickness on both surfaces of a membrane material having a pipeline structure. The membrane material having a pipeline structure has microscopic regular pores, specifically pores arranged parallel to each other and perpendicular to the membrane surface.

[0014] The conductive layers on the two surfaces are connected to the dual-electrode system by wires, and the conductive layers on the two surfaces serve as the working electrode and the counter electrode of the dual-electrode system respectively.

[0015] The membrane material with pipeline structure is a hollow porous structure, the initial pore diameter of the pores arranged in parallel to each other is in the nanometer and micrometer order, and the membrane thickness is in the micrometer to millimeter order.

[0016] After the integrated pipeline electrode is prepared, the conductive layer is sealed, and a fixed conductive area is exposed on the conductive layer as a sensing interface in contact with the outside world. The specific fixed area can be φ=3mm. 0.5MH2SO4 solution is added to the sensing interface in advance, and it is left to stand for 15 minutes, and then thoroughly rinsed with deionized water to remove contamination on the electrode surface.

[0017] The material types of the membrane material with a pipeline structure include, but are not limited to, anodized aluminum oxide (AAO) nanochannels, polyethylene terephthalate (PET) porous membranes, titanium dioxide (TiO2) nanochannels, and carbon nanotube (CNT) arrays;

[0018] The nanoporous adsorption materials (N-PAMs) have a three-dimensional porous structure and high-efficiency adsorption capacity, including various nanoporous materials with microporous and mesoporous structures, including but not limited to zeolites, metal organic frameworks (MOFs), covalent organic frameworks (COFs), microporous polymers (MPs), etc.

[0019] In the step 2), the nanoporous adsorption material N-PAMs is modified on the inner and outer surfaces of the integrated pipeline electrode, and the specific process is as follows: two reaction precursors for preparing the nanoporous adsorption material N-PAMs are weighed, and the two reaction precursors are dissolved in their respective solvents to prepare two reaction precursor solutions of certain concentrations; the reaction process is carried out in a self-made electrolytic cell, and the self-made electrolytic cell includes two electrolytic cells, each of which has a volume of about 3 mL and is used to store the precursor solution; through holes are opened on the side walls of the two electrolytic cells, and the through holes on the side walls of the two electrolytic cells are directly connected, and the integrated pipeline electrode is placed at the connection between the two through holes The integrated pipeline electrode is sandwiched between the through holes of the two electrolytic cells, so that the liquids in the two electrolytic cells can only be transmitted through the pipeline structure of the integrated pipeline electrode; then the two reaction precursor solutions are added to the two electrolytic cells on both sides of the integrated pipeline electrode respectively, and the two reaction precursor solutions are separated by the integrated pipeline electrode, so that the two reaction precursor solutions react and are modified at the integrated pipeline electrode. After the reaction is sealed at room temperature for 6 to 24 hours, the integrated pipeline electrode is taken out, rinsed with methanol 3 times, and then cleaned with deionized water and dried to obtain an integrated pipeline electrode modified with nanoporous adsorption material N-PAMs as a composite membrane electrode.

[0020] In a specific implementation, a rubber ring can be used to seal the end surface of the through hole to prevent liquid leakage.

[0021] The present invention utilizes a self-made electrolytic cell to process two reaction precursor solutions and an integrated pipeline electrode to obtain a composite membrane electrode, which can simultaneously have a large number of adsorption sites and fast ion transmission channels, and can easily control the pore size of the pipeline structure to construct a nano-confined space.

[0022] In step 3), the process of small molecule target adsorption and electrochemical detection is as follows:

[0023] Before immersion, the composite membrane electrode and the wire of the electrochemical workstation are connected, and the diffusion current of the composite membrane electrode is detected by the electrochemical workstation;

[0024] Then, the composite membrane electrode is immersed in the solution of the small molecule target to be tested, and is immersed and adsorbed for 0.5 to 2 hours at room temperature. The composite membrane electrode is then taken out, cleaned with deionized water and dried. The composite membrane electrode and the wire of the electrochemical workstation are connected, and the diffusion current of the composite membrane electrode is detected using the electrochemical workstation.

[0025] The method of using an electrochemical workstation to detect the diffusion current of a composite membrane electrode is as follows: the conductive layers on the two surfaces of the composite membrane electrode are connected to the two electrodes of the electrochemical workstation with wires, and the conductive layers on the two surfaces are used as the working electrode and the counter electrode of the dual-electrode system respectively; then 5 μL of a 1 mM K3Fe(CN)6 solution is dripped onto the sensing surface of the conductive layer on one surface of the composite membrane electrode, cyclic voltammetry (CV) is used to scan 5 times, and then an electrochemical differential pulse voltammetry (DPV) test is performed to collect the diffusion current.

[0026] All the above solution preparations and reactions of the present invention are carried out at room temperature of 25°C.

[0027] The small molecule target can be pesticides, antibiotics, biological toxins and other common small molecule chemical pollutants in the environment.

[0028] The quantitative detection of the concentration of the small molecule target according to the change of the diffusion current is specifically: the measured change of the diffusion current is compared with the curve relationship established by fitting between the diffusion current change obtained by pre-calibration and the concentration of the small molecule target to obtain the corresponding small molecule target concentration result.

[0029] The curve relationship is obtained by setting different small molecule target concentrations in advance for multiple times to conduct the same experiment to obtain corresponding diffusion current changes, and the diffusion current changes and the corresponding small molecule target concentrations are fitted to establish a curve model.

[0030] The present invention controls the diameter of the pipeline by modifying the inner wall and outer surface of the membrane material with a pipeline structure with porous nanomaterials with high adsorption capacity, thereby creating a nano-confined space that is conducive to sensing. The prepared composite membrane can specifically identify and adsorb various small molecular pollutants, and can convert the weak changes caused by the target in the nano-confined space into multiple measurable signals.

[0031] The beneficial effects of the method of the present invention are:

[0032] The present invention combines functional nanoporous adsorption materials with integrated pipeline electrodes, and can simultaneously reflect changes in the inner and outer surfaces of the pipeline without the need for an additional large-volume electrode pool.

[0033] The present invention easily creates a nano-confined space in the pipeline structure, and the composite membrane electrode has both small molecule recognition and signal transmission functions without the need for additional immune markers.

[0034] The present invention, combined with sensitive electrochemical detection, can convert the slight changes caused by small molecule pollutants into multiple measurable readings, such as differential pulse voltammetry (DPV), cyclic voltammetry (CV) and conductivity, further expanding the application prospects of nanofunctional materials in the field of sensing.

[0035] The present invention provides a simple method, brings new research ideas for the use of membrane materials with pipeline structures for small molecule detection, and further ensures agricultural and environmental safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the detection of tetracycline using ZIF-8 modified AAO-Au (ZIF-8@AAO-Au) composite membrane electrode.

[0037] Figure 2 This is a surface scanning electron microscope image of the AAO-Au integrated pipeline electrode.

[0038] Figure 3 This is the element distribution of the AAO-Au integrated pipeline electrode.

[0039] Figure 4 This is the surface scanning electron microscopy image of the prepared small-pore ZIF-8@AAO-Au composite membrane electrode.

[0040] Figure 5 This is a cross-sectional scanning electron microscope image of the prepared small-pore ZIF-8@AAO-Au composite membrane electrode.

[0041] Figure 6 This is the electrochemical signal response diagram of the ZIF-8@AAO-Au composite film electrode when used to detect tetracycline at different concentrations.

[0042] Figure 7 This is the fitting standard curve of the ZIF-8@AAO-Au composite film electrode for the detection of tetracycline at different concentrations.

[0043] Figure 8 Cross-sectional scanning electron microscopy images of ZIF-8@AAO-Au composite membrane electrodes with different pore sizes.

[0044] Fig. 9 This is the pore size distribution diagram of ZIF-8@AAO-Au composite membrane electrodes with different pore sizes. DETAILED DESCRIPTION

[0045] In order to enable those skilled in the art to better understand the technical solution of the present invention, the method provided by the present invention is described in detail below in conjunction with the accompanying drawings and embodiments. However, it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0046] Embodiments of the present invention are as follows:

[0047] Embodiment 1:

[0048] Detection of tetracycline using ZIF-8 modified AAO-Au composite film electrode (ZIF-8@AAO-Au):

[0049] (1) Preparation of composite membrane electrode

[0050] The same thickness of gold layer was deposited on both sides of the anodized aluminum oxide (AAO) nanochannel (thickness 60μm, pore size 20-30nm), and the sputtering process was set to 30mA and the sputtering time was 400s. After the gold layer was sprayed on both sides, the AAO electrode sheet was removed. Aluminum foil was used as a wire to connect the gold layers on both sides of the AAO to form a dual-electrode system, and the gold layers on both sides of the AAO were used as the working electrode and the counter electrode respectively. The aluminum foil and the gold layers on both sides of the AAO were sealed with tape, exposing only a circular conductive area with a diameter of 3mm as the sensing interface in contact with the solution. After the sealing was completed, 5μL of 0.5M H2SO4 solution was added to the sensing interface, and it was left to stand for 15 minutes, and then rinsed thoroughly with deionized water to remove contamination on the electrode surface. After drying, it was tested with a multimeter to ensure that the circuit connection was normal to obtain the AAO-Au integrated pipeline electrode, which was used as a substrate for the growth of zeolite imidazole framework-8 (ZIF-8) MOF.

[0051] ZIF-8 was grown in situ on the AAO-Au integrated pipeline electrode by the reverse diffusion method. Weigh 0.274g Zn(NO3)2·6H2O crystals and dissolve them in 50mL deionized water. Then weigh 5.665g 2-methylimidazole and dissolve it in 50mL deionized water (due to the large amount of 2-methylimidazole, continuous ultrasonic assistance is required until it is completely dissolved). The ZIF-8 modification process was carried out in a homemade 3D printed electrolytic cell. The electrolytic cell consists of two electrolytic cells. Each electrolytic cell has a volume of about 3mL and is used to store the reaction solution. Each electrolytic cell has a circular hole (φ=1cm) for the liquid on both sides to communicate with each other, and they are precisely aligned. The AAO-Au integrated pipeline electrode is sandwiched between the through holes of the two electrolytic cells, so that the liquid in the two electrolytic cells can only be transmitted through the nanochannels of the AAO-Au integrated pipeline electrode; and it is sealed with a rubber ring to prevent liquid leakage. Add 2 mL of freshly prepared Zn(NO3)2·6H2O solution to the electrolytic cell on one side of the electrolytic cell, and then add the same volume of 2-methylimidazole solution to the electrolytic cell on the other side of the electrolytic cell. Seal at room temperature for 12 hours. Take out the composite membrane electrode, wash it three times with a large amount of methanol, then wash it with deionized water, and dry it at 60°C for 1 hour to obtain the ZIF-8 modified AAO-Au composite membrane electrode (ZIF-8@AAO-Au).

[0052] (2) Characterization of composite membrane electrode

[0053] Before ZIF-8 modification, the AAO-Au integrated pipeline electrode was characterized by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). After the gold layer was sprayed, gold nanoparticles were deposited on the surface of the AAO-Au integrated pipeline electrode, and open channels with a diameter of about 25 nm were retained ( Figure 2). The cross-sectional SEM images showed ordered and parallel nanochannels. The surface composition of AAO-Au was investigated using EDS. As expected, oxygen, aluminum, and gold signals were observed ( Figure 3 ). The above results show that the conductive gold layer is successfully deposited on the AAO membrane without destroying the geometry of the nanochannels, which is beneficial to maintain its ion transport performance.

[0054] After ZIF-8 modification, the morphology of the prepared ZIF-8@AAO-Au composite membrane electrode was characterized by SEM. ZIF-8 crystals were evenly distributed on one side of the composite membrane electrode ( Figure 4 ). Cross-sectional SEM showed that ZIF-8 crystals were successfully modified in the nanochannels of AAO, resulting in a decrease in the pore diameter to about 4 nm (Figure 5).

[0055] (3) Tetracycline detection

[0056] Before adsorbing tetracycline, the ZIF-8@AAO-Au composite membrane electrode was connected to the wire of the electrochemical workstation, and the diffusion current I0 of the composite membrane electrode was detected by the electrochemical workstation;

[0057] Weigh 5 mg of tetracycline standard in 5 mL of deionized water, and dilute to obtain a series of tetracycline solutions with concentration gradients. Immerse the ZIF-8@AAO-Au composite membrane electrode in 5 mL of tetracycline solutions of different concentrations and soak for adsorption at room temperature for 1 hour. Take out the composite membrane electrode, wash it with deionized water and dry it. Connect the composite membrane electrode to the wires of the electrochemical workstation, and use the two sides of the electrode as the working electrode and the counter electrode respectively. Add 5 μL of 1 mM K3Fe(CN)6 solution to the surface of one side of the counter electrode of ZIF-8@AAO-Au, first perform cyclic voltammetry CV scan for 5 cycles until the current is stable, and then perform electrochemical differential pulse voltammetry DPV test to record the size of the diffusion current I( Figure 6 The current change rate before and after adsorption was used as the quantitative response signal of tetracycline concentration (α=(I0–I) / I0). The standard curve established is as follows Figure 7 As shown, as the concentration of tetracycline increases, the diffusion current decreases. There is a linear relationship between α and the logarithm of the tetracycline concentration Y = 9.3412Ln(X) + 20.586, and the correlation coefficient R 2 =0.9955. The linear detection range is 0.4 to 1000 ng mL -1 , the detection limit was 0.17 ng mL -1 (S / N=3).

[0058] For the detection of tetracycline in the buffer solution, the measured rate of change of the diffusion current can be compared with the above fitting curve to obtain the corresponding tetracycline concentration result.

[0059] This method does not require additional biomacromolecule labeling, but still exhibits good detection capabilities, thanks to the synergistic small molecule recognition and signal amplification effects inside and outside the constructed nanoconfined space. In addition, the detection unit integrated at the end of the nanochannel enables [Fe(CN)6] 3- Once diffused through the channel, it can be detected by the Au electrode on the surface, avoiding the situation in traditional nanochannels where the signal probe is greatly diluted by the buffer solution.

[0060] (4) Detection mechanism

[0061] like Figure 1 As shown. The filling of ZIF-8 on the inner wall of AAO-Au reduces the pore size to ~4nm, creating a nano-confined space that is conducive to sensing. At the same time, the outer surface of the composite membrane electrode is also covered with ZIF-8, and its adsorption sites are fully exposed. Under the detection conditions, after the positively charged ZIF-8 inside and outside the channel adsorbs the negatively charged tetracycline small molecules, its surface properties change, significantly increasing the surface negative charge of the nanochannel (from positive to negative). The double electrical layer overlaps in the channel, and the electrochemical probe [Fe(CN)6] 3- The electrostatic repulsion is enhanced; at the same time, the negatively charged electron cloud on the surface also inhibits the [Fe(CN)6] 3- Diffusion. Under the combined action of the inner and outer surfaces,

[0062] [Fe(CN)6] 3- Diffusion is hindered. Due to the [Fe(CN)6] 3- The electrochemical reaction is a diffusion-controlled process, and the current response is proportional to its concentration. Therefore, when tetracycline is present, the diffusion current decreases, and the diffusion current decreases as the concentration of tetracycline increases. The rate of change of the diffusion current can be used as a signal for quantitative detection of tetracycline.

[0063] Embodiment 2:

[0064] Preparation of composite membrane electrodes of different sizes:

[0065] The modification and growth of ZIF-8 in AAO-Au integrated pipeline electrodes with two other pore sizes were studied. After 12 hours of in situ growth, ZIF-8 can achieve controllable growth inside AAO nanochannels with different pore sizes, and the growth of ZIF-8 does not destroy the channel structure. For large-pore (160-200nm) AAO-Au, the growth of dodecahedral ZIF-8 crystals was observed, but there was still a large free space, and the average pore size of the corresponding ZIF-8@AAO-Au composite membrane electrode was statistically ~135nm ( Figure 8). The ZIF-8 in the medium pore size (40-70nm) AAO-Au is smaller and more densely distributed. The average pore size of the corresponding ZIF-8@AAO-Au composite membrane electrode is statistically ~15nm ( Fig. 9 ). The above results show that this method is universal for pipes with different apertures and can easily adjust the aperture of the pipe to meet different needs.

[0066] Embodiment 3:

[0067] Spiked detection of tetracycline in chicken breast;

[0068] Fresh chicken breast purchased from a supermarket was processed into minced meat using a homogenizer. 0.5 g of minced chicken was weighed and placed in 1 mL of ethyl acetate, and then ultrasonically treated for 30 min. The treated chicken sample was centrifuged at 10,000 rpm for 10 min. The supernatant was collected and diluted ten times with deionized water to prepare tetracycline solutions of different concentrations (5, 10, 100 ng mL -1 ). The ZIF-8@AAO-Au composite membrane electrode prepared according to the method in Example 1 was used for soaking and adsorption of tetracycline solution of chicken. Before and after adsorption, the electrochemical method in Example 1 was used to detect the recovery rate ranging from 81.28 to 97.19% (Table 1). It shows that the prepared ZIF-8@AAO-Au composite membrane electrode has a strong ability to resist matrix interference and can be used for actual sample detection.

[0069] Table 1

[0070]

[0071] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the method of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for detecting small molecules in nano-confined space based on nanoporous adsorption material filling, characterized in that: Methods include 1) Using membrane materials with pipeline structures to construct integrated pipeline electrodes IPE; After the integrated pipeline electrode is prepared, the conductive layer is sealed, and a fixed area of ​​the conductive layer is exposed as a sensing interface in contact with the outside world. A 0.5 M H2SO4 solution is added to the sensing interface in advance, and the solution is allowed to stand for 15 minutes for cleaning, and then thoroughly rinsed with deionized water. 2) The nanoporous adsorption material N-PAMs is modified on the inner and outer surfaces of the integrated pipeline electrode IPE to form a composite membrane electrode N-PAMs@IPE; In the step 2), the nanoporous adsorption material N-PAMs is modified on the inner and outer surfaces of the integrated pipeline electrode, and the specific process is as follows: Two reaction precursors for preparing nanoporous adsorption material N-PAMs were weighed, and the two reaction precursors were dissolved in their respective solvents to prepare two reaction precursor solutions; the reaction process was carried out in a self-made electrolytic cell, which included two electrolytic cells, through holes were opened on the side walls of the two electrolytic cells, the through holes on the side walls of the two electrolytic cells were directly connected, and an integrated pipeline electrode was placed at the connection between the two through holes, so that the liquids in the two electrolytic cells could only be transmitted through the pipeline structure of the integrated pipeline electrode; then the two reaction precursor solutions were added to the two electrolytic cells on both sides of the integrated pipeline electrode, so that the two reaction precursor solutions reacted and modified at the integrated pipeline electrode, and the integrated pipeline electrode was taken out after sealing and reacting for 6 to 24 hours at room temperature, rinsed with methanol 3 times, and then washed with deionized water and dried to obtain the integrated pipeline electrode modified with nanoporous adsorption material N-PAMs as a composite membrane electrode; 3) The composite membrane electrode N-PAMs@IPE is placed in a solution of a small molecule target to be tested for immersion and adsorption, and the change in diffusion current before and after immersion and adsorption is detected using an electrochemical workstation, and the concentration of the small molecule target is quantitatively detected based on the change in diffusion current; In step 3), the process of small molecule target adsorption and electrochemical detection is as follows: Before immersion, the composite membrane electrode and the wire of the electrochemical workstation are connected, and the diffusion current of the composite membrane electrode is detected by the electrochemical workstation; Then, the composite membrane electrode was immersed in the solution of the small molecule target to be tested, and was immersed and adsorbed for 0.5 to 2 h at room temperature. Then, the composite membrane electrode was taken out, washed with deionized water and dried. The composite membrane electrode and the wire of the electrochemical workstation were connected, and the diffusion current of the composite membrane electrode was detected using the electrochemical workstation.

2. The method for detecting small molecules in nano-confined space based on nanoporous adsorption material filling according to claim 1, characterized in that: The integrated pipeline electrode is specifically prepared by depositing conductive layers of the same thickness on two surfaces of a membrane material having a pipeline structure, and the membrane material having a pipeline structure specifically refers to pores arranged parallel to each other and perpendicular to the membrane surface.

3. The method for detecting small molecules in nano-confined space based on nanoporous adsorption material filling according to claim 1, characterized in that: The initial pore size of the pores of the membrane material with a pipeline structure is in the nanometer and micrometer order, and the membrane thickness is in the micrometer to millimeter order.

4. The method for detecting small molecules in nano-confined space based on nanoporous adsorption material filling according to claim 1, characterized in that: The material types of the membrane material with a pipeline structure include anodized aluminum oxide (AAO) nanochannels, polyethylene terephthalate (PET) porous membranes, titanium dioxide (TiO2) nanochannels and carbon nanotube (CNT) arrays; The nanoporous adsorption material has a three-dimensional porous structure, including various nanoporous materials with microporous and mesoporous structures.

5. The method for detecting small molecules in nano-confined space based on nanoporous adsorption material filling according to claim 1, characterized in that: The method of using an electrochemical workstation to detect the diffusion current of the composite membrane electrode is as follows: the conductive layers on the two surfaces of the composite membrane electrode are connected to the two electrodes of the electrochemical workstation with wires, and the conductive layers on the two surfaces are used as the working electrode and the counter electrode of the dual-electrode system respectively; then 1 mM K3Fe(CN)6 solution is added dropwise to the conductive layer on one surface of the composite membrane electrode, and cyclic voltammetry (CV) is used to scan 5 times, and then electrochemical differential pulse voltammetry (DPV) is performed to collect the diffusion current.

6. The method for detecting small molecules in nano-confined space based on nanoporous adsorption material filling according to claim 1, characterized in that: The quantitative detection of the concentration of the small molecule target according to the change of the diffusion current is specifically: the measured change of the diffusion current is compared with the curve relationship established by fitting between the diffusion current change obtained by pre-calibration and the concentration of the small molecule target to obtain the corresponding small molecule target concentration result.

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