A mww molecular sieve composite material with high adsorption capacity and conductivity, an electrochemical sensor and a preparation method and application thereof

Abstract

This invention relates to the fields of nanomaterials and electrochemical catalysts, specifically to a high-adsorption-capacity and high-conductivity MWW molecular sieve composite material, an electrochemical sensor, its preparation method, and its application. Specifically, it relates to the application in detecting chlorogenic acid content. This molecular sieve composite material is prepared by using cyclohexylamine as a template agent to obtain an aluminosilicate gel, then introducing tin dioxide into the aluminosilicate gel using an in-situ synthesis method, and combining carbon nanotubes with sheet-like SnO2-MWW molecular sieves. The resulting MWW molecular sieve composite material possesses high specific surface area, high adsorption capacity, and excellent conductivity. When applied to an electrochemical sensor for detecting chlorogenic acid content, it offers advantages such as a wide detection range (1~1500 μmol / L) and a low detection limit (0.02 μmol / L), along with excellent stability, reproducibility, anti-interference, and mechanical stability. It can accurately determine the chlorogenic acid content in drugs, and the electrochemical sensor has a simple structure, low cost, and promising application prospects.

Description

Technical Field

[0001] This invention relates to the fields of nanomaterials and electrochemical catalysts, specifically to a high-adsorption-capacity and high-conductivity MWW molecular sieve composite material, an electrochemical sensor, its preparation method and application, and particularly to its application in detecting chlorogenic acid content. Background Technology

[0002] MWW molecular sieves are aluminosilicates, belonging to porous materials, possessing a unique pore structure, high specific surface area, good diffusivity, and excellent hydrothermal stability. Their pore sizes are uniform and exhibit shape-selective properties, enabling molecular-level sieving based on differences in molecular size and polarity. Currently, these characteristics of MWW molecular sieves have led to their widespread application in separation, catalytic reactions, and other fields.

[0003] Chlorogenic acid (CGA) is a common dietary polyphenol (chemical formula C32-C4 ... 16 H 18 O9 (CGA) is widely found in coffee, tea, fruits, and certain herbs, and is renowned for its antioxidant, anti-inflammatory, antibacterial, and anticancer properties. Due to its potential in alleviating chronic diseases such as cardiovascular disease, diabetes, and obesity, CGA has attracted considerable attention as a functional food ingredient with health-promoting effects. Dietary intake affects serum CGA concentrations in humans, which are typically below 1 μM. Maintaining a concentration below 10 μM through diet can provide health benefits, while excessive intake may cause adverse reactions such as nausea, allergic reactions, or oxidative stress. For sensitive populations such as pregnant women and children, CGA intake must be strictly controlled to avoid developmental risks. These considerations highlight the necessity for accurate and rapid monitoring of CGA in food; however, existing detection methods are often limited by complex matrix interference and insufficient sensitivity in trace analysis. Therefore, developing efficient, reliable, and easy-to-use detection technologies is crucial for food quality assessment, nutritional guidance, and personalized health management.

[0004] Currently, there are various methods for detecting chlorogenic acid (CGA) content, each with its own advantages and disadvantages. For example, the common high-performance liquid chromatography (HPLC) method for CGA determination, while highly accurate, is expensive, complex, and time-consuming. Mass spectrometry (MS), although highly sensitive and specific, is also costly and complex. Fluorescence spectroscopy (FS) offers high sensitivity and accuracy, but suffers from poor stability. Capillary electrophoresis (HPCE) offers advantages such as diverse operating modes and small sample volumes, but it is also time-consuming, labor-intensive, and costly. These traditional methods not only require sophisticated instruments but also involve cumbersome sample pretreatment, making real-time and rapid monitoring inconvenient.

[0005] Electrochemical analysis is an important instrumental analytical method. Based on the electrochemical properties and changes of substances in solution, it establishes qualitative and quantitative analysis of components by relating electrical quantities such as potential, current, and charge to certain quantities of the analyte. Compared with high-performance liquid chromatography, mass spectrometry, and capillary electrophoresis, this electrochemical analysis method has significant advantages. It does not require expensive equipment, has no complex sample preparation steps, is easy to operate, and saves time and effort. The electrochemical sensors involved in this method have advantages such as simple structure, convenient operation, wide detection linearity, and low cost. The sensitivity of electrochemical sensors mainly depends on the performance of the electrode surface modification material; however, the sensitivity, detection limit, and detection range of electrochemical sensors currently used for detecting chlorogenic acid still need improvement.

[0006] Furthermore, in the preparation of MWW molecular sieves, template agents and silicon sources play crucial roles in the synthesis, controlling the specific surface area and pore volume of the molecular sieve material by regulating its crystallinity and pore structure. However, the specific surface area and pore volume of MWW molecular sieves prepared using commonly used template agents in existing technologies are still insufficient. Additionally, electrode conductivity can promote electron transfer during electrochemical detection, improving the sensitivity of electrochemical sensors. However, MWW molecular sieves themselves have poor conductivity, resulting in insufficient accuracy and sensitivity when used in electrochemical sensors for detecting chlorogenic acid. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, the first objective of this invention is to provide a method for preparing a high adsorption capacity and conductivity MWW molecular sieve composite material. This method is simple, and the resulting MWW molecular sieve composite material has the advantages of large specific surface area, high adsorption capacity, and good conductivity.

[0008] To overcome the shortcomings of the prior art, the second objective of this invention is to provide a high adsorption capacity and conductivity MWW molecular sieve composite material, which has the advantages of large specific surface area, high adsorption capacity and good conductivity.

[0009] A third objective of this invention is to provide an electrochemical sensor.

[0010] The fourth objective of this invention is to provide a method for preparing an electrochemical sensor.

[0011] The fifth objective of this invention is to provide an application of an electrochemical sensor in detecting chlorogenic acid content.

[0012] To achieve the first objective of the invention, the technical solution adopted by the present invention is as follows:

[0013] A method for preparing MWW molecular sieve composite materials with high adsorption capacity and conductivity is provided, comprising the following steps:

[0014] S1. Preparation of aluminosilicate gel: Cyclohexylamine, sodium aluminate, sodium hydroxide, and silica sol are mixed in water to obtain aluminosilicate gel;

[0015] S2. Preparation of sheet-like SnO2-MWW molecular sieve: The aluminosilicate gel is mixed with tin dioxide in situ, then heated and reacted. After filtration, washing, drying and calcination, sheet-like MWW molecular sieve loaded with tin dioxide material is obtained, which is the sheet-like SnO2-MWW molecular sieve.

[0016] S3, Loaded carbon nanotubes: The sheet-like SnO2-MWW molecular sieve and carbon nanotubes are added to a chitosan solution, stirred and reacted, then centrifuged, the precipitate is collected, washed and dried to obtain CNTs@SnO2-MWW composite material, that is, the MWW molecular sieve composite material with high adsorption capacity and conductivity is obtained.

[0017] In step S3, the chitosan solution acts as a robust and biocompatible "glue" for the interdoping of sheet SnO2-MWW molecular sieves and carbon nanotubes, and can effectively disperse the sheet SnO2-MWW molecular sieves and carbon nanotubes, preventing their aggregation.

[0018] In the preparation of the sheet-like SnO2-MWW molecular sieve, the SnO2 used is an n-type semiconductor, which has higher electron mobility and better thermal stability compared to other metal oxides. Furthermore, the moderate redox properties and acidity of SnO2 can produce an ideal synergistic effect with the strong acid sites of the MWW molecular sieve. The reaction mechanism for obtaining the sheet-like SnO2-MWW molecular sieve through in-situ synthesis is as follows:

[0019] (1) Electrostatic interaction and coordination between tin dioxide and aluminosilicate gel: In the synthesis system, Sn 4+ Ions are attracted to the negatively charged primary species of aluminosilicate through electrostatic interactions. Because Sn... 4+ It has strong Lewis acidity and can strongly coordinate with hydroxyl (-OH) and oxygen atoms in the gel to form ≡Si-O-Sn- or [Al-O]-Sn- type bonds.

[0020] (2) Co-assembly between tin dioxide and aluminosilicate gel: The crystallization of MWW molecular sieves is an ordered assembly process around a template agent. Sn species may be "encapsulated" in complex micelles or pre-structured units formed by aluminosilicate species. In this case, the SnO2 precursor is no longer an external "guest" but participates in the self-assembly process of the molecular sieve to a certain extent, becoming part of the gel matrix.

[0021] (3) Co-precipitation and in-situ dehydration condensation between tin dioxide and aluminosilicate gel: Under the high temperature and high pressure environment of hydrothermal crystallization, SnO2 nanocrystal nuclei are confined in situ between, on the surface of, or inside the growing MWW layers. This greatly inhibits the free migration of SnO2 particles, thereby obtaining ultra-small and uniform nanoparticles. During molecular sieve crystallization, Sn-OH on the SnO2 surface undergoes in-situ dehydration condensation with Si-OH / Al-OH at the ends of the MWW framework, forming strong Si-O-Sn and Al-O-Sn covalent bonds.

[0022] In the carbon nanotube loading step, the reaction mechanism between the carbon nanotubes and the sheet-like SnO2-MWW molecular sieve is as follows:

[0023] (1) The interfacial physical interaction between carbon nanotubes (CNTs) and sheet-like SnO2-MWW molecular sieves is the basis for their bonding. This interfacial physical interaction includes the following three types: 1) π-π stacking effect: The six-membered ring (siloxane ring) in the MWW molecular sieve structure has electron-rich properties and can undergo π-π stacking with the large π bonds on the graphite wall of CNTs. This is a relatively weak but wide-ranging non-covalent bond that can "adsorb" or "wrap" SnO2-MWW sheets on the surface of CNTs, providing preliminary and reversible binding force; 2) Hydrogen bonding: The carboxyl (-COOH) functional groups on the surface of carbon nanotubes can form hydrogen bonds with the silanol (Si-OH) or framework oxygen on the surface of the SnO2-MWW molecular sieve sheets. This force can effectively enhance interfacial bonding and stability; 3) Spatial confinement and entanglement: One-dimensional fibrous CNTs can serve as a three-dimensional network framework, while two-dimensional sheet-like MWW can partially wrap or overlap on CNTs like "bandages" to form an interlocking structure. This mechanical interlocking effect can effectively prevent the stacking of SnO2-MWW sheets and the aggregation of CNTs, further enhancing structural stability.

[0024] (2) The interfacial chemical bonding (mainly strong covalent bonds) between carbon nanotubes and sheet-like SnO2-MWW molecular sieves includes the following two cases: 1) The -COOH on the functionalized CNTs undergoes dehydration condensation with the Si-OH or Sn-OH on the SnO2-MWW surface to form CO-O-Si or CO-O-Sn covalent bonds, thereby providing the strongest interfacial bonding, ensuring efficient electron transport and excellent structural integrity; 2) In SnO2-MWW, the exposed SnO2 nanoparticles will directly contact the CNTs, and the oxygen-containing functional groups (-COOH, -OH) of the functionalized CNTs can directly react with the Sn-OH on the SnO2 surface to form Sn-OC covalent bonds, which is very easy to occur in in-situ synthesis or subsequent heat treatment.

[0025] In addition, the layered MWW molecular sieve loaded with CNTs, compared to other molecular sieves in traditional technologies (such as Y-type, ... ZSM-5 (Beta) loaded with CNTs has the following advantages: 1) The sheet-like MWW molecular sieve is a two-dimensional sheet with open surfaces and short channels, allowing reactants to directly access active sites from both the channels and the surface; 2) The accessibility of active sites is extremely high, with most acid sites and loaded SnO2 sites located on the exposed surface, facilitating contact with chlorogenic acid molecules in solution; 3) The composite mechanism of sheet-like MWW molecular sieve and CNTs is a surface-to-line close contact, where the two-dimensional sheet can "wrap" or "overlap" with one-dimensional CNTs to form a stable heterojunction with a large contact area; 4) Mass transfer and diffusion efficiency is extremely fast, as the open structure of the sheet-like MWW molecular sieve eliminates microporous diffusion resistance, allowing chlorogenic acid molecules (which are relatively large) to quickly reach most active sites; 5) High structural stability, with a strong mechanical interlocking effect between the sheet-like MWW molecular sieve and CNTs, resulting in a stable composite structure that is not easily damaged during electrolyte stirring or scanning. In addition, the CNTs loaded on the layered MWW molecular sieve have performance advantages over other molecular sieves in the electrochemical detection of chlorogenic acid, including higher sensitivity, faster response speed, and enhanced anti-fouling and stability.

[0026] Further, in step S1, the molar ratio of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol, and water is (2~20):(0.1~5):(0.1~5):(5~50):(100~400); preferably, the molar ratio is (5~15):(0.5~2):(0.5~2):(10~30):(150~350); more preferably, the molar ratio is 9:1:1:20:240.

[0027] In this invention, cyclohexylamine is used as the template agent. This structure guides the formation of layered MWW molecular sieves, shortens the diffusion path of the MWW molecular sieve, and reduces its diffusion resistance. Cyclohexylamine can be used to prepare MWW molecular sieves with a layered structure in a one-step process, greatly increasing the specific surface area and pore volume of the MWW molecular sieve. A larger specific surface area, higher adsorption capacity, and better diffusion performance of the molecular sieve promotes the participation of more active sites in the reaction, allowing more target molecules to be reacted rapidly in a short time, thereby improving the analytical performance of the sensor. Appropriate proportions of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol, and water can result in layered MWW molecular sieves with larger specific surface area, adsorption capacity, and diffusion performance.

[0028] In addition, tin dioxide is a semiconductor material with good conductivity. Introducing it into the layered MWW molecular sieve framework through in-situ synthesis can significantly enhance the conductivity of the molecular sieve. Further composite with highly conductive carbon nanotubes can greatly improve the redox capability of the prepared MWW molecular sieve composite material as the working electrode of electrochemical sensor.

[0029] In addition, in the preparation of sheet SnO2-MWW molecular sieves, since semiconductor tin dioxide has excellent conductivity, loading tin dioxide onto sheet MWW molecular sieves through in-situ synthesis can enhance the intrinsic conductivity of the molecular sieve. Furthermore, by further compounding with highly conductive and diffusive carbon nanotubes, the resulting MWW molecular sieve composite material can greatly enhance its electrocatalytic activity as a working electrode of an electrochemical sensor.

[0030] The mixing method is magnetic stirring, the temperature of the magnetic stirring is 20℃~40℃, and the stirring time is 2h~4h; and / or

[0031] Further, in step S2, the molar ratio of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol, water, and tin dioxide is (2~20):(0.1~5):(0.1~5):(5~50):(100~400):(0.1~5); preferably, the molar ratio is (5~15):(0.5~2):(0.5~2):(10~30):(150~350):(0.5~2); more preferably, the molar ratio is 9:1:1:20:240:1.

[0032] The in-situ mixing method is magnetic stirring, the magnetic stirring temperature is 20℃~40℃, and the magnetic stirring time is 2h~4h; and / or, the heating reaction temperature is 140℃~180℃, and the heating reaction time is 24h~54h; and / or, the drying temperature is 100℃~150℃, and the drying time is 2h~6h; and / or, the calcination temperature is 500℃~700℃, and the calcination time is 3h~5h; and / or, the washing is done with deionized water.

[0033] In step S2, during the preparation of the sheet-like SnO2-MWW molecular sieve, a suitable molar ratio during the introduction of tin dioxide into the aluminosilicate gel ensures that the resulting sheet-like SnO2-MWW molecular sieve exhibits excellent conductivity and maintains a large specific surface area. An excessively high tin dioxide ratio leads to excessive clogging of the SnO2-MWW molecular sieve pores, reducing the specific surface area and pore volume, thereby decreasing the number of active sites. Conversely, an excessively low tin dioxide ratio results in insufficient tin dioxide content introduced into the SnO2-MWW molecular sieve framework, leading to poor conductivity of the sheet-like SnO2-MWW molecular sieve.

[0034] Furthermore, in the preparation of sheet-like SnO2-MWW molecular sieves, this invention controls the reaction temperature appropriately, enabling the prepared sheet-like SnO2-MWW molecular sieves to possess a large specific surface area and adsorption capacity. However, if the reaction temperature is too high, the MWW molecular sieve crystallizes too quickly, leading to the formation of impurity crystals; if the reaction temperature is too low, the energy for MWW molecular sieve growth is insufficient, resulting in a slow crystallization rate and the formation of amorphous crystals, thus failing to form well-structured sheet-like SnO2-MWW molecular sieves.

[0035] Furthermore, in step S3, the mass ratio of the sheet-like SnO2-MWW molecular sieve to the carbon nanotube is (0.1~3):(0.1~5); preferably, the mass ratio is (0.5~2):(0.1~3); more preferably, the mass ratio is 1:1.

[0036] In step S3, during the loading of carbon nanotubes, the present invention, by controlling the appropriate composite ratio of the sheet-like SnO2-MWW molecular sieve and carbon nanotubes, enables the obtained MWW molecular sieve composite material to possess excellent conductivity and catalytic performance. Furthermore, if the composite ratio of the sheet-like SnO2-MWW molecular sieve and carbon nanotubes is too low, the specific surface area and active sites of the obtained MWW molecular sieve composite material will decrease, thereby reducing its electrochemical response performance; if the composite ratio of the sheet-like SnO2-MWW molecular sieve and carbon nanotubes is too high, the conductivity of the obtained MWW molecular sieve composite material will decrease, thereby reducing its catalytic performance and electrochemical response performance.

[0037] Furthermore, the mass ratio of the chitosan solution to the sheet-like SnO2-MWW molecular sieve is 1:(3~7); and / or, the concentration of the chitosan solution is 0.02wt%~0.3wt%; and / or, the stirring reaction temperature is 25℃~40℃, and the stirring reaction time is 2h~4h; and / or, the drying temperature is 80℃~100℃, and the drying time is 6h~8h; and / or, the washing is performed using anhydrous ethanol.

[0038] To achieve the second objective of the invention, the technical solution adopted by the present invention is as follows:

[0039] This invention provides a high adsorption capacity and conductivity MWW molecular sieve composite material, which is prepared by the above-described method for preparing a high adsorption capacity and conductivity MWW molecular sieve composite material.

[0040] To achieve the third objective of the invention, the technical solution adopted by the present invention is as follows:

[0041] An electrochemical sensor is provided, which is made of the MWW molecular sieve composite material with high adsorption capacity and conductivity.

[0042] To achieve the fourth objective of the invention, the technical solution adopted by the present invention is as follows:

[0043] This invention provides a method for preparing an electrochemical sensor, comprising the following steps:

[0044] S1. Disperse the MWW molecular sieve composite material with high adsorption capacity and conductivity as described in claim 5 in a solvent to obtain a molecular sieve composite material suspension;

[0045] S2. After the molecular sieve composite material suspension is drop-coated onto the screen-printed electrode and dried to evaporate the solvent, the electrochemical sensor is obtained.

[0046] Furthermore, in step S1, the concentration of the molecular sieve composite material suspension is 5 mg / mL to 15 mg / mL; and / or, the solvent is a chitosan solution; the concentration of the chitosan solution is 0.3 wt% to 0.7 wt%; and / or, the dispersion method is ultrasonic treatment for 20 min to 40 min.

[0047] Among them, chitosan solution is used as the solvent for dispersing MWW molecular sieve composite material. Based on the fact that chitosan solution is a strong and biocompatible "glue", it can firmly fix the active substances in MWW molecular sieve composite material onto the screen-printed electrode surface. Chitosan replaces the traditional toxic and non-degradable adhesives. The modified electrode has the advantages of being environmentally friendly, non-toxic, low cost, and easy to degrade, and can form a uniform, stable, and strongly adhesive film on the electrode surface.

[0048] Furthermore, in step S2, the molecular sieve composite material suspension is drop-coated onto the screen-printed electrode, and the thickness of the molecular sieve composite material layer formed after drying is 1 mm to 1.5 mm; and / or, the drying method is natural air drying at room temperature.

[0049] This invention enables the fabricated electrochemical sensor to possess superior detection performance by controlling the concentration of the molecular sieve composite material suspension and the thickness of the material layer formed by its drop-coating onto a screen-printed electrode. Specifically, the concentration of the molecular sieve composite material suspension affects its dispersion on the electrode. If the concentration of the suspension is too high or the amount of suspension used for drop-coating is excessive, the adsorption sites on the electrode become saturated, limiting its catalytic ability for chlorogenic acid and leading to a decrease in the detection sensitivity of the electrochemical sensor. Conversely, if the concentration of the suspension is too low or the amount of suspension used for drop-coating is insufficient, there will be fewer adsorption sites on the electrode, resulting in a weaker reactivity with chlorogenic acid, thus reducing the detection sensitivity and electrochemical response of the electrochemical sensor.

[0050] To achieve the fifth objective of the invention, the technical solution adopted by the present invention is as follows:

[0051] This invention provides an application of an electrochemical sensor, specifically the application of the electrochemical sensor described above or the electrochemical sensor prepared by the method described above in detecting chlorogenic acid content.

[0052] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0053] (1) A method for preparing a high-adsorption-capacity and high-conductivity MWW molecular sieve composite material according to the present invention involves using cyclohexylamine as a template agent, along with sodium aluminate, sodium hydroxide, silica sol, and water to prepare an aluminosilicate gel. Tin dioxide is then introduced into the aluminosilicate gel using an in-situ synthesis method. Carbon nanotubes are then composited with a sheet-like SnO2-MWW molecular sieve to obtain a sheet-like MWW molecular sieve-loaded tin dioxide and carbon nanotube composite material (CNTs@SnO2-MWW composite material), which is a high-adsorption-capacity and high-conductivity MWW molecular sieve composite material. This MWW molecular sieve composite material has the characteristics of large specific surface area, high adsorption capacity, and excellent conductivity. The total specific surface area of ​​the MWW molecular sieve composite material prepared by the present invention is greater than 400 m². 2 / g, total pore volume greater than 0.6m 3 / g.

[0054] (2) The preparation method of the MWW molecular sieve composite material with high adsorption capacity and conductivity of the present invention can promote the participation of more active sites in the reaction, allowing more target molecules to be rapidly adsorbed in a short time, thereby improving the catalytic rate of the reaction. In particular, by doping semiconductor tin dioxide into the sheet-like MWW molecular sieve, the SnO2-MWW molecular sieve has good conductivity, which increases the electrocatalytic performance of the working electrode of the molecular sieve in electrochemical sensors. In addition, by compositing carbon nanotubes with sheet-like SnO2-MWW molecular sieve, on the one hand, the carbon nanotubes, as a support, can effectively prevent the aggregation of sheet-like SnO2-MWW molecular sieve particles to expose more active sites; on the other hand, the extremely high conductivity of carbon nanotubes provides a continuous electronic conduction path for sheet-like SnO2-MWW molecular sieve, thereby greatly reducing the overall resistance of the composite material, enabling the MWW molecular sieve composite material to exhibit excellent performance when applied to electrochemical sensors.

[0055] (3) The MWW molecular sieve composite material of the present invention with high adsorption capacity and conductivity has the advantages of large specific surface area, high total pore volume and excellent conductivity. Since tin dioxide can not only improve the conductivity of the sheet MWW molecular sieve itself, but also optimize charge transport at the interface, and in addition, with the extremely high conductivity of carbon nanotubes, it provides a continuous electronic conduction path for the sheet SnO2-MWW molecular sieve, thereby enabling the composite material to exhibit excellent electrochemical performance in electrochemical sensors. In addition, the sheet SnO2-MWW molecular sieve has regular channels and short diffusion paths, which can "shape select" the reactants and shorten the reaction time during application. The synergistic effect of the active sites on the surface of the sheet SnO2-MWW molecular sieve and the carbon nanotubes can greatly enhance the electrocatalytic performance of the composite material.

[0056] (4) The present invention provides a high adsorption capacity and conductivity MWW molecular sieve composite material, which is a composite of carbon nanotubes and sheet SnO2-MWW molecular sieve. Through the combined action of chemical bonding and physical adsorption, the conductivity and three-dimensional network structure of carbon nanotubes are combined with the large specific surface area, high active sites, high diffusivity and stability of sheet SnO2-MWW molecular sieve, thus making the MWW molecular sieve composite material have good application prospects in the fields of catalysis and sensing.

[0057] (5) An electrochemical sensor of the present invention is prepared by drop-coating a suspension formed by the MWW molecular sieve composite material prepared by the present invention onto a screen-printed electrode. Since the MWW molecular sieve composite material has the advantages of good hydrothermal stability, unique pore structure, large specific surface area, high total pore volume, good diffusivity and excellent conductivity, the electrochemical sensor prepared has the advantages of low detection cost, high detection accuracy, good detection sensitivity and wide detection range. In addition, the electrochemical sensor also has the advantages of simple preparation method, simple structure, low preparation cost and convenient operation.

[0058] (6) Application of an electrochemical sensor of the present invention in the detection of chlorogenic acid content. The electrochemical sensor has the advantage of a wide detection linear range, which is 1~1500 μmol / L, and a low detection limit, which can reach 0.02 μmol / L. It also has excellent sensing characteristics such as detection sensitivity, stability, reproducibility and anti-interference. It can realize the accurate determination of chlorogenic acid content in food and reduce detection costs, and has a good application prospect. Attached Figure Description

[0059] Figure 1 The images show the XRD patterns of the sheet-like SnO2-MWW molecular sieve, CNTs, CNTs@SnO2-MWW composite material of Example 1 and the sheet-like MWW molecular sieve of Comparative Example 3.

[0060] Figure 2 SEM images of the sheet-like MWW molecular sieve of Comparative Example 3, and the sheet-like SnO2-MWW molecular sieve, CNTs, and CNTs@SnO2-MWW composite material of Example 1.

[0061] Figure 3 TEM images of the sheet-like MWW molecular sieve of Comparative Example 3, and the sheet-like SnO2-MWW molecular sieve, CNTs, and CNTs@SnO2-MWW composite material of Example 1.

[0062] Figure 4 The image shows the energy dispersive X-ray spectrum of the CNTs@SnO2-MWW composite material prepared in Example 1 of this invention.

[0063] Figure 5 The X-ray photoelectron spectroscopy (XPS) spectra of the sheet-like MWW molecular sieve of Comparative Example 3, and the sheet-like SnO2-MWW molecular sieve and CNTs@SnO2-MWW composite material of Example 1 are shown.

[0064] Figure 6 The nitrogen adsorption-desorption isotherms and BJH pore size distribution analysis diagrams are for the sheet-like MWW molecular sieve of Comparative Example 3, and the sheet-like SnO2-MWW molecular sieve and CNTs@SnO2-MWW composite material of Example 1.

[0065] Figure 7 The time-coulomb curves are used to detect the electrocatalytic activity of the sheet-like MWW molecular sieve of Comparative Example 3, and the sheet-like SnO2-MWW molecular sieve and CNTs@SnO2-MWW composite material of Example 1.

[0066] Figure 8 The cyclic voltammetry curves of the electrochemical sensors prepared in Example 7 and Comparative Examples 1-2 of this invention were measured in 0.1 mol / L PBS solution (pH=7) containing 0.005 mol / L chlorogenic acid.

[0067] Figure 9 This is a cyclic voltammetry curve of the electrochemical sensor prepared in Example 7 of the present invention in 0.1 mol / L PBS solutions containing 0.005 mol / L chlorogenic acid at different pH values.

[0068] Figure 10 This is a cyclic voltammetry curve of the electrochemical sensor prepared in Example 7 of the present invention at different scan rates in a 0.1 mol / L PBS (pH=7) solution containing 0.005 mol / L chlorogenic acid.

[0069] Figure 11 Cyclic voltammetry curves of the electrochemical sensor prepared in Example 7 in 0.1 mol / L PBS solution containing chlorogenic acid (pH=7) and 0.1 mol / L PBS solution without chlorogenic acid (pH=7).

[0070] Figure 12 The graph shows the anti-interference test results of the electrochemical sensor prepared in Example 7 of this invention for detecting chlorogenic acid.

[0071] Figure 13 The graph shows the reproducibility test results of the electrochemical sensor obtained in Example 7 of this invention for detecting chlorogenic acid current.

[0072] Figure 14 The graph shows the stability test results of the electrochemical sensor prepared in Example 7 of this invention for detecting chlorogenic acid.

[0073] Figure 15The graph shows the differential pulse voltammetry curves (a) and the linear relationship between the current value of the differential pulse voltammetry curve and the corresponding concentration (b) for detecting different concentrations of chlorogenic acid using the electrochemical sensor prepared in Example 7. Figure 16 The DPV electrochemical response curve (a) and CV electrochemical response curve (b) of the electrochemical sensors prepared in Example 7, Comparative Example 4 and Comparative Example 5 as working electrodes are shown in Figure 5. Detailed Implementation

[0074] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0075] In this embodiment of the invention, a method for preparing an MWW molecular sieve composite material with high adsorption capacity and conductivity includes the following steps:

[0076] S1. Preparation of aluminosilicate gel: Cyclohexylamine, sodium aluminate, sodium hydroxide, and silica sol are mixed in water to obtain aluminosilicate gel;

[0077] S2. Preparation of sheet-like SnO2-MWW molecular sieve: The aluminosilicate gel is mixed with tin dioxide in situ, then heated and reacted. After filtration, washing, drying and calcination, sheet-like MWW molecular sieve loaded with tin dioxide material is obtained, which is the sheet-like SnO2-MWW molecular sieve.

[0078] S3, Loaded carbon nanotubes: The sheet-like SnO2-MWW molecular sieve and carbon nanotubes are added to a chitosan solution, stirred and reacted, then centrifuged, the precipitate is collected, washed and dried to obtain CNTs@SnO2-MWW composite material, that is, the MWW molecular sieve composite material with high adsorption capacity and conductivity is obtained.

[0079] In some embodiments, in step S1, the molar ratio of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol, and water is (2~20):(0.1~5):(0.1~5):(5~50):(100~400); and / or, the mixing method is magnetic stirring, the temperature of the magnetic stirring is 20℃~40℃, and the time of the magnetic stirring is 2h~4h.

[0080] In some embodiments, in step S2, the molar ratio of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol, water, and tin dioxide is (2~20):(0.1~5):(0.1~5):(5~50):(100~400):(0.1~5); and / or, the in-situ mixing method is magnetic stirring, the magnetic stirring temperature is 20℃~40℃, and the magnetic stirring time is 2h~4h; and / or, the heating reaction temperature is 140℃~180℃, and the heating reaction time is 24h~54h; and / or, the drying temperature is 100℃~150℃, and the drying time is 2h~6h; and / or, the calcination temperature is 500℃~700℃, and the calcination time is 3h~5h; and / or, the washing is performed using deionized water.

[0081] In some embodiments, in step S3, the mass ratio of the sheet-like SnO2-MWW molecular sieve to the carbon nanotube is (0.5~2):(0.1~3); and / or, the mass ratio of the chitosan solution to the sheet-like SnO2-MWW molecular sieve is 1:(3~7); and / or, the concentration of the chitosan solution is 0.02wt%~0.3wt%; and / or, the temperature of the stirring reaction is 25℃~40℃, and the stirring reaction time is 2h~4h; and / or, the drying temperature is 80℃~100℃, and the drying time is 6h~8h; and / or, the washing is performed with anhydrous ethanol.

[0082] In this embodiment of the invention, a high adsorption capacity and conductivity MWW molecular sieve composite material is prepared by the above-described preparation method of a high adsorption capacity and conductivity MWW molecular sieve composite material.

[0083] In this embodiment of the invention, an electrochemical sensor is made from the MWW molecular sieve composite material with high adsorption capacity and conductivity described above.

[0084] In this embodiment of the invention, a method for preparing an electrochemical sensor includes the following steps:

[0085] S1. Disperse the MWW molecular sieve composite material with high adsorption capacity and conductivity as described in claim 5 in a solvent to obtain a molecular sieve composite material suspension;

[0086] S2. After the molecular sieve composite material suspension is drop-coated onto the screen-printed electrode and dried to evaporate the solvent, the electrochemical sensor is obtained.

[0087] In some embodiments, in step S1, the concentration of the molecular sieve composite material suspension is 5 mg / mL to 15 mg / mL; and / or, the solvent is a chitosan solution; the concentration of the chitosan solution is 0.3 wt% to 0.7 wt%; and / or, the dispersion method is ultrasonic treatment for 20 min to 40 min.

[0088] In some embodiments, in step S2, the molecular sieve composite material suspension is drop-coated onto a screen-printed electrode, and the thickness of the molecular sieve composite material layer formed after drying is 1 mm to 1.5 mm; and / or, the drying method is natural air drying at room temperature.

[0089] In this embodiment of the invention, an electrochemical sensor is applied, specifically the electrochemical sensor described above or prepared by the method described above, in the detection of chlorogenic acid content.

[0090] The following description is based on specific embodiments. Example 1

[0091] A method for preparing a high-adsorption-capacity and high-conductivity MWW molecular sieve composite material includes the following steps:

[0092] S1. Preparation of aluminosilicate gel: Cyclohexylamine, sodium aluminate, sodium hydroxide and silica sol are mixed in water at 40°C with magnetic stirring for 2 hours to obtain aluminosilicate gel; In this embodiment, the molar ratio of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol and water is 9:1:1:20:240.

[0093] S2. Preparation of sheet-like SnO2-MWW molecular sieve: Aluminosilicate gel and tin dioxide were mixed in situ and magnetically stirred at 40°C for 2 hours to obtain aluminosilicate gel containing tin dioxide. Then, the mixture was heated at 160°C for 36 hours, filtered, washed with deionized water, dried at 120°C for 4 hours, and calcined at 600°C for 4 hours to obtain sheet-like MWW molecular sieve loaded with tin dioxide, which is the sheet-like SnO2-MWW molecular sieve. In this embodiment, the molar ratio of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol, water, and tin dioxide is 9:1:1:20:240:1.

[0094] S3. Loaded Carbon Nanotubes: Sheet SnO2-MWW molecular sieves and carbon nanotubes were added to a 0.1 wt% chitosan solution and stirred at 40°C for 2 h. Then, the mixture was centrifuged, the precipitate was collected, washed with anhydrous ethanol, and dried at 90°C for 7 h to obtain CNTs@SnO2-MWW composite material, which is a high-adsorption-capacity and high-conductivity MWW molecular sieve composite material. In this embodiment, the mass ratio of sheet SnO2-MWW molecular sieves to carbon nanotubes was 1:1; the mass ratio of chitosan solution to sheet SnO2-MWW molecular sieves was 1:5. Example 2

[0095] A method for preparing a high-adsorption-capacity and high-conductivity MWW molecular sieve composite material includes the following steps:

[0096] S1. Preparation of aluminosilicate gel: Cyclohexylamine, sodium aluminate, sodium hydroxide and silica sol were mixed in water at 35°C with magnetic stirring for 2.5 h to obtain aluminosilicate gel; In this embodiment, the molar ratio of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol and water was 7:1:1:20:240.

[0097] S2. Preparation of sheet-like SnO2-MWW molecular sieve: The aluminosilicate gel and tin dioxide were mixed in situ and magnetically stirred at 35°C for 2.5 h to obtain an aluminosilicate gel containing tin dioxide. Then, the mixture was heated at 150°C for 48 h, filtered, washed with deionized water, dried at 100°C for 6 h, and calcined at 500°C for 5 h to obtain a sheet-like MWW molecular sieve loaded with tin dioxide, which is the sheet-like SnO2-MWW molecular sieve. In this embodiment, the molar ratio of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol, water, and tin dioxide is 7:1:1:20:240:0.2.

[0098] S3. Loaded Carbon Nanotubes: Sheet SnO2-MWW molecular sieves and carbon nanotubes were added to a 0.05wt% chitosan solution and stirred at 35°C for 2.5h. Then, the mixture was centrifuged, the precipitate was collected, washed with anhydrous ethanol, and dried at 80°C for 8h to obtain CNTs@SnO2-MWW composite material, which is a high-adsorption-capacity and high-conductivity MWW molecular sieve composite material. In this embodiment, the mass ratio of sheet SnO2-MWW molecular sieves to carbon nanotubes was 1:2; the mass ratio of chitosan solution to sheet SnO2-MWW molecular sieves was 1:3. Example 3

[0099] A method for preparing a high-adsorption-capacity and high-conductivity MWW molecular sieve composite material includes the following steps:

[0100] S1. Preparation of aluminosilicate gel: Cyclohexylamine, sodium aluminate, sodium hydroxide and silica sol are mixed in water at 30°C with magnetic stirring for 3 hours to obtain aluminosilicate gel; In this embodiment, the molar ratio of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol and water is 9:3:1:20:240.

[0101] S2. Preparation of sheet-like SnO2-MWW molecular sieve: The aluminosilicate gel and tin dioxide are mixed in situ and magnetically stirred at 30°C for 3 hours to obtain an aluminosilicate gel containing tin dioxide. Then, the mixture is heated at 180°C for 24 hours, filtered, washed with deionized water, dried at 150°C for 2 hours, and calcined at 700°C for 3 hours to obtain a sheet-like MWW molecular sieve loaded with tin dioxide, which is the sheet-like SnO2-MWW molecular sieve. In this embodiment, the molar ratio of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol, water, and tin dioxide is 9:3:1:20:240:2.

[0102] S3. Loaded carbon nanotubes: Sheet SnO2-MWW molecular sieves and carbon nanotubes were added to a 0.15wt% chitosan solution and stirred at 30°C for 3 hours. Then, the mixture was centrifuged, the precipitate was collected, washed with anhydrous ethanol, and dried at 100°C for 6 hours to obtain CNTs@SnO2-MWW composite material, which is a high-adsorption-capacity and high-conductivity MWW molecular sieve composite material. In this embodiment, the mass ratio of sheet SnO2-MWW molecular sieves to carbon nanotubes was 1:3; the mass ratio of chitosan solution to sheet SnO2-MWW molecular sieves was 1:7. Example 4

[0103] A method for preparing a high-adsorption-capacity and high-conductivity MWW molecular sieve composite material includes the following steps:

[0104] S1. Preparation of aluminosilicate gel: Cyclohexylamine, sodium aluminate, sodium hydroxide and silica sol were mixed in water at 25°C with magnetic stirring for 3.5 h to obtain aluminosilicate gel; In this embodiment, the molar ratio of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol and water was 2:0.1:0.1:5:100.

[0105] S2. Preparation of sheet-like SnO2-MWW molecular sieve: The aluminosilicate gel and tin dioxide are mixed in situ and magnetically stirred at 25°C for 3.5 h to obtain an aluminosilicate gel containing tin dioxide. Then, the mixture is heated at 140°C for 54 h, filtered, washed with deionized water, dried at 110°C for 5 h, and calcined at 550°C for 4.5 h to obtain a sheet-like MWW molecular sieve loaded with tin dioxide, which is the sheet-like SnO2-MWW molecular sieve. In this embodiment, the molar ratio of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol, water, and tin dioxide is 2:0.1:0.1:5:100:0.1.

[0106] S3. Loaded Carbon Nanotubes: Sheet SnO2-MWW molecular sieves and carbon nanotubes were added to a 0.02wt% chitosan solution and stirred at 28°C for 3.5h. Then, the mixture was centrifuged, the precipitate was collected, washed with anhydrous ethanol, and dried at 85°C for 7.5h to obtain CNTs@SnO2-MWW composite material, which is a high-adsorption-capacity and high-conductivity MWW molecular sieve composite material. In this embodiment, the mass ratio of sheet SnO2-MWW molecular sieves to carbon nanotubes was 2:3; the mass ratio of chitosan solution to sheet SnO2-MWW molecular sieves was 1:4. Example 5

[0107] A method for preparing a high-adsorption-capacity and high-conductivity MWW molecular sieve composite material includes the following steps:

[0108] S1. Preparation of aluminosilicate gel: Cyclohexylamine, sodium aluminate, sodium hydroxide and silica sol are mixed in water at 20°C with magnetic stirring for 4 hours to obtain aluminosilicate gel; In this embodiment, the molar ratio of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol and water is 20:5:5:50:400.

[0109] S2. Preparation of sheet-like SnO2-MWW molecular sieve: The aluminosilicate gel and tin dioxide are mixed in situ and magnetically stirred at 20°C for 4 hours to obtain an aluminosilicate gel containing tin dioxide. Then, the mixture is heated at 170°C for 30 hours, filtered, washed with deionized water, dried at 140°C for 3 hours, and calcined at 650°C for 3.5 hours to obtain a sheet-like MWW molecular sieve loaded with tin dioxide, which is the sheet-like SnO2-MWW molecular sieve. In this embodiment, the molar ratio of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol, water, and tin dioxide is 20:5:5:50:400:5.

[0110] S3. Loaded Carbon Nanotubes: Sheet SnO2-MWW molecular sieves and carbon nanotubes were added to a 0.3 wt% chitosan solution and stirred at 25 °C for 4 h. Then, the mixture was centrifuged, the precipitate was collected, washed with anhydrous ethanol, and dried at 95 °C for 6.5 h to obtain CNTs@SnO2-MWW composite material, which is a high-adsorption-capacity and high-conductivity MWW molecular sieve composite material. In this embodiment, the mass ratio of sheet SnO2-MWW molecular sieves to carbon nanotubes was 0.5:0.1; the mass ratio of chitosan solution to sheet SnO2-MWW molecular sieves was 1:6. Example 6

[0111] An electrochemical sensor is prepared from a high-adsorption-capacity and high-conductivity MWW molecular sieve composite material obtained in Examples 1 to 5. Example 7

[0112] A method for preparing an electrochemical sensor includes the following steps:

[0113] S1. The MWW molecular sieve composite material with high adsorption capacity and conductivity of Example 1 is dispersed in a 0.5 wt% chitosan solution and ultrasonically treated for 30 min to obtain a molecular sieve composite material suspension; in this example, the concentration of the molecular sieve composite material suspension is 10 mg / mL.

[0114] S2. After drop-coating the molecular sieve composite material suspension onto the screen-printed electrode, allow it to air dry at room temperature to evaporate the chitosan solution, thus obtaining the electrochemical sensor. In this embodiment, the thickness of the molecular sieve composite material layer is 1.25 mm.

[0115] The electrochemical sensor prepared in this embodiment was tested by cyclic voltammetry in a 0.1 mol / L PBS solution (pH=7) containing 0.005 mol / L chlorogenic acid, and the detection current was 19.85 μA. Therefore, this demonstrates that the electrochemical sensor of the present invention has electrochemical responsiveness to the detection of chlorogenic acid, and the optimal detection conditions can be determined by the current values ​​detected under different conditions. Example 8

[0116] A method for preparing an electrochemical sensor includes the following steps:

[0117] S1. The MWW molecular sieve composite material with high adsorption capacity and conductivity of Example 2 was dispersed in a 0.3 wt% chitosan solution and ultrasonically treated for 40 min to obtain a molecular sieve composite material suspension; in this example, the concentration of the molecular sieve composite material suspension was 5 mg / mL.

[0118] S2. After drop-coating the molecular sieve composite material suspension onto the screen-printed electrode, allow it to air dry at room temperature to evaporate the chitosan solution, thus obtaining the electrochemical sensor. In this embodiment, the thickness of the molecular sieve composite material layer is 1 mm.

[0119] In this embodiment, the electrochemical sensor was tested by cyclic voltammetry in a 0.1 mol / L PBS solution (pH=7) containing 0.005 mol / L chlorogenic acid, and the detection current was 16.97 μA. Example 9

[0120] A method for preparing an electrochemical sensor includes the following steps:

[0121] S1. The MWW molecular sieve composite material with high adsorption capacity and conductivity of Example 3 was dispersed in a 0.7wt% chitosan solution and ultrasonically treated for 20 min to obtain a molecular sieve composite material suspension; in this example, the concentration of the molecular sieve composite material suspension was 15 mg / mL.

[0122] S2. After drop-coating the molecular sieve composite material suspension onto the screen-printed electrode, allow it to air dry at room temperature to evaporate the chitosan solution, thus obtaining the electrochemical sensor. In this embodiment, the thickness of the molecular sieve composite material layer is 1.5 mm.

[0123] In this embodiment, the electrochemical sensor was tested by cyclic voltammetry in a 0.1 mol / L PBS solution (pH=7) containing 0.005 mol / L chlorogenic acid, and the detection current was 15.42 μA. Example 10

[0124] Application of an electrochemical sensor, specifically the application of any one of the electrochemical sensors in Examples 6 to 9 in the detection of chlorogenic acid content.

[0125] Comparative Example 1

[0126] A method for preparing an electrochemical sensor is disclosed. The difference between this comparative example and Example 7 is that the thickness of the molecular sieve composite material layer in this example is 0.75 mm. The remaining preparation methods in this comparative example are the same as in Example 7.

[0127] Comparative Example 2

[0128] A method for preparing an electrochemical sensor is disclosed. The difference between this comparative example and Example 7 is that the thickness of the molecular sieve composite material layer in this example is 1.75 mm. The remaining preparation methods in this comparative example are the same as in Example 7.

[0129] Comparative Example 3

[0130] A method for preparing a layered MWW molecular sieve includes the following steps:

[0131] Cyclohexylamine, sodium aluminate, sodium hydroxide, and silica sol were mixed in water at 40°C with magnetic stirring for 2 hours to obtain aluminosilicate gel. The gel was then heated at 160°C for 36 hours, filtered, washed with deionized water, dried at 120°C for 4 hours, and calcined at 600°C for 4 hours to obtain sheet-like MWW molecular sieve.

[0132] Comparative Example 4

[0133] A method for preparing an electrochemical sensor is disclosed. The difference between this comparative example and Example 7 is that the sheet-like SnO2-MWW molecular sieve obtained in step 2 of Example 1 is used instead of the MWW molecular sieve composite material with high adsorption capacity and conductivity of Example 1 (i.e., the MWW molecular sieve is only loaded with tin dioxide). The remaining preparation methods of this comparative example are the same as those of Example 7.

[0134] Comparative Example 5

[0135] A method for preparing an MWW molecular sieve composite material is disclosed. The difference between this comparative example and Example 1 is that step S2 is omitted, and the sheet-like MWW molecular sieve obtained in Comparative Example 3 replaces the sheet-like SnO2-MWW molecular sieve in step S3 of Example 1 (i.e., the MWW molecular sieve is only loaded with carbon nanotubes). The remaining preparation methods of this comparative example are the same as those in Example 1.

[0136] A method for preparing an electrochemical sensor is disclosed. The difference between this comparative example and Example 7 is that the MWW molecular sieve composite material prepared in this comparative example 5 is used instead of the MWW molecular sieve composite material with high adsorption capacity and conductivity in Example 1. The remaining preparation methods in this comparative example are the same as in Example 7.

[0137] Structural morphology characterization

[0138] (a) X-ray diffraction analysis

[0139] The sheet-like SnO2-MWW molecular sieve (SnO2-MWW), carbon nanotubes (CNTs), and MWW molecular sieve composite material (CNTs@SnO2-MWW) of Example 1, and the sheet-like MWW molecular sieve (MWW) of Comparative Example 3 were subjected to X-ray diffraction analysis, and the analysis results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the MWW molecular sieve composite material of the present invention was successfully synthesized. Obvious SnO2 diffraction peaks at 2θ = 26.61° and 33.89° can be observed in the SnO2-MWW spectrum, indicating that SnO2 was successfully introduced. Furthermore, characteristic peaks of SnO2 were clearly observed in the CNTs@SnO2-MWW spectrum, while no CNT peaks were observed. This may be because the strong diffraction peaks of the MWW molecular sieve masked the weak diffraction signals of the CNTs.

[0140] (II) Morphological characterization by scanning electron microscopy

[0141] The layered MWW molecular sieve of Comparative Example 3, the layered SnO2-MWW molecular sieve of Example 1, CNTs, and CNTs@SnO2-MWW composite materials were characterized by scanning electron microscopy (SEM). Figure 2 As shown in the figure. The SEM images of the layered MWW molecular sieve, layered SnO2-MWW molecular sieve, CNTs, and CNTs@SnO2-MWW composite materials are shown in the figure. Figure 2 As shown in Figures a to d.

[0142] Depend on Figure 2As can be seen, the sheet-like MWW molecular sieve prepared in Comparative Example 3 exhibits a typical two-dimensional sheet-like morphology, resembling a leaf. The shape and size of the sheet-like SnO2-MWW molecular sieve are basically consistent with those of the sheet-like MWW molecular sieve, indicating that the in-situ synthesis of SnO2 did not change the appearance of the material. In addition, carbon nanotubes exhibit a slender, entangled fibrous structure, interwoven on the surface and in the gaps of the sheet-like SnO2-MWW molecular sieve, forming a dense CNTs@SnO2-MWW heterostructure.

[0143] (III) Morphological characterization by transmission electron microscopy

[0144] The layered MWW molecular sieve of Comparative Example 3, the layered SnO2-MWW molecular sieve of Example 1, CNTs, and CNTs@SnO2-MWW composite materials were characterized by transmission electron microscopy (TEM). Figure 3 As shown in the figure. The diagrams of layered MWW molecular sieve, layered SnO2-MWW molecular sieve, CNTs, and CNTs@SnO2-MWW composite materials are respectively shown in the figure. Figure 3 As shown in Figures a to d.

[0145] Depend on Figure 3 It can be seen that the layered MWW molecular sieve and the layered SnO2-MWW molecular sieve exhibit a thin layered morphology with little variation. Furthermore, Figure 3 The carbon nanotubes in (c) exhibit a slender, strip-like structure. Figure 3 As shown in (d), CNTs and SnO2-MWW are intertwined, which is consistent with the results of SEM, proving that CNTs@SnO2-MWW was successfully synthesized.

[0146] (iv) Energy-dispersive X-ray spectroscopy analysis

[0147] The CNTs@SnO2-MWW composite material prepared in Example 1 was subjected to energy-dispersive X-ray spectroscopy analysis, such as... Figure 4 As shown. By Figure 4 It can be seen that the CNTs@SnO2-MWW composite material prepared by the present invention is mainly composed of elements such as C, Sn, Si and Al, and the elements do not exhibit agglomeration and have high dispersion.

[0148] (V) X-ray photoelectron spectroscopy full spectrum analysis

[0149] The layered MWW molecular sieve of Comparative Example 3, and the layered SnO2-MWW molecular sieve and CNTs@SnO2-MWW composite material of Example 1 were subjected to full-spectrum X-ray photoelectron spectroscopy analysis, such as... Figure 5 As shown. Among them, Figure 5 (a) is the full scan spectrum. Figure 5 (b) is the high-resolution spectrum of Sn 3d. Figure 5 (c) is the high-resolution spectrum of C 1s.

[0150] Depend on Figure 5 (a) As can be seen, the sheet-like SnO2-MWW molecular sieve has an additional Sn 3d peak (498 eV) compared to the sheet-like MWW molecular sieve, indicating that the Sn species was successfully introduced. Simultaneously, Sn 3d (498 eV) and C1s (284 eV) were observed in CNTs@SnO2-MWW, indicating that CNTs successfully recombine with SnO2-MWW. Figure 5 (b) It can be seen that both SnO2-MWW and CNTs@SnO2-MWW contain Sn 3d 3 / 2 (498.23 eV and 498.68 eV) and Sn 3d 5 / 2 (486.48 eV and 486.58 eV), but the introduction of CNTs enhanced the binding energy, possibly because a strong interaction occurred between SnO2-MWW and CNTs, leading to a decrease in the electron cloud density around the Sn atom and thus an increase in its binding energy. Furthermore, due to... Figure 5 (c) It can be seen that the binding energy of C 1s in the CNTs@SnO2-MWW composite material, 284.02 eV, belongs to sp. 2 Carbon (CC) is the characteristic peak of the main graphite lattice of CNTs.

[0151] (vi) Analysis of nitrogen adsorption-desorption isotherms and BJH pore size distribution

[0152] The layered MWW molecular sieve of Comparative Example 3, and the layered SnO2-MWW molecular sieve and CNTs@SnO2-MWW composite material of Example 1 were subjected to nitrogen adsorption-desorption isotherm and BJH pore size distribution analysis, respectively. Figure 6 As shown. Figure 6 In the figure, curve a represents the sheet-like MWW molecular sieve, curve b represents the sheet-like SnO2-MWW molecular sieve, and curve c represents the CNTs@SnO2-MWW composite material.

[0153] Depend on Figure 6 (a) shows that the nitrogen adsorption-desorption isotherms of the layered MWW molecular sieve, layered SnO2-MWW molecular sieve, and CNTs@SnO2-MWW composite material exhibit a hysteresis loop when P / P0>0.5, indicating that all three materials produce mesoporous structures. Furthermore, from... Figure 6(b) It can be observed that the layered MWW molecular sieve, the layered SnO2-MWW molecular sieve, and the CNTs@SnO2-MWW composite material all exhibit a narrow peak around 3.5 nm, indicating that the three materials have uniform mesopore sizes. Furthermore, based on the test results, the pore structure parameters were summarized. The total specific surface area of ​​the layered MWW molecular sieve reaches 435.8715 m² / g, and the total pore volume is 0.6487 m³ / g. The high specific surface area and large adsorption capacity give this molecular sieve highly exposed active sites, which is beneficial for redox reactions.

[0154] Molecular sieve performance testing

[0155] (a) Specific surface area and pore volume detection of molecular sieves

[0156] The total specific surface area, mesopore area, micropore area, total pore volume, micropore volume, and mesopore volume of the sheet-like MWW molecular sieve of Comparative Example 3, and the sheet-like SnO2-MWW molecular sieve and CNTs@SnO2-MWW composite material of Example 1 were tested respectively. The test results are shown in Table 1.

[0157] Table 1. Proportions of layered MWW molecular sieves, layered SnO2-MWW molecular sieves, and CNTs@SnO2-MWW composite materials

[0158] Table of Area and Pore Volume Test Results

[0159]

[0160] The total specific surface area was calculated using the Brunauer–Emmett–Teller (BET) method. The total pore volume was determined by adsorption volume measurement at P / P0 = 0.99. The micropore volume was determined by the t-plot method. Mesopore volume = Total pore volume - Micropore volume.

[0161] As shown in Table 1, the specific surface area of ​​the sheet-like MWW molecular sieve is not much different from that of the sheet-like SnO2-MWW molecular sieve, but the total pore volume of the sheet-like SnO2-MWW molecular sieve is lower. This may be because the introduction of SnO2 blocked some of the pores of the molecular sieve. The specific surface area of ​​the CNTs@SnO2-MWW composite material is slightly lower than that of the sheet-like MWW molecular sieve. This slight decrease proves that a close interfacial interaction occurred between the sheet-like SnO2-MWW molecular sieve and the carbon nanotubes. By sacrificing a little specific surface area, the conductivity is improved (based on the conductive pathway provided by carbon nanotubes and SnO2) and the sensing performance is significantly enhanced (based on the interaction between materials and the electronic effect at the interface).

[0162] (II) Detection of the electrocatalytic activity of molecular sieves

[0163] The electrocatalytic activity of the layered MWW molecular sieve of Comparative Example 3, and the layered SnO2-MWW molecular sieve and CNTs@SnO2-MWW composite material of Example 1 were detected, and the time-coulomb curves and the relationship between the coulomb value Q and the square root of t were obtained, as shown below. Figure 7 As shown. Figure 7 In the figure, curve a represents the sheet-like MWW molecular sieve, curve b represents the sheet-like SnO2-MWW molecular sieve, and curve c represents the CNTs@SnO2-MWW composite material.

[0164] Depend on Figure 7 (a) It can be seen that the electrode modified with CNTs@SnO2-MWW composite material exhibits the largest coulomb value, indicating its superior electron transfer capability and electrocatalytic activity. From Figure 7 (b) It can be seen that, according to the Cottrell equation, the electroactive surface area of ​​the electrode is calculated as shown in equations (1) and (2).

[0165]

[0166]

[0167] Where I(t) is the current at time t, A is the electroactive area, and D is the diffusion coefficient (D = 7.6 × 10⁻⁶). -6 cm 2 / s), n is the number of electrons transferred, F is the Faraday constant (96485 C / mol), and C is the reactant concentration (mol / cm³). 3 The electroactive areas of the three materials were calculated to be, in descending order, CNTs@SnO2-MWW composite material (0.3903 cm²). 2 )>Laminated SnO2-MWW molecular sieve (0.1942 cm 2 MWW molecular sieve (0.1002 cm⁻¹) 2 The results showed that the CNTs@SnO2-MWW composite material exhibited the best electrochemical response and electrocatalytic ability during the electrocatalytic process, and thus could be well applied to electrochemical sensors.

[0168] (III) Detection of the conductivity of molecular sieves

[0169] The conductivity of the layered MWW molecular sieve of Comparative Example 3, and the layered SnO2-MWW molecular sieve and CNTs@SnO2-MWW composite material of Example 1 were directly measured using the four-probe method to quantitatively evaluate the electrical conductivity of the three materials. Among them, the layered MWW molecular sieve exhibited the lowest conductivity (1.17 × 10⁻⁶). -8The conductivity of the layered SnO2-MWW molecular sieve is significantly increased to 7.38 × 10⁻⁶ S / cm, while that of the layered SnO2-MWW molecular sieve is significantly increased to 7.38 × 10⁻⁶ S / cm. -4 The conductivity of the CNTs@SnO2-MWW composite material is as high as 0.16 S / cm, which far exceeds that of the sheet-like MWW molecular sieve and the sheet-like SnO2-MWW molecular sieve. This shows that the composite material obtained by introducing SnO2 and carbon nanotubes in this invention greatly enhances the conductivity, and can be well applied to electrochemical sensors.

[0170] (iv) Mechanical strength testing of molecular sieves

[0171] The layered MWW molecular sieve of Comparative Example 3, and the layered SnO2-MWW molecular sieve and CNTs@SnO2-MWW composite material of Example 1 were tested for mechanical strength through abrasion tests. This is a key indicator for measuring the resistance of molecular sieve samples to friction and wear. The test method is as follows: A certain amount of sample is placed in a specific rotating drum with baffles and rotated at a fixed speed for a certain period of time. The fine powder generated by abrasion is blown out and collected by airflow. The calculation formula is: Abrasion index = (mass of fine powder generated / total mass of initial sample) × 100%.

[0172] Through experiments and calculations, the wear indices of the three samples—layered MWW molecular sieve, layered SnO2-MWW molecular sieve, and CNTs@SnO2-MWW composite material—were obtained to be 0.1% / hour, 0.1% / hour, and 0.3% / hour, respectively. Since lower values ​​indicate stronger wear resistance and better mechanical strength, and for samples with high mechanical strength, a wear index below 0.5% / hour is typically required. Therefore, the results show that the layered MWW molecular sieve, layered SnO2-MWW molecular sieve, and CNTs@SnO2-MWW composite material prepared in this invention all possess good mechanical strength.

[0173] Therefore, the performance testing of the molecular sieve shows that the MWW molecular sieve composite material with high adsorption capacity and conductivity prepared in this invention has the advantages of large specific surface area and high pore volume, as well as excellent conductivity, electrochemical response and electrocatalytic activity, and mechanical strength. Therefore, it has a good application prospect in electrochemical sensors.

[0174] Performance testing of electrochemical sensors

[0175] (i) Cyclic voltammetry curves of molecular sieve composite material layers of different thicknesses

[0176] The electrochemical sensors prepared in Example 7 and Comparative Examples 1-2 were used to determine cyclic voltammetry curves in 0.1 mol / L PBS solution (pH=7) containing 0.005 mol / L chlorogenic acid. Figure 8 As shown. Among them, Figure 8 In the diagram, curve a represents Example 7, curve b represents Comparative Example 1, and curve c represents Comparative Example 2.

[0177] Depend on Figure 8 It can be seen that when the thickness of the molecular sieve composite material layer in Example 7 is 1.25 mm, it exhibits excellent electrochemical responsiveness, resulting in good detection sensitivity and accuracy of the electrochemical sensor. In Comparative Example 1, the thickness of the molecular sieve composite material layer is 0.75 mm. At this thickness, the amount of molecular sieve composite material is too small, leading to fewer adsorption sites on the electrode and weaker adsorption and catalytic ability for chlorogenic acid in the solution, thus reducing the detection sensitivity of the electrochemical sensor. In Comparative Example 2, the thickness of the molecular sieve composite material layer is 1.75 mm. At this thickness, the amount of molecular sieve composite material is too large, resulting in saturation of adsorption sites on the electrode, and even covering the active sites, thereby reducing the electrochemical response and electrocatalytic performance.

[0178] (II) Optimization of chlorogenic acid content detection conditions

[0179] The three-electrode system of the electrochemical workstation was used for testing. The electrochemical sensor prepared in Example 7 was used as the working electrode, denoted as CNTs / SnO2 / MWW / CS / SPE electrode, Ag / AgCl electrode was used as the reference electrode, and carbon electrode was used as the counter electrode. Cyclic voltammetry was performed in PBS buffer solution containing chlorogenic acid to investigate the effects of pH value and scan rate on the corresponding chlorogenic acid current.

[0180] The electrochemical sensor prepared in Example 7 was placed in 0.1 mol / L PBS buffer solutions containing 0.005 mol / L chlorogenic acid under different pH conditions, and its cyclic voltammetry test curves are shown below. Figure 9 As shown.

[0181] Depend on Figure 9 It can be seen that during the oxidation of chlorogenic acid, the separation of electrons and protons leads to the formation of its oxidation products. When the pH value increases from 5.8 to 8.2, the oxidation potential decreases significantly from 0.30V to 0.12V, and the peak oxidation current first increases and then decreases, indicating that protons participate in the oxidation process of chlorogenic acid. The results show that the oxidation peak of chlorogenic acid reaches its maximum current response in 0.1 mol / L PBS (pH=7), meaning that the optimal pH value for detection is 7.

[0182] The electrochemical sensor prepared in Example 7 was placed in a 0.1 mol / L PBS solution (pH=7) containing 0.005 mol / L chlorogenic acid, and its cyclic voltammetry test curve is shown below. Figure 10 As shown.

[0183] Depend on Figure 10It was observed that the anolyte current of chlorogenic acid increased with the scan rate, which increased from 20 mV / s to 200 mV / s. Furthermore, the oxidation peak potential shifted continuously to the positive direction, while the reduction peak potential shifted continuously to the negative direction, indicating that electron transfer is kinetically limited at higher scan rates, and that the process is a reversible redox process. Simultaneously, a scan rate that was too slow resulted in a longer reaction time; a scan rate that was too fast increased instability during electrode detection. Therefore, the optimal scan rate selected in this experiment was 100 mV / s.

[0184] (III) Electrochemical performance testing of electrochemical sensors

[0185] The tests were conducted using a three-electrode system of an electrochemical workstation. The electrochemical sensor prepared in Example 7 was used as the working electrode, denoted as the CNTs / SnO2 / MWW / CS / SPE electrode. The Ag / AgCl electrode served as the reference electrode, and the carbon electrode as the counter electrode. Cyclic voltammetry was performed in 0.1 mol / L PBS buffer solution (pH=7) containing chlorogenic acid and in 0.1 mol / L PBS buffer solution (pH=7) without chlorogenic acid, respectively. The initial potential was 0 V, the scan rate was 100 mV / s, and the sampling interval was 0.001 V. The test results are as follows: Figure 11 As shown. Figure 11 Curve a represents a PBS buffer solution containing chlorogenic acid, and curve b represents a PBS buffer solution without chlorogenic acid.

[0186] Depend on Figure 11 It can be seen that in the blank electrolyte solution without chlorogenic acid, the working electrode shows almost no redox peaks. After adding a certain amount of chlorogenic acid, the electrode shows a significant oxidation peak at a potential of 0.20 V and a significant reduction peak at a potential of 0.15 V, exhibiting good electrochemical performance. The results indicate that the reaction process is reversible.

[0187] (iv) Selectivity testing of electrochemical sensors

[0188] The tests were conducted using a three-electrode system of an electrochemical workstation. The electrochemical sensor prepared in Example 7 was used as the working electrode, denoted as the CNTs / SnO2 / MWW / CS / SPE electrode. The Ag / AgCl electrode was used as the reference electrode, and the carbon electrode was used as the counter electrode. Fe3+ with a chlorogenic acid concentration of 10 times the concentration of chlorogenic acid was added to a 0.1 mol / L PBS buffer solution (pH=7) containing 0.001 mol / L chlorogenic acid. 3 + K + Na + Zn 2+ Cl -Differential pulse voltammetry was used to test the electrochemical response of chlorogenic acid solution with solutions containing glutamic acid (Glu), tyrosine (Tyr), acetic acid (HAc), glucose (Glc), vitamin A (VA), ascorbic acid (AA), urea (UR), creatinine (CR), and dopamine (DA). The effects of these interfering substances on the electrochemical response of chlorogenic acid solution were compared to verify the selectivity of the CNTs / SnO2 / MWW / CS / SPE electrode. The test results are as follows: Figure 12 As shown.

[0189] Depend on Figure 12 It can be seen that the addition of these interfering substances has little effect on the electrochemical response of chlorogenic acid solution, and the change in oxidation current signal is small (<8%), indicating that the prepared electrochemical sensor has good anti-interference ability.

[0190] (v) Reproducibility testing of electrochemical sensors

[0191] The three-electrode system of an electrochemical workstation was used for testing. The electrochemical sensor prepared in Example 7 was used as the working electrode, denoted as the CNTs / SnO2 / MWW / CS / SPE electrode. The Ag / AgCl electrode was used as the reference electrode, and the carbon electrode was used as the counter electrode. The chlorogenic acid solution was measured eight times using the same CNTs / SnO2 / MWW / CS / SPE electrode in a 0.1 mol / L PBS buffer solution (pH=7) containing 0.001 mol / L chlorogenic acid. Measurements were taken every three days for a total of 24 days. The differential pulse voltammetric current values ​​were recorded to verify the reproducibility of the modified electrode. The test results are as follows: Figure 13 As shown.

[0192] Depend on Figure 13 It can be seen that the difference in current values ​​among the 8 measurements is small, and the current loss rate is <4%, indicating that the CNTs / SnO2 / MWW / CS / SPE electrode has good reproducibility.

[0193] (vi) Stability testing of electrochemical sensors

[0194] The tests were conducted using a three-electrode system on an electrochemical workstation. The electrochemical sensor prepared in Example 7 was used as the working electrode, denoted as the CNTs / SnO2 / MWW / CS / SPE electrode. The Ag / AgCl electrode was used as the reference electrode, and the carbon electrode was used as the counter electrode. The electrode was prepared in an atmosphere containing 5.0 × 10⁻⁶ ppm of electrolyte. -3 M Fe(CN)6 3- / 4- In 0.1 M KCl solution, 100 segments were scanned at a scan rate of 100 mV / s. The stability of the electrochemical sensor was tested using cyclic voltammetry. The test results are as follows: Figure 14 As shown.

[0195] Depend on Figure 14It can be seen that after multiple cyclic scans, the CV curve of the electrochemical sensor remains basically unchanged, indicating that the prepared electrochemical sensor has good stability.

[0196] (vii) Detection of chlorogenic acid standard solutions of different concentrations

[0197] The three-electrode system of an electrochemical workstation was used for testing. The electrochemical sensor prepared in Example 7 was used as the working electrode, denoted as the CNTs / SnO2 / MWW / CS / SPE electrode. The Ag / AgCl electrode was used as the reference electrode, and the carbon electrode was used as the counter electrode. Differential pulse voltammetry was used to detect 0.1 mol / L PBS solutions containing different concentrations of chlorogenic acid. The initial potential was 0 V, the potential increment was 0.004 V, the amplitude was 0.025 V, the pulse width was 50 ms, and the pulse period was 200 ms. The test results are as follows: Figure 15 As shown.

[0198] Depend on Figure 15 (a) It can be seen that in the potential range of 0~0.4V, when the concentration of chlorogenic acid increases from 0.05μmol / L to 1500μmol / L, the peak current increases with the increase of chlorogenic acid concentration. Figure 15 (b) shows the linear relationship between peak current and corresponding concentration (R0). 2 =0.9980), indicating that the CNTs / SnO2 / MWW / CS / SPE electrode achieved a wide detection range and a low detection limit, with a detection range of 0.05 μmol / L to 1500 μmol / L and a detection limit of 0.02 μmol / L. Therefore, this demonstrates that the electrochemical sensor prepared in this invention has the advantages of a wide detection range and a low detection limit.

[0199] (viii) Detection of chlorogenic acid content in actual food

[0200] The three-electrode system of the electrochemical workstation was used for testing. The electrochemical sensor prepared in Example 7 was used as the working electrode, denoted as CNTs / SnO2 / MWW / CS / SPE electrode. The Ag / AgCl electrode was used as the reference electrode, and the carbon electrode was used as the counter electrode. The solutions of the three food samples (green tea, plum and blueberry) were used to replace the chlorogenic acid standard solution for detection by differential pulse voltammetry. The test results are shown in Table 2.

[0201] As shown in Table 2, the recovery rates of the three food samples were between 95.36% and 98.69% after three parallel determinations. The relative standard deviations (RSDs) of green tea, plum, and blueberry were 1.39%, 2.02%, and 2.33%, respectively, indicating that the CNTs / SnO2 / MWW / CS / SPE electrode has high reproducibility and accuracy in determining the chlorogenic acid content in actual food.

[0202] Table 2. Detection of chlorogenic acid content in different foods

[0203]

[0204] (ix) Comparative analysis of electrochemical response performance

[0205] The test was conducted using a three-electrode system on an electrochemical workstation, containing 1×10⁻⁶ electrodes. -3 Electrochemical behavior analysis was performed using electrochemical sensors prepared in Example 7, Comparative Example 4, and Comparative Example 5 as working electrodes (denoted as CNTs / SnO2 / MWW / CS / SPE electrode, SnO2 / MWW / CS / SPE electrode, and CNTs / MWW / CS / SPE electrode, respectively) in a 1 mol / L CGA solution in PBS (pH = 7). The electrochemical response curves for DPV and CV are shown below. Figure 16 As shown.

[0206] Depend on Figure 16 (a) The results show that the DPV current of the SnO2 / MWW / CS / SPE sensor is 19.78 μA, while the CNTs / MWW / CS / SPE sensor has a lower performance signal and a DPV current of 15.14 μA. When the two are combined, the oxidation current response of the CNTs / SnO2 / MWW / CS / SPE sensor is significantly enhanced, with a DPV current of 27.46 μA. Figure 16 (b) The results show that the CV current of the SnO2 / MWW / CS / SPE sensor is 45.73 μA, while the CNTs / MWW / CS / SPE sensor has a lower performance signal and a CV current of 32.95 μA. When the two are combined, the oxidation current response of the CNTs / SnO2 / MWW / CS / SPE sensor is significantly enhanced, with a CV current of 61.37 μA. Electrochemical experiments on DPV and CV show that the synergistic effect of SnO2 and CNTs jointly promotes electron transfer and improves the electrochemical performance of the CNTs / SnO2 / MWW / CS / SPE sensor.

[0207] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A MWW molecular sieve composite material having high adsorption capacity and electrical conductivity, characterized in that, The preparation method of the MWW molecular sieve composite material with high adsorption capacity and conductivity includes the following steps: S1. Preparation of aluminosilicate gel: Cyclohexylamine, sodium aluminate, sodium hydroxide, and silica sol are mixed in water to obtain aluminosilicate gel; S2. Preparation of sheet-like SnO2-MWW molecular sieve: The aluminosilicate gel is mixed in situ with tin dioxide, and then heated at 140℃~180℃ for 24h~54h. After filtration, washing, drying and calcination at 500℃~700℃ for 3h~5h, sheet-like MWW molecular sieve loaded with tin dioxide material is obtained, which is the sheet-like SnO2-MWW molecular sieve; the molar ratio of cyclohexylamine, sodium aluminate, sodium hydroxide, silica sol, water and tin dioxide is (2~20):(0.1~5):(0.1~5):(5~50):(100~400):(0.1~5); S3. Loaded carbon nanotubes: The sheet-like SnO2-MWW molecular sieve and carbon nanotubes are added to a chitosan solution and stirred at 25℃~40℃ for 2h~4h. Then, the mixture is centrifuged, the precipitate is collected, washed and dried to obtain CNTs@SnO2-MWW composite material, which is the MWW molecular sieve composite material with high adsorption capacity and conductivity. The mass ratio of the sheet-like SnO2-MWW molecular sieve to the carbon nanotubes is (0.5~2):(0.1~3); the mass ratio of the chitosan solution to the sheet-like SnO2-MWW molecular sieve is 1:(3~7).

2. A MWW molecular sieve composite material of high adsorption capacity and electrical conductivity according to claim 1, characterized in that In step S1, the mixing method is magnetic stirring, the temperature of magnetic stirring is 20℃~40℃, and the time of magnetic stirring is 2h~4h.

3. A high adsorbent capacity and conductive MWW molecular sieve composite material according to claim 1, wherein, In step S2, the in-situ mixing method is magnetic stirring, the temperature of magnetic stirring is 20℃~40℃, and the stirring time is 2h~4h; and / or The drying temperature is 100℃~150℃, and the drying time is 2h~6h; and / or The washing process involves using deionized water.

4. The high adsorbent capacity and conductive MWW molecular sieve composite material of claim 1, wherein, In step S3, the concentration of the chitosan solution is 0.02wt%~0.3wt%; and / or The drying temperature is 80℃~100℃, and the drying time is 6h~8h; and / or The washing process involves using anhydrous ethanol.

5. A method of preparing an electrochemical sensor, characterized by, Includes the following steps: S1. Disperse the MWW molecular sieve composite material with high adsorption capacity and conductivity as described in any one of claims 1 to 4 in a solvent to obtain a molecular sieve composite material suspension; S2. The molecular sieve composite material suspension is drop-coated onto a screen-printed electrode and dried to evaporate the solvent, thereby obtaining the electrochemical sensor; the thickness of the molecular sieve composite material layer formed after the molecular sieve composite material suspension is drop-coated onto the screen-printed electrode and dried is 1 mm to 1.5 mm.

6. A method of preparing an electrochemical sensor as claimed in claim 5, wherein, In step S1, the concentration of the molecular sieve composite material suspension is 5 mg / mL to 15 mg / mL; and / or The solvent is a chitosan solution with a concentration of 0.3 wt% to 0.7 wt%; and / or The dispersion method involves ultrasonic treatment for 20 to 40 minutes.

7. The method for preparing an electrochemical sensor as described in claim 5, characterized in that, In step S2, the drying method is natural air drying at room temperature.

8. An electrochemical sensor, characterized by It is prepared by the method of preparing an electrochemical sensor according to any one of claims 5 to 7.

9. Use of an electrochemical sensor, characterized in that The application of the electrochemical sensor according to claim 8 in detecting chlorogenic acid content.

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