A MXene-doped silver modified mesoporous MEL molecular sieve composite material, an electrochemical sensor and a preparation method and application thereof

Abstract

The present application relates to the technical fields of nanomaterials and electrochemical catalysts, and specifically relates to a MXene doped silver modified mesoporous MEL molecular sieve composite material, an electrochemical sensor, a preparation method and application thereof, and specifically relates to application in detecting content of gallic acid; the molecular sieve composite material is prepared by modifying mesoporous MEL molecular sieve with metal silver, and then compounding MXene material with the silver modified mesoporous MEL molecular sieve; the prepared MXene doped silver modified mesoporous MEL molecular sieve composite material has high specific surface area, high pore volume and excellent conductivity; the electrochemical sensor for detecting content of gallic acid has the advantages of wide detection range and low detection limit; the detection range is 1-50000 mu mol / L, and the detection limit can reach 0.5 mu mol / L; meanwhile, the electrochemical sensor has excellent detection sensitivity, stability, reproducibility, anti-interference and mechanical stability, can realize accurate determination of content of gallic acid in drugs, and has simple structure, convenient operation, low detection cost and good application prospect.

Description

Technical Field

[0001] This invention relates to the fields of nanomaterials and electrochemical catalysts, specifically to an MXene-doped silver-modified mesoporous MEL molecular sieve composite material, an electrochemical sensor, its preparation method and application, and particularly to its application in detecting gallic acid content. Background Technology

[0002] MEL molecular sieves are porous materials with a unique pore structure and high specific surface area. Their pore sizes are uniform and shape-selective, enabling molecular-level sieving based on differences in molecular size and polarity. Currently, these characteristics make MEL molecular sieves widely used in gas separation, catalytic reactions, and other fields.

[0003] Gallic acid (GA) is a natural polyphenol compound (C7H6O5) with potent biological activities, including antioxidant, antibacterial, anti-inflammatory, and antitumor effects. These properties make it widely used in the chemical, pharmaceutical, food, and agricultural industries. The concentration of GA in human body fluids is an important biomarker for monitoring its metabolic pathways. Blood GA levels are typically between 0.01 and 0.1 μM. Maintaining plasma GA concentrations between 0.1 and 10 μM through dietary or pharmaceutical intake has been shown to have therapeutic effects, while short-term increases in GA concentration to 50 μM are beneficial for specific clinical treatments. However, as an acidic compound, excessive intake of GA can cause adverse reactions such as gastrointestinal irritation, abdominal pain, and diarrhea. Long-term excessive intake can even impair liver metabolic function, leading to liver failure. Furthermore, strict control of intake is necessary for specific populations (those with impaired liver function and pregnant women) to prevent drug accumulation and reduce risks to fetal development. Given the importance of gallic acid (GA) monitoring in assessing bioactivity, pharmacokinetics, and safety, developing a simple, sensitive, and inexpensive technique to detect gallic acid content in drugs is of significant practical importance for quality control of gallic acid in pharmaceuticals and for personalized health management.

[0004] Currently, there are various methods for detecting gallic acid (GA) content, each with its own advantages and disadvantages. For example, the common high-performance liquid chromatography (HPLC) method for GA determination, while highly accurate, is expensive and time-consuming; ultraviolet-visible spectrophotometry (UV-Vis), although rapid, is complex to operate and has poor specificity; fluorescence spectroscopy has high sensitivity but poor stability; capillary electrophoresis (HPCE) offers advantages such as diverse operating modes and small sample volumes, but is also time-consuming, labor-intensive, and expensive. These traditional methods not only require sophisticated instruments but also involve cumbersome sample pretreatment, making real-time monitoring inconvenient.

[0005] Electrochemical sensors can rapidly and sensitively detect target information and then directly or indirectly convert it into electrical signals, thereby enabling qualitative and quantitative analysis of the target analytes. They possess advantages such as high sensitivity, simple structure, and low cost, and have promising prospects in the field of analytical detection. The sensitivity of electrochemical sensors mainly depends on the performance of the electrode surface modification materials (such as carbon nanotubes, graphene, and porous materials). Currently, the sensitivity, detection limit, and detection range of electrochemical sensors used to detect gallic acid still need improvement.

[0006] Furthermore, in the preparation of MEL molecular sieves, template agents and silicon sources play crucial roles in the synthesis, controlling the specific surface area of ​​the molecular sieve material by regulating its crystallinity and pore structure. However, the specific surface area and pore volume of MEL molecular sieves prepared using template agents in existing technologies are still insufficient, and MEL molecular sieves themselves exhibit weak conductivity. Therefore, directly applying MEL molecular sieves to electrochemical sensors results in insufficient detection accuracy and sensitivity. 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 MXene-doped silver-modified mesoporous MEL molecular sieve composite materials. This method is simple, and the resulting composite material has the advantages of large specific surface area, high adsorption capacity, and excellent conductivity.

[0008] To overcome the shortcomings of the prior art, the second objective of this invention is to provide an MXene-doped silver-modified mesoporous MEL molecular sieve composite material, which has the advantages of large specific surface area, high adsorption capacity, and excellent 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 gallic acid content.

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

[0013] This invention provides a method for preparing MXene-doped silver-modified mesoporous MEL molecular sieve composite materials, comprising the following steps:

[0014] S1. Preparation of mesoporous MEL molecular sieve: Tetraethyl orthosilicate, aluminum sulfate octadecylhydrate and tetrabutylammonium hydroxide are mixed in water to obtain aluminosilicate gel, which is then heated and reacted. After filtration, washing, drying and calcination, mesoporous MEL molecular sieve is obtained.

[0015] S2. Silver-modified mesoporous MEL molecular sieve: The mesoporous MEL molecular sieve is subjected to an ion exchange reaction with a silver ion solution, and then the precipitate is collected, dried and calcined to obtain a mesoporous Ag-MEL molecular sieve, which is the silver-modified mesoporous MEL molecular sieve.

[0016] S3, MXene doping: The mesoporous Ag-MEL molecular sieve and MXene are added to a chitosan solution, stirred and reacted, then centrifuged, the precipitate is collected, washed and dried to obtain the composite material MXene@Ag-MEL, that is, the MXene-doped silver-modified mesoporous MEL molecular sieve composite material is prepared.

[0017] In step S3, the chitosan solution acts as a robust and biocompatible "glue" for the interdoping of mesoporous Ag-MEL molecular sieve and MXene, and can effectively disperse the mesoporous Ag-MEL molecular sieve and MXene, preventing their aggregation.

[0018] The present invention discloses a method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material. This method involves using tetrabutylammonium hydroxide as a template agent, along with tetraethyl orthosilicate and aluminum sulfate octadecylhydrate, to prepare a mesoporous MEL molecular sieve. The mesoporous MEL molecular sieve is then modified with metallic silver using a silver ion solution. Finally, the MXene material is composited with the silver-modified mesoporous MEL molecular sieve. The resulting MXene-doped silver-modified mesoporous MEL molecular sieve composite material exhibits a large specific surface area, high adsorption capacity, and excellent conductivity. Therefore, this MXene-doped silver-modified mesoporous MEL molecular sieve composite material is suitable for use in electrochemical sensors for detecting gallic acid content, achieving high detection accuracy, high detection sensitivity, and a wide detection range. Furthermore, the resulting electrochemical sensor has a simple structure, is easy to operate, and has low detection costs.

[0019] In the silver-modified mesoporous MEL molecular sieve step, the reaction principle of obtaining mesoporous Ag-MEL molecular sieves through ion exchange reaction is as follows:

[0020] (1) Ion exchange and electrostatic interaction between Ag and mesoporous MEL molecular sieves: After silicon (Si) in the MEL molecular sieve framework is replaced by aluminum (Al), it will carry a negative charge. In order to maintain electroneutrality, cations (such as H+) are required. + Na + (etc.) to balance. When Ag is introduced + At that time, Ag +It will react with existing cations (such as Na) + ion exchange occurs, occupying these cation sites, Ag + With the negatively charged aluminum-oxygen tetrahedra ([AlO2]) in the framework - The two atoms are bonded together by electrostatic interaction, which is a relatively strong ionic bond.

[0021] (2) Coordination interaction between Ag and mesoporous MEL molecular sieves: Ag + Having d 10 The electronic configuration of the MEL molecular sieve exhibits a strong tendency to form coordinate bonds. Within the channels and cages of the sieve, there are numerous bridging oxygen atoms (Si-O-Al, Si-O-Si). The lone pairs of electrons on these oxygen atoms can act as electron donors, interacting with Ag... + Coordination interactions occur, forming a coordinate bond, which can be viewed as Ag... + Binding to Lewis base sites (oxygen).

[0022] (3) Reduction and clustering of Ag with mesoporous MEL molecular sieves: Under heating, light, or voltage conditions, Ag... + Spontaneous reduction, through the donation of electrons by certain groups in the MEL molecular sieve framework (such as defect sites, carbon residues in organic template agents) or external conditions, allows Ag to undergo spontaneous reduction. + Reduced to silver atoms (Ag) 0 These Ag 0 Atoms possess high mobility and tend to aggregate, forming silver clusters (Ag) of defined size, consisting of several to tens of atoms, within the nanoscale channels or cages of MEL molecular sieves. x These silver clusters are held together by metallic bonds. The pore structure of the MEL molecular sieve acts like a "nanoreactor," stabilizing these tiny silver clusters and preventing them from growing further into macroscopic silver particles.

[0023] In the MXene doping step, the reaction mechanism between MXene and mesoporous Ag-MEL molecular sieve is as follows:

[0024] (1) Interfacial physical interactions occur between MXene and mesoporous Ag-MEL molecular sieves, which is the basis for their bonding. These interactions mainly occur between the surface functional groups of MXene and the surface or pores of Ag-MEL molecular sieves. These interfacial physical interactions include the following two types: 1) Electrostatic adsorption: The surface of MXene is usually negatively charged (e.g., -O and -OH functional groups), while the silver ions (Ag) in the mesoporous Ag-MEL molecular sieve... +1) Some cation sites are positively charged, and electrostatic attraction will be generated between them, making them come into close contact. This is the first step in forming a stable composite structure; 2) Hydrogen bonding: Hydrogen bonds can be formed between the -OH functional groups on the MXene surface and the silanol groups (Si-OH) or framework oxygen on the surface of the mesoporous Ag-MEL molecular sieve. Although this force is weaker than chemical bonds, it can effectively enhance interfacial bonding and stability.

[0025] (2) Interfacial chemical bonding occurs between MXene and mesoporous Ag-MEL molecular sieves, including the following two effects: 1) Ag + Coordination with MXene functional groups: The abundant oxygen-containing functional groups (-O, -OH) on the MXene surface can act as electron donors (Lewis bases), coordinating with the highly mobile Ag in mesoporous Ag-MEL molecular sieves. + Alternatively, Ag clusters (Lewis acids) may coordinate to form Ag-O. x (MXene) type coordination bonds, thereby creating new and stronger chemical connections at the interface; 2) Covalent bonds: The functional groups on the surface of MXene may undergo dehydration condensation with the surface hydroxyl groups of mesoporous Ag-MEL molecular sieves to form weak covalent connections (such as Ti-O-Si).

[0026] Furthermore, in step S1, the molar ratio of tetraethyl orthosilicate, aluminum sulfate octadecyl hydrate, tetrabutylammonium hydroxide, and water is (200~600):(0.1~3):(50~300):(200~700).

[0027] Preferably, the molar ratio of tetraethyl orthosilicate, aluminum sulfate octadecyl hydrate, tetrabutylammonium hydroxide and water is (300~500):(0.5~2):(100~250):(300~500).

[0028] More preferably, the molar ratio of tetraethyl orthosilicate, aluminum sulfate octadecylhydrate, tetrabutylammonium hydroxide and water is 400:1:160:420;

[0029] In this invention, the template agent used is tetrabutylammonium hydroxide, whose carbon chains can guide the formation of mesopores, opening the channels of the MEL molecular sieve, shortening the diffusion path, and reducing its diffusion resistance. Using tetrabutylammonium hydroxide, a mesoporous MEL molecular sieve can be prepared in one step, greatly increasing its specific surface area and pore volume. A larger specific surface area and higher adsorption capacity of the molecular sieve promote the participation of more active sites in the reaction, allowing more target molecules to be rapidly reacted in a short time, thereby improving the reactivity of the molecular sieve. This invention, by controlling the appropriate ratio of tetraethyl orthosilicate, aluminum sulfate octadecylhydrate, tetrabutylammonium hydroxide, and water, enables the prepared mesoporous MEL molecular sieve to have a large specific surface area and adsorption capacity.

[0030] In addition, in the process of silver-modified mesoporous MEL molecular sieves, since metallic silver has excellent conductivity, modifying the mesoporous MEL molecular sieve with metallic silver can enhance the conductivity of the molecular sieve. Furthermore, by further compounding with MXene material, which has strong conductivity and high diffusivity, the resulting MXene-doped silver-modified mesoporous MEL molecular sieve composite material can significantly enhance its electrocatalytic activity as a working electrode of an electrochemical sensor.

[0031] The mixing method is magnetic stirring, the temperature of the magnetic stirring is 20℃~40℃, and the stirring time is 4h~6h; and / or

[0032] The heating reaction temperature is 150℃~190℃, and the heating reaction time is 24h~48h; and / or

[0033] The drying temperature is 120℃~150℃, and the drying time is 4h~6h; and / or

[0034] The calcination temperature is 500℃~600℃, and the calcination time is 4h~5h; and / or

[0035] The washing process involves using deionized water.

[0036] In step S1, during the preparation of mesoporous MEL molecular sieves, this invention controls a suitable reaction temperature to ensure that the prepared mesoporous MEL molecular sieves have a large specific surface area and adsorption capacity. Furthermore, if the reaction temperature is too high, the MEL molecular sieve crystallizes too quickly, leading to the formation of impurities; if the reaction temperature is too low, the energy for MEL molecular sieve growth is insufficient, resulting in a slow crystallization rate and potentially leading to amorphous crystals, thus failing to form well-structured mesoporous MEL molecular sieves.

[0037] Furthermore, in step S2, the concentration of the silver ion solution is 0.001 mol / L to 0.1 mol / L; preferably, the concentration of the silver ion solution is 0.01 mol / L.

[0038] The mass-to-volume ratio of the mesoporous MEL molecular sieve to the silver ion solution is 1 g: (15~25) mL; and / or

[0039] The silver ion solution is at least one of silver nitrate solution and silver acetate solution; and / or

[0040] The temperature for the ion exchange reaction between the mesoporous MEL molecular sieve and the silver ion solution is 40℃~80℃, and the reaction time is 6h~16h; and / or

[0041] The drying temperature is 60℃~100℃, and the drying time is 8h~16h; and / or

[0042] The calcination temperature is 500℃~600℃, and the calcination time is 5h~6h.

[0043] In step S2, the silver-modified mesoporous MEL molecular sieve undergoes an ion exchange reaction with a silver ion solution. By controlling the appropriate concentration of the silver ion solution and the reaction time, this invention enables the prepared silver-modified mesoporous MEL molecular sieve to exhibit excellent conductivity and maintain a large specific surface area. Furthermore, if the concentration of the silver ion solution is too high, it will lead to excessive clogging of the pores in the silver-modified mesoporous MEL molecular sieve, reducing the specific surface area and thus decreasing the active sites. Conversely, if the concentration of the silver ion solution is too low, the silver content in the molecular sieve after the ion exchange reaction will be too low, resulting in poor conductivity of the silver-modified mesoporous MEL molecular sieve.

[0044] Furthermore, if the ion exchange reaction time is too long, it will lead to pore blockage of the silver-modified mesoporous MEL molecular sieve and a certain degree of etching on the surface of the molecular sieve, thereby reducing the specific surface area of ​​the silver-modified mesoporous MEL molecular sieve and thus reducing its catalytic performance. If the ion exchange reaction time is too short, the ion exchange will be insufficient, which will result in too little silver content in the framework of the silver-modified mesoporous MEL molecular sieve, thereby reducing its electrical conductivity.

[0045] Furthermore, in step S3, the preparation method of MXene is as follows: after acid etching of LiF powder, Ti3AlC2 powder is added, and after stirring, centrifugation, washing and ultrasonic treatment, the product is collected and dried to obtain Ti3C2T. x That is, the MXene is obtained.

[0046] Further, in step S3, the mass ratio of the mesoporous Ag-MEL molecular sieve to MXene is (0.1~3):(0.1~5); preferably, the mass ratio of the mesoporous Ag-MEL molecular sieve to MXene is (0.5~2):(0.5~3); more preferably, the mass ratio of the mesoporous Ag-MEL molecular sieve to MXene is 1:1.

[0047] In step S3, during the MXene doping process, the present invention, by controlling the appropriate ratio of the mesoporous Ag-MEL molecular sieve to MXene, enables the obtained MXene-doped silver-modified mesoporous MEL molecular sieve composite material to possess excellent electrical conductivity and oxidation performance. Furthermore, if the ratio of mesoporous Ag-MEL molecular sieve to MXene is too high, the specific surface area and active sites of the obtained MXene-doped silver-modified mesoporous MEL molecular sieve composite material will decrease, thereby reducing its electrochemical response performance. Conversely, if the ratio of mesoporous Ag-MEL molecular sieve to MXene is too low, the conductivity of the obtained MXene-doped silver-modified mesoporous MEL molecular sieve composite material will decrease, thereby reducing its oxidation performance and electrochemical response performance.

[0048] The mass ratio of the chitosan solution to the mesoporous Ag-MEL molecular sieve is 1:(4~6); and / or

[0049] The concentration of the chitosan solution is 0.05wt%~0.2wt%; and / or

[0050] The temperature of the stirring reaction is 25℃~40℃, and the stirring reaction time is 4h~6h; and / or

[0051] The drying temperature is 40℃~60℃, and the drying time is 10h~14h; and / or

[0052] The washing process involves using anhydrous ethanol.

[0053] To achieve the second objective of the invention, the technical solution adopted by the present invention is as follows:

[0054] This invention provides an MXene-doped silver-modified mesoporous MEL molecular sieve composite material, which is prepared by the above-described method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material.

[0055] To achieve the third objective of the invention, the technical solution adopted by the present invention is as follows:

[0056] This invention provides an electrochemical sensor, which is made from the above-described MXene-doped silver-modified mesoporous MEL molecular sieve composite material.

[0057] To achieve the fourth objective of the invention, the technical solution adopted by the present invention is as follows:

[0058] This invention provides a method for preparing an electrochemical sensor, comprising the following steps:

[0059] S1. Disperse the MXene-doped silver-modified mesoporous MEL molecular sieve composite material as described in claim 6 in a solvent to obtain a molecular sieve composite material suspension;

[0060] 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.

[0061] Furthermore, in step S1, the concentration of the molecular sieve composite material suspension is 5 mg / mL to 20 mg / mL; and / or

[0062] In step S1, the solvent is a chitosan solution; the concentration of the chitosan solution is 0.4 wt% to 0.6 wt%.

[0063] In this study, chitosan solution was used as the solvent for dispersing MXene-doped silver-modified mesoporous MEL molecular sieve composite materials. As a strong and biocompatible "glue", chitosan solution can firmly fix the active substances in the MXene-doped silver-modified mesoporous MEL molecular sieve composite materials onto the screen-printed electrode surface. Chitosan replaces traditional toxic and non-degradable adhesives, and the modified electrode has the advantages of being environmentally friendly, non-toxic, low-cost, and easily degradable. It can also form a uniform, stable, and strongly adhesive film on the electrode surface.

[0064] In step S1, the dispersion is achieved by ultrasonic treatment for 50-70 minutes; and / or

[0065] In step S2, the volume of the molecular sieve composite material suspension drop-coated onto the screen-printed electrode is 4 μL to 6 μL; and / or

[0066] In step S2, the drying method is natural air drying at room temperature.

[0067] In one method for preparing an electrochemical sensor according to the present invention, by controlling the concentration of the molecular sieve composite material suspension and the amount of suspension dropped onto the screen-printed electrode, the prepared electrochemical sensor can exhibit excellent detection performance. Specifically, the concentration of the molecular sieve composite material suspension affects its dispersion state on the electrode. If the concentration of the molecular sieve composite material suspension is too high or the amount of suspension dropped is excessive, the adsorption sites on the electrode become saturated, limiting its catalytic ability for gallic acid and leading to a decrease in the detection sensitivity of the electrochemical sensor. Conversely, if the concentration of the molecular sieve composite material suspension is too low or the amount of suspension dropped is insufficient, there will be fewer adsorption sites on the electrode, resulting in a weaker reactivity to gallic acid, thereby reducing the detection sensitivity and accuracy of the electrochemical sensor.

[0068] The electrochemical sensor prepared by this invention has the advantages of simple structure, low preparation cost, convenient operation, and low detection cost.

[0069] To achieve the fifth objective of the invention, the technical solution adopted by the present invention is as follows:

[0070] 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 gallic acid content.

[0071] The electrochemical sensor prepared by this invention can overcome the defects and shortcomings of existing gallic acid content detection technologies, such as complex equipment, high detection cost, low detection accuracy, and poor detection sensitivity. The electrochemical sensor of this invention has the advantages of low detection cost, high detection accuracy, good detection sensitivity, and wide detection range when applied to the detection of gallic acid content.

[0072] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0073] (1) A method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material according to the present invention involves preparing a mesoporous MEL molecular sieve by using a template agent tetrabutylammonium hydroxide and synergistically controlling the proportion of each raw material. Then, the mesoporous MEL molecular sieve is modified with metallic silver using a silver ion solution. Finally, the MXene material is composited with the silver-modified mesoporous MEL molecular sieve, resulting in an MXene-doped silver-modified mesoporous MEL molecular sieve composite material with a large specific surface area, high adsorption capacity, and excellent conductivity. The total specific surface area of ​​the MXene-doped silver-modified mesoporous MEL molecular sieve composite material prepared according to the present invention is greater than 400 m². 2 / g, total pore volume greater than 0.3m 3 / g.

[0074] (2) The present invention provides a method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material, which 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. Specifically, by modifying the mesoporous MEL molecular sieve with metallic silver, the molecular sieve acquires good conductivity, increasing the electrocatalytic activity of the working electrode in electrochemical sensors. Furthermore, by combining MXene with the silver-modified mesoporous MEL molecular sieve, on the one hand, MXene, as a support, can effectively prevent the aggregation of Ag-MEL molecular sieve particles, thus exposing more active sites; on the other hand, the extremely high conductivity of MXene provides a continuous electron conduction path for the Ag-MEL molecular sieve, thereby greatly reducing the overall resistance of the composite material, enabling the MXene-doped silver-modified mesoporous MEL molecular sieve composite material to exhibit excellent performance when applied in electrochemical sensors.

[0075] (3) The MXene-doped silver-modified mesoporous MEL molecular sieve composite material of the present invention has the advantages of large specific surface area, high total pore volume, and excellent conductivity. Since Ag ions can not only improve the conductivity of the mesoporous MEL molecular sieve itself, but also optimize charge transport at the interface, and in addition, with the extremely high conductivity of MXene, it provides a continuous electronic conduction path for the Ag-MEL molecular sieve, thereby enabling the composite material to exhibit excellent electrochemical performance in electrochemical sensors. In addition, the Ag-MEL molecular sieve has regular channels, which can be used to "pre-organize" and "shape select" reactants during application. The synergistic effect of the active sites on the Ag-MEL molecular sieve and MXene surface can greatly enhance the electrocatalytic performance of the composite material.

[0076] (4) The present invention provides an MXene-doped silver-modified mesoporous MEL molecular sieve composite material. The composite of MXene and Ag-MEL molecular sieve works through chemical bonding (coordination bond, charge transfer) and physical adsorption (electrostatic, hydrogen bond). The conductivity and two-dimensional structure of MXene are combined with the large specific surface area, high active sites and stability of Ag-MEL molecular sieve, thus making the MXene-doped silver-modified mesoporous MEL molecular sieve composite material have good application prospects in the fields of catalysis and sensing.

[0077] (5) An electrochemical sensor of the present invention is prepared by drop-coating a suspension formed by the MXene-doped silver-modified mesoporous MEL molecular sieve composite material prepared by the present invention onto a screen-printed electrode. Since the MXene-doped silver-modified mesoporous MEL molecular sieve composite material has the advantages of good hydrothermal stability, unique pore structure, large specific surface area, high total pore volume and excellent conductivity, the electrochemical sensor prepared has the advantages of low detection cost, high detection accuracy, good detection sensitivity and wide detection range. Moreover, the preparation method of the electrochemical sensor is simple and the prepared electrochemical sensor is easy to operate.

[0078] (6) Application of an electrochemical sensor of the present invention in the detection of gallic acid content. The electrochemical sensor has the advantage of a wide detection linear range, which is 1 μmol / L to 50000 μmol / L, and a low detection limit, which can reach 0.5 μmol / L. It also has excellent sensing characteristics such as detection sensitivity, stability, reproducibility and anti-interference. It can realize the accurate determination of gallic acid content in drugs and reduce detection costs, and has a good application prospect. Attached Figure Description

[0079] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0080] Figure 1 The images show the XRD patterns of the mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, MXene, and MXene@Ag-MEL prepared in Example 1 of this invention.

[0081] Figure 2 The images show SEM images of the mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, MXene, and MXene@Ag-MEL prepared in Example 1 of this invention.

[0082] Figure 3 TEM images of the mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, MXene, and MXene@Ag-MEL prepared in Example 1 of this invention.

[0083] Figure 4 The energy dispersive X-ray spectra of mesoporous Ag-MEL molecular sieves, MXene, and MXene@Ag-MEL prepared in Example 1 of this invention are shown.

[0084] Figure 5The X-ray photoelectron spectroscopy (XPS) spectra of the mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, and MXene@Ag-MEL prepared in Example 1 of this invention are shown.

[0085] Figure 6 The nitrogen adsorption-desorption isotherms and BJH pore size distribution analysis diagrams of the mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, and MXene@Ag-MEL prepared in Example 1 of this invention are shown.

[0086] Figure 7 The time-coulomb curves for detecting the electrocatalytic activity of the mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, and MXene@Ag-MEL prepared in Example 1 of this invention are shown.

[0087] Figure 8 The cyclic voltammetry curves of the electrochemical sensors prepared in Examples 7-9 of this invention were measured in 0.1 mol / L PBS solution (pH=2) containing 0.01 mol / L gallic acid.

[0088] 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 0.02 mol / L gallic acid at different pH values.

[0089] 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=2) solution containing 0.05 mol / L gallic acid.

[0090] Figure 11 Cyclic voltammetry curves of the electrochemical sensor prepared in Example 7 in 0.1 mol / L PBS solution (pH=2) containing gallic acid and 0.1 mol / L PBS solution (pH=2) without gallic acid.

[0091] Figure 12 The graph shows the anti-interference test results of the electrochemical sensor prepared in Example 7 of this invention for detecting gallic acid.

[0092] Figure 13 The graph shows the reproducibility test results of the electrochemical sensor obtained in Example 7 of this invention for detecting gallic acid current.

[0093] Figure 14 The figure shows the stability test results of the electrochemical sensor prepared in Example 7 of this invention for detecting gallic acid.

[0094] 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 square root of the corresponding concentration for detecting different concentrations of gallic acid using the electrochemical sensor prepared in Example 7 (b). Detailed Implementation

[0095] 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.

[0096] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. In this invention, the singular forms “a,” “the,” and “the” as used in the embodiments and appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0097] In this embodiment of the invention, a method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material includes the following steps:

[0098] S1. Preparation of mesoporous MEL molecular sieve: Tetraethyl orthosilicate, aluminum sulfate octadecylhydrate and tetrabutylammonium hydroxide are mixed in water to obtain aluminosilicate gel, which is then heated and reacted. After filtration, washing, drying and calcination, mesoporous MEL molecular sieve is obtained.

[0099] S2. Silver-modified mesoporous MEL molecular sieve: The mesoporous MEL molecular sieve is subjected to an ion exchange reaction with a silver ion solution, and then the precipitate is collected, dried and calcined to obtain a mesoporous Ag-MEL molecular sieve, which is the silver-modified mesoporous MEL molecular sieve.

[0100] S3, MXene doping: The mesoporous Ag-MEL molecular sieve and MXene are added to a chitosan solution, stirred and reacted, then centrifuged, the precipitate is collected, washed and dried to obtain the composite material MXene@Ag-MEL, that is, the MXene-doped silver-modified mesoporous MEL molecular sieve composite material is prepared.

[0101] In some embodiments, in step S1, the molar ratio of tetraethyl orthosilicate, aluminum sulfate octadecyl hydrate, tetrabutylammonium hydroxide, and water is (200~600):(0.1~3):(50~300):(200~700); and / or

[0102] The mixing method is magnetic stirring, the temperature of the magnetic stirring is 20℃~40℃, and the stirring time is 4h~6h; and / or

[0103] The heating reaction temperature is 150℃~190℃, and the heating reaction time is 24h~48h; and / or

[0104] The drying temperature is 120℃~150℃, and the drying time is 4h~6h; and / or

[0105] The calcination temperature is 500℃~600℃, and the calcination time is 4h~5h; and / or

[0106] The washing process involves using deionized water.

[0107] In some embodiments, in step S2, the concentration of the silver ion solution is 0.001 mol / L to 0.1 mol / L; and / or

[0108] The mass-to-volume ratio of the mesoporous MEL molecular sieve to the silver ion solution is 1 g: (15~25) mL; and / or

[0109] The silver ion solution is at least one of silver nitrate solution and silver acetate solution; and / or

[0110] The temperature for the ion exchange reaction between the mesoporous MEL molecular sieve and the silver ion solution is 40℃~80℃, and the reaction time is 6h~16h; and / or

[0111] The drying temperature is 60℃~100℃, and the drying time is 8h~16h; and / or

[0112] The calcination temperature is 500℃~600℃, and the calcination time is 5h~6h.

[0113] In some embodiments, in step S3, the MXene is prepared by: etching LiF powder with acid, adding Ti3AlC2 powder, stirring, centrifuging, washing, and ultrasonic treatment, collecting the product, and drying it to obtain Ti3C2T. x That is, the MXene is obtained.

[0114] In some embodiments, in step S3, the mass ratio of the mesoporous Ag-MEL molecular sieve to MXene is (0.1~3):(0.1~5); and / or

[0115] The mass ratio of the chitosan solution to the mesoporous Ag-MEL molecular sieve is 1:(4~6); and / or

[0116] The concentration of the chitosan solution is 0.05wt%~0.2wt%; and / or

[0117] The temperature of the stirring reaction is 25℃~40℃, and the stirring reaction time is 4h~6h; and / or

[0118] The drying temperature is 40℃~60℃, and the drying time is 10h~14h; and / or

[0119] The washing process involves using anhydrous ethanol.

[0120] In this embodiment of the invention, an MXene-doped silver-modified mesoporous MEL molecular sieve composite material is prepared by the aforementioned method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material.

[0121] In this embodiment of the invention, an electrochemical sensor is prepared from the aforementioned MXene-doped silver-modified mesoporous MEL molecular sieve composite material.

[0122] In this embodiment of the invention, a method for preparing an electrochemical sensor includes the following steps:

[0123] S1. Disperse the MXene-doped silver-modified mesoporous MEL molecular sieve composite material as described in claim 6 in a solvent to obtain a molecular sieve composite material suspension;

[0124] 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.

[0125] In some embodiments, in step S1, the concentration of the molecular sieve composite material suspension is 5 mg / mL to 20 mg / mL; and / or

[0126] In step S1, the solvent is a chitosan solution; the concentration of the chitosan solution is 0.4 wt% to 0.6 wt%; and / or

[0127] In step S1, the dispersion is achieved by ultrasonic treatment for 50-70 minutes; and / or

[0128] In step S2, the volume of the molecular sieve composite material suspension drop-coated onto the screen-printed electrode is 4 μL to 6 μL; and / or

[0129] In step S2, the drying method is natural air drying at room temperature.

[0130] In this embodiment of the invention, an electrochemical sensor is applied, specifically the electrochemical sensor prepared by the method described above, in the detection of gallic acid content.

[0131] The following description is based on specific embodiments.

[0132] Example 1

[0133] A method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material includes the following steps:

[0134] S1. Preparation of mesoporous MEL molecular sieve: Tetraethyl orthosilicate, aluminum sulfate octadecyl hydrate, and tetrabutylammonium hydroxide were mixed in water at 25°C with magnetic stirring for 4 hours to obtain an aluminosilicate gel. The gel was then heated at 170°C for 36 hours, filtered, washed with deionized water, dried at 120°C for 6 hours, and calcined at 600°C for 4 hours to obtain a mesoporous MEL molecular sieve. In this embodiment, the molar ratio of tetraethyl orthosilicate, aluminum sulfate octadecyl hydrate, tetrabutylammonium hydroxide, and water was 400:1:160:420.

[0135] S2. Silver-modified mesoporous MEL molecular sieve: The mesoporous MEL molecular sieve was subjected to an ion exchange reaction with 0.01 mol / L silver nitrate solution at 80°C for 12 h. The precipitate was then collected, dried at 80°C for 12 h, and calcined at 550°C for 6 h to obtain a mesoporous Ag-MEL molecular sieve, which is a silver-modified mesoporous MEL molecular sieve. In this embodiment, the mass-to-volume ratio of the mesoporous MEL molecular sieve to the silver ion solution was 1 g: 20 mL.

[0136] S3, MXene doping: Mesoporous Ag-MEL molecular sieve and MXene were added to a 0.1 wt% chitosan solution and stirred at 25°C for 6 h. The mixture was then centrifuged, the precipitate was collected, washed with anhydrous ethanol, and dried at 50°C for 12 h to obtain the composite material MXene@Ag-MEL, thus preparing the MXene-doped silver-modified mesoporous MEL molecular sieve composite material. In this embodiment, the mass ratio of mesoporous Ag-MEL molecular sieve to MXene was 1:1; the mass ratio of chitosan solution to mesoporous Ag-MEL molecular sieve was 1:5.

[0137] The preparation method of MXene is as follows: 2g of LiF powder was added to 40mL of 6M HCl for acid etching for 30min, then 2g of Ti3AlC2 powder was added. After magnetic stirring at 40℃ for 36h, centrifugation was performed, the product was washed with deionized water and collected, the product was ultrasonically treated in deionized water for 30min, the supernatant was collected, and the solution was vacuum dried at 80℃ for 24h to obtain Ti3C2T. x That is, MXene is obtained.

[0138] Example 2

[0139] A method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material includes the following steps:

[0140] S1. Preparation of mesoporous MEL molecular sieve: Tetraethyl orthosilicate, aluminum sulfate octadecyl hydrate, and tetrabutylammonium hydroxide were mixed in water at 20°C with magnetic stirring for 6 hours to obtain an aluminosilicate gel. The gel was then heated at 150°C for 48 hours, filtered, washed with deionized water, dried at 120°C for 6 hours, and calcined at 500°C for 5 hours to obtain a mesoporous MEL molecular sieve. In this embodiment, the molar ratio of tetraethyl orthosilicate, aluminum sulfate octadecyl hydrate, tetrabutylammonium hydroxide, and water was 400:1:120:420.

[0141] S2. Silver-modified mesoporous MEL molecular sieve: The mesoporous MEL molecular sieve was subjected to an ion exchange reaction with a 0.001 mol / L silver nitroacetate solution at 40°C for 16 h. The precipitate was then collected, dried at 60°C for 16 h, and calcined at 500°C for 6 h to obtain a mesoporous Ag-MEL molecular sieve, which is a silver-modified mesoporous MEL molecular sieve. In this embodiment, the mass-to-volume ratio of the mesoporous MEL molecular sieve to the silver ion solution was 1 g: 15 mL.

[0142] S3, MXene doping: Mesoporous Ag-MEL molecular sieve and MXene were added to a 0.05 wt% chitosan solution and stirred at 25 °C for 6 h. The mixture was then centrifuged, the precipitate was collected, washed with anhydrous ethanol, and dried at 40 °C for 14 h to obtain the composite material MXene@Ag-MEL, i.e., the MXene-doped silver-modified mesoporous MEL molecular sieve composite material was prepared. In this embodiment, the mass ratio of mesoporous Ag-MEL molecular sieve to MXene was 0.1:0.5; the mass ratio of chitosan solution to mesoporous Ag-MEL molecular sieve was 1:4.

[0143] The preparation method of MXene is as follows: 2g of LiF powder was added to 40mL of 6M HCl for acid etching for 30min, then 2g of Ti3AlC2 powder was added. After magnetic stirring at 40℃ for 36h, centrifugation was performed, the product was washed with deionized water and collected, the product was ultrasonically treated in deionized water for 30min, the supernatant was collected, and the solution was vacuum dried at 80℃ for 24h to obtain Ti3C2T. x That is, MXene is obtained.

[0144] Example 3

[0145] A method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material includes the following steps:

[0146] S1. Preparation of mesoporous MEL molecular sieve: Tetraethyl orthosilicate, aluminum sulfate octadecylhydrate, and tetrabutylammonium hydroxide were mixed in water at 40°C with magnetic stirring for 4 hours to obtain an aluminosilicate gel. The gel was then heated at 190°C for 24 hours, filtered, washed with deionized water, dried at 150°C for 4 hours, and calcined at 600°C for 4 hours to obtain the mesoporous MEL molecular sieve. In this embodiment, the molar ratio of tetraethyl orthosilicate, aluminum sulfate octadecylhydrate, tetrabutylammonium hydroxide, and water was 300:1:160:420.

[0147] S2. Silver-modified mesoporous MEL molecular sieve: The mesoporous MEL molecular sieve was subjected to an ion exchange reaction with 0.1 mol / L silver nitrate solution at 80°C for 6 hours. The precipitate was then collected, dried at 100°C for 8 hours, and calcined at 600°C for 5 hours to obtain a mesoporous Ag-MEL molecular sieve, which is a silver-modified mesoporous MEL molecular sieve. In this embodiment, the mass-to-volume ratio of the mesoporous MEL molecular sieve to the silver ion solution was 1 g: 25 mL.

[0148] S3, MXene doping: Mesoporous Ag-MEL molecular sieve and MXene were added to a 0.2 wt% chitosan solution and stirred at 40°C for 4 h. The mixture was then centrifuged, the precipitate was collected, washed with anhydrous ethanol, and dried at 60°C for 10 h to obtain the composite material MXene@Ag-MEL, thus preparing the MXene-doped silver-modified mesoporous MEL molecular sieve composite material. In this embodiment, the mass ratio of mesoporous Ag-MEL molecular sieve to MXene was 3:5; the mass ratio of chitosan solution to mesoporous Ag-MEL molecular sieve was 1:6.

[0149] The preparation method of MXene is as follows: 2g of LiF powder was added to 40mL of 6M HCl for acid etching for 30min, then 2g of Ti3AlC2 powder was added. After magnetic stirring at 40℃ for 36h, centrifugation was performed, the product was washed with deionized water and collected, the product was ultrasonically treated in deionized water for 30min, the supernatant was collected, and the solution was vacuum dried at 80℃ for 24h to obtain Ti3C2T. x That is, MXene is obtained.

[0150] Example 4

[0151] A method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material includes the following steps:

[0152] S1. Preparation of mesoporous MEL molecular sieve: Tetraethyl orthosilicate, aluminum sulfate octadecyl hydrate, and tetrabutylammonium hydroxide were mixed in water at 30°C with magnetic stirring for 5 hours to obtain an aluminosilicate gel. The gel was then heated at 160°C for 40 hours, filtered, washed with deionized water, dried at 130°C for 5.5 hours, and calcined at 550°C for 4.5 hours to obtain the mesoporous MEL molecular sieve. In this embodiment, the molar ratio of tetraethyl orthosilicate, aluminum sulfate octadecyl hydrate, tetrabutylammonium hydroxide, and water was 200:0.1:50:200.

[0153] S2. Silver-modified mesoporous MEL molecular sieve: The mesoporous MEL molecular sieve was subjected to an ion exchange reaction with 0.05 mol / L silver nitrate solution at 50°C for 10 h. The precipitate was then collected, dried at 70°C for 13 h, and calcined at 550°C for 5.5 h to obtain a mesoporous Ag-MEL molecular sieve, which is a silver-modified mesoporous MEL molecular sieve. In this embodiment, the mass-to-volume ratio of the mesoporous MEL molecular sieve to the silver ion solution was 1 g: 18 mL.

[0154] S3, MXene doping: Mesoporous Ag-MEL molecular sieve and MXene were added to a 0.08 wt% chitosan solution and stirred at 30°C for 5 h. The mixture was then centrifuged, the precipitate was collected, washed with anhydrous ethanol, and dried at 50°C for 13 h to obtain the composite material MXene@Ag-MEL, i.e., the MXene-doped silver-modified mesoporous MEL molecular sieve composite material was prepared. In this embodiment, the mass ratio of mesoporous Ag-MEL molecular sieve to MXene was 2:3; the mass ratio of chitosan solution to mesoporous Ag-MEL molecular sieve was 1:4.5.

[0155] The preparation method of MXene is as follows: 2g of LiF powder was added to 40mL of 6M HCl for acid etching for 30min, then 2g of Ti3AlC2 powder was added. After magnetic stirring at 40℃ for 36h, centrifugation was performed, the product was washed with deionized water and collected, the product was ultrasonically treated in deionized water for 30min, the supernatant was collected, and the solution was vacuum dried at 80℃ for 24h to obtain Ti3C2T. x That is, MXene is obtained.

[0156] Example 5

[0157] A method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material includes the following steps:

[0158] S1. Preparation of mesoporous MEL molecular sieve: Tetraethyl orthosilicate, aluminum sulfate octadecyl hydrate, and tetrabutylammonium hydroxide were mixed in water with magnetic stirring at 35°C for 4.5 h to obtain aluminosilicate gel. The gel was then heated at 180°C for 30 h, filtered, washed with deionized water, dried at 140°C for 4.5 h, and calcined at 530°C for 4.8 h to obtain mesoporous MEL molecular sieve. In this embodiment, the molar ratio of tetraethyl orthosilicate, aluminum sulfate octadecyl hydrate, tetrabutylammonium hydroxide, and water was 600:3:300:700.

[0159] S2. Silver-modified mesoporous MEL molecular sieve: The mesoporous MEL molecular sieve was subjected to an ion exchange reaction with a 0.07 mol / L silver acetate solution at 70°C for 8 hours. The precipitate was then collected, dried at 90°C for 9 hours, and calcined at 580°C for 5.3 hours to obtain a mesoporous Ag-MEL molecular sieve, which is a silver-modified mesoporous MEL molecular sieve. In this embodiment, the mass-to-volume ratio of the mesoporous MEL molecular sieve to the silver ion solution was 1 g: 22 mL.

[0160] S3, MXene doping: Mesoporous Ag-MEL molecular sieve and MXene were added to a 0.15 wt% chitosan solution and stirred at 35 °C for 4.5 h. The mixture was then centrifuged, the precipitate was collected, washed with anhydrous ethanol, and dried at 55 °C for 11 h to obtain the composite material MXene@Ag-MEL, i.e., the MXene-doped silver-modified mesoporous MEL molecular sieve composite material was prepared. In this embodiment, the mass ratio of mesoporous Ag-MEL molecular sieve to MXene was 2:1; the mass ratio of chitosan solution to mesoporous Ag-MEL molecular sieve was 1:5.5.

[0161] The preparation method of MXene is as follows: 2g of LiF powder was added to 40mL of 6M HCl for acid etching for 30min, then 2g of Ti3AlC2 powder was added. After magnetic stirring at 40℃ for 36h, centrifugation was performed, the product was washed with deionized water and collected, the product was ultrasonically treated in deionized water for 30min, the supernatant was collected, and the solution was vacuum dried at 80℃ for 24h to obtain Ti3C2T. x That is, MXene is obtained.

[0162] Example 6

[0163] An electrochemical sensor is prepared from an MXene-doped silver-modified mesoporous MEL molecular sieve composite material obtained in Examples 1 to 5.

[0164] Example 7

[0165] A method for preparing an electrochemical sensor includes the following steps:

[0166] S1. The MXene-doped silver-modified mesoporous MEL molecular sieve composite material of Example 1 was dispersed in a 0.5 wt% chitosan solution and ultrasonically treated for 60 min to obtain a molecular sieve composite material suspension; in this example, the concentration of the molecular sieve composite material suspension was 10 mg / mL.

[0167] S2. After drop-coating 5 μL of 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.

[0168] In this embodiment, the electrochemical sensor was tested by cyclic voltammetry in a 0.1 mol / L PBS solution (pH=2) containing 0.01 mol / L gallic acid, and the detection current was 61.08 μA. Therefore, this demonstrates that the electrochemical sensor prepared in this invention has electrochemical responsiveness to the detection of gallic acid, and the optimal detection conditions can be determined by the current values ​​detected under different conditions.

[0169] Example 8

[0170] A method for preparing an electrochemical sensor includes the following steps:

[0171] S1. The MXene-doped silver-modified mesoporous MEL molecular sieve composite material of Example 1 was dispersed in a 0.4 wt% chitosan solution and ultrasonically treated for 50 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.

[0172] S2. After drop-coating 4 μL of 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.

[0173] In this embodiment, the electrochemical sensor was tested by cyclic voltammetry in a 0.1 mol / L PBS solution (pH=2) containing 0.01 mol / L gallic acid, and the detection current was 51.04 μA.

[0174] Example 9

[0175] A method for preparing an electrochemical sensor includes the following steps:

[0176] S1. The MXene-doped silver-modified mesoporous MEL molecular sieve composite material of Example 1 was dispersed in a 0.6 wt% chitosan solution and ultrasonically treated for 70 min to obtain a molecular sieve composite material suspension; in this example, the concentration of the molecular sieve composite material suspension was 20 mg / mL.

[0177] S2. After drop-coating 6 μL of 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.

[0178] In this embodiment, the electrochemical sensor was tested by cyclic voltammetry in a 0.1 mol / L PBS solution (pH=2) containing 0.01 mol / L gallic acid, and the detection current was 50.62 μA.

[0179] Example 10

[0180] Application of an electrochemical sensor: The application of any one of the electrochemical sensors obtained in Examples 6 to 9 in the detection of gallic acid content.

[0181] Comparative Example 1

[0182] A method for preparing an electrochemical sensor is described. The difference between this comparative example and Example 7 is that the amount of molecular sieve composite material suspension used for drop-coating onto the screen-printed electrode is 2 μL. The remaining preparation methods in this comparative example are the same as in Example 7.

[0183] Comparative Example 2

[0184] A method for preparing an electrochemical sensor is disclosed. The difference between this comparative example and Example 7 is that the amount of molecular sieve composite material suspension used for drop-coating onto the screen-printed electrode is 8 μL. The remaining preparation methods in this comparative example are the same as in Example 7.

[0185] Structural morphology characterization

[0186] (a) X-ray diffraction analysis

[0187] The mesoporous MEL molecular sieve (MEL), mesoporous Ag-MEL molecular sieve (Ag-MEL), MXene, and MXene@Ag-MEL prepared in Example 1 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 mesoporous Ag-MEL molecular sieve prepared by this invention was successfully synthesized. A distinct silver species diffraction peak at 2θ=44.28° can be observed in the Ag-MEL spectrum, indicating that Ag was successfully introduced into the mesoporous MEL molecular sieve. Furthermore, peaks of both MXene and MEL were observed simultaneously in the MXene@Ag-MEL composite material, indicating that the composite material was successfully prepared. No characteristic peaks of silver species were observed, possibly because the silver species are highly dispersed in MXene@Ag-MEL.

[0188] (II) Morphological characterization by scanning electron microscopy

[0189] The mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, MXene, and MXene@Ag-MEL prepared in Example 1 were characterized by morphology using scanning electron microscopy (SEM), as follows: Figure 2 As shown in the figure. The SEM images of mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, MXene, and MXene@Ag-MEL are shown in the figure. Figure 2 As shown in Figures a to d.

[0190] Depend on Figure 2 It is evident that the mesoporous MEL molecular sieve prepared in this invention exhibits a date-shaped nano-stacked structure, which remains essentially unchanged after the addition of Ag, confirming the stability of the mesoporous MEL molecular sieve framework structure. Furthermore, the overall shape of MXene is accordion-like, exhibiting a layered structure of nanosheets. Moreover, after combining the mesoporous Ag-MEL molecular sieve with MXene, it can be observed that Ag-MEL is dispersed around the MXene nanosheets, forming an MXene@Ag-MEL composite system.

[0191] (III) Morphological characterization by transmission electron microscopy

[0192] The mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, MXene, and MXene@Ag-MEL prepared in Example 1 were characterized by morphology using transmission electron microscopy (TEM). Figure 3 As shown in the figure. The TEM images of mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, MXene, and MXene@Ag-MEL are respectively shown in the figure. Figure 3 As shown in Figures a to d.

[0193] Depend on Figure 3 It can be seen that the mesoporous MEL molecular sieve and the mesoporous Ag-MEL molecular sieve prepared by this invention both exhibit blocky stacking morphologies with minimal variation, but the aggregation of silver nanoparticles in Ag-MEL is clearly visible. Furthermore, Figure 3 MXene in (c) is mainly composed of sheet-like stacks. Figure 3 In (d), MEL, Ag particles and MXene can be observed simultaneously, indicating that the MXene@Ag-MEL composite material was successfully synthesized.

[0194] (iv) Energy-dispersive X-ray spectroscopy analysis

[0195] The mesoporous Ag-MEL molecular sieve, MXene, and MXene@Ag-MEL prepared in Example 1 were subjected to energy-dispersive X-ray spectroscopy analysis, as follows: Figure 4 As shown in the figure. The energy-dispersive X-ray spectra of mesoporous Ag-MEL molecular sieve, MXene, and MXene@Ag-MEL are respectively shown in the figure. Figure 4As shown in Figures a to c.

[0196] Depend on Figure 4 It can be seen that the mesoporous Ag-MEL molecular sieve prepared by this invention is mainly composed of elements such as Ag, Si, Al, and O. Ag exhibits agglomeration, while the other elements are highly dispersed. Furthermore, from Figure 4 (b) and Figure 4 (c) It can be seen that there is no agglomeration in MXene and MXene@Ag-MEL composite materials, indicating that the elements are evenly dispersed.

[0197] (V) X-ray photoelectron spectroscopy full spectrum analysis

[0198] The mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, and MXene@Ag-MEL prepared in Example 1 were subjected to full-spectrum X-ray photoelectron spectroscopy analysis, as follows: Figure 5 As shown. Among them, Figure 5 (a) is the full scan spectrum. Figure 5 (b) is the high-resolution spectrum of Ag 3d. Figure 5 (c) is a high-resolution spectrum of Ti 2p.

[0199] Depend on Figure 5 (a) As can be seen, the mesoporous Ag-MEL molecular sieve prepared in this invention has an additional Ag 3d peak (368 eV) compared to the mesoporous MEL molecular sieve, indicating that Ag species were successfully introduced into the mesoporous MEL molecular sieve. Simultaneously, Ti 2p and C 1s were observed in the MXene@Ag-MEL spectrum, indicating that MXene and Ag-MEL were successfully composited. Figure 5 (b) It can be seen that both Ag-MEL and MXene@Ag-MEL composite materials contain Ag 3d 3 / 2 and Ag 3d 5 / 2 However, the introduction of MXene lowers the binding energy due to a charge compensation effect, causing the π electrons of MXene to migrate to empty Ag orbitals. Furthermore, due to... Figure 5 (c) It can be seen that the MXene@Ag-MEL composite material also contains Ti 2p 1 / 2 and Ti 2p 3 / 2 Among them, Ti species mainly exist in the tetravalent form.

[0200] (vi) Analysis of nitrogen adsorption-desorption isotherms and BJH pore size distribution

[0201] The mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, and MXene@Ag-MEL prepared in Example 1 were subjected to nitrogen adsorption-desorption isotherm and BJH pore size distribution analysis, respectively. Figure 6 As shown. Figure 6In the diagram, a represents mesoporous MEL molecular sieve, b represents mesoporous Ag-MEL molecular sieve, and c represents MXene@Ag-MEL.

[0202] Depend on Figure 6 (a) It can be seen that the nitrogen adsorption-desorption isotherms of the mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, and MXene@Ag-MEL prepared in this invention exhibit hysteresis loops when P / P0>0.5, indicating that all three materials prepared have mesoporous structures. Furthermore, from... Figure 6 (b) It can be observed that mesoporous MEL molecular sieves, mesoporous Ag-MEL molecular sieves, and MXene@Ag-MEL all exhibit a narrow peak around 3.6 nm, indicating that the three materials have uniform mesopore sizes. Furthermore, based on the test results, the pore structure parameters were summarized, and the total specific surface area of ​​the mesoporous MEL molecular sieve reached 468.02 m². 2 / g, total pore volume is 0.35m 3 / g indicates that the mesoporous MEL molecular sieve has a high specific surface area and a large adsorption capacity, which in turn gives it highly exposed active sites, which is beneficial for the oxidation reaction.

[0203] Molecular sieve performance testing

[0204] (a) Specific surface area and pore volume detection of molecular sieves

[0205] The mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, and MXene@Ag-MEL prepared in Example 1 were tested for total specific surface area, mesoporous area, micropore area, total pore volume, micropore volume, and mesoporous pore volume, respectively. The test results are shown in Table 1.

[0206] Table 1. Results of specific surface area and pore volume measurements for MEL, Ag-MEL, and MXene@Ag-MEL.

[0207]

[0208] The total specific surface area was calculated using the Brunauer–Emmett–Teller (BET) method. The total pore volume was determined by the adsorption volume at P / P0 = 0.99. The micropore volume was determined by the t-plot method. Mesopore volume = Total pore volume. - Micropore volume.

[0209] As shown in Table 1, the specific surface area of ​​Ag-MEL molecular sieve is lower than that of MEL molecular sieve. This may be because the introduction of Ag species blocked some of the pores of the molecular sieve. The specific surface area of ​​MXene@Ag-MEL is only slightly lower than that of pure MEL molecular sieve. This slight decrease precisely proves that there is a close interfacial interaction between MXene and Ag-MEL materials. By sacrificing a little specific surface area, the conductivity is improved (based on the conductive pathway provided by MXene and silver species) and the sensing performance is significantly enhanced (based on the interaction between materials and the electronic effect at the interface).

[0210] (II) Detection of the electrocatalytic activity of molecular sieves

[0211] The mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, and MXene@Ag-MEL prepared in Example 1 were subjected to electrocatalytic activity testing, and the Q-square root relationship of the time-coulomb (CC) curves was obtained as follows: Figure 7 As shown.

[0212] Depend on Figure 7 As can be seen, the MXene@Ag-MEL modified electrode exhibits the largest coulomb value, indicating its superior electron transfer capability and electrocatalytic activity. The electroactive surface area of ​​the electrode was calculated according to the Cottrell equation, as shown in equations (1) and (2).

[0213]

[0214] 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 MXene@Ag-MEL (0.2455 cm²) and 0.2455 cm², respectively. 2 Ag-MEL (0.1191 cm) > Ag-MEL (0.1191 cm) 2 MEL (0.1127cm) 2 The results showed that the MXene@Ag-MEL composite material exhibited the best electrochemical response and electrocatalytic activity during the electrocatalytic process, and thus could be well applied to electrochemical sensors.

[0215] (III) Detection of the conductivity of molecular sieves

[0216] The electrical conductivity of the mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, and MXene@Ag-MEL prepared in Example 1 was directly measured using the four-probe method to quantitatively evaluate the electrical conductivity of the three materials. Among them, the mesoporous MEL molecular sieve exhibited the lowest electrical conductivity (7.38 × 10⁻⁶). -7 The conductivity of mesoporous Ag-MEL molecular sieves increased significantly to 2.01 × 10⁻⁶ S / cm, while that of silver species loaded onto the sieves increased significantly to 2.01 × 10⁻⁶ S / cm. -3 The conductivity of MXene@Ag-MEL is as high as 1.22 S / cm, while that of mesoporous MEL molecular sieve and mesoporous Ag-MEL molecular sieve is much higher. This shows that the composite material prepared by introducing silver and MXene in this invention significantly enhances the electron transfer of mesoporous MEL molecular sieve, and can be well applied to electrochemical sensors.

[0217] (iv) Mechanical strength testing of molecular sieves

[0218] The mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, and MXene@Ag-MEL prepared in Example 1 were subjected to abrasion tests to determine their mechanical strength. This is a key indicator for evaluating the molecular sieve sample's resistance 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. Fine powder generated during 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%.

[0219] Through experiments and calculations, the wear indices of the three samples—mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, and MXene@Ag-MEL—were obtained to be 0.2% / hour, 0.2% / hour, and 0.4% / 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 mesoporous MEL molecular sieve, mesoporous Ag-MEL molecular sieve, and MXene@Ag-MEL prepared in this invention all possess excellent mechanical strength.

[0220] Therefore, the performance testing of the molecular sieve shows that the MXene-doped silver-modified mesoporous MEL molecular sieve composite material prepared in this invention has the advantages of high specific surface area, large pore volume, and excellent conductivity, electrochemical response, electrocatalytic activity, and mechanical strength. Therefore, it has a good application prospect in electrochemical sensors.

[0221] Performance testing of electrochemical sensors

[0222] (a) Cyclic voltammetry curves with different drop amounts

[0223] The electrochemical sensors prepared in Example 7 and Comparative Examples 1-2 were used to measure cyclic voltammetry curves in 0.1 mol / L PBS solution (pH=2) containing 0.01 mol / L gallic 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.

[0224] Depend on Figure 8 It can be seen that in Example 7, when the amount of molecular sieve composite material suspension dropped onto the screen-printed electrode is 5 μL, it exhibits excellent electrochemical responsiveness, resulting in good detection sensitivity and accuracy of the electrochemical sensor. In Comparative Example 2, the dropping amount is 8 μL. At this point, the excessive amount of molecular sieve composite material suspension leads to saturation of adsorption sites on the electrode, and may even clog active sites, thereby reducing the electrochemical response. In Comparative Example 1, the dropping amount is 2 μL. At this point, the insufficient amount of molecular sieve composite material suspension results in fewer adsorption sites on the electrode, weakening the adsorption and catalytic ability of gallic acid in the solution, thus reducing the detection sensitivity and accuracy of the electrochemical sensor.

[0225] (II) Optimization of gallic acid content detection conditions

[0226] 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 MXene / Ag / MEL / 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 gallic acid to investigate the effects of pH value and scan rate on the corresponding gallic acid current.

[0227] The electrochemical sensor prepared in Example 7 was placed in a 0.1 mol / PBS buffer solution containing 0.02 mol / L gallic acid under different pH conditions, and its cyclic voltammetry test curve is shown below. Figure 9 As shown.

[0228] Depend on Figure 9 It can be seen that during the oxidation of gallic acid, the separation of electrons and protons leads to the formation of its oxidation products. When the pH value decreases from 9 to 2, the oxidation potential increases significantly from 0.21V to 0.52V, and the peak oxidation current continuously increases, indicating that protons participate in the oxidation process of gallic acid. The results show that the oxidation peak of gallic acid reaches its maximum current response in 0.1 mol / L PBS (pH=2), meaning the optimal pH value for detection is 2.

[0229] The electrochemical sensor prepared in Example 7 was placed in a 0.1 mol / L PBS solution (pH=2) containing 0.05 mol / L gallic acid, and its cyclic voltammetry test curve is shown below. Figure 10 As shown.

[0230] Depend on Figure 10 It was observed that the anolyte current of gallic acid increased with the scan rate from 20 mV / s to 200 mV / s. Furthermore, the oxidation peak potential continuously shifted towards the positive direction, indicating that electron transfer was kinetically limited at higher scan rates, and that the process was an irreversible oxidation 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.

[0231] (III) Electrochemical performance testing of electrochemical sensors

[0232] The tests were conducted using a three-electrode system on an electrochemical workstation. The electrochemical sensor MXene / Ag / MEL / CS / SPE prepared in Example 7 was used as the working electrode, the Ag / AgCl electrode 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=2) containing gallic acid and in 0.1 mol / L PBS buffer solution (pH=2) without gallic 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 gallic acid, and curve b represents a PBS buffer solution without gallic acid.

[0233] Depend on Figure 11 It is known that in a blank electrolyte solution without gallic acid, the working electrode shows almost no oxidation peak. After adding a certain amount of gallic acid, the electrode exhibits a significant oxidation peak at a potential of 0.58 V, demonstrating good electrochemical performance and indicating that the reaction process is irreversible. Therefore, the electrochemical sensor prepared in this invention can be used for the detection of gallic acid content.

[0234] (iv) Selectivity testing of electrochemical sensors

[0235] 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 MXene / Ag / MEL / CS / SPE electrode. The Ag / AgCl electrode was used as the reference electrode, and the carbon electrode was used as the counter electrode. K+ with a concentration 50 times that of gallic acid was added to a 0.1 mol / L PBS buffer solution (pH=2) containing 0.01 mol / L gallic acid.+ Na + Zn 2+ Cl - Differential pulse voltammetry was used to test the electrochemical responsiveness of gallic acid solution with solutions containing lysine (Lys), glutamic acid (Glu), acetic acid (HAc), glucose (Glc), vitamin A (VA), tyrosine (Tyr), urea (UR), creatinine (CR), dopamine (DA), and ascorbic acid (AA) to compare the effects of these interfering substances on the electrochemical responsiveness of gallic acid solution, in order to verify the selectivity of the MXene / Ag / MEL / CS / SPE electrode. The test results are as follows: Figure 12 As shown.

[0236] Depend on Figure 12 It can be seen that the addition of these interfering substances has a very weak effect on the electrochemical responsiveness of gallic acid solution, and the change in oxidation current signal is small (<5%), indicating that the electrochemical sensor prepared by this invention has good anti-interference ability.

[0237] (v) Reproducibility testing of electrochemical sensors.

[0238] 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 MXene / Ag / MEL / CS / SPE electrode. The Ag / AgCl electrode was used as the reference electrode, and the carbon electrode was used as the counter electrode. In a 0.1 mol / L PBS buffer solution (pH=2) containing 0.01 mol / L gallic acid, the current in the gallic acid solution was measured multiple times at different times using the same MXene / Ag / MEL / CS / SPE electrode, and 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.

[0239] Depend on Figure 13 It can be seen that the difference in current values ​​among the eight measurements is small, indicating that the electrochemical sensor prepared in this invention has good reproducibility when used as a working electrode.

[0240] (vi) Stability testing of electrochemical sensors.

[0241] 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 MXene / Ag / MEL / CS / SPE electrode. The Ag / AgCl electrode was used as the reference electrode, and the carbon electrode was used as the counter electrode. 100 fragments were scanned at a scan rate of 100 mV / s in a 0.1 mol / L PBS buffer solution (pH=2) containing 0.05 mol / L gallic acid. The stability of the sensor was tested using cyclic voltammetry. The test results are as follows: Figure 14 As shown.

[0242] Depend on Figure 14 It can be seen that after multiple cyclic scans, the cyclic voltammetry curve of the electrochemical sensor remains basically unchanged, indicating that the electrochemical sensor prepared by the present invention has good stability.

[0243] (vii) Detection of gallic acid standard solutions of different concentrations.

[0244] 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 MXene / Ag / MEL / 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 gallic 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.

[0245] Depend on Figure 15 (a) It can be seen that in the potential range of 0.3~0.6V, when the concentration of gallic acid increases from 1μmol / L to 50000μmol / L, the peak current increases with the increase of the concentration of gallic acid. Figure 15 (b) shows the linear relationship between peak current and the square root of the corresponding concentration, R 2 =0.9995. The results show that the MXene / Ag / MEL / CS / SPE electrode achieved a wide detection range and an ultra-low detection limit, with a detection range of 1 μmol / L to 50000 μmol / L and a detection limit of 0.5 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.

[0246] 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 method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material, characterized in that, Includes the following steps: S1. Preparation of mesoporous MEL molecular sieve: Tetraethyl orthosilicate, aluminum sulfate octadecylhydrate and tetrabutylammonium hydroxide are mixed in water to obtain aluminosilicate gel, which is then heated and reacted. After filtration, washing, drying and calcination, mesoporous MEL molecular sieve is obtained. S2. Silver-modified mesoporous MEL molecular sieve: The mesoporous MEL molecular sieve is subjected to an ion exchange reaction with a silver ion solution, and then the precipitate is collected, dried and calcined to obtain a mesoporous Ag-MEL molecular sieve, which is the silver-modified mesoporous MEL molecular sieve. S3, MXene doping: The mesoporous Ag-MEL molecular sieve and MXene are added to a chitosan solution, stirred and reacted, then centrifuged, the precipitate is collected, washed and dried to obtain the composite material MXene@Ag-MEL, that is, the MXene-doped silver-modified mesoporous MEL molecular sieve composite material is prepared.

2. The method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material as described in claim 1, characterized in that, In step S1, the molar ratio of tetraethyl orthosilicate, aluminum sulfate octadecylhydrate, tetrabutylammonium hydroxide, and water is (200~600):(0.1~3):(50~300):(200~700); and / or The mixing method is magnetic stirring, the temperature of the magnetic stirring is 20℃~40℃, and the stirring time is 4h~6h; and / or The heating reaction temperature is 150℃~190℃, and the heating reaction time is 24h~48h; and / or The drying temperature is 120℃~150℃, and the drying time is 4h~6h; and / or The calcination temperature is 500℃~600℃, and the calcination time is 4h~5h; and / or The washing process involves using deionized water.

3. The method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material as described in claim 1, characterized in that, In step S2, the concentration of the silver ion solution is 0.001 mol / L to 0.1 mol / L; and / or The mass-to-volume ratio of the mesoporous MEL molecular sieve to the silver ion solution is 1 g: (15~25) mL; and / or The silver ion solution is at least one of silver nitrate solution and silver acetate solution; and / or The temperature for the ion exchange reaction between the mesoporous MEL molecular sieve and the silver ion solution is 40℃~80℃, and the reaction time is 6h~16h; and / or The drying temperature is 60℃~100℃, and the drying time is 8h~16h; and / or The calcination temperature is 500℃~600℃, and the calcination time is 5h~6h.

4. The method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material as described in claim 1, characterized in that, In step S3, the MXene is prepared as follows: LiF powder is etched with acid, then Ti3AlC2 powder is added. After stirring, centrifugation, washing, and ultrasonic treatment, the product is collected and dried to obtain Ti3C2T. x That is, the MXene is obtained.

5. The method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material as described in claim 1, characterized in that, In step S3, the mass ratio of the mesoporous Ag-MEL molecular sieve to MXene is (0.1~3):(0.1~5); and / or The mass ratio of the chitosan solution to the mesoporous Ag-MEL molecular sieve is 1:(4~6); and / or The concentration of the chitosan solution is 0.05wt%~0.2wt%; and / or The temperature of the stirring reaction is 25℃~40℃, and the stirring reaction time is 4h~6h; and / or The drying temperature is 40℃~60℃, and the drying time is 10h~14h; and / or The washing process involves using anhydrous ethanol.

6. A silver-doped MXene-modified mesoporous MEL molecular sieve composite material, characterized in that, It is prepared by the method for preparing an MXene-doped silver-modified mesoporous MEL molecular sieve composite material according to any one of claims 1 to 5.

7. An electrochemical sensor, characterized in that, It is prepared from the MXene-doped silver-modified mesoporous MEL molecular sieve composite material as described in claim 6.

8. The method for preparing an electrochemical sensor according to claim 7, characterized in that, Includes the following steps: S1. Disperse the MXene-doped silver-modified mesoporous MEL molecular sieve composite material as described in claim 6 in a solvent to obtain a molecular sieve composite material suspension; 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.

9. The method for preparing an electrochemical sensor as described in claim 8, characterized in that, In step S1, the concentration of the molecular sieve composite material suspension is 5 mg / mL to 20 mg / mL; and / or In step S1, the solvent is a chitosan solution; the concentration of the chitosan solution is 0.4 wt% to 0.6 wt%; and / or In step S1, the dispersion is achieved by ultrasonic treatment for 50-70 minutes; and / or In step S2, the volume of the molecular sieve composite material suspension drop-coated onto the screen-printed electrode is 4 μL to 6 μL; and / or In step S2, the drying method is natural air drying at room temperature.

10. An application of an electrochemical sensor, characterized in that, The application of an electrochemical sensor prepared by the method of claim 7 or any one of claims 8 to 9 in detecting gallic acid content.

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