1,2,4-trichlorobenzene on-line detection material and preparation method thereof

Abstract

This invention relates to the field of online detection in materials chemistry, specifically an online detection material for 1,2,4-trichlorobenzene and its preparation method. It provides a film-forming sensitive layer material that can be coated onto the surface of a transducer. After drying, it comprises chitosan, a crosslinking component (calculated as 0.1–5 wt% of glutaraldehyde), and magnetic core-shell molecularly imprinted particles. The magnetic core-shell molecularly imprinted particles contain a magnetite magnetic core, a silica intermediate layer, and a molecularly imprinted polymer shell. The shell is a copolymer network of cyclodextrin methacrylate and ethylene glycol dimethacrylate, using 1,2,4-trichlorobenzene as a template. The material maintains membrane integrity and long-term stability while ensuring rapid response under circulation and regeneration conditions, and controls residual 1,2,4-trichlorobenzene to no more than 0.10 wt% and residual glutaraldehyde to no more than 0.5 wt%. This material alleviates structural mass transfer contradictions and the coupling contradiction between processing and coating caused by high filler loading, and has value for online detection applications.

Description

Technical Field

[0001] This invention relates to the field of online detection materials, specifically to an online detection material for 1,2,4-trichlorobenzene and its preparation method. Background Technology

[0002] For online detection of 1,2,4-trichlorobenzene, the online detection material needs to be able to operate for extended periods under both circulation and regeneration conditions, and can be coated onto the transducer surface to form a stable film-forming sensitive layer. This film-forming sensitive layer material should maintain film integrity and long-term stability during curing, washing, and reuse, avoiding detachment, cracking, or uneven thickness on the transducer substrate surface, which would affect response repeatability. Meanwhile, online detection materials typically consist of chitosan, crosslinking components based on glutaraldehyde, and magnetic core-shell molecularly imprinted particles. Different components have coupled effects on the dry film structure during film formation, crosslinking, compounding, and post-treatment; a lack of proper matching can easily lead to a narrowing of the processing window and decreased coating consistency under high filler loads. On the other hand, the molecularly imprinted polymer shell needs to maintain the stability of the template molecule's related structure while ensuring unobstructed mass transfer channels, thus imposing comprehensive requirements on the preparation route, elution strategy, and residue control. Furthermore, improper washing and drying control can lead to residual glutaraldehyde or residual 1,2,4-trichlorobenzene causing background interference and affecting reuse.

[0003] In existing technologies, core-shell structures with a magnetic core and a silica interlayer have been used to prepare magnetic materials and surface-modified materials. For example, Chinese patent CN104759260B discloses an amino-functionalized magnetic silica-iron oxide composite nanomaterial and its preparation method, demonstrating a feasible path for the interface bonding between the magnetic core and silica. Meanwhile, Chinese patent CN115926048B discloses a method for preparing magnetic molecularly imprinted polymers, showcasing the idea of ​​constructing a molecularly imprinted polymer layer on the surface of magnetic particles. However, when applied to online detection materials, these approaches often face multiple constraints: on the one hand, the degree of crosslinking and shell thickness of the molecularly imprinted polymer layer need to balance selectivity and mass transfer rate; excessive density will reduce rapid response capability. On the other hand, high filler loading and film formation processes easily introduce intra-film stress and interface defects, leading to insufficient membrane integrity and long-term stability under flow and regeneration conditions. Furthermore, improper elution and low-residue control may damage the microstructure of the molecularly imprinted polymer shell and shorten its reusable lifespan. Therefore, systematic optimization of synergistic components and process windows is still necessary. Summary of the Invention

[0004] The purpose of this invention is to provide an online detection material for 1,2,4-trichlorobenzene and its preparation method, which solves the structure-mass transfer contradiction between the requirements for membrane integrity and long-term stability of the sensitive layer under circulation and regeneration conditions and the high sensitivity and high selectivity required for molecular imprint recognition, as well as the coupling contradiction between the processing window and coating consistency pressure brought about by high filler loading and the requirements for online rapid response and rapid regeneration, and further alleviates the natural conflict between strict template removal and low residue control and imprint site structure maintenance and cycle life.

[0005] This invention uses chitosan as the film-forming framework and glutaraldehyde for cross-linking and curing. At the same time, it introduces magnetic core-shell molecularly imprinted particles as functional components. The magnetic core of iron oxide and the intermediate layer of silica provide a stable carrier. The molecularly imprinted polymer shell provides a specific effect on 1,2,4-trichlorobenzene. Through the synergistic matching of film-forming cross-linking and core-shell particle interface, it balances membrane integrity, mass transfer and regeneration availability under high filler load.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An online detection material for 1,2,4-trichlorobenzene, wherein the online detection material is a film-forming sensitive layer material that can be coated on the surface of a transducer, and comprises, by total mass after drying:

[0008] Chitosan 20–80 wt%

[0009] The content, calculated as glutaraldehyde, is 0.1–5 wt%;

[0010] The magnetic core-shell molecularly imprinted particles comprise 15–75 wt%, and the sum of the mass fractions of the above three components does not exceed 100 wt%.

[0011] The magnetic core-shell molecularly imprinted particles comprise a magnetic core, a silica intermediate layer, and a molecularly imprinted polymer shell; the magnetic core is iron(III) oxide; the silica intermediate layer is silica; the molecularly imprinted polymer shell comprises a polymer network formed by copolymerization of cyclodextrin methacrylate and ethylene glycol dimethacrylate; the cyclodextrin methacrylate is β-cyclodextrin methacrylate or γ-cyclodextrin methacrylate, and the degree of substitution (DS) of the cyclodextrin methacrylate is 0.05–0.30.

[0012] Furthermore, the cyclodextrin methacrylate is prepared by the following steps:

[0013] A1. Raw material preparation: Dissolve β-cyclodextrin or γ-cyclodextrin in dimethyl sulfoxide to make the cyclodextrin mass fraction 5–20 wt%; add potassium carbonate, the amount of which is 0.05–0.50 times the molar amount of cyclodextrin;

[0014] A2. Reaction: Under a nitrogen inert atmosphere, glycidyl methacrylate containing p-methoxyphenol polymerization inhibitor is added dropwise to the solution at a rate of 1–5 mL / min, so that the molar ratio of glycidyl methacrylate to cyclodextrin is 0.2:1–2.0:1, and the reaction is carried out at 40–70 °C for 6–24 h.

[0015] A3. Post-treatment: After filtering the reaction solution to remove inorganic salts, add ethanol as a precipitant to precipitate the product. The mass ratio of ethanol to reaction solution is 3:1–20:1. The precipitate is washed with ethanol 1–5 times and dried at 40–60℃ for 6–24 h.

[0016] A4. Endpoint Criteria and Quality Control: The degree of substitution (DS) of the obtained cyclodextrin methacrylate is 0.05–0.30, and the residual dimethyl sulfoxide is not greater than 1.0 wt%.

[0017] Furthermore, the magnetic silica silanized particles used to prepare the magnetic core-shell molecularly imprinted particles are prepared through the following steps:

[0018] B1. Preparation of magnetic cores: Ferric chloride hexahydrate and ferrous chloride tetrahydrate were dissolved in deionized water to make the molar ratio of ferric to ferrous iron 1.8:1–2.2:1 and the total concentration of iron salts 0.1–0.5 mol / L; the temperature was raised to 60–85 °C under a nitrogen inert atmosphere, and ammonium hydroxide solution was added dropwise to adjust the pH to 9–11. The reaction was maintained at this temperature for 0.5–2 h; the resulting magnetic particles were magnetically separated and washed with deionized water until the pH of the washing solution was 7–8.

[0019] B2. Silica Coating: The magnetic particles obtained in B1 are dispersed at a concentration of 2–20 mg / mL in a mixed solvent of ethanol and deionized water, wherein the volume ratio of ethanol to deionized water is 3:1–10:1; ammonium hydroxide solution is added to adjust the pH to 9–11, and tetraethyl silicate is added. The mixture is reacted at 20–40 °C for 4–24 h to obtain silica-coated magnetic particles.

[0020] B3. Silanization: The particles obtained in B2 are dispersed at a concentration of 10–50 mg / mL in ethanol containing 1–5% deionized water by volume. 3-Methacryloxypropyltrimethoxysilane and 3-aminopropyltriethoxysilane are added, with the total amount of the two being 1–10 wt% of the particle mass, and the mass ratio of 3-methacryloxypropyltrimethoxysilane to 3-aminopropyltriethoxysilane being 1:9–9:1. The reaction is carried out at 25–60 °C for 1–8 h.

[0021] B4. Endpoint Criteria and Quality Control: The D50 of the obtained magnetic silica silanized particles is 80–240 nm, and the magnetic response time is not greater than 30 s.

[0022] Furthermore, the magnetic core-shell molecularly imprinted particles are prepared through the following steps:

[0023] C1. Preparation of prepolymer solution: 1,2,4-trichlorobenzene was added to ethanol as a template molecule, along with cyclodextrin methacrylate and ethylene glycol dimethacrylate, so that the mass ratio of cyclodextrin methacrylate to ethylene glycol dimethacrylate was 1:2–1:20, and the total mass ratio of 1,2,4-trichlorobenzene to cyclodextrin methacrylate and ethylene glycol dimethacrylate was 0.01:1–0.5:1; the total mass fraction of cyclodextrin methacrylate and ethylene glycol dimethacrylate in ethanol was 1–30 wt%; after mixing, the components were stirred and pre-incubated at room temperature for 1–2 h.

[0024] C2. Surface polymerization: Magnetic silica silanized particles are added to the prepolymer solution described in C1, such that the mass ratio of the magnetic silica silanized particles to the total mass of cyclodextrin methacrylate and ethylene glycol dimethacrylate in C1 is 0.2:1–5:1. Azobisisobutyronitrile is added as an initiator, such that the amount of initiator is 0.2–2 wt% of the total mass of cyclodextrin methacrylate and ethylene glycol dimethacrylate in C1. The reaction is carried out at 55–70 °C for 6–24 h under a nitrogen inert atmosphere to obtain core-shell particles containing template molecules.

[0025] C3. Elution and post-treatment: Wash and elute the template molecules with ethanol 3–10 times until no more than 0.10 wt% of 1,2,4-trichlorobenzene remains in the particles, and then dry to obtain magnetic core-shell molecularly imprinted particles;

[0026] C4. Quality control: The thickness of the molecularly imprinted polymer shell is 3–30 nm.

[0027] Furthermore, the film-forming sensitive layer material is prepared through the following steps:

[0028] D1. Film-forming solution: Dissolve chitosan in an aqueous solution containing glacial acetic acid, such that the mass fraction of glacial acetic acid is 0.5–2 wt% and the mass fraction of chitosan is 0.5–3 wt%, and stir until dissolved;

[0029] D2. Compounding: Add the magnetic core-shell molecularly imprinted particles prepared in step C, so that their mass fraction in the dry film is 15–75 wt%;

[0030] D3. Crosslinking film formation: Add glutaraldehyde aqueous solution to make the content of glutaraldehyde 0.1–5 wt%, coat the mixture on the surface of the transducer substrate and cure at 20–60 °C for 0.5–12 h;

[0031] D4. Post-treatment and quality control: After curing, wash with deionized water and ethanol in sequence and dry. The resulting dry film thickness is 1–100 μm and the residual glutaraldehyde is no more than 0.5 wt%.

[0032] Furthermore, the mass fraction of iron(III) oxide in the magnetic core-shell molecularly imprinted particles is 30–70 wt%, and the D50 of the magnetic core-shell molecularly imprinted particles is 100–250 nm.

[0033] As a concept of this invention, a continuous film-forming network is constructed using chitosan and crosslinking components based on glutaraldehyde, and magnetic core-shell molecularly imprinted particles are embedded in this network. This is primarily used to simultaneously improve the film integrity and long-term stability of the film-forming sensitive layer material under both circulation and regeneration conditions, while maintaining selective binding to 1,2,4-trichlorobenzene. Chitosan provides a coatable and film-forming basis, and crosslinking curing makes the dry film less prone to swelling or peeling under washing and reuse conditions. The silica interlayer of the magnetic core-shell molecularly imprinted particles helps improve the chemical environment of the particle surface and promotes interfacial compatibility with the film-forming system. The molecularly imprinted polymer shell, through structural units guided by template molecules, achieves the enrichment and differentiation of target molecules. By limiting particle size, shell thickness, residue control, and dry film thickness, this invention achieves a balance between processing window and coating consistency, thereby providing a repeatable sensitive layer basis for online detection.

[0034] This invention also discloses a method for preparing an online detection material for 1,2,4-trichlorobenzene, comprising the following steps:

[0035] S1. Provides cyclodextrin methacrylate;

[0036] S2. Provides magnetic silica silanized particles;

[0037] S3. Provides magnetic core-shell molecularly imprinted particles;

[0038] S4. Dissolve chitosan in an aqueous solution containing glacial acetic acid to obtain a film-forming solution;

[0039] S5. Add the magnetic core-shell molecularly imprinted particles to the film-forming solution, and add glutaraldehyde to crosslink and form a film, thereby obtaining 1,2,4-trichlorobenzene online detection material.

[0040] Furthermore, the degree of substitution (DS) of the cyclodextrin methacrylate provided in step S1 is 0.05–0.30, and the residual dimethyl sulfoxide is no more than 1.0 wt%.

[0041] Further, in step S4, the mass fraction of glacial acetic acid is 0.5–2 wt%, the mass fraction of chitosan is 0.5–3 wt%, and in step S5, the mass fraction of the magnetic core-shell molecularly imprinted particles in the dry film is 15–75 wt%, the content of glutaraldehyde is 0.1–5 wt%, the curing temperature is 20–60 ℃ and the curing time is 0.5–12 h, the thickness of the obtained dry film is 1–100 μm, and the residual glutaraldehyde is not greater than 0.5 wt%.

[0042] Furthermore, the molecularly imprinted polymer shell thickness of the magnetic core-shell molecularly imprinted particles provided in step S3 is 3–30 nm, and the residual 1,2,4-trichlorobenzene in the particles is no more than 0.10 wt%.

[0043] Furthermore, the chitosan used in the preparation of the online detection material has a degree of deacetylation of not less than 85% and a viscosity-average molecular weight of 100–500 kDa.

[0044] Furthermore, in step A2, the glycidyl methacrylate is added dropwise to the reaction system at a rate of 1–5 mL / min, and the glycidyl methacrylate used contains p-methoxyphenol polymerization inhibitor.

[0045] Furthermore, in step A3, the pore size of the filter medium used to remove inorganic salts is 0.22–0.45 μm; after adding ethanol, the mixture is allowed to stand at 0–4 °C for 0.5–2 h, and then centrifuged at 5000–8000 rpm for 10–15 min to collect the precipitate; the ethanol used for each wash is anhydrous ethanol, and the amount used is 5–20 mL / g of product.

[0046] Furthermore, in step A4, the degree of substitution DS is calculated as the average number of methacrylate groups on each cyclodextrin molecule.

[0047] Further, in step B1, the ammonium hydroxide solution has a mass fraction of 10–30 wt% and a dropping rate of 0.1–10 mL / min; after magnetic separation, it is washed with deionized water 3–5 times, with each wash using 10–50 mL / g of particles.

[0048] Further, in step B2, the dispersion concentration of the magnetic particles obtained in B1 in the mixed solvent is 2–20 mg / mL; the mass fraction of the ammonium hydroxide solution is 10–30 wt%; and the mass ratio of tetraethyl silicate to the magnetic particles obtained in B1 is 0.2:1–5:1.

[0049] Furthermore, in step B3, the ethanol used contains 1–5% deionized water by volume, and the dispersion concentration of the particles obtained in B2 in the ethanol is 10–50 mg / mL.

[0050] Furthermore, in step B4, the magnetic response time is measured under an external magnetic field with a magnetic field strength of 0.1–1.0 T and an aqueous dispersion with a concentration of 0.5–2 mg / mL, with the supernatant being visually clear as the endpoint; the D50 of the magnetic silica silanized particles used in step C2 is 80–240 nm.

[0051] Further, in step C1, the total mass ratio of 1,2,4-trichlorobenzene to cyclodextrin methacrylate and ethylene glycol dimethacrylate is 0.01:1–0.5:1; the total mass fraction of cyclodextrin methacrylate and ethylene glycol dimethacrylate in ethanol is 1–30 wt%; after mixing, the components are stirred and pre-incubated at room temperature for 1–2 h.

[0052] Furthermore, in step C2, the total mass ratio of magnetic silica silanized particles to cyclodextrin methacrylate and ethylene glycol dimethacrylate is 0.2:1–5:1.

[0053] Furthermore, in step C3, the amount of ethanol used for each washing is 10–50 mL / g of particles; drying is carried out at 40–60°C under a vacuum of not less than -0.06 MPa for 6–24 h.

[0054] Furthermore, in step D1, the dissolution is carried out by stirring at 20–40 °C for 0.5–6 h, with the endpoint being the absence of visible particles in the solution.

[0055] Further, in step D3, the mass fraction of glutaraldehyde in the glutaraldehyde aqueous solution is 10–30 wt%; the coating is performed by spin coating or drop coating, with a spin coating speed of 500–3000 rpm and a time of 10–60 s, or a drop coating volume of 5–50 μL.

[0056] Further, in step D4, the product is washed 1–5 times with deionized water and 1–3 times with 70–95% ethanol by volume, and then dried at 40–60 °C for 6–24 h.

[0057] Chitosan plays a key role in film formation and interfacial bonding within the system, enabling the online detection material to be coated onto the transducer substrate surface in the form of a film-forming solution and form a continuous dry film. The crosslinking components, calculated as glutaraldehyde, connect chitosan segments into a more stable network during curing, reducing the tendency for structural relaxation and film defect formation under flow and regeneration conditions. Magnetic core-shell molecularly imprinted particles provide the functional interface for the molecularly imprinted polymer shell. The magnetite core ensures controllable dispersion and recovery of the particles during preparation and post-processing. The silica interlayer acts as an isolation and support layer, facilitating silanization on its surface and further forming a polymer network. The cyclodextrin methacrylate and ethylene glycol dimethacrylate copolymer network forms selective action sites against 1,2,4-trichlorobenzene in the presence of template molecules. These components complement each other in terms of the stable crosslinked film-forming framework and the selectivity provided by the core-shell imprinting, ensuring both rapid mass transfer regeneration and long-term stability even under high filler loading conditions.

[0058] Beneficial technical effects

[0059] 1. A continuous dry film is formed by cross-linking and curing chitosan and cross-linking components (calculated as glutaraldehyde) on the surface of the transducer substrate. The curing temperature and curing time are limited to ensure that the film-forming sensitive layer material maintains the integrity and long-term stability of the film under circulation and regeneration conditions, reducing the risk of peeling and cracking.

[0060] 2. The magnetic core-shell molecularly imprinted particles consist of a magnetic core of iron oxide, a silica intermediate layer, and a molecularly imprinted polymer shell. The shell is a copolymer network of cyclodextrin methacrylate and ethylene glycol dimethacrylate, with 1,2,4-trichlorobenzene as a template, thereby enhancing the selectivity of the online detection material for the target molecule.

[0061] 3. By limiting the range of D50, magnetic response time, and molecularly imprinted polymer shell thickness of magnetic silica silanized particles, the controllability of particle dispersion and surface polymerization is taken into account; combined with the range design of particle mass fraction in dry film, the processing window and coating consistency under high filler load are improved.

[0062] 4. During the elution and post-treatment stages, the residual 1,2,4-trichlorobenzene in the particles is controlled to be no more than 0.10 wt%, and the residual glutaraldehyde is controlled to be no more than 0.5 wt% after curing and washing. This reduces background interference and facilitates regeneration and recycling, thereby alleviating the conflict between low-residue control and imprint structure preservation. Attached Figure Description

[0063] Figure 1 The image shows the superimposed XRD powder diffraction patterns of Example 1 and Comparative Example 8.

[0064] Figure 2 The cumulative distribution of XRDScherrer grain size is shown in Example 1 and Comparative Example 8.

[0065] Figure 3 The image shows the XPS high-resolution O1s spectrum peak fitting diagrams for Example 1 and Comparative Example 6.

[0066] Figure 4 The image shows the XPS high-resolution C1s spectrum peak fitting diagrams for Example 1 and Comparative Example 6.

[0067] Figure 5 The image shows the XPS high-resolution N1s spectrum peak fitting diagrams for Example 1 and Comparative Example 4.

[0068] Figure 6 Macroscopic optical photograph of the chitosan / glutaraldehyde crosslinked composite sensitive film prepared in Example 1.

[0069] Figure 7 This is a low-magnification SEM image of the surface morphology of the composite sensitive membrane in Example 1.

[0070] Figure 8 This is a TEM characterization image of the magnetic core-shell molecularly imprinted particles from Example 1. Detailed Implementation

[0071] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0072] Example 1

[0073] The 1,2,4-trichlorobenzene online detection material of this embodiment is a film-forming sensitive layer material that can be coated on the surface of a transducer. Based on the total mass of the dried online detection material of this embodiment, it contains 50 wt% chitosan, 2.5 wt% glutaraldehyde, and 45 wt% magnetic core-shell molecularly imprinted particles, with a total mass fraction of 97.5 wt%, not exceeding 100 wt%. The magnetic core-shell molecularly imprinted particles of this embodiment include a magnetic core, a silica intermediate layer, and a molecularly imprinted polymer shell. The magnetic core of this embodiment is iron(III) oxide (Fe3O4). The silica intermediate layer of this embodiment is silica. The molecularly imprinted polymer shell of this embodiment contains a polymer network formed by copolymerization of β-cyclodextrin methacrylate and ethylene glycol dimethacrylate. The β-cyclodextrin methacrylate of this embodiment is a product derived from β-cyclodextrin. The chitosan used to prepare the online detection material of this embodiment has a degree of deacetylation of 90% and a viscosity-average molecular weight of 300 kDa.

[0074] I. Preparation of Cyclodextrin Methacrylate

[0075] A1. Raw material preparation: Dissolve β-cyclodextrin in dimethyl sulfoxide to make the mass fraction of β-cyclodextrin 12wt%; add potassium carbonate in an amount of 0.28 times the molar amount of β-cyclodextrin.

[0076] A2. Reaction: Under a nitrogen inert atmosphere, glycidyl methacrylate containing p-methoxyphenol polymerization inhibitor was added dropwise to the solution obtained in step A1 at a rate of 3 mL / min, so that the molar ratio of glycidyl methacrylate to β-cyclodextrin was 1.0:1, and the reaction was carried out at 55 °C for 15 h.

[0077] A3. Post-treatment: The reaction solution obtained in step A2 was filtered through a filter medium with a pore size of 0.45 μm to remove inorganic salts; ethanol was added to the filtrate as a precipitant, with a mass ratio of ethanol to reaction solution of 11:1, and the mixture was allowed to stand at 0–4 ℃ for 1.5 h, then centrifuged at 6500 rpm for 12 min to collect the precipitate; the precipitate was washed three times with anhydrous ethanol, with an ethanol volume of 12 mL / g of product each time; the precipitate was dried at 50 ℃ for 15 h.

[0078] A4. Endpoint Criteria and Quality Control: The degree of substitution (DS) of the β-cyclodextrin methacrylate obtained in this embodiment is 0.17, and the residual dimethyl sulfoxide is no more than 1.0 wt% based on the average number of methacrylate groups on each cyclodextrin molecule.

[0079] II. Preparation of Magnetic Silaneized Silica Particles

[0080] B1. Preparation of magnetic cores: Ferric chloride hexahydrate and ferrous chloride tetrahydrate were dissolved in deionized water to make the molar ratio of ferric to ferrous iron 2.0:1 and the total concentration of iron salts 0.30 mol / L. The temperature was raised to 72 °C under a nitrogen inert atmosphere, and the pH was adjusted to 10 by adding 20 wt% ammonium hydroxide solution at a rate of 5 mL / min. The reaction was maintained at this temperature for 1.2 h. After magnetic separation, the resulting magnetic particles were washed four times with deionized water at a rate of 30 mL / g of particles each time until the pH of the washing solution was 7–8.

[0081] B2. Silica Coating: The magnetic particles obtained in step B1 were dispersed at a concentration of 10 mg / mL in a mixed solvent of ethanol and deionized water, with a volume ratio of ethanol to deionized water of 6:1; a 20 wt% ammonium hydroxide solution was added to adjust the pH to 10, and tetraethyl silicate was added, with a mass ratio of tetraethyl silicate to the magnetic particles obtained in step B1 of 2.5:1. The mixture was reacted at 30 ℃ for 14 h to obtain silica-coated magnetic particles.

[0082] B3. Silanization: The particles obtained in step B2 were dispersed at a concentration of 30 mg / mL in ethanol containing 3% deionized water by volume. 3-Methacryloxypropyltrimethoxysilane and 3-aminopropyltriethoxysilane were added in a mass ratio of 1:1, with a total amount of 5.5 wt% of the mass of the particles obtained in step B2. The reaction was carried out at 42 °C for 4.5 h.

[0083] B4. Endpoint Criteria and Quality Control: The D50 of the magnetic silica silanized particles obtained in this embodiment is 145 nm. The magnetic response time is not greater than 30 s under an external magnetic field of 0.5 T and the supernatant is visually clear as the endpoint. The D50 of the magnetic silica silanized particles used in step C2 in this embodiment is 145 nm.

[0084] III. Preparation of Magnetic Core-Shell Molecularly Imprinted Particles

[0085] C1. Preparation of prepolymer solution: 1,2,4-trichlorobenzene was added to ethanol as a template molecule, along with β-cyclodextrin methacrylate and ethylene glycol dimethacrylate obtained in step A, so that the mass ratio of β-cyclodextrin methacrylate to ethylene glycol dimethacrylate was 1:8; the total mass ratio of 1,2,4-trichlorobenzene to β-cyclodextrin methacrylate and ethylene glycol dimethacrylate was 0.15:1; the total mass fraction of β-cyclodextrin methacrylate and ethylene glycol dimethacrylate in ethanol was 15 wt%; after mixing, the components were stirred and pre-incubated at room temperature for 1.5 h.

[0086] C2. Surface polymerization: Magnetic silica silanized particles obtained in step B are added to the prepolymer solution of step C1. The mass ratio of magnetic silica silanized particles to the total mass of β-cyclodextrin methacrylate and ethylene glycol dimethacrylate is 2.0:1. Azobisisobutyronitrile is added as an initiator, and the amount of initiator is 1.1 wt% of the total mass of β-cyclodextrin methacrylate and ethylene glycol dimethacrylate in step C1. The reaction is carried out at 62 °C for 15 h under a nitrogen inert atmosphere to obtain core-shell particles containing template molecules.

[0087] C3. Elution and post-treatment: The template molecules were washed and eluted 6 times with anhydrous ethanol, with an ethanol volume of 30 mL / g particles each time, until the residual 1,2,4-trichlorobenzene in the particles was no more than 0.10 wt%. The particles were then dried at 50 ℃ and a vacuum degree of no less than -0.06 MPa for 15 h to obtain magnetic core-shell molecularly imprinted particles.

[0088] C4. Quality control: The thickness of the molecularly imprinted polymer shell in this embodiment is 15 nm; the mass fraction of iron(III) oxide in the magnetic core-shell molecularly imprinted particles in this embodiment is 50 wt%; and the D50 of the magnetic core-shell molecularly imprinted particles in this embodiment is 175 nm.

[0089] IV. Preparation of Film-Sensitive Layer Materials

[0090] D1. Film-forming solution: Chitosan with a degree of deacetylation of 90% and a viscosity-average molecular weight of 300 kDa was dissolved in an aqueous solution containing 1.2 wt% glacial acetic acid, with a chitosan mass fraction of 1.5 wt%. The solution was stirred at 30 ℃ for 3 h until no visible particles were visible.

[0091] D2. Compounding: Add the magnetic core-shell molecularly imprinted particles obtained in step C to the film-forming solution obtained in step D1, so that the mass fraction of the magnetic core-shell molecularly imprinted particles in the dry film is 45 wt%.

[0092] D3. Crosslinking film formation: Add 20 wt% glutaraldehyde aqueous solution to make the content of glutaraldehyde 2.5 wt%; apply the above mixture to the surface of the transducer substrate by spin coating at a speed of 1500 rpm for 30 s, and cure at 40 ℃ for 6 h after coating.

[0093] D4. Post-treatment and quality control: After curing, the film was washed three times with deionized water and twice with 85% ethanol (volume fraction), and then dried at 50 °C for 15 h. The dry film thickness obtained in this embodiment was 50 μm, and the residual glutaraldehyde was no more than 0.5 wt%, which yielded the 1,2,4-trichlorobenzene online detection material of this embodiment.

[0094] In this embodiment, β-cyclodextrin is used as the main functional unit. β-cyclodextrin methacrylate with a degree of substitution (DS) of 0.17 is prepared using a glycidyl methacrylate to β-cyclodextrin molar ratio of 1.0:1, a reaction temperature of 55 °C, and a potassium carbonate dosage of 0.28 times the molar amount. Magnetite (Fe3O4) magnetic cores are synthesized under conditions of 0.30 mol / L iron salt concentration, pH 10, and a temperature of 72 °C. These cores are then coated with TEOS and silica (2.5:1 mass ratio) and modified with a 1:1 mass ratio of bifunctional silanes to obtain magnetic silica silanized particles with a D50 of 145 nm. Surface-initiated polymerization is then performed at 62 °C with a functional monomer to crosslinking agent mass ratio of 1:8 and a template to monomer mass ratio of 0.15:1, under conditions of a magnetic particle to monomer mass ratio of 2.0:1, forming a molecularly imprinted polymer shell with a shell thickness of 15 nm. The resulting magnetic core-shell molecularly imprinted particles have a D50 of 175 nm and a Fe3O4 mass fraction of 50%. The film-forming material contains 50 wt% chitosan, 2.5 wt% glutaraldehyde, and 45 wt% magnetic core-shell molecularly imprinted particles. The dry film thickness after spin-coating is 50 μm. All synthesis parameters are at a balanced and moderate level, and the system exhibits both good film-forming continuity and stable recognition performance, with high process reproducibility. The material obtained in this example is suitable for continuous online monitoring of 1,2,4-trichlorobenzene at industrial wastewater discharge outlets, routine testing of effluent water quality from urban wastewater treatment plants, and the batch preparation and performance benchmark evaluation of standardized sensitive membranes in sensor research.

[0095] Example 2

[0096] The 1,2,4-trichlorobenzene online detection material of this embodiment is a film-forming sensitive layer material that can be coated on the surface of a transducer. Based on the total mass of the dried online detection material of this embodiment, it contains 35 wt% chitosan, 2.0 wt% glutaraldehyde, and 60 wt% magnetic core-shell molecularly imprinted particles, with a total mass fraction of 97.0 wt%, not exceeding 100 wt%. The magnetic core-shell molecularly imprinted particles of this embodiment include a magnetic core, a silica intermediate layer, and a molecularly imprinted polymer shell. The magnetic core of this embodiment is iron(III) oxide (Fe3O4). The silica intermediate layer of this embodiment is silica. The molecularly imprinted polymer shell of this embodiment contains a polymer network formed by copolymerization of γ-cyclodextrin methacrylate and ethylene glycol dimethacrylate. The γ-cyclodextrin methacrylate of this embodiment is a product derived from γ-cyclodextrin. The chitosan used to prepare the online detection material of this embodiment has a degree of deacetylation of 92% and a viscosity-average molecular weight of 200 kDa.

[0097] I. Preparation of Cyclodextrin Methacrylate

[0098] A1. Raw material preparation: Dissolve γ-cyclodextrin in dimethyl sulfoxide to make the mass fraction of γ-cyclodextrin 8wt%; add potassium carbonate in an amount of 0.35 times the molar amount of γ-cyclodextrin.

[0099] A2. Reaction: Under a nitrogen inert atmosphere, glycidyl methacrylate containing p-methoxyphenol polymerization inhibitor was added dropwise to the solution obtained in step A1 at a rate of 2 mL / min, so that the molar ratio of glycidyl methacrylate to γ-cyclodextrin was 1.5:1, and the reaction was carried out at 62 °C for 10 h.

[0100] A3. Post-treatment: The reaction solution obtained in step A2 was filtered through a filter medium with a pore size of 0.45 μm to remove inorganic salts; ethanol was added to the filtrate as a precipitant, with a mass ratio of ethanol to reaction solution of 8:1, and the mixture was allowed to stand at 0–4 ℃ for 1.0 h, and then centrifuged at 7000 rpm for 12 min to collect the precipitate; the precipitate was washed 4 times with anhydrous ethanol, with an ethanol volume of 15 mL / g of product each time; the precipitate was dried at 55 ℃ for 10 h.

[0101] A4. Endpoint Criteria and Quality Control: The degree of substitution (DS) of the γ-cyclodextrin methacrylate obtained in this embodiment is 0.22. Based on the average number of methacrylate groups on each cyclodextrin molecule, the residual dimethyl sulfoxide is no more than 1.0 wt%.

[0102] II. Preparation of Magnetic Silaneized Silica Particles

[0103] B1. Preparation of magnetic cores: Ferric chloride hexahydrate and ferrous chloride tetrahydrate were dissolved in deionized water to make the molar ratio of ferric to ferrous iron 2.1:1 and the total concentration of iron salts 0.25 mol / L; the temperature was raised to 75 ℃ under a nitrogen inert atmosphere, and the pH was adjusted to 10.5 by adding 25 wt% ammonium hydroxide solution at a rate of 3 mL / min, and the reaction was maintained at this temperature for 1.0 h; the resulting magnetic particles were magnetically separated and washed four times with deionized water at a rate of 25 mL / g of particles each time until the pH of the washing solution was 7–8.

[0104] B2. Silica Coating: The magnetic particles obtained in step B1 were dispersed at a concentration of 8 mg / mL in a mixed solvent of ethanol and deionized water, with a volume ratio of ethanol to deionized water of 8:1; a 25 wt% ammonium hydroxide solution was added to adjust the pH to 10.5, and tetraethyl silicate was added, with a mass ratio of tetraethyl silicate to the magnetic particles obtained in step B1 of 3.5:1. The mixture was reacted at 35 ℃ for 10 h to obtain silica-coated magnetic particles.

[0105] B3. Silanization: The particles obtained in step B2 were dispersed at a concentration of 40 mg / mL in ethanol containing 2% deionized water by volume. 3-Methacryloxypropyltrimethoxysilane and 3-aminopropyltriethoxysilane were added in a mass ratio of 7:3, and the total amount was 7.0 wt% of the mass of the particles obtained in step B2. The reaction was carried out at 50 °C for 3 h.

[0106] B4. Endpoint Criteria and Quality Control: The D50 of the magnetic silica silanized particles obtained in this embodiment is 120 nm. The magnetic response time is not greater than 30 s under an external magnetic field of 0.5 T and the supernatant is visually clear as the endpoint. The magnetic silica silanized particles used in step C2 have a D50 of 120 nm.

[0107] III. Preparation of Magnetic Core-Shell Molecularly Imprinted Particles

[0108] C1. Preparation of prepolymer solution: 1,2,4-trichlorobenzene was added to ethanol as a template molecule, along with γ-cyclodextrin methacrylate and ethylene glycol dimethacrylate obtained in step A, so that the mass ratio of γ-cyclodextrin methacrylate to ethylene glycol dimethacrylate was 1:5; the total mass ratio of 1,2,4-trichlorobenzene to γ-cyclodextrin methacrylate and ethylene glycol dimethacrylate was 0.25:1; the total mass fraction of γ-cyclodextrin methacrylate and ethylene glycol dimethacrylate in ethanol was 20 wt%; after mixing, the components were stirred and pre-incubated at room temperature for 1.5 h.

[0109] C2. Surface polymerization: Magnetic silica silanized particles obtained in step B are added to the prepolymer solution of step C1. The mass ratio of magnetic silica silanized particles to the total mass of γ-cyclodextrin methacrylate and ethylene glycol dimethacrylate is 1.5:1. Azobisisobutyronitrile is added as an initiator, and the amount of initiator is 0.6 wt% of the total mass of γ-cyclodextrin methacrylate and ethylene glycol dimethacrylate in step C1. The reaction is carried out at 65 °C for 12 h under a nitrogen inert atmosphere to obtain core-shell particles containing template molecules.

[0110] C3. Elution and post-treatment: The template molecules were washed and eluted 8 times with anhydrous ethanol, with an ethanol volume of 25 mL / g particles each time, until the residual 1,2,4-trichlorobenzene in the particles was no more than 0.10 wt%. The particles were then dried at 55 ℃ and a vacuum degree of no less than -0.06 MPa for 12 h to obtain magnetic core-shell molecularly imprinted particles.

[0111] C4. Quality control: The thickness of the molecularly imprinted polymer shell in this embodiment is 20 nm; the mass fraction of iron(III) oxide in the magnetic core-shell molecularly imprinted particles in this embodiment is 42 wt%; and the D50 of the magnetic core-shell molecularly imprinted particles in this embodiment is 160 nm.

[0112] IV. Preparation of Film-Sensitive Layer Materials

[0113] D1. Film-forming solution: Chitosan with a degree of deacetylation of 92% and a viscosity-average molecular weight of 200 kDa was dissolved in an aqueous solution containing 1.0 wt% glacial acetic acid. The chitosan mass fraction was 1.0 wt%. The solution was stirred at 25 °C for 2 h until no visible particles were visible.

[0114] D2. Compounding: Add the magnetic core-shell molecularly imprinted particles obtained in step C to the film-forming solution obtained in step D1, so that the mass fraction of the magnetic core-shell molecularly imprinted particles in the dry film is 60 wt%.

[0115] D3. Crosslinking film formation: Add 15 wt% glutaraldehyde aqueous solution to make the content of glutaraldehyde 2.0 wt%; apply the above mixture to the surface of the transducer substrate by spin coating at a speed of 2000 rpm for 20 s, and cure at 35 ℃ for 8 h after coating.

[0116] D4. Post-treatment and quality control: After curing, the film was washed three times with deionized water and twice with 80% ethanol (volume fraction), and then dried at 50 °C for 12 h. The dry film thickness obtained in this embodiment was 35 μm, and the residual glutaraldehyde was no more than 0.5 wt%, which yielded the 1,2,4-trichlorobenzene online detection material of this embodiment.

[0117] The material obtained in this embodiment is suitable for highly sensitive online monitoring of trace amounts of 1,2,4-trichlorobenzene in surface water and drinking water sources, emergency early warning detection of pollution in water bodies surrounding chemical enterprises, and rapid quantitative screening of low-concentration pollutants.

[0118] Example 3

[0119] The 1,2,4-trichlorobenzene online detection material of this embodiment is a film-forming sensitive layer material that can be coated on the surface of a transducer. Based on the total mass of the dried online detection material of this embodiment, it contains 65 wt% chitosan, 3.5 wt% glutaraldehyde, and 25 wt% magnetic core-shell molecularly imprinted particles, with a total mass fraction of 93.5 wt%, not exceeding 100 wt%. The magnetic core-shell molecularly imprinted particles of this embodiment include a magnetic core, a silica intermediate layer, and a molecularly imprinted polymer shell. The magnetic core of this embodiment is iron(III) oxide (Fe3O4). The silica intermediate layer of this embodiment is silica. The molecularly imprinted polymer shell of this embodiment contains a polymer network formed by copolymerization of β-cyclodextrin methacrylate and ethylene glycol dimethacrylate. The β-cyclodextrin methacrylate of this embodiment is a product derived from β-cyclodextrin. The chitosan used to prepare the online detection material of this embodiment has a degree of deacetylation of 95% and a viscosity-average molecular weight of 420 kDa.

[0120] I. Preparation of Cyclodextrin Methacrylate

[0121] A1. Raw material preparation: Dissolve β-cyclodextrin in dimethyl sulfoxide to make the mass fraction of β-cyclodextrin 16wt%; add potassium carbonate in an amount of 0.15 times the molar amount of β-cyclodextrin.

[0122] A2. Reaction: Under a nitrogen inert atmosphere, glycidyl methacrylate containing p-methoxyphenol polymerization inhibitor was added dropwise to the solution obtained in step A1 at a rate of 4 mL / min, so that the molar ratio of glycidyl methacrylate to β-cyclodextrin was 0.5:1, and the reaction was carried out at 45 °C for 18 h.

[0123] A3. Post-treatment: The reaction solution obtained in step A2 was filtered through a filter medium with a pore size of 0.22 μm to remove inorganic salts; ethanol was added to the filtrate as a precipitant, with a mass ratio of ethanol to reaction solution of 15:1, and the mixture was allowed to stand at 0–4 ℃ for 0.8 h, and then centrifuged at 5500 rpm for 11 min to collect the precipitate; the precipitate was washed twice with anhydrous ethanol, with an ethanol volume of 8 mL / g of product each time; the precipitate was dried at 45 ℃ for 20 h.

[0124] A4. Endpoint Criteria and Quality Control: The degree of substitution (DS) of the β-cyclodextrin methacrylate obtained in this embodiment is 0.10, and the residual dimethyl sulfoxide is no more than 1.0 wt% based on the average number of methacrylate groups on each cyclodextrin molecule.

[0125] II. Preparation of Magnetic Silaneized Silica Particles

[0126] B1. Preparation of magnetic cores: Ferric chloride hexahydrate and ferrous chloride tetrahydrate were dissolved in deionized water to make the molar ratio of ferric to ferrous iron 1.9:1 and the total concentration of iron salts 0.40 mol / L; the temperature was raised to 68 ℃ under a nitrogen inert atmosphere, and the pH was adjusted to 9.5 by adding 15 wt% ammonium hydroxide solution at a rate of 7 mL / min, and the reaction was maintained at this temperature for 1.8 h; the resulting magnetic particles were magnetically separated and washed three times with deionized water at a rate of 20 mL / g of particles each time until the pH of the washing solution was 7–8.

[0127] B2. Silica Coating: The magnetic particles obtained in step B1 were dispersed at a concentration of 15 mg / mL in a mixed solvent of ethanol and deionized water, with a volume ratio of ethanol to deionized water of 4:1; a 15 wt% ammonium hydroxide solution was added to adjust the pH to 9.5, and tetraethyl silicate was added, with a mass ratio of tetraethyl silicate to the magnetic particles obtained in step B1 of 1.5:1. The reaction was carried out at 25 ℃ for 20 h to obtain silica-coated magnetic particles.

[0128] B3. Silanization: The particles obtained in step B2 were dispersed at a concentration of 20 mg / mL in ethanol containing 4% deionized water by volume. 3-Methacryloxypropyltrimethoxysilane and 3-aminopropyltriethoxysilane were added in a mass ratio of 3:7, with a total amount of 3.5 wt% of the mass of the particles obtained in step B2. The reaction was carried out at 35 °C for 6 h.

[0129] B4. Endpoint Criteria and Quality Control: The D50 of the magnetic silica silanized particles obtained in this embodiment is 200 nm. The magnetic response time is not greater than 30 s under an external magnetic field of 0.5 T and the supernatant is visually clear as the endpoint. The D50 of the magnetic silica silanized particles used in step C2 in this embodiment is 200 nm.

[0130] III. Preparation of Magnetic Core-Shell Molecularly Imprinted Particles

[0131] C1. Preparation of prepolymer solution: 1,2,4-trichlorobenzene was added to ethanol as a template molecule, along with β-cyclodextrin methacrylate and ethylene glycol dimethacrylate obtained in step A, so that the mass ratio of β-cyclodextrin methacrylate to ethylene glycol dimethacrylate was 1:15; the total mass ratio of 1,2,4-trichlorobenzene to β-cyclodextrin methacrylate and ethylene glycol dimethacrylate was 0.08:1; the total mass fraction of β-cyclodextrin methacrylate and ethylene glycol dimethacrylate in ethanol was 8 wt%; after mixing, the components were stirred and pre-incubated at room temperature for 1.0 h.

[0132] C2. Surface polymerization: Magnetic silica silanized particles obtained in step B are added to the prepolymer solution of step C1. The mass ratio of magnetic silica silanized particles to the total mass of β-cyclodextrin methacrylate and ethylene glycol dimethacrylate is 3.5:1. Azobisisobutyronitrile is added as an initiator, and the amount of initiator is 1.8 wt% of the total mass of β-cyclodextrin methacrylate and ethylene glycol dimethacrylate in step C1. The reaction is carried out at 58 °C for 20 h under a nitrogen inert atmosphere to obtain core-shell particles containing template molecules.

[0133] C3. Elution and post-treatment: The template molecules were washed and eluted four times with anhydrous ethanol, with an ethanol volume of 40 mL / g particles each time, until the residual 1,2,4-trichlorobenzene in the particles was no more than 0.10 wt%. The particles were then dried at 45 °C and a vacuum degree of no less than -0.06 MPa for 20 h to obtain magnetic core-shell molecularly imprinted particles.

[0134] C4. Quality control: The thickness of the molecularly imprinted polymer shell in this embodiment is 8 nm; the mass fraction of iron(III) oxide in the magnetic core-shell molecularly imprinted particles in this embodiment is 58 wt%; and the D50 of the magnetic core-shell molecularly imprinted particles in this embodiment is 215 nm.

[0135] IV. Preparation of Film-Sensitive Layer Materials

[0136] D1. Film-forming solution: Chitosan with a degree of deacetylation of 95% and a viscosity-average molecular weight of 420 kDa was dissolved in an aqueous solution containing 1.8 wt% glacial acetic acid, with a chitosan mass fraction of 2.5 wt%. The solution was stirred at 35 ℃ for 5 h until no visible particles were observed.

[0137] D2. Compounding: Add the magnetic core-shell molecularly imprinted particles obtained in step C to the film-forming solution obtained in step D1, so that the mass fraction of the magnetic core-shell molecularly imprinted particles in the dry film is 25 wt%.

[0138] D3. Crosslinking film formation: Add 25 wt% glutaraldehyde aqueous solution to make the content of glutaraldehyde 3.5 wt%; apply the above mixture to the surface of the transducer substrate by spin coating at a speed of 800 rpm for 50 s, and cure at 55 ℃ for 2 h after coating.

[0139] D4. Post-treatment and quality control: After curing, the film was washed 4 times with deionized water and 2 times with 90% ethanol (volume fraction), and then dried at 55 °C for 20 h. The dry film thickness obtained in this embodiment was 75 μm, and the residual glutaraldehyde was no more than 0.5 wt%, which is the 1,2,4-trichlorobenzene online detection material of this embodiment.

[0140] The material obtained in this embodiment is suitable for long-term continuous online monitoring of the total discharge outlet of chemical industrial parks, online determination of 1,2,4-trichlorobenzene in complex industrial wastewater containing high concentrations of coexisting matrix interference (high salinity, high suspended solids), and outdoor long-term monitoring instruments with high requirements for the durability of sensor membranes.

[0141] Example 4

[0142] The 1,2,4-trichlorobenzene online detection material of this embodiment is a film-forming sensitive layer material that can be coated on the surface of a transducer. Based on the total mass of the dried online detection material of this embodiment, it contains 25 wt% chitosan, 4.0 wt% glutaraldehyde, and 70 wt% magnetic core-shell molecularly imprinted particles, with a total mass fraction of 99.0 wt%, not exceeding 100 wt%. The magnetic core-shell molecularly imprinted particles of this embodiment include a magnetic core, a silica intermediate layer, and a molecularly imprinted polymer shell. The magnetic core of this embodiment is iron(III) oxide (Fe3O4). The silica intermediate layer of this embodiment is silica. The molecularly imprinted polymer shell of this embodiment contains a polymer network formed by copolymerization of γ-cyclodextrin methacrylate and ethylene glycol dimethacrylate. The γ-cyclodextrin methacrylate of this embodiment is a product derived from γ-cyclodextrin. The chitosan used to prepare the online detection material of this embodiment has a degree of deacetylation of 88% and a viscosity-average molecular weight of 150 kDa.

[0143] I. Preparation of Cyclodextrin Methacrylate

[0144] A1. Raw material preparation: Dissolve γ-cyclodextrin in dimethyl sulfoxide to make the mass fraction of γ-cyclodextrin 10wt%; add potassium carbonate in an amount of 0.42 times the molar amount of γ-cyclodextrin.

[0145] A2. Reaction: Under a nitrogen inert atmosphere, glycidyl methacrylate containing p-methoxyphenol polymerization inhibitor was added dropwise to the solution obtained in step A1 at a rate of 2 mL / min, so that the molar ratio of glycidyl methacrylate to γ-cyclodextrin was 1.8:1, and the reaction was carried out at 63 °C for 9 h.

[0146] A3. Post-treatment: The reaction solution obtained in step A2 was filtered through a filter medium with a pore size of 0.45 μm to remove inorganic salts; ethanol was added to the filtrate as a precipitant, with a mass ratio of ethanol to reaction solution of 12:1, and the mixture was allowed to stand at 0–4 ℃ for 1.5 h, then centrifuged at 7000 rpm for 13 min to collect the precipitate; the precipitate was washed 4 times with anhydrous ethanol, with an ethanol volume of 14 mL / g of product each time; the precipitate was dried at 55 ℃ for 18 h.

[0147] A4. Endpoint Criteria and Quality Control: The degree of substitution (DS) of the γ-cyclodextrin methacrylate obtained in this embodiment is 0.27. Based on the average number of methacrylate groups on each cyclodextrin molecule, the residual dimethyl sulfoxide is no more than 1.0 wt%.

[0148] II. Preparation of Magnetic Silaneized Silica Particles

[0149] B1. Preparation of magnetic cores: Ferric chloride hexahydrate and ferrous chloride tetrahydrate were dissolved in deionized water to make the molar ratio of ferric to ferrous iron 2.0:1 and the total concentration of iron salts 0.32 mol / L. The temperature was raised to 73 °C under a nitrogen inert atmosphere, and the pH was adjusted to 10 by adding 22 wt% ammonium hydroxide solution at a rate of 4 mL / min. The reaction was maintained at this temperature for 1.2 h. After magnetic separation, the resulting magnetic particles were washed four times with deionized water at a rate of 28 mL / g of particles each time until the pH of the washing solution was 7–8.

[0150] B2. Silica Coating: The magnetic particles obtained in step B1 were dispersed at a concentration of 12 mg / mL in a mixed solvent of ethanol and deionized water, with a volume ratio of ethanol to deionized water of 7:1; a 22 wt% ammonium hydroxide solution was added to adjust the pH to 10, and tetraethyl silicate was added, with a mass ratio of tetraethyl silicate to the magnetic particles obtained in step B1 of 1.8:1. The reaction was carried out at 30 ℃ for 16 h to obtain silica-coated magnetic particles.

[0151] B3. Silanization: The particles obtained in step B2 were dispersed at a concentration of 35 mg / mL in ethanol containing 3% deionized water by volume. 3-Methacryloxypropyltrimethoxysilane and 3-aminopropyltriethoxysilane were added in a mass ratio of 6:4, and the total amount was 8.0 wt% of the mass of the particles obtained in step B2. The reaction was carried out at 52 °C for 2 h.

[0152] B4. Endpoint Criteria and Quality Control: The D50 of the magnetic silica silanized particles obtained in this embodiment is 190 nm. The magnetic response time is not greater than 30 s under an external magnetic field of 0.5 T and the supernatant is visually clear as the endpoint. The D50 of the magnetic silica silanized particles used in step C2 in this embodiment is 190 nm.

[0153] III. Preparation of Magnetic Core-Shell Molecularly Imprinted Particles

[0154] C1. Preparation of prepolymer solution: 1,2,4-trichlorobenzene was added to ethanol as a template molecule, along with γ-cyclodextrin methacrylate and ethylene glycol dimethacrylate obtained in step A, so that the mass ratio of γ-cyclodextrin methacrylate to ethylene glycol dimethacrylate was 1:4; the total mass ratio of 1,2,4-trichlorobenzene to γ-cyclodextrin methacrylate and ethylene glycol dimethacrylate was 0.30:1; the total mass fraction of γ-cyclodextrin methacrylate and ethylene glycol dimethacrylate in ethanol was 22 wt%; after mixing, the components were stirred and pre-incubated at room temperature for 1.5 h.

[0155] C2. Surface polymerization: Magnetic silica silanized particles obtained in step B were added to the prepolymer solution of step C1, with the mass ratio of magnetic silica silanized particles to the total mass of γ-cyclodextrin methacrylate and ethylene glycol dimethacrylate being 4.0:1; azobisisobutyronitrile was added as an initiator, with the amount of initiator being 0.4 wt% of the total mass of γ-cyclodextrin methacrylate and ethylene glycol dimethacrylate in step C1; the reaction was carried out at 67 ℃ for 8 h under a nitrogen inert atmosphere to obtain core-shell particles containing template molecules.

[0156] C3. Elution and post-treatment: The template molecules were washed and eluted 9 times with anhydrous ethanol, with an ethanol volume of 45 mL / g particles each time, until the residual 1,2,4-trichlorobenzene in the particles was no more than 0.10 wt%. The particles were then dried at 55 ℃ and a vacuum degree of no less than -0.06 MPa for 18 h to obtain magnetic core-shell molecularly imprinted particles.

[0157] C4. Quality control: The thickness of the molecularly imprinted polymer shell in this embodiment is 10 nm; the mass fraction of iron(III) oxide in the magnetic core-shell molecularly imprinted particles in this embodiment is 63 wt%; and the D50 of the magnetic core-shell molecularly imprinted particles in this embodiment is 210 nm.

[0158] IV. Preparation of Film-Sensitive Layer Materials

[0159] D1. Film-forming solution: Chitosan with a degree of deacetylation of 88% and a viscosity-average molecular weight of 150 kDa was dissolved in an aqueous solution containing 0.8 wt% glacial acetic acid. The chitosan mass fraction was 0.8 wt%. The solution was stirred at 25 °C for 2 h until no visible particles were visible.

[0160] D2. Compounding: Add the magnetic core-shell molecularly imprinted particles obtained in step C to the film-forming solution obtained in step D1, so that the mass fraction of the magnetic core-shell molecularly imprinted particles in the dry film is 70 wt%.

[0161] D3. Crosslinking film formation: Add 25 wt% glutaraldehyde aqueous solution to make the content of glutaraldehyde 4.0 wt%; apply the above mixture to the transducer substrate surface by drop coating, with a drop coating amount of 25 μL, and cure at 45℃ for 4 h after coating.

[0162] D4. Post-treatment and quality control: After curing, the film was washed 4 times with deionized water and 2 times with 85% ethanol (volume fraction), and then dried at 55 °C for 18 h. The dry film thickness obtained in this embodiment was 65 μm, and the residual glutaraldehyde was no more than 0.5 wt%, which is the 1,2,4-trichlorobenzene online detection material of this embodiment.

[0163] The material obtained in this embodiment is applicable to the preparation of functional sensitive membranes for high-throughput online analysis systems that require auxiliary separation and enrichment with the aid of an external magnetic field before detection, as well as the fabrication of sensitive membranes for each unit in multi-channel sensor array instruments that require high recognition capacity per unit area.

[0164] Comparative Example 1: It is basically the same as Example 1, except that the amount of chitosan in the film-forming sensitive layer material is 12 wt% (the magnetic core-shell molecular imprinted particles are kept at 45 wt%, the content of glutaraldehyde is kept at 2.5 wt%, and the sum of the mass fractions of the three is 59.5 wt%), while the amount of other components and the preparation conditions remain unchanged.

[0165] Comparative Example 2: It is basically the same as Example 1, except that the mass fraction of magnetic core-shell molecular imprinted particles in the dry film of the film-forming sensitive layer material is 8 wt% (chitosan is kept at 50 wt%, the content of glutaraldehyde is kept at 2.5 wt%, and the sum of the mass fractions of the three is 60.5 wt%), while the amount of other components and preparation conditions remain unchanged.

[0166] Comparative Example 3: It is basically the same as Example 1, except that the mass fraction of magnetic core-shell molecular imprinted particles in the dry film of the film-forming sensitive layer material is 80 wt%, and the amount of chitosan is adjusted to 12 wt% (the content of glutaraldehyde is kept at 2.5 wt%, and the sum of the mass fractions of the three is 94.5 wt%). Other preparation conditions remain unchanged.

[0167] Comparative Example 4: It is basically the same as Example 1, except that the content of glutaraldehyde in step D3 is 0.05 wt%, while the amount of other components and preparation conditions remain unchanged.

[0168] Comparative Example 5: It is basically the same as Example 1, except that the content of glutaraldehyde in step D3 is 8.0 wt%, while the amount of other components and preparation conditions remain unchanged.

[0169] Comparative Example 6: Basically the same as Example 1, except that in step C1, methacrylic acid of equal mass is used instead of β-cyclodextrin methacrylate as the functional monomer (specific steps: methacrylic acid (analytical grade, purity ≥99.0%, commercially available) and ethylene glycol dimethacrylate are dissolved in ethanol at a mass ratio of 1:8, so that the total mass fraction of the two in ethanol is 15wt%; 1,2,4-trichlorobenzene is added so that the mass ratio of the template molecule to the total mass of the functional monomer and crosslinking agent is 0.15:1; after mixing all components, the mixture is stirred and pre-incubated at room temperature for 1.5 h; subsequent steps C2~C4 and all film-forming steps D are consistent with Example 1), and other conditions remain unchanged.

[0170] Comparative Example 7: Basically the same as Example 1, except that the template molecule 1,2,4-trichlorobenzene is omitted in step C1 (i.e., 1,2,4-trichlorobenzene is not added to the prepolymer solution to prepare non-imprinted polymer particles); the amount of azobisisobutyronitrile used in step C2 is the same as in Example 1; the elution step in step C3 is still washing with ethanol 6 times, and the remaining steps C4 and all film-forming steps D are consistent with Example 1), and other preparation conditions remain unchanged.

[0171] Comparative Example 8: It is basically the same as Example 1, except that step B2 (silica coating step) is omitted. The magnetic particles of iron oxide obtained in step B1 are directly used for silanization treatment in step B3. That is, the magnetic core-shell molecular imprinted particles do not contain a silicon dioxide intermediate layer. Other preparation conditions remain unchanged.

[0172] Performance testing:

[0173] The sensitivity and detection limit of the sensor for 1,2,4-trichlorobenzene in water obtained by spin-coating the film-forming sensitive layer material of the present invention onto a quartz crystal microbalance transducer were determined by the following method. Based on the Sauerbrey equation, the binding of the target molecule to the sensitive layer causes an increase in resonant mass, driving a negative shift in the resonant frequency, and the frequency change is linearly related to the binding mass. At 25±1 °C, 1,2,4-trichlorobenzene standard solutions with concentration gradients of 0.10, 0.50, 1.0, 2.0, 5.0, 10, 20, 50, and 100 μg / L were prepared using phosphate buffer (pH 7.0, 0.01 mol / L) as the carrier. These solutions were sequentially passed through the sensor at a flow rate of 0.5 mL / min. After each concentration was equilibrated for 20 min, the stable frequency response values ​​were recorded, and a calibration curve was plotted. The frequency response was linearly fitted to the concentration, and the sensitivity was measured by the slope. LOD = 3σ / S. ≥ 3 parallel sensors were used, and the mean ± standard deviation was reported to quantitatively evaluate the device's response sensitivity (Hz·L·μg). -1 ) and detection limit (μg / L).

[0174] The selectivity of magnetic core-shell molecularly imprinted particles for recognizing 1,2,4-trichlorobenzene relative to structural analogs is characterized by the selectivity coefficient k'. Under the same target concentration conditions, the frequency response of the sensor to the target molecule (1,2,4-trichlorobenzene) and interfering substances (1,2,3-trichlorobenzene, 1,3,5-trichlorobenzene) was measured, and the ratio of the two responses was k'. A larger k' indicates higher selectivity. Single-component standard solutions of 1,2,4-trichlorobenzene, 1,2,3-trichlorobenzene, and 1,3,5-trichlorobenzene with a concentration of 10 μg / L were prepared and sequentially flowed through the sensor at 25±1 ℃, pH 7.0, and a flow rate of 0.5 mL / min. After each solution equilibrated for 20 min, the frequency response was recorded. At the same time, the frequency response of the sensor with non-imprinted polymer particles (comparative Example 7 material) was measured to calculate the imprinting factor (IF = MIP response / NIP response); k' = Δf(1,2,4-TCB) / Δf(interference). Parallel experiments with n≥3 were used, and the mean ± standard deviation was reported.

[0175] The performance retention capability of the film-forming sensitive layer under flow-through adsorption-regeneration cycle conditions was quantitatively evaluated by the frequency response retention rate (%) after 50 cycles. Under flow-through conditions, the sensor was regenerated by rinsing with ethanol to remove adsorbed template molecules. The degree of frequency response decay was measured through multiple cycles to assess long-term stability. Using phosphate buffer (pH 7.0, 25±1 ℃) as the carrier, 10 μg / L of 1,2,4-trichlorobenzene standard solution was passed through (flow rate 0.5 mL / min). After adsorption equilibration for 20 min, the frequency response Δf was recorded. Regeneration was then achieved by rinsing with 85% ethanol aqueous solution (flow rate 1.0 mL / min) for 60 s, followed by equilibration with buffer for 5 min to complete one cycle. This process was repeated 50 times, and Δf was recorded each time. n The response retention rate (Δf) is calculated as the ratio of the 50th response to the initial response. 50 / Δf1×100%), using n≥3 parallel sensors, report mean ± standard deviation.

[0176] The physical integrity of the film-forming material under simulated flow conditions was characterized by the membrane mass loss rate (%) after 72 h of flow rinsing. A continuously flowing liquid applied fluid shear force to the membrane layer. The adhesion strength of the membrane layer to the transducer surface and its resistance to flow erosion were evaluated by accurately weighing the difference in membrane mass before and after rinsing. Dry membrane samples obtained by coating the film-forming sensitive layer material onto a standard transducer substrate were dried in a 50 ℃ oven to constant weight, and the initial dry membrane mass m0 was accurately weighed (balance accuracy 0.01 mg). The samples were placed in a flow cell and continuously rinsed with phosphate buffer at 25±1 ℃, pH 7.0, at a flow rate of 2.0 mL / min for 72 h. After removal, the samples were dried at 50 ℃ to constant weight, and the final dry membrane mass m1 was weighed. The membrane mass loss rate [(m...]] was calculated. 0-[m1) / m0×100%], using n≥3 parallel samples, report the mean ± standard deviation.

[0177] The crystal structure of the magnetic Fe3O4 particles prepared in step B1 and the final magnetic core-shell molecularly imprinted particle powder (Example 1), as well as the particles obtained by omitting the silica coating step (Comparative Example 8), were confirmed by XRD characterization. X-rays exhibited Bragg diffraction in the crystals, and the Fe3O4 inverse spinel structure showed characteristic diffraction peaks at 2θ = 30.1°, 35.5°, 43.1°, 56.9°, and 62.5° (JCPDS 19-0629); the SiO2 amorphous layer showed broadened and diffused peaks at 2θ = 15–30°, which can be compared with the spectrum of Comparative Example 8 to confirm its existence. The sample was ground into powder, and diffraction patterns were acquired using an X-ray diffractometer (Cu Kα radiation, λ = 0.15406 nm, tube voltage 40 kV, tube current 40 mA). The 2θ range was 10–80°, the step size was 0.02°, and the scan rate was 2° / min. The diffraction angle was corrected using NIST SRM 640e silicon powder standard. The average grain size was calculated using the Scherrer formula D = Kλ / (βcosθ). Peak positions were assigned by comparing the spectra of Example 1 and Comparative Example 8 using Origin overlay plots, and the grain size was calculated using the Scherrer formula to confirm the iron oxide spinel ferrite crystal phase and prove the existence of the silicon dioxide interlayer.

[0178] Figure 1 The XRD powder diffraction patterns of Example 1 and Comparative Example 8 are superimposed. The basic parameters are Cu Kα radiation wavelength of 0.15406 nm, 2θ range of 10 to 80 degrees, step size of 0.02 degrees, and scan rate of 2 degrees per minute. The diffraction angle is corrected with NIST SRM 640e silicon powder. The variable parameters are that Comparative Example 8 omits step B2 silica coating, while Example 1 retains the silica interlayer. The results show that both retain the characteristic peaks of iron oxide inverse spinel at approximately 30.1, 35.5, 43.1, 56.9, and 62.5 degrees of 2θ. Example 1 also shows a broadened and diffused peak at 15 to 30 degrees of 2θ that is not present in Comparative Example 8. From both crystalline phase and amorphous characteristics, it is confirmed that the silica interlayer is successfully coated and the magnetic core structure is intact.

[0179] Figure 2The XRD Scherrer cumulative distribution maps of Example 1 and Comparative Example 8 are shown. The basic parameters are the full width at half maximum (FWHM) of the characteristic diffraction peaks of iron oxide and the calculation of the grain size according to the Scherrer formula D = Kλ divided by βcosθ, which are presented in a cumulative distribution manner. The variable parameter is whether there is a silicon dioxide intermediate layer. The results show that the grain size distribution of the two are on the same order of magnitude and there is no systematic amplification or reduction. This indicates that the silicon dioxide coating mainly introduces the amorphous layer signal without destroying the crystallographic integrity of iron oxide, thus supporting the rationality of the independent verification of the layered core-shell structure.

[0180] Figure 3 The XPS high-resolution O 1s spectrum peak fitting diagrams for Example 1 and Comparative Example 6 are shown. The basic parameters are: acquiring O 1s high-resolution spectra and fitting the components using Voigt peak shapes to quantify the peak area ratio. The variable parameter is that the shell functional monomer of Example 1 is β-cyclodextrin methacrylate. The results show that a characteristic component belonging to the cyclodextrin ether bond C–O–C appears at a binding energy of about 532.5 eV, and its proportion can be quantified. This indicates that the cyclodextrin-related oxidative environment is introduced into the molecularly imprinted shell and provides a structural basis for the recognition site.

[0181] Figure 4 The XPS high-resolution C 1s spectrum peak fitting diagrams for Example 1 and Comparative Example 6 are shown. The basic parameters are acquiring C 1s high-resolution spectra and performing Voigt peak fitting and peak area normalization quantification. The variable parameter is the β-cyclodextrin methacrylate and ethylene glycol dimethacrylate copolymer network in the shell of Example 1. The results show that the area ratio of C–O related components is increased and is consistent with the C–O–C components in O1s, indicating that the cyclodextrin-derived structural units are stably introduced into the shell and are consistent with the direction of selectivity enhancement.

[0182] Figure 5 The XPS high-resolution N 1s spectrum peak fitting diagrams for Example 1 and Comparative Example 4 are shown. The basic parameters are: acquiring N 1s high-resolution spectra and using Voigt peak fitting to separate amino and imine bond components and quantifying the degree of crosslinking by area ratio. The variable parameter is that the content of glutaraldehyde in the film-forming system of Example 1 is 2.5 wt%. The results show that at a binding energy of about 399.5 eV, the proportion of C=N imine bond component is higher and the amino component is relatively lower, indicating that the chitosan amino group and glutaraldehyde undergo sufficient Schiff base crosslinking, providing a chemical bond level basis for the stability of the membrane under circulation and regeneration conditions.

[0183] Figure 6The image shows a macroscopic optical photograph of the chitosan / glutaraldehyde crosslinked composite sensitive film prepared in Example 1, revealing its dark gray to blackish-brown appearance, matte surface, and overall coverage morphology on the transducer substrate. This morphology mainly originates from the intrinsic absorption of the Fe3O4 core, the color development of the chitosan crosslinking, and the interfacial scattering caused by the high loading of SiO2 / MIP particles. This demonstrates the good film-forming properties and substrate adhesion of the composite film under high filler loading, and the basic parameters meet the expected dry film thickness of 50 μm.

[0184] Figure 7 This is a low-magnification SEM image of the composite sensitive membrane from Example 1, with a field of view of approximately 50 μm. The main observation variable was the overall continuity of the membrane layer under a high filler loading of 45 wt%. The results show that the membrane layer completely covers the substrate, with no obvious pinholes or delamination defects, demonstrating that the chitosan crosslinking system has good adhesion. Submicron to micron-sized agglomerated protrusions with a scale of approximately 0.5–3 μm are present on the surface, consistent with the localized accumulation characteristics caused by the spin-coating process, verifying that the macroscopic uniformity of the high-loading composite membrane is within a reasonable range.

[0185] Figure 8 TEM characterization of the magnetic core-shell molecularly imprinted particles in Example 1. (a) Low-magnification bright-field TEM image shows the core-shell hierarchical structure of the particles: a high-contrast Fe3O4 core, a light gray SiO2 intermediate layer, and a low-contrast MIP shell; (b) Magnified TEM image shows the shell continuity and interface transition features; (c) HRTEM image shows clear lattice fringes in the core region, and the measured interplanar spacing can be attributed to Fe3O4(220) ( nm) and Fe3O4(311) (nm) etc.; (d) The corresponding SAED pattern is a polycrystalline ring, indicating that the core is a polycrystalline state of spinel ferrite.

[0186] Table 1. Performance comparison data between the examples and comparative examples.

[0187] Sample number Limit of detection (LOD) (μg / L) Selectivity coefficient k' (relative to 1,2,3-TCB) Response retention rate after 50 cycles (%) 72 h membrane mass loss rate (%) Example 1 0.8±0.1 4.2±0.3 91.5±1.2 3.2±0.4 Example 2 0.5±0.1 4.8±0.4 88.2±1.5 4.5±0.5 Example 3 1.2±0.2 3.9±0.3 95.3±1.0 1.8±0.3 Example 4 0.6±0.1 4.6±0.3 87.0±1.8 5.2±0.6 Comparative Example 1 0.9±0.2 3.8±0.5 68.5±3.2 18.5±2.1 Comparative Example 2 3.8±0.5 2.1±0.3 89.2±1.5 2.8±0.4 Comparative Example 3 1.2±0.3 3.5±0.5 72.3±4.5 21.2±3.5 Comparative Example 4 1.5±0.3 2.8±0.4 58.2±5.1 25.8±3.2 Comparative Example 5 2.8±0.4 2.5±0.4 82.5±2.3 4.1±0.5 Comparative Example 6 5.2±0.8 1.3±0.2 90.1±1.8 3.5±0.4 Comparative Example 7 8.5±1.2 1.1±0.1 91.5±1.2 3.3±0.4 Comparative Example 8 1.8±0.3 3.2±0.4 78.5±3.2 8.5±1.2

[0188] Data format: mean ± standard deviation; lower LOD is better, higher k' is better, higher retention rate is better, and lower loss rate is better.

[0189] As can be seen from the performance of the examples and comparative examples in Table 1, Examples 1–4 all showed higher selectivity coefficients (k') than the comparative examples. Furthermore, compared to Comparative Examples 1, 3, and 4, which had insufficient chitosan, excessive filler, or insufficient glutaraldehyde, Examples 1–4 exhibited higher 50-cycle response retention and lower 72-hour rinsing membrane mass loss, indicating that the specified ratio window can achieve a balance between recognition performance and membrane integrity. When the chitosan content was reduced to 12 wt% (Comparative Example 1), the detection limit was not significantly affected, but the membrane mass loss rate reached as high as 18.5%, indicating that chitosan, as the film-forming matrix, plays a decisive role in the membrane's resistance to flow-through erosion. Insufficient magnetic core-shell molecular imprinted particles (Comparative Example 2) significantly increased the detection limit to 3.8 μg / L, with the imprinted particles being the main recognition carrier. Excessive filler (Comparative Example 3) led to film formation defects and membrane detachment, with a membrane loss rate exceeding 21%, verifying the existence of the optimal ratio window. Insufficient glutaraldehyde (Comparative Example 4) resulted in a cycle retention rate of only 58.2%, with severe swelling and loss of the membrane layer. Excessive glutaraldehyde (Comparative Example 5) led to decreased accessibility of the imprinted sites, deteriorating both the detection limit and selectivity. Replacing cyclodextrin methacrylate with methacrylic acid (Comparative Example 6) caused the selectivity coefficient to plummet to 1.3. Non-imprinted particles (Comparative Example 7) exhibited the highest detection limit and the lowest selectivity, demonstrating that the synergistic relationship between cyclodextrin cavity host-guest recognition and molecular imprinting design determines the material's high sensitivity and high selectivity detection capability. Omitting the silica interlayer (Comparative Example 8) weakened the interfacial bonding between the imprinted shell and the magnetic core, resulting in simultaneous deterioration of membrane stability and recognition performance, confirming the overall necessity of the core-shell structure design.

[0190] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A material for online detection of 1,2,4-trichlorobenzene, characterized in that, The online detection material is a film-forming sensitive layer material that can be coated on the surface of the transducer, and comprises, based on the total mass of the online detection material after drying: Chitosan 20–80 wt% The content, calculated as glutaraldehyde, is 0.1–5 wt%; The magnetic core-shell molecularly imprinted particles comprise 15–75 wt%, and the sum of the mass fractions of the above three components does not exceed 100 wt%. The magnetic core-shell molecularly imprinted particles comprise a magnetic core, a silica intermediate layer, and a molecularly imprinted polymer shell; the magnetic core is iron(III) oxide; the silica intermediate layer is silica; the molecularly imprinted polymer shell comprises a polymer network formed by copolymerization of cyclodextrin methacrylate and ethylene glycol dimethacrylate; the cyclodextrin methacrylate is β-cyclodextrin methacrylate or γ-cyclodextrin methacrylate, and the degree of substitution (DS) of the cyclodextrin methacrylate is 0.05–0.30; The magnetic core-shell molecularly imprinted particles are prepared through the following steps: C1. Preparation of prepolymer solution: 1,2,4-trichlorobenzene was added to ethanol as a template molecule, along with cyclodextrin methacrylate and ethylene glycol dimethacrylate, so that the mass ratio of cyclodextrin methacrylate to ethylene glycol dimethacrylate was 1:2–1:20, and the total mass ratio of 1,2,4-trichlorobenzene to cyclodextrin methacrylate and ethylene glycol dimethacrylate was 0.01:1–0.5:1; the total mass fraction of cyclodextrin methacrylate and ethylene glycol dimethacrylate in ethanol was 1–30 wt%; after mixing, the components were stirred and pre-incubated at room temperature for 1–2 h. C2. Surface polymerization: Magnetic silica silanized particles are added to the prepolymer solution described in C1, such that the mass ratio of the magnetic silica silanized particles to the total mass of cyclodextrin methacrylate and ethylene glycol dimethacrylate in C1 is 0.2:1–5:

1. Azobisisobutyronitrile is added as an initiator, such that the amount of initiator is 0.2–2 wt% of the total mass of cyclodextrin methacrylate and ethylene glycol dimethacrylate in C1. The reaction is carried out at 55–70 °C for 6–24 h under a nitrogen inert atmosphere to obtain core-shell particles containing template molecules. C3. Elution and post-treatment: Wash and elute the template molecules with ethanol 3–10 times until no more than 0.10 wt% of 1,2,4-trichlorobenzene remains in the particles, and then dry to obtain magnetic core-shell molecularly imprinted particles; C4. Quality control: The thickness of the molecularly imprinted polymer shell is 3–30 nm; The film-forming sensitive layer material is prepared through the following steps: D1. Film-forming solution: Dissolve chitosan in an aqueous solution containing glacial acetic acid, such that the mass fraction of glacial acetic acid is 0.5–2 wt% and the mass fraction of chitosan is 0.5–3 wt%, and stir until dissolved; D2. Compounding: Add magnetic core-shell molecularly imprinted particles to achieve a mass fraction of 15–75 wt% in the dry film; D3. Crosslinking film formation: Add glutaraldehyde aqueous solution to make the content of glutaraldehyde 0.1–5 wt%, coat the mixture on the surface of the transducer substrate and cure at 20–60 °C for 0.5–12 h; D4. Post-treatment and quality control: After curing, wash with deionized water and ethanol in sequence and dry. The resulting dry film thickness is 1–100 μm and the residual glutaraldehyde is no more than 0.5 wt%.

2. The online detection material according to claim 1, characterized in that, The cyclodextrin methacrylate is prepared by the following steps: A1. Raw material preparation: Dissolve β-cyclodextrin or γ-cyclodextrin in dimethyl sulfoxide to make the cyclodextrin mass fraction 5–20 wt%; add potassium carbonate, the amount of which is 0.05–0.50 times the molar amount of cyclodextrin; A2. Reaction: Under a nitrogen inert atmosphere, glycidyl methacrylate containing p-methoxyphenol polymerization inhibitor is added dropwise to the solution at a rate of 1–5 mL / min, so that the molar ratio of glycidyl methacrylate to cyclodextrin is 0.2:1–2.0:1, and the reaction is carried out at 40–70 °C for 6–24 h. A3. Post-treatment: After filtering the reaction solution to remove inorganic salts, ethanol is added as a precipitant to precipitate the product. The mass ratio of ethanol to reaction solution is 3:1–20:

1. The precipitate is washed with ethanol 1–5 times and dried at 40–60 °C for 6–24 h. A4. Endpoint Criteria and Quality Control: The degree of substitution (DS) of the obtained cyclodextrin methacrylate is 0.05–0.30, and the residual dimethyl sulfoxide is not greater than 1.0 wt%.

3. The online detection material according to claim 1, characterized in that, The magnetic silica silanized particles used to prepare the magnetic core-shell molecularly imprinted particles are prepared by the following steps: B1. Preparation of magnetic cores: Ferric chloride hexahydrate and ferrous chloride tetrahydrate were dissolved in deionized water to make the molar ratio of ferric to ferrous iron 1.8:1–2.2:1 and the total concentration of iron salts 0.1–0.5 mol / L; the temperature was raised to 60–85 °C under a nitrogen inert atmosphere, and ammonium hydroxide solution was added dropwise to adjust the pH to 9–11. The reaction was maintained at this temperature for 0.5–2 h; the resulting magnetic particles were magnetically separated and washed with deionized water until the pH of the washing solution was 7–8. B2. Silica Coating: The magnetic particles obtained in B1 are dispersed at a concentration of 2–20 mg / mL in a mixed solvent of ethanol and deionized water, wherein the volume ratio of ethanol to deionized water is 3:1–10:1; ammonium hydroxide solution is added to adjust the pH to 9–11, and tetraethyl silicate is added. The mixture is reacted at 20–40 °C for 4–24 h to obtain silica-coated magnetic particles. B3. Silanization: The particles obtained in B2 are dispersed at a concentration of 10–50 mg / mL in ethanol containing 1–5% deionized water by volume. 3-Methacryloxypropyltrimethoxysilane and 3-aminopropyltriethoxysilane are added, with the total amount of the two being 1–10 wt% of the particle mass, and the mass ratio of 3-methacryloxypropyltrimethoxysilane to 3-aminopropyltriethoxysilane being 1:9–9:

1. The reaction is carried out at 25–60 °C for 1–8 h. B4. Endpoint Criteria and Quality Control: The D50 of the obtained magnetic silica silanized particles is 80–240 nm, and the magnetic response time is not greater than 30 s.

4. The online detection material according to claim 1, characterized in that, The magnetic core-shell molecularly imprinted particles contain 30–70 wt% iron oxide and have a D50 of 100–250 nm.

5. A method for preparing an online detection material for 1,2,4-trichlorobenzene as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Provides cyclodextrin methacrylate; S2. Provides magnetic silica silanized particles; S3. Provides magnetic core-shell molecularly imprinted particles; S4. Dissolve chitosan in an aqueous solution containing glacial acetic acid to obtain a film-forming solution; S5. Add the magnetic core-shell molecularly imprinted particles to the film-forming solution, and add glutaraldehyde to crosslink and form a film, thereby obtaining 1,2,4-trichlorobenzene online detection material.

6. The preparation method according to claim 5, characterized in that, The degree of substitution (DS) of the cyclodextrin methacrylate provided in step S1 is 0.05–0.30, and the residual dimethyl sulfoxide is no more than 1.0 wt%.

7. The preparation method according to claim 5, characterized in that, In step S4, the mass fraction of glacial acetic acid is 0.5–2 wt%, and the mass fraction of chitosan is 0.5–3 wt%. In step S5, the mass fraction of the magnetic core-shell molecularly imprinted particles in the dry film is 15–75 wt%, the content of glutaraldehyde is 0.1–5 wt%, the curing temperature is 20–60 ℃ and the curing time is 0.5–12 h, the thickness of the resulting dry film is 1–100 μm, and the residual glutaraldehyde is no more than 0.5 wt%.

8. The preparation method according to claim 5, characterized in that, The molecularly imprinted polymer shell thickness of the magnetic core-shell molecularly imprinted particles provided in step S3 is 3–30 nm, and the residual 1,2,4-trichlorobenzene in the particles is no more than 0.10 wt%.

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