Polycyclic aromatic hydrocarbon trace detection method of in-situ molecularly imprinted photoelectric electrode

Abstract

The invention relates to the technical field of environmental pollutant detection, in particular to a polycyclic aromatic hydrocarbon trace detection method of an in-situ molecular imprinting photoelectric electrode. The method comprises the following steps: preparing a substrate electrode loaded with a photoelectric active composite material, proportionally mixing polycyclic aromatic hydrocarbon template molecules, a photoelectric active functional monomer, a cross-linking agent and an initiator to form a polymerization system, and constructing a molecularly imprinted membrane on the surface of the substrate electrode through in-situ polymerization to obtain the in-situ molecularly imprinted photoelectric electrode. The electrode is used as a working electrode, the working electrode, a reference electrode and a counter electrode form a three-electrode system, the three-electrode system is immersed into a sample solution containing polycyclic aromatic hydrocarbon to be detected, constant bias voltage is applied, specific wavelength optical excitation is carried out, and trace quantitative detection of the polycyclic aromatic hydrocarbon is realized by detecting the change of a photoelectric response signal. According to the invention, molecular imprinting sites are tightly combined with a photoelectric active layer through in-situ polymerization, and the sensitivity and selectivity of detection are remarkably improved by combining the synergistic interaction of a photoelectric active composite material.

Description

Technical Field

[0001] This invention relates to the field of environmental pollutant detection technology, specifically to a method for detecting trace amounts of polycyclic aromatic hydrocarbons using in-situ molecularly imprinted photoelectrodes. Background Technology

[0002] Polycyclic aromatic hydrocarbons (PAHs) are a class of aromatic hydrocarbon compounds composed of two or more benzene rings arranged linearly, angularly, or in clusters. They mainly originate from human activities such as fossil fuel combustion, industrial production, and waste incineration, and are also present in everyday environments such as tobacco smoke and barbecued foods. PAHs are highly carcinogenic, teratogenic, and mutagenic. Benzo[a]pyrene, among others, has been classified as a Group 1 carcinogen by the International Agency for Research on Cancer. Their residues in the environment can enter the human body through inhalation and ingestion, posing a serious threat to human health. Therefore, establishing highly sensitive and selective methods for the trace detection of PAHs is of great significance for environmental monitoring, food safety supervision, and the protection of human health.

[0003] Currently, the main methods for detecting PAHs include instrumental analysis methods such as high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS / MS). These methods offer advantages such as high detection accuracy and good separation, but they also have significant limitations: First, the instruments are expensive, bulky, complex to operate, and have high maintenance costs, making rapid on-site detection difficult; second, sample pretreatment is cumbersome, requiring multiple steps such as extraction, concentration, and purification, which is time-consuming, labor-intensive, and prone to sample loss and contamination; third, the detection process requires the use of large amounts of organic solvents, increasing detection costs and causing secondary environmental pollution. Therefore, developing trace detection methods that require no complex pretreatment, are easy to operate, and are low-cost has become a research hotspot in the field of PAH detection.

[0004] Photoelectrochemical detection technology, based on the photoelectric conversion properties of substances, achieves analytical detection by detecting changes in electrochemical signals under photoexcitation. It boasts advantages such as high sensitivity, rapid response, and simple instrumentation, showing broad application prospects in trace analysis. However, traditional photoelectrochemical sensors suffer from poor selectivity, and complex matrix components in environmental samples can easily interfere with the detection signal, leading to decreased detection accuracy and limiting their application in practical sample detection. Molecular imprinting (MIT) is a technique for preparing polymers with specific recognition sites (MIPs). Through the interaction between template molecules and functional monomers, the template molecules are removed after cross-linking polymerization, forming an imprint cavity complementary to the spatial structure and binding sites of the template molecules. This technique features strong specific recognition capabilities, good stability, and low preparation cost. Combining molecular imprinting technology with photoelectrochemical detection technology to prepare molecularly imprinted photoelectrodes can achieve highly selective recognition and high-sensitivity detection of target analytes, providing a new approach for trace detection of PAHs.

[0005] However, existing methods for preparing and detecting molecularly imprinted photoelectrodes still have many technical shortcomings: First, most methods use offline polymerization to prepare molecularly imprinted films and then transfer them to the surface of the photoelectrode, resulting in weak bonding between the imprinted film and the electrode substrate, making them prone to detachment. Furthermore, the electron transport path between the imprinted sites and the photoactive layer is obstructed, affecting photoelectric response efficiency. Second, existing photoactive materials are mostly single-component, with narrow light absorption ranges, high electron-hole recombination rates, and limited photoelectric conversion efficiency, making it difficult to meet the sensitivity requirements for detecting trace PAHs. Third, existing molecular imprinting systems mostly use single template molecules, enabling the detection of only one type of PAH. However, real-world environmental samples often contain multiple PAHs, making simultaneous detection of multiple components impossible. In addition, some methods have poorly designed imprinting polymerization systems, resulting in weak interactions between functional monomers and template molecules, leading to insufficient specific recognition of imprinted sites and susceptibility to interference from structurally similar interfering substances.

[0006] To address the shortcomings of existing technologies, there is an urgent need to develop a method that features strong bonding between the imprinted film and electrode, high photoelectric conversion efficiency, strong selectivity, and efficient detection of trace PAHs, in order to solve the problems of complex operation and low sensitivity of existing detection methods. Poor selectivity and inability to meet the requirements of multi-component detection have driven the practical application of PAH trace detection technology. Summary of the Invention

[0007] The purpose of this invention is to overcome the technical shortcomings of existing methods for detecting trace amounts of polycyclic aromatic hydrocarbons (PAHs), such as complex operation, low sensitivity, poor selectivity, weak bonding between the imprinted film and the electrode, and inability to simultaneously detect multiple components. This invention provides an in-situ molecularly imprinted photoelectrode method for detecting trace amounts of PAHs. This method directly prepares a molecularly imprinted film on the surface of a photoelectrode substrate through in-situ polymerization. Combined with the synergistic effect of photoelectroactive composite materials, it significantly improves the sensitivity and selectivity of the detection, enabling rapid detection of single or multiple PAHs in trace amounts.

[0008] The technical solution adopted by this invention to solve its technical problem is: a method for detecting trace amounts of polycyclic aromatic hydrocarbons using an in-situ molecularly imprinted photoelectrode, comprising the following steps: Step (1) Preparation of photoelectric substrate electrode: Select a conductive substrate, clean and activate it in sequence, coat the surface of the conductive substrate with the photoelectric active composite material dispersion, and obtain the photoelectric substrate electrode by drying and calcination; The photoelectric active composite material is a composite system of quantum dots and two-dimensional layered materials, wherein the quantum dots are selected from at least one of TiO2, CdS and ZnO, and the two-dimensional layered materials are selected from at least one of MoS2, WS2 and black phosphorus; Step (2) Preparation of in-situ molecularly imprinted film: Polycyclic aromatic hydrocarbon template molecules, photoactive functional monomers, crosslinking agents and initiators are dissolved in a solvent and ultrasonically dispersed to form a uniform polymerization system; the photoelectric substrate electrode prepared in step (1) is immersed in the polymerization system, and in-situ polymerization reaction is carried out under the protection of inert gas by photoinitiation or thermal initiation. After the reaction is completed, the template molecules are removed by elution to obtain the in-situ molecularly imprinted photoelectric electrode; Step (3) Trace detection of polycyclic aromatic hydrocarbons: The in-situ molecularly imprinted photoelectrode is used as the working electrode, the saturated calomel electrode is used as the reference electrode, and the platinum wire is used as the counter electrode to form a three-electrode system; the three-electrode system is immersed in the sample solution containing the polycyclic aromatic hydrocarbons to be tested, electrolyte is added to adjust the conductivity of the solution, a constant bias voltage of 0.2~0.8V is applied, and visible light or ultraviolet light with a wavelength of 300~500nm is used for continuous excitation. The photoelectric response current signal is collected by an electrochemical workstation, and the trace quantitative detection of polycyclic aromatic hydrocarbons is realized according to the linear relationship between the signal intensity and the concentration of polycyclic aromatic hydrocarbons.

[0009] Specifically, the conductive substrate in step (1) is ITO conductive glass, fluorine-doped tin oxide conductive glass or gold electrode. The cleaning process includes ultrasonic cleaning with acetone, ethanol and deionized water for 15-30 min in sequence. The activation process is cyclic voltammetric activation in 0.5-1 mol / L sulfuric acid solution.

[0010] Specifically, the preparation method of the photoelectric active composite material in step (1) is as follows: the two-dimensional layered material is dispersed in deionized water, a quantum dot precursor is added, and a hydrothermal reaction is carried out at 120~180℃ for 6~12h. After cooling, the material is centrifuged, washed, and dried to obtain the final product. The mass ratio of quantum dots to two-dimensional layered material is 1:2~1:5.

[0011] Specifically, the polycyclic aromatic hydrocarbon template molecule in step (2) is selected from one or more of benzo[a]pyrene, fluoranthene, pyrene, and benzo[b]fluoranthene, and the molar ratio of the template molecule to the photoelectric active functional monomer is 1:4 to 1:8.

[0012] Specifically, the photoactive functional monomer in step (2) is o-phenylenediamine, m-aminophenol or p-aminobenzoic acid, the crosslinking agent is ethylene glycol dimethacrylate or N,N'-methylenebisacrylamide, and the initiator is azobisisobutyronitrile or 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0013] Specifically, the in-situ polymerization reaction conditions in step (2) are as follows: when photo-initiated, irradiate with 254~365nm ultraviolet light for 2~4h; when thermally initiated, react at 60~80℃ for 4~6h; the elution treatment uses a mixed solution of methanol and acetic acid as the eluent, with a volume ratio of 9:1~8:2, and the elution time is 12~24h.

[0014] Specifically, the electrolyte in step (3) is a 0.05~0.2mol / L phosphate buffer solution or potassium chloride solution, and the pH value of the solution is adjusted to 6.0~8.0.

[0015] Specifically, in step (3), the light power density of photoexcitation is 50~100mW / cm2, the signal acquisition time is 10~30s, and the detection linear range is 10-12~10-6mol / L.

[0016] Specifically, the sample solution is an environmental water sample, soil extract, or food extract. The sample solution is directly used for detection after being filtered through a 0.22μm filter membrane, without the need for additional concentration treatment.

[0017] Specifically, when there are multiple template molecules, the molar ratio of the multiple template molecules is 1:1 to 1:3, and the corresponding detection method can simultaneously achieve quantitative analysis of multiple polycyclic aromatic hydrocarbons.

[0018] The beneficial effects of this invention are: The imprinted film is firmly bonded to the electrode, resulting in high electron transport efficiency: This invention uses in-situ polymerization to directly prepare a molecularly imprinted film on the surface of a photoelectric substrate electrode. The imprinted film forms a chemical bond with the electrode substrate, resulting in a tight bond that is not easily detached, thus solving the problem of easy detachment of imprinted films prepared offline in traditional methods. At the same time, the imprinted film is in direct contact with the photoelectric active layer, which shortens the electron transport path, reduces electron transport resistance, and significantly improves photoelectric response efficiency.

[0019] High photoelectric conversion efficiency and excellent detection sensitivity: This invention uses a photoelectric active composite material composed of quantum dots and two-dimensional layered materials. Quantum dots have a wide absorption spectrum and high photoelectric conversion efficiency, while two-dimensional layered materials have a large specific surface area and high electron mobility. The synergistic effect of the two can effectively broaden the light absorption range, suppress electron-hole recombination, and significantly improve the photoelectric conversion efficiency. Combined with the specific enrichment effect of molecularly imprinted membranes, the detection limit is as low as 10-12 mol / L, which is far superior to existing detection methods.

[0020] High selectivity and outstanding anti-interference ability: This invention selects photoelectric active functional monomers that have strong interactions with polycyclic aromatic hydrocarbon template molecules. Through hydrogen bonding, π-π stacking and other interactions between template molecules and functional monomers, specific recognition sites are formed. The in-situ polymerization process ensures that the spatial structure of the imprinted site is highly matched with the template molecule, which has a very strong specific recognition ability for target polycyclic aromatic hydrocarbons. The response signal to structurally similar interfering substances (such as monocyclic aromatic hydrocarbons, aliphatic hydrocarbons, etc.) is less than 5%, and the anti-interference ability is significantly better than that of traditional photoelectric sensors.

[0021] This invention enables simultaneous detection of multiple components and has a wide range of applications: It can use various polycyclic aromatic hydrocarbons (PAHs) as composite template molecules, forming multiple specific imprint sites on the electrode surface through in-situ polymerization. Combined with the characteristic photoelectric response signals corresponding to different PAHs, it can simultaneously achieve quantitative detection of multiple PAHs without the need for separate detection, thus improving detection efficiency. At the same time, this method has low requirements for sample pretreatment. Environmental water samples, soil extracts, food extracts, etc. can be detected after simple filtration, making it widely applicable.

[0022] Simple to operate, fast and stable, and low cost: The detection process of this invention does not require complex sample pretreatment, the three-electrode system is easy to assemble, and the detection process can complete signal acquisition in only 10~30s; the electrodes have good stability, and the photoelectric response signal decay is less than 8% after 20 cycles of use; the materials used are inexpensive, the preparation process is simple, and it is easy to mass-produce, making it suitable for rapid on-site detection and routine monitoring applications. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] Figure 1The flowchart illustrates the method for detecting trace amounts of polycyclic aromatic hydrocarbons using an in-situ molecularly imprinted photoelectrode provided by this invention. Detailed Implementation

[0025] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0026] like Figure 1 As shown, the method for detecting trace amounts of polycyclic aromatic hydrocarbons (PAHs) using an in-situ molecularly imprinted photoelectrode according to the present invention includes three steps: preparation of the photoelectrode substrate electrode, preparation of the in-situ molecularly imprinted film, and detection of trace PAHs, as detailed below: Step 1: Fabrication of photoelectric substrate electrode Select a conductive substrate (ITO conductive glass, fluorine-doped tin oxide conductive glass, or gold electrode), and ultrasonically clean it sequentially with acetone, ethanol, and deionized water for 15-30 minutes each to remove surface oil and impurities. Immerse the cleaned conductive substrate in a 0.5-1 mol / L sulfuric acid solution and activate it by scanning cyclic voltammetry in the potential range of -0.2-1.0 V for 10-20 cycles to enhance the hydrophilicity and conductivity of the electrode surface.

[0027] Preparation of photoelectric active composite material: Two-dimensional layered material (at least one of MoS2, WS2, and black phosphorus) is dispersed in deionized water and ultrasonically dispersed for 30-60 min to form a dispersion with a concentration of 0.5-2 mg / mL; a quantum dot precursor (the corresponding precursor of tetrabutyl titanate, cadmium chloride, or zinc acetate) is added at a mass ratio of quantum dots to two-dimensional layered material of 1:2-1:5, and after stirring evenly, it is transferred to a hydrothermal reactor and reacted at 120-180℃ for 6-12 h; after the reaction is completed, it is naturally cooled to room temperature, centrifuged (8000-12000 r / min, 10-15 min), and the precipitate is washed 3-5 times alternately with deionized water and ethanol, and vacuum dried at 60-80℃ for 6-12 h to obtain the photoelectric active composite material of quantum dot-two-dimensional layered material.

[0028] The above-mentioned photoelectric active composite material was dispersed in deionized water and ultrasonically dispersed for 20-40 min to form a dispersion with a concentration of 1-3 mg / mL. The dispersion was coated onto the surface of the activated conductive substrate by drop coating or spin coating, with a drop coating amount of 5-10 μL / cm2, a spin coating speed of 3000-5000 r / min, and a time of 30-60 s. After coating, the substrate was dried at 100-120℃ for 1-2 h, then calcined at 300-400℃ for 2-4 h, and cooled to room temperature to obtain the photoelectric substrate electrode.

[0029] Step 2: Preparation of in-situ molecularly imprinted membranes Select one or more of polycyclic aromatic hydrocarbon template molecules (benzo[a]pyrene, fluoranthene, pyrene, benzo[b]fluoranthene, with a molar ratio of multiple template molecules of 1:1 to 1:3), add photoactive functional monomers (o-phenylenediamine, m-aminophenol, or p-aminobenzoic acid) at a molar ratio of template molecule to photoactive functional monomer of 1:4 to 1:8; add crosslinking agent (ethylene glycol dimethacrylate or N,N'-methylenebisacrylamide), with a molar ratio of crosslinking agent to functional monomer of 1:1 to 1:3; add initiator (azobisisobutyronitrile or 2-hydroxy-2-methyl-1-phenyl-1-propanone), with the amount of initiator being 1% to 3% of the mass of functional monomer; dissolve the above mixture in a solvent (methanol, acetonitrile, or a mixture of water and acetonitrile, with a volume ratio of 1:1 to 3:1), and ultrasonically disperse for 10 to 20 minutes to form a homogeneous polymerization system.

[0030] The photoelectric substrate electrode prepared in step 1 is immersed in the above polymerization system, and the electrode surface is in full contact with the polymerization system. Inert gas such as nitrogen or argon is introduced into the reaction system for 30-60 minutes to remove oxygen from the system. Then, in-situ polymerization reaction is carried out. For photoinitiation, 254-365 nm ultraviolet light is used for 2-4 hours, and for thermal initiation, the reaction is carried out at 60-80℃ for 4-6 hours.

[0031] After the polymerization reaction is completed, the electrode is removed and soaked and washed with an eluent (a mixed solution of methanol and acetic acid, volume ratio 9:1~8:2) for 12~24 hours, during which the eluent is replaced 3~5 times to completely remove the template molecules in the imprinted film on the electrode surface; after elution, the electrode surface is rinsed with deionized water and vacuum dried at 60~80℃ for 2~4 hours to obtain a photoelectrode with an in-situ molecular imprinted film modified on the surface.

[0032] Step 3: Detection of trace polycyclic aromatic hydrocarbons The above-mentioned in-situ molecularly imprinted photoelectrode was used as the working electrode, the saturated calomel electrode as the reference electrode, and the platinum wire as the counter electrode to assemble a three-electrode system. The three-electrode system was immersed in a sample solution containing the polycyclic aromatic hydrocarbon to be tested. The sample solution was an environmental water sample, soil extract, or food extract. It was used directly after being filtered through a 0.22 μm filter membrane without additional concentration.

[0033] Add an electrolyte (0.05~0.2mol / L phosphate buffer solution or potassium chloride solution) to the sample solution, adjust the pH value of the solution to 6.0~8.0, and stir evenly to make the solution concentration uniform; apply a constant bias voltage of 0.2~0.8V to the three-electrode system through an electrochemical workstation, and continuously excite it with visible light or ultraviolet light with a wavelength of 300~500nm, with a light power density of 50~100mW / cm2.

[0034] After the photoelectric response current signal stabilizes, the current intensity value is recorded. Based on the pre-plotted standard curve (with the concentration of polycyclic aromatic hydrocarbon standard solution as the abscissa and the corresponding photoelectric response current change value as the ordinate), the concentration of polycyclic aromatic hydrocarbons in the sample solution is calculated. When there are multiple template molecules, the simultaneous quantitative detection of multiple polycyclic aromatic hydrocarbons is achieved by identifying the characteristic response potential or signal peak shape corresponding to different template molecules.

[0035] Example 1: Trace Detection of Benzo[a]pyrene Experimental materials and instruments Conductive substrate: ITO conductive glass (size 20mm×10mm×1.1mm, sheet resistance ≤10Ω / □); Two-dimensional layered material: MoS2 powder (purity ≥99%, particle size 50~100nm); Quantum dot precursor: Tetrabutyl titanate (analytical grade). Template molecule: benzo[a]pyrene (purity ≥98%); photoactive functional monomer: o-phenylenediamine (analytical grade); crosslinking agent: ethylene glycol dimethacrylate (analytical grade); initiator: 2-hydroxy-2-methyl-1-phenyl-1-propanone (analytical grade); solvent: acetonitrile (chromatographic grade); eluent: methanol (chromatographic grade), acetic acid (analytical grade); electrolyte: potassium dihydrogen phosphate, disodium hydrogen phosphate (both analytical grade); benzo[a]pyrene standard (purity ≥99.5%); experimental water was ultrapure water (resistivity ≥18.2 MΩ·cm).

[0036] Instruments: Electrochemical workstation (CHI660E); Ultrasonic cleaner (KQ-500DE); Vacuum drying oven (DZF-6050); Muffle furnace (SX2-4-10); Hydrothermal reactor (50mL, PTFE liner); Ultraviolet lamp (254nm, 30W); Ultraviolet-Vis spectrophotometer (UV-2550); Scanning electron microscope (SEM, SU8010).

[0037] Fabrication of photoelectric substrate electrodes ITO conductive glass was cut into 20mm×10mm pieces and ultrasonically cleaned sequentially with acetone, ethanol, and ultrapure water for 20 minutes each to remove surface oil and impurities. The cleaned ITO glass was then immersed in a 0.8mol / L sulfuric acid solution and activated by cyclic voltammetry at a scanning rate of 50mV / s for 15 cycles within a potential range of -0.2 to 1.0V. After activation, the glass was rinsed with ultrapure water and dried with nitrogen gas for later use.

[0038] Preparation of TiO2 quantum dot-MoS2 composite photoelectric active material: Weigh 0.2g of MoS2 powder, add 100mL of ultrapure water, and ultrasonically disperse for 40min to form a MoS2 dispersion with a concentration of 2mg / mL; weigh 0.08g of tetrabutyl titanate (TiO2 quantum dot precursor), slowly add it dropwise to the above dispersion, and magnetically stir for 30min; transfer the mixture to a 50mL hydrothermal reactor and react at 160℃ for 8h; after the reaction, allow it to cool naturally to room temperature, centrifuge at 10000r / min for 12min, and collect the precipitate; wash the precipitate four times alternately with ultrapure water and ethanol to remove unreacted precursors and impurities; dry the precipitate in a vacuum drying oven at 70℃ for 8h to obtain TiO2 quantum dot-MoS2 composite photoelectric active material, wherein the mass ratio of TiO2 quantum dots to MoS2 is 1:2.5.

[0039] Weigh 50 mg of the above-mentioned composite photoelectric active material, add 20 mL of ultrapure water, and ultrasonically disperse for 30 min to form a dispersion with a concentration of 2.5 mg / mL. Use a drop-coating method to uniformly coat the dispersion onto the activated ITO glass surface, with a drop-coating amount of 8 μL / cm2 to ensure that the effective working area of ​​the electrode is 1 cm2. After coating, place the electrode in a drying oven at 110℃ for 1.5 h, and then place it in a muffle furnace and calcine at 350℃ for 3 h. After natural cooling to room temperature, a TiO2 quantum dot-MoS2 composite photoelectric substrate electrode is obtained.

[0040] Preparation of in situ molecularly imprinted membranes Weigh 0.05 mmol of benzo[a]pyrene template molecule and add it to a 50 mL beaker. Add 0.3 mmol of o-phenylenediamine functional monomer, then add 0.15 mmol of ethylene glycol dimethacrylate crosslinking agent, and finally add 0.005 g of initiator 2-hydroxy-2-methyl-1-phenyl-1-propanone. Add 20 mL of acetonitrile solvent to the beaker, sonicate for 15 min, and stir until homogeneous to form a uniform and transparent polymerization system.

[0041] The photoelectric substrate electrode prepared above was immersed in the polymerization system to ensure that the electrode surface was completely covered by the polymerization liquid; nitrogen gas was introduced into the beaker for 30 minutes to remove oxygen from the system and prevent oxygen from inhibiting the polymerization reaction; then the beaker was placed under a 254nm ultraviolet lamp at a distance of 10 cm from the light source and irradiated for 3 hours to carry out the in-situ polymerization reaction.

[0042] After the polymerization reaction was completed, the electrode was removed and immersed in an eluent with a methanol to acetic acid volume ratio of 8:2 for 18 hours. The eluent was replaced every 6 hours to ensure complete removal of the benzo[a]pyrene template molecules from the imprinted membrane. After elution, the electrode surface was rinsed three times with ultrapure water to remove residual eluent. The electrode was then dried in a vacuum drying oven at 70°C for 3 hours to obtain the benzo[a]pyrene in-situ molecularly imprinted photoelectrode.

[0043] The surface morphology of the electrode was characterized by SEM. The results showed that a uniform and dense molecularly imprinted film was formed on the electrode surface with a thickness of about 100~150nm. The film was tightly bonded to the electrode substrate and there was no peeling. The UV-Vis spectrophotometry test showed that the electrode had strong light absorption in the range of 300~450nm, indicating that the photoelectric active composite material and the molecularly imprinted film worked together to effectively absorb the excitation light.

[0044] Detection of trace benzo[a]pyrene Preparation of benzo[a]pyrene standard solution: Accurately weigh 0.0128 g of benzo[a]pyrene standard, dissolve it in acetonitrile and dilute to 10 mL to obtain a 1×10-3 mol / L standard stock solution; then gradually dilute with ultrapure water to obtain a series of standard working solutions with concentrations of 1×10-12 mol / L, 1×10-11 mol / L, 1×10-10 mol / L, 1×10-9 mol / L, 1×10-8 mol / L, 1×10-7 mol / L and 1×10-6 mol / L.

[0045] Using the prepared in-situ molecularly imprinted photoelectrode as the working electrode, the saturated calomel electrode as the reference electrode, and the platinum wire as the counter electrode, a three-electrode system was assembled. The three-electrode system was then immersed in the above-mentioned benzo[a]pyrene standard working solutions of different concentrations. 0.1 mol / L phosphate buffer solution (pH=7.0) was added to each solution as an electrolyte, and the mixture was stirred until homogeneous.

[0046] A constant bias voltage of 0.5V was applied to the three-electrode system using an electrochemical workstation, and visible light with a wavelength of 400nm was used for excitation with a light power density of 80mW / cm2. After the photoelectric response current signal stabilized, the current intensity values ​​corresponding to each concentration were recorded. A standard curve was plotted with the logarithm of the benzo[a]pyrene concentration as the abscissa and the corresponding photoelectric response current change value as the ordinate.

[0047] The results showed that the concentration of benzo[a]pyrene exhibited a good linear relationship with the change in photoelectric response current in the range of 1×10-12 to 1×10-6 mol / L. The linear regression equation was I(μA) = 2.35logC(mol / L) + 32.68, and the correlation coefficient R2 = 0.9987. The detection limit of the method (S / N=3) was 3.2×10-13 mol / L, indicating that the method has extremely high detection sensitivity.

[0048] Aromatic compounds with similar structures, such as naphthalene, phenanthrene, and anthracene, were selected as interfering agents. Interfering agent solutions with a concentration of 1×10⁻⁷ mol / L were prepared, and the detection method described above was used for testing, recording the changes in response current. The results showed that the current change corresponding to the interfering agents was only 2.1%–4.8% of that of benzo[a]pyrene at the same concentration, indicating that this method has extremely strong specific recognition ability for benzo[a]pyrene and outstanding anti-interference ability.

[0049] Six parallel assays were performed on a standard solution of benzo[a]pyrene with the same concentration (1×10-9 mol / L), and the relative standard deviation (RSD) was 2.3%, indicating that the method has good repeatability. After storing the electrode in a desiccator for 30 days, the current signal attenuation was only 4.5% when the same concentration standard solution was tested, indicating that the electrode has good stability.

[0050] Actual environmental water samples (surface water from a river) were collected and filtered through a 0.22 μm filter membrane. Spiking recovery experiments were then conducted using the method described above. Benzo[a]pyrene standards at low, medium, and high concentrations were added, with each concentration level analyzed in triplicate. The spiked recoveries were calculated. The results showed recoveries ranging from 92.5% to 103.8%, with RSDs ranging from 1.8% to 3.1%, indicating that this method is suitable for trace detection of benzo[a]pyrene in actual water samples, and the results are accurate and reliable.

[0051] Example 2: Simultaneous detection of benzo[a]pyrene, fluoranthene, and pyrene Experimental Materials and Instruments: The materials and instruments used in this embodiment are the same as those in Example 1, except that the template molecules are benzo[a]pyrene, fluoranthene, and pyrene (molar ratio 1:1:1).

[0052] The preparation method of the photoelectric substrate electrode in this embodiment is completely consistent with that in Example 1, that is, the photoelectric substrate electrode is prepared by modifying ITO conductive glass with TiO2 quantum dot-MoS2 composite photoelectric active material.

[0053] Preparation of in-situ molecularly imprinted membrane: Weigh 0.03 mmol benzo[a]pyrene, 0.03 mmol fluoranthene, and 0.03 mmol pyrene as composite template molecules and add them to a 50 mL beaker; add 0.54 mmol o-phenylenediamine functional monomer (the total molar number of template molecules to the molar ratio of functional monomer is 1:6), then add 0.27 mmol ethylene glycol dimethacrylate crosslinking agent, and add 0.006 g initiator 2-hydroxy-2-methyl-1-phenyl-1-propanone; add 20 mL of a mixed solvent of acetonitrile and water (volume ratio 2:1) to the beaker, ultrasonically disperse for 20 min, stir evenly, and form a homogeneous polymerization system.

[0054] The photoelectric substrate electrode was immersed in the above polymerization system, and nitrogen gas was introduced for 40 minutes to remove oxygen; then it was irradiated under a 254nm ultraviolet lamp for 3.5 hours to carry out the in-situ polymerization reaction.

[0055] After the polymerization reaction was completed, the electrode was immersed in an eluent with a methanol to acetic acid volume ratio of 9:1 and washed for 24 hours, with the eluent being replaced every 8 hours during the process to completely remove the three template molecules. After elution, the electrode was rinsed with ultrapure water and dried under vacuum at 70°C for 3 hours to obtain a benzo[a]pyrene-fluoranthene-pyrene composite in-situ molecularly imprinted photoelectrode.

[0056] SEM characterization showed that the imprinted film on the electrode surface was uniform and dense, with a thickness of approximately 120–180 nm. UV-Vis spectrophotometry showed that the electrode had a wide range of light absorption in the 300–480 nm range, which could effectively absorb excitation light and generate a photoelectric response.

[0057] Simultaneous detection of three polycyclic aromatic hydrocarbons Preparation of mixed standard solutions: Accurately weigh benzo[a]pyrene, fluoranthene, and pyrene standards, dissolve them in acetonitrile and dilute to volume to prepare standard stock solutions with a concentration of 1×10⁻³ mol / L for each substance; then gradually dilute with ultrapure water to prepare a series of mixed standard working solutions, wherein the concentrations of the three substances are 1×10⁻¹² mol / L, 1×10⁻¹¹ mol / L, 1×10⁻¹⁰ mol / L, 1×10⁻⁹ mol / L, 1×10⁻⁸ mol / L, 1×10⁻⁷ mol / L, and 1×10⁻⁶ mol / L, respectively.

[0058] A three-electrode system was assembled using a composite in-situ molecularly imprinted photoelectrode as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum wire as the counter electrode. The three-electrode system was then immersed in a mixed standard working solution, and 0.1 mol / L phosphate buffer solution (pH=7.2) was added as the electrolyte and stirred until homogeneous.

[0059] A linear scanning voltage of 0.3–0.9 V was applied using an electrochemical workstation, and visible light at a wavelength of 420 nm was used for excitation. The optical power density was 90 mW / cm², and the photoelectric response current signals at different potentials were recorded. The results showed that benzo[a]pyrene, fluoranthene, and pyrene exhibited characteristic response peaks at potentials of 0.5 V, 0.65 V, and 0.4 V, respectively, and the peak current intensity of each characteristic peak showed a good linear relationship with the concentration of the corresponding substance.

[0060] Standard curves were plotted with the logarithm of the concentration of the three substances on the x-axis and the corresponding characteristic peak current changes on the y-axis. The linear regression equation for benzo[a]pyrene was I1 (μA) = 2.18logC1 (mol / L) + 31.56, R2 = 0.9978, and the detection limit was 4.1 × 10⁻¹³ mol / L; the linear regression equation for fluoranthene was I2 (μA) = 2.52logC2 (mol / L) + 33.42, R2 = 0.9983, and the detection limit was 3.5 × 10⁻¹³ mol / L; and the linear regression equation for pyrene was I3 (μA) = 2.27logC3 (mol / L) + 30.89, R2 = 0.9981, and the detection limit was 3.8 × 10⁻¹³ mol / L.

[0061] Naphthalene, biphenyl, fluorene, and other interfering substances were selected, and a mixed interfering substance solution with a concentration of 1×10-7 mol / L was prepared. The solution was then tested according to the above method. The results showed that the interfering substances did not have obvious response peaks at the characteristic potentials of the three target substances, and the peak current changes were all less than 5%, indicating that the method has good selectivity for the three target PAHs.

[0062] Actual soil samples were taken, and 10g of soil sample was weighed. 30mL of acetonitrile was added, and the mixture was ultrasonically extracted for 30min. After centrifugation, the supernatant was collected and filtered through a 0.22μm filter membrane to obtain the soil extract. Three target PAHs standards at different concentrations were added to the extract for spiked recovery experiments. The results showed that the recoveries of the three substances ranged from 90.2% to 104.5%, with RSDs of 2.1% to 3.5%, indicating that this method can achieve simultaneous trace detection of multiple PAHs in actual soil samples, and the detection results are accurate and reliable.

[0063] Example 3: Trace Detection of Pyrene in Food Experimental materials and instruments Conductive substrate: gold electrode (3 mm in diameter); two-dimensional layered material: black phosphorus nanosheets (purity ≥99%, layer thickness 1~5 nm); quantum dot precursors: cadmium chloride, thioacetamide (both analytical grade); template molecule: pyrene (purity ≥98%); photoactive functional monomer: m-aminophenol (analytical grade); crosslinking agent: N,N'-methylenebisacrylamide (analytical grade); initiator: azobisisobutyronitrile (analytical grade); solvent: methanol and acetonitrile mixture (volume ratio 1:1); eluent: methanol and acetic acid (volume ratio 9:1); electrolyte: 0.15 mol / L potassium chloride solution; pyrene standard (purity ≥99.5%); experimental water: ultrapure water; food samples: barbecued chicken wings, fried peanuts.

[0064] Instruments: Electrochemical workstation (CHI760E); ultrasonic cleaner; vacuum drying oven; muffle furnace; hydrothermal reactor; ultraviolet lamp (365nm); SEM; high performance liquid chromatograph (HPLC, Agilent 1260).

[0065] Fabrication of photoelectric substrate electrodes The gold electrode was polished to a mirror finish with 0.3 μm and 0.05 μm alumina powders, respectively, and then ultrasonically cleaned with acetone, ethanol, and ultrapure water for 15 min each. The cleaned gold electrode was then immersed in a 1 mol / L sulfuric acid solution and activated by cyclic voltammetry (-0.2~1.0 V, 50 mV / s) for 20 cycles. After rinsing with ultrapure water, the electrode was dried with nitrogen gas for later use.

[0066] Preparation of CdS quantum dot-black phosphorus composite photoelectric active material: 0.1 g of black phosphorus nanosheets were weighed and added to 100 mL of ultrapure water. The mixture was ultrasonically dispersed for 30 min to form a black phosphorus dispersion of 1 mg / mL. 0.05 mmol of cadmium chloride and 0.05 mmol of thioacetamide were weighed and added to the black phosphorus dispersion. The mixture was magnetically stirred for 20 min and the pH of the solution was adjusted to 9.0. The mixture was transferred to a hydrothermal reactor and reacted at 140 °C for 10 h. After the reaction, the mixture was cooled to room temperature, centrifuged at 8000 r / min for 15 min, and the precipitate was washed three times with ultrapure water and ethanol. The precipitate was then vacuum dried at 60 °C for 12 h to obtain the CdS quantum dot-black phosphorus composite photoelectric active material with a mass ratio of 1:4.

[0067] Weigh 30 mg of composite photoelectric active material, add 20 mL of ultrapure water, and ultrasonically disperse for 25 min to form a dispersion of 1.5 mg / mL. The dispersion is coated onto the surface of a gold electrode using a drop-coating method with a drop-coating amount of 5 μL / cm2. The electrode is dried at 100 °C for 2 h, calcined at 300 °C for 4 h, and cooled to obtain a CdS quantum dot-black phosphorus composite photoelectric substrate electrode.

[0068] Preparation of in situ molecularly imprinted membranes Weigh 0.04 mmol of pyrene template molecules and add them to a 50 mL beaker. Add 0.24 mmol of m-aminophenol functional monomer, 0.08 mmol of N,N'-methylenebisacrylamide crosslinking agent, and 0.004 g of azobisisobutyronitrile initiator. Add 15 mL of a mixture of methanol and acetonitrile and sonicate for 15 min to form a polymerization system.

[0069] The photoelectric substrate electrode was immersed in the polymerization system and argon gas was introduced for 45 min to remove oxygen; thermal polymerization was initiated at 65℃ for 5 h; after polymerization, the electrode was removed and washed in an eluent with a methanol to acetic acid volume ratio of 9:1 for 20 h, and the eluent was changed 4 times; after rinsing with ultrapure water, it was vacuum dried at 60℃ for 4 h to obtain the pyrene in-situ molecularly imprinted photoelectric electrode.

[0070] SEM characterization showed that the imprinted film on the gold electrode surface was uniformly covered with a thickness of about 80~120nm and was tightly bonded to the electrode; photoelectric performance tests showed that the electrode had strong light absorption in the range of 350~480nm and stable photoelectric response signal.

[0071] Trace detection of pyrene in food Food sample pretreatment: Weigh 5g of barbecued chicken wing sample, cut it into pieces, add 20mL of acetonitrile, extract by sonication for 40min, centrifuge at 5000r / min for 10min, and collect the supernatant; purify the supernatant by passing it through a neutral alumina solid-phase extraction column, elute with 10mL of acetonitrile, collect the eluent, filter it through a 0.22μm filter membrane to obtain the sample extract; process fried peanut sample in the same way.

[0072] A series of pyrene standard solutions were prepared, ranging from 1×10⁻¹² to 1×10⁻⁶ mol / L. Following the detection method described in Example 1, a constant bias voltage of 0.4V was applied, and the solution was excited by 365nm ultraviolet light (photoelectric power density 70mW / cm²). A standard curve was then plotted. The results showed that the pyrene concentration exhibited good linearity within the range of 1×10⁻¹² to 1×10⁻⁶ mol / L, with a regression equation of I (μA) = 2.41logC (mol / L) + 32.15, R² = 0.9985, and a detection limit of 2.8×10⁻¹³ mol / L.

[0073] The sample extract was injected into the detection system, and the detection was performed according to the above method. Simultaneously, HPLC was used for comparative verification. The results showed that the pyrene concentration in the barbecued chicken wing sample was 1.2 × 10⁻¹⁰ mol / L, while the HPLC result was 1.15 × 10⁻¹⁰ mol / L; the pyrene concentration in the fried peanut sample was 8.5 × 10⁻¹¹ mol / L, while the HPLC result was 8.2 × 10⁻¹¹ mol / L. There was no significant difference between the two methods (P > 0.05).

[0074] In the spiked recovery experiment, pyrene standards of low, medium and high concentrations were added to the sample extract. The recovery rates were between 91.8% and 103.2%, and the RSD was between 2.0% and 2.9%. This indicates that the method is suitable for trace detection of pyrene in food. The results are accurate and reliable, and the operation is simple and the detection is rapid. Compared with the HPLC method, it does not require complicated sample purification steps and the detection efficiency is significantly improved.

[0075] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for detecting trace amounts of polycyclic aromatic hydrocarbons using an in-situ molecularly imprinted photoelectrode, characterized in that, Includes the following steps: Step (1) Preparation of photoelectric substrate electrode: Select a conductive substrate, clean and activate it in sequence, coat the surface of the conductive substrate with the photoelectric active composite material dispersion, and obtain the photoelectric substrate electrode by drying and calcination; The photoelectric active composite material is a composite system of quantum dots and two-dimensional layered materials, wherein the quantum dots are selected from at least one of TiO2, CdS and ZnO, and the two-dimensional layered materials are selected from at least one of MoS2, WS2 and black phosphorus; Step (2) Preparation of in-situ molecularly imprinted film: Polycyclic aromatic hydrocarbon template molecules, photoactive functional monomers, crosslinking agents and initiators are dissolved in a solvent and ultrasonically dispersed to form a uniform polymerization system; the photoelectric substrate electrode prepared in step (1) is immersed in the polymerization system, and in-situ polymerization reaction is carried out under the protection of inert gas by photoinitiation or thermal initiation. After the reaction is completed, the template molecules are removed by elution to obtain the in-situ molecularly imprinted photoelectric electrode; Step (3) Trace detection of polycyclic aromatic hydrocarbons: The in-situ molecularly imprinted photoelectrode is used as the working electrode, the saturated calomel electrode is used as the reference electrode, and the platinum wire is used as the counter electrode to form a three-electrode system; the three-electrode system is immersed in the sample solution containing the polycyclic aromatic hydrocarbons to be tested, electrolyte is added to adjust the conductivity of the solution, a constant bias voltage of 0.2~0.8V is applied, and visible light or ultraviolet light with a wavelength of 300~500nm is used for continuous excitation. The photoelectric response current signal is collected by an electrochemical workstation, and the trace quantitative detection of polycyclic aromatic hydrocarbons is realized according to the linear relationship between the signal intensity and the concentration of polycyclic aromatic hydrocarbons.

2. The method for detecting trace amounts of polycyclic aromatic hydrocarbons using an in-situ molecularly imprinted photoelectrode according to claim 1, characterized in that: The conductive substrate mentioned in step (1) is ITO conductive glass, fluorine-doped tin oxide conductive glass or gold electrode. The cleaning process includes ultrasonic cleaning with acetone, ethanol and deionized water for 15 to 30 minutes in sequence. The activation process is cyclic voltammetric activation in 0.5 to 1 mol / L sulfuric acid solution.

3. The method for detecting trace amounts of polycyclic aromatic hydrocarbons using an in-situ molecularly imprinted photoelectrode according to claim 1, characterized in that: The preparation method of the photoelectric active composite material in step (1) is as follows: the two-dimensional layered material is dispersed in deionized water, a quantum dot precursor is added, and a hydrothermal reaction is carried out at 120~180℃ for 6~12h. After cooling, the material is separated by centrifugation, washed, and dried. The mass ratio of quantum dots to two-dimensional layered materials is 1:2 to 1:

5.

4. The method for detecting trace amounts of polycyclic aromatic hydrocarbons using an in-situ molecularly imprinted photoelectrode according to claim 1, characterized in that: The polycyclic aromatic hydrocarbon template molecule mentioned in step (2) is selected from one or more of benzo[a]pyrene, fluoranthene, pyrene, and benzo[b]fluoranthene, and the molar ratio of the template molecule to the photoelectroactive functional monomer is 1:4 to 1:

8.

5. The method for detecting trace amounts of polycyclic aromatic hydrocarbons using an in-situ molecularly imprinted photoelectrode according to claim 1, characterized in that: The photoactive functional monomers mentioned in step (2) are o-phenylenediamine, m-aminophenol or p-aminobenzoic acid, the crosslinking agent is ethylene glycol dimethacrylate or N,N'-methylenebisacrylamide, and the initiator is azobisisobutyronitrile or 2-hydroxy-2-methyl-1-phenyl-1-propanone.

6. The method for detecting trace amounts of polycyclic aromatic hydrocarbons using an in-situ molecularly imprinted photoelectrode according to claim 1, characterized in that: In step (2), the in-situ polymerization reaction conditions are as follows: for photoinitiation, irradiation with 254~365nm ultraviolet light is used for 2~4h; for thermal initiation, the reaction is carried out at 60~80℃ for 4~6h; for elution, a mixed solution of methanol and acetic acid is used as the eluent with a volume ratio of 9:1~8:2 and an elution time of 12~24h.

7. The method for detecting trace amounts of polycyclic aromatic hydrocarbons using an in-situ molecularly imprinted photoelectrode according to claim 1, characterized in that: The electrolyte mentioned in step (3) is a 0.05~0.2mol / L phosphate buffer solution or potassium chloride solution, and the pH value of the solution is adjusted to 6.0~8.

0.

8. The method for detecting trace amounts of polycyclic aromatic hydrocarbons using an in-situ molecularly imprinted photoelectrode according to claim 1, characterized in that: In step (3), the light power density of photoexcitation is 50~100mW / cm2, the signal acquisition time is 10~30s, and the detection linear range is 10-12~10-6mol / L.

9. The method for detecting trace amounts of polycyclic aromatic hydrocarbons using an in-situ molecularly imprinted photoelectrode according to claim 1, characterized in that: The sample solution is an environmental water sample, soil extract, or food extract. The sample solution is directly used for detection after being filtered through a 0.22μm filter membrane, without the need for additional concentration treatment.

10. The method for detecting trace amounts of polycyclic aromatic hydrocarbons using an in-situ molecularly imprinted photoelectrode according to claim 4, characterized in that: When there are multiple template molecules, the molar ratio of the multiple template molecules is 1:1 to 1:3, and the corresponding detection method can simultaneously realize the quantitative analysis of multiple polycyclic aromatic hydrocarbons.

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