A core-shell composite material, electrochemical sensor, and preparation method and application thereof

Abstract

The application discloses a kind of core-shell composite materials, electrochemical sensor and its preparation method and application, the core-shell composite materials include inner core and the shell layer of the inner core is wrapped, the inner core is metal organic framework PCN-222;The preparation method of the core-shell composite material includes: metal organic framework PCN-222 is dispersed in first solvent, and dispersion liquid A is obtained;Functional monomer, template molecule, crosslinking agent and initiator are added to dispersion liquid A, and polymerization reaction is carried out, and reaction product is obtained;Template molecule of the reaction product is removed using second solvent, and the core-shell composite material is obtained.The electrochemical sensor includes working electrode, and the surface of the working electrode is attached with the core-shell composite material, it has excellent conductivity and specific recognition site, and is applied to detect 4-nonyl phenol in environment, and shows high sensitivity and selectivity.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical sensors, and in particular to a core-shell composite material, an electrochemical sensor, and a preparation method and application thereof. Background Art

[0002] 4-Nonylphenol is an endocrine disruptor (EDC) with a structure similar to estrogen and estrogenic effects, affecting the endocrine system in both wildlife and humans. 4-Nonylphenol in the environment primarily originates from intermediates in the production of polymer surfactants.

[0003] Currently, there are multiple methods for detecting 4-nonylphenol, including liquid chromatography-mass spectrometry, gas chromatography-mass spectrometry, fluorescence, and electrochemical methods. Electrochemical methods offer advantages due to their ease of miniaturization, inherent high selectivity, simplicity, and low cost. Molecularly imprinted polymers (MIPs) are widely used in the construction of electrochemical sensors due to their specific recognition and enrichment capabilities. However, existing electrochemical sensors suffer from poor electrocatalytic performance and low detection sensitivity, limiting their application in diverse environmental samples. Summary of the Invention

[0004] The present invention aims to provide a core-shell composite material with high sensitivity and selectivity to solve the problem that the existing electrochemical sensor has poor detection effect on 4-nonylphenol.

[0005] A core-shell composite material comprising a core and a shell layer surrounding the core, wherein the core is a metal organic framework PCN-222;

[0006] The preparation method of the core-shell composite material comprises:

[0007] Dispersing the metal organic framework PCN-222 in a first solvent to obtain a dispersion A;

[0008] Adding functional monomers, template molecules, crosslinking agents and initiators to dispersion A to carry out polymerization reaction to obtain a reaction product;

[0009] The template molecules in the reaction product are eluted with a second solvent to obtain the core-shell composite material.

[0010] In the core-shell composite, the metal-organic framework PCN-222, which has unique molecular structural units and square-planar coordination sites in the porphyrin unit, is a porous metal framework material with good electrical conductivity and a large specific surface area, which can improve the electrochemical performance of the core-shell material. The microporous shell structure can provide specific sites for the molecules to be detected. By combining the high conductivity of the metal-organic framework PCN-222 with the high selectivity of the shell, the core-shell composite material of the present invention has the potential to be used as a surface molecularly imprinted polymer material.

[0011] The metal-organic framework PCN-222 is typically a rod-shaped structure having a length and a diameter. Optionally, the diameter of the metal-organic framework PCN-222 is 0.7-1.0 μm, preferably 0.8-0.9 μm. For example, the metal-organic framework PCN-222 is purchased from Shanghai Chemsoon Company and is obtained by reacting ZrCl4 and tetrakis(4-carboxyphenyl)porphyrin (TCPP).

[0012] Optionally, the shell layer has a thickness of 0.1-0.3 μm, preferably about 0.2 μm.

[0013] Optionally, the specific surface area of ​​the core-shell composite material is 123-126m 2 / g, pore volume of 0.080-0.090m 3 / g.

[0014] Preferably, the specific surface area of ​​the core-shell composite material is 124.56 m 2 / g, pore volume 0.085m 3 / g.

[0015] Optionally, the preparation method further comprises:

[0016] Before the polymerization reaction, the reaction system is deoxygenated to reduce the occurrence of side reactions.

[0017] Optionally, the deoxygenation method is: introducing nitrogen into the reaction system.

[0018] Alternatively, using 4-nonylphenol as the template molecule, the functional monomer is 1-allyl-3-ethylimidazolium bromide ([AEIm]Br), the crosslinker is poly(1,4-butanediyl-3,3-bis-1-vinylimidazolium dibromide) ([V2C4(mim)2]Br2), and the initiator is azobisisobutyronitrile (AIBN). The core-shell composite prepared by this method is a composite of a metal-organic framework PCN-222 and a molecularly imprinted polyionic liquid (MIPIL), hereinafter collectively referred to as PCN-222@MIPIL.

[0019] Optionally, the polymerization reaction conditions are: reaction at 60° C. for 24 hours.

[0020] Optionally, the first solvent is a mixture of methanol and toluene (volume ratio 1:1).

[0021] Optionally, the second solvent is methanol.

[0022] Optionally, the mass ratio of the core, template molecule, functional monomer and cross-linking agent is 1:3:12:60.

[0023] Optionally, the molar ratio of the initiator to the functional monomer is 1:1.3.

[0024] The present invention also provides an electrochemical sensor, comprising a working electrode, the surface of which is adhered to the core-shell composite material.

[0025] Optionally, the working electrode is a glassy carbon electrode (GCE), and the resulting electrochemical sensor is called a PCN-222@MIPIL / GCE sensor.

[0026] Optionally, the core-shell composite material is attached to the surface of the working electrode in the form of a film.

[0027] The present invention also provides a method for preparing the electrochemical sensor, comprising:

[0028] Dispersing the core-shell composite material in a polyethyleneimine aqueous solution (PEI aqueous solution) to obtain a dispersion A;

[0029] Applying the dispersion A dropwise to the surface of the working electrode;

[0030] After drying, the electrochemical sensor is obtained.

[0031] Optionally, the molecular weight of the polyethyleneimine is 70,000, and the mass concentration of the polyethyleneimine is 0.5%.

[0032] Optionally, the concentration of the core-shell composite material in the dispersion A is 3-8 mg / mL, preferably 5 mg / mL.

[0033] Optionally, the drop-coating amount of the dispersion A is 3-7 μL, preferably 5 μL. Optionally, the surface of the working electrode is pre-polished.

[0034] Optionally, the drying method is natural drying at room temperature.

[0035] The present invention also provides the use of the aforementioned electrochemical sensor for detecting 4-nonylphenol. The core-shell composite material used in the electrochemical sensor uses 4-nonylphenol as a template molecule, resulting in a highly selective shell that effectively avoids interference from 4-nonylphenol analogs, including catechol, hydroquinone, 2-nonylphenol, 2-nitrophenol, benzidine, and hydrogenated bisphenol A. The electrochemical sensor can be used to detect the 4-nonylphenol content in lakes, rivers, soil, seafood, and toiletries.

[0036] The present invention also provides a method for detecting 4-nonylphenol, which uses the electrochemical sensor to detect 4-nonylphenol in a sample, and specifically comprises the following steps:

[0037] Immerse the working electrode in the sample for incubation;

[0038] After incubation, pulse voltammetry was used for measurement.

[0039] Optionally, the sample is a standard solution of 4-nonylphenol or an environmental sample.

[0040] Optionally, the pH of the sample is 6.0-8.0.

[0041] Optionally, the working electrode is incubated in the sample while stirring, and after incubation for 6 to 8 minutes, measurement is performed using pulse voltammetry.

[0042] Alternatively, the linear range for 4-nonylphenol is 1 × 10 -4 The detection limit (LOD) was 0.03 nM (S / N=3) at 10 μM.

[0043] Compared with the prior art, the present invention has the following technical effects:

[0044] The core-shell composite material provided by the present invention has good electrical conductivity and selectivity, and is an ideal choice as a surface molecularly imprinted polymer material. Its application in the preparation of electrochemical sensors helps to improve their electrochemical performance;

[0045] The electrochemical sensor of the present invention has excellent sensitivity and selectivity to 4-nonylphenol, has wide practical applicability, and can be reliably used to analyze 4-nonylphenol in actual samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The figure shows the preparation of the electrochemical sensor and its detection process for 4-nonylphenol;

[0047] Figure 2A Infrared spectra of PCN-222, [V2C4(mim)2]Br2 and PCN-222@MIPIL, where a: PCN-222, b: [V2C4(mim)2]Br2, c: PCN-222@MIPIL.

[0048] Figure 2B X-ray photoelectron spectra of PCN-222 and PCN-222@MIPIL, where a: PCN-222, b: PCN-222@MIPIL;

[0049] Figure 3A is the nitrogen adsorption isotherm of PCN-222;

[0050] Figure 3B is the nitrogen adsorption isotherm of PCN-222@MIPIL;

[0051] Figure 3CThe pore size distribution diagrams of PCN-222 and PCN-222@MIPIL, where a: PCN-222; b: PCN-222@MIPIL;

[0052] Figure 3D Thermogravimetric curves of PCN-222 and PCN-222@MIPIL; a: PCN-222, b: PCN-222@MIPIL;

[0053] Figure 4A is a scanning electron microscope image of PCN-222;

[0054] Figure 4B This is a transmission electron microscope image of PCN-222;

[0055] Figure 4C This is the scanning electron microscopy image of PCN-222@MIPIL;

[0056] Figure 4D Transmission electron microscopy image of PCN-222@MIPIL;

[0057] Figure 5 Energy spectra of PCN-222 and PCN-222@MIPIL, where a: PCN-222@MIPIL, b: PCN-222;

[0058] Figure 6 EDS-Mapping diagram of PCN-222@MIPIL, where A: HAADF diagram of PCN-222@MIPIL; BF: mapping diagram of various elements in PCN-222@MIPIL;

[0059] Figure 7 The figure shows the effect of PCN-222@MIPIL dosage on the current response, where the concentration of 4-nonylphenol is 5.0 μM;

[0060] Figure 8 The graph shows the effect of pH value on the current response, where the concentration of 4-nonylphenol is 5.0 μM;

[0061] Figure 9 The figure shows the effect of incubation time on current response, where the concentration of 4-nonylphenol is 5.0 μM;

[0062] Figure 10A The differential pulse voltammetry curves of the PCN-222@MIPIL sensor for various 4-nonylphenol concentrations (0, 0.0001, 0.001, 0.01, 0.05, 0.1, 0.5, 1.0, 3.0, 5.0, 7.0, 10.0 μM) (corresponding to the al curves in the figure, respectively);

[0063] Figure 10B Current response diagram of PCN-222@MIPIL sensor to 5.0 μM 4-nonylphenol and analogs;

[0064] Figure 11A Differential pulse voltammetry curves of various sensors after incubation in 4-nonylphenol (5.0 μM) solution, where a: PCN-222@MIPIL / GCE, b: PCN-222@NIPIL / GCE, c: PCN-222 / GCE, d: MIPIL / GCE;

[0065] Figure 11B Current response diagrams of various sensors after incubation in 4-nonylphenol (5.0 μM) solution, where a: PCN-222@MIPIL / GCE, b: PCN-222@NIPIL / GCE, c: PCN-222 / GCE, d: MIPIL / GCE;

[0066] Figure 12A The differential pulse voltammetry curves of the PCN-222@MIPIL sensor for various 4-nonylphenol concentrations (0, 0.0001, 0.001, 0.01, 0.05, 0.1, 0.5, 1.0, 3.0, 5.0, 7.0, 10.0 μM) (corresponding to the al curves in the figure)

[0067] Figure 12B Standard curves of PCN-222@MIPIL (a), ZIF-8@MIPIL (b), MIPIL (c) and PCN-222 (d) sensors for the detection of 4-nonylphenol. DETAILED DESCRIPTION

[0068] The technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0069] Example 1

[0070] See also Figure 1 , the preparation method of PCN-222@MIPIL is as follows:

[0071] (1) 80 mg of PCN-222 was dispersed in 30 mL of a methanol-toluene mixture (1:1 volume ratio) in a flask;

[0072] (2) adding 0.4 mmol [AEIm]Br 1-allyl-3-ethylimidazolium bromide and 0.1 mmol 4-nonylphenol under continuous stirring, and then adding 50 mg AIBN (azobisisobutyronitrile) and 2.0 mmol [V2C4(mim)2]Br2 poly (1,4-butanediyl-3,3-bis-1-vinylimidazolium dibromide) to obtain a reaction system;

[0073] (3) After deoxygenating the reaction system with nitrogen for 30 minutes, the polymerization reaction was carried out at 60°C for 24 hours;

[0074] (4) The 4-nonylphenol template molecule in PCN-222@MIPIL was removed by methanol to obtain PCN-222@MIPIL.

[0075] The successful preparation of PCN-222@MIPIL was verified by infrared spectrometry. Figure 2A , a, b, c represent the infrared spectra of PCN-222, [V2C4(mim)2]Br2 and PCN-222@MIPIL, respectively. PCN-222 is at 1603 cm -1 、1545cm -1 and 1408cm -1 The main absorption band at 1550 cm-1 can be attributed to the stretching vibration of the benzene ring. The C=N, C=C and CN vibrations of the imidazolium cation in [V2C4(mim)2]Br2 correspond to the bands at 1550 cm-1. -1 、1456cm -1 and 1185cm -1 The absorption peaks of PCN-222 have corresponding peaks in the spectrum of PCN-222@MIPIL. -1 The absorption peak of PCN-222@MIPIL at 1564 cm -1 and 1179cm -1 The peak at coincides with the infrared peak of [V2C4(mim)2]Br2, verifying the successful preparation of PCN-222@MIPIL.

[0076] The chemical elements of the core-shell composites were determined by X-ray photoelectron spectroscopy ( Figure 2B Both PCN-222 and PCN-222@MIPIL exhibit peaks of C1s, O1s, N1s, and Zr3d. PCN-222@MIPIL exhibits an additional Br 3d signal compared to PCN-222, indicating that MIPIL is successfully complexed with PCN-222.

[0077] Figure 3A and Figure 3B The N2 adsorption-desorption isotherms of PCN-222 and PCN-222@MIPIL are shown in Figure 2. The BET specific surface areas of PCN-222 and PCN-222@MIPIL are 1448.65 and 124.56 m 2 / g. The average pore volumes of PCN-222 and PCN-222@MIPIL are 1.33 and 0.085 m 3 / g.

[0078] Determination of pore size distribution curve ( Figure 3C ) showed that the average pore sizes of PCN-222(H) were 1.2 nm and 3.3 nm, while those of PCN-222@MIPIL were 1.1 nm and 2.7 nm. These results indicate that the specific surface area and pore volume of PCN-222@MIPIL are lower than those of PCN-222. The lower specific surface area, pore volume, and average pore width of PCN-222@MIPIL can be attributed to the presence of MIPIL on the surface of PCN-222.

[0079] Thermogravimetric spectra showed obvious differences in weight loss characteristics, with PCN-222 losing 45% of its total weight ( Figure 3D ) while PCN-222@MIPIL lost 90%. The huge weight loss percentage of PCN-222@MIPIL can be attributed to the thermal instability of MIPIL, indicating the successful synthesis of PCN-222@MIPIL.

[0080] In addition, the morphological characteristics of the synthesized PCN-222@MIPIL were studied using transmission electron microscopy and scanning electron microscopy. PCN-222 was rod-shaped with a size of 0.7 to 1.0 μm ( Figure 4A 、 Figure 4B The diameter of the MIPIL complex increased to 0.9 to 1.2 μm, and a shell was coated on the surface of PCN-222, indicating the successful formation of the PCN-222@MIPIL core-shell structure ( Figure 4C The core-shell structure of PCN-222@MIPIL was further confirmed by TEM ( Figure 4D ).

[0081] The energy spectrum of PCN-222 shows peaks of C, O, N, and Zr elements, while the energy spectrum of PCN-222@MIPIL shows an additional peak of Br element ( Figure 5 ), proving the formation of PCN-222@MIPIL composite material. EDS-Mapping diagram ( Figure 6 ) It can be seen that Zr, C, N, O and Br are evenly distributed throughout the structure. In addition, the diameter of the Br element ( Figure 6 C) is significantly greater than Zr( Figure 6 B), demonstrating the successful formation of MIPIL on the Zr-based MOF surface.

[0082] Example 2

[0083] See also Figure 1The preparation method of PCN-222@MIPIL / GCE sensor is as follows:

[0084] 5 mg of PCN-222@MIPIL was dispersed in a PEI aqueous solution (1 mL, 0.5 wt%). Subsequently, the PCN-222@MIPIL (or PCN-222@NIPIL, PCN-222, MIPIL) solution prepared in Example 1 was dropped onto a polished glassy carbon (GCE) electrode and dried at ambient temperature to obtain a PCN-222@MIPIL / GCE sensor.

[0085] The PCN-222@MIPIL with different volumes (3, 4, 5, 6, and 7 μL) was coated on the glassy carbon electrode and their activity in [Fe(CN)6] 3– / 4– The cyclic voltammetry curves ( Figure 7 ), 5 μL volume of PCN-222@MIPIL showed the most sensitive current response, therefore, 5 μL was selected as the optimal dosage of PCN-222@MIPIL.

[0086] Example 3

[0087] The effect of the test solution pH was studied by recording the electrochemical response under different pH conditions. The electrochemical response increased when the pH value ranged from 6.0 to 8.0. As the pH value increased to 10.0, the response decreased ( Figure 8 ). Therefore, pH 8.0 was selected as the optimal pH for the experiment.

[0088] Example 4

[0089] The adsorption time of PCN-222@MIPIL / GCE sensor in 4-nonylphenol solution was studied. Figure 9 ), the electrochemical response reached a plateau at 6 minutes, and the adsorption of 4-nonylphenol by PCN-222@MIPIL / GCE reached its maximum adsorption capacity at 6 minutes. Therefore, the 6-minute incubation time is the optimal time for adsorption.

[0090] Example 5

[0091] The selectivity of PCN-222@MIPIL / GCE sensor was investigated. The current response of 4-nonylphenol (4-NP) was higher than that of its analogs ( Figure 10A In addition, from the current ratio (I 4-壬基酚 / I analog ) to evaluate the selectivity. The I of catechol (CL), hydroquinone (HQ), o-aminophenol (2-AP), 2-nitrophenol (2-NP), benzidine (DAB) and hydrogenated bisphenol A (HBPA) were observed on the PCN-222@MIPIL sensor. 4-壬基酚 / I类似物 In addition, no interference was observed when 4-nonylphenol was detected using 5 times of catechol, hydroquinone and 10 times of 2-nitrophenol, 2-nonylphenol, benzidine and hydrogenated bisphenol analogs ( Figure 10B The PCN-222@MIPIL sensor exhibits excellent selectivity for 4-nonylphenol due to the specific recognition site.

[0092] Comparative Example 1

[0093] PCN-222@NIPIL (5 mg) was dispersed in a 1 ml 0.5 wt% aqueous PEI solution. Subsequently, 5 μL of the prepared PCN-222@NIPIL solution was dripped onto the polished GCE. The PCN-222@NIPIL-modified GCE (sensor) was dried at ambient temperature to obtain a PCN-222@NIPIL / GCE sensor.

[0094] Comparative Example 2

[0095] PCN-222 (5 mg) was dispersed in a PEI aqueous solution (1 ml, 0.5 wt%). Subsequently, 5 μL of the PCN-222 solution prepared above was dropped onto the polished GCE. The PCN-222-modified GCE (sensor) was dried at ambient temperature to obtain a PCN-222 / GCE sensor.

[0096] Comparative Example 3

[0097] MIPIL (5 mg) was dispersed in PEI aqueous solution (1 ml, 0.5 wt%). Subsequently, 5 μL of the MIPIL solution prepared above was dropped onto the polished GCE. The MIPIL-modified GCE (sensor) was dried at ambient temperature to obtain a MIPIL / GCE sensor.

[0098] Comparative Example 4

[0099] g-C3N4 a The preparation method of / CuO / GCE refers to the following literature:

[0100] J.Zou, WMDeng, JZJiang, Arramel,

[0101] Comparative Example 5

[0102] Au-NP / β-CD b / sol-gel / GNP c / GCE preparation method refers to the following literature:

[0103] DDSu,YYZhang,ZJWang,QJWan,NJYang,Decoration of graphenenano platelets with gold nanoparticles for voltammetry of 4-nonylphenol,Carbon,117(2017)313-321.

[0104] Comparative Example 6

[0105] PPy d / TiO2 MIP / Nafion / GCE preparation method refers to the following literature:

[0106] MZYu,LNWu,JNMiao,W.Wei,ARLiu,SQLiu,Titanium dioxide andpolypyrrole molecularly imprinted polymer nanocomposites basedelectrochemical sensor for highly selective detection of p-nonylphenol,Anal.Chim.Acta,1080(2019)84-94.

[0107] Comparative Example 7

[0108] The preparation method of MIL-101(Cr) / rGO / GCE refers to the following literature:

[0109] YYZhang,P.Yan,QJWan,NJYang,Integration of chromiumterephthalate metal-organic frameworks with reduced graphene oxide forvoltammetry of4-nonylphenol,Carbon,134(2018)540-547.

[0110] Comparative Example 8

[0111] nanopyramid BDD e The preparation method refers to the following literature:

[0112] XXYuan, N.Gao,

[0113] Comparative Example 9

[0114] The preparation method of MWCNT-MIP / GCE is referred to the following literature:

[0115] B.Liu,JLYan,M.Wang,XYWu,Electrochemical sensor based on molecularly imprinted polymer for determination of nonylphenol,Int.J.Electrochem.Sci.,(2018)11953-11960.

[0116] Comparative Example 10

[0117] SH-β-CD-GR f / Au preparation methods refer to the following literature:

[0118] F.Xue, ZYGao,

[0119] Test example

[0120] (1) Electrochemical performance

[0121] The differential pulse voltammetry current responses of MIPIL / GCE sensor, PCN-222 / GCE sensor, PCN-222@NIPIL / GCE sensor, and PCN-222@MIPIL / GCE sensor in the presence of 5.0 μM 4-nonylphenol were measured. Figure 11A ), PCN-222@MIPIL sensor showed the highest current response to 4-nonylphenol. The oxidation current response of PCN-222@MIPIL sensor was 2.54, 2.14 and 4.24 times that of PCN-222@NIPIL, PCN-222 and MIPIL sensors, respectively ( Figure 11B The results showed that the PCN-222@MIPIL sensor outperformed other sensors. The excellent conductivity and specific recognition sites of PCN-222@MIPIL significantly contributed to its advantages.

[0122] (2) Linear relationship and detection limit of 4-nonylphenol

[0123] The linear relationship of PCN-222@MIPIL / GCE sensor prepared in Example to 4-nonylphenol was tested respectively, and the results are shown in Figure 12. PCN-222@MIPIL / GCE sensor was tested at 1×10 -4 There is a good linear correlation between the concentration of 4-nonylphenol and the concentration of 4-nonylphenol in the range of 10 μM to 10 μM. Figure 12A The detection limit (LOD) of the PCN-222@MIPIL / GCE sensor for 4-nonylphenol was 0.03 nM (S / N=3).

[0124] The present invention also studies the linear relationship of ZIF-8@MIPIL / GCE sensor, PCN-222 / GCE sensor and MIPIL / GCE sensor to 4-nonylphenol in Comparative Examples 1 to 3 ( Figure 12B ). When the concentration of 4-nonylphenol is 2.0×10 –3MIPIL / GCE sensor showed a linear relationship up to 10 μΜ. Meanwhile, the DPV response of PCN-222 / GCE sensor was linear in the range of 5.0 x 10 –3 ZIF-8@MIPIL / GCE sensor showed a good linear relationship up to 10 μΜ. In addition, PCN-222 / GCE sensor showed a linear relationship up to 5.0 x 10 –3 MIPIL / GCE, PCN-222 / GCE and ZIF-8@MIPIL sensors for 4-nonylphenol were 0.92, 1.5 and 0.36 nM (S / N = 3), respectively. K1, K2, K3 and K4 represent the linear slopes of PCN-222@MIPIL / GCE, MIPIL / GCE, ZIF-8@MIPIL / GCE and PCN-222 / GCE sensors, respectively (K1= 0.0468, K2= 0.0153, K3= 0.0217 and K4= 0.0283). The ratio of K1 and K2, K3 or K4 can be used to evaluate different MIP sensors. K1 / K2, K1 / K3 and K1 / K4 were 3.06, 2.16 and 1.65, respectively, indicating that the current response and sensitivity of PCN-222@MIPIL / GCE sensor were higher than those of other sensors. Figure 12B

[0125] The highest sensitivity of PCN-222@MIPIL / GCE sensor was attributed to the surface MIP composite material with core-shell structure and the excellent conductivity of PCN-222. PCN-222@MIPIL with large specific surface area and fast template molecule recognition enhanced the DPV response and the sensitivity of PCN-222@MIPIL / GCE sensor for 4-nonylphenol. The comparison of PCN-222@MIPIL / GCE sensor with other electrochemical methods for 4-nonylphenol analysis was shown in Table 1. The LOD of PCN-222@MIPIL / GCE sensor was the lowest. The excellent performance of PCN-222@MIPIL / GCE sensor could be attributed to the high conductivity, large specific surface area of PCN-222 support material and the shell of surface MIPIL. Therefore, it could be concluded that PCN-222@MIPIL / GCE sensor was effective for 4-nonylphenol detection.

[0126] Table 1 Comparison of detection methods

[0127]

[0128]

[0129] a Carbon nitride, b β-cyclodextrin, c Graphene nanosheet, d ​polypyrrole, e Boron-doped diamond, f-thiol-β-cyclodextrin-graphene

[0130] (3) Actual sample measurement

[0131] To investigate the practical applicability of the PCN-222@MIPIL sensor, it was used to detect 4-nonylphenol in real samples, including lake water, soil, facial cleanser, and shrimp samples (Table 2). Soil samples were obtained from Jiaxing University, and lake water samples were obtained from Nanhu Lake. The soil samples were dried and ground. 1.0 g of the sample was then ultrasonically extracted with 10 mL of methanol for 30 minutes. The supernatant was evaporated to dryness under a stream of nitrogen, and 10 mL of phosphate buffer (pH 8.0) was added. The lake water sample was filtered through a 0.45 μm filter to remove particulate matter, and the filtrate was collected for analysis. Shrimp samples obtained from a local market were homogenized in a meat grinder. 1.0 g of shrimp was ultrasonically extracted in a test tube containing 10 mL of methanol for 30 minutes and centrifuged. The supernatant was then evaporated to dryness under a stream of nitrogen, and 10 mL of phosphate buffer (pH 8.0) was added. This solution was collected for analysis. Facial cleanser samples were also obtained from a local supermarket and pretreated using the same method as the shrimp samples.

[0132] Because 4-nonylphenol could not be detected in these samples, a 4-nonylphenol standard solution was added to them to explore the accuracy of the proposed method. The results are shown in Table 2. The recoveries of 4-nonylphenol in real samples using the PCN-222@MIPIL / GCE sensor ranged from 96.4% to 104.0%, with an RSD of less than 4.6%. This demonstrates that the PCN-222@MIPIL / GCE sensor of the present invention can be reliably applied to analyze real samples.

[0133] Table 2 Determination of 4-nonylphenol in actual samples using PCN-222@MIPIL / GCE sensor

[0134]

[0135]

[0136] The above description of the embodiments is intended to facilitate understanding and application of the present invention by those skilled in the art. Those skilled in the art may also make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and modifications and variations of the present invention should also fall within the scope of protection of the claims of the present invention.

Claims

1. A core-shell composite material, characterized in that It includes a core and a shell layer wrapping the core, wherein the core is a metal organic framework PCN-222; The preparation method of the core-shell composite material comprises: Dispersing the metal organic framework PCN-222 in a first solvent to obtain a dispersion A; Adding functional monomers, template molecules, crosslinking agents and initiators to dispersion A to carry out polymerization reaction to obtain a reaction product; eluting the template molecules in the reaction product with a second solvent to obtain the core-shell composite material; The template molecule is 4-nonylphenol, the functional monomer is 1-allyl-3-ethylimidazolium bromide, the crosslinker is poly(1,4-butanediyl-3,3-bis-1-vinylimidazole dibromide), and the initiator is azobisisobutyronitrile; The specific surface area of ​​the core-shell composite material is 123-126m 2 / g, pore volume of 0.080-0.090m 3 / g; The diameter of the metal organic framework PCN-222 is 0.7-1.0 μm, and the thickness of the shell is 0.1-0.3 μm; The mass ratio of the core, template molecule, functional monomer and cross-linking agent is 1:3:12:60; The molar ratio of the initiator to the functional monomer is 1:1.

3.

2. An electrochemical sensor, characterized in that It comprises a working electrode, the surface of which is adhered with the core-shell composite material according to claim 1.

3. The electrochemical sensor according to claim 2, characterized in that The core-shell composite material is attached to the surface of the working electrode in the form of a film.

4. The method for preparing an electrochemical sensor according to claim 2, wherein: include: Dispersing the core-shell composite material in a polyethyleneimine aqueous solution to obtain a dispersion A; Applying the dispersion A dropwise to the surface of the working electrode; After drying, the electrochemical sensor is obtained.

5. The method for preparing an electrochemical sensor according to claim 4, wherein: The concentration of the core-shell composite material in the dispersion A is 3-8 mg / mL; The drop coating amount of the dispersion A is 3-7 μL.

6. Use of the electrochemical sensor according to claim 2 in detecting 4-nonylphenol.

7. A method for detecting 4-nonylphenol, characterized in that: Detecting 4-nonylphenol in a sample using the electrochemical sensor according to claim 2 comprises the following steps: Immerse the working electrode in the sample for incubation; After incubation, pulse voltammetry was used for measurement.

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