A molecular imprinting electrochemiluminescence sensor, a preparation method thereof and application of the sensor in selective detection of trilobatin

Abstract

The application belongs to the technical field of electrochemical analysis and detection, and discloses a molecular imprinting electrochemiluminescence sensor, a preparation method thereof and application of the sensor in selective detection of trilobatin. The operation comprises the following steps: (1) a prepared g-C3N4@NiMOF composite material is modified on the surface of a glassy carbon electrode; (2) the g-C3N4@NiMOF / GCE is placed in a phosphate buffer solution containing o-phenylenediamine and TRI, and o-PD and TRI are electropolymerized on the electrode surface through cyclic voltammetry in a three-electrode system to obtain MIP-p(o-PD)-TRI / g-C3N4@NiMOF / GCE; and (3) TRI in the polymerization film is eluted to form a specific imprinting cavity, and a MIP-p(o-PD) / g-C3N4@NiMOF / GCE sensor is obtained. The molecular imprinting electrochemiluminescence sensor has the advantages of simple operation, fast analysis speed, good selectivity and high sensitivity in the detection of TRI.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical analysis and detection, and particularly relates to a method for sensitive and selective detection of TRI by using a molecular imprinting electrochemiluminescence sensor. In particular, the g-C3N4@NiMOF prepared by a hydrothermal method is drop-coated on the surface of a glassy carbon electrode, a functional monomer o-PD is electropolymerized with a template molecule TRI on the surface of the modified electrode by a cyclic voltammetry method, and the template molecule TRI in the polymerized film is eluted by further immersion in KOH, so that the MIP-p(o-PD) / g-C3N4@NiMOF / GCE is used as a sensing element to construct a molecular imprinting electrochemiluminescence sensor for quantitative detection of TRI. BACKGROUND

[0002] Trilobatin (TRI) is a natural dihydrochalcone sweetener with a sweetness of more than 300 times that of sucrose, and is an emerging food additive internationally. TRI can be extracted from the leaves of Lithocarpus polystachyus Rehder. Studies have shown that TRI has pharmacological effects such as anti-diabetes, anti-inflammation, and nerve protection, and has a broad application prospect in the field of drug development. Traditional methods for detecting TRI include high performance liquid chromatography (HPLC), ultraviolet-visible spectroscopy (UV), nuclear magnetic resonance spectroscopy (NMR), and high performance liquid chromatography-mass spectrometry (HPLC-MS). However, these methods require large and expensive instruments, are complicated to operate, and take a long time to detect. Therefore, it is of practical application value to establish a simple, rapid, sensitive, and specific method for detecting TRI.

[0003] Electrochemiluminescence (ECL) is a modern analysis technology combining electrochemistry and chemiluminescence, and has high sensitivity of luminescence analysis and controllability of electrochemistry. Due to its high sensitivity, fast response, low cost, simple operation, and low background signal, ECL is widely used in the field of analysis and detection. Graphitic carbon nitride (g-C3N4) is a polymer semiconductor material with high quantum yield and non-toxicity, and has excellent ECL performance in the presence of a co-reactant. However, due to the excessive injection of high-energy electrons into the conduction band and the formation of a poor conductive layer by reduction reaction, the ECL stability of g-C3N4 is poor.

[0004] Metal-organic frameworks (MOFs) are porous materials with metal ions as central nodes and organic molecules as bridging ligands, and have great application prospects in the field of electrochemical analysis and detection. The published Chinese patent CN201710791390.2 uses g-C3N4 and cobalt-based metal-organic frameworks to synthesize g-C3N4@MOF nanocrystals for detecting chiral drugs. However, the preparation method of g-C3N4@MOF nanocrystals is relatively complicated and time-consuming, and g-C3N4@MOF nanocrystals with small particle size are easy to fall off when modified on the electrode. Nickel-based metal-organic frameworks (NiMOF) are a kind of MOFs synthesized by Ni2+ and 2-methylimidazole, which has a simple synthesis method and short time consumption. The unique Ni 2+ -N atom structure makes it have larger specific surface area and excellent thermal stability, chemical stability and catalytic activity. Therefore, g-C3N4 is compounded with Ni-MOF by a solvent hydrothermal method to prepare g-C3N4@NiMOF, and the composite material prepared by the solvent hydrothermal method can make NiMOF nanosheets grow uniformly on the blocky g-C3N4, reduce the agglomeration of the NiMOF nanosheets to a certain extent, improve the stability of the material, increase the specific surface area of the material, and improve the ECL stability of g-C3N4 and enhance the ECL intensity of the material.

[0005] Due to the good selectivity and stability of molecularly imprinted polymer (MIP), an electrochemiluminescence sensor based on molecular imprinting can selectively identify and detect target compounds. As a potential method for preparing molecularly imprinted films, electropolymerization is simple to operate and easy to control the thickness of the film. Glassy carbon electrode (GCE) is widely used in the production of molecularly imprinted electrochemiluminescence sensors due to its wide potential window and high stability. o-Phenylenediamine (o-PD) is a derivative of aniline, which can be synthesized into poly-o-phenylenediamine (p-(o-PD)) by electropolymerization. As a conductive polymer, p-(o-PD) has many amino groups and imino groups, which can provide more active sites, and it can realize the recognition of doped substances through doping-dedoping, which is an excellent material for constructing molecularly imprinted sensors. Therefore, o-PD is selected as the functional monomer in this study, and a molecularly imprinted electrochemiluminescence sensor for TRI is prepared by electropolymerizing o-PD and TRI on the surface of GCE. The hydrogen bond interaction between the amino and imino groups in p-(o-PD) and the hydroxyl groups in TRI molecules realizes the sensitive and selective recognition of TRI.

[0006] The MIP-p(o-PD) / g-C3N4@NiMOF / GCE sensor is obtained by dropping g-C3N4@NiMOF on the surface of bare GCE, electropolymerizing the functional monomer o-PD and the template molecule TRI on the surface of the modified electrode, and then immersing in KOH to elute the template molecule TRI in the polymer film. There is a hydrogen bond interaction between the p-(o-PD) of the sensor and the TRI molecules, and the imprinted cavity formed by the sensor specifically binds to the TRI molecules through hydrogen bond, realizing the detection of TRI. The performance of the MIP-p(o-PD) / g-C3N4@NiMOF / GCE sensor is tested by ECL method using a three-electrode system. The sensor has the advantages of high sensitivity, strong selectivity, good stability, and easy use, and has great application potential for the quantitative analysis of TRI, which is one of the ideal methods for detecting TRI. SUMMARY

[0007] The first object of the present application is to provide a preparation method of a molecular imprinting electrochemiluminescence sensor for selectively detecting TRI, and the second object is to provide an application method of the molecular imprinting electrochemiluminescence sensor for selectively detecting TRI.

[0008] The preparation method of the first object of the present application is to use MIP-p(o-PD) / g-C3N4@NiMOF / GCE as a working electrode, Ag / AgCl electrode as a reference electrode, and platinum wire electrode as an auxiliary electrode to form a three-electrode system. Based on the breaking and forming of hydrogen bonds between p-(o-PD) and TRI molecules in MIP-p(o-PD) / g-C3N4@NiMOF / GCE, TRI elution and rebinding are realized. By measuring the ECL response of the electrode after eluting TRI and rebinding TRI, quantitative detection of TRI is realized. The sensor has the advantages of high detection sensitivity, fast detection speed, good selectivity, simple operation, convenient carrying, etc.

[0009] The above technical objects of the present application are achieved by the following technical solutions:

[0010] The preparation method of the molecular imprinting electrochemiluminescence sensor for selectively detecting TRI provided by the present application uses MIP-p(o-PD) / g-C3N4@NiMOF / GCE as a working electrode. Due to the hydrogen bonds between the functional monomer o-PD and the template molecule TRI, a layer of p-(o-PD) and TRI imprinting film is formed on the electrode surface through electro-polymerization due to the hydrogen bond interaction. After washing the electrode surface with KOH solution, the hydrogen bonds between p-(o-PD) and TRI are broken and specific imprinting cavities are formed, which can specifically bind TRI molecules.

[0011] Further, the preparation method of the MIP-p(o-PD) / g-C3N4@NiMOF / GCE electrochemical sensor is: the glassy carbon electrode is polished, and then sequentially cleaned with nitric acid solution, anhydrous ethanol solution and deionized water for 30 minutes, and dried at room temperature to obtain a clean glassy carbon electrode for standby use; the DMF dispersion liquid of g-C3N4@NiMOF is taken by a microsyringe and modified on the surface of the pretreated glassy carbon electrode, and dried under an infrared lamp to obtain g-C3N4@NiMOF / GCE. The g-C3N4@NiMOF / GCE is placed in a PBS buffer solution containing o-PD and TRI at pH 6.0, and in a three-electrode system, the functional monomer and the template molecule are electropolymerized on the surface of the electrode by CV to obtain MIP-p(o-PD)-TRI / g-C3N4@NiMOF / GCE. The MIP-p(o-PD)-TRI / g-C3N4@NiMOF / GCE is soaked in a KOH solution to elute the template molecule TRI, and the electrode after eluting the template molecule MIP-p(o-PD) / g-C3N4@NiMOF / GCE can specifically bind to the TRI molecule through hydrogen bonds.

[0012] Further, the operation steps of the preparation method of the g-C3N4@NiMOF are:

[0013] S1. Melamine is placed in a crucible and heated to 550℃ in a muffle furnace for reaction; after the reaction is completed, it is naturally cooled to room temperature, and the obtained yellow block solid is ground into powder with a mortar to obtain g-C3N4;

[0014] wherein the heating speed is 2℃ / min -1 , and the reaction time is 4h;

[0015] S2. g-C3N4 is dissolved in methanol and uniformly dispersed by ultrasonic. Then, nickel nitrate hexahydrate and 2-methylimidazole are added to the above dispersion liquid, which is uniformly dispersed by ultrasonic, and then the mixed liquid is moved to a reaction kettle and reacted at 180℃ for 6h. After the reaction is completed, it is cooled to room temperature, centrifuged, washed with methanol, and vacuum dried to obtain g-C3N4@NiMOF powder;

[0016] wherein the molar ratio of nickel nitrate hexahydrate, 2-methylimidazole and g-C3N4 is 1:4:0.2-1:4:2; for example, the amount of g-C3N4 used is 0.05-0.5g; the amount of nickel nitrate hexahydrate used is 0.15-1.45g; and the amount of 2-methylimidazole used is 0.16-1.64g;

[0017] The preparation method of the molecularly imprinted polymerization liquid is: a certain amount of o-PD and TRI is accurately weighed and added to the prepared pH 6.0 0.1mol / L PBS buffer solution, and ultrasonically dissolved to prepare a PBS buffer solution containing o-PD and TRI;

[0018] The molar ratio of TRI to o-PD is 1:1-1:10; the concentration of TRI is fixed at 0.5 mmol / L, and the amount used is 3.24 mg; the concentration of o-PD is 0.5-5 mmol / L, and the amount used is 0.54-5.41 mg;

[0019] The diameter of the glassy carbon electrode used is 3 mm; the concentration of the DMF dispersion of the g-C3N4@NiMOF is 0.5-3.0 mg / mL, and the drop-casting amount is 2.5-10 μL; the electro-polymerization conditions are as follows: potential range: 0-1 V; scan rate: 50 mV / s; scan number: 10-30; supporting electrolyte: the ratio of the template molecule TRI to the functional monomer o-PD is 1:1-1:10, and further preferably the PBS buffer solution containing 3 mmol / L of o-PD and 0.5 mmol / L of TRI; the concentration of the eluent KOH is 0.1-1.0 mol / L; and the elution time is 5-25 min.

[0020] The application method of the second object of the application has the same effects.

[0021] The above technical effects of the application are achieved by the following technical scheme:

[0022] The application method of the molecular imprinting electrochemical luminescence sensor for selectively detecting TRI provided by the application uses MIP-p(o-PD) / g-C3N4@NiMOF / GCE as a working electrode, a platinum wire electrode as an auxiliary electrode, and Ag / AgCl as a reference electrode, and in a conventional three-electrode system, the ECL intensity of the modified electrode recombining different concentrations of TRI is tested by an electrochemical luminescence method, and TRI is quantitatively detected.

[0023] As a preferred embodiment of the above technical scheme, the specific steps are as follows:

[0024] A1. Preparation of a TRI standard solution with different concentrations:

[0025] A TRI solution with a concentration of 5×10 -5 mol / L is prepared by using a 0.1 mol / L PBS buffer solution with a pH of 6.0, and a series of TRI standard solutions with different concentrations are diluted, with the concentration range being 1×10 -9 -5×10 -5 mol / L;

[0026] A2. Drawing of a standard curve:

[0027] The MIP-p(o-PD) / g-C3N4@NiMOF / GCE is used as a working electrode, a platinum wire electrode is used as an auxiliary electrode, and an Ag / AgCl is used as a reference electrode to form a three-electrode system, the working electrode is immersed in a series of different concentrations of TRI standard solutions prepared in step A1 to recombine TRI, the recombination time of TRI is 5-30 min, and the luminescence intensity is detected with 0.1 mol / L PBS buffer solution containing 0.05 mol / L K2S2O8 as a blank solution; in the electrochemical window range of-1.6-0 V, the high voltage of the photomultiplier tube is 800 V, the scanning speed is 0.1 V / s, the cyclic voltammetry scanning is carried out, the potential-luminescence intensity curve (E-ECL) is recorded, the linear relationship between the luminescence intensity difference before and after the recombination of TRI and the logarithmic value of the TRI concentration is established, and the corresponding linear regression equation is obtained;

[0028] A3. Actual sample detection:

[0029] The dried triostin-containing sample is crushed by a powder mill, sieved, and weighed, deionized water is added under the condition of a solid-liquid ratio of 1:20 (g / mL), reflux extraction is carried out for 3 h, and then filtration is carried out, the obtained crude extract is diluted to volume. The extract is diluted with 0.1 mol / L PBS buffer solution with pH 6.0 to obtain a sample to be tested, the standard addition method is used to test the ECL of TRI in the actual sample, and the concentration of TRI in the sample to be tested is calculated according to the linear regression equation obtained in A2.

[0030] As a preferred technical solution of the above, the detection range of triostin is 1x10 -9 -5x10 -5 mol / L, and the minimum detection limit is 4.0x10 -10 mol / L.

[0031] In summary, the present application has the following beneficial effects:

[0032] The application discloses a preparation method of a molecular imprinting electrochemiluminescence sensor and application of the molecular imprinting electrochemiluminescence sensor in selective detection of TRI. The electrochemiluminescence sensor is constructed based on molecular imprinting p(o-PD) and g-C3N4@NiMOF, g-C3N4 is compounded with NiMOF, so that the NiMOF can grow uniformly on the surface of g-C3N4, the agglomeration of the NiMOF is reduced, the specific surface area of the material is increased, and the stability and ECL performance of the luminescent material g-C3N4 are improved. The molecular imprinting is achieved by modifying o-PD and TRI on the electrode through an electropolymerization method, and the surface of the electrode is formed with imprinting cavities by eluting TRI in the polymerization film through KOH, the imprinting cavities can be combined with TRI through hydrogen bonds to specifically recognize TRI. The molecular imprinting sensor has good selectivity to TRI and strong anti-interference capability. The application first proposes the molecular imprinting electrochemiluminescence method for detecting TRI, the molecular imprinting electrochemiluminescence method can replace traditional methods such as high performance liquid chromatography and nuclear magnetic resonance which have high equipment cost and long detection period, and has the advantages of high detection sensitivity, strong selectivity, fast detection speed, wide linear range and convenient use, and promotes the application of the molecular imprinting electrochemiluminescence sensor in detection of TRI. BRIEF DESCRIPTION OF DRAWINGS

[0033] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of the specification, illustrate embodiments of the application and, together with the description, serve to explain the principles of the application, and do not limit the application. In the drawings:

[0034] Figure 1 is a brief flow chart of preparation of an MIP-p(o-PD) / g-C3N4@NiMOF / GCE electrochemiluminescence sensor and detection of TRI;

[0035] Figure 2 is a scanning electron microscope image of a g-C3N4@NiMOF composite material prepared in Example 1;

[0036] Figure 3 is an ECL response graph of a molecular imprinting electrochemical sensor constructed by different ratios of template molecules TRI and functional monomers o-PD;

[0037] Figure 4 is an ECL curve of different modified electrodes (a. MIP-p(o-PD)-TRI / g-C3N4@NiMOF / GCE; b. MIP-p(o-PD) / g-C3N4@NiMOF / GCE after elution; c. MIP-p(o-PD) / g-C3N4@NiMOF / GCE after recombination of TRI) of the molecular imprinting electrochemical sensor in 0.1M PBS (pH 7.4) containing 0.05M K2S2O8;

[0038] Figure 5is the ECL curve of MIP-p(o-PD) / g-C3N4@NiMOF / GCE electrochemiluminescence sensor for detecting different concentrations of TRI (TRI concentration range: 1 x 10 -9 ~ 5 x 10 -5 mol / L);

[0039] Figure 6 is the calibration curve of MIP-p(o-PD) / g-C3N4@NiMOF / GCE electrochemiluminescence sensor for detecting different concentrations of TRI;

[0040] Figure 7 is the selectivity histogram of MIP-p(o-PD) / g-C3N4@NiMOF / GCE electrochemiluminescence sensor. DETAILED DESCRIPTION

[0041] In order to further illustrate the technical means and effects taken by the present application to achieve the predetermined object, the specific implementation, features and effects of the preparation method and application method of the molecularly imprinted electrochemiluminescence sensor for selectively detecting TRI according to the present application are described in detail as follows.

[0042] Example 1: Preparation method and application method of a molecularly imprinted electrochemiluminescence sensor for selectively detecting TRI.

[0043] Preparation method of a molecularly imprinted electrochemiluminescence sensor for selectively detecting TRI:

[0044] (1) Preparation method of g-C3N4@NiMOF and preparation method of molecularly imprinted polymer solution:

[0045] S1. Put 5 g of melamine in a crucible and heat to 550℃ at a heating rate of 2℃ / min in a muffle furnace for 4 h; after the reaction is completed, naturally cool to room temperature, and use a mortar to grind the obtained yellow block-shaped solid into powder to obtain g-C3N4; -1

[0046] S2. Dissolve 0.2 g of g-C3N4 in 25 mL of methanol and ultrasonically disperse uniformly; then, add 0.58 g of nickel nitrate hexahydrate and 0.66 g of 2-methylimidazole to the above dispersion liquid, ultrasonically disperse uniformly, and then move the mixed liquid to a 50 mL reaction kettle, and react at 180℃ for 6 h; wherein the molar ratio of nickel nitrate hexahydrate, 2-methylimidazole and g-C3N4 is 1:4:0.75; after the reaction is completed, cool to room temperature, centrifuge, and wash with methanol, and vacuum dry to obtain g-C3N4@NiMOF powder, the scanning electron microscope image of which is shown in Figure 2

[0047] ​​S3. Take 10 mL of 0.1 mol / L PBS buffer solution with pH 6.0 prepared in advance, accurately weigh a certain amount of o-PD and TRI into the solution and ultrasonic to dissolve to prepare o-PD and TRI containing PBS buffer solution;

[0048] The molar ratio of TRI to o-PD is 1:1, 1:2, 1:4, 1:6, 1:8, and 1:10.

[0049] (2) The preparation method of the MIP-p(o-PD) / g-C3N4@NiMOF / GCE is as follows:

[0050] The glassy carbon electrode is polished and ultrasonically cleaned with nitric acid solution, anhydrous ethanol solution and deionized water for 30 min, and then dried at room temperature to obtain a pretreated glassy carbon electrode; 5 μL of 1 mg / mL g-C3N4@NiMOF DMF dispersion is transferred to the surface of a clean glassy carbon electrode with a diameter of 3 mm using a microsyringe, and dried under an infrared lamp to obtain a g-C3N4@NiMOF / GCE. The g-C3N4@NiMOF / GCE is placed in a pH 6.0 PBS buffer solution containing o-PD and TRI, and a layer of imprinting film is polymerized on the surface of the electrode by CV (potential range: 0V-1V; scan rate: 50 mV / s; scan number: 20) in a three-electrode system to obtain MIP-p(o-PD)-TRI / g-C3N4@NiMOF / GCE; the MIP-p(o-PD)-TRI / g-C3N4@NiMOF / GCE is immersed in 0.5M KOH solution for 15 min to elute the template molecule TRI in the polymerized film to obtain MIP-p(o-PD) / g-C3N4@NiMOF / GCE; the prepared electrochemiluminescence sensor is named MIP-p(o-PD) / g-C3N4@NiMOF / GCE;

[0051] An application method of a molecular imprinting electrochemiluminescence sensor for selectively detecting TRI is provided.

[0052] MIP-p(o-PD) / g-C3N4@NiMOF / GCE is used as the working electrode, a platinum wire electrode is used as the auxiliary electrode, and Ag / AgCl is used as the reference electrode, and the ECL intensity of the modified electrode before and after rebinding of TRI is tested by cyclic voltammetry scanning (electrochemical window: -1.6V-0V; photomultiplier high voltage: 800V; scan rate: 0.1V / s) in a three-electrode system.

[0053] The ECL signals of the molecular imprinting electrochemiluminescence sensors prepared by different ratios of template molecule TRI to functional monomer o-PD (1:1, 1:2, 1:4, 1:6, 1:8, and 1:10) are compared for detecting TRI, as shown in Table 1.Figure 3 As shown, when the ratio of template molecule TRI to functional monomer o-PD is 1:6, the ECL quenching value is the largest, so the optimal ratio of template molecule TRI to functional monomer o-PD is 1:6;

[0054] According to the optimal ratio of template molecule TRI to functional monomer o-PD, the molecularly imprinted electrochemiluminescence sensor for detecting TRI is prepared, and the modified electrode after rebinding TRI has a lower ECL intensity than that without binding TRI, that is, the ECL quenching value of the sensor for detecting triostin is larger, and the results are shown in Figure 4 As shown in b and c of the figure, it is indicated that the electrochemiluminescence sensor constructed by MIP-p(o-PD) / g-C3N4@NiMOF / GCE has higher sensitivity.

[0055] As a preferred embodiment of the above technical solution, the specific steps are as follows:

[0056] A1. Preparation of TRI standard solution with different concentrations:

[0057] The TRI is prepared into a 5×10 -5 mol / L solution by using 0.1 mol / L PBS buffer solution with pH 6.0, and a series of TRI standard solutions with different concentrations are diluted, and the concentration range is 1×10 -9 ~ 5×10 -5 mol / L;

[0058] A2. Drawing of standard curve:

[0059] The MIP-p(o-PD) / g-C3N4@NiMOF / GCE is used as a working electrode, a platinum wire electrode is used as an auxiliary electrode, and an Ag / AgCl is used as a reference electrode to form a three-electrode system, the working electrode is immersed in a series of TRI standard solutions with different concentrations prepared in step A1 for a certain time, and the luminescence intensity is detected by using 0.1 mol / L PBS buffer solution with pH 7.4 containing 0.05 mol / L K2S2O8 as a blank solution; in the electrochemical window range of -1.6~0V, the high voltage of the photomultiplier tube is 800V, the scanning speed is 0.1V / s, the cyclic voltammetry scanning is carried out, the potential-luminescence intensity curve (E-ECL) is recorded, and the linear relationship between the luminescence intensity difference (△ECL) before and after rebinding TRI and the logarithm value of the TRI concentration is established to obtain the corresponding linear regression equation; when the TRI concentration is between 1×10 -9 ~ 5×10 -5 mol / L, the ECL intensity decreases with the increase of the concentration, as shown in Figure 5 , and the △ECL has a good linear relationship with the logarithm of the TRI concentration Figure 6), the linear regression equation is △ECL=4395.13Log C(mol / L)+45427.93, the correlation coefficient (R 2 ) is 0.9982, and the detection limit is 4.0×10 -10 mol / L;

[0060] A3. Actual sample detection:

[0061] 5g of the leaves of L. polycephalum was added to 100mL of deionized water under the condition of a solid-liquid ratio of 1:20, and then reflux extraction was performed for 3h. After extraction, the obtained crude extract was filtered and then diluted to 100mL. 0.1mL of the extract was diluted to 100mL with a PBS buffer solution with a pH of 6.0 and a concentration of 0.1mol / L to obtain a sample to be detected, which was used for ECL detection. The concentration of TRI in the sample to be detected was calculated according to the linear regression equation obtained in A2, and the results are shown in Table 1.

[0062] In this embodiment 1, g-C3N4@NiMOF and molecularly imprinted p(o-PD) are used as electrode modification materials. Based on the high ECL performance of g-C3N4, the strong chemical stability and good catalytic performance of NiMOF, and the strong and stable ECL performance of the composite material of the two, the selectivity of the sensor is improved by the molecular imprinting technology, so that the sensor can specifically detect TRI and has excellent anti-interference ability. The MIP-p(o-PD) / g-C3N4@NiMOF / GCE electrochemiluminescence sensor constructed by combining g-C3N4@NiMOF and molecularly imprinted poly-o-phenylenediamine has better performance in detecting TRI, higher sensitivity, better stability, stronger selectivity, wider linear range and lower detection limit.

[0063] Comparative example 1: a preparation method and application method of a molecularly imprinted electrochemiluminescence sensor for selectively detecting TRI.

[0064] A preparation method of a molecularly imprinted electrochemiluminescence sensor for selectively detecting TRI:

[0065] (1) a preparation method of g-C3N4@NiMOF2 and a preparation method of a molecularly imprinted polymer solution:

[0066] The preparation method of g-C3N4 is the same as S1 in step (1) of embodiment 1.

[0067] The preparation method of g-C3N4@NiMOF2 is the same as S2 in step (1) of embodiment 1. The molar ratio of nickel nitrate hexahydrate, 2-methylimidazole and g-C3N4 is 1:4:3, and the mass of nickel nitrate hexahydrate, 2-methylimidazole and g-C3N4 is 0.58g, 0.66g and 0.77g respectively. The prepared material is named g-C3N4@NiMOF2.

[0068] The preparation method of the molecular imprinting polymer solution is the same as S3 of step (1) of Example 1.

[0069] The preparation method of the MIP-p(o-PD) / g-C3N4@NiMOF2 / GCE is as follows:

[0070] The preparation method of the MIP-p(o-PD) / g-C3N4@NiMOF2 / GCE is the same as step (2) of Example 1, wherein the dispersion solution taken by the microsyringe is a 1 mg / mL g-C3N4@NiMOF2 DMF dispersion solution.

[0071] An application method of the molecular imprinting electrochemiluminescence sensor for selectively detecting TRI:

[0072] The MIP-p(o-PD) / g-C3N4@NiMOF2 / GCE is used as a working electrode, a platinum wire electrode is used as an auxiliary electrode, and an Ag / AgCl electrode is used as a reference electrode, and the ECL intensity before and after the recombination of TRI is tested by cyclic voltammetry scanning (electrochemical window: -1.6 V-0 V; photomultiplier high voltage: 800 V; scan rate: 0.1 V / s) in a three-electrode system.

[0073] The specific application method is the same as that of Example 1, and the results of the sensor detecting TRI in actual samples are shown in Table 1.

[0074] Comparative Example 2: A preparation method and application method of a molecular imprinting electrochemiluminescence sensor for selectively detecting TRI.

[0075] A preparation method of a molecular imprinting electrochemiluminescence sensor for selectively detecting TRI:

[0076] (1) The preparation method of g-C3N4@NiMOF3 and the preparation method of the molecular imprinting polymer solution are as follows:

[0077] The preparation method of g-C3N4 is the same as S1 of step (1) of Example 1.

[0078] The preparation method of g-C3N4@NiMOF3 is the same as S2 of step (1) of Example 1, wherein the molar ratio of nickel nitrate hexahydrate, 2-methylimidazole and g-C3N4 is 1:4:0.1, and the mass of nickel nitrate hexahydrate, 2-methylimidazole and g-C3N4 is 0.58 g, 0.66 g and 0.026 g, respectively, and the prepared material is named g-C3N4@NiMOF3.

[0079] The preparation method of the molecular imprinting polymer solution is the same as S3 of step (1) of Example 1.

[0080] (2) The preparation method of the MIP-p(o-PD) / g-C3N4@NiMOF3 / GCE is as follows:

[0081] The preparation method of the MIP-p(o-PD) / g-C3N4@NiMOF3 / GCE is the same as step (2) of Example 1, wherein the micropipette is used to remove 1 mg / mL g-C3N4@NiMOF3 DMF dispersion liquid;

[0082] An application method of the molecular imprinting electrochemiluminescence sensor for selectively detecting TRI:

[0083] MIP-p(o-PD) / g-C3N4@NiMOF3 / GCE is used as a working electrode, a platinum wire electrode is used as an auxiliary electrode, and Ag / AgCl is used as a reference electrode, and the ECL intensity before and after the recombination of TRI is tested by cyclic voltammetry scanning (electrochemical window: -1.6V-0V; photomultiplier high voltage: 800V; scan rate: 0.1V / s) in a three-electrode system.

[0084] The specific application method is the same as that of Example 1, and the results of the sensor detecting TRI in actual samples are shown in Table 1.

[0085] Preparation method and application method of an electrochemiluminescence sensor for detecting trilobatin.

[0086] A preparation method of an electrochemiluminescence sensor for detecting trilobatin:

[0087] (1) Preparation method of g-C3N4 and NiMOF and preparation method of a molecular imprinting polymer solution:

[0088] The preparation method of g-C3N4 is the same as S1 of step (1) of Example 1.

[0089] The preparation method of NiMOF is as follows: 0.58 g of nickel nitrate hexahydrate and 0.66 g of 2-methylimidazole are dissolved in 25 mL of methanol, the mixture is transferred to a 50 mL reaction kettle, and the reaction is carried out at 180℃ for 6 h; after the reaction is completed, it is cooled to room temperature, centrifuged, and washed with methanol, and vacuum dried to obtain NiMOF powder;

[0090] The preparation method of the molecular imprinting polymer solution is the same as S3 of step (1) of Example 1.

[0091] (2) The preparation method of the MIP-p(o-PD) / NiMOF / g-C3N4 / GCE is as follows:

[0092] The glassy carbon electrode was polished and cleaned with nitric acid solution, anhydrous ethanol solution and deionized water for 30 min under ultrasonic, and dried at room temperature to obtain a pretreated glassy carbon electrode; 5 μL of 1 mg / mL g-C3N4 DMF dispersion was transferred to the surface of a clean glassy carbon electrode with a diameter of 3 mm using a microsyringe, and dried under an infrared lamp to obtain a g-C3N4 / GCE; 5 μL of 1 mg / mL NiMOF DMF dispersion was transferred to the electrode using a microsyringe to obtain a NiMOF / g-C3N4 / GCE; the NiMOF / g-C3N4 / GCE was placed in a PBS buffer solution containing o-PD and TRI at pH 6.0, and a layer of imprinted film was polymerized on the surface of the electrode by CV (potential range: 0-1 V; scan rate: 50 mV / s; scan number: 20) in a three-electrode system to obtain a MIP-p(o-PD)-TRI / NiMOF / g-C3N4 / GCE; the MIP-p(o-PD)-TRI / NiMOF / g-C3N4 / GCE was soaked in 0.5 M KOH solution for 15 min to elute the template molecule TRI in the polymerized film to obtain a MIP-p(o-PD) / NiMOF / g-C3N4 / GCE; the prepared electrochemiluminescence sensor was named MIP-p(o-PD) / NiMOF / g-C3N4 / GCE;

[0093] An application method of the electrochemiluminescence sensor for detecting TRI:

[0094] MIP-p(o-PD) / NiMOF / g-C3N4 / GCE was used as a working electrode, a platinum wire electrode was used as an auxiliary electrode, and Ag / AgCl was used as a reference electrode, and the ECL intensity of the modified electrode before and after rebinding of TRI was tested by cyclic voltammetry scanning (electrochemical window: -1.6-0 V; photomultiplier high voltage: 800 V; scan rate: 100 mV / s) in a three-electrode system;

[0095] The specific application method was the same as in Example 1, and the results of the sensor in detecting TRI in actual samples are shown in Table 1.

[0096] Preparation method and application method of an electrochemiluminescence sensor for detecting TRI.

[0097] Preparation method of an electrochemiluminescence sensor for detecting TRI:

[0098] (1) Preparation method of g-C3N4@NiMOF:

[0099] The preparation method of g-C3N4@NiMOF was the same as S1-S2 in step (1) of Example 1.

[0100] (2) The preparation method of the N-g-C3N4@NiMOF / GCE is:

[0101] The glassy carbon electrode was polished and ultrasonically cleaned with nitric acid solution, anhydrous ethanol solution and deionized water for 30 min, and then dried at room temperature to obtain a pretreated glassy carbon electrode; 5 μL of 1 mg / mL g-C3N4@NiMOF DMF dispersion liquid was transferred to the surface of the treated glassy carbon electrode with a diameter of 3 mm by using a microsyringe, and dried under an infrared lamp to obtain a g-C3N4@NiMOF / GCE; the g-C3N4@NiMOF / GCE was immersed in 0.5 M KOH solution for 15 min to obtain an N-g-C3N4@NiMOF / GCE; and the prepared electrochemiluminescence sensor was named N-g-C3N4@NiMOF / GCE;

[0102] An application method of the electrochemiluminescence sensor for detecting TRI:

[0103] Under a three-electrode system, the ECL intensity of the modified electrode before and after rebinding of TRI was tested by cyclic voltammetry scanning (electrochemical window: -1.6-0 V; photomultiplier high voltage: 800 V; scan rate: 100 mV / s) with N-g-C3N4@NiMOF / GCE as the working electrode, a platinum wire electrode as the auxiliary electrode, and Ag / AgCl as the reference electrode;

[0104] The specific application method is the same as that in Example 1, and the results of the sensor in detecting TRI in actual samples are shown in Table 1.

[0105] Comparative Example 5: A preparation method and application method of a non-molecularly imprinted electrochemiluminescence sensor for detecting triptolide.

[0106] A preparation method of a non-molecularly imprinted electrochemiluminescence sensor for detecting triptolide:

[0107] (1) The preparation method of g-C3N4@NiMOF and the preparation method of a non-molecularly imprinted polymer solution are:

[0108] The preparation method of g-C3N4@NiMOF is the same as S1-S2 in step (1) of Example 1.

[0109] The preparation method of the non-molecularly imprinted polymer solution is: 10 mL of 0.1 mol / L PBS buffer solution with pH 6.0 was prepared, 3.24 mg of o-PD was accurately weighed and added to the solution and ultrasonically dissolved to prepare a PBS buffer solution containing 3×10 -3 mol / L of o-PD;

[0110] (2) The preparation method of the NIP-p(o-PD) / g-C3N4@NiMOF / GCE is:

[0111] The glassy carbon electrode was polished and cleaned with nitric acid solution, anhydrous ethanol solution and deionized water for 30 min under ultrasonic, and dried at room temperature to obtain a pretreated glassy carbon electrode; 5 μL of 1 mg / mL g-C3N4@NiMOF DMF dispersion liquid was moved to the surface of the pretreated glassy carbon electrode with a diameter of 3 mm by using a microsyringe, and dried under an infrared lamp to obtain a g-C3N4@NiMOF / GCE; the g-C3N4@NiMOF / GCE was placed in a PBS buffer solution containing 3×10 -3 mol / L o-PD, and a thin film was polymerized on the surface of the electrode by CV (potential range: 0V-1V; scan rate: 50 mV / s; scan number: 20) under a conventional three-electrode system; in the same molecular imprinting elution step, the modified electrode was immersed in 0.5M KOH solution for 15 min for elution to obtain a NIP-p(o-PD) / g-C3N4@NiMOF / GCE; the prepared electrochemiluminescence sensor was named NIP-p(o-PD) / g-C3N4@NiMOF / GCE;

[0112] An application method of a non-molecular imprinting electrochemiluminescence sensor for detecting TRI:

[0113] NIP-p(o-PD) / g-C3N4@NiMOF / GCE was used as a working electrode, a platinum wire electrode was used as an auxiliary electrode, and Ag / AgCl was used as a reference electrode, and the ECL intensity of the modified electrode before and after recombination of TRI was tested by cyclic voltammetry scanning (electrochemical window: -1.6V-0V; photomultiplier high voltage: 800V; scan rate: 100 mV / s) under a three-electrode system;

[0114] The specific application method was the same as that in Example 1, and the results of the sensor in detecting TRI in actual samples were listed in Table 1.

[0115] Preparation method and application method of an electrochemiluminescence sensor for detecting triptolide.

[0116] Preparation method of an electrochemiluminescence sensor for detecting triptolide:

[0117] (1) Preparation method of g-C3N4@MnMOF and preparation method of a molecular imprinting polymerization solution:

[0118] The preparation method of g-C3N4 was the same as S1 in step (1) of Comparative Example 1;

[0119] The preparation method of g-C3N4@MnMOF is as follows: 0.2 g of g-C3N4 is dispersed in 30 mL of DMF, and ultrasonic dispersion is uniform. Then, 0.25 g of manganese chloride tetrahydrate and 0.31 g of 1,3,5-benzene tricarboxylic acid are added to the dispersion liquid, and ultrasonic dispersion is uniform. Then, the mixture is moved to a 50 mL reaction kettle, and reaction is carried out at 140 DEG C for 12 h. After reaction, cooling is carried out to room temperature, centrifugation is carried out, and washing is carried out with methanol, and vacuum drying is carried out, so that g-C3N4@MnMOF powder is obtained;

[0120] The preparation method of the molecular imprinting polymerization liquid is the same as S3 in step (1) of Example 1.

[0121] The preparation method of MIP-p(o-PD) / g-C3N4@MnMOF / GCE is as follows:

[0122] The preparation method of MIP-p(o-PD) / g-C3N4@MnMOF / GCE is the same as step (2) of Example 1, and the dispersion liquid taken by the microsyringe is 1 mg / mL g-C3N4@MnMOF DMF dispersion liquid.

[0123] The application method of the electrochemiluminescence sensor for detecting TRI is as follows:

[0124] MIP-p(o-PD) / g-C3N4@MnMOF / GCE is used as a working electrode, a platinum wire electrode is used as an auxiliary electrode, and Ag / AgCl is used as a reference electrode. In a three-electrode system, the ECL intensity before and after rebinding of TRI is tested by cyclic voltammetry scanning (electrochemical window: -1.6-0 V; photomultiplier high voltage: 800 V; scanning speed: 100 mV / s).

[0125] The specific application method is the same as that in Example 1, and the results of the sensor in detecting TRI in actual samples are shown in Table 1.

[0126] Table 1: Detection results of Lithocarpus polystarchus leaf samples

[0127]

[0128]

[0129] As shown in Table 1, the standard addition recovery rate of the MIP-p(o-PD) / g-C3N4@NiMOF / GCE for detecting the leaf sample of Lithocarpus polystachyus Rehder is 96.32% to 103.45%, and the relative standard deviation is less than 5%, indicating that the detection effect is good. According to the above experimental results, it can be obviously observed that without using the g-C3N4@NiMOF composite material prepared in the molar ratio range of nickel nitrate hexahydrate, 2-methyl imidazole and g-C3N4, and without using the template molecule TRI and the functional monomer o-PD to construct the molecularly imprinted polymer film, the sensor cannot detect TRI in the sample after assembling the sensing element, so the sensor of the application can be used for detecting TRI in the leaf sample of Lithocarpus polystachyus Rehder.

[0130] Selective detection: a selective application method of an electrochemical sensor for detecting trilobatin.

[0131] A selective application method of an electrochemical sensor for detecting trilobatin:

[0132] MIP-p(o-PD) / g-C3N4@NiMOF / GCE is used as a working electrode, a platinum wire electrode is used as an auxiliary electrode, and Ag / AgCl is used as a reference electrode, 1×10 -5 mol / L trilobatin is used as a control, phlorizin, glucose, sucralose and ascorbic acid of the same concentration are selected as interference substances, and the ECL intensity of the modified electrode before and after mixing the interference substances with all the interference substances and TRI is tested by cyclic voltammetry scanning (electrochemical window: -1.6 to 0V; photomultiplier high voltage: 800V; scan rate: 100mV / s), and the results are shown in Figure 7 As shown in Table 1, the standard addition recovery rate of the MIP-p(o-PD) / g-C3N4@NiMOF / GCE for detecting the leaf sample of Lithocarpus polystachyus Rehder is 96.32% to 103.45%, and the relative standard deviation is less than 5%, indicating that the detection effect is good. According to the above experimental results, it can be obviously observed that without using the g-C3N4@NiMOF composite material prepared in the molar ratio range of nickel nitrate hexahydrate, 2-methyl imidazole and g-C3N4, and without using the template molecule TRI and the functional monomer o-PD to construct the molecularly imprinted polymer film, the sensor cannot detect TRI in the sample after assembling the sensing element, so the sensor of the application can be used for detecting TRI in the leaf sample of Lithocarpus polystachyus Rehder.

[0133] Based on the above verification, it can be known that the application constructs a new method capable of rapidly, sensitively and selectively detecting TRI based on the electrochemiluminescence response of TRI to MIP-p(o-PD) / g-C3N4@NiMOF / GCE. Since g-C3N4 has high ECL performance, NiMOF has strong chemical stability and good catalytic performance, the material obtained by compounding the two has strong and stable ECL performance. There is a hydrogen bond action between the amino group in the molecularly imprinted p-(o-PD) and the hydroxyl group in the TRI molecule, the imprinting cavity formed by the sensor specifically binds the TRI molecule through the hydrogen bond, which improves the selectivity of the sensor and makes it have excellent anti-interference ability. When there is a small amount of TRI, there is a hydrogen bond action between p-(o-PD) in the MIP-p(o-PD) / g-C3N4@NiMOF / GCE system and TRI, and the analyte TRI is adsorbed in the imprinting cavity of the modified electrode, so that the ECL response of the sensor is reduced. It is found through research that the quenching value of the ECL intensity of the MIP-p(o-PD) / g-C3N4@NiMOF / GCE electrochemiluminescence sensor for detecting TRI has a good linear relationship with the logarithm of the concentration of TRI. The molecularly imprinted electrochemiluminescence method used in the application not only has the advantages of high sensitivity, fast detection speed, good selectivity, wide linear range, low detection limit and the like, but also has great application potential for quantitative detection and analysis of TRI by using the molecularly imprinted electrochemiluminescence sensor.

[0134] The above is only a preferred embodiment of the application, and does not limit the application in any form. Although the application has been disclosed as above, it is not intended to limit the application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the application, and any simple modification, equivalent change and modification of the above embodiments based on the technical essence of the application are still within the scope of the technical solution of the application.

Claims

1. A molecularly imprinted electrochemiluminescence sensor for selective detection of TRI, characterized in that, The MIP-p(o-PD) / g-C3N4@NiMOF / GCE is used as a molecular imprinting sensor for detecting TRI by an electrochemiluminescence method, and TRI is trilobatin. The preparation method of the molecular imprinting electrochemiluminescence sensor is as follows: A glassy carbon electrode is polished and sequentially cleaned by ultrasonic with nitric acid, anhydrous ethanol and deionized water, and then a g-C3N4@NiMOF dispersion liquid is modified on the surface of the pretreated glassy carbon electrode, and the g-C3N4@NiMOF / GCE is obtained after drying under an infrared lamp; the g-C3N4@NiMOF / GCE is placed in a phosphate buffer solution containing o-phenylenediamine (o-PD) and TRI, and a functional monomer o-PD is electro-polymerized with a template molecule TRI on the surface of the modified electrode by a cyclic voltammetry method in a three-electrode system, so as to obtain the MIP-p(o-PD)-TRI / g-C3N4@NiMOF / GCE; the MIP-p(o-PD)-TRI / g-C3N4@NiMOF / GCE is soaked in KOH to elute the template molecule TRI in the polymerized film, so as to obtain the MIP-p(o-PD) / g-C3N4@NiMOF / GCE sensor. The preparation method of the g-C3N4@NiMOF includes the following operation steps: S1. Melamine is placed in a crucible and heated to 550 ℃ in a muffle furnace for reaction; after the reaction is completed, the yellow block solid obtained is naturally cooled to room temperature, and then is ground into powder by using a mortar to obtain g-C3N4; S2. The g-C3N4 is dissolved in methanol and ultrasonically dispersed uniformly, then nickel nitrate hexahydrate and 2-methyl imidazole are added into the dispersion liquid, and the mixture is ultrasonically dispersed uniformly, then is moved into a reaction kettle, and is reacted at 180 ℃ for 6 h; after the reaction is completed, the mixture is cooled to room temperature, centrifuged, washed with methanol and vacuum dried to obtain g-C3N4@NiMOF. 2.The molecularly imprinted electrochemiluminescence sensor for selectively detecting TRI according to claim 1, wherein, The molar ratio of nickel nitrate hexahydrate, 2-methyl imidazole and g-C3N4 is 1:4:0.2-1:4:

2. 3.The molecularly imprinted electrochemiluminescence sensor for selectively detecting TRI according to claim 1, wherein, The diameter of the glassy carbon electrode used is 3 mm; the concentration of the g-C3N4@NiMOF dispersion liquid is 0.5-3.0 mg / mL; and the drop coating amount of the g-C3N4@NiMOF dispersion liquid is 2.5-10 μL. 4.The molecularly imprinted electrochemiluminescence sensor for selectively detecting TRI according to claim 1, wherein, The preparation of the phosphate buffer solution containing o-PD and TRI: o-PD and TRI are weighed and added into a prepared 0.1 mol / L PBS buffer solution with pH 6.0, and then are ultrasonically dissolved to prepare a PBS buffer solution containing o-PD and TRI; The concentration of TRI is 0.5 mmol / L; and the molar ratio of TRI to o-PD is 1:1-1:

10. 5.The molecularly imprinted electrochemiluminescence sensor for selectively detecting TRI according to claim 1, wherein, The electro-polymerization conditions are as follows: potential range: 0-1 V; scan rate: 50 mV / s; and scan number: 10-30. 6.The molecularly imprinted electrochemiluminescence sensor for selectively detecting TRI according to claim 1, wherein, The concentration of KOH is 0.1-1.0 mol / L; and the elution time is 5-25 min.

7. The use of a molecularly imprinted electrochemiluminescent sensor for the selective detection of TRI, characterized by: The MIP-p(o-PD) / g-C3N4@NiMOF / GCE of any one of claims 1-6 is used as a working electrode, a platinum wire electrode is used as an auxiliary electrode, and Ag / AgCl is used as a reference electrode, an ECL intensity of the modified electrode recombined with different concentrations of TRI is tested by an electrochemiluminescence method in a three-electrode system to realize detection of the concentration of TRI.

8. The method of claim 7, wherein the method comprises the steps of: (a) providing a molecularly imprinted electrochemiluminescent sensor for selective detection of TRI; (b) contacting the sensor with a sample suspected of containing TRI; and (c) detecting the presence of TRI in the sample. The specific steps are as follows: A1. Preparation of TRI standard solution with different concentrations: TRI was prepared into 5 x 10 -5 mol / L solution with 0.1 mol / L PBS buffer solution of pH 6.0, and a series of different concentrations of TRI standard solution was diluted, with the concentration ranging from 1 x 10 -9 ~5 x 10 -5 mol / L; A2. Drawing of a standard curve: The MIP-p(o-PD) / g-C3N4@NiMOF / GCE is used as a working electrode, a platinum wire electrode is used as an auxiliary electrode, and Ag / AgCl is used as a reference electrode to form a three-electrode system, the working electrode is immersed in a series of TRI standard solutions with different concentrations prepared in step A1 to recombine TRI, the recombination time is 5-30 min, and the luminescence intensity is detected with a blank solution of 0.1 mol / L PBS buffer solution containing 0.05 mol / L K2S2O8 at pH 7.4; in an electrochemical window range of-1.6-0 V, the high voltage of a photomultiplier tube is 800 V, the scanning speed is 0.1 V / s, cyclic voltammetry scanning is performed, the potential-luminescence intensity curve (E-ECL) is recorded, a linear relationship between the luminescence intensity difference before and after recombination of TRI and the logarithmic value of the concentration of TRI is established, and a corresponding linear regression equation is obtained; A3. Detection of an actual sample: The sample to be detected is crushed, sieved, weighed, and added to deionized water under the condition of a solid-liquid ratio of 1:20, extracted by reflux for 3 h, and then filtered, and the obtained crude extract is diluted to volume; The extract is diluted with a PBS buffer solution with pH 6.0 and a concentration of 0.1 mol / L to obtain a sample to be detected, a standard addition method is used to test the TRI in the actual sample by ECL, and the concentration of TRI in the sample to be detected is calculated according to the linear regression equation obtained in A2.

9. The method of using the molecularly imprinted electrochemiluminescent sensor for selective detection of TRI according to claim 8, wherein, The linear range of the sensor for TRI was 1 x 10 -9 -5 x 10 -5 -6 mol / L; the lowest detection limit was 4.0 x 10 -10 -6 mol / L.

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