Method and application for synthesizing a rare Eu(II)-MOF and constructing a near-infrared sensor as an electroluminescent probe

Abstract

The present invention discloses a preparation method of Eu(II)-MOF without the protection of reducing gas and its application in constructing an electroluminescent sensor for detecting novel environmental estrogens using this material as a near-infrared probe, belonging to the technical fields of environmental pollution prevention and control, electroluminescent sensing, nanomaterials, and metal-organic framework materials. The main steps are to use 1,10-phenanthroline and europium chloride as raw materials to prepare Eu(II)-MOF as a luminescent probe by hydrothermal method with the assistance of a reducing agent, and then use a two-step method to synthesize Fe3O4-Ag nanorods as a substrate material to construct a near-infrared competitive electroluminescent sensor. The raw materials used in the preparation of this material have low cost, the preparation process is simple, the reaction energy consumption is low, and it has industrial application prospects. Moreover, the constructed near-infrared electroluminescent sensor can work stably and efficiently under environments such as high temperature, high pressure, and heavy pollution, is suitable for environmental pollution detection, and has strong practical value.

Description

Technical Field

[0001] The present invention relates to a method for preparing Eu(II)-MOF without the protection of reducing gas and an application of constructing an electroluminescent sensor for detecting novel environmental estrogens based on this material as a near-infrared probe, belonging to the technical fields of environmental pollution prevention and control, electroluminescent sensing, nanomaterials, and metal-organic framework materials. Background Technique

[0002] With the improvement of technology and the living standards of humans, the use of products such as antibiotics, painkillers, antibacterial drugs, and sunscreens has become more and more popular. This has led to the detection of steroid estrogens that were originally only supposed to exist in small medicine cabinets and makeup bags in water bodies such as rivers, lakes, and coastal waters. Although the content of this novel environmental estrogen in water bodies is very low, due to its synergistic effect in water, it will have an adverse impact on the health of organisms and humans in the long run. This novel environmental estrogen is difficult to degrade and easy to accumulate, and it will interfere with the endocrine systems of humans and animals, thus causing abnormal effects in many aspects such as the reproductive development, immune system, and nervous system of the body, such as the increase in the incidence of human testicular cancer, prostate cancer, breast cancer, and uterine cancer, the frequent occurrence of hermaphroditism or feminization in wild fish, and even infant deformities and hermaphrodites. Therefore, it is of great significance to be able to quickly and efficiently detect trace amounts of novel environmental estrogens in water bodies for human health and life safety.

[0003] Currently, electrochemical, surface-enhanced Raman scattering, surface plasmon resonance, electroluminescence, etc. have been used to detect novel environmental estrogens. Among them, electroluminescent sensors have the advantages of both chemiluminescence and electrochemical analysis, such as low background signal, high sensitivity, simple operation, good reproducibility, in-situ detection, etc. Compared with traditional electroluminescent sensors, sensors with near-infrared luminescence characteristics can avoid damaging the sample, and at the same time have stronger environmental tolerance and can achieve immunoassay under harsh conditions (such as high temperature and high pressure, heavy pollution, etc.). Therefore, they can better meet the needs of environmental pollution analysis. In electroluminescent sensors, selecting a material with excellent luminescence performance as the light emitter can greatly improve the performance of the constructed sensor. Due to the characteristics of tunable luminescence performance, long luminescence lifetime, and strong energy transfer ability of lanthanide metals, they are widely prepared as luminescent materials for use in electroluminescence. However, the narrow absorption cross-section results in low absorption efficiency, so it cannot emit light efficiently by itself. To solve the above problems, it is used as a metal center to coordinate with organic ligands to form lanthanide metal-organic frameworks (Ln-MOFs). The ligand that absorbs light transfers the energy to the lanthanide ion (Ln 3+ ), and then Ln 3+ releases the energy in the form of light. By embedding the rigid skeleton of the ligand, the fluorescence emission and quantum yield of Ln-MOFs are higher than those of single Ln 3+It has increased several times, and at the same time, due to the reduced influence of the coordination field and electric field, its stability has been greatly improved. These advantages make Ln-MOFs potentially have high performance in analytical detection. Among them, the europium element (Eu) has abundant valence electrons in the f orbital, and the 4 f –4 f transition causes it to emit light in the visible and infrared regions. However, not all Eu-MOFs have both near-infrared and efficient luminescence functions, and the vast majority are Eu(III)-MOFs, whose instantaneous luminescence intensity is lower than that of Eu(II)-MOFs. In addition, the 5 2+ orbit of Eu d is exposed to the environment, making the 4 f 7 →4 f 6 5 d 1 transition strongly affected by the environment. The resulting strong visible light color change brings convenience to environmental analysis and is convenient for naked-eye real-time detection. In addition, the high instantaneous luminescence efficiency of Eu 2+ can quickly respond to the detected substances and is more suitable for detection and analysis applications. Therefore, finding a Eu(II)-MOF with high luminescence efficiency in the near-infrared region as a luminescent body to construct an electroluminescent sensor can better achieve the efficient and sensitive detection of new environmental pollutants in water bodies.

[0004] Facing this situation, in recent years, some research groups have achieved some results in the preparation of Eu(II)-MOFs. For example, the Liu research group synthesized a new macrocyclic ligand using tris(2-aminoethyl)amine as a raw material and coordinated it with Eu 2+ to form aza-salt MOF, while achieving high electroluminescence efficiency and stability in air. The Albrecht-Schönzart research group synthesized a nine-coordinated divalent Eu-MOF using the synthesized 2.2.2B cryptand macrocyclic ligand, which greatly improved the stability while ensuring high fluorescence intensity. Although the successful preparation of Eu(II)-MOFs has been achieved, due to Eu 2+ is extremely easy to be oxidized to Eu 3+, the preparation conditions of Eu(II)-MOFs are relatively stringent, requiring a large amount of nitrogen or argon to create a long-term reducing atmosphere, which not only increases the cost but also increases the experimental operation level and risk. Moreover, the few successfully prepared Eu(II)-MOFs have also been less applied in the field of electroluminescence. Therefore, it is of great significance and innovation to design and synthesize a Eu(II)-MOF with high luminous efficiency and strong stability for electroluminescence. In this development, Eu(II)-MOF materials were simply and controllably prepared without the protection of reducing gases. At the same time, Fe3O4-Ag nanorods were synthesized as catalysts and substrate materials to construct an electroluminescent sensor, that is, the synthesis of a rare Eu(II)-MOF and the construction of an efficient near-infrared environmental detection platform as an electroluminescent probe. Summary of the Invention

[0005] One of the technical tasks of the present invention is to make up for the deficiencies of the prior art and provide a simple and controllable method for preparing Eu(II)-MOF materials, that is, a method for preparing Eu(II)-MOF without the protection of reducing gases. The raw materials used in this method have low cost, simple preparation process, low reaction energy consumption, and high operation safety, and have industrial application prospects.

[0006] The second technical task of the present invention is to provide the use of the Eu(II)-MOF material prepared by the simple and controllable method, that is, using the Eu(II)-MOF as an electroluminescent probe to construct a sensor for trace detection of environmental estrogens. The Eu(II)-MOF has good near-infrared electroluminescent properties, enabling the constructed sensor to work efficiently and stably in a severely polluted environment, and has certain practical value.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] 1. Synthesis of a rare Eu(II)-MOF and construction of a near-infrared sensor as an electroluminescent probe, the steps are as follows:

[0009] Dissolve 0.257 - 0.259 g of europium chloride hexahydrate and 0.197 - 0.199 g of 1,10-phenanthroline in 9 - 11 mL of a mixed solvent of ethanol and water, adjust the pH value of the solution to 7 with sodium hydroxide solution, and add 0.0374 - 0.0376 g of glycine to obtain a mixed solution;

[0010] Place the prepared mixed solution in a single-neck flask, heat to 70 °C, and maintain for 3 - 4 h. Then, centrifuge and wash the product twice with ethanol and water respectively, and vacuum dry at 60 °C for 6 h; obtain a white rod-shaped material, that is, Eu(II)-MOF;

[0011] The synthesized Fe3O4-Ag nanorods were used as the substrate material and drop-coated on a glassy carbon electrode. Then, an antibody, a bovine serum albumin solution, a trenbolone standard, and an antigen label were successively drop-coated to prepare a near-infrared electroluminescent sensor.

[0012] The preparation steps of the Fe3O4-Ag nanorod substrate material are as follows:

[0013] Dissolve 0.004 - 0.006 g of ferric chloride hexahydrate in 20 mL of ethylene glycol, add 1.664 - 1.666 g of polyvinylpyrrolidone as solution a. Dissolve 0.33 - 0.35 g of silver nitrate in 20 mL of ethylene glycol as solution b. Drop solution a into solution b under continuous stirring. Transfer the resulting mixed solution into a reaction kettle lined with polytetrafluoroethylene, heat it to 160 °C, and keep it for 3 h. Wash the obtained product by centrifugation with ethanol three times and vacuum-dry it at 60 °C for 6 h to obtain a bright silver-colored silver nanorod material;

[0014] Dissolve 0.022 - 0.024 g of ferric chloride hexahydrate and 0.011 - 0.013 g of ferrous sulfate heptahydrate in 14 mL of ethylene glycol. Place the resulting solution in a flask, heat it to 50 °C and stir continuously. Dissolve 0.08 - 0.12 g of the prepared silver nanorods in 10 mL of ethylene glycol and drop it into the solution in the flask. Raise the temperature to 65 °C and stir for 20 min. Dissolve 0.08 - 0.12 g of NaOH in 5 mL of ethylene glycol and add it to the solution in the flask. Continue to stir for 20 min. Transfer the mixed solution into a reaction kettle lined with polytetrafluoroethylene, heat it to 200 °C, and keep it for 4 h. Wash the obtained product by centrifugation with ethanol three times and vacuum-dry it at 60 °C for 6 h to obtain black Fe3O4-Ag nanorod material.

[0015] The construction steps of the sensor are as follows:

[0016] Pretreat a glassy carbon electrode with a diameter of 4 mm using polishing powder to obtain a mirror-like surface, and rinse it thoroughly with ultrapure water. Drop 8 μL of a 3 - 5 mg / mL Fe3O4-Ag solution onto the electrode surface and store it at room temperature until dry. Drop 4 μL of a 10 μg / mL trenbolone antibody solution onto the electrode surface and store it in a refrigerator at 4 °C until dry. Drop 2 μL of a 1% (mass fraction) bovine serum albumin solution onto the electrode surface to block the non-specific active sites on the antibody and store it in a refrigerator at 4 °C until dry. Drop 6 μL of different concentrations of trenbolone standards onto the electrode surface and store it in a refrigerator at 4 °C until dry. Drop 6 μL of the antigen label solution onto the electrode surface and store it in a refrigerator at 4 °C until dry, thus realizing the construction of the near-infrared electroluminescent sensor.

[0017] After each step of the sensor construction process is completed by drop coating and dried, the electrode surface is rinsed with ultrapure water to remove the unbound parts.

[0018] The standard solutions of trenbolone at different concentrations are 100 ng / mL, 10 ng / mL, 1 ng / mL, 100 pg / mL, 10 pg / mL, 1 pg / mL, 100 fg / mL, 50 fg / mL, 10 fg / mL, and 5 fg / mL.

[0019] The preparation steps of the antigen label are as follows:

[0020] Disperse 0.5 g of Eu(II)-MOF in 100 mL of toluene, add 1 mL of 3-aminopropyltriethoxysilane, and ultrasonicate for half an hour. The resulting mixed solution is placed in a reaction kettle with a polytetrafluoroethylene liner, heated to 90 °C, and maintained for 24 h. The obtained product is centrifuged and washed 3 times with ultrapure water and then dispersed in 5 mL of PBS buffer. Then, add 200 μL of 1 μg / mL trenbolone antigen, shake at 4 °C for 8 h, and then add 100 μL of 1% bovine serum albumin solution, shake at 4 °C for 2 h to prepare the antigen label.

[0021] The PBS buffer is a mixed solution with a pH of 7.4 prepared from 1 / 15 mol / L disodium hydrogen phosphate solution and 1 / 15 mol / L potassium dihydrogen phosphate solution.

[0022] 2. Application of a rare Eu(II)-MOF prepared by the preparation method as described above as an electrochemiluminescence probe to construct a near-infrared sensor for trace detection of trenbolone, the steps are as follows:

[0023] Use a silver / silver chloride electrode as the reference electrode, a platinum wire electrode as the counter electrode, and the constructed sensor as the working electrode to establish a three-electrode system. Connect the above three electrodes in the dark box of a chemiluminescence detector, connect the electrochemical workstation and the chemiluminescence detector together. Set the high voltage of the photomultiplier tube to 800 V, the scanning voltage to 0 - 1.3 V, and the scanning rate to 0.1 V / s; use a 55 mmol / L tripropylamine solution as the base solution, and use the three-electrode system to detect the electrochemiluminescence signal intensity generated under standard solutions of trenbolone at different concentrations; draw a working curve according to the linear relationship between the obtained electrochemiluminescence signal intensity value and the logarithm of the trenbolone standard solution concentration; the tripropylamine solution has a pH of 7.4, and the preparation solvent is PBS buffer;

[0024] The above-mentioned construction of an efficient near-infrared sensor using a rare Eu(II)-MOF as an electrochemiluminescence probe for the trace detection of trenbolone has a detection limit of 3.7 fg / mL and a detection range of 5 fg / mL - 100 ng / mL, indicating the efficient and sensitive detection ability of this electrochemiluminescence sensor; after continuous operation for half an hour, no obvious change in the ECL signal was found, indicating that the sensor has good stability.

[0025] Advantageous technical effects of the present invention:

[0026] 1. A rare Eu(II)-MOF material prepared by the present invention is generated by a solvothermal method under the protection of no reducing gas. The preparation process has a simple process, is easy to control, has high operation safety, high product preparation efficiency, and is easy to industrialize.

[0027] 2. A rare Eu(II)-MOF prepared by the present invention is used as an electrochemiluminescence probe to construct a near-infrared sensor, which is a competitive electrochemiluminescence sensor constructed by combining Eu(II)-MOF with an antigen as an antigen marker. The strong electrochemiluminescence performance of Eu(II)-MOF in the near-infrared region enables the constructed sensor to work stably and efficiently in harsh environments such as high temperature, high pressure, and heavy pollution, with high practical value. Specific embodiments

[0028] The present invention will be further described below in conjunction with embodiments, but the protection scope of the present invention is not limited to the embodiments. Any changes made by professionals in the field to the technical solutions of the present invention shall fall within the protection scope of the present invention.

[0029] Example 1 Synthesis of a rare Eu(II)-MOF and preparation method of constructing a near-infrared sensor using it as an electrochemiluminescence probe

[0030] Dissolve 0.257 g of europium chloride hexahydrate and 0.197 g of 1,10-phenanthroline in a mixed solvent of 9 mL of ethanol and water, adjust the pH value of the solution to 7 with sodium hydroxide solution, and add 0.0374 g of glycine to obtain a mixed solution;

[0031] Place the prepared mixed solution in a single-neck flask, heat it to 70 °C, and maintain it for 3 h. Then, centrifuge and wash the product twice with ethanol and water respectively, and vacuum dry it at 60 °C for 6 h to obtain a white rod-shaped material, namely Eu(II)-MOF;

[0032] Drop the synthesized Fe3O4-Ag nanorods as the substrate material onto a glassy carbon electrode, and then sequentially drop an antibody, a bovine serum albumin solution, a target analyte standard, and an antigen marker to obtain a near-infrared electrochemiluminescence sensor.

[0033] The preparation steps of the Fe3O4-Ag nanorod substrate material are as follows:

[0034] Dissolve 0.004 g of ferric chloride hexahydrate in 20 mL of ethylene glycol, add 1.664 g of polyvinylpyrrolidone to obtain solution a, dissolve 0.33 g of silver nitrate in 20 mL of ethylene glycol to obtain solution b, drop solution a into solution b under continuous stirring, transfer the obtained mixed solution into a reaction kettle lined with polytetrafluoroethylene, heat to 160 °C, and keep for 3 h. Wash the obtained product 3 times by centrifugation with ethanol and vacuum dry at 60 °C for 6 h to obtain bright silver-colored silver nanorod material;

[0035] Dissolve 0.022 g of ferric chloride hexahydrate and 0.011 g of ferrous sulfate heptahydrate in 14 mL of ethylene glycol, place the obtained solution in a flask, heat to 50 °C and stir continuously. Dissolve 0.08 g of the prepared silver nanorods in 10 mL of ethylene glycol, and drop it into the solution in the flask. Raise the temperature to 65 °C and stir for 20 min. Dissolve 0.08 g of NaOH in 5 mL of ethylene glycol and add it to the solution in the flask, and continue to stir for 20 min. Transfer the mixed solution into a reaction kettle lined with polytetrafluoroethylene, heat to 200 °C, and keep for 4 h. Wash the obtained product 3 times by centrifugation with ethanol and vacuum dry at 60 °C for 6 h to obtain black Fe3O4-Ag nanorod material.

[0036] The construction steps of the sensor are as follows:

[0037] Use polishing powder to pretreat a glassy carbon electrode with a diameter of 4 mm to obtain a mirror-like surface, and rinse it thoroughly with ultrapure water; drop 8 μL of 3 mg / mL Fe3O4-Ag solution onto the electrode surface and store it at room temperature until dry; drop 4 μL of 10 μg / mL trenbolone antibody solution onto the electrode surface and store it in a refrigerator at 4 °C until dry; drop 2 μL of 1% (mass fraction) bovine serum albumin solution onto the electrode surface to block non-specific active sites on the antibody and store it in a refrigerator at 4 °C until dry; drop 6 μL of different concentrations of trenbolone standard onto the electrode surface and store it in a refrigerator at 4 °C until dry; drop 6 μL of antigen-labeled solution onto the electrode surface and store it in a refrigerator at 4 °C until dry, thus realizing the construction of a near-infrared electrochemiluminescence sensor.

[0038] After each step of the sensor construction process is dropped and dried, the electrode surface is rinsed with ultrapure water to remove the unbound part.

[0039] The standards of trenbolone at different concentrations are 100 ng / mL, 10 ng / mL, 1 ng / mL, 100 pg / mL, 10 pg / mL, 1 pg / mL, 100 fg / mL, 50 fg / mL, 10 fg / mL, and 5 fg / mL.

[0040] The preparation steps of the antigen marker are as follows:

[0041] Disperse 0.5 g of Eu(II)-MOF in 100 mL of toluene, add 1 mL of 3-aminopropyltriethoxysilane, and then ultrasonicate for half an hour. Place the obtained mixed solution in a reaction kettle with a polytetrafluoroethylene liner, heat it to 90 °C, and keep it for 24 h. The obtained product is centrifuged and washed 3 times with ultrapure water and then dispersed in 5 mL of PBS buffer. Then, add 200 μL of 1 μg / mL trenbolone antigen, shake it at 4 °C for 8 h, and then add 100 μL of 1% bovine serum albumin solution, shake it at 4 °C for 2 h to obtain the antigen marker.

[0042] The PBS buffer is a mixed solution with a pH of 7.4 prepared from 1 / 15 mol / L disodium hydrogen phosphate solution and 1 / 15 mol / L potassium dihydrogen phosphate solution.

[0043] Example 2 Preparation method of synthesis of a rare Eu(II)-MOF and construction of a near-infrared sensor as an electroluminescent probe

[0044] Dissolve 0.258 g of europium chloride hexahydrate and 0.198 g of 1,10-phenanthroline in 10 mL of a mixed solvent of ethanol and water, adjust the pH value of the solution to 7 with sodium hydroxide solution, and add 0.0375 g of glycine to obtain a mixed solution;

[0045] Place the prepared mixed solution in a single-neck flask, heat it to 70 °C, and keep it for 3.5 h. Then, centrifuge and wash the product twice with ethanol and water respectively, and dry it in vacuum at 60 °C for 6 h to obtain a white rod-shaped material, namely Eu(II)-MOF;

[0046] Drop the synthesized Fe3O4-Ag nanorods as the substrate material onto a glassy carbon electrode, and then sequentially dropwise add an antibody, a bovine serum albumin solution, a target analyte standard, and an antigen marker to prepare a near-infrared electroluminescent sensor.

[0047] The preparation steps of the Fe3O4-Ag nanorod substrate material are as follows:

[0048] Dissolve 0.005 g of ferric chloride hexahydrate in 20 mL of ethylene glycol, add 1.665 g of polyvinylpyrrolidone to obtain solution a. Dissolve 0.34 g of silver nitrate in 20 mL of ethylene glycol to obtain solution b. Drop solution a into solution b under continuous stirring. Transfer the obtained mixed solution into a reaction kettle lined with polytetrafluoroethylene, heat it to 160 °C, and keep it for 3 h. Wash the obtained product by centrifugation with ethanol three times, and dry it in vacuum at 60 °C for 6 h to obtain bright silver-colored silver nanorod material;

[0049] Dissolve 0.023 g of ferric chloride hexahydrate and 0.012 g of ferrous sulfate heptahydrate in 14 mL of ethylene glycol. Place the obtained solution in a flask, heat it to 50 °C and stir continuously. Dissolve 0.1 g of the prepared silver nanorods in 10 mL of ethylene glycol, and drop it into the solution in the flask. Raise the temperature to 65 °C and stir for 20 min. Dissolve 0.1 g of NaOH in 5 mL of ethylene glycol and add it to the solution in the flask, and continue to stir for 20 min. Transfer the mixed solution into a reaction kettle lined with polytetrafluoroethylene, heat it to 200 °C, and keep it for 4 h. Wash the obtained product by centrifugation with ethanol three times, and dry it in vacuum at 60 °C for 6 h to obtain black Fe3O4-Ag nanorod material.

[0050] The steps for constructing the sensor are as follows:

[0051] Pretreat a glassy carbon electrode with a diameter of 4 mm using polishing powder to obtain a mirror-like surface, and rinse it thoroughly with ultrapure water. Drop 8 μL of a 4 mg / mL Fe3O4-Ag solution onto the electrode surface and store it at room temperature until dry. Drop 4 μL of a 10 μg / mL trenbolone antibody solution onto the electrode surface and store it in a refrigerator at 4 °C until dry. Drop 2 μL of a 1% (mass fraction) bovine serum albumin solution onto the electrode surface to block the non-specific active sites on the antibody, and store it in a refrigerator at 4 °C until dry. Drop 6 μL of different concentrations of trenbolone standards onto the electrode surface and store it in a refrigerator at 4 °C until dry. Drop 6 μL of an antigen marker solution onto the electrode surface and store it in a refrigerator at 4 °C until dry, thus constructing a near-infrared electrochemiluminescence sensor.

[0052] After each step of the sensor construction process is dropped and dried, rinse the electrode surface with ultrapure water to remove the unbound part.

[0053] The different concentrations of trenbolone standards are characterized in that each concentration is the same as in Example 1.

[0054] The antigen marker is characterized in that the preparation steps are the same as in Example 1.

[0055] The PBS buffer solution is characterized in that the preparation method is the same as in Example 1.

[0056] Example 3 Synthesis of a Rare Eu(II)-MOF and Preparation Method of a Near-Infrared Sensor by Constructing an Electroluminescent Probe

[0057] Dissolve 0.259 g of europium chloride hexahydrate and 0.199 g of 1,10-phenanthroline in a mixed solvent of 11 mL of ethanol and water. Adjust the pH value of the solution to 7 with sodium hydroxide solution, and add 0.0376 g of glycine to obtain a mixed solution;

[0058] Place the prepared mixed solution in a single-neck flask, heat it to 70 °C, and keep it for 4 h. Then, centrifuge and wash the product twice with ethanol and water respectively, and vacuum dry it at 60 °C for 6 h to obtain a white rod-shaped material, namely Eu(II)-MOF;

[0059] Drop the synthesized Fe3O4-Ag nanorods as the substrate material onto a glassy carbon electrode, and then sequentially dropwise add an antibody, a bovine serum albumin solution, a target analyte standard, and an antigen label; to obtain a near-infrared electroluminescent sensor.

[0060] The preparation steps of the Fe3O4-Ag nanorod substrate material are as follows:

[0061] Dissolve 0.006 g of ferric chloride hexahydrate in 20 mL of ethylene glycol, add 1.666 g of polyvinylpyrrolidone as solution a, dissolve 0.35 g of silver nitrate in 20 mL of ethylene glycol as solution b, drop solution a into solution b under continuous stirring, transfer the obtained mixed solution into a reaction kettle lined with polytetrafluoroethylene, heat it to 160 °C, and keep it for 3 h. Wash the obtained product by centrifugation with ethanol 3 times, and vacuum dry it at 60 °C for 6 h to obtain a bright silver-colored silver nanorod material;

[0062] Dissolve 0.024 g of ferric chloride hexahydrate and 0.013 g of ferrous sulfate heptahydrate in 14 mL of ethylene glycol. Place the obtained solution in a flask, heat it to 50 °C and stir continuously. Dissolve 0.12 g of the prepared silver nanorods in 10 mL of ethylene glycol and drop it into the solution in the flask. Raise the temperature to 65 °C and stir for 20 min. Dissolve 0.12 g of NaOH in 5 mL of ethylene glycol and add it to the solution in the flask, and continue to stir for 20 min. Transfer the mixed solution into a reaction kettle lined with polytetrafluoroethylene, heat it to 200 °C, and keep it for 4 h. Wash the obtained product by centrifugation with ethanol 3 times, and vacuum dry it at 60 °C for 6 h to obtain a black Fe3O4-Ag nanorod material.

[0063] The construction steps of the sensor are as follows:

[0064] A glassy carbon electrode with a diameter of 4 mm was pretreated with polishing powder to obtain a mirror-like surface, which was then rinsed with ultrapure water; 8 µL of 5 mg / mL Fe3O4-Ag solution was drop-coated on the electrode surface and stored at room temperature until dry; 4 µL of 10 µg / mL trenbolone antibody solution was drop-coated on the electrode surface and stored in a 4 ℃ refrigerator until dry; 2 µL of 1% bovine serum albumin solution was drop-coated on the electrode surface to block nonspecific active sites on the antibody and stored in a 4 ℃ refrigerator until dry; 6 µL of trenbolone standards of different concentrations were drop-coated on the electrode surface and stored in a 4 ℃ refrigerator until dry; 6 µL of antigen marker solution was drop-coated on the electrode surface and stored in a 4 ℃ refrigerator until dry, thus realizing the construction of a near-infrared electroluminescent sensor.

[0065] In each step of the sensor construction process, after drop coating and drying, the electrode surface is rinsed with ultrapure water to remove the unbound parts.

[0066] The different concentrations of trenbolone standard products are characterized in that the concentrations are the same as those in Example 1.

[0067] The antigen marker is characterized in that the preparation steps are the same as those in Example 1.

[0068] The PBS buffer is characterized in that the preparation method is the same as that in Example 1.

[0069] Example 4 Application of a rare Eu(II)-MOF as an electroluminescent probe to construct a near-infrared sensor for trace detection of trenbolone

[0070] A three-electrode system was established by using a silver / silver chloride electrode as a reference electrode, a platinum wire electrode as a counter electrode, and the constructed sensor as a working electrode. The three electrodes were connected to a dark box of a chemiluminescence detector, and an electrochemical workstation and a chemiluminescence detector were connected together. The photomultiplier tube high voltage was set to 800 V, the scanning voltage was set to 0-1.3 V, and the scanning rate was set to 0.1 V / s. A 55 mmol / L tripropylamine solution was used as a base solution, and the electrochemiluminescence signal intensity generated under different concentrations of trenbolone standard was detected by using the three-electrode system. A working curve was drawn according to the linear relationship between the obtained electrochemiluminescence signal intensity value and the logarithm of the trenbolone standard concentration. The tripropylamine solution had a pH of 7.4 and was prepared using a PBS buffer solution.

[0071] The Eu(II)-MOF prepared in Example 1, Example 2 or Example 3 is used as an electrochemiluminescence probe to construct a highly efficient near-infrared sensor for the trace detection of trenbolone. The detection limit is 3.7 fg / mL, and the detection range is 5 fg / mL - 100 ng / mL, indicating the highly efficient and sensitive detection ability of this electrochemiluminescence sensor. After continuous working for half an hour, no obvious change in the ECL signal is found, indicating that this sensor has good stability.

Claims

1. A preparation method of a near-infrared electroluminescent sensor constructed with a rare Eu(II)-MOF as a probe, characterized in that, The steps are as follows: Dissolve 0.257 - 0.259 g of europium(III) chloride hexahydrate and 0.197 - 0.199 g of 1,10 - phenanthroline in a mixed solvent of 9 - 11 mL of ethanol and water. Adjust the pH value of the solution to 7 with sodium hydroxide solution, and add 0.0374 - 0.0376 g of glycine to obtain a mixed solution. Place the prepared mixed solution in a single - neck flask, heat it to 70 °C, and keep it for 3 - 4 h. Then, centrifuge and wash the product twice with ethanol and water respectively, and vacuum - dry it at 60 °C for 6 h to obtain a white rod - shaped material, namely Eu(II) - MOF. Drop - coat the synthesized Fe3O4 - Ag nanorods as the substrate material onto a glassy carbon electrode, dry it, and then successively drop - add trenbolone antibody, bovine serum albumin solution, trenbolone standard, and antigen label. After each step of drop - coating and drying, rinse the electrode surface with ultrapure water to remove the unbound part; a near - infrared electroluminescence sensor is prepared. The antigen label is formed by binding an antigen with the ECL probe Eu(II) - MOF, and the steps are as follows: Disperse 0.5 g of Eu(II) - MOF in 100 mL of toluene, add 1 mL of 3 - aminopropyltriethoxysilane, and ultrasonicate for half an hour. Place the obtained mixed solution in a reaction kettle with a polytetrafluoroethylene inner lining, heat it to 90 °C, and keep it for 24 h. Centrifuge and wash the obtained product 3 times with ultrapure water and then disperse it in 5 mL of PBS buffer. Then add 200 μL of 1 μg / mL trenbolone antigen, shake it at 4 °C for 8 h, and then add 100 μL of 1% bovine serum albumin solution and shake it at 4 °C for 2 h to obtain the antigen label. The Fe3O4 - Ag nanorods are prepared by the following method: Dissolve ferric chloride hexahydrate and ferrous sulfate heptahydrate in ethylene glycol. Place the obtained solution in a flask, heat it to 50 °C and stir continuously. Dissolve the silver nanorod material in ethylene glycol and drop it into the solution in the flask. Raise the temperature to 65 °C and stir for reaction. Dissolve NaOH in ethylene glycol and add it to the solution in the flask, and continue to stir for reaction to obtain a mixed solution. Transfer the mixed solution to a reaction kettle with a polytetrafluoroethylene inner lining, heat it to 200 °C, and keep it for 4 h. Centrifuge, wash, and dry the obtained product.

2. The preparation method of the near-infrared electroluminescent sensor according to claim 1, wherein, The preparation steps of the Fe3O4 - Ag nanorod substrate material are as follows: Dissolve 0.004 - 0.006 g of ferric chloride hexahydrate in 20 mL of ethylene glycol, add 1.664 - 1.666 g of polyvinylpyrrolidone as solution a. Dissolve 0.33 - 0.35 g of silver nitrate in 20 mL of ethylene glycol as solution b. Drop solution a into solution b with continuous stirring. Transfer the obtained mixed solution to a reaction kettle with a polytetrafluoroethylene inner lining, heat it to 160 °C, and keep it for 3 h. Centrifuge and wash the obtained product 3 times with ethanol and vacuum - dry it at 60 °C for 6 h to obtain a bright silver - colored silver nanorod material. Dissolve 0.022 - 0.024 g of ferric chloride hexahydrate and 0.011 - 0.013 g of ferrous sulfate heptahydrate in 14 mL of ethylene glycol. Place the resulting solution in a flask, heat it to 50 °C and stir continuously. Dissolve 0.08 - 0.12 g of the prepared silver nanorods in 10 mL of ethylene glycol, and add it dropwise to the solution in the flask. Raise the temperature to 65 °C and stir for 20 min. Dissolve 0.08 - 0.12 g of NaOH in 5 mL of ethylene glycol and add it to the solution in the flask. Continue to stir for 20 min. Transfer the mixed solution to a reaction kettle lined with polytetrafluoroethylene, heat it to 200 °C, and keep it for 4 h. Wash the obtained product by centrifugation with ethanol three times, and dry it in vacuum at 60 °C for 6 h to obtain the black Fe3O4-Ag nanorod material.

3. The preparation method of the near-infrared electroluminescent sensor according to claim 1, characterized in that, The construction of the near-infrared electroluminescent sensor is carried out as follows: Pretreat a glassy carbon electrode with a diameter of 4 mm using polishing powder to obtain a mirror-like surface, and rinse it thoroughly with ultrapure water. Drop 8 μL of a 3 - 5 mg / mL Fe3O4-Ag solution onto the electrode surface and store it at room temperature until dry. Drop 4 μL of a 10 μg / mL trenbolone antibody solution onto the electrode surface and store it in a refrigerator at 4 °C until dry. Drop 2 μL of a 1% (mass fraction) bovine serum albumin solution onto the electrode surface to block the non-specific active sites on the antibody, and store it in a refrigerator at 4 °C until dry. Drop 6 μL of trenbolone standards with different concentrations onto the electrode surface and store it in a refrigerator at 4 °C until dry. Drop 6 μL of the antigen-labeled substance solution onto the electrode surface and store it in a refrigerator at 4 °C until dry.

4. The preparation method of the near-infrared electroluminescent sensor according to claim 3, characterized in that, The different concentrations of trenbolone standards are 100 ng / mL, 10 ng / mL, 1 ng / mL, 100 pg / mL, 10 pg / mL, 1 pg / mL, 100 fg / mL, 50 fg / mL, 10 fg / mL, 5 fg / mL.

5. The preparation method of the near-infrared electroluminescent sensor according to claim 1, characterized in that, The PBS buffer solution is a mixed solution with a pH of 7.4 prepared from a 1 / 15 mol / L disodium hydrogen phosphate solution and a 1 / 15 mol / L potassium dihydrogen phosphate solution.

6. Application of the near-infrared electroluminescent sensor prepared by the preparation method according to claim 1 in the trace detection of trenbolone in the environment.