Micro-nano electrochemical electrode for in-situ detection of nitrite and preparation method of micro-nano electrochemical electrode

Abstract

The invention discloses a micro-nano electrochemical electrode for in-situ detection of nitrite and a preparation method of the micro-nano electrochemical electrode, and the micro-nano electrochemical electrode is prepared by the following steps of: loading a tungsten oxide homojunction material with a nano particle size onto carbon cloth subjected to hydrophilic treatment through an in-situ growth method on the basis of hydrothermal reaction, alcohol thermal reaction, annealing step-by-step synthesis and the like; a WO3 / WO3-x nano array is constructed on the surface of carbon cloth, then a Nafion solution is used for loading a nitrite ion carrier on the carbon cloth to obtain an electrode WO3 / WO3-x-3NN-CC, and then a platinum electrode is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, and the electrode WO3 / WO3-x-3NN-CC is used as a working electrode to form a three-electrode system which can be used for detecting nitrite ions. The defects of carbon cloth in the application of electrochemical detection electrodes and sensors are overcome, and the prepared electrode is low in nitrite ion detection limit and high in sensitivity. Meanwhile, when NO2 <-> is detected in solutions of urea, glucose, NO3 <->, CO3 < 2->, Fe < 3 + >, Co < 2 + > and the like with the concentration 20 times that of nitrite ions, high anti-interference capability is shown, and the application prospect is wide.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical sensing, and particularly relates to a micro-nano electrochemical electrode for in-situ detection of nitrite and a preparation method thereof. Background Art

[0002] Nitrite is widely present in the environment where humans live and is one of the most common nitrogen-containing compounds in nature. It is often used commercially as a food additive, corrosion inhibitor, preservative and fertilizer. Excessive nitrite will form carcinogens - nitrosamines, which are harmful to the human living environment and may cause serious health problems, including methemoglobinemia, blue baby syndrome, brain damage, gastric cancer, etc. In order to avoid the above adverse consequences, it has become an urgent need to strictly monitor the toxic nitrite ions in the environment to control their hazards.

[0003] At present, the commonly used methods for detecting nitrite include spectrophotometry, high performance liquid chromatography, capillary electrophoresis, electrochemical detection, etc. Electrochemical detection has attracted wide attention due to its advantages of fast response, high sensitivity, high selectivity, simple operation and high preparation diversity. Carbon cloth (CC) has the advantages of low cost, good thermal and chemical stability, low thermal expansion coefficient and easy availability of raw materials. However, commercial carbon cloth has strong hydrophobicity, low specific surface area and weak electrochemical activity, which limits its application in electrochemical sensing. Therefore, it is necessary to modify and modify carbon cloth so that it can be more widely used in electrochemical detection. Summary of the invention

[0004] In view of the above-mentioned deficiencies, the present invention discloses a micro-nano electrochemical electrode for in-situ detection of nitrite and a preparation method thereof, which solves the deficiencies existing in the application of carbon cloth in electrochemical detection electrodes and sensors, and prepares a nitrite detection electrode with excellent performance based on carbon cloth.

[0005] The present invention is achieved by adopting the following technical solutions:

[0006] A micro-nano electrochemical electrode for in-situ detection of nitrite, comprising a carbon cloth, on the surface of which a WO3 / WO 3-x Nano-array layer, the WO3 / WO 3-x The nanoarray layer is loaded with nitrite ion carriers.

[0007] Furthermore, the molecular formula of the nitrite ion carrier is C 36 H 46 N2CoO2 and its chemical structure is:

[0008]

[0009] The preparation method of the micro-nano electrochemical electrode for in-situ detection of nitrite comprises the following steps:

[0010] S1. Hydrophilic treatment of carbon cloth: ultrasonically clean the carbon cloth (CC) in acetone, ethanol and deionized water for 10 minutes in sequence, then take the carbon cloth to dry, then immerse the carbon cloth in a mixed acid solution for 12 hours, take it out, wash it with deionized water and dry it for later use; the mixed acid solution is obtained by mixing concentrated sulfuric acid and concentrated nitric acid;

[0011] S2, electrode WO3 / WO 3-x Synthesis of -CC: dissolve sodium tungstate dihydrate and potassium oxalate monohydrate in distilled water and adjust the pH to 1.4-1.6 with dilute hydrochloric acid and stir for 2 hours to obtain a precursor aqueous solution; dissolve tungsten hexachloride in ethanol to obtain a tungsten hexachloride ethanol solution; place the carbon cloth treated in step S1 in a reactor, then pour the precursor aqueous solution into it, and then seal the reactor to react at 170-190°C for 11-13 hours, then take out the carbon cloth, rinse it with ethanol and deionized water in turn, dry it at 55-60°C, and then anneal it at 540-560°C for 2 hours, cool it to room temperature, place the carbon cloth in the tungsten hexachloride ethanol solution, and then react at 170-190°C for 11-13 hours, then take out the carbon cloth, rinse it with ethanol and deionized water in turn, and dry it at room temperature to obtain the electrode WO3 / WO 3-x —CC;

[0012] S3, electrode WO3 / WO 3-x Preparation of —3NN—CC: Dissolve the nitrite ion carrier in N,N-dimethylformamide (DMF), then add an equal volume of Nafion solution and mix evenly to obtain a mixed solution, and drop the mixed solution onto the electrode WO3 / WO obtained in step S2. 3-x —CC, and then dried at room temperature for 24 h to obtain the electrode WO3 / WO 3-x —3NN—CC, namely the micro-nano electrochemical electrode for in-situ detection of nitrite.

[0013] Furthermore, in step S1, the frequency of the ultrasonic wave used in the ultrasonic cleaning is 25KHz; the mixed acid solution is obtained by mixing concentrated sulfuric acid and concentrated nitric acid, and the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1. After the carbon cloth is soaked in acetone, ethanol and deionized water for ultrasonic treatment to remove impurities on the surface of the carbon cloth, the carbon cloth is placed in a mixed acid solution prepared by concentrated sulfuric acid and concentrated nitric acid in proportion for treatment, and the carbon cloth is hydrophilized and modified, which is helpful for the subsequent loading of tungsten oxide.

[0014] Furthermore, in step S2, each 1L of the precursor aqueous solution contains 0.03-0.05mol of sodium tungstate dihydrate and 0.017-0.019mol of potassium oxalate monohydrate; and each 1L of the tungsten hexachloride ethanol solution contains 0.03-0.05mol of tungsten hexachloride.

[0015] Further, in step S3, the mixed solution is added dropwise to the electrode WO3 / WO obtained in step S2. 3-x —CC, and then dried at room temperature for 24 hours, and then repeatedly dripped the mixed solution onto the electrode WO3 / WO 3-x —CC 2 to 3 times, and after each addition, place it at room temperature to dry for 24 hours.

[0016] Furthermore, the preparation method of the nitrite ion carrier comprises the following steps:

[0017] S41, dissolving o-phenylenediamine and 3,5-di-tert-butyl salicylaldehyde in methanol to obtain reaction solution A, wherein each 1 L of reaction solution A contains 0.15-0.17 mol of o-phenylenediamine and 0.31-0.33 mol of 3,5-di-tert-butyl salicylaldehyde, then adding formic acid to the reaction solution A, mixing, stirring and reacting at 70-90° C. for 12-13 h, then filtering under reduced pressure to obtain filter residue I, washing the filter residue I with ethanol and drying to obtain intermediate I;

[0018] S42. The intermediate I obtained in step S41 is dissolved in chloroform to obtain a reaction solution B, wherein each 1 L of the reaction solution B contains 0.06-0.08 mol of the intermediate I; cobalt acetate tetrahydrate is dissolved in ethanol to obtain a reaction solution C, wherein each 1 L of the reaction solution C contains 0.12-0.16 mol of cobalt acetate tetrahydrate; the reaction solution C is slowly added dropwise to the reaction solution B, and after the addition is completed, the mixture is stirred at room temperature for 2-3 h, and then filtered under reduced pressure to obtain a filter residue II, and the filter residue II is rinsed with ethanol and dried to obtain a nitrite ion carrier.

[0019] Furthermore, in step S41, the volume ratio of the reaction solution A and formic acid is (4000-6000):(4-6); in step S42, the molar ratio of the intermediate I and cobalt acetate tetrahydrate is 1:1.

[0020] The application of the above-mentioned micro-nano electrochemical electrode for in-situ detection of nitrite is to detect nitrite in water. Specifically, a saturated calomel electrode is used as a reference electrode, a platinum electrode is used as a counter electrode, and the micro-nano electrochemical electrode for in-situ detection of nitrite is used as a working electrode to form a three-electrode electrochemical detection system. A phosphate buffer solution (PBS, pH=6.5) with a concentration of 0.1M is used as a supporting electrolyte. Then, a chronoamperometry (it) method is used and the external constant voltage is adjusted to 0.795V. Then, the water sample to be tested is added to the supporting electrolyte for detection.

[0021] Compared with the prior art, this technical solution has the following beneficial effects:

[0022] 1. Based on the hydrothermal reaction, alcohol thermal reaction and annealing step-by-step synthesis strategy, the present invention constructs WO3 / WO composed of micro-nano particles on the surface of carbon cloth. 3-x Nanoarray, and then the nitrite ion carrier is loaded onto the carbon cloth through Nafion solution, and finally the electrode WO3 / WO for detecting nitrite is prepared. 3-x -3NN-CC, the electrochemical active area of ​​this electrode is large, the electron transfer rate is accelerated, and it has a significant catalytic effect on the oxidation reaction of nitrite ions on the electrode surface.

[0023] 2. The micro-nano electrochemical electrode for in-situ detection of nitrite prepared by the present invention has the advantages of wide linear range, high sensitivity, low detection limit, short response time, etc., and is effective for urea, glucose, NO3 - 、CO3 2- , Fe 3+ 、Co 2+ There is no response to the equal current signal and it has good anti-interference ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the synthetic route of the nitrite ion carrier described in Example 2.

[0025] Figure 2 This is a scanning electron microscope image of the carbon cloth described in Example 2 when no tungsten oxide is loaded.

[0026] Figure 3 The carbon cloth loaded with WO3 / WO in Example 2 3-x Scanning electron micrograph after .

[0027] Figure 4 The carbon cloth loaded with WO3 / WO in Example 2 3-x The X-ray energy spectrum element distribution diagram after the experiment, where A is the corresponding scanning electron microscope image, C is the carbon element image, W is the tungsten element image, and O is the oxygen element image.

[0028] Figure 5 It is a relationship diagram between the sodium nitrite concentration (μM level) detected in Example 6 and the current response value.

[0029] Figure 6 It is a linear relationship diagram between the sodium nitrite concentration (μM level) detected in Example 6 and the current response value.

[0030] Figure 7 It is a graph showing the relationship between the sodium nitrite concentration (mM level) detected in Example 6 and the current response value.

[0031] Figure 8 It is a linear relationship diagram between the sodium nitrite concentration (mM level) detected in Example 6 and the current response value.

[0032] Fig. 9 This is a data graph of the electrode anti-interference test described in Example 7. DETAILED DESCRIPTION

[0033] The present invention is further described by the following examples, but is not intended to be limiting of the present invention. Specific experimental conditions and methods not specified in the following examples are conventional methods commonly known to those skilled in the art.

[0034] Example 1: A micro-nano electrochemical electrode for in-situ detection of nitrite, comprising a carbon cloth having a WO3 / WO 3-x Nano-array layer, the WO3 / WO 3-x The nanoarray layer is loaded with a nitrite ion carrier; the molecular formula of the nitrite ion carrier is C 36 H 46 N2CoO2 and its chemical structure is:

[0035]

[0036] Example 2: A method for preparing a micro-nano electrochemical electrode for in-situ detection of nitrite (see Figure 1 ), which comprises the following steps:

[0037] S1. Hydrophilic treatment of carbon cloth: ultrasonically clean the carbon cloth (CC) in acetone, ethanol and deionized water for 10 minutes in sequence, then take the carbon cloth to dry, then immerse the carbon cloth in a mixed acid solution for 12 hours, take it out, and then clean it with deionized water and dry it for use; the mixed acid solution is obtained by mixing concentrated sulfuric acid and concentrated nitric acid; the frequency of the ultrasonic wave used in the ultrasonic cleaning is 25KHz; the mixed acid solution is obtained by mixing concentrated sulfuric acid and concentrated nitric acid, and the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1;

[0038] S2, electrode WO3 / WO 3-xSynthesis of -CC: Sodium tungstate dihydrate and potassium oxalate monohydrate are dissolved in distilled water and the pH is adjusted to 1.5 with 1M dilute hydrochloric acid and stirred for 2 hours to obtain a precursor aqueous solution; tungsten hexachloride is dissolved in ethanol to obtain a tungsten hexachloride ethanol solution; the carbon cloth treated in step S1 is placed in a reactor, and then the precursor aqueous solution is poured in, and then the reactor is sealed and reacted at 180°C for 12 hours, then the carbon cloth is taken out, rinsed with ethanol and deionized water in turn, and then dried at 58°C, and then annealed at 550°C for 2 hours, cooled to room temperature, and then the carbon cloth is placed in the tungsten hexachloride ethanol solution, and then reacted at 180°C for 12 hours, then the carbon cloth is taken out, rinsed with ethanol and deionized water in turn, and then dried at room temperature to obtain the electrode WO3 / WO 3-x —CC (see Figures 2 to 4 ); each 1L of the precursor aqueous solution contains 0.04mol of sodium tungstate dihydrate and 0.018mol of potassium oxalate monohydrate; each 1L of tungsten hexachloride ethanol solution contains 0.04mol of tungsten hexachloride; the reactor uses a stainless steel high-pressure reactor lined with polytetrafluoroethylene;

[0039] S3, electrode WO3 / WO 3-x Preparation of —3NN—CC: Dissolve the nitrite ion carrier in N,N-dimethylformamide (DMF), then add an equal volume of Nafion solution and mix evenly to obtain a mixed solution, and drop the mixed solution onto the electrode WO3 / WO obtained in step S2. 3-x —CC, and then dried at room temperature for 24 hours, and then repeatedly dripped the mixed solution onto the electrode WO3 / WO 3-x —CC was used twice to obtain the electrode for detecting nitrite (electrode WO3 / WO 3-x —3NN—CC), and after each addition, place at room temperature to dry for 24 hours.

[0040] The preparation method of the nitrite ion carrier described in this embodiment comprises the following steps:

[0041] S41, dissolving o-phenylenediamine and 3,5-di-tert-butyl salicylaldehyde in methanol to obtain a reaction solution A, wherein each 1 L of the reaction solution A contains 0.16 mol of o-phenylenediamine and 0.32 mol of 3,5-di-tert-butyl salicylaldehyde, then adding formic acid to the reaction solution A, mixing, stirring and reacting at 80° C. for 12 h, then filtering under reduced pressure to obtain a filter residue I, washing the filter residue I with ethanol, and drying to obtain an intermediate I; the volume ratio of the reaction solution A to formic acid is 5000:5;

[0042] S42. The intermediate I obtained in step S41 is dissolved in chloroform to obtain a reaction solution B, wherein each 1 L of the reaction solution B contains 0.07 mol of the intermediate I; cobalt acetate tetrahydrate is dissolved in ethanol to obtain a reaction solution C, wherein each 1 L of the reaction solution C contains 0.14 mol of cobalt acetate tetrahydrate; the reaction solution C is slowly added dropwise to the reaction solution B, and after the addition is completed, the mixture is stirred at room temperature for 2 h, and then filtered under reduced pressure to obtain a filter residue II, and the filter residue II is rinsed with ethanol and then dried to obtain a nitrite ion carrier; the molar ratio of the intermediate I to cobalt acetate tetrahydrate is 1:1.

[0043] Example 3: A method for preparing a micro-nano electrochemical electrode for in-situ detection of nitrite, comprising the following steps:

[0044] S1. Hydrophilic treatment of carbon cloth: ultrasonically clean the carbon cloth (CC) in acetone, ethanol and deionized water for 10 minutes in sequence, then take the carbon cloth to dry, then immerse the carbon cloth in a mixed acid solution for 12 hours, take it out, and then clean it with deionized water and dry it for use; the mixed acid solution is obtained by mixing concentrated sulfuric acid and concentrated nitric acid; the frequency of the ultrasonic wave used in the ultrasonic cleaning is 25KHz; the mixed acid solution is obtained by mixing concentrated sulfuric acid and concentrated nitric acid, and the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1;

[0045] S2, electrode WO3 / WO 3-x Synthesis of -CC: Sodium tungstate dihydrate and potassium oxalate monohydrate are dissolved in distilled water and the pH is adjusted to 1.4 with 2M dilute hydrochloric acid and stirred for 2 hours to obtain a precursor aqueous solution; tungsten hexachloride is dissolved in ethanol to obtain a tungsten hexachloride ethanol solution; the carbon cloth treated in step S1 is placed in a reactor, and then the precursor aqueous solution is poured in, and then the reactor is sealed and reacted at 170°C for 13 hours, then the carbon cloth is taken out, rinsed with ethanol and deionized water in turn, and then dried at 55°C, and then annealed at 540°C for 2 hours, cooled to room temperature, and then the carbon cloth is placed in the tungsten hexachloride ethanol solution, and then reacted at 170°C for 13 hours, then the carbon cloth is taken out, rinsed with ethanol and deionized water in turn, and then dried at room temperature to obtain the electrode WO3 / WO 3-x —CC; Each 1L of the precursor aqueous solution contains 0.03mol of sodium tungstate dihydrate and 0.017mol of potassium oxalate monohydrate; Each 1L of tungsten hexachloride ethanol solution contains 0.03mol of tungsten hexachloride;

[0046] S3, electrode WO3 / WO 3-x Preparation of —3NN—CC: Dissolve the nitrite ion carrier in N,N-dimethylformamide (DMF), then add an equal volume of Nafion solution and mix evenly to obtain a mixed solution, and drop the mixed solution onto the electrode WO3 / WO obtained in step S2. 3-x—CC, and then dried at room temperature for 24 hours, and then repeatedly dripped the mixed solution onto the electrode WO3 / WO 3-x —CC was used twice to obtain the electrode for detecting nitrite (electrode WO3 / WO 3-x —3NN—CC), and after each addition, place at room temperature to dry for 24 hours.

[0047] The preparation method of the nitrite ion carrier described in this embodiment comprises the following steps:

[0048] S41, dissolving o-phenylenediamine and 3,5-di-tert-butyl salicylaldehyde in methanol to obtain a reaction solution A, wherein each 1 L of the reaction solution A contains 0.15 mol of o-phenylenediamine and 0.31 mol of 3,5-di-tert-butyl salicylaldehyde, then adding formic acid to the reaction solution A, mixing, stirring and reacting at 70° C. for 13 h, then filtering under reduced pressure to obtain a filter residue I, washing the filter residue I with ethanol, and drying to obtain an intermediate I; the volume ratio of the reaction solution A to formic acid is 4000:6;

[0049] S42. The intermediate I obtained in step S41 is dissolved in chloroform to obtain a reaction solution B, wherein each 1 L of the reaction solution B contains 0.06 mol of the intermediate I; cobalt acetate tetrahydrate is dissolved in ethanol to obtain a reaction solution C, wherein each 1 L of the reaction solution C contains 0.12 mol of cobalt acetate tetrahydrate; the reaction solution C is slowly added dropwise to the reaction solution B, and after the addition is completed, the mixture is stirred at room temperature for 2 h, and then filtered under reduced pressure to obtain a filter residue II, and the filter residue II is rinsed with ethanol and then dried to obtain a nitrite ion carrier; the molar ratio of the intermediate I to cobalt acetate tetrahydrate is 1:1.

[0050] Example 4: A method for preparing a micro-nano electrochemical electrode for in-situ detection of nitrite, comprising the following steps:

[0051] S1. Hydrophilic treatment of carbon cloth: ultrasonically clean the carbon cloth (CC) in acetone, ethanol and deionized water for 10 minutes in sequence, then take the carbon cloth to dry, then immerse the carbon cloth in a mixed acid solution for 12 hours, take it out, and then clean it with deionized water and dry it for use; the mixed acid solution is obtained by mixing concentrated sulfuric acid and concentrated nitric acid; the frequency of the ultrasonic wave used in the ultrasonic cleaning is 25KHz; the mixed acid solution is obtained by mixing concentrated sulfuric acid and concentrated nitric acid, and the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1;

[0052] S2, electrode WO3 / WO 3-xSynthesis of -CC: Sodium tungstate dihydrate and potassium oxalate monohydrate are dissolved in distilled water and the pH is adjusted to 1.5 with 3M dilute hydrochloric acid and stirred for 2 hours to obtain a precursor aqueous solution; tungsten hexachloride is dissolved in ethanol to obtain a tungsten hexachloride ethanol solution; the carbon cloth treated in step S1 is placed in a reactor, and then the precursor aqueous solution is poured in, and then the reactor is sealed and reacted at 185°C for 12 hours, then the carbon cloth is taken out, rinsed with ethanol and deionized water in turn, and then dried at 56°C, and then annealed at 555°C for 2 hours, cooled to room temperature, and then the carbon cloth is placed in the tungsten hexachloride ethanol solution, and then reacted at 185°C for 12 hours, then the carbon cloth is taken out, rinsed with ethanol and deionized water in turn, and then dried at room temperature to obtain the electrode WO3 / WO 3-x —CC; Each 1L of precursor aqueous solution contains 0.04mol of sodium tungstate dihydrate and 0.018mol of potassium oxalate monohydrate; Each 1L of tungsten hexachloride ethanol solution contains 0.04mol of tungsten hexachloride;

[0053] S3, electrode WO3 / WO 3-x Preparation of —3NN—CC: Dissolve the nitrite ion carrier in N,N-dimethylformamide (DMF), then add an equal volume of Nafion solution and mix evenly to obtain a mixed solution, and drop the mixed solution onto the electrode WO3 / WO obtained in step S2. 3-x —CC, and then dried at room temperature for 24 hours, and then repeatedly dripped the mixed solution onto the electrode WO3 / WO 3-x —CC was used 3 times to obtain the electrode for detecting nitrite (electrode WO3 / WO 3-x —3NN—CC), and after each addition, place at room temperature to dry for 24 hours.

[0054] The preparation method of the nitrite ion carrier described in this embodiment comprises the following steps:

[0055] S41, taking o-phenylenediamine and 3,5-di-tert-butyl salicylaldehyde and dissolving them in methanol to obtain a reaction solution A, wherein each 1L of the reaction solution A contains 0.16mol of o-phenylenediamine and 0.32mol of 3,5-di-tert-butyl salicylaldehyde, then adding formic acid to the reaction solution A, mixing, stirring and reacting at 85°C for 13h, then filtering under reduced pressure to obtain a filter residue I, washing the filter residue I with ethanol and drying to obtain an intermediate I; the volume ratio of the reaction solution A to formic acid is 5000:4.5;

[0056] S42. The intermediate I obtained in step S41 is dissolved in chloroform to obtain a reaction solution B, wherein each 1 L of the reaction solution B contains 0.07 mol of the intermediate I; cobalt acetate tetrahydrate is dissolved in ethanol to obtain a reaction solution C, wherein each 1 L of the reaction solution C contains 0.14 mol of cobalt acetate tetrahydrate; the reaction solution C is slowly added dropwise to the reaction solution B, and after the addition is completed, the mixture is stirred at room temperature for 3 h, and then filtered under reduced pressure to obtain a filter residue II, and the filter residue II is rinsed with ethanol and then dried to obtain a nitrite ion carrier; the molar ratio of the intermediate I to cobalt acetate tetrahydrate is 1:1.

[0057] Example 5: A method for preparing a micro-nano electrochemical electrode for in-situ detection of nitrite, comprising the following steps:

[0058] S1. Hydrophilic treatment of carbon cloth: ultrasonically clean the carbon cloth (CC) in acetone, ethanol and deionized water for 10 minutes in sequence, then take the carbon cloth to dry, then immerse the carbon cloth in a mixed acid solution for 12 hours, take it out, and then clean it with deionized water and dry it for use; the mixed acid solution is obtained by mixing concentrated sulfuric acid and concentrated nitric acid; the frequency of the ultrasonic wave used in the ultrasonic cleaning is 25KHz; the mixed acid solution is obtained by mixing concentrated sulfuric acid and concentrated nitric acid, and the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1;

[0059] S2, electrode WO3 / WO 3-x Synthesis of -CC: Sodium tungstate dihydrate and potassium oxalate monohydrate are dissolved in distilled water and the pH is adjusted to 1.6 with 1.5M dilute hydrochloric acid and stirred for 2 hours to obtain a precursor aqueous solution; tungsten hexachloride is dissolved in ethanol to obtain a tungsten hexachloride ethanol solution; the carbon cloth treated in step S1 is placed in a reactor, and then the precursor aqueous solution is poured in, and then the reactor is sealed and reacted at 190°C for 11 hours, then the carbon cloth is taken out, rinsed with ethanol and deionized water in turn, and then dried at 60°C, and then annealed at 560°C for 2 hours, cooled to room temperature, and then the carbon cloth is placed in the tungsten hexachloride ethanol solution, and then reacted at 190°C for 11 hours, then the carbon cloth is taken out, rinsed with ethanol and deionized water in turn, and then dried at room temperature to obtain the electrode WO3 / WO 3-x —CC; Each 1L of the precursor aqueous solution contains 0.05mol of sodium tungstate dihydrate and 0.019mol of potassium oxalate monohydrate; Each 1L of tungsten hexachloride ethanol solution contains 0.05mol of tungsten hexachloride;

[0060] S3, electrode WO3 / WO 3-x Preparation of —3NN—CC: Dissolve the nitrite ion carrier in N,N-dimethylformamide (DMF), then add an equal volume of Nafion solution and mix evenly to obtain a mixed solution, and drop the mixed solution onto the electrode WO3 / WO obtained in step S2. 3-x—CC, and then dried at room temperature for 24 hours, and then repeatedly dripped the mixed solution onto the electrode WO3 / WO 3-x —CC was used 3 times to obtain the electrode for detecting nitrite (electrode WO3 / WO 3-x —3NN—CC), and after each addition, place at room temperature to dry for 24 hours.

[0061] The preparation method of the nitrite ion carrier described in this embodiment comprises the following steps:

[0062] S41, taking o-phenylenediamine and 3,5-di-tert-butyl salicylaldehyde and dissolving them in methanol to obtain a reaction solution A, wherein each 1L of the reaction solution A contains 0.17 mol of o-phenylenediamine and 0.33 mol of 3,5-di-tert-butyl salicylaldehyde, then adding formic acid to the reaction solution A, mixing, stirring and reacting at 90° C. for 12 hours, then filtering under reduced pressure to obtain a filter residue I, washing the filter residue I with ethanol and drying to obtain an intermediate I; the volume ratio of the reaction solution A to formic acid is 6000:4;

[0063] S42. The intermediate I obtained in step S41 is dissolved in chloroform to obtain a reaction solution B, wherein each 1 L of the reaction solution B contains 0.08 mol of the intermediate I; cobalt acetate tetrahydrate is dissolved in ethanol to obtain a reaction solution C, wherein each 1 L of the reaction solution C contains 0.16 mol of cobalt acetate tetrahydrate; the reaction solution C is slowly added dropwise to the reaction solution B, and after the addition is completed, the mixture is stirred at room temperature for 3 h, and then filtered under reduced pressure to obtain a filter residue II, and the filter residue II is rinsed with ethanol and then dried to obtain a nitrite ion carrier; the molar ratio of the intermediate I to cobalt acetate tetrahydrate is 1:1.

[0064] Example 6: Take the electrode prepared in Example 1, use a saturated calomel electrode as a reference electrode, a platinum electrode as a counter electrode, and the micro-nano electrochemical electrode for in-situ detection of nitrite as a working electrode to form a three-electrode electrochemical detection system, and use a phosphate buffer solution (PBS, pH = 6.5) with a concentration of 0.1M as a supporting electrolyte. Then, use the chronoamperometry (it) method and adjust the applied constant voltage to 0.795V, then add sodium nitrite to the supporting electrolyte in multiple times to detect the nitrite ion concentration. The test results are as follows: Figures 5 to 8 .

[0065] according to Figures 5 to 8 The data show that the detection range of the electrode prepared by the method of the present invention for electrochemical detection of nitrite ions is 0.2-21.7 μM and 0.02-15.2 mM, and the corresponding sensitivity is 500.3 μA mM cm -2 and 600.7 μA mM cm -2, and in the range of 0.2-21.7 μM and 0.02-15.2 mM, they showed a linear relationship (0.2-21.7 μM: y=0.5003x+0.04192, R 2 =0.9996; 0.02~15.2mM:y=0.6008x+0.01682,R 2 =0.9999); at the same time, the detection limit is 0.06μM and the response time is 2s.

[0066] Example 7: Take the electrode prepared in Example 1, use the saturated calomel electrode as the reference electrode, the platinum electrode as the counter electrode, and the micro-nano electrochemical electrode for in-situ detection of nitrite as the working electrode to form a three-electrode electrochemical detection system, and use a phosphate buffer solution (PBS, pH = 6.5) with a concentration of 0.1M as the supporting electrolyte, then use the chronoamperometry (it) method and adjust the applied constant voltage to 0.795V, and then add NO2 - , 20 times the amount of NH4 + , Fe 3+ , Fe 2+ 、Ni 2+ 、Zn 2+ 、Co 2+ , Cu 2+ Mg 2+ solution, or a solution containing NO2 - , 20 times the amount of CO3 2- 、NO3 - 、SO4 2- 、S2O8 2- 、C2O4 2- solution, or a solution containing NO2 - , 20 times the amount of urea, sucrose, lactose, glycine, bovine serum albumin, sodium citrate solution, test results see Fig. 9 .according to Fig. 9 The data show that the electrode prepared by the present invention has good anti-interference ability when used for detecting nitrite ions.

[0067] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A micro-nano electrochemical electrode for in-situ detection of nitrite, comprising carbon cloth, characterized in that: The surface of the carbon cloth is provided with WO3 / WO 3-x Nano-array layer, the WO3 / WO 3-x The nanoarray layer is loaded with nitrite ion carriers.

2. The micro-nano electrochemical electrode for in-situ detection of nitrite according to claim 1, characterized in that: The molecular formula of the nitrite ion carrier is C 36 H 46 N2CoO2 and its chemical structure is:

3. The method for preparing the micro-nano electrochemical electrode for in-situ detection of nitrite according to claim 1 or 2, characterized in that: The following steps are involved: S1. Hydrophilic treatment of carbon cloth: ultrasonically clean the carbon cloth in acetone, ethanol and deionized water for 10 minutes in sequence, then take the carbon cloth to dry, then immerse the carbon cloth in a mixed acid solution for 12 hours, take it out, wash it with deionized water and dry it for later use; the mixed acid solution is obtained by mixing concentrated sulfuric acid and concentrated nitric acid; S2, electrode WO3 / WO 3-x Synthesis of -CC: dissolve sodium tungstate dihydrate and potassium oxalate monohydrate in distilled water and adjust the pH to 1.4-1.6 with dilute hydrochloric acid and stir for 2 hours to obtain a precursor aqueous solution; dissolve tungsten hexachloride in ethanol to obtain a tungsten hexachloride ethanol solution; place the carbon cloth treated in step S1 in a reactor, then pour the precursor aqueous solution into it, and then seal the reactor to react at 170-190°C for 11-13 hours, then take out the carbon cloth, rinse it with ethanol and deionized water in turn, dry it at 55-60°C, and then anneal it at 540-560°C for 2 hours, cool it to room temperature, place the carbon cloth in the tungsten hexachloride ethanol solution, and then react at 170-190°C for 11-13 hours, then take out the carbon cloth, rinse it with ethanol and deionized water in turn, and dry it at room temperature to obtain the electrode WO3 / WO 3-x —CC; S3, electrode WO3 / WO 3-x Preparation of —3NN—CC: Dissolve the nitrite ion carrier in N,N-dimethylformamide, then add an equal volume of Nafion solution and mix evenly to obtain a mixed solution, and drop the mixed solution onto the electrode WO3 / WO obtained in step S2. 3-x —CC and then dried at room temperature for 24 h to obtain an electrode for detecting nitrite.

4. The method for preparing the micro-nano electrochemical electrode for in-situ detection of nitrite according to claim 3, characterized in that: In step S1, the frequency of the ultrasonic wave used in the ultrasonic cleaning is 25 KHz; the mixed acid solution is obtained by mixing concentrated sulfuric acid and concentrated nitric acid, and the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is 3:

1.

5. The method for preparing the micro-nano electrochemical electrode for in-situ detection of nitrite according to claim 3, characterized in that: In step S2, each 1L of the precursor aqueous solution contains 0.03-0.05mol of sodium tungstate dihydrate and 0.017-0.019mol of potassium oxalate monohydrate; and each 1L of the tungsten hexachloride ethanol solution contains 0.03-0.05mol of tungsten hexachloride.

6. The method for preparing the micro-nano electrochemical electrode for in-situ detection of nitrite according to claim 3, characterized in that: In step S3, the mixed solution is added dropwise to the electrode WO3 / WO obtained in step S2. 3-x —CC, and then dried at room temperature for 24 hours, and then repeatedly dripped the mixed solution onto the electrode WO3 / WO 3-x —CC 2 to 3 times, and after each addition, place it at room temperature to dry for 24 hours.

7. The method for preparing the nitrite ion carrier according to claim 2, characterized in that: The following steps are involved: S41, dissolving o-phenylenediamine and 3,5-di-tert-butyl salicylaldehyde in methanol to obtain reaction solution A, wherein each 1 L of reaction solution A contains 0.15-0.17 mol of o-phenylenediamine and 0.31-0.33 mol of 3,5-di-tert-butyl salicylaldehyde, then adding formic acid to the reaction solution A, mixing, stirring and reacting at 70-90° C. for 12-13 h, then filtering under reduced pressure to obtain filter residue I, washing the filter residue I with ethanol and drying to obtain intermediate I; S42. The intermediate I obtained in step S41 is dissolved in chloroform to obtain a reaction solution B, wherein each 1 L of the reaction solution B contains 0.06-0.08 mol of the intermediate I; cobalt acetate tetrahydrate is dissolved in ethanol to obtain a reaction solution C, wherein each 1 L of the reaction solution C contains 0.12-0.16 mol of cobalt acetate tetrahydrate; the reaction solution C is slowly added dropwise to the reaction solution B, and after the addition is completed, the mixture is stirred at room temperature for 2-3 h, and then filtered under reduced pressure to obtain a filter residue II, and the filter residue II is rinsed with ethanol and dried to obtain a nitrite ion carrier.

8. The method for preparing the nitrite ion carrier according to claim 7, characterized in that: In step S41, the volume ratio of the reaction solution A and formic acid is (4000-6000):(4-6); in step S42, the molar ratio of the intermediate I and cobalt acetate tetrahydrate is 1:

1.

9. The use of the micro-nano electrochemical electrode for in-situ detection of nitrite as claimed in claim 1 or 2, characterized in that: The micro-nano electrochemical electrode for in-situ detection of nitrite is used to detect nitrite in water. Specifically, a saturated calomel electrode is used as a reference electrode, a platinum electrode is used as a counter electrode, and the electrode for detecting nitrite is used as a working electrode to form a three-electrode electrochemical detection system. A phosphate buffer solution with a concentration of 0.1M is used as a supporting electrolyte. Then, a chronoamperometry method is used and the external constant voltage is adjusted to 0.795V. Then, a water sample to be tested is added to the supporting electrolyte for detection.

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