Preparation method and application of transition metal oxide electrochemical sensor

Abstract

The invention discloses a preparation method and application of a transition metal oxide electrochemical sensor, and belongs to the field of electrochemical sensors.The preparation method of the transition metal oxide electrochemical sensor comprises the steps that firstly, a nickel foam substrate is pretreated, and then a transition metal compound solution and nickel foam are subjected to hydrothermal and calcination treatment together; the transition metal oxide self-supporting material is obtained, the prepared transition metal oxide self-supporting working electrode is used for detecting nitrite, the electrode response time is short, the sensitivity is high, the linear response range is wide, the detection lower limit is low, the working electrode only needs hydrothermal and calcination treatment, no complex synthesis treatment process is needed, and the method is suitable for large-scale industrial production. The preparation process is simple, and meanwhile, the problems that in the existing preparation process, an electrode modification layer needs to be fixed on the surface of an electrode through a polymer binder, active sites cover each other, resistance is increased, and catalytic activity is reduced are solved.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical sensors, and more specifically, to a preparation method and application of a transition metal oxide electrochemical sensor. Background Art

[0002] Nitrite is a general term for salts containing nitrite anions, the most common of which is sodium nitrite. Nitrite is an inorganic salt that is easily decomposed and has strong toxicity. Because it tastes and looks similar to table salt, it is easy to be ingested by mistake. In order to ensure food safety, nitrite content is an important indicator for testing food safety. Therefore, establishing an accurate and rapid detection method for nitrite is of great research significance.

[0003] The detection methods of nitrite include spectrophotometry, ion chromatography, capillary electrophoresis, fluorescence spectroscopy and electrochemical method;

[0004] The sensitivity of spectrophotometry is poor, and the requirements for detection conditions are high. The temperature, acidity, and the choice of reagents will affect the results of the experiment, resulting in deviations in the experimental results.

[0005] In capillary electrophoresis, due to its small diameter, impurities clog the capillary wall, interfering with the analytical signal and even damaging the instrument;

[0006] Electrochemical sensors consist of two parts: recognition elements and sensors. The combination of analytes and recognition elements generates chemical or physical signals, which are then converted into measurable output signals. The concentration of the analyte is quantitatively analyzed by detecting changes in potential, current, resistance or conductivity. Therefore, the electrochemical method has the advantages of simple equipment, high sensitivity, good selectivity, low detection limit, and fast analysis speed.

[0007] Nitrite electrochemical sensor is an emerging detection technology. Compared with other detection methods, electrochemical detection of nitrite has the advantages of low cost, rapid analysis, good portability, and the ability to meet the requirements of rapid on-site detection. Therefore, electrochemical sensor is one of the detection technologies with great research prospects.

[0008] The principle of electrochemical detection of nitrite is that nitrite ions have both oxidizing and reducing properties. Nitrite can be quantitatively detected by electrocatalytic oxidation or reduction. Electrocatalytic oxidation is the oxidation of nitrite into nitrate, which reduces the interference when nitrate is present. Therefore, electrocatalytic oxidation is often used to determine nitrite. When an external voltage is present, NO2 -The oxidation reaction, the reaction rate is the speed of electron transfer, which can be detected by the sensor to generate a current signal on the electrode. The nitrite concentration and the response current intensity are linearly related, so the nitrite concentration can be measured. Therefore, the electrochemical method can realize the rapid quantitative detection of nitrite.

[0009] At present, the electrodes used in the electrochemical detection of nitrite are mostly enzymes, metal materials, metal organic frameworks and carbon materials. During the preparation process, a binder is needed to fix the electrode modification layer on the electrode surface, which increases the resistance and reduces the catalytic activity. Summary of the invention

[0010] 1. Technical problems to be solved

[0011] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for preparing and applying a transition metal oxide electrochemical sensor, which can be realized with a simple preparation process and solves the problem that a polymer binder is required in the prior preparation process to fix the electrode modification layer on the electrode surface, so that the active sites cover each other, resulting in an increase in resistance and thus a decrease in catalytic activity.

[0012] 2. Technical solution

[0013] To solve the above problems, the present invention adopts the following technical solutions.

[0014] A method for preparing a transition metal oxide electrochemical sensor comprises the following steps:

[0015] S1: Pre-treat and clean the 1x1 cm nickel foam substrate material and dry it for later use;

[0016] S2: Weigh 0.1-2 mmol of ferric chloride, 0.1-2 mmol of nickel chloride and 0.5-5 mmol of urea, dissolve the weighed ferric chloride, nickel chloride and urea in 10-80 ml of primary water, stir and mix well, and obtain a first mixed solution;

[0017] S3: adding the first mixed solution and the reserved nickel foam into a reaction kettle, heating at 80-160° C. for 4-10 hours to obtain a precursor, and then cleaning and drying it for later use;

[0018] S4: placing the reserved precursor into a tube furnace, and annealing at 200-500° C. for 0.5-3 h in an argon atmosphere to obtain an iron-nickel-based oxide nanomaterial, i.e., a transition metal oxide nanomaterial;

[0019] S5: Electrochemical sensors are fabricated using transition metal oxide nanomaterials as working electrodes.

[0020] Furthermore, the amount of urea in S1 is 0.7-4.5 mmol.

[0021] Furthermore, the amount of urea in S1 is 0.9-4 mmol.

[0022] Furthermore, the amount of urea in S1 is 1.2-3.5 mmol.

[0023] Furthermore, the amount of urea in S1 is 1.5-3 mmol.

[0024] Application of a transition metal oxide electrochemical sensor for detecting nitrite.

[0025] 3. Beneficial effects

[0026] Compared with the prior art, the advantages of the present invention are:

[0027] (1) The working electrode preparation method of this scheme is relatively simple, and it also solves the problem that in the existing preparation process, a polymer binder is required to fix the electrode modification layer on the electrode surface, so that the active sites cover each other, resulting in an increase in resistance and a decrease in catalytic activity.

[0028] (2) The transition metal oxide prepared in this scheme is used as the working electrode of the nitrite electrochemical sensor for detecting nitrite. The electrode has a fast response time, high sensitivity, a wide linear response range and a low detection limit. The prepared electrochemical sensor has the advantages of high specificity, excellent stability and strong anti-interference ability for nitrite detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a preparation flow chart of the present invention;

[0030] Figure 2 A schematic diagram of the preparation of the present invention;

[0031] Figure 3 This is a schematic diagram of the principle of nitrite detection using the transition metal oxide nanomaterials of the present invention as working electrodes to assemble into a three-electrode system. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

[0033] Embodiment 1:

[0034] See also Figure 1-3, a method for preparing a transition metal oxide electrochemical sensor, comprising the following steps:

[0035] Step 1: Pre-treat the 1x1 cm nickel foam substrate material and dry it for later use;

[0036] Step 2: Weigh 0.1-2 mmol of ferric chloride, 0.1-2 mmol of nickel chloride and 0.5-5 mmol of urea, dissolve the weighed ferric chloride, nickel chloride and urea in 10-80 ml of primary water, stir and mix well to obtain a first mixed solution;

[0037] Step 3: Add the first mixed solution and the reserved nickel foam into a reaction kettle, heat at 80-160° C. for 4-10 hours to obtain a precursor, and then clean and dry it for later use;

[0038] Step 4: placing the reserved precursor into a tube furnace, and annealing at 200-500° C. for 0.5-3 h in an argon (hereinafter referred to as Ar) atmosphere to obtain an iron-nickel based oxide nanomaterial, i.e., a transition metal oxide nanomaterial;

[0039] Step 5: Use the above transition metal oxide nanomaterials as working electrodes to make electrochemical sensors.

[0040] Since the method for making an electrochemical sensor is a mature prior art, and the difference between the present technical solution and the prior art is only in the working electrode, the preparation in step 5 will not be described in detail.

[0041] Moreover, it was found through experiments that the working electrode made with 0.7-4.5 mmol of urea was better than the working electrode made with 0.5-5 mmol of urea.

[0042] The working electrode made with 0.9-4 mmol of urea is better than the working electrode made with 0.7-4.5 mmol of urea.

[0043] The working electrode made with 1.2-3.5 mmol of urea is better than the working electrode made with 0.9-4 mmol of urea.

[0044] The working electrode prepared with 1.5-3 mmol of urea has better effect than the working electrode prepared with 1.2-3.5 mmol of urea.

[0045] In summary, the working electrode preparation method of the present invention is relatively simple, and at the same time solves the problem that in the existing preparation process, a polymer binder is required to fix the electrode modification layer on the electrode surface, so that the active sites cover each other, resulting in an increase in resistance and thus a decrease in catalytic activity.

[0046] Embodiment 2:

[0047] See also Figure 1 As shown, the difference between this embodiment and embodiment 1 lies in the setting of various parameters, which is specifically that the preparation method includes the following steps:

[0048] A. Pre-treat the 1x1 cm nickel foam substrate material and dry it for later use;

[0049] B. Weigh 0.2 mmol of ferric chloride, 1.8 mmol of nickel chloride and 0.8 mmol of urea, dissolve the weighed ferric chloride, nickel chloride and urea in 20 ml of primary water, stir and mix well to obtain a first mixed solution;

[0050] C. Add the first mixed solution and the reserved nickel foam into a reaction kettle, heat at 100° C. for 4 h to obtain a precursor, and then clean and dry it for later use;

[0051] D. placing the reserved precursor into a tube furnace and annealing it at 200° C. for 0.5 h in an Ar atmosphere to obtain a transition metal oxide nanomaterial;

[0052] E. Use the above transition metal oxide nanomaterials as working electrodes to make electrochemical sensors.

[0053] Embodiment 3:

[0054] See also Figure 1-3 As shown, the difference between this embodiment and the above embodiments lies in the setting of various parameters, which is specifically that the preparation method includes the following steps:

[0055] A. Pre-treat the 1x1 cm nickel foam substrate material and dry it for later use;

[0056] B. Weigh 0.3 mmol of ferric chloride, 1.7 mmol of nickel chloride and 1.2 mmol of urea, dissolve the weighed ferric chloride, nickel chloride and urea in 30 ml of primary water, stir and mix well to obtain a first mixed solution;

[0057] C. Add the first mixed solution and the reserved nickel foam into a reaction kettle, heat at 140° C. for 7 hours to obtain a precursor, and then clean and dry it for later use;

[0058] D. placing the reserved precursor into a tube furnace and annealing it at 300° C. for 1.5 h in an Ar atmosphere to obtain a transition metal oxide nanomaterial;

[0059] E. Use the above transition metal oxide nanomaterials as working electrodes to make electrochemical sensors.

[0060] Embodiment 4:

[0061] See also Figure 1-3 As shown, the difference between this embodiment and the above embodiments lies in the setting of various parameters, which is specifically that the preparation method includes the following steps:

[0062] A. Pre-treat the 1x1 cm nickel foam substrate material and dry it for later use;

[0063] B. Weigh 1 mmol of ferric chloride, 1 mmol of nickel chloride and 4 mmol of urea, dissolve the weighed ferric chloride, nickel chloride and urea in 60 ml of primary water, stir and mix well to obtain a first mixed solution;

[0064] C. Add the first mixed solution and the reserved nickel foam into a reaction kettle, heat at 150° C. for 9 hours to obtain a precursor, and then clean and dry it for later use;

[0065] D. placing the reserved precursor into a tube furnace and annealing at 400° C. for 2 h in an Ar atmosphere to obtain transition metal oxide nanomaterials;

[0066] E. Use the above transition metal oxide nanomaterials as working electrodes to make electrochemical sensors.

[0067] Embodiment 5:

[0068] See also Figure 1-3 As shown, this embodiment discloses the application of transition metal oxide electrochemical sensors based on embodiment 1, which specifically uses the electrochemical sensors using transition metal oxide nanomaterials prepared in embodiments 1-4 as working electrodes to detect nitrite;

[0069] In order to demonstrate the performance of using the transition metal oxide nanomaterial as the working electrode of the nitrite electrochemical sensor for detecting nitrite, the technical scheme uses the transition metal oxide nanomaterial as the working electrode to carry out a nitrite detection experiment, the saturated calomel electrode is the reference electrode, the platinum wire electrode is the counter electrode, and the working electrode, the saturated calomel electrode and the platinum wire electrode are placed in the electrolytic cell respectively to make a three-electrode electrolytic cell, and the area of ​​the working electrode is 1x1 cm 2 , connect each electrode to the electrochemical workstation;

[0070] ① Test on the catalytic oxidation performance of transition metal oxide self-supporting electrode on nitrite:

[0071] A 0.1 M PBS buffer solution (PH = 7.0) was prepared and added to the three-electrode electrolytic cell of this embodiment. Cyclic voltammetry was performed at 50 mV s -1 The catalytic oxidation performance of the electrode was tested in a solution containing 1.0 mM nitrite at a scan rate of .

[0072] ②Sensing performance test of nitrite electrochemical sensor based on metal oxide:

[0073] The three-electrode system of this embodiment was inserted into a 0.1 M PBS buffer solution (pH = 7.0). At an applied potential of 0.8 V, nitrite solutions of different concentrations were added to the continuously stirred PBS buffer solution every 100 s, and electrochemical data were measured through the current-time curve.

[0074] ③Specific performance test of transition metal-based nitrite electrochemical sensor:

[0075] The three-electrode system of this example was inserted into a 0.1 M PBS buffer solution (pH = 7.0). At an applied potential of 0.8 V, interfering substances with 50 times and 100 times the concentration of nitrite (2.5 μM) were added every 50 s, respectively: potassium nitrate, ammonium acetate, magnesium sulfate, sodium silicate, zinc sulfate, sodium carbonate, calcium chloride and glucose, and the resulting current-time curves were recorded.

[0076] ④Stability and repeatability test of transition metal-based nitrite electrochemical sensor:

[0077] The three-electrode system of this example was inserted into a 0.1 M PBS buffer solution (pH = 7.0) and cyclic voltammetry was performed at 50 mV s -1 The same electrode was tested for stability in a 1.0 mM nitrite solution at a scan rate of 1.0 mM for one month. Six different electrodes were prepared independently using the same method and tested for repeatability.

[0078] After summarizing the above experiments, it can be seen that transition metal oxides are used as the working electrode of nitrite electrochemical sensors to detect nitrite. The electrode has a fast response time, high sensitivity, a wide linear response range and a low detection limit. The prepared electrochemical sensor has the advantages of high specificity, excellent stability and strong anti-interference ability for nitrite detection.

[0079] The above is only a preferred specific implementation of the present invention; however, the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and its improved conception within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a transition metal oxide electrochemical sensor, characterized in that: The following steps are involved: S1: Pre-treat and clean the 1x1 cm nickel foam substrate material and dry it for later use; S2: Weigh 0.1-2 mmol of ferric chloride, 0.1-2 mmol of nickel chloride and 0.5-5 mmol of urea, dissolve the weighed ferric chloride, nickel chloride and urea in 10-80 ml of primary water, stir and mix well, and obtain a first mixed solution; S3: adding the first mixed solution and the reserved nickel foam into a reaction kettle, heating at 80-160° C. for 4-10 hours to obtain a precursor, and then cleaning and drying it for later use; S4: placing the reserved precursor into a tube furnace, and annealing at 200-500° C. for 0.5-3 h in an argon atmosphere to obtain an iron-nickel-based oxide nanomaterial, i.e., a transition metal oxide nanomaterial; S5: Electrochemical sensors are fabricated using transition metal oxide nanomaterials as working electrodes.

2. The preparation method and application of a transition metal oxide electrochemical sensor according to claim 1, characterized in that: The amount of urea in S1 is 0.7-4.5 mmol.

3. The preparation method and application of a transition metal oxide electrochemical sensor according to claim 1, characterized in that: The amount of urea in S1 is 0.9-4 mmol.

4. The preparation method and application of a transition metal oxide electrochemical sensor according to claim 1, characterized in that: The amount of urea in S1 is 1.2-3.5 mmol.

5. The preparation method and application of a transition metal oxide electrochemical sensor according to claim 1, characterized in that: The amount of urea in S1 is 1.5-3 mmol.

6. An application of a transition metal oxide electrochemical sensor, the electrochemical sensor prepared by the preparation method according to any one of claims 1 to 5, characterized in that: Used to detect nitrite.

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