An electrochemical sensitive electrode for detecting nitrite, preparation method and application thereof

Abstract

An electrochemical sensitive electrode for detecting nitrite, a preparation method and its application belong to the field of electrochemical sensing technology. First, a carbon cloth is soaked in a strong acid mixed solution for a certain period of time for pretreatment and then cleaned; secondly, a copper source, a cerium source and a sodium salt are dissolved in deionized water in a certain proportion to serve as an electroplating solution; then the pretreated carbon cloth is used as a working electrode, a platinum sheet is used as a counter electrode, and a saturated calomel electrode is used as a reference electrode, and cyclic voltammetry is used for electroplating to obtain a carbon cloth-loaded cerium ion (III)-doped copper nanoparticle sensitive electrode; and the electrode is used as a working electrode for electrochemical detection of nitrite ions. The sensitive electrode prepared by the present invention has good sensitivity to nitrite ions within a certain concentration range, can realize sensitive, accurate and rapid detection of nitrite ions, and has a low detection limit, a wide linear range, high sensitivity and excellent stability and repeatability.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical sensing, and in particular relates to an electrochemical sensitive electrode for detecting nitrite, a preparation method and application thereof. Background Art

[0002] Nitrite has excellent antibacterial and antiseptic properties and is widely used as a food additive in the food industry. However, excessive nitrite intake may cause the irreversible conversion of hemoglobin to methemoglobin, impairing its ability to carry and transport oxygen. Furthermore, nitrite readily reacts with secondary amines produced by protein breakdown to form N-nitrosamines, which are potent carcinogens and pose a significant threat to public health. Therefore, rapid and accurate nitrite detection is crucial for food safety engineering. Currently, a variety of analytical techniques have been developed for nitrite detection, including chemiluminescence, spectrophotometry, mass spectrometry, capillary electrophoresis, and chromatography. However, these techniques suffer from expensive equipment, the use of toxic reagents, and complex operation. Electrochemical detection, on the other hand, has been widely studied due to its simplicity, miniaturization, rapid response, and suitability for on-site testing.

[0003] The performance of nitrite electrochemical sensors is primarily determined by the sensitive electrodes used. Traditional glassy carbon electrodes typically require the use of conductive additives and adhesives, which increase the interfacial impedance of the electrodes, hindering electron transfer and affecting detection performance. Furthermore, the low sensitivity of traditional electrode materials makes it difficult for the sensor to detect low concentrations of nitrite. Furthermore, the high detection overpotential requires a greater energy supply to complete the detection process, resulting in energy waste.

[0004] Carbon cloth (CC) has good electrical conductivity, three-dimensional porous structure and excellent acid and alkali resistance. It is usually selected as the base material for the preparation of self-supporting electrodes, avoiding the increase in impedance caused by the use of additional conductive additives. Copper (Cu) is an element widely present on the surface of the earth's crust, with abundant reserves and economical price. Copper nanoparticles (Cu NPs) have strong electrical conductivity, excellent electrocatalytic activity and are environmentally friendly, making them have great development prospects in the field of nitrite electrocatalytic sensing. Studies have shown that the intrinsic catalytic activity of electrocatalysts can be adjusted by methods such as doping, alloying and interfacialization. The electronic configuration of cerium (Ce) is 4f 0-14 , with a unique electronic transition mode, high electronegativity and ionic conductivity. The doping of cerium (III) ions can effectively adjust the electronic structure of the electrocatalyst host lattice, affect the valence state and morphology distribution, enhance the electronic conductivity, and improve the catalytic ability of the electrocatalyst.

[0005] The present invention uses carbon cloth as a substrate and loads copper nanoparticles doped with cerium ions (III) on the surface of the substrate to construct a novel nitrite electrochemical sensitive electrode. Summary of the Invention

[0006] The present invention aims to provide an electrochemical sensitive electrode for detecting nitrite, a preparation method and applications thereof. The electrochemical sensitive electrode has good sensitivity to nitrite ions within a certain concentration range and can realize sensitive, accurate and rapid detection of nitrite ions.

[0007] The first aspect of the present invention is to provide a method for preparing an electrochemical sensitive electrode for detecting nitrite, the steps of which are as follows:

[0008] (1) Soak the carbon cloth in the pretreatment solution for a certain period of time, and then clean it with deionized water ultrasonically;

[0009] (2) dissolving a copper source, a cerium source, and a sodium salt in deionized water in a certain proportion, and stirring the mixture to obtain an electrodeposition solution;

[0010] (3) using the carbon cloth treated in step (1) as a working electrode, a platinum sheet as a counter electrode, and a saturated calomel electrode as a reference electrode, and performing electrochemical deposition in the electroplating solution obtained in step (2) by cyclic voltammetry; after the deposition is completed, washing and drying are performed to obtain the electrochemical sensitive electrode for detecting nitrite.

[0011] Preferably, in step (1), the pretreatment solution is prepared by mixing nitric acid (mass fraction of 65% to 68%) and sulfuric acid (mass fraction of 95% to 98%) in a volume ratio of 2 to 3:1, and the soaking time is 60 to 72 hours;

[0012] Preferably, in step (2), the copper source is copper sulfate with a concentration of 50 mmol / L; the cerium source is cerium sulfate with a concentration of 1.5 to 10 mmol / L; and the sodium salt is sodium sulfate with a concentration of 0.1 mol / L.

[0013] Preferably, in step (3), the potential window of the cyclic voltammetry is -1 to 2 V, the scan rate is 10 to 100 mV / s, and the number of cycles is 5 to 30 cycles.

[0014] The second aspect of the present invention is to provide an electrochemical sensitive electrode for detecting nitrite obtained by the above preparation method.

[0015] A third aspect of the present invention is to provide an application of an electrochemically sensitive electrode for detecting nitrite in electrochemical detection of nitrite ions, comprising the following steps:

[0016] (1) The electrochemical sensitive electrode prepared by the present invention is used as the working electrode, the platinum sheet is used as the counter electrode, the saturated calomel electrode is used as the reference electrode, a certain concentration of sodium nitrite standard solution is added, and a supporting electrolyte is prepared for electrochemical testing;

[0017] (2) The nitrite concentration range was determined by chronoamperometry to obtain a nitrite response curve. The linear relationship between the current intensity and the nitrite concentration was fitted and used to detect unknown nitrite concentrations.

[0018] Preferably, in step (1), the supporting electrolyte is a 0.1 M phosphate buffer solution with a pH of 5.0 to 9.0;

[0019] Preferably, in step (2), the nitrite source is a sodium nitrite solution with a concentration range of 0.25 to 4000 μM.

[0020] The beneficial effects of the present invention are:

[0021] 1. The present invention reduces the size of copper nanoparticles and inhibits agglomeration by doping them with cerium (III) ions, thereby increasing the active surface area and active sites. The charge transfer effect between the cerium (III) ions and the copper nanoparticles regulates the electronic structure of the active metal centers, reducing the electron transfer impedance of the electrode and improving electronic conductivity and electrocatalytic activity. The introduction of cerium (III) ions significantly increases the content of oxygen vacancies in the active material, further providing more nitrite catalytic active centers, improving electron transfer efficiency and electrocatalytic capacity, significantly reducing the electrochemical oxidation potential of nitrite, and enhancing electrochemical sensing performance.

[0022] 2. The electrochemical sensitive electrode of the present invention exhibits excellent sensing capabilities when detecting nitrite ions, including a low detection limit, a wide linear range, high sensitivity, and excellent stability and repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 (a) and Figure 1 (b) is the cerium ion (III) doped copper nanoparticles (5-Ce 3+ -Cu NPs / CC) at different magnifications;

[0024] pass Figure 1 (a) and Figure 1 (b) It can be found that 1-Ce prepared in Example 1 3+ -Cu NPs / CC morphology is: copper nanoparticles with a size of about 150 nm are densely and evenly wrapped on the carbon fiber surface without agglomeration.

[0025] Figure 2(a) is carbon cloth (CC), Cu / CC prepared in Comparative Example 1, and 1-Ce prepared in Example 1. 3+ -X-ray diffraction (XRD) pattern of Cu NPs / CC, Figure 2 (b) Figure 2 Partially enlarged view of (a);

[0026] pass Figure 2 (a) Results demonstrate the successful synthesis of carbon cloth-supported copper particles and carbon cloth-supported cerium-doped copper nanoparticles sensitive electrodes; Figure 2 (b) 1-Ce can be found 3+ -Cu NPs / CC XRD diffraction peaks become broad and shift to lower angles, which proves that Ce 3+ It was successfully doped into Cu nanoparticles.

[0027] Figure 3 1-Ce prepared in Example 1 3+ -Cu NPs / CC, 2-Ce prepared in Example 2 3+ -Cu NPs / CC and 3-Ce prepared in Example 3 3+ -CV test result curve of Cu NPs / CC to 500 μM nitrite;

[0028] pass Figure 3 It can be found that the prepared 1-Ce 3+ -Cu NPs / CC, 2-Ce 3+ -Cu NPs / CC and 3-Ce 3+ -Cu NPs / CC showed the corresponding nitrite oxidation peaks, and 1-Ce 3+ -Cu NPs / CC has the largest oxidation peak current intensity.

[0029] Figure 4 (a) is 1-Ce prepared in Example 1 3+ -Cu NPs / CC chronoamperometric test curves for different concentrations of nitrite, Figure 4 (c) Figure 4 Enlarged view of the marked part in (a); Figure 4 (b) is the linear relationship curve between nitrite concentration and current intensity. Figure 4 (d) Figure 4 (b) Enlarged view of the marked part;

[0030] pass Figure 4 (a) and Figure 4 (c) It can be found that with the continuous addition of nitrite, the response current shows a step-like upward trend; Figure 4 (b) and Figure 4(d) It can be found that in the range of nitrite concentration from 0.25 to 500 μM, the linear relationship is y = 3.723x + 0.110 (R 2 =0.999), with a sensitivity of 3723 μA mM -1 cm -2 In the range of nitrite concentration from 500 to 4000 μM, the linear relationship is y = 1.769x + 1.157 (R 2 =0.999), the sensitivity is 1769μAmM -1 cm -2 The parameter y represents the current intensity, and the parameter x represents the nitrite concentration. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the implementation methods of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for preparing an electrochemically sensitive electrode for detecting nitrite, comprising the following steps:

[0034] 1. Mix concentrated nitric acid (68% by mass) and concentrated sulfuric acid (98% by mass) in a volume ratio of 3:1 to prepare a pretreatment solution. Soak the carbon cloth in the pretreatment solution for 72 hours. After the pretreatment, remove the carbon cloth and rinse it with deionized water for later use.

[0035] 2. Dissolve copper sulfate, cerium sulfate, and sodium sulfate in 50 mL of deionized water to obtain a mixed solution of 50 mmol / L copper sulfate, 5 mmol / L cerium sulfate, and 0.1 mol / L sodium sulfate, which is used as the electrodeposition solution;

[0036] 3. The carbon cloth treated in step (1) is used as the working electrode, the platinum sheet is used as the counter electrode, and the saturated calomel electrode is used as the reference electrode. Cyclic voltammetry is used to perform electrodeposition in the electrodeposition solution of step (2). The potential window is set to -1 to 2 V, the scanning speed is 50 mV / s, and the number of cycles is 20. After the electrodeposition is completed, it is cleaned with deionized water and dried at 60°C to obtain the electrochemical sensitive electrode (1-Ce) for detecting nitrite. 3+ -Cu NPs / CC).

[0037] 4. Prepare phosphate buffer solution with a concentration of 0.1M and a pH of 7 as the electrolyte for sodium nitrite detection. 3+ -Cu NPs / CC was used as the working electrode, platinum sheet was used as the counter electrode, and saturated calomel electrode was used as the reference electrode. Cyclic voltammetry was used to test the sensitivity of sodium nitrite. The potential window was 0.2-1.0V, and the sensing characteristics of 0.5mM sodium nitrate were tested at a scan rate of 50mV / s. In addition, the linearity test of sodium nitrite in the concentration range of 0.1-4000μM was carried out by chronoamperometry at an applied voltage of 0.74V. Under the condition of stable stirring of the electrolyte, sodium nitrite standard solution was continuously added to obtain the corresponding response current, and the linear relationship between the current intensity and the nitrite concentration was obtained by fitting. The results show that the prepared 1-Ce 3+ -Cu NPs / CC electrode showed a peak current intensity of 1.1 mA cm-3 for nitrite oxidation in cyclic voltammetry test. -2 In the chronoamperometric test, the sensitivity was 3723 μA mM in the range of nitrite concentration from 0.25 to 500 μM. -1 cm -2 ; In the range of nitrite concentration of 500~4000μM, the sensitivity is 1769μA mM -1 cm -2 .

[0038] Example 2:

[0039] 1. The carbon cloth pretreatment process is the same as in Example 1;

[0040] 2. Dissolve copper sulfate, cerium sulfate and sodium sulfate in 50 mL of deionized water to obtain a mixed solution of 50 mmol / L copper sulfate, 2.5 mmol / L cerium sulfate and 0.1 mol / L sodium sulfate, which is used as the electrodeposition solution.

[0041] 3. The electrode preparation process is the same as in Example 1;

[0042] 4. The electrochemical test process was the same as in Example 1. The results showed that the prepared 2-Ce 3+ -Cu NPs / CC electrode exhibited a peak current intensity of 0.93 mA cm-3 for nitrite oxidation in cyclic voltammetry. -2 .

[0043] Example 3:

[0044] 1. The carbon cloth pretreatment process is the same as in Example 1;

[0045] 2. Dissolve copper sulfate, cerium sulfate and sodium sulfate in 50 mL of deionized water to obtain a mixed solution of 50 mmol / L copper sulfate, 10 mmol / L cerium sulfate and 0.1 mol / L sodium sulfate, which is used as the electrodeposition solution.

[0046] 3. The electrode preparation process is the same as in Example 1;

[0047] 4. The electrochemical test process was the same as in Example 1. The results showed that the prepared 3-Ce 3+ -Cu NPs / CC electrode showed a peak current intensity of 0.73 mA cm-3 for nitrite oxidation in cyclic voltammetry test. -2 .

[0048] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0049] Comparative Example 1:

[0050] 1. The carbon cloth pretreatment process is the same as in Example 1;

[0051] 2. Dissolve copper sulfate and sodium sulfate in 50 mL of deionized water to obtain a mixed solution of 50 mmol / L copper sulfate and 0.1 mol / L sodium sulfate, which is used as the electrodeposition solution;

[0052] 3. The electrode preparation process is the same as in Example 1;

[0053] 4. The electrochemical test process was the same as in Example 1. The results showed that the peak current intensity of the oxidation of nitrite by the prepared Cu / CC electrode in the cyclic voltammetry test was 0.69 mA cm -2 .

Claims

1. A method for preparing an electrochemically sensitive electrode for detecting nitrite, comprising the following steps: (1) Soak the carbon cloth in the pretreatment solution for a certain period of time, and then clean it with deionized water ultrasonically; (2) Dissolve the copper source, cerium source and sodium salt in deionized water in a certain proportion and stir evenly to obtain an electrodeposition solution; (3) using the carbon cloth treated in step (1) as a working electrode, a platinum sheet as a counter electrode, and a saturated calomel electrode as a reference electrode, and performing electrodeposition by cyclic voltammetry in the electrodeposition solution obtained in step (2); After the deposition is completed, the electrode is cleaned and dried to obtain the electrochemical sensitive electrode for detecting nitrite; In step (1), the pretreatment solution is prepared by nitric acid with a mass fraction of 65% to 68% and sulfuric acid with a mass fraction of 95% to 98% in a volume ratio of 2 to 3:1, and the immersion time is 60 to 72 hours; in step (2), the copper source is copper sulfate with a concentration of 50 mmol / L; the cerium source is cerium sulfate with a concentration of 1.5 to 10 mmol / L; and the sodium salt is sodium sulfate with a concentration of 0.1 mol / L.

2. The method for preparing an electrochemical sensitive electrode for detecting nitrite according to claim 1, wherein: The potential window of cyclic voltammetry in step (3) is -1 to 2 V, the scan rate is 10 to 100 mV / s, and the number of cycles is 5 to 30.

3. An electrochemical sensitive electrode for detecting nitrite, characterized in that: The method is prepared by the method according to any one of claims 1 or 2.

4. Use of the electrochemical sensitive electrode for detecting nitrite according to claim 3 in electrochemical detection of nitrite ions.

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