Ni-hitp-based non-enzyme ascorbic acid electrochemical sensing electrode and application thereof

Abstract

The application relates to the technical field of electrochemical sensors, in particular to an enzyme-free ascorbic acid electrochemical sensing electrode based on Ni-HITP and application thereof. The electrochemical sensing electrode is a Ni3(HITP)2 / CC electrode modified by two-dimensional conjugated MOF Ni-HITP and directly used as an electrode material and a sensing interface, and is prepared by adopting a simple hydrothermal method with carbon cloth as a substrate. The electrochemical sensing electrode is used for high-sensitivity enzyme-free ascorbic acid electrochemical sensing. In a 0.1M NaOH solution, ascorbic acid sensing test is carried out by using an optimal potential of 0.55V. The electrochemical sensing electrode has excellent performances such as a large detection range, a low detection limit, high sensitivity, rapid response, high selectivity and high stability, and has great application potential.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical sensor, in particular to a non-enzyme ascorbic acid electrochemical sensing electrode based on Ni-HITP and application thereof. BACKGROUND

[0002] Ascorbic acid (AA) is an antioxidant, also known as vitamin C, and is an essential nutrient for the human body. The normal concentration range of AA in human daily life is 34-114 μM. As an antioxidant, AA can reduce the incidence of cancer by effectively scavenging free radicals in the body. In addition, AA maintains enzyme activity, inhibits the production of toxic substances through peroxidation, and plays an important role in the synthesis of adrenaline and neurotransmitters and the digestion of amino acids in biological metabolism. Therefore, it is of great significance to develop a reliable and effective ascorbic acid detection method to detect the AA level of the human body in real time for the health of the body.

[0003] Electrochemical sensors combine the specificity of electrochemical sensors and biomolecules, and have attracted widespread attention due to their simple device, fast response, and high sensitivity. Electrochemical sensors are divided into enzyme-based sensors and non-enzyme sensors. Enzyme-based electrochemical biosensors have excellent sensitivity and selectivity. In enzyme-based biosensors, AA is oxidized to dehydroascorbic acid by ascorbic acid oxidase under aerobic conditions, but its application is greatly limited due to its high cost, poor stability, and difficulty in immobilization. Non-enzyme sensors overcome the limitations of traditional enzyme-based sensors and are widely used in agriculture, food analysis, environmental monitoring, biomedical detection, and other fields. The electrocatalytic oxidation of AA does not require the participation of biological enzymes, provides good stability, and allows for easy storage and relatively simple sensor design. However, most of the core sensing materials of current such sensing systems have low specific surface area and few active catalytic sites, and the preparation process is complex. Therefore, designing new catalytic materials with clear chemical composition and porous structure is an important aspect of improving the performance of electrochemical sensors. In addition, although new materials for non-enzyme electrochemical sensing electrodes are constantly emerging, the preparation process of the electrode often requires the modification of nanomaterials to the surface of commercialized substrate electrodes such as glassy carbon electrodes, gold electrodes, and ITO through various methods, which is complex. During the immobilization process, nanomaterials are prone to aggregation or detachment, resulting in large differences between different batches of electrodes, which makes it difficult to achieve batch production and application of the electrode. Therefore, further simplifying the production process of non-enzyme sensing electrodes, achieving batch production of electrodes, and ensuring the reproducibility of different batches of electrodes are technical bottlenecks that must be overcome in the commercialization process of non-enzyme sensing electrodes. SUMMARY

[0004] In order to solve the problems mentioned in the background art, the purpose of the present application is to provide a non-enzyme ascorbic acid electrochemical sensing electrode based on Ni-HITP and application thereof.

[0005] The object of the present application can be achieved by the following technical solutions:

[0006] An enzyme-free ascorbic acid electrochemical sensing electrode based on Ni-HITP, the preparation method of the electrochemical sensing electrode comprises the following steps:

[0007] Step 1, add 2,3,6,7,10,11-hexamino triphenyl (HITP) ligand into a scintillation bottle, add ultrapure water and N,N-dimethylformamide into the bottle, ultrasonic mixing to obtain a ligand solution;

[0008] Step 2, under ultrasonic conditions, add nickel metal salt into the ligand solution, and after the nickel metal salt is completely dissolved, a reaction solution is obtained;

[0009] Step 3, put activated carbon cloth (CC) into the scintillation bottle, ultrasonic oscillation, then slowly add ammonia water into the solution using a pipette, after adding, place the scintillation bottle in an oven and heat at 60-70℃ for 4-8h, discharge, take out the electrode, and then wash with ultrapure water, acetone and ethanol in sequence, and then dry to obtain the electrochemical sensing electrode.

[0010] In the above technical solution, activated carbon cloth is used as the substrate, 2,3,6,7,10,11-hexamino triphenyl is used as the ligand, and the Ni3(HITP)2 / CC electrode, i.e. the electrochemical sensing electrode, is prepared by in-situ growth of active MOF material on the surface of the activated carbon cloth.

[0011] Further, in the second step, the nickel metal salt is any one of nickel acetate, nickel chloride, nickel nitrate or nickel sulfate, and preferably is nickel acetate.

[0012] Further, in the third step, the preparation method of the activated carbon cloth comprises the following steps:

[0013] Step 1, cut the carbon cloth into a sample cloth with a size of 3.5cm×4.5cm, put it into acetone, ultrasonic treatment for 10-20min, wash the dust and organic matter attached to the surface, take out and transfer to ultrapure water, ultrasonic treatment for 1-2 times, each time for 10-20min, take out, and finally ultrasonic treatment in anhydrous ethanol for 1-2 times, each time for 10-20min, take out, and dry in an oven at 60-70℃ for 8-12h to obtain the pretreated carbon cloth;

[0014] Step 2, add the pretreated carbon cloth into a mixed solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:1, soak at room temperature for 9-12h, take out the carbon cloth, wash by the same method as step 1, and dry after removing the strong acid to obtain the activated carbon cloth.

[0015] The application of an enzyme-free ascorbic acid electrochemical sensing electrode based on Ni-HITP, the electrochemical sensing electrode is used as an active electrode, and is applied to the enzyme-free electrochemical sensing ascorbic acid.

[0016] Further, the application method is as follows:

[0017] The electrochemical sensing electrode is used as a working electrode, a platinum wire is used as a counter electrode, a silver / silver chloride electrode is used as a reference electrode, a 0.1 mol / L sodium hydroxide solution is used as an electrolyte, a standard three-electrode system is used, an electrochemical workstation is used, the presence or absence of redox peaks in the cyclic voltammogram and the change of the peak position and peak value before and after the addition of ascorbic acid are tested through the cyclic voltammogram, and the response ability of the electrochemical sensing electrode to ascorbic acid is judged.

[0018] Further, the specific method of the test is as follows:

[0019] (1) Determining the optimal test potential

[0020] The electrochemical sensing electrode is taken, first, the cyclic voltammetry is used for scanning until the signal is stable, then the current-time curve method is used, 100 s is run, the current is stabilized, different initial potentials are selected, the ascorbic acid solution with a concentration of 0.2-2 mol / L is added every 20-80 s, a total of 5-10 times, the time-current curve under different initial potentials is obtained, and the optimal potential is selected for the next step.

[0021] (2) Drawing a standard curve

[0022] The optimal potential is used, the ascorbic acid solution with different concentrations is added every 20-80 s, the time-current curve is obtained, the standard curve between the concentration of the added ascorbic acid solution and the corresponding current is drawn, and the sensitivity, detection limit and detection range parameters are obtained.

[0023] The beneficial effects of the present application are as follows:

[0024] 1) A simple one-step hydrothermal method is used, the preparation conditions are mild, and the process is energy-saving and simple.

[0025] 2) The active MOF material in the composite electrode prepared by the preparation method has excellent combination stability with the substrate, does not fall off in the catalytic process, and the morphology does not change obviously after catalysis.

[0026] 3) The electrochemical sensing electrode of the present application only has obvious reaction with ascorbic acid, other small molecules with reduction have little effect on it, and has good selectivity and specificity.

[0027] 4) The electrochemical sensor of the present application is easy to prepare, is convenient for detection of hydrogen peroxide in various water bodies, has simple and easy-to-operate preparation process, short reaction time, strong signal response and good reproducibility.

[0028] Of course, implementing any product of the present application does not necessarily require achieving all the advantages described above at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed for the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort based on these drawings.

[0030] Figure 1 Scanning electron microscope images of the electrochemical sensing electrodes in Examples 2-5, wherein (a) is the electron microscope image of the Ni3(HITP)2 / CC-0 electrode in Example 2; (b) is the electron microscope image of the Ni3(HITP)2 / CC-0.3 electrode in Example 3; (c) is the electron microscope image of the Ni3(HITP)2 / CC-0.5 electrode in Example 4; (d) is the electron microscope image of the Ni3(HITP)2 / CC-1 electrode in Example 5;

[0031] Figure 2 EDS image of the Ni3(HITP)2 / CC-0.3 electrode in Example 3;

[0032] Figure 3 XPS image of the Ni3(HITP)2 / CC-0.3 electrode in Example 3;

[0033] Figure 4 XRD image of the Ni3(HITP)2 powder in Example 3;

[0034] Figure 5 FT-IR image of the Ni3(HITP)2 powder in Example 3;

[0035] Figure 6 TEM image of the Ni3(HITP)2 powder in Example 3;

[0036] Figure 7 CV response curve comparison chart of different electrodes prepared in Examples 1-5 before and after adding AA;

[0037] Figure 8 Current-time response curve chart of the Ni3(HITP)2 / CC-0.3 electrode in Example 3 after continuously adding AA at different potentials;

[0038] Figure 9 (a) is the current-time response curve of the Ni3(HITP)2 / CC-0.3 electrode in Example 3 after continuously adding AA; Figure 9(b) is the standard curve between the concentration of AA added and the response current of the Ni3(HITP)2 / CC-0.3 electrode in Example 3;

[0039] Figure 10 is the current-time response curve of the product of Example 3 of the present application to the alternating addition of interferents and AA;

[0040] Figure 11 (a) is the stability test chart of the Ni3(HITP)2 / CC-0.3 electrode in Example 3 of the present application within 30 days; Figure 11 (b) is the parallel response test results of 5 identical electrodes;

[0041] Figure 12 is the scanning electron microscope image of the Ni3(HITP)2 / CC-0.3 electrode in Example 3 of the present application after AA sensing test. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0043] Example 1

[0044] Preparation of activated carbon cloth

[0045] An initial carbon cloth of 15 cm x 15 cm is cut into a sample cloth of specifications 3.5 cm x 4.5 cm, which is put into acetone and ultrasonically treated for 15 min, taken out, transferred to contain ultrapure water, ultrasonically treated twice for 10 min each time, taken out, finally ultrasonically treated twice for 10 min each time in ethanol, taken out, and dried in an oven at 70°C for 12 h to obtain a pretreated carbon cloth;

[0046] Step two, the pretreated carbon cloth is added to a mixed solution of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1, and after room temperature soaking for 12 h, the carbon cloth is taken out and cleaned by the same washing method as step one to remove the strong acid residues on the surface of the carbon cloth, and dried to obtain the activated carbon cloth.

[0047] Example 2

[0048] Preparation of electrochemical sensing electrode

[0049] First step, 10 mg of 2,3,6,7,10,11-hexamino triphenylamine (HITP) ligand is added to a scintillation bottle, 5 mL of ultrapure water and 0 mL of N,N-dimethylformamide are added to the bottle, and ultrasonic mixing is performed to obtain a ligand solution;

[0050] Second step, under ultrasonic condition, 7mg nickel acetate was added into the ligand solution, until the nickel metal salt was completely dissolved, to obtain the reaction solution;

[0051] Third step, the activated carbon cloth (CC) prepared in Example 1 was cut into small pieces of 2.2x1.6cm, which was put into a flask, and the solution was fully contacted with the carbon cloth fiber by ultrasonic oscillation. Then 200μL ammonia was slowly added into the solution using a 1mL pipette. After the addition was completed, the flask was quickly placed in an oven for heating at 65℃ for 6h. The electrode was taken out and washed with ultrapure water, acetone and ethanol in sequence, and then dried to obtain an electrochemical sensing electrode, which was recorded as Ni3(HITP)2 / CC-0.

[0052] The Ni3(HITP)2 / CC-0 was analyzed by field emission scanning electron microscopy, and the results are shown in Figure 1 (a). As can be seen from the figure, Ni3(HITP)2 is in the form of nanowire, which is uniformly grown on the surface of carbon cloth, with a diameter of about 30-60nm.

[0053] Example 3

[0054] Preparation of an electrochemical sensing electrode

[0055] First step, 10mg of 2,3,6,7,10,11-hexaaminotriphenylamine (HITP) ligand was added into a flask, and 4.7mL ultrapure water and 0.3mL N,N-dimethylformamide were added into the flask, which was ultrasonically mixed to obtain a ligand solution;

[0056] Second step, under ultrasonic condition, 7mg nickel acetate was added into the ligand solution, until the nickel metal salt was completely dissolved, to obtain the reaction solution;

[0057] Third step, the activated carbon cloth (CC) prepared in Example 1 was cut into small pieces of 2.2x1.6cm, which was put into a flask, and the solution was fully contacted with the carbon cloth fiber by ultrasonic oscillation. Then 200μL ammonia was slowly added into the solution using a 1mL pipette. After the addition was completed, the flask was quickly placed in an oven for heating at 65℃ for 6h. The electrode was taken out and washed with ultrapure water, acetone and ethanol in sequence, and then dried to obtain an electrochemical sensing electrode, which was recorded as Ni3(HITP)2 / CC-0.3.

[0058] The scanning electron microscopy (SEM) image of the Ni3(HITP)2 / CC-0.3 is shown in Figure 1 (b). As can be seen from the figure, Ni3(HITP)2 is in the form of nanorod, which is uniformly distributed on the surface of carbon cloth, with a diameter of about 50-80nm.

[0059] Example 4

[0060] Preparation of an electrochemical sensing electrode

[0061] First step, 10 mg of 2,3,6,7,10,11-hexaaminotriphenylamine (HITP) ligand was added into a flask, 4.5 mL of ultrapure water and 0.5 mL of N,N-dimethylformamide were added into the flask, and the mixture was ultrasonically mixed to obtain a ligand solution;

[0062] Second step, 7 mg of nickel acetate was added into the ligand solution under ultrasonic condition, and a reaction solution was obtained after the nickel metal salt was completely dissolved;

[0063] Third step, the activated carbon cloth (CC) prepared in Example 1 was cut into small pieces with a size of 2.2*1.6 cm, which was then put into a flask and ultrasonically shaken to make the solution fully contact with the carbon cloth fibers. Then 200 μL of ammonia water was slowly added into the solution using a 1 mL pipette. After the addition was completed, the flask was quickly placed in an oven for heating at 65°C for 6 h. The electrode was taken out, washed with ultrapure water, acetone and ethanol in sequence, and then dried to obtain an electrochemical sensing electrode, which was recorded as Ni3(HITP)2 / CC-0.5.

[0064] The SEM image of Ni3(HITP)2 / CC-0.5 is shown in FIG. 8 (c), which is in a granular shape and accumulated on the surface of the carbon cloth. Figure 1

[0065] Example 5

[0066] Preparation of an electrochemical sensing electrode

[0067] First step, 10 mg of 2,3,6,7,10,11-hexaaminotriphenylamine (HITP) ligand was added into a flask, 4.5 mL of ultrapure water and 0.5 mL of N,N-dimethylformamide were added into the flask, and the mixture was ultrasonically mixed to obtain a ligand solution;

[0068] Second step, 7 mg of nickel acetate was added into the ligand solution under ultrasonic condition, and a reaction solution was obtained after the nickel metal salt was completely dissolved;

[0069] Third step, the activated carbon cloth (CC) prepared in Example 1 was cut into small pieces with a size of 2.2*1.6 cm, which was then put into a flask and ultrasonically shaken to make the solution fully contact with the carbon cloth fibers. Then 200 μL of ammonia water was slowly added into the solution using a 1 mL pipette. After the addition was completed, the flask was quickly placed in an oven for heating at 65°C for 6 h. The electrode was taken out, washed with ultrapure water, acetone and ethanol in sequence, and then dried to obtain an electrochemical sensing electrode, which was recorded as Ni3(HITP)2 / CC-0.5.

[0070] ​SEM image of Ni3(HITP)2 / CC-1 is shown below Figure 1 As shown in (d), it is piled up in irregular flakes on the surface of carbon cloth.

[0071] from Figure 1 It can be observed that the electrochemical sensing electrode Ni3(HITP)2 / CC-0.3 prepared in Example 3 exhibits excellent morphology. Further X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) analyses were performed on it. Figure 2 Here is the EDS plot of Ni3(HITP)2 / CC-0.3. Figure 2 The presence of C, N, O, and Ni is shown. The peaks of C and N mainly come from ligands, the peak of O mainly comes from small molecules such as H2O adsorbed on the surface, and the presence of Ni indicates the formation of Ni3(HITP)2 structure.

[0072] Figure 3 The XPS spectra of Ni3(HITP)2 / CC-0.3 are shown below. (a) is the full XPS spectrum of Ni3(HITP)2 / CC-0.3, from which the spin orbital peaks of C1s, N1s, O1s and Ni2P can be clearly observed. Figure 3 (b) is the fine N1s spectrum of the product, from which it can be clearly observed that the peaks at 399.2 and 400.4 eV correspond to the CN bond and Ni-N4 structure, respectively. Figure 3 (c) shows the fine Ni 2p spectrum of the product. It can be clearly observed that the peaks at 855.4 and 873.1 eV correspond to Ni(II)2p3 / 2 and Ni(II)2p1 / 2, respectively, while the peaks at 844.0 and 878.5 eV are satellite peaks. These results indicate the successful synthesis of Ni3(HITP)2 on the CC surface. The Ni ion is in the +2 valence state.

[0073] Ni3(HITP)2 / CC-0.3 was sonicated for 30 min to remove Ni3(HITP)2 from the carbon cloth surface. The powder was collected by centrifugation and washing, and analyzed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and transmission electron microscopy (TEM).

[0074] Figure 4 The XRD pattern of the powder shows that all diffraction peaks correspond to the standard simulated crystal pattern. The peaks at diffraction angles (2θ) of 4.7, 9.4, 12.4, 16.3, and 27.1 correspond to the (100), (200), (210), (201), and (001) crystal planes, respectively, indicating that the powder product is a pure phase of Ni3(HITP)2.

[0075] Figure 5The image shows the FT-IR spectrum of the powder. Three distinct peaks are observed at 3430, 1630, and 1350 cm⁻¹. -1 The three characteristic peaks at the point correspond to the absorption vibrations of the -NH group, the benzene ring skeleton, and the CN bond, respectively.

[0076] Figure 6 TEM image of the powder, from Figure 6 (a) clearly shows the lattice fringes of Ni3(HITP)2. Figure 6 As shown in (b), the calculated lattice spacing is 1.8 nm, corresponding to the (001) crystal plane of Ni3(HITP)2. Figure 6 In (c), the pore structure of Ni3(HITP)2 can be clearly observed. The large pores with a diameter of 1.8 nm effectively allow small molecules to pass through, thereby activating a large number of active sites inside the material. All of the above results indicate the successful synthesis of Ni3(HITP)2 on the CC surface.

[0077] Test case

[0078] A. Using an electrochemical workstation and a standard three-electrode system, a 0.1M hydroxide solution was selected as the electrolyte. The activated carbon cloth prepared in Example 1 and the electrochemical sensing electrodes prepared in Examples 2-5 were used as working electrodes, with a working area immersed in the electrolyte of 1 cm². 2 A platinum wire was used as the counter electrode, and an Ag / AgCl (saturated potassium chloride) electrode was used as the reference electrode. The response of the electrodes to AA was investigated by comparing the CV curves before and after adding 0.1M ascorbic acid to 0.1M NaOH solution.

[0079] Figure 7 The CV curves of different electrodes before and after the addition of AA are shown in the figure. As can be seen from the figure, the activated carbon cloth showed almost no redox peaks in the CV curves within the potential range of 0-0.7V (Vs Ag / AgCl) before and after the addition of AA, and the current intensity did not change significantly, indicating that the activated carbon cloth has no significant oxidizing ability for AA in NaOH solution. Unlike the activated carbon cloth, the four Ni3(HITP)2 / CC electrodes showed obvious redox peaks before the addition of AA, corresponding to the conversion between Ni(II) and Ni(III) in Ni3(HITP)2. After the addition of AA, the peak current value of the anolyte increased significantly. This is because AA, as a reducing agent, reduces Ni(III) in Ni3(HITP)2 to Ni(II) in solution, effectively enhancing the oxidation current. Simultaneously, it is oxidized to dehydroascorbic acid, and the catalytic process is shown in the following formula.

[0080] Ni(II)→Ni(III)+e -

[0081]

[0082] This indicates that Ni3(HITP)2 / CC can effectively catalyze the oxidation of AA, generating a significant response current. Furthermore, it can be seen that the electrochemical sensing electrode Ni3(HITP)2 / CC-0.3 prepared in Example 3 exhibits the highest response intensity.

[0083] B. The sensing capability of the electrochemical sensing electrode Ni3(HITP)2 / CC-0.3 prepared in Example 3 for AA was tested, and the method is as follows:

[0084] (1) Determine the optimal test potential

[0085] Take one electrode and first scan it using cyclic voltammetry until the signal stabilizes. Then, use the current-time curve method, running it for 100 seconds to allow the current to stabilize. After that, add 1M AA solution every 60 seconds, for a total of seven additions, to obtain the time-current curve at an initial potential of 0.5V. Take another unused electrode, change the initial potential to 0.55V, and repeat the above operation to obtain the time-current curve. The same operation is used to obtain the time-current curves at initial potentials of 0.60V and 0.65V.

[0086] like Figure 8 As shown, Figure 8 These are the time-current response curves of the electrodes after continuous addition of AA at different potentials. When the applied potential is 0.65V, Ni3(HITP)2 / CC-0.3 has the strongest response current to AA, but there is a large OER current interference in the initial state. The response intensity is high and the noise is low at 0.55V, which is the best test potential.

[0087] (2) Plotting the standard curve

[0088] Using a current-time curve, a potential of 0.55V was used. No AA was added for 0-300s, and then AA solution was added every 50s. The current value obtained at a certain concentration was recorded as I, and the current value without glucose solution was recorded as I0. I minus I0 is the sample's response current value to AA. A standard curve was plotted with the added AA concentration as the X-axis and the response current as the Y-axis.

[0089] like Figure 9 As shown, Figure 9 (a) shows the current response of the electrode after continuous addition of AA. As AA is added, the current curve shows an obvious response gradient current. Figure 9 (b) is the standard curve of the relationship between the concentration of added AA and the response current. The sensitivity is 21.36 mA·mM in the range of AA addition of 0-0.1 mM. -1 ·cm -2The detection limit is 0.25 μM (3δ / S, where δ is the standard deviation of the blank current and S is the slope of the standard curve). It exhibits a low detection limit and high sensitivity. The sensitivity is 11.91 mA·M in the range of 0.1–0.5 M. -1 ·cm -2 The sensitivity is 9.52 mA·m in the range of 0.5-3.5 M. -1 ·cm -2 .

[0090] Test results show that Ni3(HITP)2 / CC-0.3 has excellent detection performance for AA over a wide range, and is expected to serve as a high-efficiency AA sensing electrode material.

[0091] C. Anti-interference capability test

[0092] Prepare interference solutions containing glucose, urea, L-cysteine, glutathione, citric acid, melamine, and L-aspartate. Using a new electrode, scan the signal using cyclic voltammetry until it stabilizes. Utilize the current-time curve method, employing the optimal potential. Do not add AA for 0-100s; add 1 MAA at 100s; subsequently, alternately add 2M of the interference and 1 MAA to the solution every 25s.

[0093] like Figure 10 As shown, Figure 10 The current-time curves of alternating interference and AA were obtained. When AA was added, a significant current step appeared, while there was almost no response when the interference was added, indicating that the electrode has a strong anti-interference ability to sense AA.

[0094] D. Stability Testing

[0095] (a) Reproducibility of a single electrode

[0096] An electrode was placed in the air at room temperature, and its time response to a 1 MAA current was tested every five days over a period of 30 days.

[0097] (b) Reproducibility of multiple electrodes

[0098] Take five new electrodes and perform a current-time response test on a 1M AA electrode.

[0099] like Figure 11 As shown, Figure 11 (a) shows the stability of an electrode over 30 days. The results indicate that the response remains stable after a small amount of decay in the first 10 days within 30 days. Figure 11 (b) shows the parallel response of 5 identical electrodes. The results show that the response deviation is small, demonstrating good stability and reproducibility.

[0100] E. Structural stability

[0101] A piece of electrode after the above sensing test was taken and analyzed by field emission scanning electron microscope (FE-SEM). The scanning electron microscope image thereof is shown in FIG. 6, and the morphology of the nanorod after the test is kept well, indicating that it can keep good structural stability during the sensing process. Figure 12

[0102] The principles and implementations of the present application are described in the specific examples in this paper, and the above examples are only used to help understand the method of the present application and its core idea, including the best mode, and also enable any person skilled in the art to practice the present application, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application. The scope of patent protection of the present application is defined by the claims, and can include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included within the scope of the claims.

[0103] The above examples are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements will not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.​

Claims

1. A non-enzymatic ascorbic acid electrochemical sensing electrode based on Ni-HITP, characterized in that, The preparation method of the electrochemical sensing electrode comprises the following steps: The first step is to add 2,3,6,7,10,11-hexamino triphenyl ligand into a scintillation bottle, add ultrapure water and N,N-dimethylformamide into the bottle, ultrasonically mix to obtain a ligand solution; The second step is to add nickel metal salt into the ligand solution under ultrasonic condition, and after the nickel metal salt is completely dissolved, a reaction solution is obtained; The third step is to put activated carbon cloth into the scintillation bottle, ultrasonically shake, then slowly add ammonia water into the solution using a pipette, after the addition, place the scintillation bottle in an oven and heat at 60-70 DEG C for 4-8 h, discharge, take out the electrode, and then wash with ultrapure water, acetone and ethanol in sequence, and then dry to obtain the electrochemical sensing electrode; The preparation method of the activated carbon cloth comprises the following steps: Step one, cut the carbon cloth into a sample cloth with a size of 3.5 cm*4.5 cm, put it into acetone, ultrasonically treat for 10-20 min, take out, transfer to ultrapure water, ultrasonically treat for 1-2 times, each time for 10-20 min, take out, finally ultrasonically treat in ethanol for 1-2 times, each time for 10-20 min, take out, and dry in an oven at 60-70 DEG C for 8-12 h to obtain pretreated carbon cloth; Step two, add the pretreated carbon cloth into a mixed solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:1, soak at room temperature for 9-12 h, take out the carbon cloth, clean by the same washing method as step one, dry after removing the strong acid, and the activated carbon cloth is obtained.

2. The Ni-HITP based non-enzymatic ascorbic acid electrochemical sensing electrode according to claim 1, wherein, In the second step, the nickel metal salt is any one of nickel acetate, nickel chloride, nickel nitrate or nickel sulfate.

3. Use of a Ni-HITP-based non-enzymatic ascorbic acid electrochemical sensor electrode according to claim 1, characterized in that, The electrochemical sensing electrode is used as an active electrode and applied to the enzyme-free electrochemical sensing of ascorbic acid.

4. Use of a Ni-HITP-based non-enzymatic ascorbic acid electrochemical sensor electrode according to claim 3, characterized in that, The application method is as follows: Take the electrochemical sensing electrode as a working electrode, platinum wire as a counter electrode, silver / silver chloride electrode as a reference electrode, 0.1 mol / L sodium hydroxide solution as an electrolyte, use a standard three-electrode system, use an electrochemical workstation, test the presence or absence of redox peaks in the cyclic voltammogram and the change of peak position and peak value before and after adding ascorbic acid by cyclic voltammetry, and determine the response ability of the electrochemical sensing electrode to ascorbic acid.

5. Use of a Ni-HITP-based non-enzymatic ascorbic acid electrochemical sensor electrode according to claim 4, characterized in that, The specific method of the test is as follows: (1) Determine the optimal test potential Take the electrochemical sensing electrode, first scan to a stable signal using cyclic voltammetry, then use current-time curve method, run for 100 s to make the current stable, select different initial potentials, add 0.2-2 mol / L ascorbic acid solution every 20-80 s, a total of 5-10 times, obtain the time-current curve under different initial potentials, select the optimal potential for the next step; (2) Draw a standard curve Use the optimal potential, add ascorbic acid solution with different concentrations every 20-80 s to obtain the time-current curve, draw a standard curve between the concentration of added ascorbic acid solution and the corresponding current, and obtain the sensitivity, detection limit and detection range parameters.

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