An ascorbic acid electrochemical sensor based on poly-o-phenylenediamine micromaterials and its application

Abstract

The present invention discloses an ascorbic acid electrochemical sensor based on poly(o-phenylenediamine) micromaterials and its application, belonging to the technical field of electrochemical sensing. The present invention adopts a chemical oxidation method to synthesize poly(o-phenylenediamine) micromaterials with different morphologies by screening the types of oxidants and regulating parameters such as the NaCl concentration, which can significantly enhance their interaction with ascorbic acid. By using the prepared poly(o-phenylenediamine) micromaterials to modify the electrochemical sensor, the detection sensitivity and selectivity of the electrochemical sensor for ascorbic acid can be improved, providing a new rapid, efficient and low-cost ascorbic acid detection technology for clinical and laboratory applications.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical sensing, and particularly relates to an ascorbic acid electrochemical sensor based on poly(o - phenylenediamine) micromaterials and its application. Background Art

[0002] Ascorbic acid (vitamin C) is an essential water - soluble vitamin for the human body, widely present in various foods and organisms, and has important physiological functions such as antioxidant and promoting collagen synthesis. In clinical medicine, food industry and biochemical research, the accurate determination of ascorbic acid is of great significance. Traditional ascorbic acid detection methods such as high - performance liquid chromatography (HPLC), although having high accuracy, usually involve expensive equipment and complex operations, and are not suitable for rapid detection and on - site applications.

[0003] Currently, the rapid detection technologies on the market still face the problems of insufficient sensitivity and selectivity. For example, spectroscopic methods and titration methods are easily affected by the color and turbidity of samples, while electrochemical sensors, although having the advantages of simple operation and low cost, the existing material systems often cannot meet the requirements of both high sensitivity and high selectivity at the same time.

[0004] As an important derivative of the conductive polymer polyaniline, poly(o - phenylenediamine) contains more amino (-NH2) and imino (=NH) active functional groups on its molecular chain. These functional groups can form hydrogen bonds with the hydroxyl (-OH) and carboxyl (-COOH) groups in ascorbic acid molecules. The formation of these hydrogen bonds enhances the selective adsorption of poly(o - phenylenediamine) to ascorbic acid, enabling it to selectively recognize ascorbic acid molecules.

[0005] In addition, poly(o - phenylenediamine) is used for selectively recognizing ascorbic acid molecules through its unique porous structure and high surface area. These structural features provide a large number of electrochemically active sites for the oxidation reaction of ascorbic acid molecules, enabling them to be effectively captured and recognized. Poly(o - phenylenediamine) has good electrical conductivity, which can achieve ultrasensitive detection of ascorbic acid molecules. On the electrode surface, ascorbic acid easily undergoes an oxidation reaction, generating a characteristic current peak. The electrode modified with poly(o - phenylenediamine) can significantly amplify this current change, thereby improving the detection sensitivity. By controlling the preparation conditions, the obtained cluster - shaped poly(o - phenylenediamine) can increase its effective contact area with ascorbic acid molecules. This structure further enhances the electrochemical activity and detection sensitivity of the electrode, enabling it to detect ascorbic acid more accurately and sensitively.

[0006] Although poly-o-phenylenediamine has been studied for use in electrochemical sensors, most of the research has focused on its homogeneous form, overlooking the potential to optimize performance by controlling its microstructure. Therefore, developing a new type of electrochemical sensor based on structurally controllable poly-o-phenylenediamine micromaterials for efficient and accurate detection of ascorbic acid is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The purpose of the present invention is to provide an ascorbic acid electrochemical sensor based on poly-o-phenylenediamine micromaterials and its application.

[0008] To achieve the above purpose, the present invention provides the following technical solutions:

[0009] One of the technical solutions of the present invention: Provide a preparation method of poly-o-phenylenediamine micromaterials, including the following steps:

[0010] Dissolve o-phenylenediamine in deoxygenated water to prepare an o-phenylenediamine solution with a concentration of 0.1 mol / L; take the prepared o-phenylenediamine solution, mix it with NaCl solution and diluent, shake well, add an oxidant solution, and let it stand for reaction to obtain cluster-shaped, micron-banded or plate-shaped poly-o-phenylenediamine micromaterials;

[0011] When the prepared poly-o-phenylenediamine micromaterials are cluster-shaped, the diluent is water, the oxidant solution is 0.5 mol / L CuCl2 solution, the concentration of the NaCl solution is 3.09 mol / L, and the volume ratio of the o-phenylenediamine solution, NaCl solution, diluent and oxidant solution is 0.5:1:1:0.5;

[0012] When the prepared poly-o-phenylenediamine micromaterials are micron-banded, the diluent is water, the oxidant solution is 0.5 mol / L CuCl2 solution, the concentration of the NaCl solution is 6.18 mol / L, and the volume ratio of the o-phenylenediamine solution, NaCl solution, diluent and oxidant solution is 0.5:1:1:0.5;

[0013] When the prepared poly-o-phenylenediamine micromaterials are plate-shaped, the diluent is 0.12 mol / L HCl solution, the oxidant solution is 30 wt.% H2O2 solution, the concentration of the NaCl solution is 6.18 mol / L, and the volume ratio of the o-phenylenediamine solution, NaCl solution, diluent and oxidant solution is 0.5:0.5:1:0.5.

[0014] Preferably, the deoxygenated water is prepared by introducing N2 into water.

[0015] Preferably, the standing reaction is specifically to stand for 15 min and then continue the reaction for 12 h.

[0016] Preferably, after the static reaction, a separation step is further included. The separation step specifically includes centrifuging the reaction system after the static reaction, removing the supernatant, repeating washing with water, centrifuging to remove water, and finally drying to obtain the poly(o-phenylenediamine) micro-material.

[0017] The second technical solution of the present invention provides a poly(o-phenylenediamine) micro-material prepared according to the above preparation method of the poly(o-phenylenediamine) micro-material.

[0018] The third technical solution of the present invention: provides an ascorbic acid electrochemical sensor based on the above poly(o-phenylenediamine) micro-material. The working electrode surface of the ascorbic acid electrochemical sensor is coated with the poly(o-phenylenediamine) micro-material.

[0019] The fourth technical solution of the present invention: provides an application of the above ascorbic acid electrochemical sensor in detecting ascorbic acid.

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

[0021] The present invention uses a chemical oxidation method. By screening the types of oxidants and regulating parameters such as the NaCl concentration, poly(o-phenylenediamine) micro-materials with different morphologies are synthesized, which can significantly enhance their interaction with ascorbic acid. Using the prepared poly(o-phenylenediamine) micro-materials to modify the electrochemical sensor can improve the detection sensitivity and selectivity of the electrochemical sensor to ascorbic acid, providing a new rapid, efficient and low-cost ascorbic acid detection technology for clinical and laboratory.

[0022] The results of electrochemical tests show that the electrode modified with cluster-like poly(o-phenylenediamine) prepared can achieve the detection of ultra-low concentration ascorbic acid molecules, and the detection limit can reach 0.1 nM in an ultrapure water environment, indicating that the ascorbic acid sensor has high sensitivity. Using low-cost poly(o-phenylenediamine) materials, ascorbic acid can be simply and sensitively detected in the nM range. Description of the Drawings

[0023] Figure 1 SEM images and infrared spectra of the poly(o-phenylenediamine) materials prepared in Examples 1-3. Among them, a is the SEM image of the cluster-like poly(o-phenylenediamine) material prepared in Example 1, b is the SEM image of the micro-ribbon-like poly(o-phenylenediamine) material prepared in Example 2, c is the SEM image of the plate-like poly(o-phenylenediamine) material prepared in Example 3, and d is the infrared spectrum of the poly(o-phenylenediamine) materials prepared in Examples 1-3.

[0024] Figure 2 It is the structural diagram of the ascorbic acid electrochemical sensor prepared with cluster-like poly(o-phenylenediamine) as the electrode material in Example 4.

[0025] Figure 3Cyclic voltammetry (CV) test curves of three ascorbic acid electrochemical sensors prepared in Example 4 for 1 mM ascorbic acid. Among them, a is the electrochemical sensor coated with cluster-like poly-o-phenylenediamine, b is the electrochemical sensor coated with micron-ribbon-like poly-o-phenylenediamine, and c is the electrochemical sensor coated with plate-like poly-o-phenylenediamine.

[0026] Figure 4 Chronocurrent response results of three ascorbic acid electrochemical sensors prepared in Example 4 to ascorbic acid. Among them, a is the electrochemical sensor coated with cluster-like poly-o-phenylenediamine, b is the electrochemical sensor coated with micron-ribbon-like poly-o-phenylenediamine, and c is the electrochemical sensor coated with plate-like poly-o-phenylenediamine.

[0027] Figure 5 Chronocurrent response results of the electrochemical sensor coated with cluster-like poly-o-phenylenediamine prepared in Example 4 to different concentrations of ascorbic acid below 10 nM.

[0028] Figure 6 Chronocurrent response results of the electrochemical sensor coated with cluster-like poly-o-phenylenediamine prepared in Example 4 to 0.1 nM ascorbic acid. Detailed implementation manners

[0029] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention. It should be understood that the terms described in the present invention are only used to describe specific implementation manners and are not used to limit the present invention.

[0030] In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0031] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention.

[0032] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, that is, they are meant to include but not limited to.

[0033] Example 1

[0034] Preparation of cluster-like poly-o-phenylenediamine material:

[0035] (1) Take one 50 mL brown glass bottle, add 10 mL of deionized water into the brown glass bottle at room temperature, and continuously pass high-purity N2 (99.999%) gas into it for 30 min to remove all the oxygen in the water;

[0036] (2) Weigh 0.108 g of o-phenylenediamine monomer at room temperature, quickly add it into the brown glass bottle and mix it with water, seal it, and use a magnetic stirrer to stir it at a constant temperature until it is completely dissolved to obtain a colorless and transparent liquid. The resulting solution is 0.1 mol / L o-phenylenediamine;

[0037] (3) Seal the bottle with tin foil paper, store the resulting solution at a low temperature of 3 °C, and ensure that the solution is used up within 20 minutes before use;

[0038] (4) Take 0.5 mL of 0.1 mol / L o-phenylenediamine solution, add 1 mL of 3.09 mol / L NaCl solution and 1 mL of deionized water, shake well, and quickly add 0.5 mL of 0.5 mol / L CuCl2 solution. It is observed that the color of the solution quickly changes from blue to dark green;

[0039] (5) Let it stand for 15 minutes. It is observed that a large amount of dark green precipitate appears in the solution. Continue to react for 12 hours to make the reaction complete. Set the centrifuge speed to 5000 r / min, centrifuge for 10 minutes to remove the supernatant, retain the precipitate at the bottom, repeat washing the precipitate with deionized water three times, and finally dry it in a vacuum drying oven at 50 °C to obtain cluster-like poly-o-phenylenediamine.

[0040] Example 2

[0041] Preparation of microstrip poly-o-phenylenediamine material:

[0042] The difference from Example 1 is that in step (4), 1 mL of 3.09 mol / L NaCl solution is changed to 1 mL of 6.18 mol / L saturated NaCl solution, and the color of the formed precipitate is brown.

[0043] Example 3

[0044] Preparation of plate-like poly-o-phenylenediamine material:

[0045] The difference from Example 1 is that in step (4), 1 mL of 3.09 mol / L NaCl solution, 1 mL of deionized water, and 0.5 mL of 0.5 mol / L CuCl2 solution are changed to 0.5 mL of 6.18 mol / L saturated NaCl solution, 1 mL of 0.12 mol / L HCl solution, and 0.5 mL of 30 wt.% H2O2 solution, and the color of the formed precipitate is brown.

[0046] SEM images and infrared spectra of the poly(o-phenylenediamine) materials prepared in Examples 1-3 are shown in Figure 1 , where a is the SEM image of the clustered poly(o-phenylenediamine) material prepared in Example 1, b is the SEM image of the micron-ribbon poly(o-phenylenediamine) material prepared in Example 2, c is the SEM image of the plate-like poly(o-phenylenediamine) material prepared in Example 3, and d is the infrared spectrum of the poly(o-phenylenediamine) materials prepared in Examples 1-3.

[0047] In Example 1, using CuCl2 as the oxidant, a certain amount of o-phenylenediamine monomer and NaCl solution were mixed. As the Cu 2+ was reduced, the self-assembly of poly(o-phenylenediamine) oligomers occurred, forming a clustered poly(o-phenylenediamine) structure.

[0048] Compared with Example 1, in Example 2, by increasing the NaCl concentration, the electrostatic repulsion of poly(o-phenylenediamine) oligomers was increased, hindering the self-assembly process, and forming a micron-ribbon poly(o-phenylenediamine) structure.

[0049] In Example 3, using H2O2 as the oxidant, a plate-like poly(o-phenylenediamine) structure was formed.

[0050] As Figure 1 shown in d, the infrared peak at 1237 cm -1 is caused by the stretching vibration of the benzene-ring type C-N bond, the infrared peak at 1367 cm -1 is caused by the stretching vibration of the quinone-ring type C-N bond, the peak at 1673 cm -1 is the vibration peak of C=N in the phenazine ring, and the infrared peaks at 3176 cm -1 and 3356 cm -1 are caused by the N-H stretching vibration in NH2 and the N-H stretching vibration in NH, respectively. During the polymerization of o-phenylenediamine molecules, after the -NH2 on the o-phenylenediamine molecules is oxidized, two active sites are formed, and then through the mutual collision and contact between molecules, a phenazine-like structure is gradually formed. As the reaction time prolongs, the molecular weight gradually increases, generating a poly(o-phenylenediamine) structure with a higher degree of polymerization. The appearance of the above characteristic peaks indicates that the formed polymer contains a phenazine ring structure, confirming the formation of poly(o-phenylenediamine).

[0051] Example 4

[0052] Preparation of ascorbic acid electrochemical sensors based on the poly(o-phenylenediamine) micron materials of Examples 1-3:

[0053] (1) Respectively take 8 mg of the clustered, micron-ribbon, and plate-like poly(o-phenylenediamine) powders prepared in Example 1, Example 2, and Example 3 and dissolve them in 200 μL of water. After ultrasonic treatment at 150 W for 30 min, inks A, B, and C are obtained;

[0054] (2) Use a screen printing machine to print conductive silver paste on a polyimide substrate as the electrode lead, and dry it at room temperature for 24 h to obtain the electrode lead layer;

[0055] (3) Use carbon paste to print the working electrode and the counter electrode on the polyimide substrate, and dry it at room temperature for 24 h to obtain the working electrode layer and the counter electrode layer;

[0056] (4) Use silver / silver chloride paste to print the reference electrode on the polyimide substrate, and dry it at room temperature for 24 h to obtain the reference electrode layer;

[0057] (5) Uniformly coat inks A, B, and C on the surface of the working electrode respectively. After drying at room temperature, an ascorbic acid electrochemical sensor is obtained. The structural diagram of the ascorbic acid electrochemical sensor prepared with cluster-like poly-o-phenylenediamine as the electrode material is shown in Figure 2 .

[0058] Example 5

[0059] Application of the three ascorbic acid electrochemical sensors prepared in Example 4 in the detection of ascorbic acid:

[0060] (1) Prepare a test solution (PBS buffer solution) containing a supporting electrolyte, and add ascorbic acid with a known concentration;

[0061] (2) Immerse the modified electrode into the test solution containing ascorbic acid, and perform cyclic voltammetry scanning using an electrochemical workstation. Set the scanning potential range from -0.6 V to 0.6 V, and the scanning rate is 50 mV / s. Record the current-voltage curve, and observe the oxidation peak and reduction peak of ascorbic acid at a specific potential;

[0062] (3) Use chronoamperometry to measure the current response signals of ascorbic acid at different concentrations. Apply a fixed potential (ascorbic acid oxidation peak potential, 0.4 V), and measure the curve of current changing with time at the fixed potential. According to the change of the current peak value, calculate the concentration of ascorbic acid in the solution, and optimize the performance of the sensor by adjusting the electrode parameters and test conditions.

[0063] The cyclic voltammetry (CV) test curves of the three ascorbic acid electrochemical sensors prepared in Example 4 for 1 mM ascorbic acid are shown in Figure 3 , where a is the electrochemical sensor coated with cluster-like poly-o-phenylenediamine, b is the electrochemical sensor coated with microstrip-like poly-o-phenylenediamine, and c is the electrochemical sensor coated with plate-like poly-o-phenylenediamine. Figure 3It shows that in the presence of ascorbic acid molecules, the current responses of poly(o-phenylenediamine) with three morphologies gradually increase starting from 0.4 V, proving that poly(o-phenylenediamine) has an electrochemical response to ascorbic acid molecules. According to the CV test results, 0.6 V is selected as the working voltage of the sensing electrode to detect ascorbic acid at different concentrations.

[0064] Figure 4 Figure 4 shows the chronoamperometric response results of three ascorbic acid electrochemical sensors prepared in Example 4 for ascorbic acid. Among them, a is the electrochemical sensor coated with cluster-like poly(o-phenylenediamine), b is the electrochemical sensor coated with micron-ribbon-like poly(o-phenylenediamine), and c is the electrochemical sensor coated with plate-like poly(o-phenylenediamine). By comparing the current response results of materials with different morphologies to a 10 nM ascorbic acid solution, it is concluded that cluster-like poly(o-phenylenediamine) has a relatively high current response value to ascorbic acid molecules.

[0065] Figure 5 Figure 8 shows the chronoamperometric response results of the electrochemical sensor coated with cluster-like poly(o-phenylenediamine) for different concentrations of ascorbic acid below 10 nM. When detecting low-concentration ascorbic acid, the inventors found that complex ions in the electrolyte solution would affect the selective adsorption of ascorbic acid molecules on the electrode surface, making it difficult to achieve ultra-low concentration detection. For the detection of ultra-low concentration ascorbic acid, the present invention directly dilutes the ascorbic acid solution in deionized water and prepares solutions of 0.5 nM, 1 nM, and 10 nM for chronoamperometric detection. From Figure 5 As can be seen from Figure 10, using cluster-like poly(o-phenylenediamine) as the electrode material to detect different concentrations of ascorbic acid solutions below 10 nM, obvious current response signals appear, and as the concentration of ascorbic acid increases, the current response signals also gradually increase. By comparing different curves, it can be seen that the prepared cluster-like poly(o-phenylenediamine) electrode can achieve the detection of 0.5 nM ascorbic acid in a pure water environment.

[0066] Figure 6 Figure 14 shows the chronoamperometric response results of the electrochemical sensor coated with cluster-like poly(o-phenylenediamine) for 0.1 nM ascorbic acid. The electrochemical test results show that the electrode modified with cluster-like poly(o-phenylenediamine) can achieve the detection of ultra-low concentration ascorbic acid molecules, and the detection limit can reach 0.1 nM in an ultrapure water environment. In addition, the ultra-low detection limit indicates that the ascorbic acid sensor has high sensitivity, and the low-cost poly(o-phenylenediamine) material can simply and sensitively detect ascorbic acid in the nM range.

[0067] The above-described embodiments are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention should fall within the protection scope determined by the claims of the present invention.

Claims

1. An application of an ascorbic acid electrochemical sensor in detecting ascorbic acid, characterized in that: The surface of the working electrode of the ascorbic acid electrochemical sensor is coated with a clustered poly-o-phenylenediamine micron material; The steps for preparing the clustered poly-o-phenylenediamine micron material include: The o-phenylenediamine solution with a concentration of 0.1 mol / L is prepared by dissolving o-phenylenediamine in water from which oxygen has been removed; the prepared o-phenylenediamine solution is mixed with a NaCl solution and a diluent, and after being shaken well, an oxidant solution is added, and the mixture is allowed to react to obtain a clustered poly-o-phenylenediamine micron material; The diluent is water, the oxidant solution is a 0.5 mol / L CuCl2 solution, the concentration of the NaCl solution is 3.09 mol / L, and the volume ratio of the o-phenylenediamine solution, the NaCl solution, the diluent and the oxidant solution is 0.5:1:1:0.5.

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