A carboxylated multi-walled carbon nanotube-functionalized screen-printed electrode for detecting N3 - Method

Abstract

The application discloses a kind of based on carboxylated multi-walled carbon nanotube modified silk screen printing electrode preparation azide ion electrochemical sensor.The application uses carboxylated multi-walled carbon nanotube as modification material, acetic acid solvent, and electrode modification liquid of 2mg / mL is prepared, 2 μL is dropped on the working carbon electrode of silk screen printing electrode, and N3 ‑ Electrochemical sensor. The concentration of azide ion in the solution is detected by electrochemical analysis method, and the sensor has the advantages of easy preparation, portability, sensitivity, low price and small required detection amount.

Description

[0001] Technical Field: This invention relates to the field of electrochemical detection technology in analytical chemistry, and more particularly to a screen-printed electrode with carboxylated multi-walled carbon nanotubes for detecting N3. - The method. Background Technology

[0002] Electrochemical analysis offers advantages such as high sensitivity, real-time performance, and portability, making it highly advantageous in the detection of azide ions. Typically, electrochemical analysis is based on a three-electrode system, with interconnected circuits within an electrolytic cell to complete the detection. Some platinum and gold electrodes exhibit low sensitivity for azide ion detection. While highly boron-doped diamond (BDD) electrodes and highly oriented pyrolytic graphite (HOPG) electrodes offer high sensitivity, they are expensive and difficult to prepare. Furthermore, these electrodes require complex pretreatment processes such as polishing before operation, resulting in high costs and complex systems that are not easily portable. Compared to traditional electrodes, screen-printed electrodes offer advantages such as low cost, good stability, portability, small required detection solution volume, and simple operation.

[0003] Some blank screen-printed electrodes exhibit poor electrochemical activity due to their fabrication process or carbon paste. Modification of these electrodes is often employed to improve their detection performance. Modification of screen-printed electrodes is more convenient than that of traditional electrodes, and they are better suited for trace detection, thus showing great promise. In recent years, carboxylated multi-walled carbon nanotubes (CUVs) have been widely used as a nanomaterial in electrode modification research due to their excellent hydrophobicity, large surface area, numerous adsorption active sites, conductivity, and good potential response. Combining CUVs with screen-printed electrodes to fabricate electrochemical sensors results in more stable, highly sensitive electrochemical sensors applicable to ion detection in production processes. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a carboxylated multi-walled carbon nanotube-functionalized screen-printed electrode for detecting N3. - The proposed method optimizes the detection conditions of an electrochemical sensor and uses electrochemical analysis to detect the concentration of azide ions in solution. This detection method has advantages such as ease of preparation, portability, sensitivity, low cost, and small detection quantity.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] One objective of this invention is to provide a method for preparing an electrode modification solution, the method comprising the following steps:

[0007] Step 1: Measure 1 mL of glacial acetic acid into a 2 mL screw-top transparent sample bottle. Weigh 2 mg of carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) using an analytical balance, add them to 1 mL of glacial acetic acid, seal the bottle, shake to disperse them in the solvent, and then place it in a 100W ultrasonic cleaner for 20 minutes to ultrasonically mix. After the ultrasonic cleaner stops working, remove the bottle and store it at room temperature.

[0008] The second objective of this invention is to provide a method for screen-printing a carboxylated multi-walled carbon nanotube-functionalized electrode, the method comprising the following steps:

[0009] Step 1: Take 1 μL of the modification solution and drop it onto the working carbon electrode of the pretreated screen-printed electrode. Let it air dry naturally until the solvent evaporates (about 2 hours or more). Use deionized water to wash away the unmodified material on the electrode surface until the cyclic voltammetry curves in PBS buffer solution have similar shapes and current magnitudes. After drying completely at room temperature, it can be used for testing.

[0010] The third objective of this invention is to provide the functionalized screen-printed electrode for detecting N3. - In this application, the electrode utilizes an electrochemical detection mechanism to detect N3 in solution. - After electrochemical oxidation, an oxidation peak appears at the oxidation potential, i.e., as N3 increases... - Increased concentration leads to an enhanced oxidation peak response current, thereby achieving control over N3. - The detection.

[0011] Compared with the prior art, the present invention has the following advantages and effects:

[0012] 1. The present invention provides a method for detecting N3. - An electrochemical sensor that is sensitive to N3 - The detection method is simple, fast, and portable, making it promising for applications in various fields such as national defense, biology, medicine, and the environment. The electrochemical oxidation of azide ions on a screen-printed electrode is a diffusion-controlled and irreversible process. This electrochemical sensor converts the azide ion concentration into an electrical signal, offering fast detection speed, high sensitivity, and strong practicality.

[0013] 2. This invention provides a carboxylated multi-walled carbon nanotube functionalized screen-printed electrode for detecting N3. - The method contains N3 - The solution undergoes electrochemical oxidation on a screen-printed electrode functionalized with carboxylated multi-walled carbon nanotubes, N3 - The higher the concentration, the greater the electrochemical response current, thus achieving the effect of N3 - The quantitative detection of concentration has a low detection limit and a wide detection range, which greatly improves its effectiveness.

[0014] 3. The present invention provides a method for detecting N3. - The electrochemical sensor has a simple preparation process, low cost, and good reproducibility, stability and selectivity. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the fabrication process of the carboxylated multi-walled carbon nanotube functionalized screen-printed electrode provided in Example 1 of the present invention.

[0016] Figure 2 This is a scanning electron microscope image of the carboxylated multi-walled carbon nanotube functionalized screen-printed electrode provided in Example 1 of the present invention.

[0017] Figure 3 The carboxylated multi-walled carbon nanotube functionalized screen-printed electrode provided in Example 2 of this invention is used for detecting N3. - Electrochemical behavior characterization diagram;

[0018] Figure 4 The carboxylated multi-walled carbon nanotube functionalized screen-printed electrode provided in Example 2 of this invention was used to detect N3 at different scan rates. - Cyclic voltammetry curve;

[0019] Figure 5 The carboxylated multi-walled carbon nanotube functionalized screen-printed electrode provided in Example 2 of this invention was used to detect N3 at different scan rates. - The relationship between response current and scanning speed;

[0020] Figure 6 This is an optimization diagram of the bottom solution pH value of the screen-printed electrode with carboxylated multi-walled carbon nanotubes provided in Example 2 of the present invention.

[0021] Figure 7 The carboxylated multi-walled carbon nanotube functionalized screen-printed electrode provided in Example 3 of this invention is used to detect different concentrations of N3. - Electrochemical response diagram;

[0022] Figure 8 The carboxylated multi-walled carbon nanotube functionalized screen-printed electrode provided in Example 3 of this invention is used to detect different concentrations of N3. - The fitting plot of the DPV oxidation peak response current versus concentration change.

[0023] Figure 9 This is a reproducibility diagram of the carboxylated multi-walled carbon nanotube functionalized screen-printed electrode provided in Example 4 of the present invention.

[0024] Figure 10 This is a stability diagram of the carboxylated multi-walled carbon nanotube functionalized screen-printed electrode provided in Example 4 of the present invention.

[0025] Figure 11 This is a selectivity diagram of the carboxylated multi-walled carbon nanotube functionalized screen-printed electrode provided in Example 4 of the present invention. Detailed Implementation

[0026] The present invention is implemented through the following embodiments, but the conditions and results described in the implementation do not constitute a limitation on the content and rights of the invention.

[0027] Example 1: Carboxylated multi-walled carbon nanotube functionalized screen-printed electrode

[0028] I. Preparation of screen-printed electrodes functionalized with carboxylated multi-walled carbon nanotubes

[0029] 1. Pretreatment of screen-printed electrodes:

[0030] 100 μL of 0.1 M PBS (pH = 7.5) was dropped onto the screen-printed electrode and cyclic voltammetry was performed (parameter settings: potential scan range -0.5 V to 1.5 V, scan rate 100 mV / s, number of scan segments 40). The electrode was then allowed to air dry after scanning.

[0031] 2. Preparation of carboxylated multi-walled carbon nanotube modification solution:

[0032] Measure 1 mL of glacial acetic acid into a 2 mL screw-top transparent sample bottle. Weigh 2 mg of carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) using an analytical balance, add them to 1 mL of glacial acetic acid, seal the bottle, shake to disperse them in the solvent, and then place it in a 100W ultrasonic cleaner for 20 minutes to ultrasonically mix. After the ultrasonic cleaner stops working, remove the bottle and store it at room temperature.

[0033] 3. Preparation of screen-printed electrodes functionalized with carboxylated multi-walled carbon nanotubes:

[0034] The working electrode was modified by drop coating. 1 μL of the modification solution was dropped onto the working carbon electrode of the pretreated screen-printed electrode and allowed to air dry naturally until the solvent evaporated (about 2 hours or more). The electrode surface was washed with deionized water until the unmodified material was removed. The cyclic voltammetry curves in PBS buffer solution were similar in shape and current magnitude. After being completely dried at room temperature, the electrode was used for testing.

[0035] The fabrication process of carboxylated multi-walled carbon nanotube functionalized screen-printed electrodes is as follows: Figure 1 As shown.

[0036] II. Morphological Characterization of Carboxylated Multi-Walled Carbon Nanotube Functionalized Screen-Printed Electrodes

[0037] 1. Characterization by scanning electron microscopy (SEM), such as... Figure 2As shown, it can be observed that the surface roughness of the electrode modified with carboxylated carbon nanotubes has a slight change compared to the unmodified screen-printed electrode, indicating that the nanomaterial has been modified onto the surface of the working electrode, and the modified electrode surface has obvious cracks and a larger specific surface area.

[0038] Example 2: Carboxylated multi-walled carbon nanotube functionalized screen-printed electrode in N3 - Electrochemical characterization in solution

[0039] Take the carboxylated multi-walled carbon nanotube functionalized screen-printed electrode prepared in Example 1, and drop 100 μL of N3 containing 10 mM N3 onto the electrode sheet. - pH 7.5 PBS buffer solution with N3-free - Cyclic voltammetry was performed using a pH 7.5 PBS buffer solution, as shown in the figure. Figure 3 As shown in the figure, a distinct oxidation peak appears, but no reduction peak is observed, indicating that the electrochemical reaction is irreversible. Furthermore, the reaction of MWCNTs-COOH / SPE at pH 7.5 containing 1 mmol / L N3 was tested at different scan rates. - The cyclic voltammetry curves in PBS buffer solution showed that with increasing scan rate (20, 40, 60, 80, and 100 mV / s from bottom to top), the oxidation peak current increased, and the oxidation peak potential shifted positively. Figure 4 As shown. By Figure 4 Provide data to plot the relationship between oxidation peak current and scan rate, such as Figure 5 As shown, within the scan rate range of 20–100 mV / s, the oxidation peak current is linearly correlated with the square root of the scan rate, and the correlation coefficient is above 0.99, indicating a good linear relationship. This suggests that the electrochemical oxidation of azide ions on the screen-printed electrode is a diffusion-controlled process.

[0040] N3 - The electrochemical sensor exhibits varying stability at different pH values, and the pH range of its future operating environment is also specific. To optimize the sensor's detection of azide ions, the pH of the testing environment was optimized. The electrochemical response of the MWCNTs-COOH / SPE electrode to azide ions was tested within a pH range of 6–11. Figure 6As shown, the modified electrode activity exhibits a trend of first increasing and then decreasing with increasing pH. Between pH 6 and 7.5, the oxidation peak response current increases with increasing pH; however, within the pH range of 7.5 to 11, the oxidation peak response current decreases with increasing pH. Therefore, it can be seen that the MWCNTs-COOH / SPE electrode performs best in detecting azide ions at pH 7.5. This phenomenon of first increasing and then decreasing may be because azides are more likely to exist in proton form at low pH environments, making oxidation difficult. In strongly alkaline environments, the decrease in response current may be due to competition between hydroxide ions and azide ions, resulting in detection interference.

[0041] Example 3: Screen-printed electrodes with carboxylated multi-walled carbon nanotubes functionalized at different N3 concentrations - Response current in solution

[0042] The carboxylated multi-walled carbon nanotube functionalized screen-printed electrode prepared in Example 1, and the optimal detection pH value of 7.5 from Example 2, were tested at 5 × 10⁻⁶. -5 ~1×10 -3 The DPV current response curve of the electrochemical sensor within the mol / L azide ion concentration range is shown in the figure below. Figure 7 As shown. The relationship between the sensor's response current and azide ion concentration was obtained through data fitting, as shown below. Figure 8 As shown, the linear relationship is: y = 0.01283x + 4.8119, and the correlation coefficient R0 2 =0.9927, sensitivity is 12.83 μA / mM. According to the limit of detection formula LOD = 3σ / S (where σ is the relative standard deviation of the blank sample response 0.0446; S is the sensitivity), the detection limit of this electrochemical sensor for azide ions is calculated to be 10.4 μM.

[0043] Example 4: Carboxylated multi-walled carbon nanotube functionalized screen-printed electrode pair for N3 detection - Performance evaluation

[0044] The reproducibility, stability and selectivity of the electrochemical sensor were tested using the carboxylated multi-walled carbon nanotube functionalized screen-printed electrode prepared in Example 1 and the optimal detection pH value of 7.5 in Example 2.

[0045] To evaluate the reproducibility of the functionalized screen-printed electrode, 1 mmol / L N3 in an environment with a pH of 7.5 was used. - As a standardized detection concentration, the current response of eight screen-printed electrodes purchased from the same batch, after being modified with the same material, was tested. The test results are as follows: Figure 9As shown, the oxidation peak current of the eight electrodes was around 18.7 μA. The calculated relative deviation of the eight sets of response currents was 3.3%, and the human error within the same batch was within an acceptable range. This indicates that the functionalized screen-printed electrode electrochemical sensor has good reproducibility.

[0046] To evaluate N3 - To test the stability of the electrochemical sensor, four prepared electrodes were placed in a sealed bag and stored in a refrigerator at 4°C. One electrode was removed every two days for performance testing. The test solution was also 1 mmol / L N3. - The stability of the pH 7.5 phosphate buffer solution was evaluated by detecting the oxidation peak response current signal of the electrochemical sensor after storage for 2, 4, 6, and 8 days. The test results are as follows: Figure 10 As shown in the figure. The data in the figure shows that N3 - The electrochemical sensor was stored in a refrigerator at 4°C for 8 days, and its response current to azide ions did not change significantly, with the relative standard deviation remaining within 10%. This indicates that N3 - Electrochemical sensors have good long-term storage capabilities.

[0047] Verification of the effect of N3 in the presence of fluoride, chloride, nitrate and phosphate anions - Interference detected by the electrochemical sensor. Tests were conducted at pH 7.5 using 1 mM N3. - respectively with 10mM F - 10mM Cl - 10mM NO3 - The current response when coexisting with 0.1M PBS, and the selectivity test results of the electrochemical sensor are as follows: Figure 11 As shown in the figure, the data indicates that adding excessive interfering ions did not significantly alter the sensor's detection response to azide ions. The calculated relative standard deviation for the four groups was 3.9%, which is within acceptable limits. Furthermore, when only interfering ions were present in the detection solution, and no azide ions were added, the electrochemical sensor did not produce an oxidation peak during cyclic voltammetry scanning. The resulting baseline background current also differed significantly from the response current when azide ions were present. This demonstrates that the presence of fluoride, chloride, and nitrate ions has negligible interference with the detection of azide ions.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A screen-printed electrode for detecting N3 based on carboxylated multi-walled carbon nanotubes. - The method is characterized by, Includes the following steps: Step 1: Preparation of carboxylated multi-walled carbon nanotube modification solution: Measure 1 mL of glacial acetic acid into a 2 mL screw-top transparent sample bottle. Weigh 2 mg of carboxylated multi-walled carbon nanotubes using an analytical balance, add them to 1 mL of glacial acetic acid, seal the bottle, shake to disperse them in the solvent, and then place it in a 100W ultrasonic cleaner for 20 minutes to ultrasonically mix. After the ultrasonic cleaner stops working, remove the bottle and store it at room temperature. Step 2: Preparation of carboxylated multi-walled carbon nanotube functionalized screen-printed electrode: Take 2 μL of the modification solution described in Step 1 and drop it onto the working carbon electrode of the pretreated screen-printed electrode. Let it air dry naturally until the solvent evaporates. Use deionized water to wash the unmodified material on the electrode surface until the cyclic voltammetry curves in PBS buffer solution have similar shapes and current magnitudes. After drying completely at room temperature, it can be used for testing. Step 3: Functionalization of N3-based screen-printed electrodes with carboxylated multi-walled carbon nanotubes - Detection: Using the electrode described in step two, the electrode containing N3 - Cyclic voltammetry characterization was performed on the solution to analyze its electrochemical behavior and determine the N3. - Optimal detection conditions; detection of different concentrations of N3 by differential pulse voltammetry. - Establish the standard curve equation.

2. The method for detecting N3 based on a carboxylated multi-walled carbon nanotube functionalized screen-printed electrode according to claim 1. - The method is characterized by: 100 μL of N3 containing 10 mM was dropped onto the electrode. - pH 7.5 PBS buffer solution with N3-free - Cyclic voltammetry was performed using a pH 7.5 PBS buffer solution to characterize the redox peaks; the electrode was tested at different scan rates in a pH 7.5 solution containing 1 mmol / L N3. - Cyclic voltammetry curves in PBS buffer solution were analyzed by fitting the square root relationship between the oxidation peak current and the scan rate to determine N3. - Oxidation process on the electrode.

3. The N3 detection method based on carboxylated multi-walled carbon nanotube functionalized screen-printed electrode according to claim 1 - The method is characterized by: The electrode was tested for its resistance to N3 in the pH range of 6–11. - The electrochemical response was analyzed, and the optimal detection conditions were determined by observing the trend of peak current changes at different pH values.

4. The N3 detection method based on carboxylated multi-walled carbon nanotube functionalized screen-printed electrode according to claim 1 - The method is characterized by: The electrode was tested at 5 × 10 -5 ~1×10 -3 mol / L N3 - The DPV current response curve within the concentration range, with N3 - The relationship between concentration and oxidation peak response current was fitted to obtain N3. - Equation of the standard curve for detection and calculation of N3 - Detection limit.

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