An integrated microneedle electrode for chloride ion detection in pore water stock solution

Abstract

This invention discloses an integrated microneedle electrode for detecting chloride ions in porous water. The preparation method of the integrated microneedle electrode includes the preparation of a working electrode (AgCl / AgNPs / e-ANE) and a fishbone-shaped Ag / AgCl reference electrode. The fishbone-shaped Ag / AgCl reference electrode is then wound around the insulating layer surface of the working electrode (AgCl / AgNPs / e-ANE). This integrated two-electrode microneedle electrode achieves low-cost construction of a chloride ion microelectrode, enabling accurate detection of chloride ions in marine porous water. It demonstrates the application potential of this sensing system for long-term, on-site monitoring of chloride ions in marine porous water, and provides a reliable method for understanding the role of chloride ions in the environment.

Description

Technical Field

[0001] This invention relates to the field of electrochemical sensors, specifically to an integrated microneedle electrode for detecting chloride ions in porous water stock solutions. Background Technology

[0002] Chloride ions (Cl) - As an important indicator for water quality monitoring, the content and distribution of Cl- are of great significance for assessing the degree of marine pollution and monitoring the migration and transformation processes of pollutants, especially in some extreme environments. Currently, numerous methods for detecting Cl- have been developed based on different principles. - The detection technology is available, but it is limited by factors such as operation method, equipment size, and cost, and its application in different scenarios is limited to Cl. - In-situ monitoring to obtain continuous data suitable for analysis remains challenging. Current methods for monitoring Cl in the environment (such as coastal observation stations) and large-scale marine engineering projects are also problematic. - For both on-site detection and long-term monitoring, a particularly large number of detection points are required to obtain sufficiently rich data. This necessitates further reductions in sensor cost and demands high electrode stability to minimize maintenance and replacement frequency, thereby achieving continuous detection and monitoring data. In addition, the sensors should have a small size for easy embedding or placement in pores for Cl... - The determination of Cl. Currently widely used traditional electrodes such as GCE, SPE, and commercial metal electrodes have shortcomings in terms of size, cost, and stability, making it difficult to meet the actual needs of large-scale field detection and monitoring. Therefore, there is an urgent need for a cheaper and more stable substrate for the development of Cl. - An electrochemical micro-detection (monitoring) platform is being developed to enable large-scale on-site detection and long-term monitoring applications.

[0003] As a precise and highly sensitive detection tool, microelectrodes enable the quantitative measurement of minute chemical and biological processes in small-scale, specialized environments. Currently, researchers have made some progress in the development of microelectrodes. Acupuncture needle electrodes (ANEs) exhibit good stability in long-term monitoring and high-humidity environments, and are relatively inexpensive (e.g., a single Huatuo brand stainless steel acupuncture needle ZJ874 from Suzhou Medical Supplies Factory Co., Ltd. costs 0.26 yuan). They offer significant advantages in large-scale deployment monitoring. Furthermore, the flexible needle structure of ANEs allows for on-site detection of environmental markers, especially for analyzing the content of target substances in special environments such as pore water in sediments.

[0004] However, due to the smooth surface of ANEs, modifying materials cannot adhere firmly to their surface, which affects the quality and stability of the modified layer. Therefore, when using ANEs, researchers may need to overcome the limitation of their smooth surface, for example, by employing specific surface treatment methods such as mechanical abrasion, etching, and chemical modification, to promote the effective adhesion and uniform distribution of modifying materials. Besides controlling the surface morphology of ANEs, the choice of signal output method is also crucial for obtaining stable signals. In electrochemical sensors, potentiometric sensors and current-type sensors are two common types. Compared to current-type sensors, potentiometric sensors have advantages such as high sensitivity, low power consumption, no polarity requirement, and strong anti-interference capabilities. Most importantly, the potentiometric output method only requires a working electrode and a counter electrode to achieve signal output. Through reasonable device design, it is possible to break away from the traditional three-electrode discrete system and achieve the integration of a two-electrode system, making it more suitable for monitoring complex environments such as marine pores. To some extent, the two-electrode system greatly simplifies the original three-electrode detection system. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for preparing an integrated microneedle electrode for detecting chloride ions in pore water stock solution. This invention employs an integrated detection system based on a self-made microneedle working electrode combined with a reference electrode, selecting marine pore water as a representative environment to detect chloride ions in the pore environment. - Preliminary investigations were conducted on long-term detection (monitoring). The self-made microneedle electrode used ANE as the electrode substrate, and the electrode surface was pretreated using an electrochemical etching method. The etching process effectively increased the roughness of the ANE surface, thereby increasing the adhesion of the modification material to the electrode surface. Subsequently, AgNPs were modified onto the roughened surface of the electrochemically etched ANE using an electrodeposition method, resulting in AgNPs / ANE. Following this, based on AgNPs and Cl... - The rapid redox reaction between AgNPs / ANE and AgNWs allows for the preparation of AgCl / AgNPs / ANE after pretreatment with chloride. The self-made reference electrode used in this invention is based on a silver wire electrode. A fishbone-shaped Ag / AgCl reference electrode was prepared by immersing AgNWs in silver wire for chlorination. This self-made electrode exhibits stability in marine pore water comparable to commercially available reference electrodes. Combining these two self-made electrodes, with the self-made reference electrode wound onto the insulating layer surface of the working electrode, greatly simplifies the existing distributed electrode construction system.

[0006] This invention also employs an open-circuit potential (OCP) potential-type signal output method, which has advantages such as reversible response, high stability, resistance to protein interference, and high environmental compatibility, and is expected to achieve Cl -Accurate detection and long-term monitoring without the need for external reagents, and it is highly likely to become a key technology for in-depth understanding of Cl - One of the reliable tools for understanding changes and effects in the environment.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of the present invention provides a method for preparing an integrated microneedle electrode for detecting chloride ions in pore water stock solution, comprising preparing a working electrode AgCl / AgNPs / e-ANE and a fishbone-shaped Ag / AgCl reference electrode, and then winding the fishbone-shaped Ag / AgCl reference electrode around the insulating layer surface of the working electrode AgCl / AgNPs / e-ANE to construct an integrated microneedle electrode;

[0009] The preparation of the microneedle working electrode AgCl / AgNPs / e-ANE includes the following steps:

[0010] (1) Using the acupuncture needle electrode as the working electrode, constant potential etching was performed to obtain e-ANE;

[0011] (2) Using the e-ANE as the working electrode and the Ag / AgCl electrode as the reference electrode, a three-electrode system is constructed, and electrodeposition is performed to obtain AgNPs / e-ANE;

[0012] (3) Using the AgNPs / e-ANE as the working electrode and the Ag / AgCl electrode as the reference electrode to form a two-electrode system, place it in NaCl solution and perform chlorination treatment to obtain AgCl / AgNPs / e-ANE.

[0013] The preparation of the fishbone-shaped Ag / AgCl reference electrode includes the following steps:

[0014] Silver nanowire solution was uniformly dropped onto the surface of hydrophilically modified silver wire and allowed to evaporate at room temperature to obtain an AgNWs-modified electrode. Then, silver was deposited on the AgNWs-modified electrode in a mixed solution of AgNO3 and NaNO3 using a chronoamperometry method to obtain a fishbone-shaped Ag electrode. Subsequently, the fishbone-shaped Ag electrode was chlorinated in HCl solution by a chronoamperometry method to prepare a fishbone-shaped Ag / AgCl reference electrode.

[0015] Preferably, during the preparation of the working electrode AgCl / AgNPs / e-ANE, the voltage of the constant potential etching is 1.5-2.5V, and the etching time is 100-140s.

[0016] Preferably, in the preparation process of the working electrode AgCl / AgNPs / e-ANE, the electrolyte for the constant potential etching is an ethylene glycol solution containing 0.2-0.3 wt% sodium chloride and 0.5-1.5 vol% deionized water; more preferably, in the preparation process of the working electrode AgCl / AgNPs / e-ANE, the electrolyte for the constant potential etching is an ethylene glycol solution containing 0.23 wt% sodium chloride and 1 vol% deionized water.

[0017] Preferably, in the preparation process of the working electrode AgCl / AgNPs / e-ANE, the electrodeposition is carried out using a constant potential method, the electrolyte is a mixed solution of AgNO3 and NaNO3, and AgNPs / e-ANE is obtained after electrodeposition at a constant potential of -0.2V for 100-200s; more preferably, AgNPs / e-ANE is obtained after electrodeposition at a constant potential of -0.2V for 150s.

[0018] Preferably, in the preparation process of the working electrode AgCl / AgNPs / e-ANE, the chlorination treatment is carried out using the OCP method for at least 300 seconds until the potential reaches equilibrium, thereby obtaining AgCl / AgNPs / e-ANE.

[0019] Preferably, during the preparation of the working electrode AgCl / AgNPs / e-ANE, the concentration of the NaCl solution during the chlorination process is 1-10 μmol / L.

[0020] Preferably, in the preparation process of the fishbone-shaped Ag / AgCl reference electrode, the hydrophilic modification is performed by immersing the silver wire in a mixed aqueous solution of 1-3 wt% polyvinyl alcohol and 4-6 wt% glycerol for 10-30 min to perform hydrophilic modification; more preferably, the hydrophilic modification is performed by immersing the silver wire in a mixed aqueous solution of 2 wt% polyvinyl alcohol and 5 wt% glycerol for 10-30 min to perform hydrophilic modification; the length of the silver wire is 70 mm.

[0021] Preferably, during the preparation of the fishbone-shaped Ag / AgCl reference electrode, the concentration of the silver nanowire solution is 1-10 mg / mL.

[0022] Preferably, in the preparation of the fishbone-shaped Ag / AgCl reference electrode, a chronoamperometry method is used, with a deposition potential of -0.4V, to deposit silver on the AgNWs modified electrode in a mixed solution of 0.005-0.015 mol / L AgNO3 and 0.05-0.15 mol / L NaNO3.

[0023] Preferably, in the preparation of the fishbone-shaped Ag / AgCl reference electrode, the chlorination is carried out using a chronoamperometry method with an open-circuit potential of 250mV; the chlorination is carried out in a 0.05-0.15mol / L HCl solution.

[0024] The second aspect of the present invention provides an integrated microneedle electrode for detecting chloride ions in porous water stock solution, which is prepared by the method described above for preparing the integrated microneedle electrode for detecting chloride ions in porous water stock solution.

[0025] This invention monitors Cl - The principle:

[0026] Silver nanoparticles (AgNPs) are readily oxidized by oxygen to silver monoxide (Ag₂O) or silver ions (Ag). + Therefore, when AgNPs / ANE are placed in a solution containing Cl... - When in a buffer solution, a reversible redox equilibrium is established at the interface between AgNPs / ANE and the buffer solution (reaction 1).

[0027]

[0028] E1=E0Ag / AgCl-(RT / 2F)ln[Cl - (Equation 1)

[0029] Where E0Ag / AgCl, R, T, and F are the standard electrode potential, universal gas constant, temperature, and Faraday constant of Ag / AgCl, respectively. In the detection environment, the measured OCP potential value is equal to the value of the indicator electrode and the reference electrode (E... R The potential difference between them.

[0030] OCP=(E0Ag / AgCl-(RT / 2F)ln[Cl - ])-E R (Equation 2)

[0031] And due to E in the detection environment R It can be considered a constant, therefore OCP and [Cl] - The relation can be rewritten as follows:

[0032] OCP = C - klg[Cl] - (Equation 3)

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] The integrated dual-electrode microneedle electrode of this invention enables the low-cost construction of chloride ion microelectrodes, achieving accurate detection of chloride ions in marine pore water. This demonstrates the application potential of this sensing system in long-term on-site monitoring of chloride ions in marine pore water and provides a reliable method for a deeper understanding of the role of chloride ions in the environment.

[0035] This invention employs an electrochemical etching method to pretreat the electrode surface. The etching process can effectively increase the roughness of the ANE surface, thereby increasing the stability of the modification material adhering to the electrode surface.

[0036] By combining these two self-made electrodes to construct an integrated microneedle electrode, and winding the self-made reference electrode onto the insulating layer surface of the working electrode, the original distributed electrode construction system can be greatly simplified.

[0037] The constructed two-electrode integrated microelectrode utilizes an OCP-based potential-type recognition mechanism. The stability of the OCP-based potential-type output and current-type output in complex environments such as marine pore water was compared. The signal attenuation percentage during the potential-type test was 2.37%, while the signal attenuation percentage during the current-type test was 54.42%, demonstrating the excellent stability of the OCP-based potential-type sensor for long-term chloride ion monitoring. Attached Figure Description

[0038] Figure 1 To study the fabrication of integrated microneedle electrodes and their response to chloride ions;

[0039] Figure 2 This is a topographic image of the electrode surface during the fabrication process;

[0040] Figure 3 Electrochemical performance test graphs for ANE, e-ANE, and AgNPs / e-ANE;

[0041] Figure 4 A performance comparison graph of the reference electrode prepared for this example and a commercial Ag / AgCl reference electrode;

[0042] Figure 5 For integrated microneedle electrodes for Cl - The response test performance graph;

[0043] Figure 6 This is a stability test diagram of the integrated microneedle electrode during chloride ion detection. Detailed Implementation

[0044] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0045] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0046] Example 1

[0047] A method for fabricating an integrated microneedle electrode detection system includes the following steps:

[0048] (1) First, cut a 24AWG silicone wire with an inner diameter of 0.5mm to a length of 58mm, remove and discard the stranded copper wire, keeping only the insulating silicone sheath. Seal one end of the silicone sheath with 704 silicone rubber. After the silicone rubber has completely cured, insert a stainless steel acupuncture needle through the other end of the silicone sheath, piercing the cured silicone rubber seal. Then, use calipers to adjust the position of the acupuncture needle so that the 2mm needle tip is exposed, serving as the sensing layer of the electrode. Finally, use silicone rubber to fix the other end of the silicone insulating layer to the needle body. After the silicone rubber has completely cured, the self-made ANE is obtained. Since the copper-wound needle handle on the other side of the acupuncture needle has good conductivity, it can be directly connected to the electrode clamp of the electrochemical workstation.

[0049] (2) The obtained ANE and platinum wire electrodes were used as the working electrode and counter electrode, respectively. The electrolyte was an ethylene glycol solution containing 0.23 wt% sodium chloride (NaCl) and 1 vol% deionized water. The etching process adopted a constant potential method, and the etching parameters were a constant voltage of 2V and an etching time of 120s.

[0050] (3) A three-electrode system was constructed using the etched ANE (e-ANE) as the working electrode, a commercial silver chloride (Ag / AgCl) electrode as the reference electrode, and a platinum wire electrode as the counter electrode. Electrodeposition was performed in a mixed solution of 0.01 M AgNO3 and 0.1 M NaNO3. The electrodeposition process employed a constant potential method, and AgNPs / e-ANE was obtained after electrodeposition at a constant potential of -0.2 V for 150 s.

[0051] (4) The prepared AgNPs / e-ANE was used as the working electrode in the two-electrode system and the Ag / AgCl electrode was used as the reference electrode to form the two-electrode system. The system was placed in 5 μM NaCl solution and kept in OCP method for 300 s until the potential reached equilibrium (chlorination process) to obtain AgCl / AgNPs / e-ANE.

[0052] (5) The preparation steps of the self-made fishbone-shaped Ag / AgCl reference electrode are as follows: First, the obtained silver wire is cut into 70mm pieces and washed with ultrapure water, then dried with N2. The silver wire is immersed in a solution of 2% polyvinyl alcohol and 5% glycerol for 20min for hydrophilic modification, and then dried. Then, a 5mg / mL silver nanowire (AgNWs) solution is uniformly dropped onto the surface of the silver wire and left at room temperature for 1 day. There is no requirement for the amount of silver nanowire (AgNWs) solution added, as long as it is evenly covered, to obtain the AgNWs modified electrode. Then, using the chronoamperometry (deposition potential: -0.4V), silver is deposited on the AgNWs modified electrode in a mixed solution of 0.01M AgNO3 and 0.1M NaNO3. After drying with ultrapure water and N2, the fishbone-shaped Ag electrode is obtained. Then, the fishbone-shaped Ag electrode is chlorinated. The chlorination process is carried out in 0.1M HCl solution, and the chlorination is carried out by applying a potential of 250mV at its open circuit potential using the chronoamperometry. After the chlorination process is completed, the prepared fishbone-shaped Ag / AgCl reference electrode is washed three times with ultrapure water and dried in the dark before use.

[0053] (6) The self-made reference electrode was wound onto the insulating layer surface of the working electrode AgCl / AgNPs / e-ANE to construct an integrated microneedle electrode.

[0054] Figure 2 The image shows the surface morphology of the electrode during the fabrication process. Figure 2 a, b, d, and e show the surface morphology of the acupuncture needle electrode ANE before and after electrochemical etching. Compared with the smooth surface of the ANE tip, the acupuncture needle electrode exhibits a porous structure after electrochemical etching. Figure 2 c and f show the morphology of the electrode (AgNPs / e-ANE) after AgNPs modification. Compared with the untreated ANE, the electrodeposition morphology of AgNPs on the e-ANE surface is more uniform. Figure 2 gj characterized the surface morphology and elemental composition of AgCl / AgNPs / e-ANE, showing that Ag and Cl elements are uniformly distributed on the ANE surface. These results collectively indicate that partially oxidized AgNPs combine with chlorine to form a thin AgCl film (i.e., AgCl / AgNPs), which uniformly covers the ANE surface. Figure 2 k and l represent the surface morphology of the fishbone-shaped Ag / AgCl reference electrode in the integrated microneedle electrode. The fishbone-shaped structure has clear branches, and a large number of spherical structures appear in the main trunk and branches of the fishbone vein.

[0055] The electrochemical properties of ANE, e-ANE, and AgNPs / e-ANE were compared, and the results are as follows: Figure 3 As shown, Figure 3Figure a shows the results of an unetched acupuncture needle electrode (black line) and an etched acupuncture needle electrode (red line) at 5 mM [Fe(CN)6]. 3- / 4- Cyclic volt-ampere response diagram in the figure, Figure 3 Figure b shows the differential pulse voltammograms obtained by the ANE, e-ANE, and AgNPs / e-ANE sensors in 0.1M PBS (pH 7.0). Figure 3 It is known that the smooth surface of unetched ANE results in fewer active sites, which severely affects the electron transfer process on the electrode surface. However, under the same experimental conditions, the electrochemically etched e-ANE showed a significant increase in redox peak current and the appearance of a distinct reduction peak. The electrochemical etching process effectively improves the electrode conductivity and promotes the [Fe(CN)6] oxidation process. 3- / 4- Electron transfer on the ANE surface. Figure 3 b shows that no obvious voltammetric peaks were observed in ANE and e-ANE in the 0.1–0.6 V potential range in PBS, while AgNPs / e-ANE showed two very obvious oxidation peaks at 0.31 V and 0.40 V, which also indicates the successful loading of AgNPs.

[0056] Comparison of self-made micro-reference electrodes and commercial reference electrodes with different proportions of redox materials [Fe(CN)6] 3- / 4- Electrochemical stability of the solution at different pH levels and under long-term use. Figure 4 In the process, micro-reference electrodes (relative to commercial Ag / AgCl reference electrodes) were used in 0.1M Fe(CN)6 solutions with different proportions. 3- / Fe(CN)6 4- Potential response (a) in solutions with pH range 4–10 (b) and stability (c) in 0.1 M KCl solution. The prepared micro-reference electrode was tested in [Fe(CN)6] solutions with molar ratios of 0.1, 1, and 10. 3- / 4- The solution exhibits good potential stability. Figure 4 a). The self-made micro-reference electrode exhibits good potential stability within the pH range of 4–10, while commercial electrodes are affected by pH changes, resulting in fluctuations in their signal output. Therefore, compared to commercial reference electrodes, the self-made micro-reference electrode demonstrates better stability in the potentially variable pH environment of the marine porous environment. Figure 4 b). The micro-reference electrode can continuously measure in 0.1M KCl solution for more than 6 hours with a potential difference of only about 10mV. In contrast, the potential of the commercial reference electrode changed significantly after long-term use. Figure 4 c).

[0057] Figure 5The integrated microneedle electrode was used to compare the output of potential and current-type test signals in marine pore water containing 20 μM NaCl for 1600 s (a); and histograms showing the percentage decrease of potential and current-type test signals after 1600 s of continuous testing (b). The integrated microneedle electrode was also used in marine pore water (pH = 7.0) with continuous addition of Cl... - OCP response (c) and OCP response value at time Cl - The linear relationship between the concentration logarithm and the concentration (d). Figure 5 After injection of 20 μM NaCl, the OCP of the integrated microneedle electrode decreased from 0.173 to 0.143 V and remained almost unchanged during subsequent 1600 s monitoring. The current response of the amperometric sensor with the same modification increased from 0.821 nA to 6.582 nA after 20 μM NaCl injection, then decreased to 3.35 nA after 1600 s of continuous monitoring. The signal attenuation percentage during potentiometric testing was 2.37%, and during current testing it was 54.42%. Figure 5 b) demonstrates that the OCP-based integrated microneedle electrode is used for Cl - Long-term monitoring exhibits excellent stability. Figure 5 c and d represent the use of integrated microneedle electrodes to apply Cl... - The analytical properties of the two-electrode integrated microprobe were evaluated in terms of stability. OCP was tested upon the addition of Cl... - The potential gradient then changes rapidly within milliseconds and reaches equilibrium in about 2 seconds. The decrease in the potential gradient on AgCl / AgNPs / ANE is related to Cl... - There is a linear relationship between the logarithmic concentration and the concentration. Figure 5 d), ranging from 2.5 to 40 μM (V(mV)=-22.15lgC(μM)-93.95(mV), R 2 =0.997), and the detection limit was 1.1 μM. The results indicate that AgCl / AgNPs / ANE has a high detection limit for Cl... - It exhibits a good response, and its sensitivity conforms to the mechanistic explanations in reaction equations 2 and 3.

[0058] Figure 6 In this study, an integrated microneedle electrode was added to marine pore water (pH = 7.0) with 20 μM Cl. - OCP responses (a) recorded by AgNPs / e-ANE (black line) and AgCl / AgNPs / e-ANE (red line) after adding 20 μM ascorbic acid (AA) and 20 μM cysteine ​​(Cys); 20 μM Cl added to marine pore water (pH = 7.0) - 10mM SO4 2- 10mM CO3 2- 10mM NO3- 0.1mMCu 2+ 0.1mM Fe 3+ OCP response recorded after AgCl / AgNPs / ANE (b); Static contact angle test of bare GCE and AgCl / AgNPs / GCE (c); Integrated microneedle electrode with 20 mg mL of NaCl added to marine pore water containing 20 μM NaCl (pH = 7.4). -1 Bovine serum albumin (BSA, 10 mg / mL each time) -1 The OCP response obtained after adjustment of 20 μM NaCl (pH=7.0) in marine pore water by adding NaOH and HCl (e) and the OCP response recorded at 1200 s in 20 μM NaCl marine pore water (pH=7.4) (f).

[0059] Figure 6 Figure a compares the anti-interference performance and stability of AgNPs / e-ANE and AgCl / AgNPs / e-ANE. AgCl / AgNPs / ANE shows no potential response to AA and Cys. Considering the concentration of common ions in the environment, adding 10 mM SO42-... 2- CO3 2- NO3 - and 0.1mM Cu 2+ Fe 3+ The above-mentioned common anions and cations did not show a significant potential potential response at the AgCl / AgNPs / / e-ANE junction. The static water contact angle between GCE and AgCl / AgNPs / GCE was measured to investigate its anti-protein adsorption performance. Figure 6 c) The water contact angle of AgCl / AgNPs / e-ANE (50.8 ± 1.3°) is smaller than that of GCE (77.7 ± 0.8°) in the figure. Since the contact angle cannot be characterized on the needle tip surface, this invention uses a glassy carbon electrode (GCE) as the loading material for contact angle characterization. The preparation method of AgCl / AgNPs / GCE is the same as in Example 1, using GCE instead of e-ANE to obtain AgCl / AgNPs / GCE. It is speculated that the low interference of the protein output signal in AgCl / AgNPs / e-ANE may be due to the weak interaction between AgCl and protein, as well as the hydrophilicity of the AgCl / AgNPs surface.

[0060] Figure 6 d. Assess the impact of protein contamination on Cl - The effect of adding high concentrations of BSA on the OCP reaction on AgCl / AgNPs / e-ANE was investigated. - Changes in OCP signal, with the addition of BSA (10 mg / mL)-1 Unlike the amperometric method, the addition of protein did not cause a significant change in potential, indicating that the protein addition had little effect on the OCP reaction. The pH of the simulated seawater was adjusted from 7.4 to 8.5 and 5.5, and the potential changes were observed. Figure 6 e) It can be seen that the OCP reaction remains unchanged within the pH range of 5.5 to 8.5. Furthermore, the AgCl / AgNPs / e-ANE reaction with 20 μM Cl... - It exhibits a very stable potential response, lasting for more than 20 minutes. Figure 6 f). The above experiments effectively demonstrate the stability of the two-electrode integrated microelectrode in chloride ion detection, which is crucial for achieving chloride ion monitoring. - The dynamic changes are very important.

[0061] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for preparing an integrated microneedle electrode for detecting chloride ions in porous water stock solution, characterized in that, The process includes the preparation of the working electrode AgCl / AgNPs / e-ANE and the preparation of the fishbone-shaped Ag / AgCl reference electrode. Then, the fishbone-shaped Ag / AgCl reference electrode is wound around the insulating layer surface of the working electrode AgCl / AgNPs / e-ANE to construct an integrated microneedle electrode. The preparation of the working electrode AgCl / AgNPs / e-ANE includes the following steps: (1) Using the acupuncture needle electrode as the working electrode, constant potential etching was performed to obtain e-ANE; (2) Using the e-ANE as the working electrode and the Ag / AgCl electrode as the reference electrode, a three-electrode system is constructed, and electrodeposition is performed to obtain AgNPs / e-ANE; (3) Using the AgNPs / e-ANE as the working electrode and the Ag / AgCl electrode as the reference electrode to form a two-electrode system, place it in NaCl solution and perform chlorination treatment to obtain AgCl / AgNPs / e-ANE. The preparation of the fishbone-shaped Ag / AgCl reference electrode includes the following steps: Silver nanowire solution was uniformly dropped onto the surface of hydrophilically modified silver wire and allowed to evaporate at room temperature to obtain an AgNWs-modified electrode. Then, silver was deposited on the AgNWs-modified electrode in a mixed solution of AgNO3 and NaNO3 using a chronoamperometry method to obtain a fishbone-shaped Ag electrode. Subsequently, the fishbone-shaped Ag electrode was chlorinated in HCl solution by a chronoamperometry method to prepare a fishbone-shaped Ag / AgCl reference electrode.

2. The method for preparing the integrated microneedle electrode for chloride ion detection in porous water stock solution according to claim 1, characterized in that, During the fabrication of the working electrode AgCl / AgNPs / e-ANE, the constant potential etching voltage is 1.5-2.5V and the etching time is 100-140s.

3. The method for preparing the integrated microneedle electrode for chloride ion detection in porous water stock solution according to claim 2, characterized in that, In the preparation of the working electrode AgCl / AgNPs / e-ANE, the electrolyte for constant potential etching is an ethylene glycol solution containing 0.1-0.4 wt% sodium chloride and 0.5-1.5 vol% deionized water.

4. The method for preparing the integrated microneedle electrode for chloride ion detection in porous water stock solution according to claim 1, characterized in that, In the preparation of the working electrode AgCl / AgNPs / e-ANE, the electrodeposition is carried out using a constant potential method, with the electrolyte being a mixed solution of AgNO3 and NaNO3. After electrodeposition for 100-200s at a constant potential of -0.2V, AgNPs / e-ANE is obtained.

5. The method for preparing the integrated microneedle electrode for chloride ion detection in porous water stock solution according to claim 1, characterized in that, In the preparation of the working electrode AgCl / AgNPs / e-ANE, the chlorination treatment is carried out using the OCP method for at least 300 seconds until the potential reaches equilibrium, thus obtaining AgCl / AgNPs / e-ANE.

6. The method for preparing the integrated microneedle electrode for chloride ion detection in porous water stock solution according to claim 1, characterized in that, In the preparation process of the fishbone-shaped Ag / AgCl reference electrode, the hydrophilic modification is performed by immersing the silver wire in a mixed aqueous solution of 1-3 wt% polyvinyl alcohol and 4-6 wt% glycerol for 10-30 minutes to perform hydrophilic modification.

7. The method for preparing the integrated microneedle electrode for chloride ion detection in porous water stock solution according to claim 1, characterized in that, In the preparation of the fishbone-shaped Ag / AgCl reference electrode, the concentration of the silver nanowire solution is 1-10 mg / mL.

8. The method for preparing the integrated microneedle electrode for chloride ion detection in porous water stock solution according to claim 1, characterized in that, In the preparation of the fishbone-shaped Ag / AgCl reference electrode, the chronoamperometry method was used, with a deposition potential of -0.4V, to deposit silver on the AgNWs modified electrode in a mixed solution of 0.005-0.015 mol / L AgNO3 and 0.05-0.15 mol / L NaNO3.

9. The method for preparing the integrated microneedle electrode for chloride ion detection in pore water stock solution according to claim 1, characterized in that, In the preparation of the fishbone-shaped Ag / AgCl reference electrode, the chlorination is carried out using a chronoamperometry method with an open-circuit potential of 240-260 mV; the chlorination is performed in a 0.05-0.15 mol / L HCl solution.

10. An integrated microneedle electrode for detecting chloride ions in porous water stock solution, characterized in that, It is prepared by the method for preparing the integrated microneedle electrode for chloride ion detection in pore water stock solution according to any one of claims 1-9.

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