A pedot solution, an electrochemical sensing electrode and a preparation method

Abstract

This invention relates to a PEDOT solution, an electrochemical sensing electrode, and a preparation method thereof, comprising 75-200 parts of a PEDOT:PSS aqueous dispersion, 3-10 parts of an organic solvent, and 0.3-2 parts of a crosslinking agent, wherein the crosslinking agent is a silane coupling agent. Through the synergistic ratio of these components, a composite functional layer is formed on the electrode surface, solving the problems of insufficient interfacial wetting and electro-drift caused by the hydrophobicity of traditional electrode substrates, ensuring stable solid-liquid interfacial contact between the electrode and detection media such as aqueous solutions and sweat. Simultaneously, the three-dimensional network structure constructed by the crosslinking reaction allows the composite functional layer to form a strong chemical bond with the electrode substrate, effectively avoiding problems such as modification layer detachment and swelling. This application replaces traditional electroplating processes, is suitable for integrated products such as wearable sweat patches, avoids problems such as electrolyte corrosion of the substrate and short circuits, and is suitable for the modification needs of embedded, irregularly shaped, and array electrodes.

Description

Technical Field

[0001] This invention relates to the field of electrochemical sensor technology, and in particular to a PEDOT solution, an electrochemical sensing electrode, and a preparation method thereof. Background Technology

[0002] Electrochemical sensors are widely used in various fields such as biomedical detection, environmental monitoring, and food safety inspection due to their advantages such as fast response speed, high sensitivity, compact structure, and controllable cost.

[0003] In existing technologies, the electrode substrates of electrochemical sensors mostly employ glassy carbon electrodes, gold electrodes, platinum electrodes, or carbon-based electrodes. While these electrode substrates possess good conductivity and a certain degree of chemical stability, meeting basic electrochemical sensing requirements, their surfaces are often hydrophobic or partially hydrophobic due to their inherent material properties, resulting in low surface energy and low electrochemical interfacial capacitance. This characteristic leads to insufficient wettability between the electrode and the electrolyte, making it difficult to form stable interfacial contact in complex detection environments such as aqueous solutions and sweat. This directly affects the consistency of the sensing signal, and the low interfacial capacitance also limits the sensor's detection sensitivity, making it difficult to meet high-precision sensing requirements.

[0004] To address these shortcomings, the industry commonly employs a technique of modifying the electrode substrate surface with conductive polymer materials. PEDOT and PEDOT:PSS, due to their excellent conductivity, good electrochemical activity, and biocompatibility, are widely used to modify electrodes to improve interfacial capacitance, wettability, and reduce interfacial resistance. In existing technologies, electrode modification schemes based on PEDOT / PEDOT:PSS typically involve electroplating to form a conductive polymer layer on the electrode surface. This modified layer optimizes the electrode's electrochemical performance, enhancing the sensor's overall detection effect. However, existing electroplating modification processes are only applicable to standalone electrode substrates, meaning they must be performed before the electrode is fully assembled with the sensor product.

[0005] Once electrodes and sensor products (especially wearable sweat patches) are assembled, electroplating can no longer be used for further modification. Firstly, the overall structure of sensor products often includes flexible substrates and encapsulation materials that are susceptible to electroplating environments. The electrolyte during electroplating can corrode the substrate, damage the encapsulation structure, and the electric field can cause short circuits or malfunctions within the product. Secondly, the assembled electrodes are often embedded or irregularly shaped, making it difficult to ensure a uniform electric field distribution on the electrode surface during electroplating. Furthermore, the electrolyte cannot fully contact all areas of the electrode to be modified. Even if electroplating is forced, a uniformly thick and structurally stable conductive polymer modification layer cannot be formed, which can actually compromise the overall performance of the product. In addition, even with a process of "electroplated to modify the electrodes before combining them with the product," the bonding and assembly operations during the process can damage the electroplated modification layer, leading to peeling, cracking, or structural damage, ultimately failing to guarantee stable sensing performance of the electrodes. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides a PEDOT solution, an electrochemical sensing electrode, and a preparation method thereof.

[0007] The technical solution adopted by this application to solve its technical problem is:

[0008] A PEDOT solution contains the following components and their mass fractions: PEDOT:PSS aqueous dispersion 75-200 parts; 3-10 parts organic solvent; Crosslinking agent 0.3-2 parts; The crosslinking agent is a silane coupling agent.

[0009] More specifically, the organic solvent is ethylene glycol, the crosslinking agent is 3-glycidoxypropyltrimethoxysilane, and the solid content of the PEDOT:PSS aqueous dispersion is 1.0-1.3 wt%.

[0010] More specifically, the mass fractions of each component are: 100 parts of PEDOT:PSS aqueous dispersion; Five parts of a high-boiling-point organic solvent; 1 part crosslinking agent.

[0011] The crosslinking agent is a silane coupling agent containing epoxy groups.

[0012] An electrochemical sensing electrode includes an electrode substrate and a composite functional layer disposed on a working area of ​​the electrode substrate surface. The composite functional layer comprises a cross-linked network structure formed by curing a PEDOT solution for electrochemical sensing electrodes as described above. The cross-linked network structure is formed by chemical bonding of the PEDOT:PSS and the cross-linking agent.

[0013] More specifically, the electrode substrate is a flexible substrate.

[0014] A method for preparing an electrochemical sensing electrode includes the following steps: S1. Provide the components of the PEDOT solution as described above and mix them in proportion to form a homogeneous PEDOT solution; S2. Apply the PEDOT solution to the working area on the surface of the electrode substrate; S3. The electrode substrate containing the PEDOT solution is cured to solidify the PEDOT solution and cause a cross-linking reaction to form a three-dimensional network structure, thereby forming a composite functional layer on the surface of the electrode substrate.

[0015] More specifically, in S1, PEDOT:PSS aqueous dispersion, organic solvent and crosslinking agent are mixed in a container according to the proportion, and then ultrasonically mixed for 5 minutes at room temperature.

[0016] More specifically, in S2, the coating method is one of drip coating, spray coating, screen printing or inkjet printing.

[0017] More specifically, in S3, the curing process is as follows: S31. Preheat and cure at 50-70℃ for 20-40 minutes to remove organic solvents; S32. Heating and curing at 90-110℃ for 20-40 minutes to allow the crosslinking agent to undergo a crosslinking reaction with PEDOT:PSS and the electrode substrate surface.

[0018] More specifically, after S3, there is also a step S4, which involves rinsing with deionized water to remove residual uncrosslinked small molecules and drying at room temperature.

[0019] The beneficial effects of this invention are as follows: This application improves the performance of electrochemical sensing electrodes through PEDOT solution formulation design and non-electroplating preparation process; by synergistically combining PEDOT:PSS aqueous dispersion, ethylene glycol, and epoxy-containing silane coupling agent, a composite functional layer with both high capacitance and excellent hydrophilicity is formed on the electrode surface, solving the problems of insufficient interfacial wetting and electro-drift caused by the hydrophobicity of traditional electrode substrates, ensuring stable solid-liquid interface contact between the electrode and detection media such as aqueous solutions and sweat. Simultaneously, the three-dimensional network structure constructed by the cross-linking reaction allows the composite functional layer to form a strong chemical bond with the electrode substrate, effectively avoiding problems such as modification layer detachment and swelling; This application replaces traditional electroplating processes with gentle coating methods such as drop coating, spray coating, screen printing, or inkjet printing, which not only adapts to integrated products such as wearable sweat patches, avoiding problems such as electrolyte corrosion of the substrate and short circuits, but also controls the thickness and uniformity of the modification layer, adapting to the modification needs of embedded, irregularly shaped, and array electrodes. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the electrochemical sensing electrode of the present invention; Figure 2 This is a flowchart of the preparation method of the electrochemical sensing electrode of the present invention; Figure 3 This is a test diagram of Embodiment 1 of the present invention; Figure 4 This is a test diagram of Embodiment 2 of the present invention; Figure 5 This is a test diagram of Embodiment 3 of the present invention; Figure 6 This is a test diagram of Embodiment 4 of the present invention; Figure 7 This is a test diagram of Embodiment 5 of the present invention; Figure 8 This is a test diagram of Embodiment 6 of the present invention; Figure 9 This is a test diagram of Embodiment 7 of the present invention; Figure 10 This is a test diagram of Comparative Example 1 of the present invention; Figure 11 This is a test diagram of Comparative Example 2 of the present invention. Detailed Implementation

[0021] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The direction of movement is also relative and is not limited to an absolute direction of movement. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, the technical features involved in the different embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0024] This application provides a PEDOT solution suitable for the preparation and modification of electrochemical sensing electrodes, especially applicable to integrated sensors (such as wearable sweat patches) where electroplating processes are not feasible. It can form a modification layer (composite functional layer 200, such as...) on the surface of the electrode substrate 100 through methods such as drop casting and printing, possessing high conductivity, high capacitance, and an excellent hydrophilic interface. Figure 1 As shown in the figure, it effectively solves the problems of poor adhesion, insufficient wettability and poor structural stability of existing electrode modification layers, and significantly improves the overall performance and long-term reliability of electrochemical sensing electrodes.

[0025] The PEDOT solution contains the following components and their mass fractions: PEDOT:PSS aqueous dispersion 75-200 parts; 3-10 parts of high-boiling-point organic solvent; Crosslinking agent 0.3-2 parts; The crosslinking agent is a silane coupling agent containing epoxy groups.

[0026] PEDOT:PSS is poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate), preferably an aqueous dispersion of PEDOT:PSS with a solid content of 1.0-1.3wt%. It has excellent conductivity, electrochemical activity and film-forming properties, and can provide a good electron transport channel for the modified electrode. At the same time, the sulfonate groups it contains can initially improve the wettability of the electrode surface.

[0027] The organic solvent is used to control the viscosity, surface tension, and film quality of the solution, ensuring that the solution is suitable for preparation processes such as drop coating and inkjet printing. At the same time, it can improve the spreadability of PEDOT:PSS on the electrode surface and avoid defects such as pinholes and cracks after film formation. The organic solvent is preferably ethylene glycol. Compared with other organic solvents (such as propylene glycol, ethanol, etc.), ethylene glycol has a high boiling point and high volatility. It is not easy to evaporate quickly during solution preparation and film formation, which would lead to uneven film layer. At the same time, its strong polarity allows it to be miscible with PEDOT:PSS aqueous dispersion without causing phase separation, and it can further improve the wettability of the solution on various electrode substrates.

[0028] The crosslinking agent is a silane coupling agent. The methoxysilane group in the molecule of the crosslinking agent, and the silanol group formed after hydrolysis of the methoxysilane group, can undergo a condensation reaction with the hydroxyl groups on the surface of the electrode substrate 100 to form a stable chemical bond. Further, the crosslinking agent in this application is a silane coupling agent containing epoxy groups, preferably 3-glycidoxypropyltrimethoxysilane. On the basis of the stable chemical bond between the methoxysilane group and the electrode substrate 100, the epoxy group undergoes a highly efficient crosslinking reaction with the active groups (such as sulfonate groups) in the PEDOT:PSS molecular chain to form a three-dimensional network structure. Under the dual effect, it not only significantly improves the mechanical strength, water resistance, and adhesion and bonding strength of the modified layer to the electrode substrate 100, but also further optimizes the electrochemical stability of the electrode interface, avoiding the modification layer from falling off or swelling in aqueous solutions, sweat, and other environments. Moreover, the crosslinking reaction conditions are mild and will not destroy the conductive structure of PEDOT:PSS, which can enhance its structural stability and environmental corrosion resistance while ensuring the high conductivity of the modified layer.

[0029] In the field of electrochemical sensors, existing technologies exhibit electrical drift, which severely limits the long-term stable application of sensors in aqueous solutions, sweat, and other environments. Unmodified traditional electrode substrates can experience electrical drift of up to 3 mV, and even electrodes modified with conventional electrodeposition of PEDOT often show drift greater than 2 mV, leading to accumulated detection errors and failing to meet high-precision requirements. The main causes are: the electrode substrate often has a small surface area and small pore size, making rapid wetting difficult and resulting in insufficient interfacial wetting; as the electrode substrate gradually wets, electrical drift occurs; the modified layer prepared by electrodeposition has uneven morphology and disordered pores; and the modified layer only physically adsorbs onto the substrate without stable cross-linking, making it prone to swelling and detachment. All these factors ultimately cause continuous fluctuations in the actual effective contact area of ​​the electrode, triggering electrical drift.

[0030] To address the aforementioned electrical drift phenomenon, this application adjusts the formulation of the PEDOT solution, with the following mass fractions for each component: 100 parts of PEDOT:PSS aqueous dispersion; Five parts of a high-boiling-point organic solvent; 1 part crosslinking agent; The crosslinking agent is a silane coupling agent containing epoxy groups.

[0031] The organic solvent is ethylene glycol. In this application, 5 parts of ethylene glycol are selected, which is miscible with PEDOT:PSS aqueous dispersion, significantly improving the spreadability of the solution on the hydrophobic substrate surface, ensuring the formation of a uniform film layer without pinholes or cracks, avoiding insufficient wetting, reducing fluctuations in effective contact area, and thus suppressing electro-drift.

[0032] The crosslinking agent is 3-glycidoxypropyltrimethoxysilane (GOPS). Uncrosslinked or insufficiently crosslinked films are prone to swelling and detachment in environments such as aqueous solutions and sweat, leading to dynamic changes in the effective contact area and resulting in electro-drift. In this application, GOPS can undergo crosslinking reactions with the acidic groups in the PEDOT:PSS molecular chain and the hydroxyl groups on the electrode substrate 100 surface through epoxy groups, forming a stable three-dimensional network structure.

[0033] Based on the above PEDOT solution, such as Figure 1 This application provides an electrochemical sensing electrode, including an electrode substrate 100 and a composite functional layer 200 disposed on the working area of ​​the surface of the electrode substrate 100. The composite functional layer 200 is formed by heat treatment and cross-linking of the above-mentioned PEDOT solution. The contact angle of the composite functional layer 200 when in contact with sweat is less than 60°.

[0034] Based on the above electrochemical sensing electrodes, such as Figure 2 This application provides a preparation method, including the following steps: S1. Mix PEDOT:PSS aqueous dispersion, organic solvent and crosslinking agent in a container according to the ratio, and place it in an ultrasonic cleaner at room temperature for ultrasonic mixing for 5 minutes to ensure that PEDOT:PSS aqueous dispersion, organic solvent and crosslinking agent are fully miscible to form a homogeneous and stable PEDOT solution.

[0035] S2. Using one of the following methods—drop coating, spray coating, screen printing, or inkjet printing—the PEDOT solution prepared in S1 is coated onto the working area of ​​the electrode substrate 100. During the coating process, the coating amount is controlled to ensure that the PEDOT solution uniformly covers the working area, forming a wet film with a thickness of 1-5 μm. Drop coating and spray coating are suitable for small-batch laboratory preparation, while screen printing and inkjet printing are suitable for large-scale industrial production.

[0036] S3. The electrode substrate 100 containing the PEDOT solution is cured to solidify the PEDOT solution and cause a cross-linking reaction to form a three-dimensional network structure, thereby forming the composite functional layer 200 on the surface of the electrode substrate 100; wherein the curing process employs a segmented curing process, as detailed below. S31. Preheating and curing: Place the electrode substrate 100 coated with PEDOT solution into a constant temperature oven and preheat and cure at 50-70℃ for 20-40 minutes. Slowly remove the solvent in the PEDOT solution to prevent the formation of bubbles or pores inside the film layer due to rapid solvent evaporation, and at the same time create stable conditions for subsequent crosslinking reactions.

[0037] S32. High-temperature curing: After preheating and curing, keep the oven sealed and raise the temperature to 90-110℃. Continue heating and curing at this temperature for 20-40 minutes to promote the full cross-linking reaction between the epoxy groups in the cross-linking agent molecules and the active groups in the PEDOT:PSS molecular chain and the hydroxyl groups on the surface of the electrode substrate 100, ultimately forming a stable three-dimensional network structure. This structure is used to improve the mechanical strength, water resistance and adhesion of the composite functional layer 200 to the electrode substrate 100, thereby structurally blocking the path of electrical drift.

[0038] S4. After high-temperature curing, remove the electrode substrate 100 from the oven and allow it to cool naturally to room temperature. Then, rinse the composite functional layer 200 on the electrode surface with deionized water to remove small molecule impurities that did not participate in the cross-linking reaction during the curing process. After rinsing, place the electrode in a room temperature environment to dry naturally, or dry it in a 30-40℃ forced-air drying oven for 10-20 minutes to ensure that the electrode surface is completely dry. Finally, a stable composite functional layer 200 is formed on the surface of the electrode substrate 100.

[0039] For different formulations of PEDOT solution, the following electrochemical sensing electrodes were fabricated as examples (Examples 1-7) using the above preparation method. A potassium ion selective film was modified on the surface of the composite functional layer 200 in each example to measure the potassium ion concentration. Comparative Example 1 with an unmodified composite functional layer 200 and Comparative Example 2 prepared by electroplating were set as references. Then, an electrochemical workstation was connected, and open-circuit voltage was selected for testing. Each example and comparative example were tested at concentrations of 0.5 mM, 1 mM, 2 mM, 4 mM, 8 mM, 16 mM, and 32 mM, respectively, and each concentration was tested for 300 s.

[0040]

[0041] Examples 1-7 all employ the non-electroplating preparation method described in this invention, without using any electroplating-related processes, yet all achieve electro-drift performance superior to or close to that of traditional electroplating processes. Specifically, the electro-drift of Comparative Example 2 is ±1.344mV, while the electro-drift of Example 1 (±1.47mV) of this application is close to that of the electroplating process, and Example 7 (±0.4mV) far exceeds the electro-drift level of the electroplating process; although the electro-drift of the other examples is slightly higher than that of the electroplating process, they are all superior to that of Comparative Example 1 (±3mV) without modification of the composite functional layer 200. More importantly, this application solves the problem that the electroplating process cannot be adapted to wearable sweat patches, and can be directly used for electrode modification already integrated with the product. Moreover, the preparation process is simple and controllable, with lower costs, making it more suitable for mass production.

[0042] Among all the embodiments and comparative examples, Example 7 exhibits the best electrical drift characteristics, with an electrical drift of only ±0.4mV, which is not only far lower than all other embodiments but also superior to Comparative Examples 1 and 2. Example 7, with the synergistic effect of PEDOT:PSS aqueous dispersion, ethylene glycol, and GOPS, demonstrates stable signal reference, effectively meeting the requirements for long-term high-precision detection in complex environments such as aqueous solutions and sweat.

[0043] This application achieves improved performance of electrochemical sensing electrodes through PEDOT solution formulation design and non-electroplating preparation process. By synergistically combining PEDOT:PSS aqueous dispersion, ethylene glycol, and epoxy-containing silane coupling agent, especially the optimal combination of 100:5:1, a composite functional layer 200 with both high capacitance and excellent hydrophilicity is formed on the electrode surface. This composite functional layer 200 has a contact angle with sweat of less than 60°, solving problems such as insufficient interfacial wetting and electrical drift caused by the hydrophobicity of traditional electrode substrates, ensuring stable solid-liquid interfacial contact between the electrode and detection media such as aqueous solutions and sweat. Simultaneously, the three-dimensional network structure constructed by the cross-linking reaction allows the composite functional layer 200 to form a strong chemical bond with the electrode substrate 100, effectively avoiding problems such as modification layer detachment and swelling. Combined with a segmented curing process, the electrode electrical drift is reduced to ±0.4mV, far superior to unmodified electrodes and traditional electroplated modified electrodes, suppressing signal fluctuations and meeting the requirements for long-term high-precision detection.

[0044] Furthermore, this application replaces traditional electroplating processes with gentle coating methods such as drop coating, spray coating, screen printing, or inkjet printing. This not only makes it suitable for integrated products such as wearable sweat patches, avoiding problems such as electrolyte corrosion of the substrate and short circuits, but also allows for control of the thickness and uniformity of the modified layer, adapting to the modification needs of embedded, irregularly shaped, and array electrodes. The preparation method itself is simple, controllable, and lower in cost, ensuring the sensor's high capacitance, low interfacial resistance, and other electrical properties, while improving the product's repeatability and lifespan. It provides a more stable and practical technical solution for electrochemical sensors in fields such as biomedical detection and environmental monitoring, especially suitable for long-term continuous monitoring scenarios in complex environments.

[0045] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A PEDOT solution, characterized in that, The components and their mass fractions are as follows: PEDOT:PSS aqueous dispersion 75-200 parts; 3-10 parts organic solvent; Crosslinking agent 0.3-2 parts; The crosslinking agent is a silane coupling agent.

2. The PEDOT solution according to claim 1, characterized in that, The organic solvent is ethylene glycol, and the crosslinking agent is 3-glycidoxypropyltrimethoxysilane; the solid content of the PEDOT:PSS aqueous dispersion is 1.0-1.3 wt%.

3. The PEDOT solution according to claim 2, characterized in that, The mass fractions of each component are, 100 parts of PEDOT:PSS aqueous dispersion; Five parts of a high-boiling-point organic solvent; 1 part crosslinking agent; The crosslinking agent is a silane coupling agent containing epoxy groups.

4. An electrochemical sensing electrode, characterized in that, The invention includes an electrode substrate and a composite functional layer disposed on the working area of ​​the electrode substrate surface. The composite functional layer comprises a cross-linked network structure formed by curing the PEDOT solution according to any one of claims 1-3. The cross-linked network structure is formed by chemical bonding of the PEDOT:PSS and the cross-linking agent.

5. The electrochemical sensing electrode according to claim 4, characterized in that, The electrode substrate is a flexible substrate.

6. A method for preparing an electrochemical sensing electrode, characterized in that, Includes the following steps, S1. Provide each component of the PEDOT solution as described in any one of claims 1-3 and mix them in proportion to form a homogeneous PEDOT solution; S2. Apply the PEDOT solution to the working area on the surface of the electrode substrate; S3. The electrode substrate containing the PEDOT solution is cured to solidify the PEDOT solution and cause a cross-linking reaction to form a three-dimensional network structure, thereby forming a composite functional layer on the surface of the electrode substrate.

7. The preparation method according to claim 6, characterized in that, In S1, PEDOT:PSS aqueous dispersion, organic solvent and crosslinking agent are mixed in a container according to the proportion, and then ultrasonically mixed for 5 minutes at room temperature.

8. The preparation method according to claim 6, characterized in that, In S2, the coating method is one of drip coating, spray coating, screen printing or inkjet printing.

9. The preparation method according to claim 6, characterized in that, In S3, the curing process is performed as follows: S31. Preheat and cure at 50-70℃ for 20-40 minutes to remove organic solvents; S32. Heating and curing at 90-110℃ for 20-40 minutes to allow the crosslinking agent to undergo a crosslinking reaction with PEDOT:PSS and the electrode substrate surface.

10. The preparation method according to claim 6, characterized in that, Following S3, step S4 is included, in which the sample is rinsed with deionized water to remove any remaining uncrosslinked small molecules and then dried at room temperature.

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