Electrochemical sensor and manufacturing method thereof

Abstract

The invention discloses an electrochemical sensor and a manufacturing method thereof, and relates to the technical field of electrochemistry, the electrochemical sensor is constructed by taking a pipette tip as a substrate, a traditional customized substrate is replaced, the structural design is simple, and materials are convenient to take; in the assembling process, the fixing unit is arranged at the position, with the through hole, of the pipette tip in a sleeving mode, after the clamping groove of the fixing unit is adjusted to be parallel to the center axis of the through hole, the two ends of the through hole are sealed at the joint of the fixing unit and the pipette tip through the first sealing structure; one end, with an electrode reaction area, of the sensing piece is inserted into the clamping groove of the fixing unit, the second sealing structure is arranged at the inlet of the clamping groove to seal the inlet of the clamping groove, the formed reaction cavity enables a solution to react in the reaction area without interference, and the whole electrochemical sensor is simple in assembly process and high in reliability. Complicated positioning and sealing processes are not needed, the assembling time is greatly shortened, and meanwhile the sensor is small in overall size, convenient to carry and capable of achieving on-site rapid detection.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to an electrochemical sensor and its fabrication method. Background Technology

[0002] Electrochemical sensors are widely used in environmental monitoring, food detection, and biomedicine due to their high sensitivity, good selectivity, and fast response speed. Traditional electrochemical sensors typically use customized substrates, requiring cumbersome positioning, fixing, and sealing steps during assembly, which is time-consuming and results in a complex overall structure, hindering portability and rapid on-site detection. Furthermore, existing sensors often have low matching degrees between reaction volume and substrate structural parameters, leading to poor repeatability of detection results; electrode mounting and fixing methods also suffer from insufficient stability and poor sealing performance, affecting the sensor's lifespan and detection accuracy. Summary of the Invention

[0003] This application aims to solve one of the aforementioned technical problems in the prior art. Therefore, embodiments of this application provide an electrochemical sensor.

[0004] This application also provides a method for fabricating an electrochemical sensor.

[0005] According to an embodiment of the first aspect of this application, an electrochemical sensor is provided, including a pipette tip having a pipetting channel, the end of the pipette tip being the inlet of the pipetting channel, and a through hole being provided on the outer side of the pipette tip, the through hole penetrating both sides of the pipette tip and communicating with the pipetting channel. A fixing unit includes a through hole and a slot. The through hole passes through the center of the fixing unit, and the slots are symmetrically arranged on both sides of the fixing unit with the central axis of the through hole as the center. The slots communicate with the through hole. The fixing unit is sleeved on the pipette tip through the through hole. The through hole is directly opposite the slot. The two ends of the through hole are provided with a first sealing structure to fix the fixing unit to the pipette tip. The sensing element is inserted into the slot, and the electrode reaction area of ​​the sensing element is located in the slot. A second sealing structure is provided at the entrance of the slot to form a reaction chamber in the fixing unit.

[0006] The aforementioned electrochemical sensor has at least the following advantages: This application constructs a sensor using a pipette tip as a substrate, replacing the traditional customized substrate. The structural design is simple and the materials are readily available. The assembly process involves fitting a fixing unit onto the pipette tip with a through hole, adjusting the slot of the fixing unit to be parallel to the central axis of the through hole, sealing both ends of the through hole at the connection between the fixing unit and the pipette tip using a first sealing structure, inserting the end of the sensing element with the electrode reaction area into the slot of the fixing unit, and sealing the entrance of the slot with a second sealing structure. The resulting reaction chamber allows the solution to react in the reaction area without interference. The entire assembly process of the electrochemical sensor is simple, requiring no complex positioning and sealing processes, significantly shortening the assembly time. At the same time, the sensor is small in size, making it easy to carry and quickly detect on-site.

[0007] According to the electrochemical sensor described in the first aspect of this application, the sensing element includes a substrate, and three electrode units formed of a conductive carbon paste layer are disposed on one side of the substrate. A gold nanolayer and a platinum / copper nanolayer are sequentially disposed on the electrode units.

[0008] According to the electrochemical sensor described in the first aspect of this application, anaerobic adhesive is applied to the gap between the end of the perforation and the pipette tip to form the first sealing structure, and anaerobic adhesive is applied to the inlet of the slot to form the second sealing structure.

[0009] According to an embodiment of the second aspect of this application, a method for fabricating an electrochemical sensor is provided, comprising the following steps: ultrasonically cleaning a pipette tip with deionized water and then drying it for later use; The fixing unit is fitted onto the pipette tip with the through hole. After adjusting the slot of the fixing unit to be parallel to the central axis of the through hole, anaerobic adhesive is applied to the connection between the fixing unit and the pipette tip to seal both ends of the through hole. Electrode units are formed on the substrate by screen printing. After adjusting the reaction area of ​​the electrode unit, gold nanolayers and platinum / copper nanolayers are formed sequentially on the surface of the electrode unit by electrodeposition. Insert the treated substrate with the electrode reaction area into the slot of the fixing unit, and apply anaerobic adhesive to the entrance of the slot to seal and fix it.

[0010] According to the method for fabricating an electrochemical sensor according to the second aspect of this application, before the gold nanolayer is formed, a gold solution with a concentration of 1 mM is prepared, wherein 7.88 mg of chloroauric acid and 17.65 mg of sodium citrate are added to 20 ml of ultrapure water and ultrasonically vibrated at room temperature for 10 ± 2 minutes to obtain a solution containing gold.

[0011] According to the method for fabricating an electrochemical sensor according to the second aspect of this application, before the platinum / copper nanolayer is formed, a platinum-copper solution with a solution concentration of 2mM is prepared, wherein 5.38mg of copper chloride and 16.39mg of chloroplatinic acid are added to 20ml of 0.5M sulfuric acid solution and ultrasonically vibrated at room temperature for 10±2 minutes to obtain a solution containing platinum / copper.

[0012] According to the method for fabricating an electrochemical sensor as described in the second aspect of this application, during the deposition process, a substrate with electrode units is placed in a prepared gold solution and electrodeposited for a first preset time. Then, the substrate is removed, cleaned with pure water, and placed in a prepared platinum / copper solution and electrodeposited for a second preset time.

[0013] According to the method for fabricating an electrochemical sensor as described in the second aspect of this application, during deposition in a gold solution, electrodeposition is performed at a constant potential of 0 mV for 60 s.

[0014] According to the method for fabricating an electrochemical sensor as described in the second aspect of this application, during platinum / copper solution deposition, deposition is performed at a potential of -0.3V for 120s.

[0015] According to the method for fabricating an electrochemical sensor as described in the second aspect of this application, after the gold nanolayer is formed, the surface of the electrode unit of the substrate is observed by scanning electron microscopy to see if the gold nanoparticles have been successfully attached. After confirming that the gold nanoparticles have been successfully attached, the platinum / copper nanolayer is electrodeposited. After the platinum / copper nanolayer is electrodeposited, it is necessary to observe and characterize it by scanning electron microscopy.

[0016] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0017] The present application will be further described below with reference to the accompanying drawings and embodiments; Figure 1 This is a schematic diagram of the structure of the electrochemical sensor according to an embodiment of this application; Figure 2 This is a schematic diagram of the base component in an embodiment of this application; Figure 3 This is an observation image of an embodiment of this application where no gold nanolayer has been electrodeposited; Figure 4 This is an observation image of the electrodeposited gold nanolayer in the embodiments of this application; Figure 5 This is an observation image of the electrodeposited platinum / copper nanolayer in the embodiments of this application; Figure 6 This is a cyclic voltammetry curve of an electrochemical sensor test in an embodiment of this application; Figure 7 This is another cyclic voltammetry curve of the electrochemical sensor test in the embodiments of this application; Figure 8 This is the performance evaluation curve of the electrochemical sensor in the embodiments of this application. Figure 1 ; Figure 9 This is the performance evaluation curve of the electrochemical sensor in the embodiments of this application. Figure 2 ; Figure 10 This is a test diagram of the anti-interference capability of the electrochemical sensor in the embodiments of this application.

[0018] Reference numerals: handle 100, second frustum 200, sensing element 300, base 310, working electrode 320, counter electrode 330, reference electrode 340, insulating tape 350, fixing unit 400, first frustum 500. Detailed Implementation

[0019] This section will describe in detail the specific embodiments of this application. Preferred embodiments of this application are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of this application, but they should not be construed as limiting the scope of protection of this application.

[0020] In the description of this application, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and 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 this application.

[0021] In the description of this application, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0022] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0023] Reference Figure 1 and Figure 2The electrochemical sensor in this application embodiment includes a pipette tip, a fixing unit 400, and a sensing element 300.

[0024] The pipette tip is equipped with a pipetting channel, the end of which is the inlet of the pipetting channel. A through hole is provided on the outside of the pipette tip, which runs through both sides of the pipette tip and connects to the pipetting channel.

[0025] The fixing unit 400 includes a through hole and a slot. The through hole passes through the center of the fixing unit 400, and the slot is symmetrically arranged on both sides of the fixing unit 400 with the central axis of the through hole as the center. The slot communicates with the through hole. The fixing unit 400 is sleeved on the pipette tip through the through hole. The through hole is directly opposite the slot. The two ends of the through hole are provided with a first sealing structure to fix the fixing unit 400 to the pipette tip.

[0026] After the sensor 300 is inserted into the slot, the electrode reaction area of ​​the sensor 300 is located in the slot, and a second sealing structure is provided at the entrance of the slot to form a reaction chamber inside the fixing unit 400.

[0027] This application constructs a sensor using a pipette tip as a substrate, replacing the traditional customized substrate. The structural design is simple and the materials are readily available. The assembly process involves fitting a fixing unit 400 onto the pipette tip with a through hole, adjusting the slot of the fixing unit 400 to be parallel to the central axis of the through hole, and sealing both ends of the through hole at the connection between the fixing unit 400 and the pipette tip using a first sealing structure. The end of the sensing element 300 with the electrode reaction area is inserted into the slot of the fixing unit 400, and a second sealing structure is set at the entrance of the slot to seal the entrance of the slot. The resulting reaction chamber allows the solution to react in the reaction area without interference. The entire assembly process of the electrochemical sensor is simple, requiring no complex positioning and sealing processes, which greatly shortens the assembly time. At the same time, the sensor is small in size, easy to carry, and allows for rapid on-site detection.

[0028] The pipette tip includes a first frustum 500, a second frustum 200, and a handle 100 connected to each other. The larger diameter end of the first frustum 500 is connected to the smaller diameter end of the second frustum 200. The handle 100 is located at the other end of the second frustum 200. The inlet is located at the other end of the first frustum 500, and the through hole is located on the second frustum 200.

[0029] Anaerobic adhesive is applied to the gap between the end of the perforation and the pipette tip to form a first sealing structure, and anaerobic adhesive is applied to the entrance of the slot to form a second sealing structure.

[0030] In some other embodiments, the sensing element 300 includes a base 310, on one side of which are three electrode units formed of a conductive carbon paste layer, and gold nanolayers and platinum / copper nanolayers are sequentially disposed on the electrode units.

[0031] Specifically, such as Figure 2 As shown, the three electrode units are the counter electrode 330, the reference electrode 340, and the working electrode 320. The electrodes are fabricated using laboratory conductive carbon paste and screen-printed (SPE) electrodes. Insulating tape 350 is used to separate the reaction areas of electrode 330 to ensure that the reaction areas of each electrode are identical. Au nanoparticles are then deposited on the electrode surface using electrodeposition. Pt and Cu alloy nanoparticles are then deposited using the same method. This process yields the desired Pt-Cu NPs / Au / SPE. This electrode exhibits better detection limits, sensitivity, and linearity for nitrite detection compared to SPE.

[0032] In this embodiment, the substrate 310 is a PET board. Laboratory conductive carbon paste is printed onto the PET board, and then cut to the required three electrodes using scissors. Figure 2 As shown, insulating tape 350 is then attached above the electrode to make the reaction area of ​​the working electrode 320 a circular area.

[0033] This application also provides a method for fabricating an electrochemical sensor, comprising the following steps: The pipette tips were ultrasonically cleaned with deionized water and then dried for later use. Specifically, 5ml capacity polypropylene pipette tips were selected, ultrasonically cleaned with deionized water for 10 minutes, and then dried. Their structural parameters are as follows: the smaller diameter end of the first frustum 500 has a diameter of 0.25cm, the smaller diameter end has a diameter of 0.92cm, and the length is 4.07cm; the smaller diameter end of the second frustum 200 has a diameter of 0.92cm, the smaller diameter end has a diameter of 1.08cm, the length is 9.22cm, and the thickness is 0.35mm.

[0034] The fixing unit 400 is fitted onto the pipette tip at the position with the through hole. After adjusting the slot of the fixing unit 400 to be parallel to the central axis of the through hole, anaerobic adhesive is applied to the connection between the fixing unit 400 and the pipette tip to seal both ends of the through hole. Specifically, a polycarbonate sphere with an outer diameter of 2cm and a wall thickness of 0.15mm is used as the fixing unit 400. The center position of the sphere is marked on the surface of the sphere. The sphere is aligned with the first frustum 500, so that the distance between the center of the sphere and the larger diameter end of the first frustum 500 is 7.8cm. A methacrylate-based anaerobic adhesive is applied to the connection between the sphere and the second frustum 200 segment. It is left to stand for 10 minutes to cure, thus completing the fixing and sealing of the sphere.

[0035] Electrode units are formed on substrate 310 by screen printing. After adjusting the reaction area of ​​the electrode unit, gold nanolayers and platinum / copper nanolayers are sequentially formed on the surface of the electrode unit by electrodeposition.

[0036] Insert the prepared substrate 310 with the electrode reaction area into the slot of the fixing unit 400, and apply anaerobic adhesive to the entrance of the slot to seal and fix it.

[0037] The process involves screen printing conductive carbon paste (70% solid content) onto a 0.05mm thick polyimide film using a 250-mesh screen. Three rectangular electrode units, each 1.2cm long, 0.8cm wide, and 0.08mm thick, are then fabricated. The working electrode 320 has a lead width of 0.2cm and a reaction area size of 1.0cm × 0.8cm. The counter electrode 330 and reference electrode 340 have the same dimensions as the working electrode 320, with leads located on either side. A 0.03mm thick polyimide insulating tape 350, covering an area of ​​0.8cm², is adhered below the working electrode 320 (outside the reaction area), compacted, and excess tape is trimmed.

[0038] Two symmetrical rectangular grooves (1.25cm×0.8cm×0.1mm) and two holes (radii 5mm and 4.8mm, with the center distance between the holes matching the center distance between the rectangular grooves) are laser-cut on the top of the sphere. The prepared sensor 300 is inserted into the rectangular groove, ensuring that the electrode reaction area faces the inside of the sphere. A methacrylate-based anaerobic adhesive is applied to the gap between the electrode and the slot, and allowed to stand for 8 minutes to cure, thus completing the fixation and sealing of the sensor 300.

[0039] After the electrochemical sensor is assembled, the pipette tip is connected to the pipette, and the liquid to be tested is drawn into the pipette tip through the pipette. Then, the three electrode units are connected to the electrochemical workstation, and the amperometry-time curve is used for detection to obtain a current value. Substituting the current value into the relevant linear equation, the concentration of nitrite can be obtained, thus realizing the detection of nitrite.

[0040] In some embodiments, a gold solution with a concentration of 1 mM is prepared before the gold nanolayer is formed. Specifically, 7.88 mg of chloroauric acid and 17.65 mg of sodium citrate are added to 20 ml of ultrapure water and ultrasonically vibrated at room temperature for 10 ± 2 minutes to obtain a solution containing gold.

[0041] Before forming the platinum / copper nanolayer, a platinum / copper solution with a concentration of 2 mM was prepared. Specifically, 5.38 mg of copper chloride and 16.39 mg of chloroplatinic acid were added to 20 ml of 0.5 M sulfuric acid solution and ultrasonically vibrated at room temperature for 10 ± 2 minutes to obtain a solution containing platinum / copper.

[0042] During the deposition process, the substrate 310 with electrode units is placed in a prepared gold solution and electrodeposited for a first preset time. Then, the substrate 310 is removed, cleaned with pure water, and placed in a prepared platinum-copper solution and electrodeposited for a second preset time.

[0043] Specifically, using the electrodeposition method, the SPE (substrate 310 with electrode units) is placed in an AuNPs solution (i.e., gold solution) and electrodeposited for 60 seconds at a constant potential of 0 mV. After being removed and washed with pure water, it is placed in a Pt-Cu NPs solution (i.e., platinum copper solution) and deposited for 120 seconds at a potential of -0.3V to obtain Pt-Cu NPs / Au / SPE (i.e., the complete sensing element 300).

[0044] Among them, the Pt-Cu NPs / Au / SPE composition is called "Pt-Cu nanoparticle modified gold (Au) screen-printed electrode (SPE)". It is a composite electrode obtained by electrodepositing platinum-copper (Pt-Cu) alloy nanoparticles (NPs) onto the surface of gold (Au) screen-printed electrode (SPE) through a specific process.

[0045] The Pt-Cu NPs / Au / SPE electrode is a composite electrode formed by electrodepositing Au nanoparticles and Pt-Cu alloy nanoparticles onto the surface of an SPE electrode, rather than the preparation of a new material.

[0046] After the gold nanolayer is formed, the surface of the electrode unit of the substrate 310 is observed by scanning electron microscopy to see if the gold nanoparticles are successfully attached. After confirming that the gold nanoparticles are successfully attached, the platinum / copper nanolayer is electrodeposited. After the platinum / copper nanolayer is electrodeposited, it is necessary to observe and characterize it by scanning electron microscopy.

[0047] For further comparison, screen-printed electrodes containing AuNPs (Au NPs / SPE) and screen-printed electrodes containing Pt / Cu NPs (Pt-Cu NPs / SPE) were prepared.

[0048] SPE and Au NPs / SPE were characterized by scanning electron microscopy, such as Figure 3 , 4 As shown, Figure 4 The surface area of ​​the electrode is greater than Figure 3 The SPE surface showed several clusters of spherical particles. XRD analysis of the electrode 330 surface revealed that Au NPs and Pt-Cu NPs were successfully loaded onto the electrode surface. Figure 5 As shown, this indicates that Pt-Cu NPs / Au / SPE was successfully prepared.

[0049] The sensing element 300 of this application has a larger and more uniform electrode reaction area: compared with traditional narrow and long electrodes, the larger reaction area makes the current distribution more uniform and improves the sensitivity of the electrode, especially when detecting low concentration substances (such as nitrite), it can obtain more accurate signals.

[0050] Lower electrode interference: Optimized electrode spacing avoids mutual interference caused by overly close electrodes. This invention is better suited for detecting complex matrices in real-world environments, ensuring signal stability and accuracy.

[0051] Support for multiplex detection: Due to the greater flexibility and adaptability of the electrode design in this application, the number of electrodes can be easily expanded to support multiple analytical needs. For example, different substances can be monitored simultaneously on the same device, or rapid detection of different target substances can be achieved by changing electrodes.

[0052] The optimized structural design meets the portability requirements: Compared with the traditional electrode structure, the electrode designed in this application is more compact and easier to assemble, which meets the needs of portable sensors for rapid on-site detection.

[0053] Electrochemical tests were performed on the fabricated sensing element 300 using a 0.1 MPa h = 7.4 PBS solution as the detection solution. CV detection was employed, with a potential range of 0–1 V. The electrochemical responses of bare SPE (substrate 310 with electrode units), Cu NPs / SPE (substrate 310 with electrode deposited copper nanoparticles), Au NPs / SPE (substrate 310 with electrode deposited gold nanoparticles), Pt NPs / SPE (substrate 310 with electrode deposited platinum nanoparticles), Pt-Cu NPs / SPE (substrate 310 with electrode deposited platinum / copper), and Pt-Cu NPs / Au / SPE (substrate 310 with electrode deposited gold-platinum / copper) in the aforementioned detection solution were tested. The results are attached. Figure 6 The cyclic voltammetry curves shown indicate that Pt-Cu NPs / Au / SPE exhibits the strongest electrocatalytic activity and stability at potentials of 0.7–1 V, with the horizontal axis representing voltage / V and the vertical axis representing current / µA.

[0054] Among them, bare SPE is also called bare screen-printed electrode, Cu NPs / SPE is also called Cu nanoparticle modified screen-printed electrode, Au NPs / SPE is also called Au nanoparticle modified screen-printed electrode, and Pt NPs / SPE is also called Pt nanoparticle modified screen-printed electrode.

[0055] PBS solution with a pH of 0.1 Mp = 7.4 (containing 1 mM nitrite) was used as the detection solution, and CV detection was performed with a potential range of 0–1 V. The electrochemical responses of bare SPE (substrate 310 with electrode units), Cu NPs / SPE (substrate 310 with electrode deposited copper nanoparticles), Au NPs / SPE (substrate 310 with electrode deposited gold nanoparticles), Pt NPs / SPE (substrate 310 with electrode deposited platinum nanoparticles), Pt-Cu NPs / SPE (substrate 310 with electrode deposited platinum / copper), and Pt-Cu NPs / Au / SPE (substrate 310 with electrode deposited gold-platinum / copper) in the above detection solutions were tested, and the results are attached. Figure 7 The cyclic voltammetry curves shown indicate that Pt-Cu NPs / Au / SPE exhibits the strongest electrocatalytic activity and stability at potentials of 0.7–1 V, with the horizontal axis representing voltage / V and the vertical axis representing current / µA.

[0056] In some embodiments, deposition time optimization was performed: the deposition time of AuNPs was optimized by electrodepositing at 15s, 30s, 60s, 120s, and 240s, respectively, and the performance of the electrochemical sensor was tested. 60s was determined to be the optimal electrodeposition time. The deposition time of Pt-Cu NPs was optimized by electrodepositing at 30s, 60s, 120s, 240s, and 480s, respectively, and the sensor performance was tested. 120s was determined to be the optimal electrodeposition time.

[0057] Pt-Cu NPs ratio optimization: Pt-Cu NPs solutions with ratios of (4:0), (3:1), (2:2), (1:3), and (0:4) were prepared for electrodeposition, and the sensor performance was tested. The optimal Pt-Cu NPs ratio was determined to be (2:2), where the ratio refers to the molar concentration ratio.

[0058] Sensor performance evaluation: The sensor was evaluated using the it curve method at an operating potential of 0.8V. The results showed that the linear range of the sensor can be divided into two segments: one segment is the lower concentration range from 1μM to 1000μM. Figure 8 The linear equation is y = 0.01598x + 0.13577, R0 2 =0.99, another segment is the higher concentration range from 2mM to 8mM, the linear equation is y=0.00521x+11.2018, R 2 =0.99, and the detection limit of the sensor is 0.11 μM. Among these, Figure 9 It can be seen that the electrochemical sensor of this application has a large linear range, from 1 μM to 8000 μM.

[0059] Sensor anti-interference test: Interference ions including 0.5 mM sodium chloride, copper chloride, sodium acetate, magnesium chloride, potassium nitrate, sodium phosphate, potassium iodate, potassium chloride, copper sulfate, sodium nitrate, and calcium chloride were added to 0.1 M PBS (pH 7.4) solution. The sensor's detection effect on 0.05 mM nitrite was tested. The results showed that the interfering ions had almost no effect on the detection, indicating good anti-interference performance of the sensor. (See attached diagram) Figure 10 The results are shown.

[0060] Real sample testing: The electrochemical sensor prepared in this application was used to spike pure water, cola, milk, and river water. The experimental data are shown in the table below:

[0061] The experimental data shown in the table above indicate that the recovery rate of nitrite in some beverages and environmental water samples is 96.43%-103.75%, demonstrating the sensor's good detection effect on real samples. The sensor has high detection accuracy and good application prospects.

[0062] The beneficial effects of this application are: Structural and assembly advantages: This application uses a pipette tip as a substrate to construct a sensor, replacing the traditional customized substrate. The structural design is simple and the materials are readily available. The assembly process can be completed through simple steps such as opening holes, bonding, and electrode insertion and fixing. There is no need for complicated positioning and sealing processes, which greatly shortens the assembly time. At the same time, the overall size of the sensor is small, making it easy to carry and quickly detect on site.

[0063] Improved detection performance: Pt-Cu NPs / Au / SPE was prepared by sequentially loading Au nanoparticles and Pt-Cu nanoparticles onto the surface of SPE via electrodeposition. Compared with traditional SPE and single metal nanoparticle modified electrodes, this electrode has a lower detection limit (0.11 μM), higher sensitivity, and a wider linear range (1 μM-1000 μM, 2 mM-8 mM) for nitrite, enabling accurate quantitative detection of nitrite.

[0064] Stability and sealing optimization: The sensor's sphere and electrodes are fixed and sealed using methacrylate-based anaerobic adhesive (or hot melt adhesive), which improves the sensor's structural stability and sealing performance, reduces detection errors caused by problems such as loose electrodes and leakage, and extends the sensor's service life.

[0065] Strong anti-interference and practical application capabilities: The sensor prepared in this application is almost unaffected in the presence of various interfering ions such as sodium chloride and copper chloride, and has good anti-interference performance. At the same time, the accuracy of the spiked detection results of real samples such as pure water, cola, milk and river water is high, indicating that it has good application prospects in practical scenarios such as food testing and environmental monitoring.

[0066] Advantages in manufacturing cost and flexibility: The pipette tips and screen printing materials used in sensor manufacturing are common consumables with low cost; and the specifications of the pipette tips can be replaced according to needs (1ml, 5ml, 10ml, etc.), and the size of the sphere cavity and electrode chip can be dynamically adjusted, which has strong customization flexibility and can adapt to different detection needs.

[0067] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application.

Claims

1. An electrochemical sensor, characterized by: The application relates to a fixed unit for a pipette tip. The fixed unit comprises a through hole and a clamping groove, the through hole penetrates the center of the fixed unit, the clamping groove is symmetrically arranged on both sides of the fixed unit with the center axis of the through hole as the center, the clamping groove is communicated with the through hole, and the fixed unit is sleeved on the pipette tip through the through hole. The through hole is opposite to the clamping groove, and the first sealing structure is arranged at both ends of the through hole to fix the fixed unit on the pipette tip. The inductive piece is inserted into the clamping groove, and the electrode reaction area of the inductive piece is in the clamping groove, and the second sealing structure is arranged at the inlet of the clamping groove to form a reaction cavity in the fixed unit.

2. The electrochemical sensor of claim 1, wherein: The fixed unit comprises a base piece, one side of the base piece is provided with three electrode units formed by a conductive carbon paste layer, and a gold nano layer and a platinum / copper nano layer are sequentially arranged on the electrode units.

3. The electrochemical sensor of claim 1, wherein: Anaerobic glue is applied at the gap between the end of the through hole and the pipette tip to form the first sealing structure, and anaerobic glue is applied at the inlet of the clamping groove to form the second sealing structure.

4. A method of fabricating an electrochemical sensor based on the sensor of claim 2, characterized by, The application further discloses a preparation method of the fixed unit. The pipette tip is ultrasonically cleaned with deionized water and then dried for standby use. The fixed unit is sleeved on the position of the pipette tip with the through hole, the clamping groove of the fixed unit is adjusted to be parallel to the center axis of the through hole, anaerobic glue is applied at the joint of the fixed unit and the pipette tip to seal both ends of the through hole. The electrode units are formed on the base piece by means of silk screen printing, the reaction area of the electrode units is adjusted, and then a gold nano layer and a platinum / copper nano layer are sequentially formed on the surface of the electrode units by means of electrodeposition. One end of the base piece with the electrode reaction area is inserted into the clamping groove of the fixed unit, and anaerobic glue is applied at the inlet of the clamping groove to seal and fix.

5. The method of claim 4, wherein: Before the gold nano layer is formed, a gold solution with a solution concentration of 1mM is prepared, 7.88mg of chloroauric acid and 17.65mg of sodium citrate are added into 20ml of ultrapure water, and ultrasonic oscillation is carried out at room temperature for 10+2 minutes to obtain a gold-containing solution.

6. The method of claim 5, wherein: Before the platinum / copper nano layer is formed, a platinum / copper solution with a solution concentration of 2mM is prepared, 5.38mg of cupric chloride and 16.39mg of chloroplatinic acid are added into 20ml of 0.5M sulfuric acid solution, and ultrasonic oscillation is carried out at room temperature for 10+2 minutes to obtain a platinum / copper-containing solution.

7. The method of claim 6, wherein: During the deposition process, the base piece with the formed electrode units is placed into the prepared gold solution to deposit for a first preset time, then the base piece is taken out, cleaned with pure water, and then placed into the prepared platinum / copper solution to deposit for a second preset time.

8. The method of claim 7, wherein: During the deposition in the gold solution, electrodeposition is carried out at 0mv constant potential for 60s.

9. The method of claim 7, wherein: During the deposition in the platinum / copper solution, deposition is carried out at a potential of-0.3V for 120s.

10. The method of claim 6, wherein: After the gold nano layer is formed, whether the gold nano is successfully attached to the electrode unit surface of the base is observed by a scanning electron microscope, and after confirming that the gold nano is successfully attached, electrodeposition of the platinum / copper nano layer is performed, and after the electrodeposition of the platinum / copper nano layer is completed, the platinum / copper nano layer is observed by the scanning electron microscope.

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