Bifunctional zinc ion selective microelectrode, ultramicro electrochemical sensor as well as preparation method and application of bifunctional zinc ion selective microelectrode and ultramicro electrochemical sensor

Abstract

The invention belongs to the technical field of analysis and detection, and particularly relates to a bifunctional zinc ion selective microelectrode, an ultramicro electrochemical sensor, a preparation method and application. The method comprises the following steps: preparing a platinum ultramicro disc electrode through the steps of laser drawing, polishing, electrode extraction and the like, doping a multi-walled carbon nanotube into a zinc ion selective membrane solution, and curing to form a membrane to obtain a target microelectrode; according to the ultramicro electrochemical sensor, the microelectrode is used as a core functional part and is matched with a reference electrode and an auxiliary electrode to form a three-electrode system. The diameter of the electrode is 25 [mu] m, the RG value is about 3, the linear correlation coefficient of zinc ions reaches up to 0.997, and the electrode has excellent selectivity, conductivity and position control accuracy. High-resolution monitoring of the concentration of zinc ions in a negative electrode interface in-situ micro-area under different electrolyte additive systems and different charge-discharge multiplying powers in the charge-discharge process of the aqueous zinc ion battery can be realized through a potential response mode of a scanning electrochemical microscope.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microfluidic device manufacturing, and particularly relates to a bifunctional zinc ion selective microelectrode, an ultramicro electrochemical sensor, and a preparation method and application thereof. BACKGROUND

[0002] Zinc also has important applications in metal corrosion, energy chemistry, catalysis, etc. The concentration distribution of zinc ions in the interface microregion of zinc metal is closely related to the growth process of zinc dendrites in the interface of zinc ion batteries and metal corrosion. In-situ measurement of the concentration distribution of zinc ions in the interface microregion of zinc metal can provide information such as the corrosion dissolution rate of the zinc metal microregion and the concentration diffusion of Zn 2+ at the interface. 2+ Therefore, in-situ detection of the concentration of zinc ions in the interface microregion has important scientific significance for better understanding the biological metabolism, the corrosion of the interface microregion of zinc metal, and the growth mechanism of zinc dendrites in the interface of zinc ion batteries. In the measurement of the concentration of ions in the interface microregion by the traditional microregion ion selective electrode, the electrode potential is usually used to detect the concentration of a specific chemical species on the substrate, but the electrode potential has no feedback effect on the probe-substrate distance, so the precise control of the probe-substrate position cannot be achieved during the experiment.

[0003] At present, there are methods that can be used for monitoring the concentration of Zn 2+ , such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), ultraviolet-visible (UV-Vis) spectroscopy, and flame atomic absorption spectrometry (FAAS). These analysis techniques can determine the concentration of Zn 2+ , but the experiment involves complex analysis tools, and the solution must be taken out for measurement, so in-situ online monitoring of the concentration distribution of Zn 2+ in the interface microregion of the metal cannot be achieved during the experiment. Although fluorescence spectroscopy can achieve in-situ online monitoring of the concentration distribution of Zn 2+ , the experiment usually requires the addition of a fluorescent molecular probe to the solution, the fluorescent molecular probe is generally an organic molecule, which may interfere with the experimental process, and the service life of the fluorescent molecule is generally short, making it difficult to achieve long-term in-situ online monitoring. SUMMARY

[0004] Therefore, the application provides a bifunctional zinc ion selective microelectrode, an ultramicro electrochemical sensor, and a preparation method and application thereof, which can simply and quickly prepare a bifunctional zinc ion ultramicro sensor with excellent response performance to zinc ions for detecting the concentration of Zn 2+ in the interface microregion under precise control of the probe-substrate position.

[0005] To achieve the above object, the application adopts the following technical solutions: The first technical objective of this invention is to provide a method for preparing a bifunctional zinc ion-selective microelectrode, specifically comprising the following steps: 1) Take a platinum wire with a diameter of 25 µm and a capillary glass tube with an outer diameter of 0.5 mm to 2.0 mm and an inner diameter of 0.1 mm to 0.5 mm, and place the wire in the hollow cavity of the capillary glass tube. 2) Stretch the capillary glass tube to reduce the diameter at the middle position of the capillary glass tube. When the inner wall at the middle position of the capillary glass tube is in contact with the metal wire, break the capillary glass tube from the middle position to obtain two platinum microelectrodes. 3) Insert a wire into the electrode from the end of the capillary glass tube, connect the wire to the metal wire inside the electrode, and then seal the end of the capillary glass tube. 4) Tetrabutylthiuram disulfide, high molecular weight polyvinyl chloride, o-nitrophenyl octyl ether, and sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate are mixed in a certain proportion and dissolved in tetrahydrofuran to prepare a zinc ion selective membrane solution. 5) Multi-walled carbon nanotubes are uniformly dispersed in a zinc ion selective membrane solution using an ultrasonic method. The dispersed mixture is then drop-coated onto the polished tip of a platinum microelectrode and left to stand in air at room temperature until the mixture at the electrode tip solidifies to form a uniform thin film.

[0006] It should be noted that most methods involve complex analytical procedures, are expensive, and are not suitable for real-time in-situ micro-area monitoring of interfaces. This invention employs ultra-micro ion sensor electrodes with micrometer-scale dimensions, combined with in-situ micro-area measurement technology, enabling experimental monitoring of Zn in interfacial micro-areas. 2+ In-situ online monitoring of concentration distribution.

[0007] Furthermore, existing ion-selective microelectrodes do not respond to the probe-substrate position, making precise control of the probe position difficult in experiments. This invention dops the ion-selective membrane with a certain mass ratio of multi-walled carbon nanotubes, significantly improving the conductivity of the ion-selective membrane and enabling the ultramicro ion-selective electrode to possess both potential and current responses.

[0008] This invention addresses the problems of insufficient selectivity, poor conductivity, and difficulty in achieving in-situ high-resolution monitoring of interfacial micro-regions in existing zinc ion monitoring electrodes. The invention first prepares a platinum ultramicro disk electrode through laser pulling, polishing, and electrode extraction. Then, multi-walled carbon nanotubes are doped into a zinc ion-selective film solution in a specific ratio, and the film is solidified to obtain the target microelectrode. The ultramicro electrochemical sensor uses this microelectrode as the core functional component, combined with a reference electrode and an auxiliary electrode to form a three-electrode system. The electrode of this invention has a diameter of 25 μm, an RG value of approximately 3, and a linear correlation coefficient with zinc ions as high as 0.997, exhibiting excellent selectivity, conductivity, and precise position control. It can achieve high-resolution monitoring of the in-situ micro-region zinc ion concentration at the negative electrode interface under different electrolyte additive systems and different charge / discharge rates during the charging and discharging process of aqueous zinc-ion batteries using scanning electrochemical microscopy potential response mode. This provides key technical support for revealing the dendrite growth mechanism of zinc negative electrodes, optimizing electrolyte formulations, and electrode modification strategies, and has broad application prospects.

[0009] Optionally, when preparing the zinc ion selective membrane solution, the main ingredients are weighed according to the following mass fraction ratios, and the sum of the mass fractions of the main ingredients is 100%: The mixture consists of 6%-9% tetrabutylthiuram disulfide, 30%-35% polyvinyl chloride, 50%-60% o-nitrophenyl octyl ether, and 0.3%-1% sodium tetra(3,5-bis(trifluoromethyl)phenyl)borate. To facilitate control of the solution concentration, 0.1-0.5 g of the total mass of the above-mentioned mixed main materials can be used for subsequent dissolution operations.

[0010] Optionally, the mass ratio of multi-walled carbon nanotubes to zinc ion selective membrane solution is 1:5 to 1:20.

[0011] Specifically, the core innovations of this invention are explained from the aspects of preparation process and performance: 1) By adjusting the laser drawing parameters, the size of the platinum microelectrode wire can be precisely controlled. Electrodes prepared by sealing carbon fiber wires with capillary glass tubes have long usable lengths and high detection accuracy; they are also easy to polish to reduce RG (reactive protein ratio), have small electrode sizes, and are less likely to collide with samples during testing. After loading a zinc ion selective film, bifunctional zinc ion selective electrodes of different sizes can be prepared, enabling in-situ high-resolution monitoring of zinc ions in micro-regions of biological cells or metal interfaces. This invention can easily prepare bifunctional zinc ion selective microelectrodes with controllable size, low RG, good sealing performance, and excellent zinc ion response, which is of great significance for high-resolution spatial detection of zinc ion concentration distribution in micro-regions.

[0012] 2) The bifunctional zinc ion-selective microelectrode prepared in this invention exhibits excellent linear response and stability to zinc ions. Combined with micro-area scanning probe technology, it can be used for in-situ high-resolution online monitoring of zinc ions in micro-areas within cells and at metal interfaces, showing broad application prospects in biochemistry, metal corrosion, and energy chemistry. Furthermore, the introduction of multi-walled carbon nanotubes in this invention can increase the conductivity of the ion-selective membrane. Optimizing the appropriate amount of multi-walled carbon nanotubes can improve the response slope of the ion-selective electrode within a certain range, enabling the ion-selective electrode to have both potential and current responses, allowing for precise control of the probe-substrate position in experiments.

[0013] The second technical objective of this invention is to provide an application of a bifunctional zinc ion selective microelectrode prepared as described above in the analysis and detection of zinc ions.

[0014] Specifically, it relates to the field of zinc-ion battery negative electrode reaction mechanism analysis, and is particularly applicable to the dynamic in-situ determination of zinc ion concentration distribution in various zinc-ion energy storage devices such as aqueous zinc-ion batteries and non-aqueous zinc-ion batteries, within the 0-100 μm micro-region of the negative electrode (such as metallic zinc negative electrode, zinc-based alloy negative electrode, zinc composite negative electrode) interface during charge-discharge cycles and resting.

[0015] The bifunctional zinc ion-selective microelectrode is used for qualitative and quantitative detection of zinc ions, and is also used for in-situ measurement of Zn in the interfacial microregion. 2+ Concentration distribution.

[0016] Specifically, the bifunctional zinc ion selective microelectrode prepared by the above method is used as the working electrode, and a platinum wire counter electrode and an Ag / AgCl reference electrode are combined to construct a three-electrode in-situ detection system. By combining the current response mode of scanning electrochemical microscopy, the current signal during the movement of the working electrode along the z-axis is recorded. According to the standard approximation curve, the precise control of the interface position between the bifunctional zinc ion selective microelectrode and the negative electrode of the zinc ion battery can be achieved. The bifunctional zinc ion selective microelectrode can realize the quantitative analysis of the zinc ion concentration at the interface under precise position control.

[0017] Furthermore, the bifunctional zinc ion-selective microelectrode can be used for in-situ measurement of Zn in interfacial microregions. 2+ Concentration distribution, the specific operation is as follows: Using the aforementioned three-electrode in-situ detection system, combined with the potential response mode of scanning electrochemical microscopy, the working electrode is controlled to move three-dimensionally at a certain height near the negative electrode interface of the zinc-ion battery. Simultaneously, the response potential signal of the bifunctional zinc-ion selective microelectrode is recorded through an electrochemical workstation. Based on the pre-plotted "zinc ion concentration-response potential" calibration curve, the experimentally recorded response potential signal is converted into the zinc ion concentration of the corresponding micro-region. This allows for the acquisition of zinc ion concentration distribution data at different spatial locations (e.g., 5 μm, 10 μm...100 μm from the zinc negative electrode interface) and at different time points (e.g., 0 min, 10 min, 30 min of charging, and at the end of discharging) of the negative electrode interface. This enables in-situ high-resolution detection of the zinc ion concentration distribution in the micro-region of the zinc-ion battery negative electrode interface by the bifunctional zinc-ion selective microelectrode.

[0018] The third technical objective of this invention is to provide an ultramicro electrochemical sensor comprising a bifunctional zinc ion selective microelectrode prepared by the method described above.

[0019] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a bifunctional zinc ion selective microelectrode and its preparation method. This microelectrode, combined with scanning electrochemical microscopy, can be widely used in energy chemistry, corrosion electrochemistry, environmental chemistry and bioelectrochemistry research.

[0020] First, the introduction of multi-walled carbon nanotubes in this invention can increase the conductivity of the ion-selective membrane. Optimizing the appropriate amount of multi-walled carbon nanotubes can improve the response slope of the ion-selective electrode within a certain range, and also enable the ion-selective electrode to have both potential and current responses, allowing for precise control of the probe-substrate position in experiments.

[0021] Secondly, the bifunctional zinc ion selective microelectrode prepared by this invention has good linear response and stability to zinc ions. Combined with micro-area scanning probe technology, it can be used for in-situ high-resolution online monitoring of zinc ions in micro-areas inside cells and at metal interfaces, and has broad application prospects in biochemistry, metal corrosion and energy chemistry.

[0022] Finally, by adjusting the laser pulling parameters, this invention can obtain platinum ultramicroelectrodes of different sizes. After loading zinc ion selective films, bifunctional zinc ion selective electrodes of different sizes are obtained, enabling in-situ high-resolution online monitoring of zinc ions in micro-regions of biological cells or metal interfaces. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 An optical photograph of the tip of a zinc ion-selective microelectrode probe.

[0025] Figure 2 The cyclic voltammetry curves of the zinc ion-selective microelectrode in ferrocene methanol solution are shown.

[0026] Figure 3 The potential response diagram of the zinc ion selective microelectrode prepared in Example 1 to zinc ions.

[0027] Figure 4 The potential response of the zinc ion-selective microelectrode prepared for Comparative Example 1 to zinc ions is shown in the figure.

[0028] Figure 5 The potential response of the zinc ion-selective microelectrode prepared for Comparative Example 2 to zinc ions is shown in the figure.

[0029] Figure 6 This is an approximation curve of a zinc ion selective microelectrode on a stainless steel surface.

[0030] Figure 7 This is a spatial distribution diagram of zinc ion concentration in the micro-region of the zinc anode interface. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0033] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and technical means not specifically mentioned herein refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0034] To better illustrate the content of this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0035] Without conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of this application.

[0036] This invention discloses a method for preparing a bifunctional zinc ion selective microelectrode.

[0037] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0038] Example 1 A method for preparing a bifunctional zinc ion-selective microelectrode includes the following steps: 1. Take 25 μm platinum wire after annealing and straighten it by rolling.

[0039] 2. Take a septum-type borosilicate capillary glass tube with an outer diameter of 1.5 mm and an inner diameter of 1.0 mm, immerse it in a mixed solution of H2SO4 and H2O2 with a volume ratio of 3:1 for 30 min, wash it repeatedly with deionized water, and then dry it for later use.

[0040] 3. Place the treated platinum wire in the middle of the borosilicate capillary glass tube to ensure accurate positioning.

[0041] 4. Seal one end of the borosilicate capillary glass tube with sealing film and place it in the center of the Laser Puller P-2000 laser pulling instrument. Connect the other end to a vacuum pump. Initially adjust the pulling parameters: laser intensity 380, laser beam size 5, speed 15, delay 120, and pulling force 0, to refine the inner diameter of the glass tube to 300 μm. Adjust the parameters again: laser intensity 280, laser beam size 4, speed 15, delay 120, and pulling force 0. Manually stop after 15 seconds. At this point, the middle part of the glass tube is completely sealed to the platinum wire. Finally, cut along the middle of the glass tube to obtain a platinum microelectrode with a diameter of approximately 25 μm and a tip size of approximately 50 μm.

[0042] 5. First, polish the platinum microelectrode on sandpaper, then place it in an alumina slurry for fine polishing until the surface is mirror-like.

[0043] 6. Take a nickel wire, dip its tip in a small amount of silver paste, and insert it into the tail of the borosilicate capillary glass tube under the aid of a microscope, so that the nickel wire and the platinum wire are in close contact; then seal the tail of the glass tube with hot melt glue to fix the nickel wire.

[0044] 7. Polish the electrode again: First, it is initially polished with sandpaper, and then finely polished to a mirror finish in an alumina slurry to obtain a platinum ultra-micro disk electrode with a diameter of 25 μm and an RG value of about 3.

[0045] 8. Weigh out tetrabutylthiuram disulfide (7 mg), polyvinyl chloride (34 mg), o-nitrophenyl octyl ether (58 mg), and sodium tetra(3,5-bis(trifluoromethyl)phenyl)borate (1 mg) in a mass ratio of 7:34:58:1. Mix the above components and dissolve them in tetrahydrofuran. Stir well to prepare a zinc ion selective membrane solution.

[0046] 9. Weigh 1.0 mg of multi-walled carbon nanotubes and add them to 50 μL of the above ion-selective membrane solution. Disperse the multi-walled carbon nanotubes uniformly by ultrasonication (ultrasonic time 5 min) to obtain a mixed solution.

[0047] 10. Add the mixed solution to the probe tip and wait for the solution to solidify into a film to obtain a bifunctional zinc ion selective microelectrode with a diameter of 25 μm.

[0048] Example 2 A method for preparing a bifunctional zinc ion-selective microelectrode includes the following steps: 1. Take 25 μm platinum wire after annealing and straighten it by rolling.

[0049] 2. Take a septum-type borosilicate capillary glass tube with an outer diameter of 1.5 mm and an inner diameter of 1.0 mm, immerse it in a mixed solution of H2SO4 and H2O2 with a volume ratio of 3:1 for 30 min, wash it repeatedly with deionized water, and then dry it for later use.

[0050] 3. Place the treated platinum wire in the middle of the borosilicate capillary glass tube to ensure accurate positioning.

[0051] 4. Seal one end of the borosilicate capillary glass tube with sealing film and place it in the center of the Laser Puller P-2000 laser pulling instrument. Connect the other end to a vacuum pump. Initially adjust the pulling parameters: laser intensity 380, laser beam size 5, speed 15, delay 120, and pulling force 0, to refine the inner diameter of the glass tube to 300 μm. Adjust the parameters again: laser intensity 280, laser beam size 4, speed 15, delay 120, and pulling force 0. Manually stop after 15 seconds. At this point, the middle part of the glass tube is completely sealed to the platinum wire. Finally, cut along the middle of the glass tube to obtain a platinum microelectrode with a diameter of approximately 25 μm and a tip size of approximately 50 μm.

[0052] 5. First, polish the platinum microelectrode on sandpaper, then place it in an alumina slurry for fine polishing until the surface is mirror-like.

[0053] 6. Take a nickel wire, dip its tip in a small amount of silver paste, and insert it into the tail of the borosilicate capillary glass tube under the aid of a microscope, so that the nickel wire and the platinum wire are in close contact; then seal the tail of the glass tube with hot melt glue to fix the nickel wire.

[0054] 7. Polish the electrode again: First, it is initially polished with sandpaper, and then finely polished to a mirror finish in an alumina slurry to obtain a platinum ultra-micro disk electrode with a diameter of 25 μm and an RG value of about 3.

[0055] 8. Weigh out tetrabutylthiuram disulfide (7 mg), polyvinyl chloride (34 mg), o-nitrophenyl octyl ether (58 mg), and sodium tetra(3,5-bis(trifluoromethyl)phenyl)borate (1 mg) in a mass ratio of 7:34:58:1. Mix the above components and dissolve them in tetrahydrofuran. Stir well to prepare a zinc ion selective membrane solution.

[0056] 9. Weigh 0.8 mg of multi-walled carbon nanotubes and add them to 50 μL of the above ion-selective membrane solution. Disperse the multi-walled carbon nanotubes uniformly by ultrasonication (ultrasonic time 5 min) to obtain a mixed solution.

[0057] 10. Add the mixed solution to the probe tip and wait for the solution to solidify into a film to obtain a bifunctional zinc ion selective microelectrode with a diameter of 25 μm.

[0058] Example 3 A method for preparing a bifunctional zinc ion-selective microelectrode includes the following steps: 1. Take 25 μm platinum wire after annealing and straighten it by rolling.

[0059] 2. Take a septum-type borosilicate capillary glass tube with an outer diameter of 1.5 mm and an inner diameter of 1.0 mm, immerse it in a mixed solution of H2SO4 and H2O2 with a volume ratio of 3:1 for 30 min, wash it repeatedly with deionized water, and then dry it for later use.

[0060] 3. Place the treated platinum wire in the middle of the borosilicate capillary glass tube to ensure accurate positioning.

[0061] 4. Seal one end of the borosilicate capillary glass tube with sealing film and place it in the center of the Laser Puller P-2000 laser pulling instrument. Connect the other end to a vacuum pump. Initially adjust the pulling parameters: laser intensity 380, laser beam size 5, speed 15, delay 120, and pulling force 0, to refine the inner diameter of the glass tube to 300 μm. Adjust the parameters again: laser intensity 300, laser beam size 4, speed 15, delay 120, and pulling force 0. Manually stop after 15 seconds. At this point, the middle part of the glass tube is completely sealed to the platinum wire. Finally, cut along the middle of the glass tube to obtain a platinum microelectrode with a diameter of approximately 25 μm and a tip size of approximately 40 μm.

[0062] 5. First, polish the platinum microelectrode on sandpaper, then place it in an alumina slurry for fine polishing until the surface is mirror-like.

[0063] 6. Take a nickel wire, dip its tip in a small amount of silver paste, and insert it into the tail of the borosilicate capillary glass tube under the aid of a microscope, so that the nickel wire and the platinum wire are in close contact; then seal the tail of the glass tube with hot melt glue to fix the nickel wire.

[0064] 7. Polish the electrode again: First, it is initially polished with sandpaper, and then finely polished to a mirror finish in an alumina slurry to obtain a platinum ultra-micro disk electrode with a diameter of 25 μm and an RG value of about 2.

[0065] 8. Weigh out tetrabutylthiuram disulfide (7 mg), polyvinyl chloride (34 mg), o-nitrophenyl octyl ether (58 mg), and sodium tetra(3,5-bis(trifluoromethyl)phenyl)borate (1 mg) in a mass ratio of 7:34:58:1. Mix the above components and dissolve them in tetrahydrofuran. Stir well to prepare a zinc ion selective membrane solution.

[0066] 9. Weigh 1.0 mg of multi-walled carbon nanotubes and add them to 50 μL of the above ion-selective membrane solution. Disperse the multi-walled carbon nanotubes uniformly by ultrasonication (ultrasonic time 5 min) to obtain a mixed solution.

[0067] 10. Add the mixed solution to the probe tip and wait for the solution to solidify into a film to obtain a bifunctional zinc ion selective microelectrode with a diameter of 25 μm.

[0068] Example 4 A method for preparing a bifunctional zinc ion-selective microelectrode includes the following steps: 1. Take 25 μm platinum wire after annealing and straighten it by rolling.

[0069] 2. Take a septum-type borosilicate capillary glass tube with an outer diameter of 1.5 mm and an inner diameter of 1.0 mm, immerse it in a mixed solution of H2SO4 and H2O2 with a volume ratio of 3:1 for 30 min, wash it repeatedly with deionized water, and then dry it for later use.

[0070] 3. Place the treated platinum wire in the middle of the borosilicate capillary glass tube to ensure accurate positioning.

[0071] 4. Seal one end of the borosilicate capillary glass tube with sealing film and place it in the center of the Laser Puller P-2000 laser pulling instrument. Connect the other end to a vacuum pump. Initially adjust the pulling parameters: laser intensity 380, laser beam size 5, speed 15, delay 120, and pulling force 0, to refine the inner diameter of the glass tube to 300 μm. Adjust the parameters again: laser intensity 280, laser beam size 4, speed 15, delay 120, and pulling force 0. Manually stop after 15 seconds. At this point, the middle part of the glass tube is completely sealed to the platinum wire. Finally, cut along the middle of the glass tube to obtain a platinum microelectrode with a diameter of approximately 25 μm and a tip size of approximately 50 μm.

[0072] 5. First, polish the platinum microelectrode on sandpaper, then place it in an alumina slurry for fine polishing until the surface is mirror-like.

[0073] 6. Take a nickel wire, dip its tip in a small amount of silver paste, and insert it into the tail of the borosilicate capillary glass tube under the aid of a microscope, so that the nickel wire and the platinum wire are in close contact; then seal the tail of the glass tube with hot melt glue to fix the nickel wire.

[0074] 7. Polish the electrode again: First, it is initially polished with sandpaper, and then finely polished to a mirror finish in an alumina slurry to obtain a platinum ultra-micro disk electrode with a diameter of 25 μm and an RG value of about 3.

[0075] 8. Weigh out tetrabutylthiuram disulfide (7 mg), polyvinyl chloride (34 mg), o-nitrophenyl octyl ether (58 mg), and sodium tetra(3,5-bis(trifluoromethyl)phenyl)borate (1 mg) in a mass ratio of 7:34:58:1. Mix the above components and dissolve them in tetrahydrofuran. Stir well to prepare a zinc ion selective membrane solution.

[0076] 9. Weigh 1.2 mg of multi-walled carbon nanotubes and add them to 50 μL of the above ion-selective membrane solution. Disperse the multi-walled carbon nanotubes uniformly by ultrasonication (ultrasonic time 5 min) to obtain a mixed solution.

[0077] 10. Add the mixed solution to the probe tip and wait for the solution to solidify into a film to obtain a bifunctional zinc ion selective microelectrode with a diameter of 25 μm.

[0078] To further demonstrate the beneficial effects of the present invention and to better understand it, the technical features disclosed in the present invention are further illustrated by the following comparative examples, experimental examples, and application examples, but these should not be construed as limiting the present invention. Other improvements made by those skilled in the art based on the above-described invention, without inventive effort, are also considered to fall within the protection scope of the present invention.

[0079] Comparative design principle: Based on Example 1, only the core parameters such as "whether multi-walled carbon nanotubes are added" and "the proportion of ion-selective membrane components" are changed, while the other preparation steps and parameters remain consistent. The superiority of the method of the present invention is verified by performance testing and comparison.

[0080] Comparative Example 1: Zinc ion selective microelectrode without the addition of multi-walled carbon nanotubes 1. Steps 1-7 are completely consistent with Example 1.

[0081] 2. Step 8 is the same as in Example 1, preparing a zinc ion selective membrane solution.

[0082] 3. Skip the multi-walled carbon nanotube addition and ultrasonic dispersion operation in step 9, and directly use the pure ion-selective membrane solution prepared in step 8.

[0083] 4. Step 10: Add the pure ion-selective membrane solution to the probe tip, and obtain the target electrode after solidification into a film.

[0084] Comparative Example 2: Zinc ion-selective microelectrode with adjusted composition ratio of ion-selective membrane 1. Steps 1-7 are completely consistent with Example 1.

[0085] 2. Step 8: Adjust the mass ratio of the ion-selective membrane components to tetrabutylthiuram disulfide: polyvinyl chloride: o-nitrophenyl octyl ether: sodium tetra(3,5-bis(trifluoromethyl)phenyl)borate = 5:25:69:1, that is, weigh out tetrabutylthiuram disulfide (5 mg), polyvinyl chloride (25 mg), o-nitrophenyl octyl ether (69 mg), and sodium tetra(3,5-bis(trifluoromethyl)phenyl)borate (1 mg), and the remaining preparation conditions are the same as in Example 1.

[0086] 3. Steps 9-10 are the same as in Example 1, and the target electrode is prepared.

[0087] Experimental Example: Electrode Performance Testing and Verification Test object Zinc ion selective microelectrodes prepared in Experimental Example 1 and Comparative Examples 1 and 2.

[0088] Test conditions Environmental parameters: temperature 25±0.5℃, humidity 50±5%.

[0089] Detection system: Zinc sulfate solution (pH=7.0).

[0090] Test system: Three-electrode system (working electrode is the electrode to be tested, reference electrode is silver / silver chloride electrode, and auxiliary electrode is platinum wire electrode).

[0091] Testing instrument: CHI660E electrochemical workstation.

[0092] Test items and results 1. Observation of probe tip morphology: Observation is performed using a metallurgical microscope, such as... Figure 1 As shown, in the electrode prepared in Example 1, the Pt wire diameter is 25 μm, and the glass and metal wire are tightly bonded together without gaps.

[0093] Note: Since steps 1-7 of Comparative Examples 1 and 2 are completely identical to those of Example 1, the morphology and performance of the Pt electrode are theoretically also completely identical. Here, only the tip morphology of the Pt ultramicro electrode prepared in Example 1 is observed.

[0094] 2. Cyclic voltammetry (CV) curve determination: The electrode under test was placed in a 1 mM ferrocene methanol solution for testing. The results are as follows: Figure 2 As shown in Figure a, the electrode prepared in Example 1 exhibits a good S-shaped CV curve and stable current response, indicating excellent conductivity. Figure 2 b is the CV curve of the electrode prepared in Comparative Example 1. It can be seen that the electrode current value is low and the conductivity is poor. Figure 2 c is the CV curve of the electrode prepared in Comparative Example 2. It can be seen that the electrode CV curve still has a good S-shape, and the conductivity is not significantly affected.

[0095] 3. Linear response performance determination: Prepare a solution with a concentration of 10... -5 10 -4 10 -3 10 -2 10 -1 A zinc ion standard solution of mol / L was used. The electrode to be tested was placed in the solution of each concentration, and the open circuit potential was measured. A standard curve was plotted with the open circuit potential as the ordinate and the logarithm of the zinc ion concentration as the abscissa. The linear correlation coefficient R² of the electrode in Example 1 was as high as 0.997 (mol / L). Figure 3 The linear response is excellent; the electrode linear correlation coefficients of Comparative Examples 1 and 2 are 0.894 ( Figure 4 ), 0.915 ( Figure 5 The response performance of both decreased significantly.

[0096] 4. Verification of probe-substrate position control: The approximation curve of the electrode in ferrocene methanol solution along the z-axis of Example 1 is basically consistent with the standard curve, which can be used for precise control of probe-substrate position in SECM experiments.

[0097] In summary, the zinc ion selective microelectrode prepared in Example 1 is superior to Comparative Examples 1 and 2 in terms of morphological fit, conductivity, linear response performance, and position control accuracy, highlighting the superiority of the technical solution of the present invention.

[0098] Application examples Application scenarios Focusing on the entire charging and discharging process of aqueous zinc-ion batteries, this study achieves high-resolution monitoring of zinc ion concentration in in-situ micro-regions at the negative electrode interface, providing technical support for the study of zinc negative electrode dendrite growth mechanism and optimization of electrolyte-electrode system.

[0099] Detection methods The potential response mode of scanning electrochemical microscopy (SECM) was used. The working electrode was the bifunctional zinc ion selective microelectrode prepared in Example 1, the reference electrode was a silver / silver chloride electrode, the auxiliary electrode was a platinum wire electrode, the detection environment temperature was 25℃, and the electrolyte system was 2 M ZnSO4 solution.

[0100] Operating steps 1. Electrode calibration: with a concentration of 10 -5 10 -4 10 -3 10 -2 10 -1A zinc ion standard solution of mol / L was used as the calibration system. The open circuit potential was measured using the electrode prepared in Example 1, and a standard curve was plotted. The linear regression equation was obtained as E = -0.0134pZn + 0.149 (E is the response potential in V; pZn is the logarithm of the zinc ion concentration), with a correlation coefficient R² = 0.997, ensuring the accuracy of the concentration calculation.

[0101] 2. Sample detection: Using the SECM current response mode, the electrode was brought close to the zinc anode interface at 20 μm, and then switched to the SECM potential response mode. The scanning parameters were set to a scanning area of ​​100×100 μm and a scanning speed of 10 μm / s. The electrode response potential was recorded and substituted into the standard curve to calculate the spatial distribution data of zinc ion concentration in the micro-region of the zinc anode interface.

[0102] 3. Specific testing for charging and discharging scenarios: targeting 1 mA cm -2 Current density, 1 mAh cm -2 During the first discharge of the battery under capacity conditions, in-situ monitoring was performed (monitoring results are as follows). Figure 7 As shown in the figure. A clear presence of Zn²⁺ at the zinc anode interface can be observed from the figure. + The aggregation sites confirm that zinc ions are non-uniformly distributed at the interface during discharge. This distribution feature exacerbates the heterogeneity of zinc ion deposition, thereby promoting the growth of zinc anode dendrites and ultimately shortening the battery cycle life. This fully verifies the accurate monitoring capability of the electrode of this invention under actual working conditions.

[0103] This application example clarifies the correlation between the concentration distribution of zinc ions at the zinc anode interface and dendrite growth during charging and discharging through in-situ monitoring. This not only provides direct experimental evidence for a deeper understanding of the core mechanism of zinc anode dendrite growth, but also has important theoretical guidance for the subsequent design of high-efficiency electrolyte formulations and the development of electrode surface modification strategies, thus helping to promote the performance optimization and industrialization of aqueous zinc-ion batteries.

[0104] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a bifunctional zinc ion selective microelectrode, characterized in that, Specifically, the steps include the following: 1) Take a platinum wire with a diameter of 25 µm and a capillary glass tube with an outer diameter of 0.5 mm to 2.0 mm and an inner diameter of 0.1 mm to 0.5 mm, and place the wire in the hollow cavity of the capillary glass tube. 2) Stretch the capillary glass tube to reduce the diameter at the middle position of the capillary glass tube. When the inner wall at the middle position of the capillary glass tube is in contact with the metal wire, break the capillary glass tube from the middle position to obtain two platinum microelectrodes. 3) Insert a wire into the electrode from the end of the capillary glass tube, connect the wire to the metal wire inside the electrode, and then seal the end of the capillary glass tube. 4) Tetrabutylthiuram disulfide, high molecular weight polyvinyl chloride, o-nitrophenyl octyl ether, and sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate are mixed in a certain proportion and dissolved in tetrahydrofuran to prepare a zinc ion selective membrane solution. 5) Multi-walled carbon nanotubes are uniformly dispersed in a zinc ion selective membrane solution using an ultrasonic method. The dispersed mixture is then drop-coated onto the polished tip of a platinum microelectrode and left to stand in air at room temperature until the mixture at the electrode tip solidifies to form a uniform thin film.

2. The method for preparing the bifunctional zinc ion selective microelectrode according to claim 1, characterized in that, When preparing the zinc ion selective membrane solution, weigh each main ingredient according to the following mass fraction ratios, and the sum of the mass fractions of each main ingredient is 100%: Tetrabutylthiuram disulfide 6%-9%, high molecular weight polyvinyl chloride 30%-35%, o-nitrophenyl octyl ether 50%-60%, sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate 0.3%-1%.

3. The method for preparing the bifunctional zinc ion selective microelectrode according to claim 1, characterized in that, The mass ratio of multi-walled carbon nanotubes to zinc ion selective membrane solution is 1:5 to 1:

20.

4. The application of a bifunctional zinc ion selective microelectrode prepared by the method described in claim 1 in the analysis and detection of zinc ions.

5. The application according to claim 4, characterized in that, Using the bifunctional zinc ion selective microelectrode prepared by the method described in claim 1 as the working electrode, and combining it with a platinum wire counter electrode and an Ag / AgCl reference electrode, a three-electrode in-situ detection system is constructed. By combining the current response mode of scanning electrochemical microscopy, the current signal during the movement of the working electrode along the z-axis is recorded. According to the standard approximation curve, the precise control of the interface position between the bifunctional zinc ion selective microelectrode and the negative electrode of the zinc ion battery can be achieved. The bifunctional zinc ion selective microelectrode enables quantitative analysis of the zinc ion concentration at the interface under precise position control.

6. The application according to claim 5, characterized in that, The bifunctional zinc ion-selective microelectrode can be used for in-situ measurement of Zn in interfacial microregions. 2+ Concentration distribution, the specific operation is as follows: Using the aforementioned three-electrode in-situ detection system, combined with the potential response mode of scanning electrochemical microscopy, the working electrode is controlled to move in three dimensions at a certain height near the negative electrode interface of the zinc-ion battery. At the same time, the response potential signal of the bifunctional zinc-ion selective microelectrode is recorded by an electrochemical workstation. Based on the pre-drawn "zinc ion concentration-response potential" calibration curve, the experimentally recorded response potential signal is converted into the zinc ion concentration of the corresponding micro-region, thereby obtaining the zinc ion concentration distribution data at different spatial locations and time points of the negative electrode interface. This enables in-situ high-resolution detection of the zinc ion concentration distribution in the micro-region of the negative electrode interface of a zinc-ion battery by a dual-function zinc ion selective microelectrode.

7. An ultra-micro electrochemical sensor, characterized in that, The ultramicro electrochemical sensor comprises a bifunctional zinc ion selective microelectrode prepared by the method described in claim 1.

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