An ammonium ion sensor and a method for preparing the same

Abstract

The application discloses an ammonium ion sensor and a preparation method thereof, wherein the ammonium ion sensor comprises a substrate, a reference electrode and a working electrode which are arranged on the substrate in a spaced manner; the working electrode comprises a metal electrode layer, a dendritic gold nanomaterial layer, a conductive polymer layer and an ammonium ion selective membrane which are arranged in a stacked manner; the metal electrode layer is arranged in close contact with the substrate; the conductive polymer layer is arranged in close contact with one side of the dendritic gold nanomaterial layer and wraps around the surface of the dendritic gold according to the shape of the dendritic gold. In the application, the conductive polymer layer is conformal with the dendritic gold in the dendritic gold nanomaterial layer, which is beneficial to electron transmission, reduces potential drift, makes the ammonium ion sensor have good performance, has a low detection lower limit and a wide sensing range, realizes sensitive, stable and real-time noninvasive monitoring of different ammonium ion concentrations in various body fluids, does not produce toxic substances during ammonium ion detection and can realize continuous detection of ammonium ions in body fluids.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, in particular to an ammonium ion sensor and a preparation method thereof. BACKGROUND

[0002] Ammonia (NH3) exists in various body fluids in the form of ammonium ions (NH4 + ), and the concentration of ammonium ions in the body fluid is one of the important indicators reflecting whether the physiological function of human body is normal. Therefore, the technology for detecting ammonium ions has important significance in the field of health monitoring.

[0003] Currently, the detection methods of ammonium ions include colorimetric method and chromatography method. The colorimetric method is based on the indigo phenol reaction of Nessler reagent and soil urease activity detection kit (Berthelot), and the phenolic substances and by-products generated in the reaction process are highly toxic. The ammonium ion detection method using chromatography needs to detect the fluorescence of the sample to obtain the concentration of ammonium ions in combination with a fluorescence detection device. These traditional optical ammonium ion detection methods need large professional instruments and relatively professional operators, and it is difficult to realize continuous detection of ammonium ions in body fluids.

[0004] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0005] In view of the above problems of the prior art, the present application aims to provide an ammonium ion sensor and a preparation method thereof, and aims to solve the problems that the existing ammonium ion detection method produces toxic substances and cannot realize continuous detection of ammonium ions in body fluids.

[0006] The technical scheme of the present application is as follows:

[0007] In a first aspect, the present application provides an ammonium ion sensor, wherein the ammonium ion sensor comprises:

[0008] a substrate, a reference electrode and a working electrode which are arranged on the substrate in a spaced manner;

[0009] The working electrode comprises a metal electrode layer, a dendritic gold nanomaterial layer, a conductive polymer layer and an ammonium ion selective membrane which are arranged in sequence, the metal electrode layer is arranged in close contact with the substrate, the conductive polymer layer is arranged in close contact with one side of the dendritic gold nanomaterial layer, and the dendritic gold nanomaterial layer is wrapped on the surface of the dendritic gold according to the shape of the dendritic gold.

[0010] Optionally, the conductive polymer layer comprises poly 3,4-ethylenedioxythiophene and polystyrene sulfonate.

[0011] Optionally, the reference electrode comprises an Ag / AgCl electrode layer and a reference membrane which are sequentially stacked, and the Ag / AgCl electrode layer is attached to the substrate.

[0012] Optionally, the reference membrane comprises polyvinyl butyrate and sodium chloride.

[0013] In a second aspect, the application provides a method for preparing the ammonium ion sensor as described above, comprising the steps of:

[0014] providing a substrate;

[0015] forming a metal electrode layer, a dendritic gold nanomaterial layer, a conductive polymer layer and an ammonium ion selective membrane on the substrate in sequence to obtain a working electrode, wherein the conductive polymer layer is formed by an electrochemical deposition method;

[0016] forming a reference electrode on the substrate and spaced from the working electrode.

[0017] Optionally, the step of forming a metal electrode layer, a dendritic gold nanomaterial layer, a conductive polymer layer and an ammonium ion selective membrane on the substrate in sequence to obtain a working electrode specifically comprises:

[0018] providing metal ink, printing the metal ink on the substrate by dispensing printing, and drying to form the metal electrode layer;

[0019] depositing gold on the metal electrode layer by pulse potential method to form the dendritic gold nanomaterial layer;

[0020] depositing conductive polymer on the dendritic gold nanomaterial layer by pulse potential method to form the conductive polymer layer;

[0021] providing an ammonium ion selective membrane solution, transferring the ammonium ion selective membrane solution to the conductive polymer layer, and drying to form the ammonium ion selective membrane to obtain the working electrode.

[0022] Optionally, in the step of depositing gold on the metal electrode layer by pulse potential method to form the dendritic gold nanomaterial layer, a mixed solution of tetrachloroauric acid and hydrochloric acid is used as the deposition solution.

[0023] Optionally, in the step of depositing conductive polymer on the dendritic gold nanomaterial layer by pulse potential method to form the conductive polymer layer, a conductive polymer solution is used as the deposition solution, and the preparation method of the conductive polymer solution comprises the steps of:

[0024] adding polystyrene sulfonate, potassium ferrocyanide and 3,4-ethylenedioxythiophene into water to form the conductive polymer solution.

[0025] Optionally, the step of forming a reference electrode spaced apart from the working electrode on the substrate specifically comprises:

[0026] The silver ink is provided, and the silver ink is printed on the substrate by using the dispensing printing method. After drying, a silver electrode layer spaced apart from the working electrode is obtained.

[0027] An iron chloride solution is added dropwise on the silver electrode layer, and after reaction, an Ag / AgCl electrode layer is formed.

[0028] A reference film solution is provided, and the reference film solution is transferred to the Ag / AgCl electrode layer. After drying, a reference film is formed.

[0029] Optionally, the preparation method of the reference film solution comprises the steps of:

[0030] Polyvinyl butyrate and sodium chloride are dissolved in an organic solvent to form the reference film solution.

[0031] Beneficial effects: In the present application, the conductive polymer layer is attached to one side of the dendritic gold nanomaterial layer, and is wrapped around the surface of the dendritic gold according to the shape of the dendritic gold, that is, the conductive polymer layer can be conformal with the dendritic gold in the dendritic gold nanomaterial layer, which is beneficial to electron transmission, reduces potential drift, realizes high conformality of the ammonium ion sensor nanostructure, and makes the ammonium ion sensor have good performance, has a low detection lower limit and a wide sensing range, realizes sensitive, stable and real-time non-invasive monitoring of different ammonium ion concentrations in various body fluids. The ammonium ion sensor provided by the present application has the advantages of miniaturization and fast response speed based on the potential method for detecting ammonium ions, and can realize continuous detection of ammonium ions in body fluids without producing toxic substances during ammonium ion detection. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a structure schematic diagram of the ammonium ion sensor in the embodiment of the present application.

[0033] Figure 2 (a) is a surface SEM image of the silver electrode layer in Example 1 of the present application, (b) is a surface SEM image of the dendritic gold nanomaterial layer on the surface of the silver electrode layer in Example 1 of the present application, and (c) is a surface SEM image of the conductive polymer layer on the surface of the dendritic gold nanomaterial layer in Example 1 of the present application.

[0034] Figure 3 It is a physical diagram of the silver electrode layer in Example 1 of the present application.

[0035] Figure 4 It is a physical diagram of the silver electrode layer with a dendritic gold nanomaterial layer on the surface in Example 1 of the present application.

[0036] Figure 5A real object diagram of a silver electrode layer with a layer of dendritic gold nanomaterial and a layer of conductive polymer on the surface in Example 1 of the present application.

[0037] Figure 6 A voltage-time curve of the ammonium ion sensor in Example 1 of the present application for detecting ammonium ions of different concentrations.

[0038] Figure 7 A result diagram of sensitivity test of the ammonium ion sensor in Example 1 of the present application. DETAILED DESCRIPTION

[0039] The present application provides an ammonium ion sensor and a preparation method thereof. To make the purpose, technical solutions and effects of the present application more clear and explicit, the present application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein only for the purpose of describing specific embodiments and is not intended to limit the present application.

[0041] The present application provides an ammonium ion sensor, wherein, as shown in the accompanying drawings (the cross-sectional view of the working electrode is in the rightmost rectangular dashed box, and the cross-sectional view of the reference electrode is in the leftmost oval dashed box), the ammonium ion sensor comprises: Figure 1

[0042] a substrate, a reference electrode and a working electrode which are arranged on the substrate in a spaced manner;

[0043] The working electrode comprises a metal electrode layer, a layer of dendritic gold nanomaterial, a layer of conductive polymer and an ammonium ion selective membrane which are arranged in sequence, the metal electrode layer is arranged in close contact with the substrate, the layer of conductive polymer is arranged in close contact with one side of the layer of dendritic gold nanomaterial and wraps around the surface of the dendritic gold according to the shape of the dendritic gold.

[0044] ​In the present application, the conductive polymer layer contacts one side of the branched gold nanomaterial layer, and the branched gold is wrapped on the surface of the branched gold nanomaterial, that is, the conductive polymer layer can conform to the branched gold in the branched gold nanomaterial layer, thereby facilitating electron transmission, reducing potential drift, realizing high conformality of the ammonium ion sensor nanostructure, and enabling the ammonium ion sensor to have good performance, a low detection lower limit, and a wide sensing range, thereby realizing sensitive, stable, and real-time non-invasive monitoring of different ammonium ion concentrations in various body fluids. The ammonium ion sensor provided in the present application has the advantages of miniaturization and fast response speed in detecting ammonium ions based on the potential method. The low detection lower limit and wide sensing range of the ammonium ion sensor are realized through the conformation of the conductive polymer and the branched gold nanostructure. The high sensitivity and real-time measurement of ammonium ions in the body fluid are realized through the selectivity of the ammonium ion selective membrane. When detecting ammonium ions, no toxic substances are generated, and continuous detection of ammonium ions in the body fluid can be realized.

[0045] In the present embodiment, the conductive polymer layer is attached to one side of the branched gold nanomaterial layer, and the branched gold is wrapped on the surface of the branched gold, that is, the conductive polymer layer attached to one side of the branched gold nanomaterial layer has the shape of the branched gold. It can be understood that when the conductive polymer layer is thin, the side of the conductive polymer layer attached to the ammonium ion selective membrane also has a similar shape of the branched gold; and when the conductive polymer layer is thick enough, the side of the conductive polymer layer attached to the ammonium ion selective membrane can be a planar structure.

[0046] In the present embodiment, covering the branched gold nanomaterial layer with the metal electrode layer can make the ammonium ion sensor more stable and have a longer service life. Meanwhile, the three-dimensional structure of the branched gold in the branched gold nanomaterial layer increases the contact area, and a small amount of body fluid to be measured is required, thereby having a low detection limit, that is, a small sensor can be used to complete the detection.

[0047] In addition, the ammonium ion sensor provided in the present embodiment has good biocompatibility and can be used in multiple fields such as biomedicine.

[0048] In one embodiment, the substrate is a flexible substrate, and the material of the flexible substrate includes but is not limited to one of polyethylene terephthalate (PET) and polyimide (PI). The substrate of the composition is stretchable and foldable, and a flexible ammonium ion sensor can be prepared by using the stretchable and foldable flexible substrate. The flexible ammonium ion sensor is more attached to the skin and forms a wearable ammonium ion sensor.

[0049] In one embodiment, the material of the metal electrode layer is one of silver and gold, but is not limited thereto.

[0050] In one embodiment, the thickness of the branched gold nanomaterial layer is 1-5 μm, that is, the height of the branched gold can be 1-5 μm.

[0051] In an embodiment, the conductive polymer layer comprises poly(3,4-ethylenedioxythiophene) and polystyrene sulfonate.

[0052] In an embodiment, the conductive polymer layer consists of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonate, i.e. the conductive polymer layer consists of PEDOT:PSS. The conductive polymer PEDOT:PSS, consisting of a polymer of 3,4-ethylenedioxythiophene monomer, i.e. poly(3,4-ethylenedioxythiophene) and polystyrene sulfonate, has unique electrical and ionic dual conductivity and excellent biocompatibility. PEDOT:PSS is used in this embodiment, which is more flexible and non-toxic compared to inorganic materials, thereby reducing the mechanical mismatch with biological tissues and avoiding the loss of biological tissues. In addition, PEDOT:PSS has lower impedance and higher charge injection capacity than metal, and can be chemically adjusted to adjust its electrical properties or allow covalent attachment of biomolecules. In addition, PEDOT:PSS is more conducive to conformal with dendritic gold in the layer of dendritic gold nano-material, more conducive to the transmission of electrons, reduces the drift of potential, and more conducive to achieving high conformality of nanostructures, so that the sensor has a low lower limit of measurement and a wide sensing range, and the use of this PEDOT:PSS can make the performance of the ammonium ion sensor more excellent.

[0053] In an embodiment, the ammonium ion selective membrane comprises a polyvinyl chloride (PVC) matrix and a mobile ion carrier doped in the polyvinyl chloride matrix. Further, the mobile ion carrier is nonactin or the like. In this embodiment, based on the high selectivity and high electrochemical signal conduction sensitivity of the ammonium ion selective membrane, selective recognition of ammonium ions in sweat is achieved, specifically, the ammonium ions can be selectively combined according to size and shape, thereby generating a potential gradient on the membrane. By introducing a selective ion barrier at the solution device interface, the ion signals derived from interfering ion substances are blocked. This embodiment realizes high sensitivity measurement of ammonium ions in body fluids through the selectivity of the ammonium ion selective membrane.

[0054] In an embodiment, the reference electrode comprises an Ag / AgCl electrode layer and a reference membrane which are sequentially stacked, and the Ag / AgCl electrode layer is attached to the substrate.

[0055] In an embodiment, the reference membrane comprises polyvinyl butyrate and sodium chloride.

[0056] In an embodiment, the reference membrane consists of polyvinyl butyrate and sodium chloride.

[0057] The present application also provides a preparation method of the ammonium ion sensor as described above.

[0058] S1, providing a substrate;

[0059] S2, sequentially forming a metal electrode layer, a dendritic gold nanomaterial layer, a conductive polymer layer, and an ammonium ion selective membrane on the substrate to obtain a working electrode; wherein the conductive polymer layer is formed by an electrochemical deposition method;

[0060] S3, forming a reference electrode on the substrate and spaced apart from the working electrode.

[0061] The ammonium ion sensor prepared in the embodiment has good performance, a low detection lower limit, and a wide sensing range, and can realize sensitive, stable, and real-time non-invasive monitoring of the concentration of different ammonium ions in various body fluids. Moreover, the ammonium ion sensor does not produce toxic substances during ammonium ion detection and can realize continuous detection of ammonium ions in body fluids. In the embodiment, the conductive polymer layer is formed by an electrochemical deposition method, which can enable the conductive polymer to wrap around the surface of the dendritic gold during deposition, that is, the conductive polymer can conform to the dendritic gold in the dendritic gold nanomaterial layer, thereby facilitating electron transmission, reducing potential drift, realizing high shape retention of the ammonium ion sensor nanostructure, and enabling the ammonium ion sensor to have good performance, a low detection lower limit, and a wide sensing range, and to realize sensitive, stable, and real-time non-invasive monitoring of the concentration of different ammonium ions in various body fluids.

[0062] In step S1, in an embodiment, the substrate is a flexible substrate, and the material of the flexible substrate includes but is not limited to one of polyethylene terephthalate (PET) and polyimide (PI). In the embodiment, the substrate is stretchable and foldable, and the flexible ammonium ion sensor prepared by using the stretchable and foldable flexible substrate is more conformable to the skin.

[0063] In step S2, in an embodiment, the step of sequentially forming a metal electrode layer, a dendritic gold nanomaterial layer, a conductive polymer layer, and an ammonium ion selective membrane on the substrate to obtain a working electrode specifically includes:

[0064] S21, providing metal ink, and printing the metal ink on the substrate by using a dispensing printing method, and forming the metal electrode layer after drying;

[0065] S22, depositing gold on the metal electrode layer by using a pulse potential method to form the dendritic gold nanomaterial layer;

[0066] S23, depositing a conductive polymer on the dendritic gold nanomaterial layer by using a pulse potential method to form the conductive polymer layer;

[0067] S24, providing an ammonium ion selective membrane solution, transferring the ammonium ion selective membrane solution to the conductive polymer layer, and after drying, forming the ammonium ion selective membrane to obtain the working electrode.

[0068] In this embodiment, the metal ink is printed on the substrate, and then the dendritic gold nanomaterial and the conductive polymer are electrochemically deposited, and finally the ammonium ion selective membrane is formed on the conductive polymer layer to realize the selective recognition of ammonium ions in sweat.

[0069] Unlike the traditional method of preparing electrodes by ion sputtering film plating through a mask plate, in this embodiment, the dispensing printing method is used for the first time to manufacture the electrodes of the wearable ammonium ion sensor. Specifically, the dispensing equipment can be used to draw the shape of the metal electrode, and the microelectronic printer can print the metal electrode on the substrate according to the received image. This method is simple to operate, has higher freedom, can save time, and can realize the rapid and batch preparation of the ammonium ion sensor electrode with low cost.

[0070] Steps S22 and S23 use the pulse potential method to deposit gold on the metal electrode layer to form a dendritic gold nanomaterial layer, and then deposit a conductive polymer on the dendritic gold nanomaterial layer. The conductive polymer is conformal with the dendritic gold nanomaterial, which is conducive to electron transmission, reduces potential drift, realizes the high conformality of the ammonium ion sensor nanostructure, and makes the ammonium ion sensor have good performance, low detection limit and wide sensing range, and realizes the sensitive, stable and real-time non-invasive monitoring of the concentration of different ammonium ions in various body fluids.

[0071] In step S21, in one embodiment, the metal ink is printed on the substrate by using the dispensing printer and the dispensing printing method. Specifically, the metal ink is placed in the dispensing printer, and then the metal ink is printed on the substrate under a preset pressure (for example, 29 kPa) and a preset printing speed (for example, 3 mm / s).

[0072] In one embodiment, the metal ink is silver ink, but is not limited thereto. The silver ink can be obtained by direct purchase.

[0073] In step S22, the gold is deposited on the metal electrode layer in the three-electrode system of the electrochemical workstation by pulse potential method to form the layer of the dendritic gold nanomaterial. Specifically, the counter electrode in the three-electrode system of the electrochemical workstation is connected with the platinum wire electrode, the reference electrode in the three-electrode system of the electrochemical workstation is connected with the Ag / AgCl electrode, and the working electrode in the three-electrode system of the electrochemical workstation is connected with the metal electrode layer on the substrate, and the distance between the electrodes (e.g. 2-3 mm) is controlled to avoid collision. A mixed solution of tetrachloroauric acid and hydrochloric acid is used as the deposition solution (for example, the concentration of tetrachloroauric acid in the deposition solution can be 50 mM, and the concentration of HCl can be 50 mM), and then the deposition is performed at a preset voltage (e.g. -2 V) and a preset frequency (e.g. 50 Hz) for a preset number of times (e.g. 3000 times) to form the layer of the dendritic gold nanomaterial. The use of high-concentration deposition solution and high voltage enables the layer of the dendritic gold nanomaterial with excellent performance to be prepared in a short time.

[0074] In step S23, the conductive polymer is deposited on the layer of the dendritic gold nanomaterial in the three-electrode system of the electrochemical workstation by pulse potential method to form the layer of the conductive polymer. Specifically, the counter electrode in the three-electrode system of the electrochemical workstation is connected with the platinum wire electrode, the reference electrode in the three-electrode system of the electrochemical workstation is connected with the Ag / AgCl electrode, and the working electrode in the three-electrode system of the electrochemical workstation is connected with the metal electrode layer on the substrate, and the distance between the electrodes (e.g. 2-3 mm) is controlled to avoid collision. A conductive polymer solution is used as the deposition solution, and then the deposition is performed at a preset voltage (e.g. 0.865 V) and a preset frequency (e.g. 1 Hz) for a preset number of times (e.g. 840 times).

[0075] In an embodiment, the preparation method of the conductive polymer solution comprises the steps of:

[0076] Polystyrene sulfonate, potassium ferrocyanide and 3,4-ethylenedioxythiophene are added to water to form the conductive polymer solution.

[0077] In step S24, in a specific embodiment, the ammonium ion-selective membrane is dropped on the layer of the conductive polymer (the dropping amount can be 2-3 μL), and after drying (e.g. at room temperature), the ammonium ion-selective membrane is formed to obtain the working electrode.

[0078] In step S3, in an embodiment, the step of forming the reference electrode spaced apart from the working electrode on the substrate specifically comprises:

[0079] S31, providing silver ink, printing the silver ink on the substrate by using the dispensing printing method, and obtaining a silver electrode layer spaced from the working electrode after drying;

[0080] S32, dropping a ferric chloride solution on the silver electrode layer, and forming an Ag / AgCl electrode layer after reaction;

[0081] S33, providing a reference film solution, transferring the reference film solution to the Ag / AgCl electrode layer, and forming a reference film after drying.

[0082] In step S31, unlike the traditional method of preparing electrodes by ion sputtering film plating through a mask plate, the silver ink is printed into a silver electrode layer with a certain shape by using the dispensing printing method for the electrode of the wearable ammonium ion sensor, so that the electrode of the ammonium ion sensor can be mass-produced and the cost is low. Of course, the silver electrode layer for preparing the reference electrode can also be printed at the same time as the metal electrode layer (step S21) of the working electrode is printed.

[0083] In step S32, the step of forming an Ag / AgCl electrode layer by dropping a ferric chloride solution on the silver electrode layer after reaction specifically includes:

[0084] The FeCl3 solution is dropped on the silver electrode layer to completely cover the silver electrode layer (for example, the dropping amount can be 2-3 μL), and after 10-15 s of reaction, the excess FeCl3 solution is removed.

[0085] In step S33, in one embodiment, the reference film solution is transferred to the Ag / AgCl electrode layer.

[0086] In one embodiment, the preparation method of the reference film solution includes the steps of:

[0087] Polyvinyl butyrate and sodium chloride are dissolved in an organic solvent to form the reference film solution.

[0088] In one embodiment, the organic solvent is methanol. Specifically, polyvinyl butyrate and sodium chloride are dissolved in methanol to form a reference film solution, which is then dropped onto the Ag / AgCl electrode layer (as an example, the dropping amount can be 2-3 μL), and after drying, a reference film is formed.

[0089] The application will be further described through specific examples.

[0090] Example 1

[0091] The silver ink is a commercially available product, and the silver ink used in this example is SINWE (Xinwei) 3703 conductive silver paste.

[0092] (1) Pointing and printing two silver electrode layers (for distinction, respectively referred to as a first silver electrode layer and a second silver electrode layer) arranged at intervals on a PET film. Specifically, the steps include:

[0093] The silver ink is put into a pointing and printing head with an aperture of 0.16 mm, and the first silver electrode layer and the second silver electrode layer arranged at intervals are printed on a PET film with a thickness of 25 μm at a printing speed of 3 mm / s using a pressure of 29 KPa, and then placed on a heating table and heated and dried at 80℃ for 10 min. Among them, both silver electrode layers are circles with a diameter of 2 mm, and the center distance between the two is 3 mm. Both silver electrode layers are connected with wires, and the electrode wire length is 10 mm and the width is 0.5 mm. The SEM image of the silver electrode layer is shown in Figure 2 (a), and the actual image is shown in Figure 3 .

[0094] (2) Using pulse potential method, a branched gold nanomaterial layer is deposited on the first silver electrode layer. Specifically, the steps include:

[0095] 0.17 g of HAuCl4, 83.3 μL of hydrochloric acid solution (HCL concentration is 6M), 10 mL of deionized water are mixed and shaken to obtain a mixed solution with a concentration of 50 mM of HAuCl4 and HCl, and stored at 4℃ for standby;

[0096] In the three-electrode system of the electrochemical workstation, the counter electrode in the electrochemical workstation is connected with the platinum wire electrode, the reference electrode in the electrochemical workstation is connected with the Ag / AgCl electrode, and the working electrode in the electrochemical workstation is connected with the above-mentioned first silver electrode layer. The distance between each electrode (counter electrode, reference electrode, working electrode) is controlled to be 3 mm; the voltage direction and size is set to -2V, the frequency is 50 Hz, and the deposition cycle number is 3000 times; 100 μL of the mixed solution with a concentration of 50 mM of HAuCl4 and HCl is added dropwise to the surface of the silver electrode layer in the deposition area, and the deposition is started. The deposition time is 1 min, and the oxidation-reduction reaction occurs. The surface of the deposition area turns yellow, and a branched gold nanomaterial layer with a thickness of 5 μm is covered on the first silver electrode layer. The SEM image is shown in Figure 2 (b), and the actual image is shown in Figure 4 .

[0097] (3) Using pulse potential method, a conductive polymer PEDOT:PSS is deposited on the branched gold nanomaterial layer to form the conductive polymer layer. Specifically, the steps include:

[0098] The PET film with the first and second silver electrode layers and the branched gold nanomaterial layer on the surface is washed with ultrapure water for 2 times, and dried for 10 min;

[0099] Mix 206 mg NaPss, 36.8 mg K4FeCN6, 10.6 μL EDOT, 10 mL deionized water, shake well to obtain a conductive polymer deposition solution, and store at 4°C for standby;

[0100] In the three-electrode system of the electrochemical workstation, the counter electrode in the three-electrode system of the electrochemical workstation is connected with the platinum wire electrode, the reference electrode in the three-electrode system of the electrochemical workstation is connected with the Ag / AgCl electrode, the working electrode in the three-electrode system of the electrochemical workstation is connected with the first silver electrode layer after deposition of gold, and the distance between each electrode (counter electrode, reference electrode, working electrode) is controlled to be 3 mm; the voltage direction and size is set to 0.865 V, the frequency is 1 Hz, and the deposition cycle number is 84 times; 100 μL of the conductive polymer deposition solution is added dropwise on the surface of the dendritic gold nanomaterial layer, and deposition is started to obtain a conductive polymer layer conformal to the dendritic gold nanomaterial layer, the SEM image of which is shown in FIG. 8(c), and the physical image thereof is shown in FIG. 8(d). Figure 3 Figure 5

[0101] (4) Dropping ammonium ion selective membrane solution on the conductive polymer layer, and drying to form the ammonium ion selective membrane. Specifically comprising the steps of:

[0102] Washing the product obtained in the above step (3) with ultrapure water for 3 times, and drying at room temperature for 10 min;

[0103] Mixing 1 wt% nonactin, 0.5 wt% tetrasodium salt [3,5-bis(trifluoromethylphenyl)]borate (NaTFPB), 32.6 wt% PVC, and 65.9 wt% bis(2-ethylhexyl)sebacate (DOS) to form a mixture, taking 100 mg of the mixture to dissolve in 660 uL of tetrahydrofuran, shaking and shaking well to obtain an ammonium ion selective membrane solution, and storing at 4°C for standby;

[0104] Dropping the above ammonium ion selective membrane solution on the conductive polymer layer, the dropping amount is 3 μL, the dropping number is 1 time, and drying at room temperature for 6 h to form the ammonium ion selective membrane.

[0105] (5) Dropping ferric chloride solution on the second silver electrode layer, and forming the Ag / AgCl electrode layer after reaction. Specifically comprising the steps of:

[0106] Dissolving FeCl3 in deionized water to form a 1M FeCl3 solution;

[0107] Dropping the above FeCl3 solution on the second silver electrode layer, the dropping amount is 3 μL, completely covering the silver electrode layer, the covering time is 15 s, then removing the remaining FeCl3 solution, and drying at room temperature for 10 min to form the Ag / AgCl electrode layer.​​

[0108] (6) Forming a reference film on the Ag / AgCl electrode layer. The specific steps include:

[0109] Dissolve 79.1 mg of polyvinyl butyrate and 50 mg of sodium chloride in 1 mL of methanol to form a reference film solution;

[0110] Drop the above-mentioned reference film solution onto the Ag / AgCl electrode layer, the drop amount is 3 μL, the drop number is 1, and then dry at room temperature for 6 h to form a reference film.

[0111] Test:

[0112] Use a three-electrode system of a multi-channel potentiostat, the counter electrode in the three-electrode system of the potentiostat is connected with a platinum wire electrode, the reference electrode in the three-electrode system of the potentiostat is connected with the Ag / AgCl electrode layer in the ammonium ion sensor, the working electrode in the three-electrode system of the potentiostat is connected with the first silver electrode layer in the ammonium ion sensor, and the distance between each electrode is controlled to be 2 mm;

[0113] Drop 50 μL of 100 mM NH4Cl solution in the sensing area, stand for 30 s, and start the test. Measure the voltage-time (Vt) curve, and pause. Remove the added solution, clean the sensor with ultrapure water, and dry the electrodes. Drop 50 μL of 10 mM NH4Cl solution in the sensing area, stand for 30 s, and start the test. Repeat the above steps to measure the voltage-time (Vt) curves of 1 mM, 100 μM, and 10 μM NH4Cl solutions, respectively. Measure the voltage-time (Vt) curves of NH4Cl solutions with different concentrations in five orders of magnitude from 10 μM to 100 mM. The results are shown in Figure 6 , the sensitivity results are shown in Figure 7 , and the sensitivity is 54.7 mV / decade.

[0114] In summary, the application provides an ammonium ion sensor and a preparation method and application thereof. In the application, the conductive polymer layer is attached to one side of the dendritic gold nanomaterial layer, and the conductive polymer layer is wrapped around the dendritic gold on the surface of the dendritic gold, that is, the conductive polymer layer can be conformal with the dendritic gold in the dendritic gold nanomaterial layer, which is conducive to electron transmission, reduces potential drift, realizes high shape retention of the ammonium ion sensor nanostructure, and makes the ammonium ion sensor have good performance, has a low detection lower limit and a wide sensing range, realizes sensitive, stable and real-time non-invasive monitoring of different ammonium ion concentrations in various body fluids. The ammonium ion sensor provided in the application has the advantages of miniaturization and fast response speed in detecting ammonium ions based on the potential method, realizes a low detection lower limit and a wide sensing range of the ammonium ion sensor through the conformal of the conductive polymer and the dendritic gold nanostructure, realizes high sensitivity and real-time measurement of ammonium ions in the body fluid through the selectivity of the ammonium ion selective membrane, and realizes continuous detection of ammonium ions in the body fluid without generating toxic substances during ammonium ion detection. In addition, unlike the traditional method of preparing an electrode by ion sputtering film coating using a mask plate, in the embodiment, the dispensing printing method is used to manufacture the electrode of the ammonium ion sensor for the first time, which has the advantages of simple operation, higher freedom, time saving, and can realize rapid and batch preparation of the electrode of the ammonium ion sensor, and has low cost.

[0115] It should be understood that the application of the application is not limited to the above examples, and can be improved or changed according to the above description for those skilled in the art, and all these improvements and changes should belong to the protection scope of the appended claims of the application.

Claims

1. An ammonium ion sensor characterized by, The ammonium ion sensor comprises: a substrate, a reference electrode and a working electrode which are arranged on the substrate in a spaced manner; the working electrode comprises a metal electrode layer, a dendritic gold nanomaterial layer, a conductive polymer layer and an ammonium ion selective membrane which are arranged in a stacked manner, the metal electrode layer is arranged on the substrate, the conductive polymer layer is arranged on one side of the dendritic gold nanomaterial layer and wraps around the surface of the dendritic gold according to the shape of the dendritic gold; the thickness of the dendritic gold nanomaterial layer is 1-5 μm; the ammonium ion selective membrane comprises the following components in mass percentage: 1 wt% of non-viable antibiotic, 0.5 wt% of tetrasodium [3,5-bis(trifluoromethylphenyl)]borate, 32.6 wt% of polyvinyl chloride and 65.9 wt% of bis(2-ethylhexyl)sebacate; the reference electrode comprises an Ag / AgCl electrode layer and a reference membrane which are arranged in a stacked manner, and the Ag / AgCl electrode layer is arranged on the substrate; the reference membrane comprises polyvinyl butyrate and sodium chloride.

2. The ammonium ion sensor of claim 1, wherein the conductive polymer layer comprises poly(3,4-ethylenedioxythiophene) and polystyrene sulfonate.

3. A method for the preparation of an ammonium ion sensor according to any one of claims 1-2, characterized in that, The method comprises the steps of: providing a substrate; forming a metal electrode layer, a dendritic gold nanomaterial layer, a conductive polymer layer and an ammonium ion selective membrane on the substrate in a stacked manner to obtain a working electrode, wherein the conductive polymer layer is formed by an electrochemical deposition method; forming a reference electrode on the substrate in a spaced manner with the working electrode; in the step of depositing gold on the metal electrode layer to form the dendritic gold nanomaterial layer by using the pulse potential method, a mixed solution of tetrachloroauric acid and hydrochloric acid is used as the deposition solution, wherein the concentration of tetrachloroauric acid is 50 mM and the concentration of HCl is 50 mM.

4. The method for preparing an ammonium ion sensor according to claim 3, characterized by, The step of forming a metal electrode layer, a dendritic gold nanomaterial layer, a conductive polymer layer and an ammonium ion selective membrane on the substrate in a stacked manner to obtain a working electrode specifically comprises the steps of: providing metal ink, printing the metal ink on the substrate by using the dispensing printing method, and drying to form the metal electrode layer; depositing gold on the metal electrode layer to form the dendritic gold nanomaterial layer by using the pulse potential method; depositing conductive polymer on the dendritic gold nanomaterial layer to form the conductive polymer layer by using the pulse potential method; providing an ammonium ion selective membrane solution, transferring the ammonium ion selective membrane solution to the conductive polymer layer, and drying to form the ammonium ion selective membrane to obtain the working electrode.

5. The method for preparing an ammonium ion sensor according to claim 4, characterized by, in the step of depositing conductive polymer on the dendritic gold nanomaterial layer to form the conductive polymer layer by using the pulse potential method, a conductive polymer solution is used as the deposition solution, and the preparation method of the conductive polymer solution comprises the steps of: adding polystyrene sulfonate, potassium ferrocyanide and 3,4-ethylenedioxythiophene into water to form the conductive polymer solution.

6. The method for preparing an ammonium ion sensor according to claim 3, wherein The step of forming a reference electrode on the substrate in a spaced manner with the working electrode specifically comprises the steps of: providing silver ink, printing the silver ink on the substrate by using the dispensing printing method, and drying to obtain a silver electrode layer which is arranged in a spaced manner with the working electrode; Dropping ferric chloride solution on the silver electrode layer, and forming Ag / AgCl electrode layer after reaction; Providing reference film solution, transferring the reference film solution to the Ag / AgCl electrode layer, and forming reference film after drying.

7. The method for preparing an ammonium ion sensor according to claim 6, wherein The preparation method of the reference film solution comprises the steps of: Dissolving polyvinyl butyrate and sodium chloride in an organic solvent to form the reference film solution.

Images