Ion selective electrode, preparation method thereof and detection probe

Abstract

The invention relates to an ion selective electrode, a preparation method thereof and a detection probe. The ion selective electrode comprises a conductive substrate, a conductive layer, a solid contact layer and an ammonium ion sensitive film which are sequentially stacked, the conductive substrate is a metal sheet, and the solid contact layer comprises graphene quantum dots and a conductive polymer. The preparation method of the ion selective electrode comprises the following steps: (1) electrically depositing a conductive layer on a conductive substrate, wherein the conductive substrate is a metal sheet; (2) electrodepositing a solid-state contact layer on the conductive layer by using a dispersion liquid for forming the solid-state contact layer, the dispersion liquid for forming the solid-state contact layer including graphene quantum dots and a monomer for forming a conductive polymer; and (3) forming an ammonium ion sensitive membrane on the solid contact layer. The detection probe comprises a connecting seat and the ion selective electrode, wherein the ion selective electrode is in threaded connection with the connecting seat.

Description

TECHNICAL FIELD

[0001] The present application relates to an ion-selective electrode and a preparation method thereof, and a detection probe, and belongs to the technical field of ion-selective electrodes. BACKGROUND

[0002] Ion-selective electrodes are commonly used instruments in ion analysis and have been widely used in the fields of environmental monitoring, biomedical analysis, industrial analysis, and marine pollution monitoring. In particular, ammonium ions are one of the important biochemical indicators in aquaculture water quality, and the content thereof has an important influence on water quality and water product quality.

[0003] The structure of the ion-selective electrode in most current commercial electrode ammonia nitrogen probes mainly includes an ammonium ion sensitive membrane (sometimes referred to as an ammonium sensitive membrane herein), a filling solution for conduction, and a conductive part. However, this type of ammonia nitrogen probe has the following four problems: 1. The filling solution leaks, the ammonium sensitive membrane loses the conduction medium with the conductive part, and the test is abnormal; 2. The bubbles in the filling solution adhere to the membrane or the conductive wire, resulting in inaccurate testing; the probe can only be placed vertically during testing to avoid bubble interference, and the probe needs to be shaken before testing to drive the bubbles to the top; 3. The ammonium sensitive membrane has no effective support and is more prone to damage under water flow impact; 4. When the ammonium sensitive membrane is damaged, the replacement of the membrane head is easy to cause the spilling and pollution of the filling solution. Therefore, it is desirable to develop a full solid-state ion-selective electrode.

[0004] The structure of the current full solid-state ion-selective electrode generally mainly includes a conductive substrate, a solid-state contact layer (SC), and an ion-selective membrane (SM). The SC converts the ion concentration into an electronic signal. The SM layer plays an ion recognition role through an ion carrier.

[0005] For example, patent document 1 provides a solid-state ammonium ion electrode based on conductive polyaniline, in which a metal wire is used as a conductive substrate and conductive polyaniline is used as a solid-state contact layer. However, the supportability of this conductive substrate is poor, and the electrode is prone to damage (especially during replacement). Moreover, although the size of the electrode is small, the contact area with the measured object is small, which has a negative impact on the sensitivity of the electrode. In addition, the ion-electron transduction ability of the solid-state contact layer needs to be improved, which also leads to the need to improve the sensitivity of the electrode.

[0006] In addition, regarding the solid-state contact layer, some studies have mentioned the research progress of various materials as solid-state contact layer materials.

[0007] For example, patent document 2 provides an ammonium ion electrode with proton-doped polyaniline as a sensitive membrane, which includes a metal wire, a carbon film, and proton-doped polyaniline.

[0008] For example, Patent Document 3 provides a solid-state ion-selective electrode in which a solid-state contact layer is a porous, ordered nanostructured NiCo2S4 layer formed in situ on the surface of an electrode substrate.

[0009] <<Prior Art Documents>>

[0010] Patent Document 1: CN103063725A

[0011] Patent Document 2: CN106093161A

[0012] Patent Document 3: CN113189177A SUMMARY

[0013] <<Problems to be Solved by the Invention>>

[0014] In view of the above, the purpose of the present application is to provide an ion-selective electrode that is easy to replace, has an ammonium ion-sensitive membrane that is not easily deformed or damaged, and has high sensitivity. The purpose of the present application is also to provide a production method that can easily obtain an ion-selective electrode that is easy to replace, has an ammonium ion-sensitive membrane that is not easily deformed or damaged, and has high sensitivity. In addition, the purpose of the present application is also to provide a detection probe in which the ion-selective electrode is easy to replace, the ammonium ion-sensitive membrane is not easily deformed or damaged.

[0015] <<Solution to the Problem>>

[0016] According to the diligent research of the inventor of the present application, it is found that the above technical problems can be solved by implementing the following technical solutions.

[0017] [1]. An ion-selective electrode, comprising: an electrically conductive substrate, an electrically conductive layer, a solid-state contact layer, and an ammonium ion-sensitive membrane, which are sequentially stacked,

[0018] The electrically conductive substrate is a metal sheet,

[0019] The solid-state contact layer comprises graphene quantum dots and an electrically conductive polymer.

[0020] [2]. The ion-selective electrode according to [1], wherein the metal sheet is at least one selected from a platinum sheet, a titanium sheet, or a titanium sheet plated with platinum; and / or

[0021] The electrically conductive polymer is polyaniline.

[0022] [3]. The ion-selective electrode according to [1] or [2], wherein the electrically conductive layer is composed of metal nanoparticles; and / or

[0023] The ammonium ion-sensitive membrane comprises an ion exchanger, a plasticizer, a non-conductive polymer, and an ammonium ion carrier.

[0024] [4]. The ion-selective electrode according to [3], wherein the metal nanoparticle is at least one selected from the group consisting of copper nanoparticle and silver nanoparticle.

[0025] the ion exchanger is at least one selected from the group consisting of sodium salt and potassium salt;

[0026] the plasticizer is at least one selected from the group consisting of o-nitrophenyl octyl ether, bis(2-ethylhexyl)adipate, bis(2-ethylhexyl)sebacate, and dibutyl phthalate;

[0027] the non-conductive polymer is at least one selected from the group consisting of polyvinyl chloride and polyurethane;

[0028] the ammonium ionophore is ammonium ionophore I.

[0029] [5]. A method for producing an ion-selective electrode, comprising:

[0030] (1) electrodepositing a conductive layer on a conductive substrate, the conductive substrate being a metal sheet,

[0031] (2) electrodepositing a solid-state contact layer on the conductive layer by using a solid-state contact layer-forming dispersion liquid, the solid-state contact layer-forming dispersion liquid including graphene quantum dots and a monomer for forming a conductive polymer,

[0032] (3) forming an ammonium ion-sensitive membrane on the solid-state contact layer.

[0033] [6]. The method for producing according to [5], wherein, in step (1), the conductive layer is formed on the surface of the conductive substrate by immersing the conductive substrate in a conductive layer-forming solution and using cyclic voltammetry; and / or

[0034] in step (2), the solid-state contact layer is formed on the surface of the conductive substrate by immersing the conductive substrate on which the conductive layer has been formed in the solid-state contact layer-forming dispersion liquid and using cyclic voltammetry; and / or

[0035] in step (3), an ammonium ion-sensitive membrane-forming solution is coated on the solid-state contact layer and dried.

[0036] [7]. The method for producing according to [6], wherein, in step (1), the conductive layer-forming solution is an aqueous metal salt solution; and / or

[0037] in step (1), in the cyclic voltammetry, the scan voltage interval ranges from 0 to (-1.5 V), and the scanning is performed 20 to 40 times.

[0038] [8]. The production method according to [6] or [7], wherein, in step (2), the solid-state contact layer forming dispersion liquid is obtained by preparing a graphene quantum dot dispersion liquid, adjusting the graphene quantum dot dispersion liquid to be acidic, and dissolving the monomer for forming the conductive polymer in the graphene quantum dot dispersion liquid adjusted to be acidic; and / or

[0039] In step (2), in the cyclic voltammetry, the scanning voltage interval range is 0 to 1 V, and the scanning is performed for 30 to 60 cycles.

[0040] [9]. The production method according to any one of [6] to [8], wherein, in step (3), the ammonium ion-sensitive membrane forming solution is obtained by dissolving an ion exchanger, a plasticizer, a non-conductive polymer, and an ammonium ion carrier in an organic solvent.

[0041]

[10] . A detection probe comprising: a connection seat, further comprising: the ion-selective electrode according to any one of [1] to [4], or the ion-selective electrode obtained by the production method according to any one of [5] to [9];

[0042] The ion-selective electrode is threadedly connected to the connection seat.

[0043] <<Effects of the Invention>>

[0044] The present application achieves the following technical effects through the above technical solutions.

[0045] In the present application, the solid-state contact layer in a solid-state structure makes the obtained electrode easy to replace; the metal sheet is used as the conductive base, which can more effectively provide support for the ammonium ion-sensitive membrane, the ammonium ion-sensitive membrane is not easy to deform and damage, and the contact area is also increased to improve the test sensitivity. In addition, graphene quantum dots and conductive polymers are used in the solid-state contact layer at the same time, the boundary effect, high specific surface area, high carrier mobility and high stability of graphene quantum dots can enhance the ion-electron conduction ability of the solid-state contact layer.

[0046] In addition, in the present application, the production method of the ion-selective electrode is simple, and especially the electrodeposition (such as cyclic voltammetry) process can be continuously used, so that the ion-selective electrode which is easy to replace, has high sensitivity and is not easy to deform and damage can be easily obtained. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 FIG. 1 shows a schematic diagram of an ion-selective electrode.

[0048] Figure 2 FIG. 4 shows a schematic flow chart of the production method of the ion-selective electrode of the present application.

[0049] Figure 3 The figure shows the relationship between the open-circuit voltage of the ammonium-sensitive electrode prepared in the examples and the reference electrode (Ag / AgCl electrode) and the ammonium chloride standard solution of different concentrations.

[0050] Figure 4 The figure shows the relationship between the open-circuit voltage of the ammonium-sensitive electrode prepared in the comparative example and the reference electrode (Ag / AgCl electrode) and the ammonium chloride standard solution of different concentrations.

[0051] Figure 5 An example of a detection probe is shown in the image.

[0052] <Explanation of Figure Markers>

[0053] 1 Ammonium ion sensitive membrane

[0054] 2 Solid contact layer

[0055] 3. Conductive substrate

[0056] 4. Conductive layer Detailed Implementation

[0057] Various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The term "exemplary" as used herein means "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments.

[0058] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In other instances, methods, means, apparatus, and steps well known to those skilled in the art have not been described in detail in order to highlight the spirit of the present invention.

[0059] Unless otherwise stated, all units used in this specification are international standard units, and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors that are unavoidable in industrial production.

[0060] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0061] In the present specification, reference to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", and the like, means that a particular element (e.g., feature, structure, property, and / or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and can or can not be present in other embodiments. In addition, it should be understood that the described elements can be combined in any suitable manner in the various embodiments.

[0062] In the present specification, a numerical range indicated using "numerical value A to numerical value B" means a range including the end point numerical values A, B. A numerical range indicated using "and above" and "and below" means a range including the end point numerical value. A numerical range indicated using "greater than" and "less than" means a range not including the end point numerical value.

[0063] In the present specification, "optional" or "optionally" means that the event or circumstance described next can or can not occur, and the description includes the case where the event occurs and the case where the event does not occur.

[0064] <<Ion selective electrode>>

[0065] The ion selective electrode of the present application includes: an electrically conductive base body, an electrically conductive layer, a solid contact layer, and an ammonium ion-sensitive membrane, which are sequentially stacked. The electrically conductive base body is a metal sheet, and the solid contact layer includes graphene quantum dots and an electrically conductive polymer.

[0066] In the present application, the electrically conductive base body, the electrically conductive layer, the solid contact layer, and the ammonium ion-sensitive membrane in the ion selective electrode can each have one or more layers.

[0067] In addition, the ion selective electrode further includes a housing. The electrically conductive base body, the electrically conductive layer, the solid contact layer, and the ammonium ion-sensitive membrane, and optionally other layers are housed in the housing. In addition, a mechanical member for connecting to other members, such as an internal thread, can be provided on the housing.

[0068] The following describes each structure in detail.

[0069] <Electrically conductive base body>

[0070] In the present application, the electrically conductive base body is a metal sheet, and the specific type of the metal sheet is not particularly limited as long as it is electrically conductive, such as aluminum, platinum, titanium, gold, silver, copper, nickel, cobalt, zinc, tin, and the like, and any combination of two or more of these metals.

[0071] In some preferred embodiments, the metal sheet is preferably at least one selected from the group consisting of a platinum sheet, a titanium sheet, or a titanium sheet plated with platinum.

[0072] <Electrically conductive layer>

[0073] In the present application, the conductive layer is not particularly limited, and various structures and compositions in the art can be employed. For example, the conductive layer can be formed directly on the conductive base, or can be formed on the conductive base with other layers interposed. For another example, the conductive layer can be a carbon layer, a metal layer, and a conductive polymer layer, etc.

[0074] Preferably, from the viewpoint of enhancing the microscopic contact area of the conductive layer with the solid-state contact layer, the conductive layer is preferably formed of nanoparticles of a conductive material.

[0075] In some preferred embodiments, from the viewpoint of enhancing the conductivity of the conductive base and the microscopic contact area of the conductive layer with the solid-state contact layer, the conductive layer is preferably composed of metal nanoparticles.

[0076] Examples of the kind of metal nanoparticles include, without limitation, aluminum nanoparticles, platinum nanoparticles, titanium nanoparticles, gold nanoparticles, silver nanoparticles, copper nanoparticles, nickel nanoparticles, cobalt nanoparticles, zinc nanoparticles, tin nanoparticles, etc. These particles can be used alone or in combination of two or more.

[0077] In some more preferred embodiments, from the viewpoint of better achieving the desired effects, the metal nanoparticles are more preferably at least one selected from the group consisting of copper nanoparticles and silver nanoparticles.

[0078] <solid-state contact layer>

[0079] In the present application, the solid-state contact layer includes graphene quantum dots and a conductive polymer. For example, the solid-state contact layer can be formed directly on the conductive layer, or can be formed on the conductive layer with other layers interposed.

[0080] Quantum dots (QDs) generally refer to nanocrystals with a radius less than or close to the exciton Bohr radius, and in particular to semiconductor nanocrystals.

[0081] The term "graphene quantum dots" refers to tiny graphene fragments with a size generally in the range of 1 to 10 nanometers, which are significantly different from single-layer or multi-layer graphene materials such as graphene oxide in physical, chemical, and electronic properties.

[0082] In the present application, the specific kind of conductive polymer is not particularly limited, and examples include, without limitation, polyacetylene, polyaniline, thiophene-based polymers, pyrrole-based polymers, (N-substituted pyrrolidine)-based polymers, etc.

[0083] In some preferred embodiments, from the viewpoint of better achieving the desired technical effects of the present application, the conductive polymer is preferably polyaniline.

[0084] In the present application, the composite form of the graphene quantum dots and the conductive polymer in the solid-state contact layer is not particularly limited. In some preferred embodiments, in the solid-state contact layer, the graphene quantum dots are dispersed in the conductive polymer as a matrix.

[0085] In the present application, the respective contents of the graphene quantum dots and the conductive polymer in the solid-state contact layer are not particularly limited and can be appropriately adjusted according to actual needs.

[0086] In some specific embodiments, the content of the graphene quantum dots is preferably 1 to 5 mass%, more preferably 2 to 3 mass%, relative to 100 mass% of the total mass of the solid-state contact layer.

[0087] In some specific embodiments, the content of the conductive polymer is preferably 95 to 99 mass%, more preferably 97 to 98 mass%, relative to 100 mass% of the total mass of the solid-state contact layer.

[0088] In addition, other components can also be included in the solid-state contact layer, such as carbon materials such as pristine graphene, graphene oxide, and reduced graphene oxide, and the like.

[0089] <Ammonium ion-sensitive film>

[0090] In the present application, the ammonium ion-sensitive film is not particularly limited and various structures and compositions in the art can be used. For example, the ammonium ion-sensitive film can be formed directly on the solid-state contact layer, or can be formed on the solid-state contact layer through other layers.

[0091] In some specific embodiments, the ammonium ion-sensitive film preferably includes an ion exchanger, a plasticizer, a non-conductive polymer, and an ammonium ion carrier.

[0092] The ion exchanger is not particularly limited and those known in the art can be used arbitrarily. In some specific embodiments, the ion exchanger can be at least one selected from the group consisting of sodium salts and potassium salts. As the sodium salt, for example, sodium tetraphenylborate or the like can be used. As the potassium salt, for example, potassium tetrakis(4-chlorophenyl)borate and potassium tetrakis(3,5-di(trifluoromethyl)phenyl)borate or the like can be used.

[0093] In some preferred embodiments, the content of the ion exchanger is preferably 0.5 to 3%, more preferably 1 to 2.5%, in mass percentage, relative to 100% of the total mass of the ammonium ion-sensitive film.

[0094] The plasticizer is not particularly limited and those known in the art can be arbitrarily used. Examples of the plasticizer include, but are not limited to, ortho-nitrophenyl octyl ether, alkanoate plasticizers, phthalate plasticizers. As the alkanoate plasticizer, for example, bis(2-ethylhexyl)adipate, bis(2-ethylhexyl)sebacate, di-n-octyl sebacate, or the like can be used. As the phthalate plasticizer, for example, dibutyl phthalate, dioctyl phthalate, or diisodecyl phthalate, or the like can be used.

[0095] In some preferred embodiments, the plasticizer is preferably at least one selected from the group consisting of ortho-nitrophenyl octyl ether, bis(2-ethylhexyl)adipate, bis(2-ethylhexyl)sebacate, and dibutyl phthalate, more preferably ortho-nitrophenyl octyl ether.

[0096] In some preferred embodiments, the content of the plasticizer is preferably 40 to 70%, more preferably 45 to 65% by mass with respect to the total mass 100% of the ammonium ion-sensitive membrane.

[0097] The non-conductive polymer is not particularly limited and those known in the art can be arbitrarily used. Examples of the non-conductive polymer include, but are not limited to, polyvinyl chloride, polyurethane, polyethylene terephthalate, polybutylene terephthalate, or the like.

[0098] In some preferred embodiments, the non-conductive polymer is preferably at least one selected from the group consisting of polyvinyl chloride and polyurethane, more preferably polyvinyl chloride.

[0099] In some preferred embodiments, the content of the non-conductive polymer is preferably 20 to 50%, more preferably 30 to 45% by mass with respect to the total mass 100% of the ammonium ion-sensitive membrane.

[0100] The ammonium ion carrier is not particularly limited and those known in the art can be arbitrarily used. In some preferred embodiments, the ammonium ion carrier is preferably ammonium ion carrier I.

[0101] In some preferred embodiments, the content of the ammonium ion carrier is preferably 0.1 to 5%, more preferably 0.3 to 4% by mass with respect to the total mass 100% of the ammonium ion-sensitive membrane.

[0102] In some particularly specific embodiments, the ammonium ion-sensitive membrane includes 1 to 2% by mass of potassium tetrakis(3,5-di(trifluoromethyl)phenyl)borate, 50 to 65% of ortho-nitrophenyl octyl ether, 30 to 40% of polyvinyl chloride, and 0.5 to 3.5% of the ammonium ion carrier.

[0103] <Other layer>

[0104] The ion-selective electrode of the present application can optionally include other layers, such as other conductive layers, isolation layers for protection, other ion-sensitive membranes, active layers disposed on each ion-sensitive membrane, and the like.

[0105] <Method for producing an ion-selective electrode>

[0106] The method for producing an ion-selective electrode of the present application includes: (1) electrodepositing a conductive layer on a conductive base, the conductive base being a metal sheet; (2) electrodepositing a solid-state contact layer on the conductive layer by using a solid-state contact layer-forming dispersion liquid, the solid-state contact layer-forming dispersion liquid including graphene quantum dots and a monomer for forming a conductive polymer; and (3) forming an ammonium ion-sensitive membrane on the solid-state contact layer.

[0107] Each step is described in detail below. An illustrative example is shown in Figure 1 and Figure 2 .

[0108] <Step (1)>

[0109] In step (1), a conductive layer is electrodeposited on a conductive base, the conductive base being a metal sheet.

[0110] In the present application, the details of the conductive base and the conductive layer are the same as those described above in the details of the conductive base and the conductive layer in the <<Ion-selective electrode>> section, and are not described again here.

[0111] In the present application, the term "on" (for example, "on the conductive base" here, and "on the conductive layer" and "on the solid-state contact layer" described later) means performing the operation above the member referred to, and does not mean performing the operation directly on the surface of the member referred to.

[0112] In the present application, the method of electrodepositing is not particularly limited. The method of electrodepositing can be constant potential deposition, constant current deposition, or cyclic voltammetry, and preferably, cyclic voltammetry is used.

[0113] In some specific embodiments, the conductive layer is formed on the surface of the conductive base by immersing the conductive base in a conductive layer-forming solution and using cyclic voltammetry.

[0114] In step (1), in some preferred embodiments, the conductive layer-forming solution is preferably an aqueous metal salt solution. The aqueous metal salt solution can be obtained by a method known in the art, for example, a metal salt can be dissolved in water to obtain an aqueous metal salt solution.

[0115] In some preferred embodiments, the aqueous metal salt solution is preferably at least one selected from the group consisting of an aqueous copper salt solution and an aqueous silver salt solution. As the aqueous copper salt solution, for example, an aqueous copper acetate solution, an aqueous copper nitrate solution, an aqueous copper sulfate solution, an aqueous copper chloride solution, and the like can be used. As the aqueous silver salt solution, for example, an aqueous silver acetate solution, an aqueous silver nitrate solution, an aqueous silver sulfate solution, an aqueous silver chloride solution, an aqueous silver oxalate solution, and the like can be used.

[0116] In other preferred embodiments, the concentration of the metal salt in the aqueous metal salt solution is 1 to 5 g / L, more preferably 2 to 4 g / L.

[0117] In step (1), the conditions for the cyclic voltammetry are not particularly limited. In some preferred embodiments, the scanning voltage interval ranges from 0 to (-1.5 V), and the scanning is performed 20 to 40 times.

[0118] In some particularly specific embodiments, step (1) includes the following: the above-described conductive substrate is used as a working electrode, a carbon electrode or a platinum electrode is used as an auxiliary electrode, a saturated calomel electrode is used as a reference electrode, the above-described electrodes are all immersed in the solution for forming a conductive layer, and electroplating is performed, the electroplating process scanning voltage interval: 0 to (-1.5 V), scanning speed: 50 mV / s, scanning: 20 to 40 times.

[0119] <Step (2)>

[0120] In step (2), a solid-state contact layer is electrodeposited on the conductive layer by using a dispersion liquid for forming a solid-state contact layer, the dispersion liquid for forming a solid-state contact layer including graphene quantum dots and a monomer for forming a conductive polymer.

[0121] In the present application, the details of the solid-state contact layer are the same as those described above in the details of the solid-state contact layer in the <<ion-selective electrode>> and will not be described here again.

[0122] In the present application, the method for performing the electrodeposition is not particularly limited. The electrodeposition method can be constant potential deposition, constant current deposition, or cyclic voltammetry, and preferably, cyclic voltammetry is used.

[0123] In some specific embodiments, the solid-state contact layer is formed on the surface of the conductive substrate by immersing the conductive substrate on which the conductive layer has been formed in the dispersion liquid for forming a solid-state contact layer and using cyclic voltammetry.

[0124] In step (2), the specific composition of the dispersion liquid for forming a solid-state contact layer is not particularly limited as long as it includes graphene quantum dots and a monomer for forming a conductive polymer.

[0125] In some preferred embodiments, the solid-state contact layer is formed by a dispersion liquid obtained by preparing a graphene quantum dot dispersion liquid, adjusting the graphene quantum dot dispersion liquid to be acidic, and dissolving the monomer for forming the conductive polymer in the graphene quantum dot dispersion liquid adjusted to be acidic.

[0126] The graphene quantum dot dispersion liquid can be obtained by any method known in the art. For example, the graphene quantum dot dispersion liquid can be obtained by a method in which a three-electrode system is used in a buffer solution, in which a graphite rod is used as a working electrode, and a constant voltage of 2 to 5 V is applied to oxidize and cut graphene sheets using radicals generated by water ionization, thereby obtaining a dark brown graphene quantum dot dispersion liquid.

[0127] As the buffer solution, those known in the art can be used, for example, a phosphate buffer solution such as a sodium dihydrogen phosphate (NaH2PO4) solution, a bicarbonate buffer solution such as a combination of sodium bicarbonate (NaHCO3) and sodium carbonate (Na2CO3).

[0128] In some more preferred embodiments, the graphene quantum dot dispersion liquid is adjusted to have a pH of <5, and more preferably, a pH of <4. The method for adjusting to be acidic is not particularly limited, and for example, an organic acid such as acetic acid, citric acid, or an inorganic acid such as hydrochloric acid, phosphoric acid, nitric acid can be added.

[0129] In some more preferred embodiments, the monomer for forming the conductive polymer (e.g., an aniline monomer) is dissolved in the graphene quantum dot dispersion liquid adjusted to be acidic in an amount of 0.1 to 1 M.

[0130] In addition, the dispersion method is not particularly limited, and those known in the art can be used, for example, ultrasonic irradiation, stirring, shaking, and the like.

[0131] In step (2), the conditions for the cyclic voltammetry are not particularly limited. In some preferred embodiments, the scan voltage interval ranges from 0 to 1 V, and is scanned for 30 to 60 cycles.

[0132] In some particularly specific embodiments, step (2) includes the following ① to ③:

[0133] ① A graphite rod is used as a working electrode, a platinum electrode is used as an auxiliary electrode, and a saturated calomel electrode is used as a reference electrode in a 0.1 M NaH2PO4 solution, and a constant voltage of 2 to 5 V is applied to oxidize and cut graphene sheets using radicals generated by water ionization, thereby obtaining a dark brown graphene quantum dot dispersion liquid.

[0134] (ii) The graphene quantum dot dispersion liquid is adjusted to pH < 4 with hydrochloric acid, and then an appropriate amount of aniline 0.1-1 M is added and ultrasonicated for 30-60 minutes to uniformly dissolve the aniline in the graphene quantum dot dispersion liquid, thereby obtaining a dispersion liquid for forming a solid contact layer.

[0135] (iii) The conductive substrate on which the conductive layer is formed is used as a working electrode, a carbon electrode or a platinum electrode is used as an auxiliary electrode, and a saturated calomel electrode is used as a reference electrode, and the electrodes are immersed in the dispersion liquid for forming a solid contact layer and subjected to electroplating, the electroplating process being performed at a scan voltage range of 0-1 V and a scan rate of 50 mV / s for 30-60 cycles.

[0136] <Step (3)>

[0137] In Step (3), an ammonium ion-sensitive membrane is formed on the solid contact layer.

[0138] In the present application, the details of the ammonium ion-sensitive membrane are the same as those described above in the details of the ammonium ion-sensitive membrane in the ion-selective electrode, and thus will not be described again.

[0139] In the present application, the method for forming the ammonium ion-sensitive membrane is not particularly limited and can be those known in the art.

[0140] In some specific embodiments, the solution for forming an ammonium ion-sensitive membrane is coated on the solid contact layer and dried.

[0141] In Step (3), the specific composition of the solution for forming an ammonium ion-sensitive membrane is not particularly limited. In some preferred embodiments, the solution for forming an ammonium ion-sensitive membrane is obtained by dissolving an ion exchanger, a plasticizer, a non-conductive polymer, and an ion carrier in an organic solvent.

[0142] Examples of the organic solvent include, but are not limited to, ether-based solvents such as tetrahydrofuran, ketone-based solvents such as butanone, acetone, and cyclohexanone, and the like. In some preferred embodiments, the organic solvent is preferably tetrahydrofuran, or a mixture of tetrahydrofuran and acetone.

[0143] The concentration of each component in the solution for forming an ammonium ion-sensitive membrane is not particularly limited and is appropriately adjusted depending on the kind of each component and the coating method.

[0144] In some specific embodiments, in the solution for forming an ammonium ion-sensitive membrane, the concentration of the ion exchanger is preferably 0.5-3%, and more preferably 1-2.5%, in terms of mass percentage, relative to the total amount of the solid components.

[0145] In some specific embodiments, the concentration of the plasticizer in the solution for forming an ammonium ion-sensitive membrane is preferably 40 to 70% by mass, more preferably 45 to 65% by mass, relative to the total amount of the solid components.

[0146] In some specific embodiments, the concentration of the non-conductive polymer in the solution for forming an ammonium ion-sensitive membrane is preferably 20 to 50% by mass, more preferably 30 to 45% by mass, relative to the total amount of the solid components.

[0147] In some specific embodiments, the concentration of the ion carrier in the solution for forming an ammonium ion-sensitive membrane is preferably 0.1 to 5% by mass, more preferably 0.3 to 4% by mass, relative to the total amount of the solid components.

[0148] The coating method is not particularly limited and those known in the art can be used, such as a spray coating method, a spin coating method, a drop coating method, a curtain coating method, and the like.

[0149] The drying method is not particularly limited and those known in the art can be used, such as natural air drying, heating air blowing, oven drying, and the like. The drying conditions can be, for example, as follows: the drying temperature is 20 to 80°C, and the drying time can be 1 hour to 24 hours.

[0150] In some particularly specific embodiments, step (2) comprises the following ① to ②:

[0151] ① Dissolve 1 to 2% of potassium tetrakis(3,5-di(trifluoromethyl)phenyl)borate, 50 to 65% of o-nitrophenyl octyl ether, 30 to 40% of polyvinyl chloride, and 0.5 to 3.5% of an ammonium ion carrier, relative to the total amount of the solid components, in an appropriate amount of tetrahydrofuran, and shake to mix them uniformly to obtain a solution for forming an ammonium ion-sensitive membrane.

[0152] ② Take 40 to 60 uL of the solution for forming an ammonium ion-sensitive membrane, spin coat or drop coat it on the solid contact layer, and dry it at 50°C for 10 to 20 hours.

[0153] In addition, since the ammonium ion-sensitive membrane is in a storage state before use or testing, the ammonium ion-sensitive membrane is usually activated by being immersed in a solution containing the corresponding ions at the time of use or testing. For example, in some specific embodiments, the ammonium-sensitive membrane tip can be activated by being soaked in a 0.01 M ammonium chloride solution for 6 to 12 hours.

[0154] <Other steps>

[0155] The production method of the present application can optionally include other steps, such as steps of washing and drying each of the above layers, forming any other layer on each of the above layers, and the like.

[0156] Detection probe

[0157] The detection probe of the present application comprises a connecting seat, and further comprises the ion-selective electrode as described above or obtained by the preparation method of the ion-selective electrode as described above. The ion-selective electrode is threadedly connected with the connecting seat.

[0158] The detection probe of the present application can be applied in the detection of ion concentration in water environment. The water environment can be water in sewage treatment or storage pool, lake water, river water or sea water, etc.

[0159] The detection probe provided by the present application takes the ion-selective electrode of the present application as a working electrode. The working principle is that the ion-selective electrode can convert the activity (input) of the ion to be detected in the sample solution to be detected into a potential signal (output). The change of the potential signal can be obtained by measuring the open circuit voltage of the electrode in the sample to be detected, which is proportional to the ion concentration in the sample to be detected, and then the content of the ion to be detected is calculated.

[0160] In addition, the detection probe can have any structure known in the art. For example, one example of the detection probe of the present application is shown in the following Figure 5

[0161] Embodiment

[0162] The embodiments of the present application will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. The specific conditions not mentioned in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not marked with the manufacturer, which are all conventional products that can be obtained by market purchase.

[0163] <<Example>>:

[0164] 1. Constructing the conductive layer

[0165] Conductive substrate: platinum electrode wafer

[0166] Solution for forming the conductive layer: copper acetate solution with a concentration of 2 g / L

[0167] Construction method: cyclic voltammetry, the conductive substrate as described above is used as a working electrode, a carbon electrode or a platinum electrode is used as an auxiliary electrode, and a saturated calomel electrode is used as a reference electrode. The above electrodes are all immersed in the solution for forming the conductive layer as described above; the scanning voltage range of the electroplating process is 0-1.2 V, the scanning speed is 50 mV / s, and the scanning is 24 circles. After the electroplating is completed, the conductive substrate is rinsed with deionized water and then used, and a conductive substrate with uniform coverage of copper nanoparticles on the surface is obtained.

[0168] 2. Constructing the solid contact layer ​

[0169] Preparation of graphene quantum dots solution: In 0.1M NaH2PO4 solution, graphite rod as working electrode, platinum electrode as auxiliary electrode, saturated calomel electrode as reference electrode, 3V constant voltage is applied to generate free radicals by water ionization to oxidize and cut graphene sheets, thereby obtaining dark brown graphene quantum dots solution.

[0170] Preparation of dispersion liquid for forming solid-state contact layer: After adjusting the above graphene quantum dots solution to be acidic (pH<4) with hydrochloric acid, a proper amount of aniline 0.5M is added and ultrasonic is applied for 30 minutes, so that aniline is uniformly dispersed in the graphene quantum dots solution.

[0171] Construction method: cyclic voltammetry, the above conductive substrate with conductive layer is used as working electrode, carbon electrode as auxiliary electrode, saturated calomel electrode as reference electrode, all of the above electrodes are immersed in the above dispersion liquid for forming solid-state contact layer; plating process scanning voltage range: 0-0.5V, scanning speed: 50mV / s, scanning 40 times. After plating, deionized water and ethanol are used for cleaning, and then natural drying is performed for 6H for standby, thereby obtaining the solid-state contact layer of polyaniline with uniformly dispersed graphene quantum dots.

[0172] 3. Construction of ammonium sensitive layer

[0173] Solution for forming ammonium sensitive layer: 1% of potassium tetrakis(3,5-di(trifluoromethyl)phenyl)borate (KTFPB), 60% of o-nitrophenyl octyl ether, 38% of PVC, 1% of ammonium ion carrier I are dissolved in a proper amount of tetrahydrofuran, oscillation is performed to make them uniformly mixed, and then they are stored in refrigerator.

[0174] Construction method: 50uL of the solution for forming ammonium sensitive layer is spin-coated on the solid-state contact layer, and drying is performed at 50℃ for 18H. Before testing, the head of ammonium sensitive membrane is soaked in 0.01M ammonium chloride solution for activation for 12H.

[0175] <<Comparative example>>

[0176] 1. Construction of conductive layer

[0177] Conductive substrate: platinum electrode wafer

[0178] Solution for forming conductive layer: copper acetate solution with a concentration of 2g / L

[0179] Construction method: cyclic voltammetry, the above conductive substrate is used as working electrode, carbon electrode as auxiliary electrode, saturated calomel electrode as reference electrode, all of the above electrodes are immersed in the above solution for forming conductive layer; plating process scanning voltage range: 0- -1.2V, scanning speed: 50mV / s, scanning 24 times. After plating, deionized water is used for cleaning, and then standby is performed, thereby obtaining the conductive substrate with copper nanoparticles uniformly covering the surface.

[0180] 2. Constructing solid-state contact layer

[0181] Solid-state contact layer forming dispersion liquid: deionized water was adjusted to be acidic (pH < 4) with hydrochloric acid, and an appropriate amount of aniline 0.5M was added and ultrasonic treated for 30 minutes to uniformly disperse the aniline.

[0182] Construction method: cyclic voltammetry, the above-mentioned conductive substrate on which the conductive layer was constructed was used as the working electrode, a carbon electrode was used as the auxiliary electrode, and a saturated calomel electrode was used as the reference electrode, all of which were immersed in the above-mentioned solid-state contact layer forming dispersion liquid; the scanning voltage range of the electroplating process was 0-0.5V, the scanning speed was 50mV / s, and the scanning was performed for 40 cycles. After electroplating, the product was washed with deionized water and ethanol respectively and then naturally dried for 6H for standby, to obtain a polyaniline solid-state contact layer.

[0183] 3. Constructing ammonium sensitive layer

[0184] Ammonium sensitive layer forming solution: 1% potassium tetrakis (3, 5-di (trifluoromethyl) phenyl) borate (KTFPB), 60% o-nitrophenyl octyl ether, 38% PVC, 1% ammonium ion carrier I were dissolved in an appropriate amount of tetrahydrofuran, and then oscillated to mix uniformly and stored in a refrigerator.

[0185] Construction method: 50uL of the ammonium sensitive layer forming solution was spin-coated on the solid-state contact layer, and dried at 50℃ for 18H. Before testing, the head of the ammonium sensitive membrane was soaked in a 0.01M ammonium chloride solution for activation for 12H.

[0186] <<Test method>>

[0187] The ammonium sensitive electrodes respectively prepared in the examples and the comparative examples were respectively placed with a reference electrode (Ag / AgCl electrode) in different concentrations of ammonium chloride standard solution, to obtain the relationship between the open circuit voltage (vertical axis) between the ammonium sensitive electrode and the reference electrode and different concentrations of ammonium chloride standard solution (horizontal axis: common logarithm of ammonium ion concentration), which are shown in Figure 3 and Figure 4 .

[0188] Figure 3 The linear range was 0.18-180mg / L, the detection lower limit was 0.18mg / L, the sensitivity was 52.28mV / decade (decade: order of magnitude), and the square of R (R 2 ) could reach 0.9992.

[0189] Figure 4 The linear range was 1.8-180mg / L, the detection lower limit was 1.8mg / L, the sensitivity was 47.258mV / decade (decade: order of magnitude), and the square of R (R 2 ) was 0.9861, which wasFigure 3 Comparatively low.

[0190] wherein, square of R (R 2 ) represents linearity, the closer to 1 represents the higher linearity in the detection range, and the accuracy will be higher accordingly.

[0191] It should be noted that although the technical solutions of the present application are described with specific examples, those skilled in the art can understand that the present application should not be limited thereto.

[0192] The above has described the embodiments of the present application, the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. The selection of the terms used herein is intended to best explain the principles of the embodiments, practical application or improvement of the technology in the market, or to enable other ordinary skilled in the art to understand the embodiments disclosed herein.

Claims

1. An ion-selective electrode, characterized in that The ion-selective electrode comprises: an electrically conductive substrate, an electrically conductive layer, a solid-state contact layer, and an ammonium ion-sensitive membrane which are sequentially stacked, The electrically conductive substrate is a metal sheet, The solid-state contact layer comprises graphene quantum dots and an electrically conductive polymer.

2. The ion-selective electrode according to claim 1, characterized in that The metal sheet is at least one selected from a platinum sheet, a titanium sheet, or a titanium sheet plated with platinum; and / or The electrically conductive polymer is polyaniline.

3. The ion-selective electrode according to claim 1 or 2, characterized in that The electrically conductive layer is composed of metal nanoparticles; and / or The ammonium ion-sensitive membrane comprises an ion exchanger, a plasticizer, a non-conductive polymer, and an ammonium ion carrier.

4. The ion-selective electrode according to claim 3, characterized in that The metal nanoparticles are at least one selected from copper nanoparticles and silver nanoparticles; The ion exchanger is at least one selected from sodium salt and potassium salt; The plasticizer is at least one selected from o-nitrophenyl octyl ether, bis(2-ethylhexyl)adipate, bis(2-ethylhexyl)sebacate, and dibutyl phthalate; The non-conductive polymer is at least one selected from polyvinyl chloride and polyurethane; The ammonium ion carrier is ammonium ion carrier I.

5. A method of preparing an ion-selective electrode, characterized by, Comprising: (1) electrodepositing an electrically conductive layer on an electrically conductive substrate, the electrically conductive substrate being a metal sheet, (2) electrodepositing a solid-state contact layer on the electrically conductive layer by using a solid-state contact layer-forming dispersion liquid, the solid-state contact layer-forming dispersion liquid comprising graphene quantum dots and a monomer for forming an electrically conductive polymer, (3) forming an ammonium ion-sensitive membrane on the solid-state contact layer.

6. The preparation method according to claim 5, characterized in that, In step (1), the electrically conductive layer is formed on the surface of the electrically conductive substrate by immersing the electrically conductive substrate in an electrically conductive layer-forming solution and using cyclic voltammetry; and / or In step (2), the solid-state contact layer is formed on the surface of the electrically conductive substrate by immersing the electrically conductive substrate on which the electrically conductive layer has been formed in the solid-state contact layer-forming dispersion liquid and using cyclic voltammetry; and / or In step (3), an ammonium ion-sensitive membrane-forming solution is coated on the solid-state contact layer and dried.

7. The production method according to claim 6, wherein In step (1), the electrically conductive layer-forming solution is an aqueous metal salt solution; and / or In the cyclic voltammetry in step (1), the scanning voltage interval ranges from 0 to (-1.5 V), and scanning is performed for 20 to 40 cycles.

8. The production method according to claim 6 or 7, characterized by, In step (2), the solid-state contact layer-forming dispersion liquid is obtained by preparing a graphene quantum dot dispersion liquid, adjusting the graphene quantum dot dispersion liquid to be acidic, and dissolving the monomer for forming an electrically conductive polymer in the graphene quantum dot dispersion liquid adjusted to be acidic; and / or In the cyclic voltammetry in step (2), the scanning voltage interval ranges from 0 to 1 V, and scanning is performed for 30 to 60 cycles. In step (3), the ammonium ion-sensitive membrane-forming solution is obtained by dissolving an ion exchanger, a plasticizer, a non-conductive polymer, and an ammonium ion carrier in an organic solvent.

9. The production method according to any one of claims 6 to 8, characterized by, Comprising:

10. A detection probe, characterized by, The connecting seat further comprises: the ion-selective electrode according to any one of claims 1-4, or the ion-selective electrode obtained by the preparation method according to any one of claims 5-9; The ion-selective electrode is threadedly connected with the connecting seat. ​

Images