KR20220043512A - Reference electrode for ion measuring sensor and manufacturing method thereof - Google Patents

Abstract

A reference electrode for an ion measurement sensor according to an embodiment of the present invention includes graphene containing a fluorine functional group treated with fluoro-benzene. An object of the present invention is to provide the reference electrode for an ion measurement sensor manufactured by one-time printing and coating.

Description

Reference electrode for ion measuring sensor and manufacturing method thereof

The present invention relates to a reference electrode for an ion measurement sensor including graphene containing a fluorine functional group treated with fluorine-benzene, and a method for manufacturing the same

An ion measuring sensor that detects ions in a solution containing ions requires a reference electrode capable of applying a constant potential in the solution.

However, since the Ag/AgCl reference electrode, which is a generally used standard electrode, contains a bar-shaped glass material and a silver bar, it is easy to break, expensive, and difficult to manufacture micro-sized electrodes.

Although a method of printing an Ag/AgCl electrode used as a reference electrode in a liquid phase has been developed for manufacturing a micro-sized electrode, the printed Ag/AgCl electrode is unstable, so reproducibility and reliability are problematic.

In addition, when used in an ion sensing field effect transistor (ISFET)-based ion measurement sensor, there is a problem that it is difficult to be compatible with the ion sensing field effect transistor (ISFET) manufacturing process due to the structure and shape of Ag/AgCl.

Patent Publication No. 10-2014-0103022

An object of the present invention is to provide a reference electrode for an ion measuring sensor with improved reproducibility and reliability without exhibiting sensitivity to not only hydrogen ions present in a solution but also sodium ions, calcium ions, potassium ions, and the like.

An object of the present invention is to provide a reference electrode for an ion measurement sensor manufactured by one printing and application.

An object of the present invention is to provide a reference electrode for an ion measuring sensor that is easily manufactured by being compatible with a semiconductor manufacturing process for manufacturing the ion measuring sensor.

An object of the present invention is to provide a reference electrode for an ion measuring sensor manufactured without being limited by equipment/space/processing area.

An object of the present invention is to provide a reference electrode for a micro-sized ion measuring sensor.

A reference electrode for an ion measuring sensor according to an embodiment of the present invention includes graphene including a fluorine functional group treated with fluorine-benzene.

The graphene according to an embodiment of the present invention may be non-oxidized graphene or reduced graphene oxide (rGo).

The graphene containing the fluorine functional group treated with the fluorine-benzene according to an embodiment of the present invention is a fluorine-benzene (Fluoro-benzene) solution in which non-oxidized graphene powder or reduced graphene oxide powder is dispersed. may have been formed.

The reference electrode for the ion measurement sensor according to the embodiment of the present invention may further include a substrate, and the fluorine-benzene-treated non-oxidized graphene or reduced graphene oxide containing a fluorine functional group is powder It may be applied to the substrate in the form of.

The graphene containing the fluorine functional group treated with the fluorine-benzene according to an embodiment of the present invention is a fluorine-benzene solution on a non-oxidized graphene sheet or a reduced graphene oxide sheet. It may be formed by coating.

The reference electrode for an ion measurement sensor according to an embodiment of the present invention may further include a substrate, and the fluorine-benzene-treated non-oxidized graphene or reduced graphene oxide-containing fluorine functional group is a sheet. It may be formed on the substrate in the form.

Ions of the ion measuring sensor according to an embodiment of the present invention may be, for example, hydrogen ions, sodium ions, calcium ions, potassium ions, magnesium ions, nitrate ions, sulfate ions, chlorine ions, halogen ions, ammonium ions, and the like.

The ion measuring sensor according to an embodiment of the present invention may be an ion sensing field effect transistor (ISFET) based ion measuring sensor.

A method for manufacturing a reference electrode for an ion measurement sensor according to an embodiment of the present invention includes depositing a gold (Au) electrode on a substrate; and coating the graphene containing the fluorine functional group treated with the fluoro-benzene on the substrate or a gold (Au) electrode deposited on the substrate; including, wherein the fluorine functional group is included In the step of applying the graphene, the non-oxide graphene or reduced graphene oxide containing the fluorine functional group treated with the fluorine-benzene is applied on the substrate in powder form, and the fluorine-benzene (Fluoro-benzene) is applied on the substrate. -benzene)-treated graphene containing a fluorine functional group is formed by dispersing non-oxidized graphene powder or reduced graphene oxide powder in a fluoro-benzene solution (fluoro-benzene).

A method for manufacturing a reference electrode for an ion measurement sensor according to an embodiment of the present invention includes: forming a graphene sheet on a substrate; depositing a gold (Au) electrode on a portion of the graphene sheet ; and applying a fluoro-benzene solution on the graphene sheet to prepare graphene containing a fluorine functional group treated with fluoro-benzene; including, the graphene The fin sheet is a non-oxidized graphene sheet or a reduced graphene oxide sheet.

The present invention provides a reference electrode for an ion measuring sensor with improved reproducibility and reliability without exhibiting sensitivity to not only hydrogen ions present in a solution but also sodium ions, calcium ions, potassium ions, and the like.

The present invention provides a reference electrode for an ion measurement sensor manufactured by one printing and application.

The present invention provides a reference electrode for an ion measuring sensor that is easily manufactured by being compatible with a semiconductor manufacturing process for manufacturing the ion measuring sensor.

The present invention provides a reference electrode for an ion measuring sensor that is manufactured without being limited by equipment/space/processing area.

An object of the present invention is to provide a reference electrode for a miniaturized ion measuring sensor.

1 shows a reduced graphene oxide powder manufacturing process including a fluorine functional group according to Example 1 of the present invention.
2 shows an ion measuring sensor to which a reference electrode according to Example 1 of the present invention is applied.
3 is a graph comparing the sensitivity to ions of the reference electrode according to Comparative Example and Example 1 of the present invention.
4 is a graph comparing the sensitivity to ions of the reference electrode according to Comparative Example and Example 1 of the present invention.
5 is a graph comparing the sensitivity to ions of the reference electrode according to Comparative Example and Example 1 of the present invention.
6 is a graph comparing the sensitivity to ions of the reference electrode according to Comparative Example and Example 1 of the present invention.
7 shows a graphene sheet manufacturing process including a fluorine functional group according to Example 2 of the present invention.
8 shows a reference electrode according to Example 2 of the present invention.
9 is a graph showing results of Raman spectroscopy analysis of graphene sheets according to Comparative Examples and Example 2 of the present invention.
10 is a graph comparing the contact angle with water of the graphene sheet according to Comparative Example and Example 2 of the present invention.
11 is a graph showing the result of characteristic change with respect to the ion concentration of the reference electrode according to Comparative Example and Example 2 of the present invention.
12 is a graph comparing the sensitivity to ions of the reference electrode according to Comparative Example and Example 2 of the present invention.
13 is a graph comparing the sensitivity to ions of the reference electrode according to Comparative Example and Example 2 of the present invention.
14 shows a manufacturing process of a reference electrode according to Example 2 of the present invention.
15 is a reference electrode according to Embodiment 2 of the present invention and an example of application thereof to a G-ISFET.
16 is an example of a method for measuring ions in a solution by applying a reference electrode according to Example 2 of the present invention to a G-ISFET.
17 is a graph evaluating the sensitivity to ions of the reference electrode according to Example 2 of the present invention.
18 is an example of detecting a change in the real-time ion concentration of the reference electrode according to Example 2 of the present invention.

Hereinafter, the present invention will be described in more detail through examples. It should not be construed that the scope of the present invention is limited by these examples.

Expressions such as "comprising" as used herein should be understood as open-ended terms, including the possibility of including other embodiments.

As used herein, “preferred” and “preferably” refer to embodiments of the invention that may provide certain advantages under certain circumstances. The recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the invention.

In the present specification, when a member is said to be positioned 'on' another member, this includes not only a case in which a member is in contact with another member but also a case in which another member exists between the two members.

A reference electrode for an ion measuring sensor according to an embodiment of the present invention includes graphene including a fluorine functional group treated with fluorine-benzene.

The reference electrode is a fluorine-functionalized graphene, and since it does not show sensitivity to changes in ion concentration, it can maintain a constant potential, thereby providing reference sensitivity for the ion measurement sensor.

The fluorine functionalization degree increases as the atomic ratio of fluorine atoms forming a C-F bond to carbon atoms increases, and as the fluorine functionalization degree increases, reproducibility and reliability as a reference electrode increase.

The graphene according to an embodiment of the present invention may be non-oxidized graphene or reduced graphene oxide (rGo).

When the graphene is reduced graphene oxide, as an example, it may be prepared by reducing graphene oxide and then introducing a fluorine functional group to the surface of the reduced graphene oxide. Alternatively, the fluorine functional group may be introduced to the graphene oxide surface and then reduced, or may be prepared by simultaneously attaching and reducing the functional group.

The graphene containing a fluorine functional group according to an embodiment of the present invention is formed by fluorine-benzene treatment, which is performed by the following mechanism.

Benzene group derivatives can be functionalized without damage to the graphene surface by non-covalent bonding by electrostatic attraction through π-π interaction. Graphene has an sp2 hybridized carbon structure, and each carbon atom has π electrons and has an electron cloud due to delocalization. The benzene group also has an electron cloud due to the π electrons of the hexagonal benzene ring like graphene. Therefore, a non-covalent bond is formed by the π-π interaction between the electron cloud on the surface of graphene having a continuous π bond structure and the electron cloud of fluorbenzene.

In the fluorine-benzene (Fluoro-benzene), a fluorine atom is substituted for the hydrogen of benzene, and the number of substitutions is 1 to 6.

By functionalizing the fluorine-benzene-treated graphene with fluorine, it does not exhibit sensitivity to not only hydrogen ions in the solution but also sodium ions, calcium ions and potassium ions, and is stably maintained even after long-term use.

In addition, the method of manufacturing graphene containing fluorine functional groups by fluorine-benzene treatment enables fluorine functionalization within a short time compared to fluorine plasma treatment techniques, and fluorine functionalization of large-area graphene is convenient. can do.

The reference electrode for an ion measurement sensor according to an embodiment of the present invention is, as an example, a graphene powder containing a fluorine functional group treated with fluorine-benzene, or a fluorine-benzene treated It may include a graphene sheet (sheet) containing a fluorine functional group.

As an example, the fluorine-benzene (Fluoro-benzene)-treated graphene containing a fluorine functional group is formed by dispersing non-oxidized graphene powder or reduced graphene oxide powder in a fluoro-benzene solution (Fluoro-benzene). can be (see FIG. 2).

As such, when the graphene containing the fluorine functional group exists in the form of powder, it can be used in the form of ink to have a reference electrode function through a single printing and application process.

In the present invention, the reduced graphene oxide powder can be dispersed in a fluorine-benzene solution to prepare reduced graphene oxide containing a fluorine functional group, and the process is shown in FIG. 1 .

At this time, as an embodiment, the graphene powder may be dispersed in an amount of 30 to 70 mg in 1 ml of a fluoro-benzene solution, or 40 to 60 mg in 1 ml. At this time, if it is less than the above weight range, the electrode must be manufactured by repeated application, and if it exceeds the above weight range, application is difficult due to viscosity. In addition, as a reference electrode in the above weight range, reproducibility and reliability are increased, and ion sensitivity can be effectively controlled.

The reference electrode for an ion measurement sensor according to an embodiment of the present invention may further include a substrate, and the fluorine-benzene-treated non-oxidized graphene or reduced graphene oxide containing a fluorine functional group is powder It may be applied to the substrate in the form of.

The substrate may be a material selected from the group consisting of silicon, glass, metal, plastic, and ceramic, but is not particularly limited thereto. As an example, the substrate may be selected from the group consisting of silicon, glass, polystyrene, polymethylacrylate, polycarbonate, and ceramic.

The thickness of the coating layer may vary depending on the concentration of the solution in which the graphene powder is dispersed. As an example, the thickness of the coating layer may be 10 μm to 1,000 μm, and the degree of fluorine functionalization increases in the weight range to increase reproducibility and reliability as a reference electrode, and ion sensitivity can be effectively controlled.

In an embodiment of the present invention, since non-oxidized graphene or reduced graphene oxide is applied on a substrate in powder form to form a reference electrode, non-oxidized graphene or reduced graphene containing a fluorine functional group is applied only by one application or printing process. It is possible to form a graphene oxide reference electrode.

In addition, the process using graphene powder is compatible with semiconductor manufacturing processes such as a stencil technique, so that a reference electrode for an ion measurement sensor can be manufactured in a simple and economical process.

In addition, in the process using graphene powder, since fluorine functionalization is possible only by reacting at room temperature compared to the process using graphene sheets, a separate process for fluorine functionalization is not required. A gold electrode may be deposited on the substrate, and non-oxidized graphene or reduced graphene oxide containing a fluorine functional group treated with fluoro-benzene may also be formed on the gold electrode in the form of powder. . The gold electrode is for forming an ohmic contact when a voltage is applied to a reference electrode including graphene including a fluorine functional group.

In addition, a protective layer or an insulating layer for protecting the gold electrode from an ion solution may be formed on the gold electrode. As an example, the protective layer may be formed of an epoxy resin or a similar polymer material.

In addition, as an example, the fluorine-benzene (Fluoro-benzene)-treated graphene containing a fluorine functional group is coated with a fluorine-benzene solution on a non-oxidized graphene sheet or a reduced graphene oxide sheet. It may be formed as a result (see FIG. 8).

More preferably, the graphene may be non-oxidized graphene. This is because, when the graphene surface is oxidized, electrons are lost in the hexagonal rings of graphene and the free electron cloud is reduced, so that the π-π interaction can be more active in the non-oxidized graphene.

The reference electrode for an ion measurement sensor according to an embodiment of the present invention may further include a substrate, and the fluorine-benzene-treated non-oxidized graphene or reduced graphene oxide-containing fluorine functional group is a sheet. It may be formed on the substrate in the form.

As an example, when the graphene including the fluorine functional group exists in the form of a sheet, the graphene sheet formed on the substrate is fluorine-functionalized by fluorine-benzene treatment.

The graphene sheet including the fluorine functional group may include a fluoro-benzene solution on the graphene sheet formed on the substrate.

This may be fluorine-functionalized by a process such as applying a fluoro-benzene solution to the graphene sheet formed on the substrate (see FIG. 7 ).

In this case, the substrate may be a material selected from the group consisting of silicon, glass, metal, plastic, and ceramic, but is not particularly limited thereto. As an example, the substrate may be selected from the group consisting of silicon, glass, polystyrene, polymethylacrylate, polycarbonate, and ceramic.

As described above, the method of applying fluorine-benzene solution to the graphene sheet formed on the substrate for fluorine functionalization is possible in a short period of time compared to the fluorine plasma treatment technique. Graphene of the area can be easily functionalized with fluorine.

In addition, since graphene is functionalized directly with a fluoro-benzene solution, it is not limited in equipment, space, and processing area compared to plasma processing techniques.

In addition, in comparison with the fluorine plasma treatment technique, fluorine functionalization is possible within a short time, and graphene of a large area can be conveniently functionalized with fluorine.

In addition, a gold (Au) electrode may be deposited on the substrate or on the non-oxidized graphene or reduced graphene oxide sheet including the fluorine functional group. The gold electrode is for forming an ohmic contact when a voltage is applied to a reference electrode including graphene including a fluorine functional group.

In addition, a protective layer or an insulating layer for protecting the gold electrode from an ion solution may be formed on the gold electrode. As an example, the protective layer may be formed of an epoxy resin or a similar polymer material.

The ion of the ion measuring sensor to which the reference electrode according to the embodiment of the present invention is applied may be a hydrogen ion, a sodium ion, a calcium ion, or a potassium ion. Since the present invention treats non-oxidized graphene or reduced graphene oxide with a fluorine-benzene solution for functionalization with fluorine, it does not show sensitivity to H ⁺ as well as K ⁺ , Na ⁺ , and Ca ^{2 +} ions. It is possible to provide a stable reference electrode even for long-term use.

As a more preferred example, the ion measuring sensor may be an ion sensing field effect transistor (ISFET) based ion measuring sensor.

As an example, the 　 ion sensing field 　 effect transistor may include a substrate; insulating layer; a source electrode and a drain electrode spaced apart from each other; It may include a channel layer disposed between the source electrode and the drain electrode (see FIGS. 15 and 16 ).

A method for manufacturing a reference electrode for an ion measurement sensor according to an embodiment of the present invention includes depositing a gold (Au) electrode on a substrate; and coating the graphene containing the fluorine functional group treated with the fluoro-benzene on the substrate or a gold (Au) electrode deposited on the substrate; including, wherein the fluorine functional group is included In the step of applying the graphene, the non-oxide graphene or reduced graphene oxide containing the fluorine functional group treated with the fluorine-benzene is applied on the substrate in powder form, and the fluorine-benzene (Fluoro-benzene) is applied on the substrate. -benzene)-treated graphene containing functional groups is formed by dispersing non-oxidized graphene powder or reduced graphene oxide powder in a fluoro-benzene solution. Its preparation method has been described above.

In addition, the method for manufacturing a reference electrode for an ion measurement sensor according to an embodiment of the present invention includes forming a graphene sheet on a substrate; gold (Au) on a part of the graphene sheet depositing an electrode; and applying a fluoro-benzene solution on the graphene sheet to prepare graphene containing a fluorine functional group treated with fluoro-benzene; including, the graphene The fin sheet is a non-oxidized graphene sheet or a reduced graphene oxide sheet (see FIG. 14 ). Its preparation method has been described above.

Example 1 : Preparation of a reference electrode including a material containing reduced graphene oxide powder containing a fluorine functional group by fluorine-benzene treatment.

In 1 ml of fluorine-benzene, 50 mg or less of reduced graphene oxide powder was mixed and sonicated at room temperature for 1 h to prepare an ink in which reduced graphene oxide was dispersed. 10 ul of graphene powder-based ink prepared after sonication was printed or applied on the gold electrode using equipment such as a pipette or inkjet printer.

In this case, an insulating film forming process may be required depending on the shape of the gold electrode. Although a separate insulating film forming process is not required for the form shown in FIG. 2 , the insulating film region may be formed of an epoxy or similar polymer material when manufactured in the same form as the structure shown in FIG. 14 .

Comparative Example 1-1:.

A commonly used standard Ag/AgCl electrode was used as a reference electrode.

Comparative Example 1-2 : Preparation of a reference electrode comprising pure reduced graphene oxide powder not containing a fluorine functional group.

Pure reduced graphene oxide powder that does not contain fluorine functional groups was prepared as a dispersed graphene ink based on an organic solvent.

50 mg of pure reduced graphene oxide powder was put in 1 ml of tetrahydrofuran and ultrasonicated for 1 h to prepare an ink. In this case, as a solution for dispersing the pure reduced graphene oxide powder, an organic solvent such as acetone, ethanol, methanol, or dimethylformamide may be used.

10 ul of graphene powder-based ink prepared after sonication was printed or applied on the gold electrode using equipment such as a pipette or inkjet printer.

In this case, an insulating film forming process may be required depending on the shape of the gold electrode. Although a separate insulating film forming process is not required for the form shown in FIG. 2 , an insulating film may be formed of an epoxy or similar polymer material when manufactured in the same form as the structure shown in FIG. 14 .

Experimental example One

The results of comparing the sensitivity (a) to sodium ions of the reference electrode according to Comparative Example 1-1 (a), Comparative Example 1-2 (b), and Example 1 (c) are shown in FIGS. 3 to 6 . .

3 to 6 , in the case of Comparative Example 1-1 using Ag/AgCl, a small amount of V _GS deviation is shown every week according to the increase or decrease of the sodium ion concentration in the solution. In addition, it can be confirmed that the measured sensitivity is non-linear and does not have sensitivity to a change in sodium ion concentration.

In the case of Example 1, as in Comparative Example 1-1 using Ag/AgCl, a small amount of V _GS deviation was exhibited weekly in the increase and decrease of the sodium ion concentration. Therefore, it can be confirmed that the reduced pure graphene reference electrode containing fluorine functional groups treated with fluorine-benzene does not have sensitivity to changes in sodium ion concentration.

In contrast, in the case of Comparative Example 1-2, V _GS with respect to the increase in sodium ion concentration It can be confirmed that the amount of change is large, and it can be seen that the reduced oxidation graph without fluorine-benzene has sensitivity to ions and is difficult to be used as a reference electrode material.

Example 2 : Preparation of a reference electrode including a non-oxidized graphene sheet including a fluorine functional group by fluorine-benzene treatment.

Before fluorine treatment, an electrode was formed on the graphene sheet by depositing gold in an area except for the size of 500 * 5000 um. In this case, the size of the sheet exposed to the solution may be changed according to measurement conditions and manufacturing processes.

A 99% fluorine-benzene solution was applied on the graphene sheet on which the gold electrode was deposited through a pipette or micro-droplet method. After the fluorine-benzene on the surface was completely dried (it takes several minutes), an insulating film was formed on the gold electrode part using an epoxy or similar polymer material.

Depending on the manufacturing process, the fluorine-benzene treatment may be performed after forming the insulating layer.

Comparative Example 2 : Preparation of a reference electrode comprising a pure non-oxidized graphene sheet not containing a fluorine functional group

An electrode was formed on the graphene sheet by depositing gold in the region except for the size of 500 * 5000 um. Thereafter, an insulating film was formed on the gold electrode part using an epoxy or similar polymer material. In this case, the size of the sheet exposed to the solution may be changed according to measurement conditions and manufacturing processes.

Experimental example 2

Referring to FIG. 9 , the carbon structures of Example 2 and Comparative Example 2 can be confirmed by Raman spectroscopy.

Referring to FIG. 10 , it can be seen that Example 2 has a larger water contact angle compared to Comparative Example 2, because hydrophobicity is increased by functionalizing pure graphene with fluorine.

Referring to FIG. 11 , in the case of Example 2, as compared to Comparative Example 2, it can be confirmed that there is no sensitivity according to the change in acidity.

12 and 13, in the case of Example 2, compared with Comparative Example 2, it can be confirmed that there is no sensitivity according to the concentration change to all of the sodium ion, potassium ion and calcium ion.

Referring to FIGS. 17 to 18 , in the case of Example 2, it can be seen that the V _GS deviation constantly decreases over time.

Claims (10)

Graphene containing a fluorine functional group treated with fluorine-benzene; including,
Reference electrode for ion measurement sensors.
The method of claim 1,
The graphene is non-oxidized graphene or reduced graphene oxide (rGo),
Reference electrode for ion measurement sensors.
The method of claim 1,
The fluorine-benzene (Fluoro-benzene)-treated graphene containing a fluorine functional group is formed by dispersing non-oxidized graphene powder or reduced graphene oxide powder in a fluorine-benzene (Fluoro-benzene) solution.
Reference electrode for ion measurement sensors.
The method of claim 1,
further comprising a substrate;
The fluorine-benzene (Fluoro-benzene) that the non-oxidized graphene or reduced graphene oxide containing the treated fluorine functional group is applied on the substrate in the form of powder,
Reference electrode for ion measurement sensors.
The method of claim 1,
The fluorine-benzene (Fluoro-benzene)-treated graphene containing a fluorine functional group is formed by coating a fluorine-benzene (Fluoro-benzene) solution on a non-oxidized graphene sheet or a reduced graphene oxide sheet,
Reference electrode for ion measurement sensors.
The method of claim 1,
further comprising a substrate;
The fluorine-benzene (Fluoro-benzene) that the non-oxidized graphene or reduced graphene oxide containing the treated fluorine functional group is formed on the substrate in the form of a sheet,
Reference electrode for ion measurement sensors.
The method of claim 1,
The ions of the ion measuring sensor are hydrogen ions, sodium ions, calcium ions, potassium ions, magnesium ions, nitrate ions, sulfate ions, chlorine ions, halogen ions, ammonium ions,
Reference electrode for ion measurement sensors.
The method of claim 1,
The ion measuring sensor is an ion sensing field effect transistor (ISFET) based ion measuring sensor,
Reference electrode for ion measurement sensors.
depositing a gold (Au) electrode on the substrate; and
Applying the graphene containing the fluorine functional group treated with the fluoro-benzene on the substrate or the gold (Au) electrode deposited on the substrate;
In the step of applying the graphene containing the fluorine functional group, the non-oxide graphene or the reduced graphene oxide containing the fluorine functional group treated with the fluorine-benzene is applied on the substrate in powder form,
The fluorine-benzene (Fluoro-benzene)-treated graphene containing a fluorine functional group is formed by dispersing non-oxidized graphene powder or reduced graphene oxide powder in a fluorine-benzene (Fluoro-benzene) solution.
A method for manufacturing a reference electrode for an ion measurement sensor.
forming a graphene sheet on a substrate;
depositing a gold (Au) electrode on a portion of the graphene sheet; and
Preparing a graphene containing a fluorine functional group treated with fluorine-benzene by applying a fluoro-benzene (Fluoro-benzene) solution on the graphene sheet;
The graphene sheet is a non-oxidized graphene sheet or a reduced graphene oxide sheet,
A method for manufacturing a reference electrode for an ion measurement sensor.

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