Electrode, biosensor, and method for manufacturing electrode

Abstract

An electrode 1 is provided with a base material film 2 and a conductive carbon layer 4, in the order toward one side in the thickness direction. The conductive carbon layer 4 has a first functional group and a second functional group on one surface in the thickness direction. The first functional group is composed of an ester group, an ether group, and a secondary or higher amine. The second functional group is composed of a hydroxyl group, a primary amine, and a carbonyl group. The ratio (first functional group / second functional group) of the first functional group to the second functional group on the one surface of the conductive carbon layer 4 in the thickness direction is 4.0 or less as determined using X-ray photoelectron spectroscopy in which the photoelectron take-off angle is 90°. In addition, the ratio (O90 / C90) calculated from the oxygen atom content O90 and the carbon atom content C90 on the one surface of the conductive carbon layer in the thickness direction is 0.13 or more as determined using X-ray photoelectron spectroscopy in which the photoelectron take-off angle is 90°.

Description

Electrode, biosensor, and method for manufacturing electrode

[0001] The present invention relates to an electrode, a biosensor, and a method for manufacturing an electrode, and more particularly to an electrode, a biosensor including the electrode, and a method for manufacturing the electrode.

[0002] Conventionally, carbon electrodes have been used as electrodes for biosensors.

[0003] As such an electrode, for example, an electrode including a substrate and a conductive carbon layer has been proposed (see, for example, Patent Document 1 listed below).

[0004] Japanese Patent Application Laid-Open No. 2021-56205

[0005] Such biosensors are required to have both high sensitivity and high reagent applicability.

[0006] The present invention provides an electrode that combines highly sensitive activity with high reagent applicability, a biosensor including the electrode, and a method for producing the electrode.

[0007] The present invention [1] provides a conductive carbon layer comprising, in this order toward one side in a thickness direction, a base film and a conductive carbon layer, the conductive carbon layer having, on one surface in the thickness direction, a first functional group and a second functional group, the first functional group being an ester group, an ether group, and a secondary or higher amine, and the second functional group being a hydroxyl group, a primary amine, and a carbonyl group, the ratio of the first functional group to the second functional group (first functional group / second functional group) on one surface in the thickness direction of the conductive carbon layer measured using X-ray photoelectron spectroscopy with a photoelectron take-off angle of 90° being 4.0 or less, and the content of oxygen atoms O ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ ) is 0.13 or more.

[0008] The present invention [2] is the electrode according to the above [1], further comprising a metal underlayer between the substrate film and the conductive carbon layer.

[0009] The present invention [3] is a biosensor comprising the electrode according to the above [1] or [2].

[0010] The present invention [4] is a method for producing an electrode according to the above [1] or [2], comprising: a preparation step of preparing a base film; a conductive carbon layer arrangement step of arranging a conductive carbon layer on one side in a thickness direction of the base film to produce a laminate; and a plasma treatment step of performing a plasma treatment on the one side in the thickness direction of the laminate in the presence of nitrogen gas.

[0011] In the electrode of the present invention, the ratio of the first functional groups to the second functional groups (first functional groups / second functional groups) on one surface in the thickness direction of the conductive carbon layer, measured by X-ray photoelectron spectroscopy with a photoelectron take-off angle of 90°, is 4.0 or less. Furthermore, the content of oxygen atoms O ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ ) is 0.13 or more. Therefore, both highly sensitive activity and high reagent applicability can be achieved.

[0012] The biosensor of the present invention includes the electrode of the present invention, and therefore can achieve both highly sensitive activity and high reagent applicability.

[0013] The method for manufacturing an electrode of the present invention includes a plasma treatment step of performing plasma treatment on one surface of a conductive carbon layer in the thickness direction in the presence of nitrogen gas, so that the ratio of first functional groups to second functional groups (first functional groups / second functional groups) on one surface of the conductive carbon layer in the thickness direction is 4.0 or less, and the content of oxygen atoms O ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C９０ ) is 0.13 or more.

[0014] FIG. 1 is a cross-sectional schematic diagram of one embodiment of an electrode of the present invention. FIGS. 2A to 2D show a method for manufacturing the electrode shown in FIG. 1. FIG. 2A shows a preparation step for preparing a substrate film. FIG. 2B shows a metal underlayer disposing step for disposing a metal underlayer on one surface in the thickness direction of the substrate film. FIG. 2C shows a conductive carbon layer disposing step for manufacturing a laminate by disposing a conductive carbon layer on one surface in the thickness direction of the metal underlayer. FIG. 2D shows a plasma treatment step for performing plasma treatment on one surface in the thickness direction of the laminate in the presence of nitrogen gas. This is a schematic diagram of one embodiment of an electrochemical measurement system using the electrode 1 shown in FIG. 1.

[0015] An embodiment of the electrode of the present invention will be described with reference to FIG.

[0016] In Figure 1, the up-down direction of the paper surface is the up-down direction (thickness direction). The upper side of the paper surface is the upper side (one side in the thickness direction). The lower side of the paper surface is the lower side (the other side in the thickness direction). The left-right direction and the depth direction of the paper surface are surface directions perpendicular to the up-down direction. Specifically, they conform to the directional arrows in each figure.

[0017] 1, the electrode 1 has a film shape (including a sheet shape) with a predetermined thickness. The electrode 1 extends in a plane direction perpendicular to the thickness direction. The electrode 1 has a flat upper surface and a flat lower surface.

[0018] The electrode 1 includes, in this order toward one side in the thickness direction, a base film 2, a metal base layer 3, and a conductive carbon layer 4. Specifically, the electrode 1 includes the base film 2, the metal base layer 3 disposed directly on the upper surface (one side in the thickness direction) of the base film 2, and the conductive carbon layer 4 disposed directly on the upper surface (one side in the thickness direction) of the metal base layer 3. The electrode 1 preferably includes the base film 2, the metal base layer 3, and the conductive carbon layer 4.

[0019] From the viewpoint of ease of handling, the thickness of the electrode 1 is, for example, 10 μm to 1000 μm, preferably 25 μm to 500 μm, more preferably 50 μm to 250 μm, even more preferably 100 μm to 225 μm, and particularly preferably 150 μm to 200 μm.

[0020] <Base Film> The base film 2 has a film shape and is the bottom layer of the electrode 1.

[0021] Examples of materials for the base film 2 include resins, ceramics, and metals. From the viewpoint of flexibility, resins are preferred as materials for the base film 2. In other words, the base film 2 is preferably a resin film.

[0022] Examples of resins include polyester resins, (meth)acrylic resins, olefin resins, polycarbonate resins, polyethersulfone resins, polyarylate resins, melamine resins, polyamide resins, polyimide resins, cellulose resins, and polystyrene resins. Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Examples of (meth)acrylic resins include polymethyl methacrylate. Examples of olefin resins include polyethylene, polypropylene, and cycloolefin polymers. Examples of cellulose resins include triacetyl cellulose.

[0023] The resin is preferably a polyester resin, and more preferably polyethylene terephthalate.

[0024] The resins can be used alone or in combination of two or more.

[0025] The thickness of the substrate film 2 is obtained by subtracting the thickness (nm) of the metal underlayer 3 and the thickness (nm) of the conductive carbon layer 4 from the thickness (μm) of the electrode 1 described above, and is, for example, 10 μm to 1000 μm, preferably 25 μm to 500 μm, more preferably 50 μm to 250 μm, even more preferably 100 μm to 225 μm, and particularly preferably 150 μm to 200 μm.

[0026] The thickness of the base film 2 can be measured using a dial gauge (manufactured by PEACOCK, "DG-205").

[0027] <Metallic Underlayer> The metallic underlayer 3 assists the conductivity of the conductive carbon layer 4 .

[0028] The metal underlayer 3 is disposed on the entire lower surface of the conductive carbon layer 4 so as to be in contact with the lower surface of the conductive carbon layer 4. In other words, the metal underlayer 3 is disposed between the base film 2 and the conductive carbon layer 4.

[0029] The material of the metal underlayer 3 is a metal. Examples of metals include titanium, tantalum, chromium, molybdenum, tungsten, and niobium. Niobium is preferably used as the material of the metal underlayer 3 from the viewpoint of improving activity (described later) with respect to the analyte. In other words, the metal underlayer 3 is preferably a niobium layer.

[0030] The material for the metal underlayer 3 can be used alone or in combination of two or more kinds.

[0031] The metal underlayer 3 is formed by sputtering, as will be described in detail later, that is, the metal underlayer 3 is preferably a sputtered layer.

[0032] The thickness of the metal underlayer 3 is, from the viewpoint of productivity by sputtering, for example, 1 nm to 200 nm, preferably 3 nm to 100 nm, and more preferably 4 nm to 80 nm; from the viewpoint of achieving both productivity and conductivity, it is even more preferably 5 nm to 50 nm, particularly preferably 7 nm to 48 nm, or even 9 nm to 45 nm; and from the viewpoint of further improving productivity and conductivity, it is even more preferably 10 nm to 40 nm, even more preferably 11 nm to 39 nm, or even more preferably 13 nm to 30 nm.

[0033] Specifically, from the viewpoint of reducing the surface resistance of the electrode 1, the thickness of the metal underlayer 3 is, for example, 1 nm or more, preferably 3 nm or more, more preferably 4 nm or more, even more preferably 5 nm or more, particularly preferably 7 nm or more, even 9 nm or more, even 10 nm or more, even 11 nm or more, or even 13 nm or more. From the viewpoint of improving adhesion and suppressing the occurrence of cracks, the thickness is, for example, 200 nm or less, preferably 100 nm or less, more preferably 80 nm or less, even more preferably 50 nm or less, particularly preferably 48 nm or less, even 45 nm or less, even 40 nm or less, even 39 nm or less, or even 30 nm or less.

[0034] <Conductive Carbon Layer> The conductive carbon layer 4 has a film shape. The conductive carbon layer 4 is disposed on the entire upper surface of the metal base layer 3 so as to be in contact with the upper surface of the metal base layer 3. The conductive carbon layer 4 is the uppermost layer of the electrode 1.

[0035] The conductive carbon layer 4 is, for example, sp ２ Bonds and sp ３ That is, the conductive carbon layer 4 has, for example, a graphite structure and a diamond structure, which can improve the conductivity of the conductive carbon layer 4 and the sensitivity of the electrode.

[0036] sp ３ Number of bonded atoms and sp ２ sp for the sum of the number of atoms bonded ３ The ratio of the number of bonded atoms (sp ３ / sp ３ +sp２ ) is, for example, 0.10 to 0.90, preferably 0.20 to 0.50, more preferably 0.25 to 0.45 from the viewpoint of productivity, and even more preferably 0.30 to 0.40 from the viewpoint of electrochemical properties.

[0037] The above ratio is determined by measuring one surface of the conductive carbon layer 4 in the thickness direction by X-ray photoelectron spectroscopy. ２ Bond peak intensity and sp ３ It can be calculated based on the peak intensity of the binding.

[0038] The conductive carbon layer 4 is formed by sputtering, as will be described in detail later, that is, the conductive carbon layer 4 is preferably a sputtered layer.

[0039] The thickness of the conductive carbon layer 4 is, from the viewpoint of productivity, for example, 1.0 nm to 20 nm, preferably 2.0 nm to 17 nm, and more preferably 2.5 nm to 15 nm; from the viewpoint of achieving both productivity and conductivity, it is still more preferably 3.0 nm to 13 nm, particularly preferably 3.5 nm to 11 nm, furthermore preferably 4.0 nm to 9.0 nm, or even more preferably 4.5 nm to 7.0 nm.

[0040] Specifically, from the viewpoint of improving the performance of the electrode 1, the thickness of the conductive carbon layer 4 is, for example, 1.0 nm or more, preferably 2.0 nm or more, more preferably 2.5 nm or more, even more preferably 3.0 nm or more, particularly preferably 3.5 nm or more, further 4.0 nm or more, and even 4.5 nm or more; and from the viewpoint of ensuring adhesion to the metal underlayer 3, the thickness is, for example, 20 nm or less, preferably 17 nm or less, more preferably 15 nm or less, even more preferably 13 nm or less, particularly preferably 11 nm or less, further 9.0 nm or less, and even 7.0 nm or less.

[0041] The conductive carbon layer 4 has a first functional group and a second functional group on one surface in the thickness direction.

[0042] As will be described in detail later, the first functional group and the second functional group are provided to one surface in the thickness direction of the conductive carbon layer 4 by plasma treatment.

[0043] The first functional group, which will be described in detail later, is a functional group that exchanges electrons with the analyte during measurement and contributes to the sensitivity of the electrode 1. The contribution of the first functional group to the sensitivity of the electrode 1 is lower than that of the second functional group. The first functional group also affects the applicability of the reagent on the surface of the electrode 1 to the measurement target. Specifically, the first functional group is an ester group, an ether group, and a secondary or higher amine. In other words, the first functional group is one of the three functional groups: an ester group, an ether group, and a secondary or higher amine.

[0044] The second functional group, which will be described in detail later, is a functional group that exchanges electrons with the analyte during measurement and contributes to the sensitivity of the electrode 1. The contribution of the second functional group to the sensitivity of the electrode 1 is greater than that of the first functional group. The second functional group also affects the applicability of the reagent on the surface of the electrode 1 to the object to be measured. Specifically, the second functional group is one of three functional groups: a hydroxyl group, a primary amine, and a carbonyl group.

[0045] In the electrode 1, the ratio of the first functional groups to the second functional groups (first functional groups / second functional groups) on one surface in the thickness direction of the conductive carbon layer 4, measured by X-ray photoelectron spectroscopy with a photoelectron take-off angle of 90°, is 4.0 or less, preferably less than 3.5 or less, more preferably 3.0 or less, even more preferably 2.5 or less, particularly preferably 2.0 or less, and particularly preferably 1.5 or less, and is, for example, 0.1 or more.

[0046] If the ratio is equal to or less than the upper limit, the sensitivity of the electrode is improved, and the applicability of the reagent is improved.

[0047] On the other hand, if the ratio exceeds the upper limit, the sensitivity of the electrode decreases, and the applicability of the reagent decreases.

[0048] The above ratio is adjusted to be equal to or less than the above upper limit by adjusting the conveying speed in the manufacturing method of the electrode 1 described later and the plasma treatment conditions (e.g., nitrogen concentration, pressure, discharge power, and plasma time) in the plasma treatment step described later.

[0049] The water contact angle of one surface in the thickness direction of the conductive carbon layer 4 is not limited, but is, for example, 10 degrees or more and 90 degrees or less.

[0050] The water contact angle of one surface in the thickness direction of the conductive carbon layer 4 is preferably 10 degrees or more, more preferably 15 degrees or more, even more preferably 20 degrees or more, particularly preferably 25 degrees or more, and most preferably 30 degrees or more. When the water contact angle of one surface in the thickness direction of the conductive carbon layer 4 is equal to or greater than the above-mentioned lower limit, reagent applicability can be improved.

[0051] On the other hand, if the water contact angle of one surface in the thickness direction of the conductive carbon layer 4 is less than the above-mentioned lower limit, the reagent droplets will wet and spread too much, resulting in a significant decrease in reagent applicability. Here, reagent applicability refers to the property of maintaining an appropriate amount of reagent when applied to the electrode and preventing the reagent from shifting during transportation or movement. Such properties are achieved by maintaining the surface of the electrode 1 with sufficient reagent applicability.

[0052] The water contact angle of one surface in the thickness direction of the conductive carbon layer 4 is preferably 55 degrees or less, more preferably 50 degrees or less, even more preferably 48 degrees or less, and particularly preferably 46 degrees or less. When the water contact angle of one surface in the thickness direction of the conductive carbon layer 4 is equal to or less than the above upper limit, reagent applicability can be improved.

[0053] On the other hand, if the water contact angle on one surface in the thickness direction of the conductive carbon layer 4 exceeds the upper limit mentioned above, the electrode will repel the reagent when the reagent is applied, causing inconvenience in production.

[0054] The conditions for measuring the water contact angle will be described in detail in the examples below.

[0055] Although the method for adjusting the water contact angle of one surface in the thickness direction of the conductive carbon layer 4 to fall within the above-mentioned range is not limited, in the present invention, the water contact angle is adjusted to an appropriate numerical range mainly by adjusting the ratio of the first functional groups to the second functional groups (first functional groups / second functional groups) described above. That is, the water contact angle is adjusted by adjusting the conveying speed in the manufacturing method of the electrode 1 and the plasma treatment conditions (e.g., nitrogen concentration, pressure, discharge power, and plasma time) in the plasma treatment step described below.

[0056] The content of oxygen atoms O on one surface in the thickness direction of the conductive carbon layer measured using X-ray photoelectron spectroscopy with a photoelectron take-off angle of 90° ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ ) is, for example, 0.03 or more.

[0057] The oxygen atom content O on one surface of the conductive carbon layer 4 in the thickness direction ９０ and the carbon atom content C ９０ The ratio (O ９０ / C ９０ ) is 0.13 or more, preferably 0.14 or more, more preferably 0.15 or more, even more preferably 0.16 or more, and particularly preferably 0.17 or more. ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ ) is equal to or greater than the above-mentioned lower limit, the sensitivity of the electrode 1 can be further improved.

[0058] The oxygen atom content O on one surface of the conductive carbon layer 4 in the thickness direction ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ ) is, for example, 0.3 or less, preferably 0.26 or less, more preferably 0.24 or less, particularly preferably 0.22 or less, and most preferably 0.21 or less. ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ ) is equal to or less than the above upper limit, a structure suitable for the conductive carbon layer 4 can be maintained.

[0059] The oxygen atom content O on one surface of the conductive carbon layer 4 in the thickness direction ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０) is measured by X-ray photoelectron spectroscopy with a photoelectron take-off angle of 90°. The conditions for X-ray photoelectron spectroscopy will be described in the Examples below.

[0060] The content O of oxygen atoms on one surface in the thickness direction of the conductive carbon layer 4 is measured using X-ray photoelectron spectroscopy with a photoelectron take-off angle of 90°. ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ The method for adjusting the oxygen atom content O ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ ) within the above range, for example, a method of subjecting one surface in the thickness direction of the conductive carbon layer 4 to oxidation treatment, etching, surface modification, and cleaning, and in this embodiment, a method of subjecting one surface in the thickness direction of the conductive carbon layer 4 to plasma treatment is preferably used. The method of subjecting one surface in the thickness direction to plasma treatment will be described later.

[0061] <Electrode Manufacturing Method> A method for manufacturing the electrode 1 will be described with reference to FIGS. 2A to 2D.

[0062] The method for producing the electrode 1 includes a preparation step of preparing a substrate film 2, a metal underlayer disposing step of disposing a metal underlayer 3 on one thickness-wise surface of the substrate film 2, a conductive carbon layer disposing step of disposing a conductive carbon layer 4 on one thickness-wise surface of the metal underlayer 3 to produce a laminate 10, and a plasma treatment step of performing a plasma treatment on one thickness-wise surface of the laminate 10 in the presence of nitrogen gas. This method is preferably carried out using a roll-to-roll system. In such a case, the conveying speed is, for example, 0.1 m / min to 20.0 m / min.

[0063] [Preparation Step] In the preparation step, as shown in FIG. 2A, a base film 2 is prepared.

[0064] [Metallic Underlayer Arranging Step] In the metallic underlayer arranging step, as shown in FIG. 2B , a metallic underlayer 3 is arranged on one surface of the substrate film 2 in the thickness direction.

[0065] The metal underlayer 3 can be formed by, for example, a dry method or a wet method. The metal underlayer 3 is preferably formed by a dry method.

[0066] Examples of dry methods include PVD (physical vapor deposition) and CVD (chemical vapor deposition). Preferably, the dry method is PVD. Examples of PVD include sputtering, vacuum deposition, laser deposition, and ion plating. Preferably, the PVD is sputtering.

[0067] In the sputtering method, a target (material for the metal underlayer 3) and the substrate film 2 are placed facing each other in a vacuum chamber. Next, sputtering gas is supplied and a voltage is applied from a power source, which accelerates gas ions and irradiates them onto the target, thereby ejecting the target material from the target surface. The target material is then deposited on the surface (one surface in the thickness direction) of the substrate film 2, forming the metal underlayer 3.

[0068] The sputtering gas may be, for example, an inert gas (eg, argon gas).

[0069] The film formation pressure during sputtering is, for example, 0.05 Pa to 1.0 Pa.

[0070] The power source may be, for example, a DC power source, an AC power source, an MF power source, or an RF power source, or may be a combination of these.

[0071] The discharge power is, for example, 1.0 W / cm ２ ~8.0 W / cm ２ , preferably 1.5 W / cm ２ ~4.0 W / cm ２ is.

[0072] The temperature of the substrate film 2 (film formation temperature) is, for example, -10°C to 200°C, or preferably 20°C to 100°C.

[0073] As a result, the metal underlayer 3 is disposed on one surface of the substrate film 2 in the thickness direction.

[0074] 2C , in the conductive carbon layer arranging step, a conductive carbon layer 4 is arranged on one surface in the thickness direction of the metal base layer 3 to produce the laminate 10. In other words, in the conductive carbon layer arranging step, a conductive carbon layer 4 is arranged on one side in the thickness direction of the base film 2 to produce the laminate 10.

[0075] The method for forming the conductive carbon layer 4 is the same as the method for forming the metal underlayer 3. A preferred method for forming the conductive carbon layer 4 is sputtering.

[0076] In the sputtering method, sintered carbon is selected as the target, and the sputtering conditions (sputtering gas, deposition pressure, power supply, discharge power, and deposition temperature) in the sputtering method are the same as those in the metal underlayer disposing step described above.

[0077] In this way, the conductive carbon layer 4 is disposed on one surface in the thickness direction of the metal base layer 3, and the laminate 10 is manufactured.

[0078] 2D , in the plasma treatment step, plasma treatment is performed on one surface in the thickness direction of the laminate 10 (specifically, one surface in the thickness direction of the conductive carbon layer 4) in the presence of nitrogen gas. As described in this embodiment, the plasma treatment is preferably capacitively coupled plasma treatment under low pressure or in vacuum, and more preferably capacitively coupled plasma treatment under vacuum.

[0079] Specifically, the laminate 10 is transferred into a vacuum chamber, and nitrogen is supplied into the vacuum chamber.

[0080] The nitrogen concentration in the gas supplied into the vacuum chamber is, for example, 50% by volume to 100% by volume, preferably 70% by volume to 100% by volume, and more preferably 90% by volume to 100% by volume.

[0081] A gas other than nitrogen (specifically, an inert gas) may be introduced into the vacuum chamber. Examples of the inert gas include argon. The proportion of the gas other than nitrogen in the vacuum chamber is the balance of the nitrogen in the vacuum chamber, and is, for example, 10% by volume or less.

[0082] The actual nitrogen gas concentration in the vacuum chamber is affected not only by the nitrogen concentration in the supplied gas and the concentration of gases other than nitrogen, but also by remaining components in the vacuum chamber and components attached to the laminate. Examples of remaining components in the vacuum chamber and components attached to the laminate include water, oxygen, nitrogen, and carbon dioxide. When the nitrogen concentration in the gas supplied to the vacuum chamber is 100% by volume, the actual nitrogen gas concentration in the vacuum chamber is approximately 98% by volume. The actual nitrogen gas concentration in the vacuum chamber is, for example, 50% to 98% by volume, preferably 70% to 98% by volume, and more preferably 90% to 98% by volume.

[0083] The pressure inside the vacuum chamber is, for example, 0.1 Pa to 20 Pa. The pressure can be adjusted by the amount of nitrogen gas supplied to the vacuum chamber.

[0084] Next, one surface of the laminate 10 in the thickness direction is subjected to plasma treatment.

[0085] Examples of plasma generation methods include AC plasma generation methods and DC plasma generation methods. Examples of AC plasma generation methods include capacitively coupled plasma (CCP), inductively coupled plasma (ICP), and surface acoustic wave plasma (SWP). Examples of DC plasma generation methods include magnetron DC discharge. Preferably, AC plasma generation methods, more specifically capacitively coupled plasma, are used.

[0086] The discharge power is, for example, 0.05 W / cm ２ ~12.0 W / cm ２ , preferably 0.1 W / cm ２ ~10.0 W / cm ２ , more preferably 0.2 W / cm２ ~5.0 W / cm ２ is.

[0087] The plasma treatment time is, for example, 0.3 to 60 seconds, preferably 0.5 to 30 seconds.

[0088] Specifically, the plasma treatment time is, for example, 0.3 seconds or more, preferably 0.5 seconds or more, from the viewpoint of reliably imparting the first functional group and the second functional group to one surface of the conductive carbon layer 4 in the thickness direction, and is, for example, 60 seconds or less, preferably 30 seconds or less, from the viewpoint of preventing a change in the film quality of the conductive carbon layer 4 and a decrease in the activity (described later) of the conductive carbon layer 4 against the test substance.

[0089] In this way, plasma treatment is performed on one surface in the thickness direction of the laminate 10, and the electrode 1 is manufactured.

[0090] In the electrode 1, the ratio of the first functional groups to the second functional groups (first functional groups / second functional groups) on one surface in the thickness direction of the conductive carbon layer 4, as measured by X-ray photoelectron spectroscopy with a photoelectron take-off angle of 90°, is 4.0 or less. Furthermore, the content of oxygen atoms O ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ ) is 0.13 or more. Therefore, an electrode that achieves both highly sensitive activity and high reagent applicability can be obtained.

[0091] Therefore, the electrode 1 can be suitably used particularly as an electrode in a biosensor, that is, the electrode 1 is preferably a biosensor electrode.

[0092] 2. Biosensor In the following description, a blood glucose sensor will be described in detail as an example of a biosensor. In the blood glucose sensor, the test substance is, for example, a ferricyanide compound or a ferrocyanide compound.

[0093] The blood glucose sensor includes an electrode 1 and a reagent layer arranged in this order toward one side in the thickness direction.

[0094] The reagent layer contains an enzyme and a ferricyanide or ferrocyanide compound.

[0095] An example of the enzyme is glucose oxidase.

[0096] Examples of the ferricyanide compound include potassium ferricyanide and sodium ferricyanide. The ferricyanide compound is preferably potassium ferricyanide.

[0097] Examples of ferrocyanide compounds include potassium ferrocyanide and sodium ferrocyanide.

[0098] A method for detecting glucose in blood using a blood glucose sensor will be described in detail below, with the reagent layer containing an enzyme and potassium ferricyanide.

[0099] In this method, blood is first added to one side of the reagent layer in the thickness direction. At this time, glucose in the blood is oxidized by the enzyme in the reagent layer. At this time, the enzyme reduces potassium ferricyanide to potassium ferrocyanide.

[0100] A voltage is then applied to the blood glucose sensor, which causes the potassium ferrocyanide to oxidize and become potassium ferricyanide.

[0101] By measuring the value of the current that flows during the oxidation reaction, glucose in the blood can be indirectly detected.

[0102] The blood glucose sensor includes the electrode 1. Therefore, it is possible to achieve both high sensitivity and high reagent applicability.

[0103] 3. Effects In the electrode 1, the ratio of the first functional groups to the second functional groups (first functional groups / second functional groups) on one surface in the thickness direction of the conductive carbon layer, measured using X-ray photoelectron spectroscopy with a photoelectron take-off angle of 90°, is 4.0 or less. Furthermore, the content of oxygen atoms O ９０and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ ) is 0.13 or more. Therefore, an electrode that achieves both highly sensitive activity and high reagent applicability can be obtained.

[0104] Specifically, blood glucose sensors are known as biosensors. To accurately detect blood glucose levels from minute blood samples, electrodes that combine high sensitivity and high reagent applicability are required.

[0105] As described above, the blood glucose sensor includes an electrode 1 and a reagent layer, arranged in this order toward one side in the thickness direction. The reagent layer contains an enzyme and a ferricyanide compound or a ferrocyanide compound. Regarding a method for detecting glucose in blood using the blood glucose sensor, if the ferricyanide compound is potassium ferricyanide, the glucose in the blood is first oxidized by the enzyme in the reagent layer, and the enzyme also reduces the potassium ferricyanide to potassium ferrocyanide. Next, by applying a voltage to the blood glucose sensor, the potassium ferrocyanide is oxidized to potassium ferricyanide. Then, by measuring the current flowing during the oxidation reaction, glucose in the blood is indirectly detected.

[0106] The value of the current that flows in the above-mentioned oxidation reaction varies depending on the sensitivity of the electrode 1, so an electrode with high sensitivity and activity is required for efficient measurement. Furthermore, for efficient measurement of a small amount of blood sample, sufficient reagent applicability is required to prevent the blood sample from wetting and spreading.

[0107] In the electrode 1, the ratio of the first functional groups to the second functional groups (first functional groups / second functional groups) on one surface in the thickness direction of the conductive carbon layer, measured using X-ray photoelectron spectroscopy with a photoelectron take-off angle of 90°, is 4.0 or less. Furthermore, the content of oxygen atoms O ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ ) is 0.13 or more. Therefore, an electrode that achieves both highly sensitive activity and high reagent applicability can be obtained.

[0108] Specifically, the above-described plasma treatment can provide the first functional group and the second functional group to one surface in the thickness direction of the conductive carbon layer 4. At the same time, the content of oxygen atoms O ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ ) can be 0.13 or more. Plasma treatment using nitrogen gas imparts functional groups containing not only nitrogen atoms but also oxygen atoms. This is because oxygen atoms contained in the remaining components in the vacuum chamber and the attached components of the laminate are used in the plasma treatment. The first functional group and the second functional group have different energy levels, and therefore differ in the likelihood of electron transfer with the test substance. Specifically, the first functional group is ranked as more likely to transfer electrons with the test substance, while the second functional group is ranked as less likely to transfer electrons with the test substance.

[0109] Specifically, the primary functional groups, ester groups, ether groups, and secondary or higher amine groups, are less likely to exchange electrons with the analyte than the secondary functional groups, hydroxyl groups, primary amines, and carbonyl groups. As a result, when the proportion of the primary functional groups in the conductive carbon layer 4 increases, the glucose response current decreases, and the sensitivity of the electrode 1 decreases.

[0110] On the other hand, the secondary functional groups, hydroxyl groups, primary amines, and carbonyl groups, are more likely to exchange electrons with the test substance than the primary functional groups, ester groups, ether groups, and secondary or higher amines. As a result, when the proportion of the secondary functional groups in the conductive carbon layer 4 increases, the glucose response current increases, and the sensitivity of the electrode improves. The oxygen atom content O ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ ) is 0.13 or more, the above effects are further improved significantly.

[0111] Furthermore, the first functional groups, ester groups, ether groups, and secondary or higher amines, are less hydrophilic than the second functional groups, hydroxyl groups, primary amines, and carbonyl groups. On the other hand, the second functional groups, hydroxyl groups, primary amines, and carbonyl groups, are more hydrophilic than the first functional groups, ester groups, ether groups, and secondary or higher amines. Therefore, by adjusting the ratio of the first functional groups to the second functional groups (first functional groups / second functional groups), the water contact angle can be adjusted, and the reagent applicability can be controlled.

[0112] In the electrode 1 of this embodiment, the ratio of the first functional groups to the second functional groups (first functional groups / second functional groups) on one surface in the thickness direction of the conductive carbon layer, measured using X-ray photoelectron spectroscopy with a photoelectron take-off angle of 90°, is 4.0 or less. Furthermore, the content of oxygen atoms O ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ ) is 0.13 or more. This makes it possible to achieve both high sensitivity activity and high reagent applicability.

[0113] The blood glucose sensor includes the electrode 1. Therefore, it is possible to achieve both high sensitivity and high reagent applicability.

[0114] <Modifications> In the modification examples, the same components and steps as those in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof will be omitted. Furthermore, the modification examples can achieve the same effects as those in the first embodiment unless otherwise specified. Furthermore, the first embodiment and the modification examples can be combined as appropriate.

[0115] In the above description, the electrode 1 includes the substrate film 2, the metal underlayer 3, and the conductive carbon layer 4, in that order toward one side in the thickness direction, but the electrode 1 does not necessarily have to include the metal underlayer 3. In such a case, the electrode 1 includes the substrate film 2 and the conductive carbon layer 4, in that order toward one side in the thickness direction. Preferably, the electrode 1 includes the metal underlayer 3 from the viewpoint of improving activity toward the analyte.

[0116] The electrode 1 may also include layers (e.g., a hard coat layer, a gas barrier layer) other than the base film 2, the metal underlayer 3, and the conductive carbon layer 4. Specifically, the electrode 1 may include other layers on the other surface of the base film 2 in the thickness direction, between the base film 2 and the metal underlayer 3, between the metal underlayer 3 and the conductive carbon layer 4, and on one surface of the conductive carbon layer 4 in the thickness direction.

[0117] The hard coat layer is an abrasion protection layer that makes it difficult for scratches to occur on the electrode 1. Specifically, the electrode 1 preferably has a hard coat layer on one surface and / or the other surface of the substrate film 2 in the thickness direction.

[0118] Furthermore, when the electrode 1 includes other layers, the thickness of the substrate film 2 is the thickness (μm) of the electrode 1 minus the thickness (nm) of the metal underlayer 3, the thickness (nm) of the conductive carbon layer 4, and the thicknesses (nm) of the other layers.

[0119] In the above explanation, electrode 1 is described as an electrode of a biosensor, but it is not limited to this and can also be used as an electrode for electrochemical measurements in which a test substance is the measurement target, specifically as a working electrode for performing cyclic voltammetry (CV).

[0120] The present invention will be described in more detail below with reference to examples and comparative examples. It should be noted that the present invention is in no way limited to these examples and comparative examples. The specific numerical values ​​of the blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be replaced with the upper limit values ​​(numeric values ​​defined as "equal to or less than") or lower limit values ​​(numeric values ​​defined as "equal to or more than" or "exceeding") of the corresponding blending ratios (content ratios), physical property values, parameters, etc. described in the "Modes for Carrying Out the Invention" above.

[0121] <Electrode Production> Example 1 and Comparative Examples 1 and 2 were produced according to the following procedure. The plasma treatment conditions used in the production are shown in Table 1. Example 1 [Preparation Step] A polyethylene terephthalate film (thickness: 188 μm) was prepared as the substrate film. The following steps were carried out using a roll-to-roll method. The conveying speed was 0.5 m / min.

[0122] [Metal Underlayer Forming Step] A niobium layer (thickness: 32 nm) was formed on one surface of the substrate film in the thickness direction by magnetron sputtering. The magnetron sputtering conditions were as follows: {Conditions} Target: Niobium Target power (discharge power): 1.9 W / cm ２ Sputtering gas: argon gas Film formation pressure: 0.2 Pa Film formation temperature: 40°C

[0123] [Conductive Carbon Layer Forming Step] A conductive carbon layer (thickness: 10 nm) was formed on one surface of the niobium layer in the thickness direction by magnetron sputtering. The magnetron sputtering conditions were as follows. A laminate was thus produced. {Conditions} Target: Sintered carbon Target power: 3.3 W / cm ２ Sputtering gas: argon gas Film formation pressure: 0.2 Pa Film formation temperature: 40°C

[0124] [Plasma Treatment Step] In the presence of nitrogen gas, plasma treatment was performed on one surface in the thickness direction of the laminate (specifically, one surface in the thickness direction of the conductive carbon layer) under the following conditions. Thus, an electrode was manufactured. {Conditions} Type of plasma: vacuum plasma Plasma generation method: capacitively coupled plasma discharge Nitrogen concentration in vacuum chamber: 98% by volume Gas: nitrogen Pressure: 1.0 Pa Discharge power: 0.3 W / cm ２ Plasma time: 24 seconds

[0125] Example 2 An electrode was manufactured based on the same procedure as in Example 1. However, in the plasma treatment step, the plasma treatment was performed under the following conditions: {Conditions} Type of plasma: low-pressure plasma Plasma generation method: capacitively coupled plasma discharge Nitrogen concentration in vacuum chamber: 98% by volume Gas: nitrogen Pressure: 10 Pa Discharge power: 2.7 W / cm ２ Plasma time: 24 seconds

[0126] Comparative Example 1 An electrode was produced according to the same procedure as in Example 1, except that the plasma treatment step was not carried out.

[0127] Comparative Example 2 An electrode was manufactured based on the same procedure as in Example 1. However, in the plasma treatment step, oxygen gas was used instead of nitrogen gas. The oxygen concentration in the vacuum chamber was 98% by volume. The pressure in the plasma treatment step was 0.5 Pa, and the discharge power was 2.6 W / cm. ２ It was.

[0128]

[0129] <Evaluation> [Thickness] The thickness of the metal underlayer and the conductive carbon layer in the electrodes of each Example and Comparative Example were measured by preparing cross-sectional samples for TEM by FIB microsampling and observing the cross-sections using a field emission transmission electron microscope (FE-TEM, manufactured by JOEL, "JEM-2800"). The results are shown in Table 1.

[0130] [Measurement of the Ratio of Primary Functional Groups / Second Functional Groups] The primary functional groups (ester groups, ether groups, and secondary or higher amines) and secondary functional groups (hydroxyl groups, primary amines, and carbonyl groups) refer to the concentration of each functional group derived from the carbon layer, and are calculated as the ratio of the amount (number of moles) of each functional group to the total amount (number of moles) of carbon in the carbon layer. The concentration of each functional group can be determined using X-ray photoelectron spectroscopy (ESCA) using the gas-phase chemical modification method exemplified in Journal of Polymer Science Vol. 26 559-572 (1988) and Journal of the Adhesion Society of Japan Vol. 27 No. 4 (1991). Specifically, the value is measured as follows.

[0131] The electrodes of each example and each comparative example were cut into 1 cm x 1 cm pieces to prepare measurement samples. Next, X-ray photoelectron spectroscopy was performed on the measurement samples. Specifically, narrow scan spectra of carbon, nitrogen, oxygen, and fluorine were obtained on one side of the measurement sample in the thickness direction (the surface of the conductive carbon layer), and the element ratios were calculated from the ratios of the areas of the respective peaks. Furthermore, in the C1s narrow scan spectrum, sp ２ Peaks attributable to bonds (C=C), sp ３ Peaks attributable to bonds (C-C), peaks attributable to COO and -N(H)COO, peaks attributable to C-O and C-N, and peaks attributable to C=O and >NC(=O) were confirmed. {Conditions} X-ray photoelectron spectrometer: KRATOS ULTRA2 manufactured by Shimadzu Corporation X-ray source: Monochrome Al Kα X Ray setting: 700 μm x 300 μm [5 mA, 75 W, Resolution 20] Photoelectron take-off angle: 90 degrees to the sample surface Charge neutralization conditions: Charge neutralization mechanism used

[0132] In the analysis, ESCApe was used as fitting software.

[0133] Also, sp ２ Peaks attributable to bonds (C=C), sp ３The tops of the peaks attributable to bonds (C-C), COO and -N(H)COO, CO and C-N, and C=O and >NC(=O) were assigned as follows: ２ Peak attributable to bond (C═C): ​​284.0 eV to 284.5 eV sp ３ Peak attributable to a bond (C-C): 285.0 eV Peak attributable to C-O and C-N: 286.0 eV to 287.0 eV Peak attributable to C=O and >NC(=O): 287.3 eV to 288.2 eV Peak attributable to COO and -N(H)COO: 288.3 eV to 289.2 eV

[0134] The half-width is sp ２ The other peaks were set to about 1.1 to 1.4 times the original value. Fitting was performed within the above range so that the difference between the actual measurement and the fitting was minimized.

[0135] (Method for calculating carbonyl group concentration) The carbon atom ratio [C 未修飾 ] and the bond ratio of C=O and >NC(=O) [C=O 結合比率 ] and the carbonyl group concentration [C Ｃ=Ｏ ] was calculated based on the following formula (1): Ｃ＝Ｏ ]=[C=O 結合比率 ]×[C 未修飾 ] (1)

[0136] (Method for calculating carboxyl group concentration) Narrow scan spectra were obtained by ESCA for a sample that had been subjected to gas-phase chemical modification with a labeling reagent (trifluoroethanol) and an unmodified sample. The concentration [F ＣＯＯＨ（修飾） ], [F ＣＯＯＨ（未修飾） The carboxyl group concentration on the sample surface [C ＣＯＯＨ ] was calculated based on the following formula (2): ＣＯＯＨ ] = ([F ＣＯＯＨ（修飾） ]-[F ＣＯＯＨ（未修飾） ]) ÷ 3 (2)

[0137] (Method for calculating the ester group concentration) The carbon atom ratio [C 未修飾 ], the COO bond ratio obtained from waveform separation of narrow scan spectra [COO 結合比率 ] to determine the ester group concentration [C ＣＯＯＣ ] was calculated based on the following formula (3): ＣＯＯＣ ] = [COO 結合比率 ]×[C 未修飾 ]-[C ＣＯＯＨ ] (3)

[0138] (Method for calculating hydroxyl group concentration) Narrow scan spectra of ESCA were obtained for a sample that had been subjected to gas-phase chemical modification with a labeling reagent (trifluoroacetic anhydride) and an unmodified sample. The concentration [F Ｃ－ＯＨ（修飾） ], [F Ｃ－ＯＨ（未修飾） The hydroxyl group concentration on the sample surface [C Ｃ－ＯＨ ] was calculated based on the following formula (4): Ｃ－ＯＨ ] = ([F Ｃ－ＯＨ（修飾） ]-[F Ｃ－ＯＨ（未修飾） ]) ÷ 3 (4)

[0139] (Method for calculating primary amine concentration) Narrow scan spectra of ESCA were obtained for a sample that had been subjected to gas-phase chemical modification with a labeling reagent (pentafluorobenzaldehyde) and an unmodified sample. The concentration [F ＮＨ２（修飾） ], [F ＮＨ２（未修飾） The primary amine concentration on the sample surface [C ＮＨ２ ] was calculated based on the following formula (5): ＮＨ２ ] = ([F ＮＨ２（修飾） ]-[F ＮＨ２（未修飾） ]) ÷ 5 (5)

[0140] (Method for calculating the concentration of ether groups and secondary or higher amines) The carbon atom ratio [C 未修飾], and the bond ratio of C—O to C—N [C—O and C—N bond ratio] obtained from waveform separation of the narrow scan spectrum was used to determine the concentration of ether groups and secondary or higher amines on the sample surface [C ＣＯＣ，ＣＮＣ ] was calculated based on the following formula (6): ＣＯＣ，ＣＮＣ ] = [C-O and C-N bond ratio] x [C 未修飾 ]-[C Ｃ－ＯＨ ]-[C ＮＨ２ ] (6)

[0141] From the above, the primary functional groups (ester groups, ether groups, and secondary or higher amines) and secondary functional groups (hydroxyl groups, primary amines, and carbonyl groups) were quantified, and the "primary functional groups / secondary functional groups" ratio was calculated. The results are shown in Table 1.

[0142] [Measurement of Water Contact Angle] For each electrode of each Example and Comparative Example, the water contact angle of one surface in the thickness direction of the electrode was measured immediately after the plasma treatment (specifically, within 12 hours after the plasma treatment). The measurement results are shown in Table 2.

[0143] Specifically, the water contact angle was measured by the sessile drop method using a water contact angle measuring device (product name "Dmo-501", manufactured by Kyowa Interface Science Co., Ltd.) in an atmosphere at a temperature of 23°C and a humidity of 30% RH. First, a water droplet of about 2.0 μL was dropped onto the center of one surface of the electrode in the thickness direction. Then, one second after the drop, the angle formed by the tangent line of the adherend surface (one surface of the electrode in the thickness direction) and the end of the dropped water droplet was measured and recorded as the "water contact angle (°)." A smaller "water contact angle (°)" indicates better hydrophilicity.

[0144] A: The water contact angle was 30 degrees or more and less than 50 degrees. The reagent applicability was remarkably high. B: The water contact angle was 20 degrees or more and less than 30 degrees. The reagent applicability was sufficiently high. C: The water contact angle was 10 degrees or more and less than 20 degrees. The reagent applicability was high. D: The water contact angle was less than 10 degrees or 50 degrees or more. The reagent applicability was low.

[0145] [Measurement of glucose response current] In order to measure the sensitivity of the prepared electrode, that is, the glucose response current, an enzyme electrode was prepared and the glucose response current was measured.

[0146] 1. Preparation of Enzyme Electrode First, an enzyme solution was prepared by mixing 0.8 mg of glucose dehydrogenase, 1.5 μL of a 4 wt % aqueous solution of bovine serum albumin, 1.2 μL of a 1% aqueous solution of glutaraldehyde, and 0.3 μL of a 0.05 M potassium phosphate buffer solution (pH 6.5).

[0147] Next, an insulating tape with a 2 mm diameter hole was attached to one surface in the thickness direction of the electrode 1 to prepare an electrode 1 with a known exposed area on one surface in the thickness direction. Next, the enzyme solution was dropped onto the electrode, and the electrode was stored in a refrigerator at 3°C ​​overnight or longer. In this way, an enzyme electrode (enzyme-modified carbon electrode) comprising an electrode and an enzyme layer was prepared.

[0148] 2. Measurement of glucose response current A 100 mM potassium ferrocyanide solution, an electrolyte prepared by adding KCl to 0.05 M phosphate buffer (pH 6.5) to make the concentration 1 M, and a 1000 mg / dL glucose solution were mixed to prepare a glucose solution (subject solution 25) having a concentration of 600 mg / dL.

[0149] Next, the prepared enzyme electrode (enzyme-modified carbon electrode) was used as a working electrode 21, and as shown in FIG. 4, the working electrode 21 was connected to a potentiostat 24 (pocketSTAT, manufactured by IVIUM Technologies) together with a reference electrode 22 (Ag / AgCl) and a counter electrode 23 (Pt), to prepare an electrochemical measurement system 20 including these.

[0150] Next, 1 mL of glucose solution was spread on the working electrode 21 for 1 minute. Thereafter, the working electrode 21 of these electrochemical measurement systems 20 was swept in the positive direction within a potential sweep range of -0.2 to 0.8 V at a scan rate of 0.1 V / sec (specifically, the potential was changed in the order of -0.2 V, 0.8 V, and -0.2 V). From the results of the CV measurement, the current value at 600 mg / dL at a potential of 0.3 V when sweeping in the positive direction from -0.2 V to 0.8 V was determined as the glucose-responsive current. The glucose responsiveness was then evaluated based on the following evaluation criteria. The measurement results are shown in Table 2.

[0151] A: The response current was 15 μA or more. The sensitivity to glucose was remarkably excellent. B: The response current was 10 μA or more and less than 15 μA. The sensitivity to glucose was excellent. C: The response current was 5 μA or more and less than 10 μA. The sensitivity to glucose was somewhat excellent. D: The response current was less than 5 μA. The sensitivity to glucose was insufficient.

[0152] [Oxygen atom content O on one surface in the thickness direction of the conductive carbon layer ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ Measurement of] The electrodes of each Example and Comparative Example (within 12 hours after the plasma treatment) were cut into 1 cm x 1 cm pieces to prepare measurement samples. Next, X-ray photoelectron spectroscopy was performed on the measurement samples. Specifically, a wide scan spectrum and a narrow scan spectrum were obtained for one surface in the thickness direction of the measurement sample (the surface of the conductive carbon layer), and the element ratio was calculated from the ratio of the areas of the respective peaks. Other measurement conditions are as follows. The measurement was performed at a photoelectron take-off angle of 90°. As a result, it was possible to obtain "O ９０ " and "C ９０ " was calculated, and the oxygen atom content O ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ The results are shown in Table 2. {Conditions} X-ray photoelectron spectrometer: KRATOS ULTRA2 manufactured by Shimadzu Corporation X-ray source: Monochrome Al Kα X-ray setting: 700 μm × 300 μm [5 mA, 75 W, Resolution 20] Photoelectron take-off angle: 90 degrees to the sample surface Charge neutralization conditions: Charge neutralization mechanism used

[0153]

[0154] The above invention is provided as an exemplary embodiment of the present invention, but it is merely an example and should not be interpreted as being limiting. Modifications of the present invention that are obvious to those skilled in the art are included in the scope of the following claims.

[0155] The electrodes are used in electrochemical measurements.

[0156] REFERENCE SIGNS LIST 1 Electrode 2 Substrate film layer 3 Metal underlayer 4 Conductive carbon layer 10 Laminate 20 Electrochemical measurement system 21 Working electrode

Claims

1. A conductive carbon layer comprising a base film and a conductive carbon layer in this order toward one side in a thickness direction, wherein the conductive carbon layer has a first functional group and a second functional group on one surface in the thickness direction, wherein the first functional groups are ester groups, ether groups, and secondary or higher amines, and the second functional groups are hydroxyl groups, primary amines, and carbonyl groups, wherein the ratio of the first functional groups to the second functional groups (first functional groups / second functional groups) on one surface in the thickness direction of the conductive carbon layer measured using X-ray photoelectron spectroscopy with a photoelectron take-off angle of 90° is 4.0 or less, and the oxygen atom content O ９０ and the carbon atom content C ９０ The ratio calculated from ９０ / C ９０ ) is 0.13 or more.

2. The electrode according to claim 1, further comprising a metal underlayer between the substrate film and the conductive carbon layer.

3. A biosensor comprising the electrode according to claim 1 or 2.

4. A method for manufacturing an electrode according to claim 1 or 2, comprising: a preparation step of preparing a substrate film; a conductive carbon layer arrangement step of arranging a conductive carbon layer on one thickness-wise side of the substrate film to manufacture a laminate; and a plasma treatment step of performing plasma treatment on the one thickness-wise side of the laminate in the presence of nitrogen gas.

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