WO2010004690A1

WO2010004690A1 - Carbon electrode, electrochemical sensor, and carbon electrode manufacturing method

Info

Publication number: WO2010004690A1
Application number: PCT/JP2009/002794
Authority: WO
Inventors: 田光公康; 松本達; 上條憲一; 津田健一郎; 二瓶史行; 成田薫
Original assignee: 日本電気株式会社
Priority date: 2008-07-09
Filing date: 2009-06-19
Publication date: 2010-01-14
Also published as: JPWO2010004690A1; JP5120453B2

Abstract

The carbon electrode (10) has an insulating substrate (1), a conductive layer (2) provided on said insulating substrate, a carbon film (3) provided on said conductive layer (2), and a water-permeable carbon layer (4) provided to cover said carbon film (3). Said carbon film (3) contains carbon having SP2 bonds and SP3 bonds. Said water-permeable carbon layer (4) contains carbon having SP2 bonds.

Description

Carbon electrode, electrochemical sensor, and carbon electrode manufacturing method

The present invention relates to a carbon electrode, an electrochemical sensor, and a method for producing a carbon electrode.

) Technology for detecting substances in solutions is required in a wide range of fields such as environmental assessment, food analysis, and medical diagnosis. So far, various methods such as chromatography, electrophoresis, quartz crystal method, and electrochemical method have been put into practical use. Among these, the electrochemical method is most commonly used because it has high detection sensitivity, is easy to operate, and is easy to downsize the apparatus.

Electrochemical measurement is a technique for analyzing the substance in a solution by controlling the potential and current of an electrode immersed in the solution and measuring them. An apparatus for detecting and quantifying a substance using an electrochemical measurement method is particularly called an electrochemical sensor.

Demands for the above electrochemical sensor include the following. 1) The measurement can be performed stably for a long time. 2) High measurement sensitivity. 3) Easy to manufacture.

Electrochemical sensor performance varies greatly depending on the electrode material. As a material for the electrode, a conductive material such as a metal such as platinum, gold, silver or mercury, or carbon is generally used. In addition, for the purpose of improving measurement sensitivity and reaction selectivity, the electrode surface is loaded with a biomolecule such as an enzyme or an antibody, a catalyst, a modifying substance such as an electron transfer mediator, or coated with a molecule-selective membrane or the like. An electrode may be used.

Among these, it is known that an electrode made of a metal material is easy to manufacture and has high sensitivity under relatively low potential measurement conditions. However, the metal electrode is 1.0 V vs. * Solvent electrolysis and electrode dissolution reactions occur actively under conditions of higher potential than about Ag / AgCl. Then, since the reaction current of the solvent flows in a large amount, it is impossible to detect a weak change in the current value due to the reaction of a trace component, and there is a problem that the sensitivity of the sensor is significantly impaired.

On the other hand, an electrode made of a carbon material has an advantage that the solvent is hardly electrolyzed even under a high potential condition, and the electrode itself is hardly oxidized and reduced. Therefore, high detection sensitivity and electrode durability can be obtained even under high potential conditions. Further, since measurement under a high potential condition is possible, there are many detectable substances, and a more versatile sensor can be constructed.

Examples of such a carbon electrode include an electrode made by curing a carbon paste (see, for example, Patent Document 1), a glassy carbon electrode made by firing a polymer (see, for example, Patent Document 2), and a gas phase. An electrode (for example, Patent Document 3) made by forming a carbon film by a growth method is known. However, since these electrodes have a small surface area, there is a problem that the current density is low and the sensitivity is poor when an electrochemical sensor is used.

On the other hand, carbon nanotubes (hereinafter referred to as CNT) are known as carbon materials having a large specific surface area. CNT is a carbon material in which a graphite layer has a cylindrical shape and is expected to be applicable to highly sensitive electrodes because of its high conductivity. As an electrochemical sensor using CNTs, a sensor in which a composition containing a hydrophilic polymer and carbon nanotubes is applied to an electrode is disclosed (Patent Document 4). In this patent document, it is described that carbon, a metal, an alloy, and various compounds are used as an electrode material. In particular, it is described that graphite, pyrolytic carbon, glassy carbon, acetylene black, or carbon black is used as the carbon material.
Japanese Patent Laid-Open No. 1-240849 JP-A-5-155610 JP 2007-316038 A JP 2006-292495 A

However, a conventional electrode using CNT has a problem that stability cannot be obtained when used in a solution. For example, among the descriptions in Patent Document 4, in the case of an electrode configuration in which CNT is applied on a metal or alloy, the solution permeates the CNT layer and contacts the metal or alloy. Then, as described above, the reaction of the solvent occurs on the metal or alloy and the sensitivity is lowered. Furthermore, when gas is generated by this reaction, the CNT layer is peeled off, making it difficult to use the electrode.

Furthermore, according to the investigation by the inventors, a carbon electrode produced by applying CNT to a specific carbon material such as a diamond film sometimes detaches from the electrode surface during measurement. As this cause, it is considered that the adhesion between the CNT and the diamond film is low. For example, a diamond film synthesized by the vapor phase growth method described in Patent Document 3 is known to have very little solution penetration. However, when CNT is applied on the diamond film, the CNT is detached from the electrode surface during measurement. As the electrode surface area changes, the sensor characteristics drift when the measurement time is prolonged.

Also, the electrode with CNT coated on the diamond film had a high electrical resistance. When the electrical resistance is high, electrons reacted on the electrode surface are not transmitted quickly, resulting in low sensitivity. This may be due to the high contact resistance between the CNT and the diamond film.

Therefore, conventionally, studies on carbon materials that provide high adhesion and low contact resistance when CNT is applied have been insufficient.

In addition to CNTs, carbon nanohorns, fullerenes, carbon blacks, and the like are known as carbon materials having a large specific surface area.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a carbon electrode having low electric resistance and capable of performing stable measurement with high measurement sensitivity.

According to the present invention,
An insulating substrate;
A conductive layer provided on the insulating substrate;
A first carbon layer provided on the conductive layer;
A second carbon layer provided to cover the first carbon layer;
With
The first carbon layer includes carbon having an SP2 bond and an SP3 bond and having an amorphous structure;
The second carbon layer is provided with a carbon electrode including carbon having an SP2 bond.

The present invention provides a carbon electrode having a low electrical resistance and capable of stable measurement with high measurement sensitivity.

The above-described object and other objects, features, and advantages will become more apparent from the preferred embodiments described below and the accompanying drawings.
It is sectional drawing of the carbon electrode in embodiment of this invention. It is sectional drawing of the carbon electrode in embodiment of this invention. It is sectional drawing of the modification electrode in embodiment of this invention. It is a flowchart of the manufacturing method of a carbon electrode. It is a top view which shows the mode of the patterning of an electrochemical sensor. It is sectional drawing of the electrochemical sensor in embodiment of this invention. In Example 4, it is a figure which shows arrangement | positioning of 48 sets of electrodes. It is an experimental result of Example 1. It is sectional drawing of the carbon electrode in embodiment of this invention.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals, and description thereof will be omitted as appropriate. The carbon electrode of 1st Embodiment is demonstrated with reference to FIG.

The carbon electrode 10 of the first embodiment includes an insulating substrate 1, a conductive layer 2 provided on the insulating substrate 1, a first carbon layer provided on the conductive layer 2, A second carbon layer provided to cover the first carbon layer, wherein the first carbon layer includes carbon having an SP2 bond and an SP3 bond and having an amorphous structure, and the second carbon layer includes , Including carbons having an SP2 bond.
In the first embodiment, the carbon film 3 is used as the first carbon layer, and the water permeable carbon layer 4 is used as the second carbon layer.

As the material of the insulating substrate 1, a main material made of a highly insulating material such as ceramics, glass, quartz, or plastic can be used. A member excellent in water resistance, heat resistance, chemical resistance, and adhesion to the conductive layer 2 is desirable, and glass is particularly desirable.

The conductive layer 2 may be provided on the insulating substrate 1, or may have a higher conductivity than the carbon film 3. It is considered that the series resistance of the carbon film 3 can be lowered by providing the conductive layer 2. Thereby, the resistance loss at the time of electrochemical measurement is reduced, and the detection sensitivity of the sensor is improved.

The material used for the conductive layer 2 is preferably a material having a low contact resistance with the carbon film 3. For example, Ti, Cr, Cu, Au, Pt, Ni, Ir, W, Mo, TiN, TaN, Pd, Mg, Al or an alloy of these elements or a conductive film of an alloy of these elements and carbon is used. be able to.

The conductive layer 2 may be composed of two or more conductive films. For example, in order to improve the adhesion between the conductive layer 2 and the insulating substrate 1, Cr, Ti, W, etc. are formed on the insulating substrate 1. In addition, other conductive films may be formed.

The conductive layer 2 can be formed by sputtering, ion plating, vacuum deposition, CVD, electrolysis, or the like. The formation method is not limited, but a sputtering method is preferably used. Thereby, not only the adhesiveness with the insulating substrate 1 is good, but accurate patterning is possible, and mass productivity can be improved.

The carbon film 3 may be provided so as to cover the conductive layer 2. As the carbon film 3, a carbon film in which SP2 bonds and SP3 bonds are mixed is used.

The carbon film 3 has a dense film structure because it is a film in which SP2 bonds and SP3 bonds are mixed. With this dense film structure, the occurrence of cracks in the carbon film 3 can be suppressed. Therefore, even if it is immersed in the solution for a long time, the solution does not penetrate into the carbon film 3 and the change in the electrode area hardly occurs.

Furthermore, since the solution is not permeated by being covered with the carbon film 3 having a dense film structure, it is possible to prevent contact between the conductive layer 2 and the solution. Thereby, electrolysis of the solvent on the surface of the conductive layer 2 and dissolution reaction of the conductive layer 2 do not occur, and high detection sensitivity and stability are obtained.

When the carbon film 3 is formed so as to cover all surfaces including the side surface of the conductive layer 2, the conductive layer 2 is completely protected. However, the area of the side surface of the conductive layer 2 is the carbon film 3 and the water-permeable layer. The surface area of the conductive carbon layer 4 is negligibly small, and even if an electrochemical reaction occurs on the side surface of the conductive layer 2, the flowing current value is negligibly small.

Therefore, the upper surface of the conductive layer 2 only needs to be covered with the carbon film 3. When the side surface of the conductive layer 2 is not covered with the carbon film 3, the conductive layer 2 and the carbon film 3 can be processed at the same time when the patterned carbon electrode 10 is produced.

Moreover, the carbon film 3 has π electrons due to the SP2 bond. Therefore, the carbon film 3 exhibits conductivity by having π electrons. Further, when the carbon film 3 has π electrons, a π electron and π-π interaction of the water permeable carbon layer 4 is formed, thereby improving the adhesion between the carbon film 3 and the water permeable carbon layer 4.

This prevents the water-permeable carbon layer 4 from being peeled off in the solution, and a highly stable sensor can be constructed. Further, when the π-π interaction is formed, the contact resistance between the carbon film 3 and the water permeable carbon layer 4 is lowered. Accordingly, it is possible to configure the carbon electrode 10 with high detection sensitivity.

Further, the carbon film 3 has chemical resistance, high potential resistance, and high mechanical strength by having the SP3 bond. Thereby, since the tolerance to severe conditions, such as application of a high electric potential and repeated measurement, is high in an acidic solution, even if the carbon film 3 is damaged, the penetration of the solution can be suppressed.

The carbon film 3 preferably contains carbon having an amorphous structure. By including carbon having an amorphous structure, the film structure becomes denser, so that the penetration of the solution into the carbon film 3 is further reduced and the chemical resistance is improved. Examples of carbon having an amorphous structure having such characteristics include diamond-like carbon and amorphous carbon.
Whether the carbon film has an amorphous structure can be confirmed by Raman scattering spectroscopy using a visible light laser. For example, it is known that one sharp peak is observed near 1584 cm ^{−1 in} graphite, while a broad peak is observed near 1584 cm ⁻¹ in a carbon film having an amorphous structure.

Furthermore, the carbon film 3 may contain elements other than carbon. By including an element other than carbon, the conductivity of the carbon film 3 is improved. In addition, hardness and chemical resistance are improved. As these elements, metal elements including all elements generally used for doping can be used. Examples thereof include Cr, Ti, Si, N, B, Ar, Au, Pt, Cu, Ag, Fe, S, P, and H.

The ratio of SP2 bond and SP3 bond (SP2 / SP3 value) is not particularly limited, but is preferably 0.01 or more and 100.0 or less, more preferably 0.1 or more and 10.0 or less. The reason is that when the bond ratio is within this range, a sufficiently large π electron and a dense film structure is formed.

If the ratio is too low, there are few π electrons, so that the conductivity and adhesion with the water-permeable carbon layer 4 are insufficient. On the other hand, if the ratio is too high, a dense film structure cannot be obtained, resulting in insufficient water resistance, chemical resistance, high potential resistance, and mechanical strength.

Further, in the present embodiment, it was found from the electron microscope image of the carbon film 3 that the carbon film 3 has the same structure when the SP2 / SP3 value is 0.1 or more and 10.0 or less.

The thickness of the carbon film 3 is not particularly limited, but is preferably 0.02 μm or more and 20 μm or less. The reason is that the water resistance and electrical conductivity of the carbon film 3 are sufficiently secured when the thickness is within this range. If the film thickness is smaller than 0.02 μm, pinholes increase in the carbon film 3 and solution penetration tends to occur. On the other hand, if the film thickness is larger than 20 μm, the carbon film 3 has a high resistance and the measurement sensitivity is lowered.

The method for producing the carbon film 3 is not particularly limited, but a vapor phase growth method is preferably used because the film thickness and characteristics are easily controlled. For example, magnetron sputtering, radio frequency (RF) sputtering, direct current (DC) sputtering, counter target sputtering, electron cyclotron resonance (ECR) sputtering, ion beam sputtering (IBS), ion plating, ionization deposition So-called physical vapor deposition can be used. Alternatively, so-called chemical vapor deposition (CVD) methods such as plasma chemical vapor deposition (CVD), thermal CVD, and ion beam deposition (IBS) can be used.

Of these, the sputtering method is preferably used because the ratio of the SP2 bond and the SP3 bond can be easily controlled. In the sputtering method, the coupling ratio is controlled by adjusting the bias voltage.

Furthermore, in the carbon film 3, the coupling ratio between the SP2 bond and the SP3 bond may change stepwise from the insulating substrate 1 without any clear distinction between the films. Since the seam of the film is eliminated, stress concentration at the interface between different materials does not occur, and peeling of the carbon film 3 can be suppressed.

Preferably, the SP2 / SP3 value of the carbon film 3 may be maximized near the interface between the carbon film 3 and the water-permeable carbon layer 4. Thereby, the vicinity of the interface of the carbon film 3 in contact with the water permeable carbon layer 4 has a high SP2 / SP3 value, so that the adhesion with the water permeable carbon layer 4 can be improved. Further, the carbon film 3 other than the vicinity of the interface may have a low SP2 / SP3 value, whereby the penetration of the solution is prevented and the protective action for the conductive layer 2 can be improved.

The water permeable carbon layer 4 is provided so as to cover the carbon layer 3. The water permeable carbon layer 4 is a layer in which powdery carbon having a nanostructure is fixed.

As the powdery carbon having a nanostructure constituting the water-permeable carbon layer 4, one having SP2 bond is used. By having the SP2 bond, the water-permeable carbon layer 4 has π electrons. By having π electrons, powdered carbon having nanostructures can be bonded to each other by π-π interaction to form a layer.

Furthermore, the water permeable carbon layer 4 is considered to form a π-π interaction with the carbon of the carbon film 3. Therefore, the adhesion between the water-permeable carbon layer 4 and the carbon film 3 is improved, and the contact resistance can be reduced.

The water-permeable carbon layer 4 can be formed by applying a solution in which powdered carbon having a nanostructure is dispersed to the carbon film 3. The coating method is not particularly limited, and spin coating, dip coating, spray coating, dispensing, screen printing, ink jet, and the like can be used.

Of these, the spin coat method is preferably used because of its high uniformity and reproducibility. The concentration and amount of the solution used for spin coating can be determined by appropriate examination. Moreover, as a solvent, if these carbon materials disperse | distribute, it will not specifically limit, Water, a buffer solution, an organic solvent, and its mixture can be used.

The method for dispersing the carbon material is not particularly limited, and for example, ultrasonic treatment can be used. After the application, a drying step can be added as necessary. The water permeable carbon layer 4 formed by this method can be bonded to the carbon film 3 by forming a layer by physical adsorption such as π bond or van der Waals force.

Since the water-permeable carbon layer 4 thus formed is composed of powdered carbon having a nanostructure, it is possible to form irregularities on the surface and to form voids in the layer. Thereby, electrochemical measurement can be performed with a large specific surface area, and measurement sensitivity can be improved.

The solution penetrates into the water-permeable carbon layer 4, but the penetration of the solution is suppressed by the carbon film 3 existing thereunder as described above. Therefore, the electrode area can be stabilized after the solution has completely penetrated into the water-permeable carbon layer 4. Further, since the carbon film 3 hardly generates gas from the electrode surface even when a high potential of about 1 V is applied, the water-permeable carbon layer 4 is hardly peeled off. Further, since the carbon layer 3 has good chemical resistance and high potential resistance, even if the solution penetrates into the water-permeable carbon layer, the carbon layer 3 is hardly damaged or dissolved during the electrochemical measurement. . Therefore, it is possible to obtain an electrode having high stability even in long-time measurement.

The material of the water permeable carbon layer 4 is not particularly limited as long as it is powdery carbon having a nanostructure having an SP2 bond. For example, graphite, amorphous carbon, diamond-like carbon, carbon fiber, carbon black, acetylene black, Examples include ketjen black (registered trademark), carbon nanotubes, carbon nanohorns, and carbon nanofibers. These may be used as a single type or as a mixture of a plurality of types.

Of these, carbon nanotubes or carbon nanohorns can be particularly preferably used. The reason for this is that since it has a needle-like structure, the contact area with the carbon film 3 is increased, and a large number of π-π interactions are formed to obtain high adhesion and low contact resistance. It is possible to obtain a highly stable electrode because of its excellent chemical resistance and high potential resistance.

When forming the water permeable carbon layer 4, the binding force of the π-π interaction may be supplemented as necessary. For example, the fixing force can be increased by modifying and crosslinking the functional groups on the surfaces of the powdered carbon having a nanostructure and the carbon film 3, or adding a fixing agent such as a binder.

Further, the water permeable carbon layer 4 may be subjected to a hydrophilic treatment. When the water-permeable carbon layer 4 becomes hydrophilic, the time required for the penetration of the solution to be accelerated and the electrode to show a stable response is shortened.

The method of the hydrophilic treatment is not particularly limited, and for example, a method of mixing and applying a hydrophilic substance to the water permeable carbon layer 4 or a method of exposing to a plasma atmosphere can be used. These treatments may be performed after the permeable carbon layer 4 is formed on the carbon layer 3, or for powdered carbon having a nanostructure as a raw material of the permeable carbon layer 4 and a dispersion thereof. You may do it.

Examples of gas components for creating a plasma atmosphere include oxygen, nitrogen, and argon. Any hydrophilic substance can be used as long as it has hydrophilicity, and there are polymers such as acrylamide, ethylene glycol, ethylene oxide, ethyleneimine, and phospholipid. Of these, the method of applying a hydrophilic material is particularly preferable because it has little influence on the crystal structure of carbon.

Also, the solution penetration time into the water permeable carbon layer 4 can be shortened by making the density of the water permeable carbon layer 4 sparse. The density of the water-permeable carbon layer 4 can be adjusted by the concentration and amount of the carbon material dispersion applied to the carbon film 3 when the water-permeable carbon layer 4 is formed.

Since the carbon film 3 and the water-permeable carbon layer 4 are laminated and the contact area between both layers is large, even if the density of the water-permeable carbon layer 4 is sparse, it is possible to obtain a low-resistance electrode. When the density of the layer 4 decreases, the surface area decreases and the current value decreases. The optimum density can be appropriately adjusted as necessary.

The carbon electrode 10 having the configuration as described above functions as a working electrode of an electrochemical sensor. When actually used as an electrochemical sensor, a reference electrode 11 and a counter electrode 12 are appropriately used.

(Production method)
Then, the manufacturing method of the carbon electrode 10 which concerns on this Embodiment is demonstrated. FIG. 4 shows a flowchart of the method for manufacturing the carbon electrode 10 according to the present embodiment. The manufacturing method of the carbon electrode 10 includes a step of forming the conductive layer 2 (step S10), a step of forming the carbon film 3 (step S20), a step of forming the water-permeable carbon layer 4 (step S30), and a step of dicing. (Step S40). The method of each step will be described in detail below.

Steps S10 and 11: Formation of Conductive Layer First, the conductive layer 2 is formed on the insulating substrate 1 by sputtering (step S10). The method for forming the conductive layer 2 is not limited to the sputtering method, and an ion plating method, a vacuum deposition method, a CVD method, an electrolytic method, or the like may be used. Further, the conductive layer 2 is patterned on the insulating substrate 1 as necessary (step S11). For the patterning of the conductive layer 2, an etching method, a lift-off method, a sand blast method, or the like can be used.

Steps S20 and 21; Formation of Carbon Film Subsequently, the carbon film 3 is formed on the insulating substrate 1 on which the conductive layer 2 is formed (Step S20). The carbon film 3 is formed by a so-called physical vapor deposition method such as a sputtering method or an ion plating method, a plasma chemical vapor deposition (CVD) method, a thermal CVD method, an ion beam deposition (IBS) method, or the like. A so-called chemical vapor deposition (CVD) method can be used. By being formed by the vapor deposition method, the carbon film 3 forms a dense film structure and covers the surface of the conductive layer 2. Further, the carbon film 3 is patterned as necessary (step S21). As a patterning method, a method of forming a mask made of ceramics, photoresist or the like on the carbon film 3 and etching with oxygen plasma or the like, a method of processing by sand blasting using a metal mask, or the like can be used.

Steps S30 and 31: Formation of a water-permeable carbon layer On the carbon layer 3, a powdery carbon dispersion having a nanostructure is applied by spin coating, and the solvent volatilizes to form the water-permeable carbon layer 4. (Step S30). The water permeable carbon layer 4 is in close contact with the carbon film 3 by π-π interaction. Further, the water permeable carbon layer 4 is patterned as necessary (step S31). As the patterning method, etching using oxygen plasma using a mask, a lift-off method, or the like is used. Note that the coating method is not limited to the spin coating method, and a screen printing method, an ink jet method, or the like may be used. When a method that can be applied onto a pattern, such as a screen printing method or an ink jet method, is used, Step S30 and Step S31 are performed at a time, and the process can be omitted.

Step S40: Dicing The substrate is diced according to the patterned shape and cut into a plurality of carbon electrodes 10. Examples of the dicing method include a method using a dicing blade and a scribe device.

The carbon electrode 10 is manufactured by the above steps S10 to S40. The produced carbon electrode 10 is used as a working electrode of an electrochemical sensor. That is, it is electrically connected to a current measuring device (not shown) or the like via an external substrate by a method such as wire bonding. The electrochemical sensor 14 is used in combination with the reference electrode 11 and the counter electrode 12.

In addition, when it is set as the structure where the carbon film 3 was provided only on the upper surface of the conductive layer 2, step S11 may be omitted and the carbon film 3 and the conductive layer 2 may be patterned in the process of step S21. Thereby, the process of forming the mask in step S11 is omitted, and the manufacturing is simplified. As the patterning method, a single processing method or a combination of two or more processing methods may be used.

For example, the carbon film 3 and the conductive layer 2 are patterned at once by sand blasting, or after patterning the carbon film 3 by etching with oxygen plasma, the conductive layer 2 exposed by patterning of the carbon film 3 is patterned by sand blasting or the like. Can do. For the patterning, an appropriate method may be used as appropriate based on the processing characteristics of the film to be used. However, it is preferable that the patterning can be further simplified if it can be produced by a single processing method.

Similarly, the step of forming the mask by patterning the carbon film 3 and the conductive layer 2 in the step of patterning the water-permeable carbon layer 4 in step S31 without step S11 and step S21 can be omitted. If the water-permeable carbon layer 4, the carbon film 3, and the conductive layer 2 are patterned in step S31, the process of forming a mask can be further omitted, and the manufacturing is simplified.

Alternatively, the carbon film 3 and the water permeable carbon layer 4 may be formed after patterning the conductive layer 2 in step S11, and the carbon film 3 and the water permeable carbon layer 4 may be patterned in the process of step S31. If it does in this way, the pattern of the conductive layer 2 and the carbon film 3 can be made into a different shape. Therefore, since the wall surface of the conductive layer 2 can be made to be completely covered with the carbon film 3, an electrode with very high stability can be obtained.

According to the present embodiment, the series resistance can be lowered by forming the conductive layer 2 under the carbon film 3. Further, the contact resistance between the carbon film 3 and the water permeable carbon layer 4 can be reduced by laminating the carbon film 3 and the water permeable carbon layer 4. Therefore, an electrode having low resistance can be obtained, and resistance loss during electrochemical measurement is reduced, so that the detection sensitivity of the sensor can be improved.

Further, the specific surface area can be improved by forming the water-permeable carbon layer 4 so as to cover the carbon film 3. When the specific surface area is large, electrochemical measurement can be performed in a large area, and the measurement sensitivity is improved.

Further, since the water-permeable carbon layer 4 is a sparse layer, when the measurement solution is touched, the solution quickly penetrates into the inside. Therefore, it is possible to shorten the time required for the electrode immersed in the solution to show a stable response.

Furthermore, the conductive layer 2 is prevented from contacting the solution by being covered with the carbon film 3. Since the carbon film 3 has a dense film structure, it can be configured such that no cracks occur and no solution permeates. Thereby, even if it immerses in a solution for a long time, the change of an electrode area can be suppressed. In addition, electrolysis of the solvent on the surface of the conductive layer 2 and dissolution reaction of the conductive layer 2 do not occur, and high detection sensitivity and stability can be obtained.
(Second Embodiment)

The second embodiment will be described with reference to FIG. FIG. 9 is a cross-sectional configuration diagram of the carbon electrode according to the present embodiment. In the carbon electrode of the present embodiment, a third carbon layer is added to the carbon electrode 10 according to the first embodiment. Note that the same configuration as that of the first embodiment will be omitted.

The carbon electrode 10 of the second embodiment is characterized in that the first carbon layer further includes at least one third carbon layer having an SP2 / SP3 value different from that of the first carbon layer.
Further, in the carbon electrode 10 of the second embodiment, the first carbon layer and the second carbon layer are in contact with each other, and the SP2 / SP3 value of the first carbon layer is equal to SP2 / SP3 of the third carbon layer. It may be higher than the value.
Here, in the second embodiment, the carbon film 3 is used as the first carbon layer, the water permeable carbon layer 4 is used as the second carbon layer, and the carbon film 30 is used as the third carbon layer.

The carbon film 10 of the second embodiment may use the carbon film 3 described above. Further, two or more carbon films 3 and carbon films 30 having different SP2 / SP3 values may be laminated.

Among these, since the carbon film 3 and the carbon film 30 having both water resistance, chemical resistance, high potential resistance, durability and conductivity can be obtained, the carbon film 3 and the carbon film having two or more different SP2 / SP3 values. It is particularly preferable that 30 is laminated.

The order in which the carbon film 3 and the carbon film 30 are stacked is not particularly limited, but when the carbon film 3 is in contact with the water permeable carbon layer 4, the carbon film 3 has a high SP2 / SP3 value, and the carbon film 30 has an SP2 / It is particularly preferable to include at least one layer having a low SP3 value.

The reason is that the carbon film 3 in contact with the water permeable carbon layer 4 has a high SP2 / SP3 value, so that the adhesion with the water permeable carbon layer 4 is improved. Further, the carbon film 30 includes at least one layer having a low SP2 / SP3 value, thereby preventing the solution of the carbon film 30 from penetrating and improving the protective action on the conductive layer 2.

The carbon film 3 is formed on an upper surface of the conductive layer 2 provided with an intermediate layer containing at least one selected from Cr, Ti, and W in order to improve adhesion with the conductive layer 2. May be. The intermediate layer can be formed by sputtering or the like.

In this embodiment, the composition of the conductive layer 2 and the intermediate layer may be mixed near the interface between the conductive layer 2 and the intermediate layer. Furthermore, the composition of the intermediate layer and the carbon film 3 may be mixed in the vicinity of the interface between the intermediate layer and the carbon film 3.

The intermediate layer does not have to form a clear interface with the conductive layer 2 and the carbon film 3, and each composition of the conductive layer 2 / intermediate layer / carbon film 3 is stepwise from the substrate surface in the vertical direction. Alternatively, a mixed gradient composition layer that changes to

As described above, when the mixed gradient composition layer is formed, stress concentration at the interface between different materials does not occur, so that the adhesiveness with the insulating substrate 1 is improved and a stable electrode can be obtained. The mixed gradient composition layer can be formed by setting the targets of the conductive layer 2, the intermediate layer, and the carbon film 3 in the same chamber and performing sputtering while rotating the substrate.

For the deposition of the carbon film 3 and the carbon film 30 (step S20), the sputtering method is preferably used because the control of the ratio of SP2 bonds to SP3 bonds is easy. In the sputtering method, the coupling ratio is controlled by adjusting the bias voltage. Thereby, it can be set as the structure by which the two or

more carbon films

3 and 30 from which SP2 / SP3 value differs were laminated | stacked.
(Third embodiment)

The third embodiment will be described with reference to FIG. FIG. 3 is a cross-sectional configuration diagram of the modified electrode according to the present embodiment. In the modified electrode of the present embodiment, a modifying substance 9 is added to the carbon electrode 10 according to the first embodiment. Note that the same configuration as that of the first embodiment will be omitted.

The carbon electrode 10 of the third embodiment is characterized in that the carbon electrode 10 of the first embodiment further includes a modifier 9 supported on the second carbon layer.
In the third embodiment, the water permeable carbon layer 4 is used as the second carbon layer. Furthermore, the carbon electrode 10 of the third embodiment can be used as a modified electrode.

As shown in FIG. 3, a conductive layer 2 is formed on an insulating substrate 1, and at least the upper surface thereof is covered with a carbon film 3. A water permeable carbon layer 4 is formed so as to cover the surface of the carbon film 3. The modifying substance 9 is supported inside and outside the water-permeable carbon layer 4.

The modifying substance 9 is not particularly limited, and a substance generally used for a modifying electrode is used. Examples of the modifying substance 9 include a substance that promotes the oxidation-reduction reaction of the target substance, a substance that mediates transfer of electrons between the target substance and the electrode, a substance that has a molecular recognition function, a substance that regulates substance permeability, and the like Is used.

More specifically, examples of the modifying substance 9 include a catalyst, an enzyme, a metal complex, an electron transfer mediator, an antibody, a nucleic acid, a receptor, a protein, a lipid, a polymer, a cell, a microorganism, and a living tissue. A single substance and a plurality of substances are used. By carrying these modifiers 9 inside and outside the water-permeable carbon layer 4, an electrochemical sensor that improves detection of substances that do not directly react with the electrode, sensitivity, response specificity, stability, etc. Is possible.

The modifying substance 9 may be supported by applying a substance dispersed in a solvent on the water-permeable carbon layer 4. As the type of the solvent, an aqueous solution such as a buffer solution or an organic solvent such as alcohol in which the modifying substance 9 is dispersed while maintaining the activity is appropriately used.

Since the water-permeable carbon layer 4 has water permeability, the applied dispersion penetrates into the water-permeable carbon layer 4 and the modifier 9 is supported inside and outside the carbon layer. The solvent may be added with a crosslinking agent such as glutaraldehyde or a polymer such as polyethylene glycol or vinyl alcohol in order to firmly support the modifying substance.

When the modifying substance penetrates into the carbon film, the modifying substance 9 adheres to the water-permeable carbon layer 4 and is prevented from peeling by the anchor effect. Therefore, a modified electrode with high stability can be obtained.

Furthermore, since the carbon of the water permeable carbon layer 4 has high conductivity, it functions as an electrode as a whole including the ends of the carbon. Therefore, the electrochemically reactive substance generated by the action of the modifying substance 9 is quickly converted into an electrical signal by the nearby water-permeable carbon layer 4 and the carbon film 3, and there is little outflow from the electrode due to diffusion. Since the action of the modifying substance 9 can be detected efficiently, a highly sensitive modified electrode can be obtained.

Further, since the water-permeable carbon layer 4 has a large specific surface area, the water-permeable carbon layer 4 can carry a large amount of modifier 9. As a result, the effect of the modifying substance 9 is remarkably exhibited, and a modified electrode with particularly enhanced detection sensitivity and response specificity can be obtained.

The modifier 9 is supported on the patterned water-permeable carbon layer 4 before dicing (step S40). The modification substance 9 may be supported by, for example, spin coating a dispersion of the modification substance 9.

According to the present embodiment, the modified substance 9 permeates and is carried inside the water-permeable carbon layer 4, whereby a modified electrode with particularly improved detection sensitivity and stability can be obtained. In addition, a large amount of the modifying substance 9 is immobilized on the water-permeable carbon layer 4, and a modified electrode with particularly enhanced detection sensitivity and response specificity can be obtained.
(Fourth embodiment)

A fourth embodiment of the present invention will be described with reference to FIG. 5 and FIG.

FIG. 6 shows a cross-sectional view of the electrochemical sensor 14 according to the present embodiment. The electrochemical sensor 14 has an insulating substrate 1, a working electrode 13, a reference electrode 11, and a counter electrode 12.

FIG. 5 shows a top view of the electrochemical sensor 14. FIG. 6 shows a structure in which a plurality of electrochemical sensors 14 are formed on the insulating substrate 1. When the working electrode 13 is a microelectrode, the reference electrode 11 can also serve as the counter electrode 12. In this case, the electrochemical sensor 14 includes the working electrode 13 and the reference electrode 11. It's okay.

The working electrode 13 includes a conductive layer 2, a carbon film 3, and a water permeable carbon layer 4. The working electrode 13 formed on the insulating substrate 1 can use the carbon electrode 10 described in any of the first to third embodiments, but is not limited to the carbon electrode 10.

The reference electrode 11 is preferably a metal layer mainly composed of silver. Of these, the formation of silver / silver chloride is particularly preferred because of the high stability of the redox potential in the measurement solution.

When forming silver / silver chloride, a layer of Ti, Cr, or the like may be sandwiched between the reference electrode 11 and the insulating substrate 1 in order to improve adhesion to the substrate. Further, silver / silver chloride may be formed so as to cover the surface of an electrical wiring (not shown) formed of a layer such as Pt and Au formed on the insulating substrate 1.

Silver / silver chloride can be formed, for example, by anodic polarization in aqueous hydrochloric acid after forming silver by sputtering.

The counter electrode 12 is preferably a platinum group element. As the counter electrode 12, platinum having particularly excellent chemical resistance is preferable. When platinum is formed, a layer such as Ti or Cr may be sandwiched between the insulating substrate 1 and the substrate so as to improve adhesion to the substrate.

The reference electrode 11 and the counter electrode 12 can be formed on the insulating substrate 1 by a lift-off method. The reference electrode 11 and the counter electrode 12 may be formed before or after the step of forming the conductive layer 2 (step S10). When the counter electrode 12 is made of the same material as that of the conductive layer 2, the step of forming the conductive layer 2 (Step S <b> 10) and the step of forming the counter electrode 12 can be performed simultaneously.

Furthermore, the method of forming silver used for the reference electrode 11 is not limited to the sputtering method, and may be formed by, for example, a plating method. When the plating method is used, an electric wiring made of Pt, Au or the like can be formed on the insulating substrate 1, and silver can be formed on the surface of the electric wiring by electrolytic plating.

Silver may be formed before or after the step of forming the conductive layer 2 (step S10). When the electric wiring is made of the same material as the counter electrode 12 or the conductive layer 2, the step of forming the electric wiring and the step of forming the counter electrode 12 or the conductive layer 2 (step S10) can be performed simultaneously.
(Fifth embodiment)

The fifth embodiment will be described with reference to FIG. In addition, description is abbreviate | omitted about the structure similar to 1st Embodiment. In the carbon electrode 10 of the present embodiment, a connection portion 8 is added to the carbon electrode 10 according to the first embodiment.

The electrochemical sensor of the fifth embodiment further includes a measurement unit (not shown) and a conductive wire 5, the measurement unit and the carbon electrode 10 are electrically connected by the conductive wire 5, and the conductive wire 5 is Through the first carbon layer and in electrical contact with the conductive layer 2, the surface of the conductive wire 5 is covered with an insulating film 6, and the surfaces of the insulating film 6 and the first carbon layer are sealed. It is characterized by being covered with a stopper 7.
In the fifth embodiment, the carbon film 3 is used as the first carbon layer.

As shown in FIG. 2, a conductive layer 2 is formed on an insulating substrate 1, and at least the upper surface thereof is covered with a carbon film 3. A water permeable carbon layer 4 is provided so as to cover the surface of the carbon film 3. The connection portion 8 includes a conductive wire 5 that penetrates the carbon film 3 and contacts the conductive layer 2, an insulating film 6 that covers the surface of the conductive wire 5, and a sealing material 7 that covers a portion where the conductive wire 5 penetrates the carbon film 3. Consists of.

The conducting wire 5 is connected to an electrochemical measurement device (not shown). By bringing the conductive wire 5 into contact with the conductive layer 2, a low resistance electric wiring is formed. Then, the resistance loss is reduced, so that electrochemical measurement can be performed with high sensitivity.

Furthermore, the surface of the conductive wire 5 is covered with an insulating film 6, and the penetration portion of the conductive wire 5 formed in the carbon film 3 is covered with a sealing material 7. As a result, the conductive wire 5 and the contact portion between the conductive wire 5 and the conductive layer 2 can be protected and a highly waterproof connection portion can be obtained. Thereby, the stability and durability of the electrode can be improved.

The conducting wire 5 is conductive. The conducting wire 5 is electrically connected to the conductive layer 2 by being provided so that at least one end penetrates the carbon film 3 and contacts the conductive layer 2.

Furthermore, another end of the conducting wire 5 is connected to an electrochemical measuring device. Thereby, the electrode potentials of the carbon film 3 and the water permeable carbon layer 4 can be controlled to function as working electrodes in electrochemical measurement.

A metal is preferably used as the material of the conducting wire 5. The reason is that the electrical resistance is low and the contact resistance with the conductive layer 2 is low. There are no particular limitations on the type of metal, but for example, Pt, Au, Ag, Cu, Al, Fe, Cr, Ni, Zn, In, Pb, Nb, Sn, and alloys based on these can be used. . In addition, the conducting wire 5 may be comprised from a single material and several types of materials. For example, it is possible to achieve both ease of manufacture and low resistance by using stainless steel having high hardness at the tip portion and using copper having low electrical resistance at other portions.

The conducting wire 5 can be brought into contact with the conductive layer 2 through the carbon film 3 by being driven by a puncher or the like. Since the carbon film 3 is a dense film, generation of cracks can be prevented even when the conductive wire 5 is driven. Therefore, the conductive layer 2 is protected from the solution by the carbon film 3 except for the portion where the conducting wire 5 penetrates.

Since it is easy to penetrate the carbon film 3 during manufacturing, the shape of the end of the conductive wire 5 is preferably a tapered shape such as a needle shape or a blade shape. Further, a so-called barb structure that is pointed in the direction opposite to the tip may be formed at the end. In particular, the barb structure is preferably embedded in the conductive layer 2. When there is a barb structure, the lead wire 5 is prevented from falling off, and it is possible to reduce defective electrical contact.

In addition, in FIG. 2, although the conducting wire 5 has a needle-like shape, the shape of the conducting wire 5 is not limited to this. For example, the shape of the cross section of the end portion of the conducting wire 5 is not particularly limited, and may be a circle, a polygon, or a curve. Of these, polygons and curves are particularly preferable.

The reason is that the contact area with the conductive layer 2 can be increased and the contact resistance is reduced. When the contact resistance decreases, a low-resistance electrode can be obtained, and a sensor with high detection sensitivity can be constructed.

Moreover, you may provide a some front-end | tip in the edge part of the conducting wire 5, for example, a sword mountain-like end part provided with two or more needle-like front-end | tips, an end part which has two or more said polygonal cross sections, and a plurality of curved cross sections It can be set as the edge part which has, and the edge part which mixed these shapes. By providing a plurality of tips on the conducting wire 5, the contact area with the conductive layer 2 can be increased and a low-resistance electrode can be obtained.

Moreover, the conducting wire 5 can be made into a clip shape. The conductive wire 5 penetrates the carbon film 3 by forming sharp irregularities inside the clip and sandwiching the substrate with the clip. Thereby, you may make the conducting wire 5 and the conductive layer 2 contact electrically. Since the conductive wire 5 and the conductive layer 2 are always in close contact with each other by the clip, it is possible to reduce electrical contact defects.

Further, since the connection part 8 can be removed, the connection part 8 can be reused by making the substrate disposable. It is not necessary to manufacture the connection portion 8 for each electrode, and the manufacturing of the electrode can be simplified.

Further, two or more conductive wires 5 may be connected to the conductive layer 2. The plurality of conductive wires 5 electrically connected to the same conductive layer 2 can act as a single electrode by being connected to the same working electrode connection part of the electrochemical measuring device. By connecting a plurality of conducting wires 5, the contact area with the conductive layer 2 can be increased, and a low resistance electrode can be obtained.

In FIG. 2, the leading end of the conducting wire 5 exists in the conductive layer 2, but the position of the leading end of the conducting wire 5 is not limited to this as long as the conducting wire 5 and the conductive layer 2 are electrically connected. For example, by using a material having high crack resistance such as plastic for the insulating substrate 1 and the tip of the conductive wire 5 is inserted into the plastic, the conductive wire 5 can be firmly fixed to the substrate and prevented from falling off. is there.

Except for the part inserted into the carbon film 3, the conductive wire 5 is completely covered with the insulating film 6 and the sealing material 7. In addition, as long as the electrical contact with the conductive layer 2 is not hindered, at least a part of the conductive wire 5 in the portion inserted into the carbon film 3 may be covered with the insulating film 6 and the sealing material 7. .

The insulating film 6 uses a water-impermeable electrical insulating film and covers the conductive wire 5. Thereby, since the conducting wire 5 does not contact with the solution, an electrochemical reaction at the time of applying the potential of the conducting wire 5 can be suppressed.

As the material of the insulating film 6, a material that is in close contact with the conductive wire 5 and the sealing material 7 can be used. Examples of the material of the insulating film 6 include plastics, silicon resin, and Teflon (registered trademark) resin. Among these, when a silicon resin and a Teflon (registered trademark) resin are used, a high chemical resistance is obtained, and a silicon resin is particularly preferable because it has high adhesion to the sealing material 7. These can be used in combination of a single type or a plurality of types. For example, a portion that does not contact the sealing material 7 may be covered with a plastic material such as enamel, and a portion that contacts the sealing material 7 may be covered with a silicon resin.

The sealing material 7 is formed so as to completely cover a portion where the conductive wire 5 penetrates the carbon film 3, and is provided so as to be in close contact with the insulating film 6 and the carbon film 3. The sealing material 7 prevents the solution from penetrating into the groove formed in the carbon film 3 due to the penetration of the conductive wire 5, thereby preventing the conductive layer 2 and the conductive wire 5 from contacting the solution. As a result, the waterproofness of the electrode is improved, and a highly stable sensor can be constructed.

The sealing material 7 is an electrically insulating elastic body. The material of the sealing material 7 is not particularly limited as long as it is an electrically insulating elastic body. For example, synthetic rubber such as nitrile rubber and fluorine rubber, natural rubber, thermoplastic elastomer, silicon resin, and the like can be used. . Of these, silicone resins are particularly preferred because of their high chemical resistance.

The sealing material 7 can be adhered and adhered to the carbon film 3 and the insulating film 6. The bonded sealing material 7 adheres firmly, preventing penetration of the solution and preventing the lead 5 from falling off. Thereby, a stable electrode can be obtained. Such a structure can be formed by pouring a softened sealing material 7 or a prepolymer of the sealing material 7 into a portion where the conductive wire 5 on which the insulating film 6 is formed is driven into the carbon film 3, and then curing. it can.

Further, the sealing material 7 may be adhered and adhered to the insulating film 6 and may be physically pressed and adhered to the carbon film 3. Thereby, even when the surface energy of the carbon film 3 is small and it is difficult to adhere the sealing material 7, it is possible to prevent the penetration of the solution.

Such a structure can be formed by adhering the sealing material 7 to the conductive wire 5 on which the insulating film 6 is formed, and driving the conductive wire 5 into the carbon film 3. Further, when the conductive wire 5 whose tip is covered with the sealing material 7 is used, when the carbon film 3 is driven, the sealing material 7 at the tip is peeled off, and the conductive wire 5 is exposed and electrically connected to the conductive layer 2. In addition, the sealing material 7 and the carbon film 3 can be brought into close contact with each other.

The connecting portion 8 is formed on the carbon film 3 after dicing (step S40). The connection portion 8 is formed by, for example, driving the conductive wire 5 covered with the insulating film 6 into the carbon film 3 except for the portion to be brought into contact with the conductive layer 2, and softening the sealing material 7 or at the portion where the conductive wire 5 is driven. It can be formed by pouring and curing the prepolymer of the sealing material 7. In the case where the same material is used for the sealing material 7 and the insulating film 6, the insulating film and the sealing material can be formed at the same time.

According to the present embodiment, a low resistance electric wiring is formed by bringing the conductive wire 5 into contact with the conductive layer 2. The resistance loss is reduced, and an electrode capable of performing electrochemical measurement with high sensitivity can be obtained.

Furthermore, since the connection part of the conducting wire 5 is protected by the insulating film 6 and the sealing material 7, it becomes possible to make the connection part highly waterproof. Thereby, it is possible to obtain an electrode with improved stability and durability.

According to the present embodiment, after the step of forming a conductive layer (step S10) on a single insulating substrate 1, the conductive layer is patterned (step S11) to form a plurality of conductive layers. After the step of forming the plurality of working electrodes 13, the reference electrode 11, and the counter electrode 12 at a time, and forming the water permeable carbon layer as the second carbon layer (step S30), the plurality of carbon electrodes 10 are divided into By dicing in units of electrochemical sensors 14, a plurality of electrochemical sensors 14 can be obtained, and an electrochemical sensor excellent in mass productivity can be obtained.

Note that the above-described embodiments are not independent of each other, and a plurality of embodiments can be combined as necessary.

Hereinafter, the present invention will be described using examples and comparative examples. The present invention is not limited to the following examples.
Example 1

A method for manufacturing the carbon electrode of Example 1 will be described.
First, a 10 mm × 10 mm (0.515 mm thick) quartz substrate was prepared, washed with acetone, and then washed with a solution containing the same amount of hydrogen peroxide and nitric acid.

Subsequently, a 300 nm platinum layer was formed on the quartz substrate by sputtering of platinum. By the lift-off method, the platinum layer was patterned into the working electrode and counter electrode designs shown in FIG. 5 to obtain a counter electrode.

Subsequently, a diamond-like carbon film having an SP2 / SP3 value of 0.01 or more and 100.0 or less and a thickness of 1 μm by controlling the coupling ratio of SP2 coupling and SP3 coupling by adjusting the bias voltage by ion beam sputtering. Formed.

The SP2 / SP3 value of this carbon film was found to be 2.5 from electron energy loss spectrometry. By analyzing the shape of the absorption peak in the vicinity of 284 eV in the allotrope consisting only of carbon by electron energy loss spectrometry, the difference in the binding state is clearly shown. By comparing this difference, the SP2 / SP3 value of the carbon film can be obtained. Further, it was found from the electron microscopic image of the carbon film that the carbon film had the same structure when the SP2 / SP3 value was 0.1 or more and 10.0 or less.
In addition, a broad peak was observed near 1584 cm ⁻¹ by Raman scattering spectroscopy using a visible light laser. Therefore, it was confirmed that the carbon film has an amorphous structure.

Subsequently, 10 mg of carbon nanohorn was added to 10 mL of dichloroethane and dispersed with an ultrasonic cleaner for 5 minutes. And 500 microliters of dichloroethane solutions containing carbon nanohorn were fractionated, and it was dripped on the board | substrate, and spin-coated on 2000 rpm and the rotation conditions for 30 second. The substrate was dried under a nitrogen atmosphere at 100 ° C. for 10 minutes.

Subsequently, a photoresist pattern was formed on the substrate, and the carbon nanohorn layer and the carbon film were patterned into the working electrode design shown in FIG. 5 by etching using oxygen plasma to obtain a working electrode.

Subsequently, a 300 nm silver layer was formed by silver sputtering, and a current of 0.8 mA was passed in a 0.1 M hydrochloric acid aqueous solution for 10 minutes to form silver / silver chloride. Then, the reference electrode was obtained by patterning into the reference electrode design of FIG. 5 by the lift-off method.

Subsequently, each electrode and the flexible substrate were electrically connected by wire bonding, and wiring was performed so that the current flowing through the working electrode could be measured. Here, waterproofing was applied to the portion connected by wire bonding.
(Comparative Example 1)

As Comparative Example 1, a conventional electrochemical sensor using a diamond film was used. The diamond electrode was produced according to the method described in Patent Document 3.
(Comparative Example 2)
As Comparative Example 2, an electrochemical sensor produced by applying carbon nanotubes on glassy carbon according to Patent Document 4 was used. The electrode was coated with 8 μL of a 0.25 W / W% aqueous solution of carboxymethylcellulose containing carbon nanotubes suspended at a content of 0.2 W / W% on commercially available glassy carbon (BAS), 37% dried for 1 hour. And produced.
(Comparative Example 3)

As Comparative Example 3, an electrochemical sensor was fabricated by applying CNTs on a carbon material consisting only of SP3 bonds. A diamond film was used as a carbon material consisting only of SP3 bonds. For the production of the diamond film, the same method as in Example 1 was used except for the method of Patent Document 3.

The characteristics of the electrochemical sensors of Example 1 and Comparative Examples 1 to 3 were evaluated. Evaluation items are measurement sensitivity, stability, electrode area, and electrical resistance. Measurement sensitivity and stability were evaluated by electrochemical measurement in an aqueous solution. A pH 7 phosphate buffer in which 0.1 M KCl, 0.4 mM ferrocenemethanol and 0.4 mM adenine were dissolved was used as a measurement solution. Immerse the electrochemical sensor in the solution, 0.2-1.8V vs. Cyclic voltammetry measurement was performed under a potential condition of Ag / AgCl.

The measurement sensitivity was determined to be better as the current value was higher by comparing the oxidation current values of ferrocene methanol and adenine. Stability was determined by repeating cyclic voltammetry for 50 cycles, and comparing the degree of waveform deformation, the smaller the deformation, the better. As for the electrode area, an electron microscope image on the electrode surface was compared, and the larger the specific surface area, the better. The electric resistance between the surface of the working electrode and the lead wire from the working electrode was measured by a two-terminal method, and the lower the electric resistance, the better.

・・・ Characteristics of each sensor are indicated by ○, △, × (Fig. 8).

The sensor of Example 1 had good measurement sensitivity, stability, electrode area, and electrical resistance. On the other hand, all of the sensors of Comparative Examples 1 to 3 have a defect in some characteristics.

The sensor of Comparative Example 1 had good electrode area stability and electrical resistance, but was inferior in measurement sensitivity and electrode area. In particular, since the electrode surface was smooth in the evaluation of the electrode area, the specific surface area was remarkably small compared to other electrodes. The sensor of Comparative Example 2 had good measurement sensitivity, electrode area, and electrical resistance. However, as the measurement was repeated, the current value gradually changed and the stability was poor. The electrode of Comparative Example 3 had a good electrode area. However, the electrode resistance was large and the electrode sensitivity was inferior. Further, CNT peeling occurred during the measurement, and the current value was not stable.

As described above, it was confirmed that the electrode of Example 1 had good measurement sensitivity, stability, electrode area, and electrical resistance, and exhibited excellent characteristics as an electrochemical sensor.
(Example 2)

A method for manufacturing the electrochemical sensor of Example 2 will be described.
First, a 10 mm × 10 mm (0.515 mm thick) quartz substrate was prepared, washed with acetone, and then washed with a solution containing the same amount of hydrogen peroxide and nitric acid.

Subsequently, a diamond-like carbon film having a thickness of 0.05 μm and an SP2 / SP3 value of 1.1 was similarly formed by ion beam sputtering. The SP2 / SP3 value of the carbon film was determined by electron energy loss spectrometry.
In addition, a broad peak was observed near 1584 cm ⁻¹ by Raman scattering spectroscopy using a visible light laser. Therefore, it was confirmed that the carbon film has an amorphous structure.

Subsequently, 10 mg of carbon nanohorn was added to 10 mL of dichloroethane and dispersed with an ultrasonic cleaner for 5 minutes. And 500 microliters of dichloroethane solutions containing carbon nanohorn were fractionated, and it was dripped on the board | substrate, and spin-coated on 2000 rpm and the rotation conditions for 30 second. It was dried for 10 minutes in a nitrogen atmosphere at 100 ° C.

Subsequently, the margin of one end was flattened, and a copper wire was soldered to the handle side of the alligator clip having sharp irregularities on the other end. A silicone resin prepolymer was applied to the connection portion of the copper wire and the surface of the clip, and the silicone resin was cured by placing it in an oven at 120 ° C. for 3 hours with the clip open. After cooling in the air, the substrate on which the working electrode was formed was sandwiched so that the sandwiching margin on which sharp irregularities were formed was in contact with the carbon film. The reference electrode and the counter electrode were electrically connected to the flexible substrate by wire bonding and wired so that the current flowing through the working electrode could be measured. Here, waterproofing was applied to the portion connected by wire bonding.

When the resistance of the produced electrode was measured with a tester, it was confirmed that the electrode could be made to have a lower resistance than before. Moreover, when it measured in aqueous solution, the penetration of the solution to the contact point of a crocodile clip and a platinum layer was prevented by the silicon resin, and it confirmed that it could be an electrode with higher stability compared with the past.
(Example 3)

A method for producing an electrochemical sensor using the modified electrode of Example 3 will be described.

First, a 10 mm × 10 mm (thickness 0.515 mm) quartz substrate was prepared, washed with acetone, and then washed with a solution containing the same amount of hydrogen peroxide and nitric acid.

Subsequently, a 300 nm platinum layer was formed on the quartz substrate by sputtering of platinum. The platinum layer was patterned into a working electrode and counter electrode design shown in FIG. 5 by the lift-off method to obtain a counter electrode.

Subsequently, similarly, a diamond-like carbon film having a thickness of 2.5 μm and an SP2 / SP3 value of 5.2 was formed by ion beam sputtering. The SP2 / SP3 value of the carbon film was determined by electron energy loss spectrometry.
In addition, a broad peak was observed near 1584 cm ⁻¹ by Raman scattering spectroscopy using a visible light laser. Therefore, it was confirmed that the carbon film has an amorphous structure.

Subsequently, a 22.5 w / v% albumin solution containing 100 mg / 100 μL (pure water) glucose oxidase and 1 v / v% glutaraldehyde was spin-coated and dried at 4 ° C. for 24 hours in a nitrogen atmosphere. To fix the enzyme.

Subsequently, each electrode and the flexible substrate were electrically connected by wire bonding and wired so that the current flowing through the working electrode could be measured. Here, waterproofing was applied to the portion connected by wire bonding. Thereby, an electrochemical sensor using the modified electrode of Example 3 was obtained.

The produced electrochemical sensor was immersed in a phosphate buffer at pH 6.5 in which 0.1 M KCl was dissolved, and 0.8 V vs. Amperometric measurement was performed under a potential condition of Ag / AgCl. When glucose, which is a substrate for glucose oxidase, was added to the solution to a concentration of 0.1 mM, an increase in oxidation current was observed. When the glucose concentration was further increased, the current value increased. On the other hand, even when fructose which is not a substrate for glucose oxidase was added to a concentration of 0.1 mM, the current value did not increase. It was confirmed that the modified electrode of Example 3 functions as an enzyme-modified electrode.
Example 4

The manufacturing method of the electrochemical sensor of Example 4 will be described.
First, a 4-inch quartz wafer was prepared, washed with acetone, and then washed with a solution containing the same amount of hydrogen peroxide and nitric acid.

Subsequently, a 300 nm platinum layer was formed on the quartz substrate by sputtering of platinum. By the lift-off method, the platinum layer was patterned into the working electrode and counter electrode design shown in FIG. 7 to obtain 48 counter electrodes.

Subsequently, similarly, a diamond-like carbon film having a thickness of 1 μm and an SP2 / SP3 value of 2.5 was formed by ion beam sputtering. The SP2 / SP3 value of the carbon film was determined by electron energy loss spectrometry.
In addition, a broad peak was observed near 1584 cm ⁻¹ by Raman scattering spectroscopy using a visible light laser. Therefore, it was confirmed that the carbon film has an amorphous structure.

Subsequently, 10 mg of carbon nanohorn was added to 10 mL of dichloroethane and dispersed with an ultrasonic cleaner for 5 minutes. Then, 5 mL of a dichloroethane solution containing carbon nanohorns was collected and dropped onto the substrate, and spin-coated under a rotation condition of 2000 rpm for 30 seconds. It was dried for 10 minutes in a nitrogen atmosphere at 100 ° C.

Subsequently, a photoresist pattern was formed on the substrate, and the carbon nanohorn layer and the carbon film were patterned into the working electrode design shown in FIG. 7 by etching using oxygen plasma to obtain 48 working electrodes.

Subsequently, a 300 nm silver layer was formed by silver sputtering, and a current of 0.8 mA was passed in a 0.1 M hydrochloric acid aqueous solution for 10 minutes to form silver / silver chloride. Then, 48 reference electrodes were obtained by patterning into the reference electrode design of FIG. 7 by the lift-off method.

Note that the 48 working electrodes, the counter electrode, and the reference electrode are arranged so as to form a set one by one. That is, the electrode pairs shown in FIG. 5 are arranged in 6 rows × 8 columns on the substrate.

Subsequently, 48 sets were separated by a dicing apparatus, and each set was electrically connected to the flexible substrate by wire bonding. The parts connected by wire bonding were waterproofed. As a result, 48 electrochemical sensors were obtained.

When the response characteristics of each electrode to ferrocenemethanol were evaluated, it was confirmed that the variation in the current value between the electrodes was within a certain range, and electrochemical measurement could be performed with high sensitivity. That is, it has been confirmed that there is no problem in cleaning even if a plurality of electrochemical sensors are formed on a single quartz wafer.

As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.
This application claims priority based on Japanese Patent Application No. 2008-178870 filed on Jul. 9, 2008, the entire disclosure of which is incorporated herein.

Claims

An insulating substrate;
A conductive layer provided on the insulating substrate;
A first carbon layer provided on the conductive layer;
A second carbon layer provided to cover the first carbon layer;
With
The first carbon layer includes carbon having an SP2 bond and an SP3 bond and having an amorphous structure;
The second carbon layer is a carbon electrode containing carbon having an SP2 bond.
The carbon electrode according to claim 1, wherein the first carbon layer has an SP2 bond to SP3 bond ratio (SP2 / SP3 value) of 0.01 or more and 100.0 or less.
The carbon electrode according to claim 2, wherein the SP2 / SP3 value is 0.1 or more and 10.0 or less.
The carbon electrode according to any one of claims 1 to 3, wherein the first carbon layer includes diamond-like carbon or amorphous carbon.
The carbon electrode according to any one of claims 1 to 4, wherein the second carbon layer includes powdered carbon having a nanostructure.
The powdery carbon having the nanostructure is selected from graphite, amorphous carbon, diamond-like carbon, carbon fiber, carbon black, acetylene black, ketjen black (registered trademark), carbon nanotube, carbon nanohorn, and carbon nanofiber. The carbon electrode according to claim 5, comprising at least one selected from the group consisting of:
The carbon electrode according to claim 6, wherein the powdered carbon having a nanostructure includes a carbon nanotube or a carbon nanohorn.
The carbon electrode according to any one of claims 1 to 7, wherein the SP2 / SP3 value of the first carbon layer is maximized in the vicinity of an interface between the first carbon layer and the second carbon layer.
The carbon electrode according to any one of claims 1 to 8, wherein the first carbon layer further includes at least one third carbon layer having an SP2 / SP3 value different from that of the first carbon layer.
The first carbon layer and the second carbon layer are in contact with each other, and the SP2 / SP3 value of the first carbon layer is higher than the SP2 / SP3 value of the third carbon layer. Carbon electrode.
The carbon electrode according to any one of claims 1 to 10, further comprising an intermediate layer including at least one selected from Cr, Ti, and W between the conductive layer and the first carbon layer.
The carbon electrode according to claim 11, wherein the composition of the conductive layer and the intermediate layer is mixed in the vicinity of the interface between the conductive layer and the intermediate layer.
The carbon electrode according to claim 11 or 12, wherein the composition of the intermediate layer and the first carbon layer is mixed in the vicinity of the interface between the intermediate layer and the first carbon layer.
The carbon electrode according to any one of claims 1 to 13, wherein the second carbon layer carries a modifier.
The modified substance includes at least one selected from a catalyst, an enzyme, a metal complex, an electron transfer mediator, an antibody, a nucleic acid, a receptor, a protein, a lipid, a polymer, a cell, a microorganism, and a living tissue. The described carbon electrode.
A carbon electrode according to any one of claims 1 to 15,
A reference pole;
An electrochemical sensor comprising:
The electrochemical sensor according to claim 16, further comprising a counter electrode.
The electrochemical sensor further includes a measurement unit and a conducting wire,
The measurement unit and the carbon electrode are electrically connected by the conductive wire,
The conducting wire penetrates the first carbon layer and is in electrical contact with the conductive layer;
The surface of the conducting wire is covered with an insulating film,
The electrochemical sensor according to claim 16 or 17, wherein surfaces of the insulating film and the first carbon layer are covered with a sealing material.
The electrochemical sensor according to claim 18, wherein a tip end of the conducting wire is tapered.
The conducting wire has a barbed structure at least at a part of its end,
The electrochemical sensor according to claim 18, wherein the barb structure is embedded in the conductive layer.
The electrochemical sensor according to any one of claims 18 to 20, wherein a leading end of the conducting wire penetrates the first carbon layer and the conductive layer and is inserted into the insulating substrate.
Forming a conductive layer on an insulating substrate;
Forming a first carbon layer on the upper surface of the conductive layer;
Forming a second carbon layer so as to cover the first carbon layer;
The manufacturing method of the carbon electrode in any one of Claim 1 to 15 containing.
After the step of forming the conductive layer, patterning the conductive layer to form a plurality of conductive layers;
The method for producing a carbon electrode according to claim 22, further comprising a step of dividing the plurality of carbon electrodes after the step of forming the second carbon layer.