JP2018105805A - Sensor electrode - Google Patents

Abstract

An electrode for a sensor that can be easily formed and functions stably as a sensor is provided. A first electrode layer 4 is provided on one surface of a base material 1 having insulating properties, the first electrode layer includes a working electrode 21 and a standard electrode 22, and the first electrode layer includes the first electrode layer described above. A first layer 2 containing palladium is provided on one surface of the substrate, and the standard electrode functions as a standard electrode on the surface of the first layer opposite to the surface on which the substrate is formed. An electrode for a sensor comprising the second layer 3 containing gold formed so as to exhibit the following. [Selection] Figure 2

Description

  The present invention relates to an electrode for a sensor that can be easily formed and functions stably as a sensor.

Biosensors using electrochemical detection means have been put into practical use as a method for quickly and easily measuring the concentration and the like of a specific component in a biological sample such as blood.
In general, an electrochemical biosensor using an enzyme as a sensing element includes an electrode system including a working electrode and a counter electrode as electrodes, and a reaction unit including an enzyme and an electron carrier (mediator). An example of such a biosensor is a glucose sensor that electrochemically quantifies glucose in blood.

For example, in a glucose sensor, an enzyme selectively oxidizes glucose in blood to produce gluconic acid in the reaction part, and simultaneously reduces an electron carrier to produce a reduced form. The reductant is transmitted to the electrode system, and the reductant is oxidized again by applying a certain voltage, and current is generated at that time.
Since the magnitude of the current generated at this time depends on the glucose concentration in the blood, the glucose in the blood can be quantified from the current value measured by the measuring device connected to the biosensor.

Biosensors typified by glucose sensors and the like are required to have high sensitivity and measurement accuracy in order to enable measurement in a short time from a small amount of sample. On the other hand, since biosensors are consumables that are used after being exchanged for each test, they are also required to be low in cost.
In order to obtain a highly sensitive and inexpensive biosensor, a metal material having high conductivity such as silver and nickel has been conventionally used as a material for the electrode system and the wiring portion (see Patent Document 1).
However, the electrode made of such a metal material has the electrical characteristics of the biosensor deteriorated due to corrosion due to contact with moisture in the atmosphere, moisture in the sample, hydrogen peroxide generated by the enzyme reaction of the sample and the enzyme, There exists a problem that the precision as a sensor falls.

  In addition, as a material for the electrode, for example, a method using carbon is known (Patent Document 2). Carbon is less likely to corrode than the metal materials described above and is less expensive than metal materials. However, carbon does not have an inexpensive technique for processing into a flat and precise pattern shape, and there is a problem that it is difficult to mass-produce electrodes that can be used as a highly accurate sensor.

For this reason, as an electrode material used for a biosensor, a material using a non-corrosive noble metal material such as gold is generally used.
In addition, as described in Patent Document 3, after forming a non-corrosive noble metal material film such as gold by a vapor deposition method, a noble metal material film other than the electrode is formed by a photolithography method or the like. The removal method is used.
Such electrodes are used not only for biosensors but also for various measurement sensors such as gas sensors and biological substance detection sensors, SAW (surface acoustic wave) filters, biofuel cell electrodes, and the like. .

JP 2006-023291 A JP 2004-294231 A JP 2010-229135 A

However, when a working electrode or the like is formed using a gold electrode, there is a problem that the material itself is expensive and the sensor electrode is expensive.
In addition, when a working electrode or the like is formed using a gold electrode, it is necessary to separately form a silver / silver oxide electrode or the like as a standard electrode, which causes a problem that the manufacturing process becomes complicated and the cost is increased.
In order to solve such a problem, the present inventors are considering forming an electrode using palladium. Palladium is less expensive than gold, and the electrode using it is one of the few materials that can be used as a standard electrode. For this reason, when a working electrode or the like is formed using a palladium electrode, it is not necessary to separately form a standard electrode using a different material as in the case where a gold electrode is used. That is, if it is a palladium electrode, a standard electrode and a working electrode can be formed simultaneously, and the effort which forms a standard electrode separately using another material can be saved. For this reason, it becomes possible to achieve significant cost reduction by forming the electrode using a palladium electrode.
However, when both the standard electrode and the working electrode are formed of palladium electrodes, there is a problem that they may not function as a sensor.

  The present invention has been made in view of the above problems, and it is a main object of the present invention to provide a sensor electrode that can be easily formed and functions stably as a sensor.

As a result of repeated studies to solve the above problems, the present inventors, as a result of forming a working electrode using a palladium electrode, components such as proteins (hereinafter referred to as adsorptive components) in a sample containing a measurement object. It has been discovered that the sensor electrode may not function as a sensor by adsorbing to the surface of the working electrode and inhibiting the electrochemical reaction on the surface of the working electrode.
In addition, the electrode layer with a thin gold electrode film on the palladium electrode surface can suppress the adsorption of adsorptive components to the surface of the working electrode when it is used to form a working electrode and a standard electrode. The present invention has been completed by newly finding out that it also functions as a standard electrode.

That is, the present invention has a first electrode layer on one surface of an insulating substrate, the first electrode layer includes a working electrode and a standard electrode, and the first electrode layer includes the substrate. Having a first layer containing palladium on one side (hereinafter sometimes referred to as a palladium layer), and on the surface of the first layer opposite to the surface on which the substrate is formed, There is provided a sensor electrode characterized in that the standard electrode has a second layer (hereinafter sometimes referred to as a gold layer) containing gold formed so as to function as a standard electrode.
That is, the present invention has a base material having insulating properties and a first electrode layer formed on one surface of the base material, and the first electrode layer includes a working electrode and a standard electrode, The first electrode layer includes a palladium layer formed on one surface of the substrate, and a surface of the palladium layer opposite to the surface on which the substrate is formed. There is provided a sensor electrode comprising a gold layer formed so as to exhibit a function.

According to the present invention, the first electrode layer includes the palladium layer and the gold layer on the surface of the palladium layer opposite to the surface on which the base material is formed. The working electrode formed using the layer can suppress the adsorption of the adsorptive component during use. For this reason, the electrode for sensors of the present invention functions stably as a sensor.
The first electrode layer is formed of a gold layer so that the standard electrode functions as a standard electrode, so that the standard electrode formed using the first electrode layer is a standard electrode. As a result,
Therefore, the first electrode layer can be used as both a working electrode and a standard electrode, and both the working electrode and the standard electrode are formed by such a first electrode layer. This makes it easy to form electrodes.

  In the present invention, the thickness of the second layer is preferably 5 nm or more and 50 nm or less. That is, in the present invention, the gold layer preferably has a thickness of 5 nm to 50 nm. This is because it is easy to form the first electrode layer that functions as a standard electrode.

  In the present invention, the thickness of the first layer is preferably thicker than the thickness of the second layer. That is, in the present invention, it is preferable that the palladium layer is thicker than the gold layer. This is because the amount of gold layer used, that is, the amount of gold used can be reduced, and the sensor electrode of the present invention is low-cost.

  In this invention, it has an electrode layer containing the said 1st layer in one surface of the said base material, and it is preferable that all the said electrode layers are said 1st electrode layers. That is, in the present invention, it is preferable that all of the electrode layers formed on one surface of the substrate and including the palladium layer are the first electrode layer. This is because all the electrodes formed by the electrode layer are formed by the first electrode layer, whereby the sensor electrode of the present invention can be easily formed.

In the present invention, the object to be measured can be accommodated on one surface of the base material, and a housing part in which the working electrode and the standard electrode are disposed, and one end connected to the housing part And a flow path having the other end connected to the inlet. That is, in the present invention, it is formed on one surface of the base material and can accommodate a measurement object, and a housing portion in which the working electrode and the standard electrode are disposed, and one end of the housing It is preferable to have a flow path that is connected to the accommodating portion and has the other end connected to the introduction port.
This is because the sensor electrode of the present invention can be easily used as a sensor by having the housing portion and the flow path.

  In the present invention, the working electrode preferably has a comb shape in plan view. This is because the sensor electrode of the present invention is a highly sensitive sensor because the working electrode has a comb shape in plan view.

  In the present invention, the sensor electrode is preferably used as an endotoxin sensor. This is because the sensor electrode of the present invention is low in cost, and therefore, for example, it is possible to measure endotoxin concentration measured in various situations at low cost.

  The present invention is advantageous in that an electrode can be easily formed and a sensor electrode that functions stably as a sensor can be provided.

It is a schematic plan view which shows an example of the electrode for sensors of this invention. It is the sectional view on the AA line of FIG. It is explanatory drawing explaining the electrode layer in this invention. It is explanatory drawing explaining the electrode layer in this invention. It is the schematic plan view and sectional drawing which show the other example of the electrode for sensors of this invention. It is the schematic plan view and sectional drawing which show the other example of the electrode for sensors of this invention. 2 is a cyclic voltammogram in Example 1. FIG. 4 is a cyclic voltammogram in Example 2. 4 is a cyclic voltammogram in Example 3. 6 is a cyclic voltammogram in Example 4. 6 is a cyclic voltammogram in Example 5. 7 is a cyclic voltammogram in Example 6. 2 is a cyclic voltammogram in Comparative Example 1. 4 is a cyclic voltammogram in Comparative Example 2. 10 is a cyclic voltammogram in Comparative Example 3. 10 is a cyclic voltammogram in Comparative Example 4. 10 is a cyclic voltammogram in Comparative Example 5. 10 is a cyclic voltammogram in Comparative Example 6. 2 is a cyclic voltammogram in Reference Example 1. 2 is an amperogram in Example 1. FIG. 10 is an amperogram in Example 7.

The present invention relates to a sensor electrode.
Hereinafter, the sensor electrode of the present invention will be described in detail.

  The sensor electrode of the present invention has a base material having an insulating property and a first electrode layer formed on one surface of the base material, and the first electrode layer includes a working electrode and a standard electrode. The first electrode layer includes a palladium layer formed on one surface of the substrate and a surface of the palladium layer opposite to the surface on which the substrate is formed. And a gold layer formed so as to perform the function as.

Such a sensor electrode of the present invention will be described with reference to the drawings. FIG. 1 is a schematic plan view showing an example of a sensor electrode of the present invention, and FIG. 2 is a cross-sectional view taken along line AA of FIG.
As illustrated in FIGS. 1 and 2, the sensor electrode 10 of the present invention includes a base material 1 having an insulating property and a first electrode layer 4 formed on one surface of the base material 1. The first electrode layer 4 includes a working electrode 21 and a standard electrode 22, and the first electrode layer 4 includes a palladium layer 2 formed on one surface of the substrate 1, and a palladium layer 2. The gold layer 3 is formed on the surface opposite to the surface on which the base material 1 is formed so that the standard electrode 22 functions as a standard electrode.
1 and FIG. 2, the electrode layer 6 including the palladium layer 2 formed on one surface of the substrate 1 includes an electrode portion 11 including two working electrodes 21, a standard electrode 22, and a counter electrode 23. And an electrode having a terminal part 13 connected to the electrode part 11 and used for connection to the measuring device, and a wiring part 12 connecting the electrode part 11 and the terminal part 13, all of these electrodes being the first An example in which the electrode layer 4 is formed, that is, an example in which the electrode layer 6 including the palladium layer 2 is the first electrode layer 4 is shown.

According to the present invention, the first electrode layer includes the palladium layer and the gold layer on the surface of the palladium layer opposite to the surface on which the base material is formed. The working electrode formed using the layer can suppress the adsorption of the adsorptive component during use due to the presence of the gold layer, and can suppress the inhibition of the electrochemical reaction by the adsorbing component. For this reason, the electrode for sensors of the present invention functions stably as a sensor.
In addition, the first electrode layer is formed such that the gold layer is formed so that the standard electrode functions as a standard electrode, for example, a sample including an object to be measured can be brought into contact with the palladium layer. Thus, the function as a palladium layer can be exhibited. As a result, the standard electrode formed using the first electrode layer functions as a standard electrode.
Therefore, the first electrode layer can be used as both a working electrode and a standard electrode, and both the working electrode and the standard electrode are formed by such a first electrode layer. This makes it easy to form electrodes.
Furthermore, since the first electrode layer includes a palladium layer, the cost can be reduced as compared with the case where the electrode is formed only by the gold layer.

The sensor electrode of the present invention has a substrate and an electrode layer.
Hereafter, each structure of the electrode for sensors of this invention is demonstrated in detail.

1. Electrode layer The electrode layer includes a palladium layer formed on one surface of the substrate.
The electrode layer includes at least a first electrode layer.

(1) First electrode layer The first electrode layer includes at least a working electrode and a standard electrode.
The first electrode layer includes a palladium layer formed on one surface of the substrate, and a surface of the palladium layer opposite to the surface on which the substrate is formed. And a gold layer formed so as to exhibit a function.

Here, the standard electrode is formed so as to function as a standard electrode. The surface of the palladium layer opposite to the surface on which the base material is formed (hereinafter sometimes referred to as a palladium layer surface). Even if a gold layer is formed on the sensor electrode of the present invention, the standard electrode formed using the first electrode layer in the sensor electrode of the present invention may be any one that can exhibit the function as the standard electrode.
More specifically, the standard electrode is formed so as to function as a standard electrode. More specifically, a cyclic voltammogram is created under the conditions described in the evaluation 1 of the embodiment described later, and oxidation is performed from the cyclic voltammogram. Both peaks and reduction peaks can be observed.
Specifically, it can be determined that the oxidation peak was observed when the oxidation peak position was observed at 0.3 V or less.
Further, when a straight line parallel to the X axis passes through the reduction peak observed in the cyclic voltammogram, the characteristic after the reduction peak is higher than that line, that is, the potential is changed from 0.6 V to −0. When scanning at .4 V, when a current value equal to or higher than the current value at the reduction peak is observed on the lower potential side than the potential at which the reduction peak was observed, it can be determined that the reduction peak could be observed.
As such a 1st electrode layer, it has the gold layer formed in the palladium layer surface in the state in which the sample (henceforth a sample may only be called a sample) containing a measuring object can reach a palladium layer, for example. More specifically, an embodiment (first embodiment) having a gold layer having a thickness of 50 nm or less and a gold layer having a pattern shape in which the palladium layer is partially exposed in plan view. And an embodiment (second embodiment) having
In the present invention, in particular, the first electrode layer is preferably the first embodiment. This is because the formation of the gold layer is easy.
3A is a schematic plan view showing an example of the first electrode layer 4 having the gold layer 3 having a thickness of 50 nm or less, and FIG. 3B is a cross-sectional view taken along line BB in FIG. It is line sectional drawing.
4A, 4 </ b> C, and 4 </ b> E schematically illustrate an example of the first electrode layer 4 having a gold layer 3 having a pattern shape in which the palladium layer 2 is partially exposed in plan view. FIGS. 4B, 4D, and 4F are cross-sectional views taken along the line CC of FIGS. 4A, 4C, and 4E, respectively.
Hereinafter, the first electrode layer of each of such embodiments will be described separately.

(A) 1st embodiment The 1st electrode layer of this aspect has a gold layer whose thickness is 50 nm or less.

Here, it is not clear why the standard electrode formed using the first electrode layer has a function as a standard electrode by having a gold layer having a thickness of 50 nm or less. It is guessed as follows.
That is, the gold layer generally has pinholes and the like, and the thinner the film, the greater the number of pinholes. For this reason, when the thickness of the gold layer is equal to or less than a predetermined range, the sample can reach the palladium layer. As a result, the first electrode layer functions as a standard electrode.
Further, since the palladium layer is covered with the gold layer, the adsorption of the adsorptive component can be suppressed. As a result, the first electrode layer functions stably as a working electrode.
Furthermore, cost reduction can be achieved because thickness is 50 nm or less.

The thickness of the gold layer may be 50 nm or less, and varies depending on the application of the sensor electrode of the present invention. For example, the thickness is preferably 5 nm or more and 50 nm or less, and preferably 5 nm or more and 30 nm or less. In particular, it is preferably 5 nm or more and 20 nm or less, and particularly preferably 5 nm or more and 15 nm or less.
This is because when the thickness of the gold layer is within the above range, the sample can stably reach the palladium layer, and further, the adsorption of the adsorptive component to the palladium layer can be stably suppressed.
The thickness of the gold layer refers to the distance from the surface of the palladium layer opposite to the surface on which the substrate is formed to the surface on the opposite side of the surface of the gold layer on which the palladium layer is formed. Specifically, it is indicated by h1 in FIG. 3 (b) already described.

  Hereinafter, the gold layer and the palladium layer included in the first electrode layer of this embodiment will be described.

(I) Gold layer The gold layer is formed on the surface of the palladium layer opposite to the surface on which the substrate is formed so that the first electrode layer functions as the standard electrode. In this embodiment, the thickness is 50 nm or less.
The gold layer is a layer containing gold as a main component.

Here, including gold as a main component is sufficient if the first electrode layer stably functions as a working electrode and a standard electrode. For example, the gold content in the gold layer is 95 mass. %, More preferably 98% by mass or more, and particularly preferably 100% by mass, that is, one containing only gold. This is because the first electrode layer stably functions as the working electrode and the standard electrode when the content is within the above-described range.
In addition, when the said content is less than 100 mass%, as a material which the said gold layer can contain, platinum etc. can be mentioned, for example.

  The place where the gold layer is formed on the surface of the palladium layer may be a pattern where the palladium layer is exposed, but is usually the entire surface of the surface of the palladium layer. This is because the formation of the first electrode layer is facilitated by the formation location.

  The gold layer may be formed on the surface of the palladium layer opposite to the surface on which the base material is formed, but may be formed on the side surface of the palladium layer as necessary. Good.

  The gold layer may be formed on the surface of the palladium layer opposite to the surface on which the base material is formed through another layer, but is usually formed so as to be in direct contact with the palladium layer. It is what is done.

(Ii) Palladium layer The palladium layer is formed on one surface of the substrate.
The palladium layer is a layer containing palladium as a main component.

Here, including palladium as a main component is not limited as long as the first electrode layer stably functions as a working electrode and a standard electrode. For example, the palladium content in the palladium layer is 95 mass%. %, More preferably 98% by mass or more, and particularly preferably 100% by mass, that is, one containing only palladium. This is because the first electrode layer stably functions as the working electrode and the standard electrode when the content is within the above-described range.
In addition, when the said content is less than 100 mass%, as a material which the said palladium layer can contain, gold | metal | money, nickel, chromium, carbon etc. can be mentioned, for example.

The thickness of the palladium layer is not particularly limited as long as the first electrode layer stably functions as a working electrode and a standard electrode. For example, the thickness can be 5 nm or more and 500 nm or less, and in particular, 10 nm or more and 100 nm or less. It is preferable that it is 30 nm or more and 50 nm or less especially. This is because, when the thickness is within the above range, the first electrode layer stably functions as the working electrode and the standard electrode.
The palladium layer is preferably thicker than the gold layer. This is because the sensor electrode of the present invention is low-cost.
The thickness of the palladium layer refers to the distance from the surface of the palladium layer on the substrate side to the surface on which the gold layer is formed. Specifically, h2 in FIG. 3 (b) already described. It is shown by.

(Iii) Forming method of first electrode layer The first electrode layer includes at least a working electrode and a standard electrode, and its planar view shape is usually a pattern shape.
As a method for forming such a first electrode layer, any method can be used as long as the first electrode layer having a desired pattern shape can be formed. For example, after forming a patterned palladium layer, a gold layer is formed on the palladium layer. A first layer, a palladium layer-forming film capable of forming a palladium layer, and a gold layer-forming film capable of forming a gold layer, and then a laminated body of the palladium layer-forming film and the gold layer-forming film. And the like (second method).
In the present invention, it is preferable that the formation method is the first method. This is because the amount of gold used for forming the gold layer can be reduced.

As a method of forming a patterned palladium layer, a method of forming a patterned resist after forming a palladium layer forming film and then etching the palladium layer forming film exposed from the resist can be used. In addition, as the above formation method, after forming a mask layer having an opening at the formation position of the first electrode layer, a method of forming a palladium layer formation film, or a palladium layer formed at the formation position of the first electrode layer After forming an adhesion layer that can be adhered to the substrate, a method of forming a palladium layer forming film formed using the constituent material of the palladium layer can be used.
Examples of the mask layer include a photoresist, a printing layer, a metal mask, and a water-based ink layer. Examples of the adhesion layer include a plating base.
As a method for laminating the gold layer on the patterned palladium layer, a plating method or the like can be used, and among them, an electroless plating method can be preferably used. As the electroless gold plating solution, for example, a non-cyanide electroless gold plating solution can be used.
Moreover, as a formation method of a palladium layer formation film and a gold layer formation film, what is necessary is just a method which can form the palladium layer formation film and gold layer formation film of desired thickness, and using a general film forming method is used. For example, known vapor deposition methods such as vacuum vapor deposition, physical vapor deposition methods such as sputtering, ion plating, etc., plating methods, etc., among others, vapor deposition methods. In particular, the physical vapor deposition method is preferable.
As a method for patterning the laminate, a method similar to the method for forming the patterned palladium layer can be used.
In addition, when the said formation method is a method of forming into a film after forming a mask layer etc., you may perform the process which removes an unnecessary palladium layer formation film with a mask layer as needed.

(B) Second Embodiment A second embodiment of the first electrode layer has a gold layer having a pattern shape in which the palladium layer is partially exposed in plan view.

In this aspect, since the plan view shape of the gold layer is a pattern shape in which the palladium layer is partially exposed, the sample can reach the palladium layer, so that the first electrode layer functions as a standard electrode. It will be a thing.
In addition, since the palladium layer is partially covered with the gold layer, adsorption of the adsorptive component can be suppressed. As a result, the first electrode layer can also stably function as a working electrode.

The shape of the gold layer in plan view may be a pattern shape in which the palladium layer is partially exposed, and may be a dot shape (halftone dot shape), a line shape, a shape in which a plurality of openings are arranged, or the like.
The shape of the dot-shaped gold layer in plan view is not particularly limited as long as the first electrode layer can function as a standard electrode. For example, a polygonal shape such as a triangular shape, a quadrangular shape, a pentagonal shape, a circular shape, etc. The shape may be an ellipse or the like.
The shape of the opening can be the same as the shape of the dot-shaped gold layer in plan view.
4A, 4C, and 4E described above show examples in which the planar view shape is a line shape, a dot shape, and a shape in which a plurality of openings are arranged, respectively. is there.
Moreover, FIG.4 (c) and FIG.4 (e) show the example whose planar view shape of a dot shape and an opening part is a square shape, respectively.

The covering ratio of the gold layer, that is, the ratio of the area covered by the gold layer (gold layer area) to the area of the palladium layer opposite to the surface on which the substrate is formed (palladium layer area) (gold The layer area / palladium layer area) may be less than 1 and varies depending on the application of the sensor electrode of the present invention, and may be, for example, 0.50 or more and 0.99 or less. However, it is preferably 0.60 or more and 0.95 or less, and particularly preferably 0.80 or more and 0.95 or less. This is because the first electrode layer stably functions as the working electrode and the standard electrode when the covering ratio is in the above-described range.
The covering ratio is, for example, that, for an electrode formed by the first electrode layer, a square region having at least one side of 10 μm or more is disposed so as to maximize the overlap in a plan view, and the square region and the plan view are arranged. It is possible to obtain the covering ratio at the overlapping portion.

Hereinafter, the gold layer and the palladium layer included in the first electrode layer of this embodiment will be described.
The palladium layer can be the same as that described in the section “(a) First embodiment”, and the description thereof is omitted here.

(I) Gold layer The gold layer is formed on the surface of the palladium layer opposite to the surface on which the base material is formed so that the first electrode layer functions as the standard electrode. In this embodiment, the plan view shape is a pattern shape in which the palladium layer is partially exposed.

  The thickness of the gold layer is not particularly limited as long as the first electrode layer stably functions as a working electrode and a standard electrode. For example, the thickness can be 5 nm or more and 50 nm or less. Is preferably 10 nm or more and 30 nm or less in particular. This is because a gold layer having a predetermined pattern shape can be stably formed when the thickness is within the above range. In addition, the cost can be reduced.

  About the other content of the said gold layer, since it can be made to be the same as that of the content of the term of the said "(a) 1st embodiment", description here is abbreviate | omitted.

(Ii) Method for Forming First Electrode Layer The first electrode layer includes at least a working electrode and a standard electrode, and its planar view shape is usually a pattern shape.
In the first electrode layer of this aspect, the gold layer is formed in a pattern in which the palladium layer is exposed.
As a method for forming such a first electrode layer, any method can be used as long as the first electrode layer having a desired pattern shape can be formed. For example, after forming a patterned palladium layer, a pattern shape is formed on the palladium layer. And a method of forming a gold layer.
The method for forming the gold layer in a pattern and the method for forming the palladium layer in a pattern are the same as the method for forming the palladium layer in the pattern described in the section “(a) First embodiment” above. can do.

(C) Other layers The first electrode layer has a structure in which a palladium layer and a gold layer are laminated in this order from the base material side, and has a layer other than the palladium layer and the gold layer. However, it is preferable that the first electrode layer includes only a palladium layer and a gold layer, and is formed so that the palladium layer is in direct contact with the substrate. This is because the sensor electrode of the present invention is low in cost because it is the first electrode layer having the above layer structure.
The other layer may be any layer having conductivity, and is formed between a palladium layer such as a Ti layer, a Cr layer, or a Ni layer and a base material, and the adhesion of the first electrode layer to the base material is improved. Examples include an improved adhesion improving layer.
In addition, about the plating base layer used when forming a palladium layer by a plating method, it is not contained in the said adhesive improvement layer.

(2) Target for forming first electrode layer The first electrode layer includes at least a working electrode and a standard electrode.
Here, the phrase “the first electrode layer includes a working electrode and a standard electrode” means that the working electrode and the standard electrode are formed of the first electrode layer.
In the present invention, the first electrode layer only needs to include a part that can contact the sample of the working electrode and the standard electrode. For example, the first electrode layer may include only a part of each of the working electrode and the standard electrode. It is preferable to include all the parts of the standard electrode that can come into contact with the sample, and in particular, to include both the working electrode and the standard electrode, that is, the working electrode and the standard electrode are all the first electrode layer. Is preferred.
FIG. 1 and FIG. 2 already described show examples in which the first electrode layer includes all of the working electrode and the standard electrode.
FIG. 5 shows an example in which the first electrode layer includes only a part of each of the working electrode and the standard electrode, and shows an example including only a part that can contact each sample. FIG. 5 (a) is a schematic plan view showing another example of the sensor electrode 10 of the present invention, and FIGS. 5 (b) and 5 (c) are cross-sectional views taken along the line DD of FIG. 5 (a), respectively. It is EE sectional view taken on the line.
FIG. 5 shows an example in which the first electrode layer includes all the parts that can contact the working electrode and the standard electrode sample.

(A) Working electrode The working electrode is an object to be measured by an electric current that flows as a result of an electrochemical reaction with the redox substance contained in the sample and oxidation of the redox substance and oxidation of the redox substance. It detects objects.

The shape of the working electrode in plan view is not particularly limited as long as it can cause an electrochemical reaction with a redox substance, and can be the same as that of a general sensor electrode.
In this invention, it is preferable that the said planar view shape is a comb shape which has at least 2 or more comb-tooth part and the connection part which connects these comb-tooth parts. When the planar view shape is a comb shape, the working electrode can easily have a large contact area with the sample. Therefore, the sensor electrode of the present invention can be used as a highly accurate sensor.
Further, by being in the comb shape, for example, two comb-shaped working electrodes are arranged so that the comb teeth portions are adjacent in the width direction, that is, the comb teeth portions are engaged with each other, thereby The electrode can efficiently amplify the detected current value. This is because the sensor electrode of the present invention can be used as a highly accurate sensor.
Note that FIG. 1 already described shows an example in which the working electrode 21 has a comb shape having at least two or more comb teeth portions 14a and a connecting portion 14b that connects these comb teeth portions 14a. .

The width of the comb portion is not particularly limited as long as it can be a sensor with a desired accuracy, but it is preferably 0.1 μm or more and 20 μm or less, and in particular, 0.1 μm. It is preferably 10 μm or less.
The length of the comb tooth portion varies depending on the application of the sensor electrode of the present invention, and can be 500 μm or more and 10,000 μm or less.
The number of the comb-tooth portions varies depending on the application of the sensor electrode of the present invention, and can be 50 or more and 500 or less.
The width between the adjacent comb tooth portions varies depending on the application of the sensor electrode of the present invention, but can be 0.1 μm or more and 60 μm or less.
The width of the connecting portion varies depending on the application of the sensor electrode of the present invention, but can be 0.1 μm or more and 10,000 μm or less.
In addition, the width | variety of the said comb-tooth part, length, the width | variety between the said adjacent comb-tooth parts, and the width | variety of the said connection part are specifically shown by a, b, c, d in FIG. It is. FIG. 1 already described shows an example in which the number of comb teeth per comb electrode is four.

The number of working electrodes may be one or more, and is appropriately set according to the use of the sensor electrode of the present invention.
When the number of working electrodes is two, that is, when the first working electrode and the second working electrode are provided as working electrodes, the first working electrode and the second working electrode are reduced forms of redox substances, respectively. It can be used as an electrode for oxidizing and an electrode for reducing an oxidized form of the redox substance.
Since the first working electrode and the second working electrode are arranged close to each other, the oxidation and reduction of the redox substance can be repeated with high frequency, and the sensor electrode of the present invention can be used as a highly accurate sensor. Become.

(B) Standard electrode The standard electrode is a reference electrode when determining the potential of the working electrode.

  The planar view shape of the standard electrode can be the same as that generally used for electrochemical sensors.

The distance between the working electrode of the standard electrode may be a distance that does not cause a short circuit.
Such a distance between the electrodes can be appropriately set according to the size of the sensor electrode of the present invention.

(C) Others The first electrode layer includes at least a working electrode and a standard electrode among electrodes formed by the electrode layer.
In the present invention, a part of the electrodes formed by the electrode layer is formed by the first electrode layer, that is, only a part of the palladium layer included in the electrode layer is covered by the gold layer. However, all the electrodes formed by the electrode layer are formed by the first electrode layer, that is, all the palladium layers contained in the electrode layer are covered with the gold layer, It is preferable that all of the electrode layers including the palladium layer formed on the first electrode layer are first electrode layers. This is because all the electrodes formed by the electrode layer are formed by the first electrode layer, whereby the sensor electrode of the present invention can be easily formed.
1 and 2 described above are examples in which all the electrode layers 6 are the first electrode layers 4, that is, examples in which all the electrodes formed by the electrode layers 6 are formed by the first electrode layers 4. It is shown.
FIG. 5 described above is an example in which a part of the electrode layer 6 is the first electrode layer 4, that is, an example in which a part of the electrode formed by the electrode layer 6 is formed by the first electrode layer 4. It is shown.

  In the present invention, among the electrodes formed by the electrode layer, the other electrodes other than the working electrode and the standard electrode are connected to the electrode portion and the electrode portion other than the working electrode and the standard electrode, and are used for connection to the measuring device. The terminal part, the electrode part, the wiring part which connects the terminal part, etc. can be mentioned.

(I) Electrode part The said electrode part is an electrode which produces an electrochemical reaction in contact with a sample. As such an electrode part, you may have a counter electrode other than the working electrode and standard electrode which were already demonstrated, for example.
Here, the counter electrode is an electrode used to prevent the electrochemical reaction at the working electrode from stagnation due to the influence of the principle of electrical neutrality.
The counter electrode may be one in which the standard electrode also functions. Further, when the standard electrode is a common electrode that also functions as a counter electrode, as a method for connecting the common electrode and the measuring device, a method of connecting the common electrode to both the standard electrode terminal and the counter electrode terminal of the measuring device. Can be used.

  The shape of the counter electrode in plan view can be the same as that generally used for electrochemical sensors.

The distance between the counter electrode and the working electrode may be a distance that does not cause a short circuit.
Such a distance between the electrodes can be appropriately set according to the size of the sensor electrode of the present invention.

(Ii) Terminal part and wiring part The said terminal part is connected to the said electrode part, and is used for a connection with a measuring apparatus.
Moreover, the said wiring part connects an electrode part and a terminal part.
The measuring device to which the terminal portion is connected varies depending on the application of the sensor electrode of the present invention, but a device generally used for electrochemical measurement can be used, for example, a potentiostat, a current amplifier, Devices having functions equivalent to these can be mentioned. These devices can include, for example, a device including a connection electrode for receiving an electrical signal generated by the sensor electrode, a calculation unit, a power source, a display unit, and an operation unit.
About the planar view shape of the said terminal part and the said wiring part, it can be made to be the same as that used for a general wiring board.
For example, the shape of the terminal portion in plan view may be a circular shape, a rectangular shape, a polygonal shape such as a square shape, a circular shape, or the like. In addition, the wiring portion can have a line shape or the like.

(3) Others The electrode layer has at least a first electrode layer, but may have a second electrode layer as necessary. As such a 2nd electrode layer, what contains the said palladium layer formed in one surface of the said base material should just be included. For example, as illustrated in FIG. 5, the second electrode layer 5 has a palladium layer 2 and does not have a gold layer, that is, the surface of the palladium layer 2 on which the substrate 1 is formed. A material in which the gold layer 3 is not formed on the opposite surface can be used as the second electrode layer 5.
About the palladium layer contained in the 2nd electrode layer in this invention, it can be made to be the same as that of the content as described in the term of said (1) 1st electrode layer.
FIG. 5A shows an example in which the electrode layer 6 includes the first electrode layer 4 and the second electrode layer 5. The second electrode layer 5 is an example in which the surface opposite to the surface on which the substrate 1 is formed is covered with the insulating layer 24.
In FIG. 5, only the portion of the electrode portion 11 including the comb-shaped working electrode 21, standard electrode 22, and counter electrode 23 that is not covered by the insulating layer 24 is formed by the first electrode layer 4. The portion covered with is formed by the second electrode layer 5. In FIG. 5, only the portion of the wiring portion 12 that is not covered by the insulating layer 24 is formed by the first electrode layer 4, and the portion that is covered by the insulating layer 24 is formed by the second electrode layer 5. It is. In FIG. 5, all of the terminal portions 13 are formed by the first electrode layer 4.
FIG. 5 shows an example in which all the parts of the electrode portion 11 that can contact the sample of the working electrode 21, the standard electrode 22, and the counter electrode 23 are formed by the first electrode layer 4.

When the electrode layer has a first electrode layer and a second electrode layer, the electrode layer is formed by first forming a palladium layer in a pattern and then forming a gold layer only on the surface of the palladium layer used as the first electrode layer. For example, after forming an electrode layer in a pattern using a palladium layer, a portion where the second electrode layer is formed is covered with a resist layer, and the surface of the palladium layer exposed from the resist layer is covered. By forming the gold layer, a method in which a part of the electrode layer is the first electrode layer and the rest is the second electrode layer can be mentioned.
Further, the resist layer after the gold layer is formed may be peeled off after the gold layer is formed, or may be used as the configuration of the sensor electrode of the present invention as an insulating layer without being removed.

2. Base material The base material has an insulating property and supports the electrode layer.

Here, having an insulating property is not limited as long as it is possible to prevent a short circuit between a working electrode and a standard electrode provided on the surface of the base material. The volume resistance value of the substrate can be, for example, 1 × 10 ¹² Ω · m or more. In addition, the said volume resistance value can be calculated | required with the measuring method according to JISK9611.
As such a base material, for example, a resin base material, paper, a ceramic base material, a glass base material, a semiconductor base material or a metal base material having at least a surface insulation can be used. The substrate may have rigidity or elasticity. Among them, the substrate preferably has elasticity, for example, polyethylene terephthalate (PET) resin, vinyl chloride resin, polystyrene (PS) resin, polypropylene (PP) resin, polycarbonate (PC), polyethylene naphthalate (PEN). A film such as polyphenylene sulfide resin (PPS) can be suitably used.
Note that the substrate may or may not have flexibility. Moreover, the presence or absence of transparency of a base material is not ask | required.

  The shape, size, thickness, and the like of the substrate can be appropriately set depending on the shape of the connecting portion of the measuring instrument that uses the sensor electrode of the present invention.

3. Others The electrode for a sensor of the present invention has a substrate and an electrode layer, but may have other configurations as necessary.
As such other configuration, for example, as illustrated in FIG. 6, it is formed on one surface of the base material 1 and can accommodate the measurement object, and the working electrode 21 and the inside thereof can be accommodated therein. An accommodation portion 28 in which the standard electrode 22 is disposed, a flow path 29 formed on one surface of the base material, one end connected to the accommodation portion 28 and the other end connected to the introduction port 30, and the introduction port 30. A reaction part 27 containing an enzyme, a cover layer 26 arranged on the substrate 1, an insulating layer 24 formed so as to cover the wiring part 12, and the like. .
6A is a schematic plan view showing another example of the sensor electrode of the present invention, and FIG. 6B is a diagram in which the cover layer is omitted from FIG. 6A. FIG.6 (c) is the FF sectional view taken on the line of Fig.6 (a).

(1) Storage part The storage part in this invention is formed on a board | substrate, and can accommodate a measuring object, The said working electrode and the said standard electrode are arrange | positioned in the inside, Usually these All electrode parts including these electrodes are arranged.
The shape of the accommodating portion is not particularly limited, and examples of the shape of the accommodating portion in plan view include a circular shape, an elliptical shape, and a rectangular shape.
In the sensor electrode of the present invention, since the sample can be measured by introducing about several μL to several tens of μL, the capacity of the accommodating portion is preferably 1 mm ³ or more and 200 mm ³ or less, particularly 1 mm. It is preferably ³ or more and 100 mm ³ or less, particularly 1 mm ³ or more and 50 mm ³ or less. For example, when the shape of the housing portion is circular, the housing portion may have a diameter of about 1 mm to 5 mm and a depth of about 1 mm to 10 mm.

The arrangement of the accommodation part is not particularly limited as long as the measurement object can be accommodated and the electrode part can be arranged inside the measurement object. For example, as shown in FIG. 5, the accommodating part 28 may be arrange | positioned so that an upper part may become the inlet 30, and the accommodating part 28 may be arrange | positioned connected to the flow path 29 as shown in FIG. .
The number of accommodating parts may be one or plural.

  The housing portion may be formed by a groove in the base material, and as shown in FIG. 5 which has already been described, the cover layer 26 having an opening in the shape of the housing portion 28 on the base material 1 or already described. As shown in FIG. 6, it may be formed by disposing a spacer 25 having an opening in the shape of the accommodating portion 28 on the base material 1.

(2) Flow path The sensor electrode of the present invention may have a flow path having one end connected to the housing portion and the other end connected to the inlet.
The flow path may be formed by a groove in the base material, and by arranging a spacer 25 having an opening in the shape of the flow path 29 on the base material 1, as shown in FIG. It may be formed.
The width and height of the flow path are not particularly limited as long as the subject can be guided to the accommodating portion, and can be, for example, about 0.5 mm to 5 mm.

(3) Reaction part The electrode for sensors of this invention is arrange | positioned from an inlet to an accommodating part, and may have the reaction part containing an enzyme.
The reaction part is a part that converts a chemical potential, heat, or an optical change into an electric signal accompanying a change movement of a substrate-specific substance.

When the sensor electrode of the present invention is used as a glucose sensor for measuring glucose concentration, examples of the enzyme include glucose oxidase (GOD) and glucose dehydrogenase (GDH).
When the sensor electrode of the present invention is used for a cholesterol sensor, an alcohol sensor, a scroll sensor, a lactate sensor, or a fructose sensor, examples of the enzyme include cholesterol esterase, cholesterol oxidase, alcohol oxidase, lactate oxidase, fructose dehydrogenase, Those suitable for the reaction system such as xanthine oxidase and amino acid oxidase can be appropriately used.
The reaction part may contain, for example, potassium ferricyanide, a ferrocene derivative, a quinone derivative, an osmum derivative, etc. as a redox substance together with these enzymes.

When the sensor electrode of the present invention is used as an endotoxin sensor for measuring endotoxin concentration, an enzyme containing at least factor C can be used as the enzyme, and in particular, factor B and a clotting enzyme precursor are further included. Those can be preferably used.
The reaction part may contain a peptide compound to which a redox substance is bound together with the enzyme.
Examples of the redox substance include compounds represented by the following general formula (1) including paramethoxyaniline (hereinafter sometimes simply referred to as pMA), dyes, paraaminophenol (pAP), and the like. Can do.
Specific examples of the dye include 2,4-dinitroaniline (DNP), p-nitroaniline (pNA), 7-methoxycoumarin-4-acetic acid (MCA), Dansyl dye, and the like. .

(In the formula (1), R is —O—C _n H _{2n + 1} or —S—C _n H _{2n + 1} , and n is an integer from 1 to 4.)

  In the present invention, the compound represented by the general formula (1) is preferably pMA. The shorter the alkyl chain of the compound represented by the above general formula (1), the higher the water solubility, and the activated factor C or the activated coagulase has a peptide sequence of the oligopeptide contained in the peptide compound. It becomes easy to recognize. For this reason, since the compound represented by the general formula (1) bound to the oligopeptide as a redox substance is pMA, the peptide compound has increased reactivity with the activated factor C and the like. is there.

  In the present invention, the redox substance is preferably pMA or pAP. PMA and pAP released from the peptide compound and pMA and pAP bound to the peptide compound have different redox potentials, and the difference is relatively large. For this reason, even if the concentration of pMA or pAP released from the peptide compound is extremely small, the concentration of endotoxin can be detected with high accuracy.

The peptide compound to which the redox substance is bound is not limited as long as it has a redox material and an oligopeptide to which the redox substance is bound. A peptide having a peptide protecting group bonded to the end can be used.
The oligopeptide is not particularly limited as long as it can release a redox substance by the action of factor C or a coagulase precursor. Examples of the oligopeptide capable of releasing the redox substance by the action of the coagulation enzyme precursor include tripeptides such as Leu-Gly-Arg and Thr-Gly-Arg.

The place where the reaction unit is arranged is arranged between the introduction port and the storage unit.
In the present invention, it is particularly preferable that the arrangement location is in the accommodating portion, in particular, a location that overlaps the electrode portion in plan view, and in particular, a location in contact with the electrode portion. It is preferable. This is because the arrangement location is easy to mix and measure the reaction part and the sample.
6 that has already been described is a portion where the reaction portion 27 is formed so as to overlap a part of the working electrode 21 and the counter electrode 23 included in the electrode portion 11 in plan view, and is further arranged so as to be in contact with these electrodes. An example is shown.

The method for forming the reaction part is not particularly limited as long as the reaction part can be arranged at a desired position. For example, it can be formed by applying a solution containing the enzyme onto the electrode part exposed in the housing part and then drying to remove the solvent component.
As a method for applying the enzyme-containing solution, for example, a dispenser method can be used.
When forming the reaction part, the enzyme loses its activity when left at a temperature of 40 ° C. or higher for a long time. Therefore, it is preferable to dry the solvent at 40 ° C. or lower and quickly return to room temperature after drying.

(4) Cover layer In this invention, the cover layer may be arrange | positioned on the board | substrate.

The cover layer may have a through hole. A through hole can be used as the inlet. Moreover, the accommodating part 28 can also be formed by the through-hole provided in the cover layer 26 so that it may illustrate in FIG.
The size of the through hole can be the same as the size of the housing portion when the housing portion 28 is formed by the through hole as illustrated in FIG. Although not shown, when the through hole is an introduction port and is connected to the flow path, it may be of a size capable of introducing the sample.
The shape of the through hole is not particularly limited, but the shape of the through hole in plan view is preferably a circle or an ellipse because it is easy to form the through hole.

  Moreover, the groove | channel for forming a flow path and an accommodating part may be formed in the opposing surface with the base material of a cover layer. The size of the groove for forming the flow path and the accommodating portion can be the same as the size of the flow path and the accommodating portion.

The cover layer is not particularly limited as long as the surface has insulating properties, and examples thereof include a glass substrate and a resin substrate.
The shape of the cover layer is not particularly limited, and can be an arbitrary shape such as a square shape such as a square shape, a circular shape, or an elliptical shape.

A cover layer is arrange | positioned on a base material so that a terminal may be exposed at least. Further, when the housing portion is formed by the through hole of the cover layer, the cover layer is arranged so that the through hole is located on the electrode portion. Further, when the flow path and the accommodating portion are formed by the groove of the cover layer, the cover layer is arranged so that a part of the groove is located on the electrode portion.
The cover layer can be attached to the substrate via an adhesive or a pressure-sensitive adhesive, for example.

(5) Spacer In the present invention, a spacer may be disposed between the base material and the cover layer. The spacer is provided in order to form the accommodating portion and the flow path.
The spacer can have an opening corresponding to the accommodating portion and the flow path. The size and shape of the opening can be the same as the size and shape of the accommodating portion and the flow path.

The spacer is not particularly limited as long as it has insulating properties, and for example, a photocurable resin, a thermosetting resin, or the like can be used. In the case of using a photocurable resin or a thermosetting resin, the spacer can be formed at low cost. In addition, a resin base material can be used as the spacer. For example, a resin base material such as polyethylene terephthalate (PET) resin, vinyl chloride resin, polystyrene (PS) resin, polypropylene (PP) resin, or polyester resin can be used. It is.
The shape of the spacer is not particularly limited, and may be any shape such as a square shape such as a square shape, a circular shape, or an elliptical shape.

The spacer is disposed on the substrate so that at least the terminal is exposed and the opening of the spacer is positioned on the electrode portion.
The spacer can be attached to the substrate via an adhesive or a pressure-sensitive adhesive, for example.

(6) Insulating layer In this invention, an insulating layer can be formed so that a wiring part may be covered. The insulating layer can suppress oxidation of the wiring portion and prevent a short circuit.
As a material for the insulating layer, for example, a thermosetting resin, a photocurable resin, or the like can be used.
The insulating layer can be formed by covering the wiring portion and forming the insulating layer in a pattern so as not to cover the electrode portion and the terminal portion. For example, a photolithography method, a screen printing method, and a gravure printing method. Method, flexographic printing method, inkjet method and the like.

4). Applications The sensor electrode of the present invention can be used for various measurements, specifically, electrodes for applications such as humidity sensors; electrodes for gas sensors such as odor sensors and NO ₂ sensors; glucose sensors, Examples include electrodes for biosensor applications such as cholesterol sensors, alcohol sensors, scroll sensors, lactic acid sensors, fructose sensors, endotoxin sensors, and immunosensors.
In the present invention, the sensor electrode is preferably used for biosensor applications, and particularly preferably used as an endotoxin sensor. This is because the sensor electrode of the present invention is low-cost, and therefore, endotoxin concentration measured in various situations can be measured at low cost.
For example, as a method for using the sensor electrode as an endotoxin sensor, an electrode layer having two working electrodes, a first working electrode and a second working electrode, a standard electrode, and a counter electrode as necessary is used. And a method for measuring the concentration of endotoxin.
In addition, examples of the application of the sensor electrode include an electrode application for dielectric analysis and an electrode application for a biofuel cell.

Examples of the sample measured using the sensor electrode include biological samples such as blood, saliva, sweat and urine, environmental inspection objects, foods, cosmetics, waste liquids, resins, and the like.
In addition, about the said sample, it is not limited to a liquid sample, A gas sample can also be included.
In the present invention, from the viewpoint of having both a working electrode and a standard electrode, the sample is preferably a liquid sample.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be specifically described using examples and comparative examples.

  The reagents used in this example are as follows.

(1) Standard endotoxin solution The endotoxin standard product is manufactured by Seikagaku Corporation E.I. Coli O113: USP Reference Standard Endotoxin derived from H10 strain was used. A standard endotoxin solution was prepared using endotoxin-free water attached to Endospecy ES24M manufactured by Seikagaku Corporation, and was vigorously stirred with a vortex mixer for 30 minutes immediately before use. The endotoxin concentration was shown as the final concentration in the measurement solution.

(2) Lysate reagent As the lysate reagent, Endspecy ES24M manufactured by Seikagaku Corporation, in which the lysate reagent was sealed in a dedicated test tube for each test in a lyophilized state, was used.

(3) LGR-pAP
LGR-pAP was synthesized using the same method as the synthesis of LGR-pMA described in JP-A-2015-187607, and stored at −20 ° C. as a 10 mM stock solution.
For dilution of LGR-pAP, a buffer solution attached to Endospecy ES24M manufactured by Seikagaku Corporation was used.

[Example 1]
After forming a 50 nm palladium (Pd) film on the PET base material (substrate) by sputtering, etching is performed by a photolithography method, and the two working electrodes, one counter electrode, and the like already shown in FIG. A patterned palladium layer having an electrode part including one standard electrode, a terminal part, and a wiring part was formed.
Next, a gold layer having a thickness of 10 nm was formed on the patterned palladium layer by electroless plating to form a sensor electrode having a base material and a first electrode layer. The electroless plating of the gold layer was performed using a non-cyan type electroless gold plating solution.
The two working electrodes have a comb shape, and the width of the comb teeth and the width between the comb teeth are 9 μm and 9 μm, respectively. The width between adjacent comb teeth of each working electrode (c in FIG. 1) is the sum of the width of the comb teeth and twice the width between the comb teeth. The poles were arranged so that the widths between the comb teeth were equal. In Example 1, the width between adjacent comb teeth (c in FIG. 1) was 27 μm.
Further, the width between the comb teeth is a distance between the comb teeth of the two comb-shaped working electrodes, and specifically, is indicated by e in FIG.

[Example 2]
A sensor electrode was formed in the same manner as in Example 1 except that the thickness of the gold layer was 30 nm.

[Example 3]
A sensor electrode was formed in the same manner as in Example 1 except that the thickness of the gold layer was 50 nm.

[Example 4]
A sensor electrode was formed in the same manner as in Example 1 except that the thickness of the gold layer was 5 nm, and the width of the comb teeth and the width between the comb teeth were 5 μm and 5 μm, respectively.

[Example 5]
A sensor electrode was formed in the same manner as in Example 1 except that the thickness of the gold layer was 10 nm, and the width of the comb teeth and the width between the comb teeth were 5 μm and 5 μm, respectively.

[Example 6]
A sensor electrode was formed in the same manner as in Example 1 except that the thickness of the gold layer was 5 nm, and the width of the comb teeth and the width between the comb teeth were 7 μm and 7 μm, respectively.

[Example 7]
A sensor electrode was formed in the same manner as in Example 1 except that the thickness of the gold layer was 10 nm, and the width of the comb teeth and the width between the comb teeth were 7 μm and 7 μm, respectively.

[Comparative Example 1]
A sensor electrode was formed in the same manner as in Example 1 except that the gold layer was not formed.

[Comparative Example 2]
A sensor electrode was formed in the same manner as in Example 1 except that the thickness of the gold layer was 100 nm.

[Comparative Example 3]
A sensor electrode was formed in the same manner as in Example 1 except that the thickness of the gold layer was 1 nm, and the width of the comb teeth and the width between the comb teeth were 8 μm and 8 μm, respectively.

[Comparative Example 4]
A sensor electrode was formed in the same manner as in Example 1 except that the thickness of the gold layer was 1 nm.

[Comparative Example 5]
A sensor electrode was formed in the same manner as in Example 1 except that the thickness of the gold layer was 0.5 nm.

[Comparative Example 6]
A sensor electrode was formed in the same manner as in Example 1 except that the thickness of the gold layer was 1 nm, and the width of the comb teeth and the width between the comb teeth were 6 μm and 6 μm, respectively.

[Reference Example 1]
After forming a 50 nm palladium (Pd) film on the PET substrate (substrate) by sputtering, etching is performed by photolithography, and one counter electrode and one standard electrode as shown in FIG. A patterned palladium layer having an electrode part including the terminal part and a wiring part connected to the counter electrode and the standard electrode was formed.
Next, after a 50 nm gold (Au) film is formed on the PET base material (substrate) by sputtering with a mask covering the palladium layer, etching is performed by a photolithography method. A sensor having a gold working electrode, a palladium standard electrode, and a palladium counter electrode, in which a pattern-shaped gold layer having a terminal portion and a wiring portion connected to the two working electrodes is formed. An electrode was formed.
The two working electrodes have a comb shape, and the width of the comb teeth and the width between the comb teeth are 9 μm and 9 μm, respectively.

[Evaluation 1]
Endotoxin concentration was detected using the LAL cascade reaction.
As the lysate reagent and the buffer, a reagent attached to Endospecy manufactured by Seikagaku Corporation was used. LGR-pAP (20 μL), buffer (180 μL) and endotoxin standard solution (200 μL) were added to a test tube containing the lysate reagent (Endospecy ES24M) in a lyophilized state, and stirred to prepare 400 μL of a mixed solution.
After reacting at 37 ° C. for 60 minutes, 200 μL of the mixed solution was dropped on the electrode part of the sensor electrode prepared in Examples, Comparative Examples and Reference Examples, and then pAP released from LGR-pAP was cyclic vol Detection was performed using a tammetry method (CV method). The results are shown in FIG. 7 (Example 1), FIG. 8 (Example 2), FIG. 9 (Example 3), FIG. 10 (Example 4), FIG. 11 (Example 5), and FIG. FIG. 13 (Comparative Example 1), FIG. 14 (Comparative Example 2), FIG. 15 (Comparative Example 3), FIG. 16 (Comparative Example 4), FIG. 17 (Comparative Example 5), FIG. 19 (Reference Example 1).
In addition, from the cyclic voltammograms obtained for the examples, comparative examples, and reference examples, the observability of the oxidation peak and the reduction peak and the peak current value were evaluated. The results are shown in Table 1 below. Note that L / S in Table 1 indicates that L indicates the width of the comb teeth and S indicates the width between the comb teeth.
In the CV method, the scanning speed was 20 mV / s, and the range was 0 V → 0.6 V → −0.4 V → 0 V.
In addition, the concentration of LGR-pAP in the mixed solution was 0.5 mM, and the concentration of the endotoxin standard solution was 1000 EU / L.

In addition, the observation of the oxidation peak and the reduction peak is made by visually confirming the cyclic voltammogram, and when both the oxidation peak and the reduction peak can be observed, it is indicated as ◯, and when both the oxidation peak and the reduction peak cannot be observed. Is x.
Specifically, when the oxidation peak position (for example, the position of the GG line parallel to the vertical axis in FIGS. 7 to 19) was observed at 0.3 V or less, it was determined that the oxidation peak could be observed. .
Further, when a straight line parallel to the horizontal axis (for example, the HH line in FIGS. 7 to 19) passes through the reduction peak observed in the cyclic voltammogram, the characteristic after the reduction peak is determined from that line. What is above, that is, when the potential is scanned from 0.6 V to -0.4 V, a current value higher than the current value at the reduction peak is observed on the lower potential side than the potential at which the reduction peak was observed It was judged that a reduction peak could be observed.
In Example 4 and Example 6, the oxidation peak position was 0.3 V or less, and as a cyclic voltammogram, a portion parallel to at least 0.05 V was observed between −0.2 V and 0 V. It was. And, the high voltage side end of the parallel part is recognized as a reduction peak, and the current value on the low voltage side is observed to be a current value equal to or higher than the current value at the reduction peak by observing the part where the current value on the low voltage side is constant. It was judged.
Moreover, in Examples 1-6, the reduction | restoration peak was observed by the electric potential of -0.2V or more and 0V or less.
Further, the peak current value includes a downwardly convex inflection point (reduction peak) detected at a potential of −0.2 V or more and 0 V or less and a reduction peak adjacent to the reduction peak in the cyclic voltammogram. Two inflected inflection points (adjacent peaks) are identified, an auxiliary line connecting the two adjacent peaks with a straight line is created, and the difference in current value between the reduction peak and the auxiliary line (FIGS. 7 to 12) And p) in FIG. 19 was obtained.
In addition, as shown in FIG. 11 (Example 5), when the inflection point on the high potential side among the adjacent peaks is unclear, the value on the curve at 0.1 V is recognized as the adjacent peak.

[Evaluation 2]
400 μL of a mixed solution was prepared in the same manner as in Evaluation 1, except that 200 μL of an endotoxin standard solution having a concentration of 1 EU / L was used as the endotoxin standard solution. Next, 200 μL of the mixed solution was dropped on the electrode part of the sensor electrode produced in Example 1 and Example 7, and then pAP released from LGR-pAP was detected using the amperometry method. In the amperometry method, an initial potential of −0.2 V is applied for 10 seconds, then the potential is stepped to 0.4 V and applied for 30 seconds to record the current resulting from the oxidation reaction of pAP, and then to −0.15 V. The potential was stepped and applied for 30 seconds, and the current from the pAP reduction reaction was recorded. The results are shown in FIG. 20 (Example 1) and FIG. 21 (Example 7).

[Evaluation 3]
PAP was detected using the amperometry method in the same manner as in Evaluation 2, except that the endotoxin standard solution was not added. The results are shown in FIG. 20 (Example 1) and FIG. 21 (Example 7).

[Summary]
From Evaluation 1, when the gold layer is not formed (Comparative Example 1), when the thickness of the gold layer is 1 nm or less (Comparative Examples 3 to 6) or larger than 50 nm (Comparative Example 2), the oxidation peak and reduction In some cases, both of the peaks could not be clearly detected, whereas in the examples where the thickness of the gold layer was 5 nm to 50 nm, both the oxidation peak and the reduction peak could be clearly detected.
Thus, when the gold layer is within a predetermined thickness range, for example, when it is 50 nm or less, particularly when it is 5 nm or more and 50 nm or less, the first electrode layer in which the palladium layer and the gold layer are laminated is stable. It was confirmed that it also functions as a standard electrode.
Moreover, from the evaluation 2 and the evaluation 3, in the Example, it has confirmed that it could distinguish clearly by the case where the density | concentration of an endotoxin is 0 EU / L and the case of 1 EU / L. Therefore, in the Examples, it was confirmed that stable detection was possible even when the concentration of endotoxin as a measurement target was as low as 1 EU / L.

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Palladium layer 3 ... Gold layer 4 ... 1st electrode layer 5 ... 2nd electrode layer 6 ... Electrode layer 10 ... Electrode for sensors 11 ... Electrode part 12 ... Wiring part 13 ... Terminal part 21 ... Working electrode 22 ... Standard electrode 23 ... Counter electrode 24 ... Insulating layer 25 ... Spacer 26 ... Cover layer 27 ... Reaction part 28 ... Housing part 29 ... Channel 30 ... Inlet

Claims (7)

Having a first electrode layer on one surface of the insulating substrate;
The first electrode layer includes a working electrode and a standard electrode;
The first electrode layer has a first layer containing palladium on one surface of the substrate, and further, the standard of the first layer on the surface opposite to the surface on which the substrate is formed. An electrode for a sensor having a second layer containing gold formed so that the electrode functions as a standard electrode.   The sensor electrode according to claim 1, wherein the thickness of the second layer is 5 nm or more and 50 nm or less.   The sensor electrode according to claim 1, wherein a thickness of the first layer is larger than a thickness of the second layer. Having an electrode layer including the first layer on one surface of the substrate;
4. The sensor electrode according to claim 1, wherein all of the electrode layers are the first electrode layers. 5. On one side of the substrate,
An object to be measured can be accommodated, and an accommodating part in which the working electrode and the standard electrode are disposed,
A flow path having one end connected to the housing and the other end connected to the inlet;
The sensor electrode according to any one of claims 1 to 4, wherein the sensor electrode is provided.   The sensor electrode according to any one of claims 1 to 5, wherein the working electrode has a comb shape in a plan view.   The sensor electrode according to any one of claims 1 to 6, wherein the sensor electrode is used as an endotoxin sensor.