JP2018189480A - Chemical sensing electrode, chemical sensing device, and method for manufacturing chemical sensing electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemical sensing electrode having high conductivity, excellent reliability, capable of measuring with high accuracy, and being able to be manufactured at a relatively low cost, and a method for manufacturing the same. SOLUTION: A support 1 and two or more electrodes 4a and 4b and a sensitive substance 5 are provided, and at least one or more electrodes are a substrate having a surface made of metal and a carbon coating 3 covering at least a part of the surface. The carbon film is a continuous film having a thickness of 1 μm or more, and the sensitive substance 5 is a sensitive substance that reacts with a specific chemical substance, covers between two or more electrodes, and is a chemical substance adsorbed on the sensitive substance. A chemical sensing electrode that detects the presence of a chemical substance by measuring the electrical characteristics of the sensitive substance that changes depending on the above with two or more electrodes is used, and the formation of a carbon film is a method for manufacturing a chemical sensing electrode by a plating method. [Selection diagram] Fig. 1

Description

  The present invention relates to a chemical sensing electrode, a chemical sensing device using the same, and a method for manufacturing the chemical sensing electrode.

  Currently, medical care is highly developed, and it is possible to grasp the condition of a patient by analyzing body fluids such as blood, saliva, urine, body odor, and exhaled breath. For example, research has been conducted on determining the presence or absence of dental caries by measuring the pH of saliva and diagnosing diabetes by measuring the blood sugar level of tears. In addition, by examining nitric oxide and hydrogen sulfide in exhaled breath, it is possible to grasp the state of inflammation, infection, etc. in the trachea and mouth. These examinations are performed, for example, when a patient collects body fluid by himself or collects exhaled breath and body odor, and these are measured and analyzed by a medical institution.

  On the other hand, an apparatus for measuring and analyzing body fluid, body odor, and exhalation by itself without a patient going to a medical institution has been developed. This not only enables speeding up of inspection and analysis, but also enables inspection to be performed at a high frequency. Therefore, it becomes possible to discover before changing the physical condition. Therefore, the number of cases that require advanced medical care and administration of expensive drugs is reduced, and medical costs in an aging society can be reduced.

  There are various biosensing techniques as described above, and electrochemical techniques are widely used because trace components can be detected with high sensitivity. In the electrochemical technique, biological information that is a chemical characteristic is detected as an electrical signal, and thus there is an advantage that it is easy to process and analyze a signal obtained using a semiconductor device or the like. For this reason, development of a new electrochemical sensing device and a sensing technique using the same has been actively conducted.

  For example, Patent Document 1 describes an electrochemical sensor for introducing an ionomer to the electrode surface and measuring the concentration of nitric oxide in exhaled breath. Patent Document 2 describes an electrochemical sensor that analyzes the carbon monoxide concentration by measuring the resistance value of a sensitive layer using cobalt oxide carrying a noble metal as the sensitive layer. Patent Document 3 describes an electrochemical sensor that analyzes the concentration of mercaptan or hydrogen sulfide as a sensitive layer containing titanium oxide, cerium oxide, and vanadium oxide by measuring the resistance value of the sensitive layer. .

  Like these technologies, an electrochemical sensor collects gas generated from a living body such as sweat and breathing and gas in the environment, and adsorbs various chemical substances contained in the gas to sensitive substances covering the electrodes. By measuring and analyzing changes in the current value, resistance value, and capacitance value flowing between the electrodes, information serving as an index (biomarker) for grasping the characteristics and state of the living body is obtained. Hereinafter, an electrode used in an electrochemical sensor and having a sensitive substance is generally referred to as a “chemical sensing electrode”.

  One of the important points in realizing an electrochemical sensor is that there are various chemical sensing electrodes that perform electrochemical measurements and transmit the measurement results as electrical signals, including the cost of materials, configurations, and manufacturing methods. From the point of view, it can be adapted to practical use. In Patent Document 1, since glass or silicon ceramic is used for the support and a dry etching process is used for processing the support and forming electrodes, there are problems in terms of manufacturing method and cost.

The electrode must first be electrochemically stable. For example, when an electrode in which a conductive material is partially coated with an electrochemically inactive (stable) conductive material and a portion that is not coated with the conductive material is supported by an insulating material, the insulating material and When a corrosive gas enters between the electrodes, an electrochemically unstable conductive material comes into contact with the gas. As a result, the conductive material is corroded and the measurement cannot be continued with sufficient reliability. Further, when gas enters between the insulating material and the electrode, even if the surrounding gas concentration decreases, the gas between the insulating material and the electrode is difficult to be replaced, so that it is difficult to quickly detect a change in the gas concentration.

  When an electrochemically stable conductive material is coated on a non-conductive material instead of a conductive material, problems such as corrosion do not occur. However, in this case, if the coating made of a conductive material is thin and the occurrence of pinholes cannot be avoided at the manufacturing stage, measurement cannot be performed with sufficient reliability. That is, unless a coating made of a conductive material is formed to be considerably thick, amperometry measurement (a method in which current is measured with a constant potential applied to the electrode) or coulometry measurement (current amount is integrated over time and measured as a charge amount) It is impossible to pass a large current that can ensure the accuracy of the method.

  In general, noble metals such as gold and platinum are selected as the electrochemically stable conductive material. Since these substances are very expensive, they are formed as a thin film on a substrate and formed into an electrode shape by patterning. However, in order to avoid pinholes, it is necessary to secure a corresponding film thickness, so that even a thin film is expensive.

  In Patent Documents 2 and 3, a baked sensitive material is used, which is convenient to carry. However, since an electrode is produced by baking a noble metal paste, high costs are unavoidable, and foreign substances contained in the paste In addition to concerns about changes in electrochemical properties and pinholes caused by the remaining of the electrode in the electrode, it is difficult to print paste on a solid support, and the shape of the chemical sensing electrode and thus the sensor is limited. There is a problem of being done.

  A technique using carbon instead of a noble metal as an electrochemically stable conductive material is also disclosed. For example, the carbon electrode described in Patent Document 4 covers an insulating substrate, a conductive layer provided on the insulating substrate, a first carbon layer provided on the conductive layer, and the first carbon layer. And a second carbon layer provided on the surface. The first carbon layer includes carbon having an SP2 bond and an SP3 bond and having an amorphous structure. The second carbon layer contains carbon having an SP2 bond. Specifically, the first carbon layer is a carbon layer made of diamond-like carbon or amorphous carbon having an amorphous structure formed by a vapor deposition method.

  However, the electrochemical sensor in Patent Document 4 is intended for long-time measurement and repeated measurement, and there are restrictions such as the necessity of using noble metal as a material for some conductive layers and the need to form by vacuum film formation. In order to manufacture such an electrochemical sensor, there is a problem that material costs and processes are increased.

JP 2014-137342 A Japanese Patent Laying-Open No. 2015-040753 JP-A-2006-125916 International Publication No. 2010/004690

The present invention solves one or more of the problems in the electrochemical sensor described above, has a high conductivity, is excellent in reliability, can be measured with high accuracy, and can be manufactured at a relatively low cost. An object of the present invention is to provide a chemical sensing device using the same, and a method for producing a chemical sensing electrode.

In order to solve the above problems, the invention according to claim 1 is a chemical sensing electrode comprising a support, two or more electrodes, and a sensitive substance,
The at least one electrode includes a base having a surface made of metal and a carbon coating covering at least a part of the surface,
The carbon coating is a continuous film having a thickness of 1 μm or more,
The sensitive substance is a sensitive substance that reacts with a specific chemical substance, covers between the two or more electrodes,
A chemical sensing electrode having a function of detecting the presence of the chemical substance by measuring electrical characteristics of the sensitive substance that changes depending on the chemical substance adsorbed on the sensitive substance with the two or more electrodes. Is.

The invention according to claim 2 comprises a plurality of sets of the two or more electrodes, and each set covers a different sensitive material between the two or more electrodes for each set,
2. The chemical sensing electrode according to claim 1, wherein an electrical property of the sensitive substance that varies depending on a chemical substance adsorbed on a different sensitive substance for each group is measured by the two or more electrodes of each group. It is a thing.

  The invention according to claim 3 is the chemical sensing electrode according to claim 1 or 2, wherein the sensitive substance includes at least one of an oxide semiconductor, an organic semiconductor, and a compound semiconductor.

  The invention according to claim 4 is characterized in that the two or more electrodes include electrodes having a separation distance of 1 mm or less between the electrodes and the chemical sensing electrode according to any one of claims 1 to 3 It is a thing.

  The invention according to claim 5 is the chemical sensing electrode according to any one of claims 1 to 4, wherein the two or more electrodes include an electrode having a coil shape.

  Invention of Claim 6 equips the inside or the exterior with the mechanism which applies an electrical signal between the electrodes of the chemical sensing electrode in any one of Claims 1-5, and the mechanism which measures an electrical signal Is a chemical sensing device characterized by

The invention according to claim 7 includes a step of providing a substrate having a surface made of metal,
Coating at least a part of the metal surface of the substrate with a carbon coating by plating to obtain an electrode;
Fixing the electrode coated with the carbon coating to a support;
And a step of covering the electrode fixed to the support with a sensitive substance.

  According to an eighth aspect of the present invention, prior to the step of coating at least a part of the metal surface of the base with a carbon coating by plating, the base is processed and deformed, and the base is fixed to the support. The method for producing a chemical sensing electrode according to claim 7, wherein either or both of the steps are performed in advance.

Since the chemical sensing electrode of the present invention is coated with a carbon film composed of a continuous film having a thickness of 1 μm or more on at least a part of the metal surface of the substrate, the conductivity is high and the reliability is excellent.
A chemical sensing electrode capable of measuring with high accuracy and a chemical sensing device using the same are obtained. In addition, since the method for producing a chemical sensing electrode of the present invention forms the carbon film by a plating method, it can be produced at a relatively low cost and high productivity, and a carbon film having a uniform thickness can be easily obtained. A chemical sensing electrode with a high degree of freedom can be obtained.

It is (a) schematic sectional drawing (b) schematic top view which shows the structure of the chemical sensing electrode which concerns on 1st Embodiment of this invention. It is a schematic plan view which shows the structure of the chemical sensing electrode which concerns on 2nd Embodiment of this invention. It is a schematic cross section which shows the manufacturing process of the chemical sensing electrode based on 1st Embodiment of this invention produced in Example 1. FIG. It is a perspective view which shows the form after (a) manufacturing process of the chemical sensing electrode which concerns on 3rd Embodiment of this invention produced in Example 2, and (b) the form after manufacture.

  Hereinafter, a chemical sensing electrode, a chemical sensing device, and a method for manufacturing a chemical sensing electrode according to an embodiment of the present invention will be described with reference to the drawings. The same components are denoted by the same reference numerals unless there is a reason for the sake of convenience, and redundant description is omitted. In each drawing, the thicknesses and ratios of the constituent elements may be exaggerated for ease of viewing, and the number of constituent elements may be reduced. Moreover, it is not limited to the following embodiment in the range which does not deviate from the meaning of this invention.

  Fig.1 (a) is a schematic cross section which shows the structure of the chemical sensing electrode 10 which concerns on 1st Embodiment of this invention, (b) is a schematic top view similarly. Usually, a chemical sensing electrode for obtaining information by an electrochemical method includes two or more electrodes. The two or more electrodes are, for example, one or more pairs of measurement electrodes, a pair of measurement electrodes and a reference electrode, or three electrodes in which a pair of measurement electrodes and a reference electrode are combined. Although the chemical sensing electrode of the present invention also includes two or more electrodes, the chemical sensing electrode 10 of FIG. 1 illustrates the case of two electrodes.

  The chemical sensing electrode 10 according to the first embodiment of the present invention further includes a base 2 having a surface in which at least one of the two or more electrodes (both the two electrodes 4a and 4b in FIG. 1) is made of metal, And a carbon coating 3 that covers at least a part of the surface (at least the entire region that can be contacted with the chemical substance to be measured). Since carbon is electrochemically inactive, it does not easily deteriorate even when it comes into contact with a living body, liquid, or gas.

  The carbon coating 3 provided in the chemical sensing electrode of the present invention is a continuous film having a thickness of 1 μm or more. Here, the continuous film is not a porous film or a film made of carbon particles such as those formed using a carbon paste, but a dense film. Furthermore, since it has a sufficient thickness of 1 μm or more, it is a film with a very low possibility of pinholes. Therefore, the conductivity is high, the reliability is high, and the measurement with high accuracy is possible.

  Carbon is a cheaper material than precious metals, and its price fluctuation is small. Therefore, the chemical sensing electrode of the present invention can be manufactured at a relatively low cost.

The chemical sensing electrode 10 according to the first embodiment of the present invention further includes a sensitive substance 5 that reacts with a specific chemical substance. The sensitive substance 5 needs to be electrically connected to the two electrodes 4a and 4b as shown in FIG. The covering shape of the sensitive material 5 may be a shape covering the entire electrode, but it is sufficient that at least the electrodes 4a and 4b are electrically connected. For example, only the side walls of the electrodes 4a and 4b are in contact with the sensitive material 5. You may do it. In the present application, FIG.
As shown in b), the shape in which the sensitive material 5 covers a part of the electrodes 4a and 4b will be referred to as “cover” as a representative connection form.

  The sensitive substance 5 is preferably in the form of a gel, a paste, or a sheet in order to reliably cover the two electrodes. If it is a gel or paste, it can be applied by applying it sufficiently thickly by printing or spraying, and firing and drying as necessary. If it is a sheet form, it can be processed into a necessary shape in advance, and can be used after being attached on an electrode. Alternatively, it is possible to cut and use the entire support 1 after a sheet that has not been cut is attached to the entire chemical sensing electrode.

  The chemical substance is detected by measuring the electrical characteristics of the sensitive substance in contact with the chemical substance and capturing the change. In other words, the presence of the chemical substance is detected by measuring the electrical characteristics of the sensitive substance that changes depending on the chemical substance adsorbed on the sensitive substance with two or more electrodes, and is quantified in comparison with a calibration curve or the like. For example, the concentration of the gas can be measured by comparing the electrical characteristics when placed in the atmosphere with the electrical characteristics when placed in a specific gas. The electrical characteristics include voltage, current, inductance, capacity, impedance, and the like. In addition, as an electrical signal applied at the time of measurement, direct current, alternating current, arbitrary sine wave, rectangular wave, impulse waveform, and the like can be freely selected.

  FIG. 2 is a schematic plan view showing the configuration of the chemical sensing electrode 20 according to the second embodiment of the present invention. The chemical sensing electrode of the second embodiment is provided with a plurality of sets of two or more electrodes on one support 1, and the chemical sensing electrode 20 of FIG. 2 shows a mode in which two sets of two electrodes 4a and 4b are provided. Yes. In each group, two or more electrodes are covered with different sensitive substances 5 and 6 for each group, and the electrical characteristics of the sensitive substances 5 and 6 that change depending on the chemical substances adsorbed to the sensitive substances 5 and 6 are determined. Measure with two or more electrodes.

  By using different sensitive substances for each group, it becomes possible to measure multiple types of chemical substances simultaneously. If the same type of sensitive substance is used, it is possible to improve the measurement accuracy and measure the chemical concentration difference due to the difference in location.

  The sensitive substance is preferably a substance containing at least one of an oxide semiconductor, an organic semiconductor, and a compound semiconductor, but is not particularly limited as long as it exhibits a reaction with a specific chemical substance. Examples of oxide semiconductors include tin oxide, zinc oxide, and indium oxide. Examples of solid electrolytes that exhibit semiconductor characteristics include copper bromide and silver sulfide. These may be used alone or in combination.

  In electrical measurement, it is necessary to reduce the noise as much as possible. For this purpose, it is desirable to make the distance between the electrodes as small as possible in two or more electrodes. Here, the inter-electrode separation distance is the shortest linear distance in a plan view of the opposite ends of two or more electrodes.

  By narrowing the distance between the electrodes, the resistance value of the sensitive substance itself becomes small, and it becomes easy to detect a change in electrical characteristics even with a very small amount of chemical substance. In order to realize this, it is preferable to set the distance between the electrodes to 1 mm or less, more preferably 0.5 mm or less. When the distance between the electrodes exceeds 1 mm, there are disadvantages in terms of a decrease in detection accuracy due to an increase in resistance value, a material cost, a firing / drying time of the sensitive substance, and the like.

The chemical sensing device of the present invention is a chemical sensing device including a mechanism for applying an electric signal between the electrodes of the chemical sensing electrode and a mechanism for measuring the electric signal in addition to the chemical sensing electrode described above. To apply and measure these electric signals, a power supply device and a measurement unit are required. These devices and units may be included in the chemical sensing device of the present invention, or may be connected to the chemical sensing electrode of the present invention as an external unit.

  The method for producing a chemical sensing electrode of the present invention includes a step of providing a substrate having a surface made of metal, a step of coating at least a part of the surface of the substrate made of metal with a carbon coating by a plating method, and a carbon coating, A method for producing a chemical sensing electrode, comprising: a step of fixing an electrode coated with a substrate to a support; and a step of covering the electrode fixed to the support with a sensitive substance.

  In the method for producing a chemical sensing electrode of the present invention, since a plating method is preferably used as a method of coating at least a part of the metal surface of the substrate with a carbon film, a thick carbon film can be formed. For example, a carbon film having a thickness of 1 to 5 μm can be formed.

  Moreover, according to the plating method, a carbon film having a uniform thickness can be formed even when the substrate has a complicated shape. For example, when the substrate has a curved or bent shape, the carbon film can be formed so as to cover at least a region of the metal surface of the substrate where the substrate is curved or bent. Therefore, it is possible to increase the degree of freedom in shape of the chemical sensing electrode and thus the sensor.

  Furthermore, according to the plating method, the carbon coating can be formed at a relatively low cost and with high productivity. Specifically, for example, a carbon plating technique that is implemented by I'MCEP Co., Ltd. using molten salt electrolysis can be used.

  Another method for forming a carbon film on the surface of a substrate using an electrochemical reaction is to include conductive carbon particles in an electrolytic solution containing a metal to be deposited so that the substrate becomes a cathode. There is a method of forming a carbon film by reacting.

  As the carbon particles, for example, those including a graphite structure and a mixture of SP2 structure and SP3 structure are used. As a metal to be deposited, for example, in addition to noble metals such as gold, platinum, silver, rhodium, and ruthenium, it can be used in an electrolytic plating solution made of an aqueous solution such as iron, nickel, cobalt, copper, chromium, zinc, or an alloy thereof. A thing can be selected suitably. Alternatively, when a non-aqueous dimethyl sulfone bath is used, relatively inexpensive aluminum can be used as the metal to be deposited.

  In the manufacturing process of the chemical sensing electrode of the present invention, if a high temperature is not required when fixing the substrate to the support, for example, if it does not exceed 500 ° C., the substrate is first coated with a carbon film, and then supported. It can also be fixed to the body. That is, when the carbon film is exposed to a high temperature, the carbon film is damaged. Therefore, the order of the process of coating the carbon film and the process of fixing to the support can be changed according to the temperature applied in the process.

  The chemical sensing electrode of the present invention can be made into a chemical sensing electrode having a shape corresponding to the intended use and measurement environment by processing and deforming in advance to match the chemical substance or sensor shape for sensing the substrate. Examples of the deformation include bending the base and cutting it into a necessary shape, and press working and lathe processing can be used for these processes. Examples of deformed shapes include coil shapes, dumbbell shapes, spring shapes, donut shapes, and the like.

  From the above, in the manufacturing process of the chemical sensing electrode of the present invention, prior to the step of coating at least a part of the metal surface of the substrate with a carbon coating by plating, the substrate is deformed, and the substrate is supported. Either or both of the steps of fixing to the body can be performed in advance.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not limited to a following example.

<Example 1>
As shown in FIG. 3A, two stainless steel bases 2 having a width (X direction) of 1 mm, a length (Y direction) of 40 mm, and a thickness (Z direction) of 300 μm are prepared, and these are separated by a distance of 0.5 mm. Was placed on an unfired ceramic substrate so as to be parallel to each other, and this was fired to fix it to the ceramic substrate support 1.

  Next, as shown in FIG. 3B, the base 2 fixed on the support 1 was coated with a carbon film 3 with a thickness of 1 μm by plating to form electrodes 4a and 4b.

  Further, as shown in FIG. 3 (c), a tin oxide paste as a sensitive material 5 is applied and sintered on the surface so as to connect and cover the electrodes 4a and 4b, and the first embodiment of the present invention shown in FIG. A chemical sensing electrode 10 was obtained.

  Although not shown, ten chemical sensing electrodes 10 were electrically connected in parallel on a hot plate.

  When the electrical resistance value in the state where the chemical sensing electrode 10 as described above is heated at 300 ° C. and left in the atmosphere for 10 minutes and in the state where the chemical sensing electrode 10 is left in the carbon monoxide atmosphere for 10 minutes is measured, The electrical resistance value when placed in a carbon monoxide atmosphere is reduced to ½ or less. From this, the chemical sensing electrode 10 of this embodiment can detect carbon monoxide gas. It was confirmed.

<Example 2>
A cylindrical ceramic having a diameter of 5 mm is used as a support 11 (see FIG. 4), and two stainless steel wires having a thickness of 0.5 mm are used as a base body, and are spirally wound with a separation distance of 0.5 mm. .

  Next, as shown in FIG. 4A, the substrate fixed to the support 11 was coated with a carbon film with a thickness of 1 μm by plating to form electrodes 14a and 14b, respectively.

  Further, as shown in FIG. 4B, a tin oxide paste as a sensitive material 15 was applied to the surface so as to cover the electrodes 14a and 14b and sintered, thereby obtaining a chemical sensing electrode 30 of the third embodiment of the present invention. .

  Although not shown, the chemical sensing electrode 30 was inserted into a glass tube having an inner diameter of 10 mm.

  Electricity in a state where the chemical sensing electrode 30 is heated to 300 ° C. and the atmosphere is introduced into the glass tube and left for 10 minutes, and carbon monoxide gas is introduced into the glass tube and left for 10 minutes. When the resistance value was measured, the electrical resistance value in a state where it was left in a carbon monoxide atmosphere was reduced to ½ or less, and from this, the chemical sensing electrode 30 of this example detects carbon monoxide gas. Confirmed that it was possible.

DESCRIPTION OF SYMBOLS 1, 11 ... Support body 2 ... Base | substrate 3 ...... Carbon film 4a, 4b, 14a, 14b ... Electrode 5, 6, 15 ...・ Sensitive substances 10, 20, 30 ... chemical sensing electrodes

Claims (8)

A chemical sensing electrode comprising a support, two or more electrodes and a sensitive substance,
The at least one electrode includes a base having a surface made of metal and a carbon coating covering at least a part of the surface,
The carbon coating is a continuous film having a thickness of 1 μm or more,
The sensitive substance is a sensitive substance that reacts with a specific chemical substance, covers between the two or more electrodes,
A chemical sensing electrode having a function of detecting the presence of the chemical substance by measuring an electrical characteristic of the sensitive substance that varies depending on the chemical substance adsorbed on the sensitive substance with the two or more electrodes. A plurality of sets of the two or more electrodes are provided, and each set covers the two or more electrodes with a different sensitive substance for each set,
2. The chemical sensing electrode according to claim 1, wherein an electrical characteristic of the sensitive substance that varies depending on a chemical substance adsorbed on a different sensitive substance for each group is measured by the two or more electrodes of each group.   The chemical sensing electrode according to claim 1, wherein the sensitive substance includes at least one of an oxide semiconductor, an organic semiconductor, and a compound semiconductor.   The chemical sensing electrode according to any one of claims 1 to 3, wherein the two or more electrodes include electrodes having a distance of 1 mm or less between the electrodes.   The chemical sensing electrode according to any one of claims 1 to 4, wherein the two or more electrodes include an electrode having a coil shape.   6. A chemical sensing device comprising a mechanism for applying an electric signal between the electrodes of the chemical sensing electrode according to claim 1 and a mechanism for measuring the electric signal inside or outside. Providing a substrate having a surface made of metal;
Coating at least a part of the metal surface of the substrate with a carbon coating by plating to obtain an electrode;
Fixing the electrode coated with the carbon coating to a support;
Covering the electrode fixed to the support with a sensitive material, and a method for producing a chemical sensing electrode.   Prior to the step of coating at least a part of the metal surface of the substrate with a carbon coating by plating, either or both of the step of deforming the substrate and the step of fixing the substrate to the support are performed. The method for producing a chemical sensing electrode according to claim 7, which is performed in advance.