gas sensor

Abstract

To provide a gas sensor that has a simple structure, low manufacturing cost, is easy to handle, and is capable of detecting gases. [Solution] The device comprises a conductive porous body 20 containing a conductor in an insulating porous body, a first electrode portion 11 and a second electrode portion 12 arranged at intervals in the extending direction of the conductive porous body 20, and a resistance measuring portion 15 for measuring the electrical resistance value between the first electrode portion 11 and the second electrode portion 12. The conductive porous body 20 is a gas detection portion that detects gas, and zinc oxide is supported on the conductive porous body 20.

Description

Technical Field

[0001] This invention relates to a gas sensor for detecting gases.

Background Art

[0002] Conventionally, gas sensors have been used to detect various gases such as hydrogen, oxygen, and carbon dioxide. For example, Patent Document 1 proposes a hydrogen gas sensor using a metal oxide. Also, Patent Document 2 proposes an oxygen gas sensor and a carbon dioxide gas sensor using an oxygen ion conductor made of a solid electrolyte. Furthermore, Patent Document 3 proposes a gas sensor that detects oxidizing gases such as ozone using a gas-sensitive body made of a metal oxide. Also, Patent Document 4 proposes a gas sensor that detects gases using a sensitive portion produced by firing a metal oxide semiconductor paste mainly composed of zinc oxide particles.

[0003] In the hydrogen gas sensor described in Patent Document 1, a hydrogen detection layer is formed on a substrate, and a pair of electrodes is disposed on this hydrogen detection layer. The hydrogen detection layer includes a catalyst that dissociates hydrogen gas into protons and electrons, and a metal oxide whose electrical resistance decreases due to the electrons generated by the dissociation of hydrogen gas by the catalyst. The configuration is such that hydrogen gas is detected by a change in the electrical resistance between the pair of electrodes.

[0004] In the oxygen gas sensor and the carbon dioxide gas sensor described in Patent Document 2, an oxygen ion conductor made of a solid electrolyte is disposed on the surface of an insulating substrate (for example, an alumina substrate), and an oxygen detection electrode made of a noble metal, a carbon dioxide detection electrode covered with a metal carbonate, and a reference electrode shielded from the test gas are provided so as to contact the oxygen ion conductor.

[0005] In the gas sensor described in Patent Document 3, a gas sensor made of a metal oxide such as tin oxide, indium oxide, zinc oxide, tungsten oxide, or titanium oxide is placed on an insulating substrate on which a pair of electrodes are formed, and the amount of oxygen vacancies on the surface of the gas sensor is adjusted to a predetermined amount by exposing the gas sensor to an oxidizing gas and subjecting it to heat treatment.

[0006] In the gas sensor described in Patent Document 4, a sensing element is provided on the upper surface of an alumina substrate on which electrodes are formed, and the sensing element is made by firing a metal oxide semiconductor paste mainly composed of zinc oxide particles. The zinc oxide particles consist of ultrafine zinc oxide particles having an average particle diameter of 50 nm or less. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2018-004572 [Patent Document 2] Japanese Patent Application Publication No. 11-287785 [Patent Document 3] Japanese Patent Publication No. 2004-061306 [Patent Document 4] Patent No. 3933500 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, in the various gas sensors described in Patent Documents 1-4, the metal oxide or solid electrolyte that detects the gas is arranged on the surface of the substrate, resulting in a low degree of freedom in shape and a complex structure. Therefore, there were problems such as difficulty in manufacturing and difficulty in handling.

[0009] In particular, the hydrogen gas sensor described in Patent Document 1 required the inclusion of a catalyst (e.g., Ti) to dissociate hydrogen gas into protons and electrons, which led to problems such as increased manufacturing costs. Furthermore, the oxidizing gas sensor described in Patent Document 3 required the gas sensor to be exposed to the oxidizing gas and subjected to heat treatment to adjust the amount of oxygen vacancies on its surface, which resulted in increased manufacturing costs. Furthermore, the gas sensors described in Patent Documents 3 and 4 required a high-temperature process to form metal electrodes and metal oxides that acted as gas receptors, which led to problems such as increased manufacturing costs.

[0010] This invention has been made in view of the circumstances described above, and aims to provide a gas sensor that has a simple structure, low manufacturing cost, is easy to handle, and is capable of detecting gases. [Means for solving the problem]

[0011] To solve the above-mentioned problems, the gas sensor according to embodiment 1 of the present invention comprises a conductive porous body containing a conductor, a first electrode portion and a second electrode portion arranged at intervals in the extending direction of the conductive porous body, and a resistance measuring portion for measuring the electrical resistance value between the first electrode portion and the second electrode portion, wherein the conductive porous body serves as a gas detection portion for detecting gas, and zinc oxide is supported on the conductive porous body.

[0012] According to the gas sensor of embodiment 1 of the present invention, it has a conductive porous body in which a conductor is contained in an insulating porous body, and this conductive porous body serves as a gas detection unit for detecting gas, and zinc oxide is supported on the conductive porous body. In this case, in a conductive porous body containing a conductor, the electrical resistance changes when it comes into contact with a specific gas. Therefore, when the conductive porous body, which is the gas detection unit, is exposed to a specific gas, the electrical resistance of the conductive porous body changes. By measuring the electrical resistance between the first electrode and the second electrode using the resistance measuring unit, the gas can be detected.

[0013] Furthermore, since zinc oxide is supported on the conductive porous body, when exposed to oxygen gas, the zinc oxide reacts with oxygen, causing a significant change in electrical resistance, thus enabling accurate detection of oxygen gas. Furthermore, since a conductive porous material containing a conductor is used in an insulating porous material, a substrate for arranging carbon nanotubes, etc., is unnecessary, resulting in a simple structure and easy handling. In addition, because the structure is simple and catalysts are not required, manufacturing costs can be significantly reduced.

[0014] The gas sensor of embodiment 2 of the present invention is characterized in that, in the gas sensor of embodiment 1, the conductor is a thermoelectric material whose absolute value of the Seebeck coefficient is 3 μV / K or more. According to the gas sensor of aspect 2 of the present invention, the conductor contained in the insulating porous body is a thermoelectric material with an absolute value of Seebeck coefficient of 3 μV / K or more. Therefore, when the conductive porous body comes into contact with a specific gas, the electrical resistance value changes significantly. By measuring the electrical resistance value between the first electrode and the second electrode using the resistance measuring unit, the gas can be detected with high accuracy.

[0015] The gas sensor according to embodiment 3 of the present invention is characterized in that, in the gas sensor according to embodiment 1 or embodiment 2, the conductor is a carbon nanotube. According to the gas sensor of embodiment 3 of the present invention, since the conductive material contained in the insulating porous body is a carbon nanotube, the electrical resistance of the conductive porous body changes significantly when it comes into contact with a specific gas. By measuring the electrical resistance between the first electrode and the second electrode using the resistance measuring unit, the gas can be detected with high accuracy.

[0016] A gas sensor according to aspect 4 of the present invention is characterized in that, in the gas sensor according to aspect 1 or aspect 2, the conductor is an organic thermoelectric material. According to the gas sensor of Embodiment 4 of the present invention, since the conductor contained in the insulating porous body is an organic thermoelectric material, the porous body containing the conductor will have a large change in its electrical resistance value when it comes into contact with a specific gas. By measuring the electrical resistance value between the first electrode portion and the second electrode portion by the resistance measuring portion, gas detection can be performed with high accuracy.

[0017] The gas sensor of Embodiment 5 of the present invention is characterized in that, in the gas sensor of Embodiment 1 or Embodiment 2, the conductor is a nanotube or a nanowire made of a compound semiconductor or a silicon semiconductor. According to the gas sensor of Embodiment 5 of the present invention, since the conductor contained in the insulating porous body is a nanotube or a nanowire made of a compound semiconductor or a silicon semiconductor, the porous body containing the conductor will have a large change in its electrical resistance value when it comes into contact with a specific gas. By measuring the electrical resistance value between the first electrode portion and the second electrode portion by the resistance measuring portion, gas detection can be performed with high accuracy.

[0018] The gas sensor of Embodiment 6 of the present invention is characterized in that, in any one of the gas sensors of Embodiments 1 to 5, the insulating porous body is any one of paper, thread, non-woven fabric, cloth, and lead stick. According to the gas sensor of Embodiment 6 of the present invention, since the insulating porous body is any one of paper, thread, non-woven fabric, cloth, and lead stick (wick), a porous body containing a conductor can be easily produced by containing a conductor in these paper, thread, non-woven fabric, cloth, and lead stick (wick). Note that the paper in the present invention includes all those formed by papermaking, and the cloth in the present invention includes all those formed by weaving. In addition, the porous body containing the conductor can be surely brought into contact with the gas to be measured, and the gas can be detected with high accuracy. Furthermore, after use, the porous body containing the conductor can be incinerated and discarded, thereby reducing the environmental load.

Advantages of the Invention

[0019] According to the present invention, it is possible to provide a gas sensor that has a simple structure, a low manufacturing cost, is easy to handle, and can detect gas.

Brief Description of the Drawings

[0020] [Figure 1] It is a schematic explanatory view of a gas sensor which is an embodiment of the present invention. [Figure 2] It is a partially enlarged explanatory view of the conductor-containing porous body of the gas sensor shown in FIG. 1. [Figure 3] It is a schematic explanatory view of a method for manufacturing a conductor-containing porous body used in a gas sensor which is an embodiment of the present invention. [Figure 4] It is a graph showing the results of the examples.

Modes for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that each of the embodiments described below is specifically described in order to better understand the gist of the invention, and does not limit the present invention unless otherwise specified. In addition, the drawings used in the following description may show, for the sake of convenience, the main parts enlarged in order to make the features of the present invention easier to understand, and the dimensional ratios of each component are not necessarily the same as the actual ones.

[0022] As shown in FIG. 1, a gas sensor 10 according to an embodiment of the present invention includes a conductor-containing porous body 20 in which a conductor is contained in an insulating porous body, a first electrode portion 11 and a second electrode portion 12 disposed at intervals in the extending direction of the conductor-containing porous body 20, and a resistance measuring portion 15 that measures the electrical resistance between the first electrode portion 11 and the second electrode portion 12. In the present embodiment, the first electrode portion 11 is disposed at one end (the lower end in FIG. 1) of the conductor-containing porous body 20, and the second electrode portion 12 is disposed at the other end (the upper end in FIG. 1) of the conductor-containing porous body 20.

[0023] In this embodiment, the conductive porous body 20 described above is used as a gas detection unit that detects a specific gas. In this embodiment, as shown in Figure 2, zinc oxide 25 is supported on the conductive porous body 20. Here, since zinc oxide 25 reacts with oxygen gas and its electrical resistance changes significantly, the gas sensor in this embodiment is an oxygen gas sensor that detects oxygen gas in the gas detection unit.

[0024] As described above, the conductive porous body 20 is defined as an insulating porous body in which a conductor is incorporated. In this embodiment, the conductor is preferably a thermoelectric material with an absolute Seebeck coefficient of 3 μV / K or higher. This thermoelectric material has semiconductor properties, specifically those of a p-type or n-type semiconductor. In this embodiment, the conductive porous body 20 may be either a p-type or n-type semiconductor.

[0025] Thermoelectric materials with an absolute Seebeck coefficient of 3 μV / K or greater include (a) carbon nanotubes (CNTs), (b) organic thermoelectric materials, (c) nanotubes and nanowires made of compound semiconductors or silicon semiconductors, (d) noble metal compounds, (e) carbon materials, and (f) metals such as Bi, Co, Fe, and Ni. Furthermore, it is preferable that the thermoelectric material contained in the conductive porous body 20 has a Seebeck coefficient of 40 μV / K or higher in absolute value. Alternatively, the thermoelectric materials (a) to (f) may be used in combination.

[0026] Here, (a) in the case of carbon nanotubes, the conductive porous body 20 can be constructed by incorporating carbon nanotubes into an insulating porous body. The Seebeck coefficient of carbon nanotubes is approximately 5-170 μV / K.

[0027] (b) Examples of organic thermoelectric materials include PEDOT-based materials (PEDOT:PSS, PEDOT:Tos, etc.), π-conjugated nickel complex-based materials (poly(nickel-ethylenetetrathiolate)), and N-DMBI-based materials (N,N-dimethyl-2-phenyl-2,3-dihydro-1H-benzoimidazole). The Seebeck coefficient for PEDOT:PSS is approximately 10-100 μV / K. The Seebeck coefficient for PEDOT:Tos is approximately 40-210 μV / K. The Seebeck coefficient for π-conjugated nickel complex systems is approximately -16-140 μV / K. In the case of organic thermoelectric materials, a conductive porous body 20 can be constructed by incorporating the organic thermoelectric material into an insulating porous body.

[0028] (c) In the case of nanotubes or nanowires made of compound semiconductors or silicon semiconductors, the conductive porous body 20 can be constructed by incorporating one or more types of nanotubes or nanowires made of compound semiconductors or silicon semiconductors, such as boron nitride nanotubes, Si nanowires, or Bi2Te3 nanowires, into another porous body.

[0029] (d) Examples of noble metal compounds include copper compounds, silver compounds, gold compounds, platinum compounds, etc. Specifically, compounds of noble metal elements (Cu, Ag, Au, Pt) and S, Se, Te are preferred. In the case of noble metal compounds, a conductive porous body 20 can be constructed by incorporating the noble metal compound into an insulating porous body.

[0030] (e) Examples of carbon materials include carbon black and graphite. In the case of carbon materials, a conductive porous body 20 can be constructed by incorporating carbon material into an insulating porous body.

[0031] (f) In the case of metals such as Bi, Co, Fe, and Ni, the conductive porous body 20 can be constructed by incorporating the metal Bi, Co, Fe, Ni, etc. into the insulating porous body. It is preferable to incorporate the metal Bi, Co, Fe, Ni, etc. into the insulating porous body by a plating method.

[0032] In this embodiment, the conductive porous body 20 is an insulating porous body impregnated with carbon nanotubes (CNTs), and has semiconductor properties, specifically those of a p-type or n-type semiconductor. In this embodiment, the conductive porous body 20 may be either a p-type or n-type semiconductor.

[0033] As the insulating porous body, fibrous materials such as paper, yarn, nonwoven fabric, cloth, and lead sticks are preferred. In this embodiment, the insulating porous body is paper, and the conductive porous body 20 is CNT-containing paper. In other words, paper, which is an insulator, is used as the insulating porous body. Furthermore, the fibers used may be natural fibers or artificial fibers. Paper, thread, nonwoven fabric, cloth, reed sticks, etc., which are made by combining multiple fibers, may also be used.

[0034] As described above, in this embodiment, zinc oxide 25 is supported on the conductive porous body 20, as shown in Figure 2. There are no particular restrictions on the particle size of the supported zinc oxide 25, but it is preferable that it be in the range of 10 nm to 10 μm. Furthermore, there are no particular restrictions on the distribution amount of supported zinc oxide-25, but it should be 0.1 mg / cm³. 2 More than 1g / cm 2 It is preferable that the range be within the following limits.

[0035] Below, an example of a method for manufacturing the conductive porous body 20 (CNT-containing paper) described above will be explained with reference to Figure 3.

[0036] As shown in Figure 3(1), a pulp suspension in which pulp fibers are dispersed is obtained by adding pulp fibers to pure water and stirring thoroughly. Furthermore, as shown in Figure 3(2), a carbon nanotube dispersion is obtained by adding multi-walled carbon nanotubes to pure water and stirring thoroughly. In this case, it is preferable that the amount of multi-walled carbon nanotubes is 0.8% by mass or more and 3.2% by mass or less relative to the weight of the pulp fibers, which are the raw material for paper. In addition, a dispersant such as SDS (sodium dodecyl sulfate) may be added as needed. Furthermore, it is preferable to perform ultrasonic treatment for about 30 minutes when obtaining the carbon nanotube dispersion.

[0037] Next, as shown in Figure 3(3), the pulp suspension and the carbon nanotube dispersion are mixed and stirred to obtain a mixture. At this time, the carbon nanotubes will adhere to the pulp fibers. Next, as shown in Figures 3(4) and 3(5), the above-mentioned mixture is used in papermaking and dried to obtain CNT-containing paper. Next, a dispersion containing zinc oxide is prepared, and the CNT-containing paper is immersed in the zinc oxide dispersion and dried to support the zinc oxide on the CNT-containing paper. Through the process described above, a conductive porous body 20 on which zinc oxide 25 is supported can be manufactured.

[0038] There are no particular restrictions on the particle size of the zinc oxide particles dispersed in the zinc oxide dispersion described above, but it is preferable that it be within the range of 10 nm to 10 μm. Furthermore, there are no particular restrictions on the concentration of zinc oxide in the zinc oxide dispersion, but it is preferable that it be within the range of 0.1 g / L to 5 g / L. Furthermore, as a solvent for dispersing zinc oxide, for example, water, ethanol, styrene, DMF (dimethylformamide), ethyl violet, etc., can be used.

[0039] In the gas sensor 10 of this embodiment, when the conductive porous body 20 constituting the gas detection unit is exposed to oxygen gas, the zinc oxide 25 of the conductive porous body 20 comes into contact with the oxygen gas, causing a significant change in the electrical resistance value of the conductive porous body 20. Therefore, the resistance measuring unit 15 measures the electrical resistance between the first electrode unit 11 and the second electrode unit 12, and when the electrical resistance changes, it is determined that oxygen gas is present.

[0040] In this embodiment of the gas sensor 10, which has the configuration described above, there is a conductive porous body 20 containing a conductor in an insulating porous body. This conductive porous body 20 serves as a gas detection unit that detects gas, and zinc oxide 25 is supported on the conductive porous body 20. Therefore, when oxygen gas is present in the gas detection unit made of the conductive porous body 20, the zinc oxide 25 and oxygen react, causing a large change in electrical resistance, which makes it possible to detect oxygen gas with high accuracy. Furthermore, since a conductive porous material 20 containing a conductor is used in an insulating porous material, a substrate for arranging carbon nanotubes, etc., is unnecessary, resulting in a simple structure and easy handling. In addition, because the structure is simple and catalysts are not required, manufacturing costs can be significantly reduced.

[0041] Furthermore, in the gas sensor 10 of this embodiment, if the conductor is a thermoelectric material with an absolute Seebeck coefficient of 3 μV / K or higher, the electrical resistance of the conductive porous body 20 will change significantly when it comes into contact with a specific gas. By measuring the electrical resistance between the first electrode portion 11 and the second electrode portion 12 using the resistance measuring unit 15, oxygen gas can be detected with high accuracy.

[0042] Furthermore, in the gas sensor 10 of this embodiment, if the conductor is a carbon nanotube, the electrical resistance of the conductive porous body 20 will change significantly when it comes into contact with oxygen gas. By measuring the electrical resistance between the first electrode portion 11 and the second electrode portion 12 using the resistance measuring unit 15, oxygen gas can be detected with high accuracy.

[0043] Furthermore, in the gas sensor 10 of this embodiment, if the insulating porous body is one of the following: paper, yarn, nonwoven fabric, cloth, or lead stick, the conductive porous body 20 can be easily manufactured by incorporating a conductor into the paper, yarn, nonwoven fabric, cloth, or lead stick. Furthermore, the conductive porous body 20 constituting the gas detection unit can be reliably brought into contact with oxygen gas, enabling accurate detection of oxygen gas. Furthermore, after use, the conductive porous material 20 can be incinerated and disposed of, thereby reducing the environmental burden.

[0044] Although one embodiment of the present invention has been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical spirit of the invention.

[0045] For example, in this embodiment, a conductive porous material (CNT-containing paper) made of paper as the insulating porous material has been described, but it is not limited to this. The conductive porous material may also be made of yarn as the insulating porous material (for example, CNT-containing yarn), or of nonwoven fabric as the insulating porous material (for example, CNT-containing nonwoven fabric), or of cloth as the insulating porous material (for example, CNT-containing cloth), or of lead sticks as the insulating porous material (for example, CNT-containing lead sticks). Furthermore, conductive porous materials (CNT-containing yarns) can be manufactured by the following methods.

[0046] The method for incorporating carbon nanotubes into yarn is basically the same as manual dyeing techniques. One method involves immersing the base yarn in a carbon nanotube dispersion, then heating the dispersion to a temperature below boiling point (around 60°C) to evaporate the water, thereby coating the yarn with concentrated carbon nanotubes. This impregnation method allows for the incorporation of more carbon nanotubes into the yarn.

[0047] The base yarn (substrate) necessary for producing CNT-containing yarn is typically made from naturally derived yarns such as cotton, linen, wool, or silk, or from chemically synthesized synthetic fibers such as polyester or nylon. However, a blend of these yarns may also be used. In the case of yarns that do not absorb dye, such as synthetic fibers, a carbon nanotube dispersion may be applied to its surface and dried to produce a CNT-containing yarn.

[0048] Furthermore, in this embodiment, the method for supporting zinc oxide on a conductive porous material (CNT-containing paper) was described as immersing the conductive porous material (CNT-containing paper) in a zinc oxide dispersion and drying it. However, the method is not limited to this, and zinc oxide may be supported on the conductive porous material (CNT-containing paper) by other methods. For example, a white pigment containing zinc oxide may be applied to the surface of a conductive porous material (CNT-containing paper). Alternatively, a conductive porous material (CNT-containing paper) may be produced by preparing a mixture of a pulp suspension, a carbon nanotube dispersion, and a zinc oxide dispersion, and then papermaking and drying this mixture. [Examples]

[0049] The results of the verification experiments conducted to confirm the effects of the present invention are described below.

[0050] A pulp suspension containing dispersed pulp fibers (derived from eucalyptus) was prepared by adding pulp fibers to pure water and stirring thoroughly. Furthermore, a carbon nanotube dispersion was obtained by adding multi-walled carbon nanotubes (NC7000, manufactured by Nanocyl) and a dispersant (SDS: sodium dodecyl sulfate) to pure water and stirring thoroughly.

[0051] Next, the pulp suspension and the carbon nanotube dispersion were mixed and stirred to obtain a mixed solution. Next, the above-mentioned mixture was used to make paper, which was then dehydrated, heat-pressed, and dried to obtain CNT-containing paper. Then, the CNT-containing paper was immersed in nitric acid for one hour to remove the dispersant (SDS: sodium dodecyl sulfate) that inhibits conductivity.

[0052] In this example of the present invention, a dispersion of zinc oxide was prepared, and the CNT-containing paper described above was immersed in the zinc oxide dispersion and dried to support zinc oxide on the CNT-containing paper, thereby producing a conductive porous body on which zinc oxide was supported. In the comparative example, immersion in a dispersion containing zinc oxide was not performed, and therefore zinc oxide was not supported.

[0053] The first electrode portion and the second electrode portion were arranged in the fabricated conductive porous body to constitute the gas sensors of the present invention example and comparative example. The gas sensors of the present invention example and comparative example were placed inside a container, and the container was filled with 100% oxygen gas. The electrical resistance between the first electrode and the second electrode was then measured. The rate of change from the initial resistance value is shown in Figure 4.

[0054] In a comparative example where a conductive porous body without zinc oxide support was used as the gas detection unit, it was confirmed that the resistance value gradually decreased after oxygen gas was filled in. In contrast, in the present invention, where a conductive porous body supported with zinc oxide is used as the gas detection unit, it is confirmed that the resistance value rises immediately after oxygen gas is filled in, and then gradually decreases thereafter. Therefore, according to the present invention, it has been confirmed that oxygen gas can be detected in a short time by measuring the electrical resistance between the first electrode and the second electrode.

[0055] From the above, it has been confirmed that the present invention can provide a gas sensor that has a simple structure, low manufacturing cost, is easy to handle, and is capable of detecting gases. [Explanation of symbols]

[0056] 10 Gas sensors 11 First electrode part 12 Second electrode part 15 Resistance Measurement Section 20 Conductive material containing porous material 25. Zinc Oxide

Claims

1. The device comprises a conductive porous body containing a conductor, a first electrode portion and a second electrode portion arranged at intervals in the extending direction of the conductive porous body, and a resistance measuring unit for measuring the electrical resistance between the first electrode portion and the second electrode portion. A gas sensor characterized in that the conductive porous body serves as a gas detection unit for detecting gas, and zinc oxide is supported on the conductive porous body.

2. The gas sensor according to claim 1, characterized in that the conductor is a thermoelectric material whose absolute value of the Seebeck coefficient is 3 μV / K or more.

3. The gas sensor according to claim 1 or 2, characterized in that the conductor is a carbon nanotube.

4. The gas sensor according to claim 1 or 2, characterized in that the conductor is an organic thermoelectric material.

5. The gas sensor according to claim 1 or 2, characterized in that the conductor is a nanotube or nanowire made of a compound semiconductor or silicon semiconductor.

6. The gas sensor according to claim 1 or 2, characterized in that the insulating porous body is made of one of the following: paper, thread, nonwoven fabric, cloth, or lead stick.

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