gas sensor

Abstract

Provided is a gas sensor that has high sensitivity and responds at high speed. The gas sensor 1 is provided with sensitive parts 20 and a plurality of electrodes 21 arranged via the sensitive parts 20. The sensitive parts 20 each include an ionic liquid and are configured so that the electrical resistance thereof changes in response to adsorption of gas molecules G. The ionic liquid preferably includes a hydrophobic anion. The hydrophobic anion preferably includes an organic fluorine compound. The organic fluorine compound preferably has a trifluoromethyl group.

Description

[Technical Field]

[0001] This disclosure relates to a gas sensor, more particularly to a gas sensor comprising a sensing element and a plurality of electrodes arranged via the sensing element. [Background technology]

[0002] Patent Document 1 describes a sensor. This sensor includes a region of conductive organic material and a region of conductive material that is compositionally different from the conductive organic material. The sensor also provides an electrical path through the region of conductive organic material and the region of conductive material. The conductive organic material is selected from the group consisting of polyanilines, emeraldine salts of polyanilines, polypyrroles, polythiophenes, polyEDOTs, and derivatives thereof.

[0003] However, the sensor described in Patent Document 1 had a slow response speed, and sometimes required several minutes for a single measurement. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 2002-526769 [Overview of the project]

[0005] This disclosure aims to provide a gas sensor with a fast response speed.

[0006] A gas sensor according to one aspect of the present disclosure comprises a sensing element and a plurality of electrodes arranged via the sensing element. The sensing element contains an ionic liquid and is configured such that its electrical resistance changes when gas molecules are adsorbed upon it. [Brief explanation of the drawing]

[0007] [Figure 1]Figure 1A is a plan view showing the gas sensor according to this embodiment. Figure 1B is a perspective view showing the sensing part of the gas sensor according to this embodiment. [Figure 2] Figures 2A and 2B are explanatory diagrams illustrating the operation of the sensitive membrane described above. Figure 2C is a graph showing an example of the change in resistance over time obtained from the operation of the sensitive membrane described above. [Figure 3] Figure 3 is a schematic plan view showing the gas sensor used for the test described above. [Figure 4] Figure 4 is a graph showing the response waveform in Example 1 described above. [Figure 5] Figure 5 is a graph showing the sensitivity of Examples 1 and 2 and Comparative Example 1 described above. [Figure 6] Figure 6 is a graph showing the sensitivity of Examples 1-3 and Comparative Example 1 described above. [Modes for carrying out the invention]

[0008] (Embodiment 1) (1) Overview The gas sensor 1 according to this embodiment is, for example, an artificial olfactory sensor, and is used to detect, for example, odor component molecules as the gas molecules to be detected. Examples of odor component molecules include volatile organic compounds (VOCs) and ammonia, and the gas sensor 1 is used to detect these VOCs, etc. The gas sensor 1 detects VOCs, which are gas molecules of odor components contained in a sample gas such as gas collected from food, breath collected from the human body, or air collected from a room in a building. Note that the gas molecules to be detected by the gas sensor 1 are not limited to VOCs, and may include molecules of multiple types of odor components including VOCs, or molecules other than odor components, such as flammable gases, toxic gases such as carbon monoxide, etc.

[0009] Figure 1A shows a gas sensor 1 according to this embodiment. This gas sensor 1 comprises a sensing element 20 and a plurality of electrodes 21 on a substrate 120. The gas sensor 1 also has a plurality of sensing elements 20, and a plurality (for example, a pair) of electrodes 21 are arranged on each sensing element 20 via the sensing element 20. The plurality of sensing elements 20 are arranged in a row in the vertical and horizontal directions (four in this embodiment) to form an array. Each sensing element 20 is formed in a circular shape when viewed from above. Note that the number, arrangement, and shape of the sensing elements 20 in the gas sensor 1 are not limited to Figure 1A and can be appropriately changed depending on the type of gas sensor 1, etc.

[0010] As shown in Figure 1B, the sensing unit 20 comprises a gas adsorbent 201 and conductive particles 202. The sensing unit 20 is formed by dispersing a plurality of conductive particles 202 in a matrix of gas adsorbent 201. Each electrode 21 is electrically connected to the conductive particles 202 in the gas adsorbent 201. A pair of electrodes 21 are also electrically connected to the detection unit of the processing unit 13.

[0011] The gas adsorbent 201 is formed to adsorb the target gas molecules G. The gas adsorbent 201 also has electrical insulating properties and is formed from a gas adsorption material in the form of a film, plate, or sheet. The gas adsorption material constituting the gas adsorbent 201 contains an ionic liquid. The type of ionic liquid is selected according to the type of chemical substance (gas) to be adsorbed by the gas adsorbent 201, the type of conductive particles 202, and other factors.

[0012] The conductive particles 202 are particles that have conductivity. The sensing part 20 has conductivity by containing a plurality of conductive particles 202. The conductive particles 202 may include, for example, at least one material selected from the group consisting of carbon materials, conductive polymers, metals, metal oxides, semiconductors, superconductors, and complex compounds.

[0013] As shown in Figure 2A, before adsorbing gas molecules G, the sensing part 20 described above has a small thickness of gas adsorbent 201, and the multiple conductive particles 202 dispersed in the gas adsorbent 201 are densely packed. When gas molecules G are adsorbed onto the sensing part 20 from this state, the gas adsorbent 201 expands and its thickness increases, and as shown in Figure 2B, the multiple conductive particles 202 dispersed in the gas adsorbent 201 become sparsely packed. As a result, the spacing between the multiple conductive particles 202 dispersed in the gas adsorbent 201 widens, and as shown in Figure 2C, the resistance value of the sensing part 20 increases at t1 when gas molecules G are adsorbed. Furthermore, as the gas molecules G leave the sensing part 20, the gas adsorbent 201 contracts from a thick state (state in Figure 2B) to a thinner state (state in Figure 2A), and the resistance value gradually decreases from t2 when gas molecules G leave the sensing part 20. Then, by detecting this change in resistance value in the detection unit of the processing unit 13 which is electrically connected to the electrode 21, the gas sensor 1 can detect whether or not gas molecules G are present in the supplied gas such as air.

[0014] (2)Details As described above, the sensing part 20 of the gas sensor 1 according to this embodiment includes a gas adsorbent 201. The gas adsorbent 201 contains an ionic liquid. The ionic liquid is a liquid salt (low molecular weight) at room temperature and has less steric hindrance than the polymers conventionally used in the sensing parts of gas sensors. Therefore, the gas molecules G to be detected are easily adsorbed onto the gas adsorbent 201, and the gas molecules G adsorbed onto the gas adsorbent 201 are thought to diffuse rapidly within the gas adsorbent 201. Thus, the response speed of the gas sensor 1 can be increased. In addition, the gas adsorbent 201 containing the ionic liquid also allows for rapid detachment of gas molecules G. Therefore, in the gas sensor 1 of this embodiment, the ionic liquid, which is the gas adsorption material of the sensing part 20, rapidly adsorbs and desorbs gas molecules G, thereby reversibly causing a large structural change in the conductive particles.

[0015] In addition, since the ionic liquid has a low vapor pressure, there is almost no volatilization, and it is easy to maintain the shape of the sensitive part 20. Also, since the ionic liquid has high stability, there are few changes in its chemical structure and it is less likely to deteriorate. Furthermore, the properties of the ionic liquid can be changed by combinations of various cations and various anions, and by modification of each of the cations and anions. Therefore, theoretically, multiple types of ionic liquids can be composed of 16 combinations of 10 types of cations and anions. For this reason, if a plurality of gas adsorbents 201 are composed of combinations of different types of cations and anions, each gas adsorbent 201 is likely to adsorb different types of gas molecules G, which is advantageous for multi-channelization of the gas sensor 1. That is, the selectivity of the type of gas molecule G to be detected by the gas sensor 1 can be enhanced, and high discrimination of the type of gas molecule G becomes possible.

[0016] In this embodiment, examples of the cation (type) of the ionic liquid include imidazolium (5-membered ring, conjugated), piperidinium (6-membered ring, single bond), pyrrolidinium (5-membered ring, single bond), pyridinium (6-membered ring, conjugated), ammonium, sulfonium, phosphonium, etc. Also, in this embodiment, examples of the anion (type) of the ionic liquid include carboxylate ion, phosphate ion, sulfonate ion, tetrafluoroborate ion, trifluoromethyl group ([Tf2N] - , hydrophobic), hexafluorophosphate ion, trifluoromethanesulfonate ([TfO] - , hydrophobic), etc.

[0017] In this embodiment, it is preferable that the anion of the ionic liquid be a hydrophobic anion. This makes it difficult for water to adsorb onto the gas adsorbent 201 of the sensing part 20, thereby increasing the sensitivity of the gas sensor 1 to the gas molecules G to be detected. That is, although the atmosphere contains many water molecules (moisture) in addition to gas molecules G, these water molecules are in a much higher concentration than gas molecules G, and therefore tend to adsorb in large quantities onto the gas adsorbent 201. As a result, moisture affects the detection result of the gas sensor 1, making it difficult to obtain a response from the gas sensor 1 to the gas molecules G to be detected. Therefore, in this embodiment, by using a hydrophobic anion in the ionic liquid of the gas adsorbent 201, it is made difficult for water molecules to adsorb onto the gas adsorbent 201, and moisture does not affect the detection result of the gas sensor 1.

[0018] Here, hydrophobicity is considered almost synonymous with low hydrogen bond acceptance. Therefore, since the reactivity between water and ionic liquids largely depends on hydrogen bonding, it is thought that the reactivity can be suppressed by making the anions of the ionic liquid low hydrogen bond acceptance. In this case, the polarized -OH of water is the hydrogen bond donor, and the polarized N, O, F of the anion are the hydrogen bond acceptors. For hydrophobic anions, for example, it is preferable that the hydrogen bond acceptance parameter (β value) is less than 0.3, and it is thought that the smaller the β value, the less likely the anion is to form hydrogen bonds with water. There is no particular lower limit set for the β value; it is sufficient if it is greater than 0.

[0019] As the hydrophobic anion, it is preferable to use an organic fluorine compound. Thereby, the hydrogen bond accepting property of the hydrophobic anion becomes low, and the adsorption of moisture to the gas adsorbent 201 tends to be less. Further, as the organic fluorine compound used as the hydrophobic anion, it is preferable that the compound has a trifluoromethyl group. Thereby, the hydrogen bond accepting property of the hydrophobic anion becomes further low, and the adsorption of moisture to the gas adsorbent 201 tends to be even less. More specifically, examples of the compound having a trifluoromethyl group include bis(trifluoromethanesulfonyl)amide ion (see [Chemical Formula 1]). In addition, as the hydrophobic anion, it is preferable that the hydrophobic anion does not have a carboxyl group. Thereby, the hydrophobicity of the hydrophobic anion is easily obtained.

[0020]

Chemical Formula

[0021] In the present embodiment, it is preferable to use imidazolium as the cation of the ionic liquid. Further, it is preferable to use a cation having high hydrophobicity. For example, it is preferable that the imidazolium has an alkyl chain having 7 or more carbon atoms. The imidazolium used in the present embodiment is shown in [Chemical Formula 2].

[0022]

Chemical Formula

[0023] The ionic liquid constituting the gas adsorbent 201 can contain a cation and an anion at a certain ratio. For example, from the viewpoint of valence, the ionic liquid contains a monovalent anion and a cation in an equal ratio.

[0024] The sensing portion 20 of the gas sensor 1 according to this embodiment comprises a plurality of conductive particles 202. The plurality of conductive particles 202 are dispersed in a gas adsorbent 201. Preferably, the plurality of conductive particles 202 are made of, for example, carbon black. In this case, a change in the electrical resistance value of the sensing portion 20 is particularly likely to occur when the gas sensor 1 is exposed to gas. Preferably, the conductive particles 202 include an oxide semiconductor, and preferably, the oxide semiconductor is antimony tin oxide. In this case, a change in the electrical resistance value of the sensing portion 20 is particularly likely to occur when the gas sensor 1 is exposed to gas.

[0025] The average particle size of the conductive particles 202 is preferably, for example, 10 nm to 300 nm, in which case the dispersibility in the gas adsorbent 201 can be improved. The average particle size of the conductive particles 202 is the arithmetic mean of the particle size obtained from electron microscope images of the conductive particles 202, based on the number of particles.

[0026] The ratio of conductive particles 202 contained in the sensing part 20 is not particularly limited, but it is preferable that, for example, the ratio of conductive particles 202 to 100 parts by mass of gas adsorbent (ionic liquid) 201 is 200 parts by mass (conductive particles:ionic liquid in a mass ratio of 2:1). In this case, when the gas sensor 1 is exposed to gas, a change in the electrical resistance value of the sensing part 20 is particularly likely to occur.

[0027] The gas sensor 1 according to this embodiment is formed by providing a plurality of sensing parts 20 and a plurality of electrodes 21 on a substrate 120. Each sensing part 20 is electrically connected to a pair of electrodes 21 in contact with it. In manufacturing the gas sensor 1, the plurality of sensing parts 20 are formed on the substrate 120 on which the plurality of electrodes 21 are formed. Each sensing part 20 can be formed by applying a molding material containing an ionic liquid and conductive particles using a method such as inkjet or dispensing.

[0028] (3) Variant The embodiments described are merely one of many embodiments of the present disclosure. The embodiments can be modified in various ways depending on the design, etc., as long as they achieve the objectives of the present disclosure.

[0029] In the above description, the sensing unit 20 comprises an electrically insulating ionic liquid and conductive particles, and the sensing unit 20 is conductive due to the conductive particles, but it is not limited to this. For example, the sensing unit 20 does not have to contain conductive particles, in which case the ionic liquid contained in the gas adsorbent 201 is conductive. As the conductive ionic liquid, for example, an ionic liquid having various modifying groups can be used. When molecules of the gas to be detected are adsorbed onto the gas adsorbent 201, the gas adsorbent 201 expands, which changes the electrical resistance value of the sensing unit 20 between the multiple electrodes 21, and by measuring this change in electrical resistance value, the gas molecules G can be detected.

[0030] (Embodiment 2) The gas sensor 1 according to this embodiment differs from the gas sensor 1 according to Embodiment 1 in the composition of the ionic liquid.

[0031] In the following, components similar to those in Embodiment 1 will be denoted by common reference numerals, and their descriptions will be omitted as appropriate.

[0032] The configuration described in Embodiment 2 can be applied in appropriate combination with the configuration described in Embodiment 1 (including modified versions).

[0033] In Embodiment 1, the case in which the anions in the ionic liquid of the gas adsorbent 201 are hydrophobic anions was described in order to reduce the influence of moisture on the gas sensor 1. On the other hand, in Embodiment 2, the anions in the ionic liquid of the gas adsorbent 201 are formed to include hydrophilic anions so that the sensitivity of the gas sensor 1 is improved for a specific gas molecule G. Here, a hydrophilic anion is one that is hydrophilic and has higher hydrogen bond acceptance than the hydrophobic anion used in Embodiment 1. That is, it is preferable that the hydrophilic anion is an anion with a hydrogen bond acceptance parameter (β value) of 0.3 or higher. There is no particular upper limit set for the β value, but for example, it is 0.8 or lower.

[0034] For example, anions other than organofluorine compounds can be used as hydrophilic anions. In particular, anions that do not have a trifluoromethyl group can be used as hydrophilic anions. Specifically, examples of hydrophilic anions include halogen ions, nitrate ions, tetrafluoroborate ions, hexafluorophosphate ions, thiocyanate ions, alkyl sulfate ions, p-toluenesulfonate ions, and tetrafluoroacetate ions. In particular, the weakly hydrophilic anion hexafluorophosphate ion (PF6) - ), and PF6 - Tetrafluoroborate ions (BF4) have a higher hydrophilicity. - ) is preferably used.

[0035] When a hydrophilic anion is used as the anion in the ionic liquid of the gas adsorbent 201, the adsorption of gas molecules G, which are hydrogen bond donors, to the gas adsorbent 201 is improved. Therefore, the sensitivity of the gas sensor 1 to gas molecules G, which are hydrogen bond donors, is improved. Specifically, when gas molecules G are pyrrole, the adsorption to the gas adsorbent 201 is improved, and the detection sensitivity of the gas sensor 1 to pyrrole is improved. Therefore, in order to increase the detection sensitivity of gas molecules G, which are hydrogen bond donors, the gas sensor 1 can use a hydrophilic anion as the anion in the ionic liquid of the gas adsorbent 201.

[0036] Furthermore, the same cations as in Embodiment 1, such as imidazolium, can be used for the ionic liquid. In this embodiment, by using different anions with the same cation, ionic liquids with different properties can be easily prepared.

[0037] (Embodiment 3) In the gas sensor 1 according to this embodiment, when it has a plurality of sensing parts 20, the composition of the ionic liquid contained in the gas adsorbent 201 of each sensing part 20 differs from that of the gas sensor 1 according to embodiments 1 and 2.

[0038] In the following, components similar to those in Embodiments 1 and 2 will be denoted by common reference numerals, and their descriptions will be omitted as appropriate.

[0039] The configuration described in Embodiment 3 can be applied in appropriate combination with the configurations (including modified versions) described in Embodiments 1 and 2.

[0040] In this embodiment, when the gas sensor 1 has multiple sensing parts 20, the gas adsorbent 201 of each sensing part 20 can be formed using different ionic liquids. This makes it possible to make the types of gas molecules G adsorbed by the gas adsorbent 201 of each sensing part 20 different, thereby improving the detection sensitivity of the gas sensor 1 to multiple types of gas molecules G and facilitating multi-channel design.

[0041] For example, some of the multiple sensing parts 20 can form a gas adsorbent 201 using an ionic liquid containing hydrophobic anions, while other parts can form a gas adsorbent 201 using an ionic liquid containing hydrophilic anions. In this case, the sensing part 20 equipped with a gas adsorbent 201 containing hydrophilic anions can selectively detect gas molecules G of hydrogen bond donors such as pyrrole, while the sensing part 20 equipped with a gas adsorbent 201 containing hydrophobic anions can selectively detect gas molecules G other than hydrogen bond donors. [Examples]

[0042] Figure 3 shows a schematic diagram of the structure of the test gas sensor 1. This gas sensor 1 has a first electrode 211 and a second electrode 212 mounted on an electrically insulating substrate 120, forming a comb-shaped electrode system. The dimension L1 of the comb-shaped electrode system in the direction along the comb teeth is 520 μm, and the dimension L2 in the direction perpendicular to the comb teeth is 500 μm. Furthermore, an electrically insulating film (insulating film 9) is provided on the substrate 120 to cover the first electrode 211 and the second electrode 212. The insulating film 9 has a strip-shaped opening 7 with a width of 5 μm, as shown in Figure 3, which overlaps the first electrode 211 and the second electrode 212. The dimension L3 between the centers of the opening 7 shown in Figure 3 is 60 μm. Furthermore, a sensing part 20, equipped with a gas adsorbent 201 and conductive particles 202, is provided on the substrate 120 to cover the insulating film 9, with a thickness of 1 μm. Therefore, the sensing part 20 contacts the first electrode 211 and the second electrode 212 through the opening 7. The diameter D1 of the sensing part 20 shown in Figure 3 is 900 μm. The gas sensor 1 is also provided with a first terminal 81 extending from one end of the first electrode 211 and protruding to the outside of the sensing part 20, and a second terminal 82 extending from one end of the second electrode 212 and protruding to the outside of the sensing part 20.

[0043] With a constant voltage applied between the first terminal 81 and the second terminal 82, the gas sensor 1 was placed in a nitrogen gas stream, and then the target gas molecules G were introduced into the gas stream for approximately 15 seconds. During this process, the current flowing between the first terminal 81 and the second terminal 82 was measured, and the electrical resistance value of the sensing unit 20 was calculated from the results.

[0044] (Example 1) For the gas adsorbent 201 of the test gas sensor 1, imidazolium as the cation shown in [Chemical Formula 2] above was used as the ionic liquid, and the hydrophobic anion shown in [Chemical Formula 1] above was used as the anion. Carbon black with an average particle size of 44 nm was used as the conductive particles 202. The ratio of the gas adsorbent 201 to the conductive particles 202 constituting the sensing part 20 is 2:1 by mass ratio, with conductive particles:gas adsorbent = 2:1.

[0045] (Comparative Example 1) The test gas sensor 1 was formed in the same manner as in Example 1, except that the gas adsorbent 201 was formed from a polymer, specifically polysiloxane polymer (Sigma-Aldrich, trade name SP-2330).

[0046] Figure 4 shows the change in the electrical resistance value of the sensing element 20 (electrical resistance value between the first electrode 211 and the second electrode 212) for Example 1 and Comparative Example 1. Benzaldehyde was used as the gas molecule G to be detected, and the concentration was 10 ppm.

[0047] Comparing the changes in electrical resistance (response waveforms) between Example 1 and Comparative Example 1, Example 1 exhibits a steeper rise and fall in the waveform compared to Comparative Example 1. When the rise slope of each waveform was calculated using the Ramer-Douglas-Peucker algorithm, it was 0.89 for Example 1 and 0.31 for Comparative Example 1. Similarly, when the fall slope of each waveform was calculated using the same algorithm, it was 0.85 for Example 1 and 0.29 for Comparative Example 1. Therefore, Example 1, which uses an ionic liquid in the sensing part 20, has rise and fall slopes that are more than twice as steep as those of Comparative Example 1, which uses a polymer, indicating a faster response speed.

[0048] (Example 2) As the ionic liquid constituting the gas adsorbent 201, the cation used is imidazolium as shown in [Chemical Formula 2] above, and the anion is the weakly hydrophilic hexafluorophosphate ion (PF6 - ) was used. Otherwise, it was formed in the same manner as in Example 1.

[0049] For Examples 1 and 2 and Comparative Example 1, the sensitivity of the test gas sensor 1 was measured when an evaluation gas containing benzaldehyde at a concentration of 10 ppm was used as the target gas molecule G, and when air with 30% humidity was used as the evaluation gas. Sensitivity is defined as Rs / R0, where Rs is the resistance value measured at the sensing part 20 when the evaluation gas is introduced into the gas sensor 1, and R0 is the resistance value measured at the sensing part 20 when odorless gas (nitrogen) is introduced into the gas sensor 1.

[0050] As shown in Fig. 5, in Example 1, it can be seen that the sensitivity to benzaldehyde is higher than the sensitivity to moisture. On the other hand, in Example 2 and Comparative Example 1, it can be seen that the sensitivity to moisture is higher than the sensitivity to benzaldehyde. Therefore, by using a hydrophobic ionic liquid containing a hydrophobic anion as the ionic liquid included in the gas adsorbent 201, it can be said that the reactivity to moisture can be suppressed while maintaining the sensitivity to VOC (benzaldehyde).

[0051] (Example 3) As the ionic liquid constituting the gas adsorbent 201, imidazolium shown in the above [Chemical Formula 2] was used as the cation, and hydrophilic tetrafluoroborate ion (BF4 - ) was used as the anion. Otherwise, it was formed in the same manner as in Example 1.

[0052] For Examples 1 - 3 and Comparative Example 1, when an evaluation gas containing nonanal at a concentration of 2 ppm as the gas molecule G to be detected, when an evaluation gas containing benzaldehyde at a concentration of 2 ppm, and when an evaluation gas containing pyrrole at a concentration of 2 ppm were used, the sensitivity of the test gas sensor 1 was measured. The sensitivity was determined in the same manner as above.

[0053] As shown in Fig. 6, in Examples 1, 2 and Comparative Example 1, the sensitivity to the low-polarity molecule pyrrole is low, but in Example 3, the sensitivity to pyrrole was higher than that in Examples 1, 2 and Comparative Example 1. Therefore, by using a hydrophilic ionic liquid containing BF4 - with high hydrophilicity as the ionic liquid included in the gas adsorbent 201, it can be said that pyrrole can be detected with high sensitivity.

[0054] (Summary) As described above, the gas sensor (1) according to the first aspect includes a sensitive part (20) and a plurality of electrodes (21) arranged via the sensitive part (20). The sensitive part (20) contains an ionic liquid and is configured such that the electrical resistance changes when a gas molecule (G) is adsorbed.

[0055] According to this embodiment, the adsorption and desorption of gas molecules (G) in the sensing part (20) becomes faster, and the response speed of the gas sensor (1) becomes faster.

[0056] A second embodiment is a gas sensor (1) according to the first embodiment, wherein the sensing part (20) includes conductive particles (202) and is conductive due to the conductive particles (202).

[0057] According to this embodiment, the adsorption and desorption of gas molecules (G) in the sensing part (20) becomes faster, and consequently, the change in the electrical resistance value of the sensing part (20) due to the conductive particles (202) also becomes faster, and the response speed of the gas sensor (1) becomes faster.

[0058] A third embodiment is a gas sensor (1) according to the first or second embodiment, wherein the ionic liquid contains hydrophobic anions.

[0059] According to this embodiment, the responsiveness of the sensing element (20) to moisture is suppressed, and the detection sensitivity of the target gas molecule (G) is increased.

[0060] A fourth embodiment is a gas sensor (1) according to the third embodiment, wherein the hydrophobic anion includes an organofluorine compound.

[0061] According to this embodiment, the responsiveness of the sensing element (20) to moisture is further suppressed, and the detection sensitivity of the target gas molecule (G) is further increased.

[0062] The fifth aspect is a gas sensor (1) according to the fourth aspect, wherein the organofluorine compound has a trifluoromethyl group.

[0063] According to this embodiment, the responsiveness of the sensing element (20) to moisture is further suppressed, and the detection sensitivity of the target gas molecule (G) is further increased.

[0064] The sixth aspect is a gas sensor (1) according to the first aspect, wherein the ionic liquid contains hydrogen bond-accepting anions.

[0065] According to this embodiment, the adsorption of hydrogen bond-donating gas molecules G to the sensing part (20) is increased, and the detection sensitivity of hydrogen bond-donating gas molecules (G) is increased.

[0066] The seventh embodiment is a gas sensor (1) according to any one of the first to sixth embodiments, wherein the cation of the ionic liquid contains imidazolium.

[0067] According to this embodiment, the characteristics of the sensing element (20) are stabilized, and the detection sensitivity of gas molecules (G) is increased.

[0068] The eighth aspect is a gas sensor (1) according to any one of the first to seven aspects, comprising a plurality of sensing parts (20) of different types of ionic liquids. The plurality of sensing parts (20) are arranged in an array.

[0069] According to this embodiment, each of the multiple sensing elements (20) responds to different types of gas molecules (G), resulting in a multi-channel gas sensor (1) capable of detecting a wide variety of gas molecules (G).

[0070] The ninth aspect is a gas sensor (1) according to the eighth aspect, wherein a plurality of sensing parts (20) are each composed of an ionic liquid containing hydrophobic anions and an ionic liquid containing hydrophilic anions.

[0071] According to this embodiment, a gas sensor (1) can be obtained that has a fast response speed and high detection sensitivity for hydrogen bond-donating gas molecules (G).

[0072] The tenth embodiment is a gas sensor (1) according to any one embodiment of the second to ninth embodiments, wherein the conductive particles (202) are carbon black.

[0073] According to this embodiment, the characteristics of the sensing element (20) are stabilized, and the detection sensitivity of gas molecules (G) is increased.

[0074] The eleventh embodiment is a gas sensor (1) according to any one of the second to tenth embodiments, wherein the conductive particles (202) are an oxide semiconductor.

[0075] According to this embodiment, the characteristics of the sensing element (20) are stabilized, and the detection sensitivity of gas molecules (G) is increased.

[0076] The twelfth aspect is a gas sensor (1) according to the eleventh aspect, wherein the oxide semiconductor is antimony tin oxide.

[0077] According to this embodiment, the characteristics of the sensing element (20) are stabilized, and the detection sensitivity of gas molecules (G) is increased.

[0078] The thirteenth aspect is a gas sensor (1) according to the first aspect, wherein the ionic liquid is conductive.

[0079] According to this embodiment, the adsorption and desorption of gas molecules (G) in the sensing part (20) becomes faster, and the response speed of the gas sensor (1) becomes faster. [Explanation of Symbols]

[0080] 1. Gas sensor 20 Sensing part 202 Conductive particles 21 electrodes G gas molecule

Claims

1. It comprises a sensing element and a plurality of electrodes arranged via the sensing element, The sensing part contains an ionic liquid and is configured such that its electrical resistance changes when gas molecules are adsorbed. The sensing part includes conductive particles, and is conductive due to the conductive particles. The sensing part contains the conductive particles and the ionic liquid in a mass ratio of 2:

1. Gas sensor.

2. The ionic liquid contains a hydrophobic anion, The gas sensor according to claim 1.

3. The hydrophobic anion comprises an organofluorine compound. The gas sensor according to claim 2.

4. The organofluorine compound has a trifluoromethyl group, The gas sensor according to claim 3.

5. The ionic liquid contains an anion that accepts hydrogen bonds, The gas sensor according to claim 1.

6. The hydrogen bond acceptability parameter of the anion is less than 0.

3. The gas sensor according to claim 5.

7. The hydrogen bond accepting parameter of the anion is 0.3 or more and 0.8 or less. The gas sensor according to claim 5.

8. The cation of the ionic liquid contains imidazolium, The gas sensor according to any one of claims 1 to 7.

9. comprising a plurality of sensing parts of different types of ionic liquid, The plurality of sensing elements are arranged in an array. A gas sensor according to any one of claims 1 to 8.

10. Each of the plurality of sensing parts is composed of an ionic liquid containing hydrophobic anions and an ionic liquid containing hydrophilic anions, The gas sensor according to claim 9.

11. The conductive particles are carbon black, A gas sensor according to any one of claims 1 to 10.

12. The conductive particles include an oxide semiconductor, A gas sensor according to any one of claims 1 to 11.

13. The oxide semiconductor is antimony tin oxide, The gas sensor according to claim 12.

14. The ionic liquid is conductive, The gas sensor according to claim 1.

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