Semiconductor gas sensor, diaper, gas detection method, urine and / or feces detection method, method for determining when to change a diaper, and gas-responsive material

Abstract

The objective is to provide a semiconductor gas sensor capable of sensitively distinguishing and detecting ammonia gas and hydrogen sulfide gas without heating to high temperatures (approximately 180-300°C), a gas detection method using the same, a method for detecting diapers, urine and / or feces, a method for determining when to change diapers, and a gas-responsive material used in the above-mentioned semiconductor gas sensor. [Solution] A semiconductor gas sensor, a diaper, a gas detection method, a method for detecting urine and / or feces, a method for determining when to change a diaper, and a gas-responsive material, each comprising an electrode and a VO2(M1) phase-containing layer provided on the electrode, wherein the VO2(M1) phase functions as a gas-responsive material.

Description

[Technical Field]

[0001] This invention relates to a semiconductor gas sensor, a diaper, a gas detection method, a method for detecting urine and / or feces, a method for determining when to change a diaper, and a gas-responsive material. [Background technology]

[0002] Gas sensors are used to detect the presence or absence of gas, as well as its concentration. One type of gas sensor known is the semiconductor gas sensor (also called a "chemical resistance gas sensor"), which utilizes the change in electrical resistance resulting from the reaction between a gas-responsive material, such as a metal oxide semiconductor, and a gas. Due to its advantages such as excellent mass-producibility and relatively low manufacturing cost, semiconductor gas sensors are used in a variety of applications, such as alarms for various hazardous gases, portable sensors for detecting gas types in exhaled breath, odor sensors, and monitoring of the work environment.

[0003] Semiconductor gas sensors using n-type semiconductors exhibit decreased electrical resistance when exposed to reducing gases (electron-donating gases) and increased electrical resistance when exposed to oxidizing gases (electron-withdrawing gases). Conversely, semiconductor gas sensors using p-type semiconductors exhibit increased electrical resistance when exposed to reducing gases (electron-donating gases) and decreased electrical resistance when exposed to oxidizing gases (electron-withdrawing gases). Thus, the responsiveness (change in electrical resistance) of semiconductor gas sensors is determined by the type of metal oxide semiconductor (n-type or p-type) used as the gas-responsive material and the type of gas being detected (reducing or oxidizing). Therefore, technological development is underway to selectively detect specific gases using semiconductor gas sensors.

[0004] For example, Patent Document 1 describes the effects of flammable gases such as hydrogen and NO xA gas sensor is described that can reduce the influence of oxidizing gases such as [list of gases], and has improved detection sensitivity (gas sensitivity) and responsiveness to odorous gases compared to conventional sensors. This gas sensor has a gas detection layer containing SnO2 at a content of 90% by mass or more, and Ir, P, and Pt in specific content ratios. Furthermore, Patent Document 2 describes an ammonia gas sensor with high ammonia selectivity and improved measurement accuracy. This gas sensor comprises a first solid electrolyte layer mainly composed of one or more oxides selected from the group of V, Bi, and Sb (ammonia-selective oxides), and a reference electrode and a detection electrode formed on the surface of the first solid electrolyte layer. Furthermore, Patent Document 3 describes a semiconductor gas sensor that combines the operating principle of a semiconductor gas sensor (oxidation-reduction reaction on the gas sensor surface that occurs due to surface adsorption of gas) with a new gas detection principle (change in resistance switching characteristics at the electrode interface due to gas), thereby enabling the identification of hydrogen gas while maintaining the high sensitivity detection capability for a wide range of gas species of semiconductor gas sensors.

[0005] Semiconductor gas sensors generally do not react well with gases at room temperature, and in order to function as a high-sensitivity gas sensor as desired, the gas detection layer needs to be heated to a high temperature (approximately 180-300°C) to activate it. However, this high-temperature heating has been criticized for problems such as difficulty in miniaturizing the device and the possibility of delamination between the gas detection layer and the substrate. To solve this problem, it has been proposed, for example, as described in Patent Documents 4 and 5, to provide an adhesion layer that prevents delamination between the gas detection layer and the substrate.

[0006] Technology is being developed to detect the usage status of human care products such as diapers using various sensors. For example, Patent Document 6 describes a diaper change timing sensor equipped with a pair of electrodes for detecting urination, and states that by measuring the electrical characteristics (e.g., resistance and conductivity) between the electrodes using this diaper change timing sensor, the wetness of the diaper due to urination can be determined. Furthermore, Patent Document 7 describes an excretion detection device that separately includes a temperature detection means for detecting the temperature inside the diaper and a detection means for detecting the state of soiling of the diaper. Furthermore, Patent Document 8 describes the use of a gas sensor in addition to a moisture sensor for detecting urination, as a means for detecting defecation, which includes an element made of a heater and a sintered body of SnO2 as a metal oxide semiconductor. It also describes that this gas sensor enables highly sensitive detection of methyl mercaptan (methanethiol), which is the main component of the odor of feces. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2009 / 130884 [Patent Document 2] Japanese Patent Publication No. 2010-139238 [Patent Document 3] Japanese Patent Publication No. 2022-179881 [Patent Document 4] Japanese Patent Publication No. 2006-317155 [Patent Document 5] International Publication No. 2009 / 078370 [Patent Document 6] Japanese Patent Application Publication No. 9-033468 [Patent Document 7] Japanese Patent Application Publication No. 9-290001 [Patent Document 8] Japanese Patent Publication No. 2022-058409 [Non-patent literature]

[0008] [Non-Patent Document 1] JX Wang, XW Sun, et al. Nanotechnology, 2009, Vol. 20, p. 465501. [Non-Patent Document 2] M. Sinha, S. Neogi, et al. Sens. Actuators, B Chem. 2021, Vol. 336, p. 129729.

Summary of the Invention

Problems to be Solved by the Invention

[0009] The inventors have come up with the idea that if a technology capable of detecting urine and feces with the same sensor can be realized using a semiconductor gas sensor, it will be possible to develop a diaper product with unprecedented added value. However, as a semiconductor gas sensor, one that can distinguish between ammonia gas derived from urine and hydrogen sulfide gas derived from feces and selectively respond has not been known so far. Furthermore, as described above, a semiconductor gas sensor also requires high-temperature heating for activation of the gas sensing layer during gas sensing, and in a diaper product used at body temperature, it is difficult to realize a semiconductor gas sensor that can distinguish and detect urine and feces.

[0010] The present invention has been made in view of the above various circumstances, and an object thereof is to provide a semiconductor gas sensor capable of sensitively distinguishing and detecting ammonia gas and hydrogen sulfide gas without heating at a high temperature (approximately 180 to 300°C), and a gas detection method using the same. Another object of the present invention is to provide a diaper, a method for detecting urine and / or feces, and a method for determining the diaper replacement time, which enable detection of urine and feces without heating at a high temperature (approximately 180 to 300°C) by using the semiconductor gas sensor of the present invention. Another object of the present invention is to provide a gas-responsive material capable of sensitively distinguishing and detecting ammonia gas and hydrogen sulfide gas without heating at a high temperature (approximately 180 to 300°C).

Means for Solving the Problems

[0011] Some metal oxide semiconductors have been reported to exhibit gas responsiveness at relatively low temperatures. For example, Non-Patent Document 1 describes that ZnO, a typical p-type semiconductor, exhibits a p-type response to NO2 gas at temperatures below 100°C, and that this sensing behavior reverses at operating temperatures above 100°C. Furthermore, Non-Patent Document 2 states that the sensing behavior of ZnO / CNT composites for each gas can be reversed by temperature control. Based on the information described in Non-Patent Documents 1 and 2 above, the inventors considered that intrinsic semiconductor materials with narrow band gaps may also be able to modulate sensing behavior with temperature, and conducted further investigations. As a result, it was found that a semiconductor gas sensor using an n-type semiconductor VO2(M1) phase with a narrow band gap of 0.68 eV as the gas-responsive material exhibits a characteristic gas response (positive change in electrical resistance) to ammonia gas at a low temperature of 20°C, different from conventional semiconductor gas sensors. It was also found that it can sensitively distinguish and detect ammonia gas from hydrogen sulfide gas, etc., which exhibit a negative change in electrical resistance, without heating to high temperatures (approximately 180-300°C). The present invention was completed based on these findings and further investigations.

[0012] The above-mentioned problems of the present invention were solved by the following means. <1> A semiconductor gas sensor comprising an electrode and a VO2(M1) phase-containing layer provided on the electrode, wherein the VO2(M1) phase functions as a gas-responsive material. <2> The substrate has the electrode and the VO2(M1) phase-containing layer in this order. <1> The semiconductor gas sensor described above. <3> For distinguishing and detecting ammonia gas from at least one of the following gases: hydrogen sulfide, hydrogen, nitric oxide, toluene, acetone, and ethanol, <1> or <2> The semiconductor gas sensor described above. <4> For use at an operating temperature of 15-65°C, <1> ~ <3> A semiconductor gas sensor as described in one of the following documents. <5> Exposure to ammonia gas increases electrical resistance, while exposure to at least one of the following gases—hydrogen sulfide, hydrogen, nitric oxide, toluene, acetone, and ethanol—decreases electrical resistance. <1> ~ <4> A semiconductor gas sensor as described in one of the following documents. <6> The substrate is a flexible substrate. <2> The semiconductor gas sensor described above. <7> For use in detecting urine and / or feces, <5> The semiconductor gas sensor described above. <8> Designed to be attached to a diaper, <7> The semiconductor gas sensor described above. <9> <8> A diaper equipped with a semiconductor gas sensor as described above. <10> <1> ~ <8> A gas detection method that uses a semiconductor gas sensor described in any one of the above to distinguish and detect ammonia gas from at least one of the following gases: hydrogen sulfide, hydrogen, nitric oxide, toluene, acetone, and ethanol. <11> <1> ~ <8> A method for detecting urine and / or feces, which distinguishes between urine and feces and detects them using a semiconductor gas sensor described in any one of the above. <12> <7> A method for determining when to change a diaper, comprising detecting ammonia gas derived from urine and / or hydrogen sulfide gas derived from feces excreted in a diaper using a semiconductor gas sensor as described above, thereby determining when to change the diaper. <13> A gas-responsive material containing the VO2(M1) phase as an active ingredient. <14> For distinguishing and detecting ammonia gas from at least one of the following gases: hydrogen sulfide, hydrogen, nitric oxide, toluene, acetone, and ethanol, <13> The gas-responsive material described in [reference]. <15> For use in detecting urine and / or feces, <14> The gas-responsive material described in [reference].

[0013] In this invention, a numerical range represented using "~" means a range that includes the numbers written before and after "~" as the lower limit and upper limit, respectively. [Effects of the Invention]

[0014] According to the semiconductor gas sensor and gas detection method using the present invention, ammonia gas and hydrogen sulfide gas, etc., can be detected with high sensitivity without heating to high temperatures (approximately 180-300°C). Furthermore, according to the present invention's method for detecting diapers, urine and / or feces, and method for determining when to change a diaper, the semiconductor gas sensor of the present invention can distinguish and detect urine and feces without heating to high temperatures (approximately 180-300°C). Furthermore, the gas-responsive material of the present invention enables sensitive differentiation and detection of ammonia gas, hydrogen sulfide gas, and the like without heating to high temperatures (approximately 180-300°C). [Brief explanation of the drawing]

[0015] [Figure 1] The XRD patterns of the single-phase VO2(M1) powder obtained in Synthesis Example 1 (under a nitrogen gas atmosphere) are shown. The upper pattern is the XRD pattern of the single-phase VO2(M1) powder, and the lower pattern is the XRD pattern theoretically calculated based on a crystal structure model for the measured diffraction pattern using Rietveld analysis. [Figure 2]The XRD patterns of the powders obtained in Synthesis Example 1 (under air) are shown. Figure 2(a) is at 310°C, Figure 2(b) at 360°C, Figure 2(c) at 410°C, Figure 2(d) at 460°C, and Figure 2(e) at 490°C, showing the XRD patterns of powders obtained by performing chemical reactions in subcritical fluid or supercritical fluid (subcritical water or supercritical water), respectively. Figures 2(c) to (e) show the XRD patterns of powders with a mixed phase of VO2(M1) and V6O13. At the bottom of Figure 2, the XRD patterns of the VO2(M1) phase (ICDD No. 43-1051 VO2(M1)) and V6O13 (ICDD No. 43-1050 V6O13) registered in ICDD (International Centre for Diffraction Data) are shown superimposed. Peaks characteristic of the VO2(M1) phase are indicated by ●, and peaks characteristic of V6O13 are indicated by ▼. [Figure 3] Figure 3(a) shows the XRD pattern of the VO2(M1) phase registered in the ICDD (ICDD No. 43-1051 VO2(M1)), and Figure 3(b) shows the XRD pattern of the VO2(B) phase registered in the ICDD (ICDD No. 81-2392 VO2(B)). [Figure 4] These are photographs serving as drawings of the flexible comb-shaped electrode sheet fabricated in the example. Figure 4(a) is a photograph of the comb-shaped electrode sheet folded along its long axis, and Figure 4(b) is a photograph of the comb-shaped electrode sheet folded perpendicular to its long axis. [Figure 5] This is a photograph serving as a substitute for a drawing of the semiconductor gas sensor chip fabricated in the example. [Figure 6] This graph shows the gas response results for various gas species at 20°C using a semiconductor gas sensor with a single-phase VO2(M1) sensing layer. The vertical axis represents the response ΔR / R (Response (%)). From top to bottom, the graph shows the gas response to each gas species indicated in the figure: NH3 (ammonia) gas, H2S (hydrogen sulfide) gas, H2 (hydrogen) gas, NO (nitric oxide) gas, toluene gas, acetone gas, and ethanol gas. [Figure 7]This graph shows the gas response results for various gas types at 20°C using a semiconductor gas sensor with a single-phase VO2(M1) sensing layer. The vertical axis represents electrical resistance (Rgas) (Resistance (Ω)). The gas concentrations for each gas type are the same as those shown in Figure 6. [Figure 8] This bar graph shows the gas response results for various gas species at 20°C, 30°C, and 40°C for a semiconductor gas sensor using a single-phase VO2(M1) sensing layer. Each region separated by a straight line shows, from left to right, the gas response at 20°C, 30°C, and 40°C, respectively. The seven bar graphs in each region show, from left to right, the gas response for 24.7 ppm NH3 gas, 5.00 ppm H2S gas, 0.97 ppm H2 gas, 2.93 ppm NO gas, 99.7 ppm toluene gas, 99.7 ppm ethanol gas, and 101 ppm acetone gas, respectively. [Figure 9] Figures 9(a) to 9(g) are graphs showing the gas response results for various gas species at 20°C using a semiconductor gas sensor with a mixed phase layer of VO2(M1) and V6O13 as the sensing layer. The vertical axis represents the response ΔR / R (Response (%)). From top to bottom, Figure 9(a) shows the gas response to NH3 gas, Figure 9(b) shows the gas response to H2S gas, Figure 9(c) shows the gas response to H2 gas, Figure 9(d) shows the gas response to NO gas, Figure 9(e) shows toluene gas, Figure 9(f) shows acetone gas, and Figure 9(g) shows ethanol gas, at the concentrations indicated in the figures. [Figure 10]This radar chart shows the gas response results for various gas species at 20°C, 30°C, 40°C, 50°C, and 60°C of a semiconductor gas sensor using a mixed phase layer of VO2(M1) and V6O13 as the sensing layer. The response ΔR / R (Response (%)) for each gas species at 24.7 ppm NH3 gas, 5.00 ppm H2S gas, 0.97 ppm H2 gas, 2.93 ppm NO gas, 99.7 ppm toluene gas, 101 ppm acetone gas, and 99.7 ppm ethanol gas is shown at 20°C (■), 30°C (●), 40°C (▲), 50°C (▼), and 60°C (◆). [Figure 11] This graph shows the response of the diaper sensor (inside mode) to three deliveries of 40 mL of 38°C artificial urine at 25°C. The vertical axis represents the response ΔR / R (Response (%)). The timing of the artificial urine delivery is indicated by the arrows. [Figure 12] This graph shows the response of the diaper sensor (inside mode) to three applications of 5 ppm H2S gas at 25°C. The vertical axis represents the response ΔR / R (Response (%)). The timing of the H2S gas application is indicated by the arrows. [Figure 13] This graph shows the response of a diaper sensor (outside mode) to three 40 mL doses of 38°C artificial urine at 25°C. The vertical axis represents the response ΔR / R (Response (%)). The timing of the artificial urine supply is indicated by arrows. [Figure 14] This graph shows the response of a diaper sensor (outside mode) to the simultaneous supply of 5 ppm H2S gas and 40 mL of 38°C artificial urine three times at 25°C. The vertical axis represents the response ΔR / R (Response (%)). The timing of the supply of H2S gas and artificial urine is indicated by arrows. [Modes for carrying out the invention]

[0016] Preferred embodiments of the present invention are described below, but the present invention is not limited to the embodiments described below other than those specified herein.

[0017] [Semiconductor gas sensor] The semiconductor gas sensor of the present invention comprises an electrode and a VO2(M1) phase-containing layer provided on the electrode, wherein the VO2(M1) phase functions as a gas-responsive material. In other words, the semiconductor gas sensor of the present invention is a gas sensor that utilizes the fact that the electrical resistance of the gas sensor changes in a gas type-dependent manner due to the reaction between the VO2(M1) phase, which is a metal oxide semiconductor, and the gas.

[0018] In this invention, "VO2(M1) phase" refers to VO2 (Monoclinic, P21 / c), an n-type semiconductor that undergoes a reversible metal-semiconductor transition (MST) with the metallic phase VO2(R) at approximately 68°C. The fact that VO2(M1) phase is an n-type semiconductor is described in A. Patel, et al. Superlattices Microst. 2019, Vol. 130, pp. 160-167, and Y. Zhou, et al. J. Appl. Phys. 2013, Vol. 113, pp. 213703. In addition to the VO2(M1) phase mentioned above, another known metal oxide semiconductor of VO2 is the VO2(B) phase. This VO2(B) phase is VO2(Monoclinic, C2 / m) and transitions to the metallic phase VO2(R) at approximately 480°C. In the VO2(B) phase, it is known that at 20°C, the electrical resistance of the VO2(B) phase increases upon contact with any of the reducing gases: ammonia, hydrogen sulfide, acetone, ethanol, and toluene (see VX Hien, et al., J. Mater. Sci., 2021, Vol. 32, pp. 13803-13812). In contrast, the semiconductor gas sensor of the present invention, for example, when using a single phase of VO2(M1) as the gas-responsive material, exhibits a decrease in electrical resistance upon contact with reducing gases such as hydrogen sulfide, hydrogen gas, toluene, acetone, and ethanol, as well as an oxidizing gas such as nitric oxide, at least at 20 to 40°C, while its electrical resistance increases upon contact with a reducing gas such as ammonia (see Example 1(1) below). Furthermore, the VO2(M1) phase and V6O 13 When using a mixed phase, at least at 20-60°C, the electrical resistance decreases upon contact with reducing gases such as hydrogen sulfide, hydrogen gas, toluene, acetone, and ethanol, as well as the oxidizing gas nitric oxide, while the electrical resistance increases upon contact with the reducing gas ammonia (see Example 1(2) below). Compared to a single VO2(M1) phase, the VO2(M1) phase and V6O 13 The reason why the temperature range over which responsiveness to gas species is maintained in the mixed phase is, although speculative, V6O 13 It is thought that the mixed phase with V6O may be related to the fact that the Schottky barrier, described later, becomes larger compared to the case of a single VO2(M1) phase, and V6O 13 It is believed that similar phenomena may occur in mixed phases with other vanadium oxides.

[0019] The reason why the above-mentioned reversal of gas response due to temperature occurs in the semiconductor gas sensor of the present invention is thought to be as follows. When a metallic electrode comes into contact with an n-type semiconductor VO2(M1) phase, a Schottky junction may be formed at the interface between the electrode and the VO2(M1) phase. When the semiconductor gas sensor of the present invention comes into contact with ammonia gas, the adsorption of ammonia gas reduces the electron affinity (and work function) of the VO2(M1) phase, causing the Schottky barrier (a value calculated by subtracting the electron affinity of the VO2(M1) phase-containing layer from the work function of the electrode) to exceed 0 (resulting in Schottky contact), which is thought to increase resistance. On the other hand, when the semiconductor gas sensor of the present invention comes into contact with hydrogen sulfide gas, hydrogen gas, nitric oxide gas, toluene gas, acetone gas, or ethanol gas, the decrease in electron affinity (and work function) of the VO2(M1) phase surface due to gas adsorption is less likely to occur, and the Schottky barrier becomes less than 0 (resulting in ohmic contact), which is thought to decrease resistance. In the following description, "hydrogen sulfide gas, etc." refers to "at least one of the following gases: hydrogen sulfide gas, hydrogen gas, nitric oxide gas, toluene gas, acetone gas, and ethanol gas."

[0020] In other words, when the semiconductor gas sensor of the present invention is exposed to hydrogen sulfide gas or the like, a change occurs in the electron affinity of the VO2(M1) phase-containing layer, and the Schottky barrier of the Schottky junction formed between the VO2(M1) phase-containing layer and the electrode becomes less than 0 (ohmic contact). On the other hand, when exposed to ammonia gas, a different change occurs in the electron affinity of the VO2(M1) phase-containing layer, and the Schottky barrier becomes greater than 0 (Schottky contact). As a result of the above, the semiconductor gas sensor of the present invention exhibits decreased electrical resistance when exposed to hydrogen sulfide gas, etc., and increased electrical resistance when exposed to ammonia gas.

[0021] As described above, the semiconductor gas sensor of the present invention can be used as a semiconductor gas sensor for distinguishing and detecting hydrogen sulfide gas and ammonia gas.

[0022] (Gas-responsive materials) The VO2(M1) phase-containing layer is not particularly limited as long as it contains the VO2(M1) phase and functions as a gas-responsive material. For example, it may be a single-phase VO2(M1) layer, or it may be a layer containing the VO2(M1) phase and components other than the VO2(M1) phase. Examples of components other than the VO2(M1) phase include vanadium oxide other than the VO2(M1) phase (referred to as "other vanadium oxide"). The aforementioned other vanadium oxides may be compounds or composite compounds thereof that have a crystalline structure such as a monoclinic phase or a tetragonal phase and contain the element vanadium. For example, V6O 13 Examples include vanadium oxide doped with cations such as W and Mo, or anions such as N, B and P, in the form of V2O5, V4O9, VO, VO2(B) phase, VO2(A) phase, or NH4VO3, or any of these. The content of the VO2(M1) phase in the VO2(M1) phase-containing layer is not particularly limited as long as it functions as a gas-responsive material and the effects of the present invention are achieved. For example, a molar ratio of VO2(M1) phase:other vanadium oxides = 1:99 to 100:0 is preferred, and VO2(M1) phase:other vanadium oxides = 35:65 to 100:0 is more preferred. For a mixed phase layer of VO2(M1) phase and other vanadium oxides, a ratio of VO2(M1) phase:other vanadium oxides = 40:60 to 80:20 is even more preferred. Note that VO2(M1) phase:other vanadium oxides = 100:0 means that the VO2(M1) phase-containing layer is a single-phase layer of VO2(M1) phase. The VO2(M1) phase content in the VO2(M1) phase-containing layer is calculated by performing powder X-ray diffraction (XRD) on the VO2(M1) phase-containing layer and determining the ratio of the peak areas with the strongest intensity for each phase.

[0023] In the semiconductor gas sensor of the present invention, the VO2(M1) phase functions as a gas-responsive material and, upon contact with the gas to be detected, detects the presence or absence of a specific gas species in the target gas based on the gas response pattern of the semiconductor gas sensor. In the present invention, "detection" is not limited to determining the presence or absence of a specific gas species, but also includes predicting (estimating) the presence or absence of a specific gas species with a desired accuracy. Furthermore, in the present invention, "presence" in the "presence or absence" of a specific gas species may mean that the specific gas species simply exists, or it may mean that the specific gas species is present in a certain amount (certain concentration) or more, in addition to simply existing. Similarly, "absence" may mean that the specific gas species is not present at all (below the detection limit), or that even if the specific gas species is present, its amount (concentration) is below a certain amount (certain concentration). Thus, the criteria for "presence or absence" are set appropriately according to the purpose.

[0024] The semiconductor gas sensor of the present invention exhibits no change in its response pattern to hydrogen sulfide gas and other gases, as well as to ammonia gas, in the temperature range of at least 15 to 45°C (at least 15 to 65°C in the case of a mixed phase of VO2(M1) phase and other vanadium oxides), which is close to the human body temperature. Therefore, it can be suitably used as a sensor for human healthcare applications such as diapers. The statement that the above response pattern does not change means that the sensing behavior of the semiconductor gas sensor of the present invention when exposed to gas, that is, the behavior of the response ΔR / R (Response (%)) represented by equation (A) described later, does not change whether it is upward or downward. Specifically, the response pattern to hydrogen sulfide gas, etc., always shows downward behavior (n-type response: decrease in electrical resistance) within the above temperature range, and the response pattern to ammonia gas always shows upward behavior (p-type response: increase in electrical resistance) within the above temperature range. The semiconductor gas sensor of the present invention can be used with an operating temperature of, for example, 15 to 45°C (for example, 15 to 65°C in the case of a mixed phase of VO2(M1) phase and other vanadium oxides).

[0025] The semiconductor gas sensor of the present invention can detect specific gas species in the target gas, but the detectable concentration range varies depending on the gas species, the environment in which it is used, etc. For example, it can detect ammonia gas in a concentration range of 2.5 to 18,000 ppm, and hydrogen sulfide gas and the like can be detected in a concentration range of 0.1 to 10,000 ppm.

[0026] Contact between the semiconductor gas sensor of the present invention and the gas to be detected can be achieved by the gas reaching the semiconductor gas sensor through natural diffusion.

[0027] The semiconductor gas sensor of the present invention typically has a configuration in which a VO2(M1) phase-containing layer is provided on an electrode in contact with the electrode. Other configurations are not particularly limited, and configurations commonly used in semiconductor gas sensors can also be adopted in the semiconductor gas sensor of the present invention.

[0028] (electrode) The electrodes can be any electrodes usable in semiconductor gas sensors without any particular limitations. From the viewpoint of making the gas response due to the positive or negative Schottky barrier more apparent, it is preferable that the electrodes be made of a metal with a work function of 3.20 to 5.44 eV (preferably 4.05 to 4.80 eV). Specific examples include silver, molybdenum, iron, platinum, and gold.

[0029] The semiconductor gas sensor of the present invention preferably has a layer configuration in which the electrode and the VO2(M1) phase-containing layer are arranged on a substrate in that order. As for the substrate, any substrate commonly used in semiconductor gas sensors can be used without any particular limitations. In particular, it is more preferable that the substrate is a flexible substrate, that is, that the electrode and the VO2(M1) phase-containing layer are provided on the flexible substrate in this order. The materials constituting the flexible substrate are not particularly limited as long as they are insulating materials, and those that are water-soluble and biodegradable are preferred. Examples include cellulose derivatives such as HPMC (hydroxypropyl methylcellulose), polyesters, and polyamides. When the substrate is a flexible substrate, the semiconductor gas sensor of the present invention can be used as a flexible, compact semiconductor gas sensor. For example, it can be suitably used as a semiconductor gas sensor attached to a diaper for detecting urine and / or feces. There are no particular limitations on the size of the semiconductor gas sensor chip of the present invention. When used as a small semiconductor gas sensor, for example, the sensor can have dimensions of 10 to 50 mm in length, 5 to 100 mm in width, and 1 to 10 μm in thickness.

[0030] [Gas-responsive materials] The gas-responsive material of the present invention has VO2(M1) phase as an active ingredient. The VO2(M1) phase is as described above for the VO2(M1) phase in the semiconductor gas sensor of the present invention. The VO2(M1) phase may be a single phase of VO2(M1), or it may be a mixed phase of the VO2(M1) phase in the semiconductor gas sensor of the present invention described above and other vanadium oxides. The gas-responsive material of the present invention can be used as a gas-responsive material for distinguishing and detecting ammonia gas and hydrogen sulfide gas, etc. That is, when the gas-responsive material of the present invention is used on an electrode, the response pattern to hydrogen sulfide gas, etc. shows downward behavior (n-type response: decrease in electrical resistance), and the response pattern to ammonia gas shows upward behavior (p-type response: increase in electrical resistance), so it can be used as a material that exhibits gas-selective responsiveness.

[0031] The gas-responsive material of the present invention can be used as a gas-responsive material for detecting urine and / or feces. Urea, which makes up about 1.7-1.8% of urine, is known to be broken down into ammonia by bacteria. In addition, volatile gases derived from feces contain about 1% hydrogen sulfide gas. Therefore, by using the gas-responsive material of the present invention, which can distinguish and detect ammonia gas and hydrogen sulfide gas, it is possible to distinguish and detect urine and feces.

[0032] The following are some of the advantages of the semiconductor gas sensor of the present invention: (1) to (5). (1) It can easily distinguish and detect urine and feces without requiring complex analysis, and the condition of the diaper can be determined by the opposite response patterns of ammonia gas and hydrogen sulfide gas (n-type response and p-type response). (2) It is low-cost and reusable. (3) Semiconductor gas sensors can operate without being heated to high temperatures, thus eliminating the need for a heating device. Therefore, the temperature control heater required for conventional semiconductor gas sensors can be omitted. Because a temperature control heater is not required, semiconductor gas sensors can be miniaturized, and organic substrates with low heat resistance can be used. As a result, it becomes possible to create small semiconductor gas sensors using flexible substrates. (4) The sensor chip is highly flexible and has excellent biocompatibility and fitting properties, so when used attached to a diaper, the feeling of a foreign object is greatly reduced. (5) Since water-soluble substrates can also be used, they are easy to decompose and environmentally friendly. The semiconductor gas sensor of the present invention is not particularly limited in its applications and can be used in applications where gas sensors have been used to date. In light of (1) to (5) above, it is particularly suitable for use as a semiconductor gas sensor in human care devices such as diapers. Specifically, by equipping diapers worn by elderly people requiring care who have difficulty communicating verbally, or infants, with the semiconductor gas sensor of the present invention, urine and feces can be detected independently. Furthermore, centralized monitoring by a nurse station, alerts for different types of excretions using different music, and in the future, alerts via smartphones are also envisioned.

[0033] (Manufacturing method for semiconductor gas sensors) The semiconductor gas sensor chip of the present invention can be obtained by conventional methods known as methods for manufacturing semiconductor gas sensors using metal oxide semiconductors, without any particular limitations. For example, a semiconductor gas sensor can be obtained by adding a VO2(M1) phase to a solvent such as ethanol, dispersing it using ultrasound to prepare a slurry, then dropping the slurry onto a comb-shaped electrode using a pipette or the like, and finally drying the dropped slurry in a drying oven at 30-100°C to remove the solvent.

[0034] (Method for preparing gas-responsive materials) The VO2(M1) phase can be prepared, for example, by the following method. First, a precursor is prepared by mixing a reducing agent such as hydrazine into a mixed solution of hydrogen peroxide solution and V2O5. The obtained precursor is dispersed in a solvent such as water, and VO2 (M1 phase) can be obtained by carrying out a chemical reaction in a subcritical fluid and / or supercritical fluid (preferably in subcritical water and / or supercritical water). A single-phase VO2(M1) can be obtained by carrying out the above-mentioned chemical reactions in a subcritical fluid and / or supercritical fluid under an inert gas atmosphere such as argon gas or nitrogen gas. A mixed phase of VO2(M1) phase and other vanadium oxides can be obtained by carrying out the above-mentioned chemical reactions in a subcritical fluid and / or supercritical fluid under a gas atmosphere containing oxygen gas (e.g., under air). Furthermore, the proportion of the VO2(M1) phase in the mixed phase of the VO2(M1) phase and other vanadium oxides can be adjusted by adjusting the temperature at which the above-mentioned chemical reactions are carried out in the subcritical fluid and / or supercritical fluid. As shown in Figure 2, as the temperature at which the above-mentioned chemical reactions are carried out in the subcritical fluid and / or supercritical fluid increases, the proportion of other vanadium oxides, such as V6O, increases. 13 The transition to the VO2(M1) phase is promoted. Furthermore, the chemical reactions in the subcritical fluid and / or supercritical fluid described above are preferably chemical reactions in a supercritical fluid. In addition to the above, any other necessary treatments, such as purification, may be performed as appropriate.

[0035] [Diapers] The diaper of the present invention is equipped with the semiconductor gas sensor of the present invention. With regard to diapers other than the semiconductor gas sensor of the present invention, commercially available products can be used without particular restrictions, and the method of fixing to the diaper can also be done by a normal fixing method without particular restrictions, as long as urine and / or feces can be detected. The diaper of the present invention can detect urine and / or feces whether the semiconductor gas sensor of the present invention is provided on the inside (body side) or outside of the diaper.

[0036] [Gas detection method] The gas detection method of the present invention is a method for distinguishing and detecting ammonia gas and hydrogen sulfide gas, etc., using the semiconductor gas sensor of the present invention. The environmental conditions for gas detection (temperature, concentration of the gas to be detected, contact with the gas to be detected, etc.) are as described above for the semiconductor gas sensor of the present invention.

[0037] [Method for detecting urine and / or stool] As described above, the semiconductor gas sensor of the present invention can be used to detect urine and / or feces, distinguishing between urine and feces. In other words, according to the present invention, the semiconductor gas sensor of the present invention can distinguish between ammonia gas and hydrogen sulfide gas, and distinguish between the presence or absence of urine discharge by ammonia gas and the presence or absence of fecal discharge by hydrogen sulfide gas.

[0038] [How to determine when to change diapers] The present invention provides a method for determining when to change a diaper, which involves using a semiconductor gas sensor of the present invention to detect ammonia gas derived from urine and / or hydrogen sulfide gas derived from feces excreted in the diaper, thereby determining when to change the diaper. The timing of diaper changes can be arbitrarily determined by setting an alarm to sound according to the gas concentration detected by a semiconductor gas sensor. For example, regarding the timing of diaper changes due to urine excretion, one method is to signal the time to change the diaper with an alarm or the like when the response ΔR / R (Response (%)) represented by formula (A) described later, which is caused by contact with ammonia gas, exceeds a predetermined threshold a predetermined number of times. This method makes it possible to change the diaper at a time when the urine capacity of the diaper is not exceeded. Regarding the timing of diaper changes due to fecal excretion, one method is to signal the time to change the diaper with an alarm or the like when the response ΔR / R (Response (%)) represented by formula (A) described later, which is caused by contact with hydrogen sulfide gas, falls below a predetermined threshold, so that the diaper can be changed when fecal excretion occurs once. This method makes it possible to change the diaper at the time of defecation. Furthermore, as shown in Example 3 described later, even when urine and feces are excreted at approximately the same time, an alarm or the like can be used to signal that it is time to change the diaper if the absolute value of the negative change in the response ΔR / R (Response (%)) represented by formula (A) described later is significantly different from the absolute value of the positive change in the response ΔR / R (Response (%)) represented by formula (A) described later that occurred immediately before this negative change, for example, by more than twice as much. This method makes it possible to change diapers in conjunction with bowel movements.

[0039] The following is an example of excellent properties of the VO2(M1) phase as a gas-responsive material. The test results of semiconductor gas sensors using the single-phase VO2(M1) phase and the mixed phase of the VO2(M1) phase and V6O 13 are shown below using as an example. The present invention is not limited to the following examples other than as defined in the present invention. Note that min means minutes.

Example

[0040] Synthesis Example 1: Synthesis of VO2(M1) phase powder (1) Preparation of precursor 5 mL of an H2O2 aqueous solution (30%) and V2O5 (0.05 mol) were added to a container, stirred at 6*0 °C for 24 hours, then N2H4·H2O (2.75 mmol) was further added, and stirred at room temperature (25 °C) for 20 minutes to obtain a gel-like precursor. (2) Synthesis of VO2(M1) phase powder % 5 g of the obtained gel-like precursor was dispersed in 10 mL of water, and a chemical reaction in a subcritical fluid or supercritical fluid (subcritical water or supercritical water) was carried out for 30 to 60 minutes, followed by suction filtration and vacuum drying at 60 °C to obtain a powder of a single-phase VO2(M1) phase or a powder of a mixed phase of the VO2(M1) phase and V6O 13 was obtained. Note that the powder of the single-phase VO2(M1) phase was obtained by carrying out the above (1) precursor preparation step in an atmosphere replaced with nitrogen gas and carrying out the chemical reaction in the supercritical fluid (supercritical water) in the above (2) at 490 °C. The XRD pattern of the obtained powder is shown in Fig. 1. The powder of the mixed phase of the VO2(M1) phase and V6O 13 was obtained by carrying out the above (1) precursor preparation step in the atmosphere and carrying out the chemical reaction in the supercritical fluid (supercritical water) in the above (2) at 410 °C, 460 °C or 490 °C. On the other hand, when the above (1) precursor preparation step was carried out in the atmosphere and the chemical reaction in the subcritical fluid (subcritical water) in the above (2) was carried out at 310 °C or 360 °C, almost no VO2(M1) phase was obtained, and V6O 13 was obtained as the main powder. The XRD pattern of the obtained powder is shown in Fig.!

[0041] (Identification) The obtained powders were identified by analyzing their XRD patterns using an X-ray diffractometer (XRD, Bruker, D2 Phaser). The XRD pattern shown in Figure 1 exhibits characteristic peaks and a good agreement with the XRD pattern of the VO2(M1) phase registered in ICDD (International Centre for Diffraction Data) (ICDD No. 43-1051 VO2(M1), shown in Figure 3(a)), confirming that a VO2(M1) phase powder was obtained. In the XRD pattern of Figure 2, the peaks labeled (011), (-211), (002) / (020), (-212) / (210), (121), (-222), and (022) in order from the 2θ=0° side are attributed to the peaks characteristic of the VO2(M1) phase (peaks indicated by ● in the figure), and the peaks labeled (110), (003), (-401), (310), (-113), (-601), (-711), and (-116) in order from the 2θ=0° side are V6O 13 These are attributed to characteristic peaks (indicated by ▼ in the figure). From these results, it can be concluded that the powder obtained by performing the precursor preparation step (1) in air and the chemical reaction in the supercritical fluid (supercritical water) in (2) at 410°C, 460°C, or 490°C is composed of a VO2(M1) phase and a V6O 13 It was confirmed that it was a powder of the mixed phase. Note that the VO2(M1) phase and V6O 13 The composition (molar ratio) of the mixed phase powder is, under conditions of 410°C, VO2(M1) phase:V6O 13 =0.70:1 (i.e., approximately 41:59), under conditions of 460°C, VO2(M1) phase:V6O 13 =0.99:1 (i.e., approximately 50:50), under the conditions of 490°C, VO2(M1) phase:V6O 13 The ratio = 1.06:1 (i.e., approximately 51:49) was confirmed by analyzing the data using powder X-ray diffraction (XRD) and calculating it from the ratio of the strongest peak areas of each phase.

[0042] Synthesis Example 2: Fabrication of a Gas Detection Device (1) Fabrication of comb-shaped electrode sheets A flexible comb-shaped electrode sheet was fabricated by applying silver paste (product name: BASE-CD01, manufactured by Shanghai Mifang Electronic Technology) to a 33 μm thick HPMC (hydroxypropyl methylcellulose) film at a rate of 1 mm / s and a pressure of 50 kPa using electrode fabrication equipment (product name: Scientific 3, manufactured by Shanghai Zhongbin Technology) (see Figure 4). The comb-shaped portion of the electrode (excluding the lead wires) was 15 mm in length and 5 mm in width, with an electrode spacing of 0.50 mm and an electrode width of 0.50 mm. (2) Fabrication of semiconductor gas sensors In a container containing 200 μL of ethanol, add the VO2(M1) single-phase powder obtained in Synthesis Example 1 above, or the VO2(M1) phase and V6O 13 0.010 g of the mixed phase powder was added and dispersed by ultrasound. 15 μL of the obtained slurry was dropped onto the comb-shaped electrode of the comb-shaped electrode sheet using a pipette. After the slurry had spread over the electrode, the next 15 μL was dropped, and the slurry was dropped a total of four times. The dropped slurry was then dried overnight in a 60°C drying oven to form a sensing layer (i.e., a single-phase VO2(M1) layer, or a VO2(M1) phase and V6O 13 A semiconductor gas sensor chip with a mixed phase layer thickness of approximately 1.8 μm was fabricated (see Figure 5). The obtained semiconductor gas sensor chip was fixed into a chamber for a gas sensing device.

[0043] Example 1: Evaluation of the gas responsiveness of the VO2(M1) phase (1) Semiconductor gas sensor chip using a single-phase VO2(M1) layer The gas response of a semiconductor gas sensor chip using a single-phase VO2(M1) sensing layer fabricated as described above was collected using a two-point probe method with a data acquisition device (Agilent 34970A, Agilent Technologies). Various analyte gases containing NH3, H2, H2S, NO, toluene, ethanol, and acetone at predetermined concentrations were introduced into the sensor device for each gas, and the gas response of the semiconductor gas sensor was measured in a dry nitrogen base at room temperature (20°C). Target gases of various concentrations were mixed with nitrogen gas as a base gas, and the mixture was flowed at a total flow rate of 200 SCCM (standard cubic centimeters per min). The flow rate of 200 SCCM of target gas corresponds to the concentration. The injection time of the analyte was 10 minutes, followed by a 10-minute interval to reintroduce the nitrogen atmosphere. The response ΔR / R (Response (%)) is calculated by comparing the electrical resistance of the sensor in nitrogen (R0) immediately before flowing the target gas of each concentration with the electrical resistance of the sensor in the analyte gas (R0). gas The ratio of ) was calculated using the following formula (A). ΔR / R={(R gas -R0) / R0} × 100% Equation (A) The obtained gas responsiveness results are shown in Figures 6-8. As shown in Figures 6 and 7, after exposing the semiconductor gas sensor to the target gas for 10 minutes, the response values ​​at 20°C showed a positive response with increased electrical resistance for NH3 gas at concentrations of 2.47-24.7 ppm, and a negative response with decreased electrical resistance for H2S gas at 0.50-5.00 ppm, H2 gas at 0.10-0.97 ppm, NO gas at 0.29-2.93 ppm, toluene gas at 9.97-99.7 ppm, ethanol gas at 9.97-99.7 ppm, and acetone gas at 10.1-101 ppm. Furthermore, as shown in Figure 8, at 20°C, 30°C, and 40°C, a positive response was always shown for NH3 gas, while a negative response was always shown for H2S gas, H2 gas, NO gas, toluene gas, ethanol gas, and acetone gas.

[0044] (2) VO2(M1) phase and V6O 13Semiconductor gas sensor chip using a mixed phase layer Instead of the semiconductor gas sensor chip using the single-phase VO2(M1) layer described in (1) above, use the VO2(M1) phase and V6O prepared above. 13 The gas response of a semiconductor gas sensor chip using a mixed phase layer was measured and evaluated in the same manner as in (1) above. Note that the VO2(M1) phase and V6O 13 As the mixed phase layer, in Synthesis Example 1 above, the preparation step of the precursor (1) was carried out under air, and the chemical reaction in the supercritical fluid (supercritical water) in (2) was carried out at 490°C for 30 minutes to obtain the VO2(M1) phase and V6O 13 A layer obtained using a powder of the mixed phase was used. The obtained gas responsiveness results are shown in Figures 9 and 10. As shown in Figures 9(a) to (g), the response values ​​after exposing the semiconductor gas sensor to the target gas for 10 minutes at 20°C showed an increase in electrical resistance and a positive response for NH3 gas with gas concentrations of 2.47 to 24.7 ppm, while for H2S gas (0.50 to 5.00 ppm), H2 gas (0.10 to 0.97 ppm), NO gas (0.29 to 2.93 ppm), toluene gas (9.97 to 99.7 ppm), acetone gas (10.1 to 101 ppm), and ethanol gas (9.97 to 99.7 ppm), the electrical resistance decreased and a negative response was observed. Furthermore, as shown in Figure 10, the response values ​​after exposing the semiconductor gas sensor to the target gas for 10 minutes showed that at 20°C, 30°C, 40°C, 50°C, and 60°C, the electrical resistance increased for NH3 gas at a gas concentration of 24.7 ppm, always showing a positive response (response ΔR / R (Response (%) greater than 0%)), while for all of the following gases—H2S gas at 5.00 ppm, H2 gas at 0.97 ppm, NO gas at 2.93 ppm, toluene gas at 99.7 ppm, acetone gas at 101 ppm, and ethanol gas at 99.7 ppm—the electrical resistance decreased, always showing a negative response (response ΔR / R (Response (%) less than 0%)).

[0045] Example 2: Diaper Sensor (Inside Mode) Evaluation A diaper (Uni-Charm Co., Ltd., product name: Toypanman L size) was fitted to a doll with a waist circumference of 51 cm. The semiconductor gas sensor chip used in Example 1(2) above was fixed to the diaper using double-sided tape at a position 135° on the inside of the diaper, with the navel being 0° (corresponding to one side of the doll's buttocks), so that the sensing layer was not covered by the fixing tape and faced the doll. The responsiveness to artificial urine (composition: water 97.15% by mass, urea 1.75% by mass, NaCl 0.55% by mass, KCl 0.55% by mass) and H2S gas (5 ppm H2S gas simulating volatile gas from feces) were evaluated at 25°C. The response to the artificial urine described above was evaluated by supplying 40 mL of 38°C artificial urine every 30 minutes using a syringe, injecting it into the center of the front of the diaper (towards the doll's navel) inside the diaper. The response to H2S gas (5 ppm H2S gas simulating volatile gases derived from feces) was evaluated by continuously supplying 5 ppm H2S gas for 60 seconds for 60 seconds at the start of measurement (0 minutes), 30 minutes later, and 60 minutes later, using a silicone tube with an inner diameter of 4 mm, into the center of the rear of the diaper (towards the doll's buttocks) inside the diaper. Figure 11 shows the results of the response to artificial urine, and Figure 12 shows the results of the response to H2S gas. As shown in Figure 11, when artificial urine was supplied, the response ΔR / R showed a positive response of approximately 70% for the first (0 min) and second (30 min) supplies, and a positive response of approximately 40% for the third (60 min) supply. Furthermore, as shown in Figure 12, when H2S gas was supplied, the response ΔR / R showed a negative response of approximately -120% for the first (0 min) supply, a negative response of approximately -100% for the second (30 min) supply, and a negative response of approximately -90% for the third (60 min) supply. Note that since the supply of artificial urine and H2S gas was carried out under normal pressure, the response ΔR / R was not necessarily 0% at the timing of artificial urine or H2S gas supply due to the diffusion of various gases, but as described above, a clear negative or positive response was shown. Thus, it can be seen that by using the semiconductor gas sensor of the present invention as a diaper sensor (inside mode), urine and feces can be detected separately.

[0046] Example 3: Diaper Sensor (Outside Mode) Evaluation In Example 2 described above, the semiconductor gas sensor chip used in Example 1(2) was fixed to the outside of the diaper using double-sided tape at a position corresponding to the side of the doll's waist, at 90° when the part corresponding to the navel is set to 0°. The sensing layer was not covered by the fixing tape and was facing the doll side. In Example 2 described above, after fixing the semiconductor gas sensor chip to the outside of the diaper as described above, the responsiveness to the artificial urine and the responsiveness to H2S gas (5 ppm H2S gas simulating volatile gases derived from feces) were evaluated at 25°C in the same manner as in Example 2, except that the evaluation of responsiveness to H2S gas was changed as follows. Furthermore, to evaluate the response to H2S gas, for each of the H2S gas supply sessions (1st (0 min), 2nd (30 min), and 3rd (60 min)), 40 mL of 38°C artificial urine was injected simultaneously with the H2S gas supply using a syringe into the center of the front of the diaper (towards the doll's navel) inside the diaper. The response when H2S gas and artificial urine were supplied simultaneously was evaluated. Figure 13 shows the results for the response to artificial urine, and Figure 14 shows the results for the response to the simultaneous supply of H2S gas and artificial urine. As shown in Figure 13, when artificial urine was supplied, the first (0 min) and second (30 min) supplies showed a positive response with a response ΔR / R of approximately 130%, and the third (60 min) supply showed a positive response (p-type response) with a response ΔR / R of approximately 130% three times within 30 minutes after supply. Furthermore, as shown in Figure 14, in all cases of the first (0 min), second (30 min), and third (60 min) supplies in which H2S gas and artificial urine were supplied simultaneously, a negative response (n-type response) was observed. In addition, similar to Example 2, in Example 3, since the supply of artificial urine and H2S gas was carried out under normal pressure, the response ΔR / R was not necessarily 0% at the timing of artificial urine and / or H2S gas supply due to the diffusion of various gases, but as described above, a clear negative or positive response was observed. Thus, it can be seen that by using the semiconductor gas sensor of the present invention as a diaper sensor (out mode), urine and feces can be detected separately.

Claims

1. An electrode and VO provided on the electrode ２ (M1) Having a phase-containing layer, the VO ２ A semiconductor gas sensor in which the (M1) phase functions as a gas-responsive material.

2. On the substrate, the electrode and the VO ２ The semiconductor gas sensor according to claim 1, having (M1) a phase-containing layer in this order.

3. A semiconductor gas sensor according to claim 1 for distinguishing and detecting ammonia gas from at least one gas selected from hydrogen sulfide, hydrogen, nitric oxide, toluene, acetone, and ethanol.

4. A semiconductor gas sensor according to claim 1, for use at an operating temperature of 15 to 65°C.

5. The semiconductor gas sensor according to claim 1, wherein its electrical resistance increases when exposed to ammonia gas, and decreases when exposed to at least one gas from hydrogen sulfide, hydrogen, nitric oxide, toluene, acetone, and ethanol.

6. The semiconductor gas sensor according to claim 2, wherein the substrate is a flexible substrate.

7. A semiconductor gas sensor according to claim 5, for use in detecting urine and / or feces.

8. A semiconductor gas sensor according to claim 7, for use by being attached to a diaper.

9. A diaper equipped with a semiconductor gas sensor as described in claim 8.

10. A gas detection method that uses the semiconductor gas sensor described in claim 1 to distinguish and detect ammonia gas from at least one gas selected from hydrogen sulfide, hydrogen, nitric oxide, toluene, acetone, and ethanol.

11. A method for detecting urine and / or feces, which distinguishes between urine and feces and detects them using the semiconductor gas sensor described in claim 1.

12. A method for determining when to change a diaper, comprising using the semiconductor gas sensor described in claim 7 to detect ammonia gas derived from urine and / or hydrogen sulfide gas derived from feces excreted in the diaper, thereby determining when to change the diaper.

13. VO ２ A gas-responsive material having the (M1) phase as its active ingredient.

14. A gas-responsive material according to claim 13 for distinguishing and detecting ammonia gas from at least one gas selected from hydrogen sulfide, hydrogen, nitric oxide, toluene, acetone, and ethanol.

15. A gas-responsive material according to claim 14, for use in detecting urine and / or feces.

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