Hydrogen sensor

Abstract

This invention provides a hydrogen sensor that can selectively, highly sensitively, and stably detect only hydrogen. [Solution] The device comprises a detection element 14 provided inside a laminated film 141 formed on a transparent substrate 140, in which a hydrogen detection region 143b whose optical properties change upon reaction with hydrogen is formed. By measuring the difference in surface plasmon resonance that occurs in the hydrogen detection region whose optical properties have changed when light is obliquely incident on the detection element, it is possible to detect only hydrogen.

Description

Technical Field

[0001] The present invention relates to a hydrogen sensor for detecting hydrogen gas, and in particular, to a hydrogen sensor using surface plasmon resonance occurring inside a sensing element constituted by a laminated film formed on a transparent substrate.

Background Art

[0002] Chemical sensors for detecting the types and concentrations of chemical substances have been developed, and for example, chemical sensors for detecting hydrogen gas leakage have been developed as hydrogen sensors. A plurality of hydrogen sensors with different detection methods are known, and generally, those that detect hydrogen using an electrical signal such as a change in electrical resistance in the sensing element constituting the hydrogen sensor are common. These electric detection-type hydrogen sensors are required to prevent the risk of explosion caused by overcurrent or spark in an electric circuit coming into contact with hydrogen.

[0003] As an example of an explosion-proof hydrogen sensor with low explosion risk, a method of detecting hydrogen gas by an optical technique is known. For example, the hydrogen sensors disclosed in Japanese National Publication of International Patent Application No. 6-501546 (Patent Document 1) and Japanese Unexamined Patent Application Publication No. 2007-93588 (Patent Document 2) have a sensing element in which a catalytic material such as palladium, whose optical properties change upon contact with a target substance to be detected, is formed on a transparent substrate. A light source, a photodetector, and the sensing element, which are the main components of this hydrogen sensor, are arranged with the atmosphere to be measured interposed therebetween. In the optical detection-type hydrogen sensor, there is no need to arrange a current-carrying part in the measurement atmosphere, and there is also no need to heat the sensing element to a high temperature, so the above problems are avoided, and leakage detection of hydrogen gas can be performed more safely.

[0004] In this hydrogen sensor, hydrogen is detected by measuring a change in optical properties caused by contact with the target substance to be detected on the surface of the sensing element. Therefore, there has been a problem that malfunction occurs when the optical properties of the sensing element change due to adhesion of substances other than hydrogen, chemical reaction, or the like.

[0005] An example of an optical hydrogen sensor capable of selectively detecting only hydrogen is the hydrogen sensor disclosed in Japanese Patent Application Publication No. 2023-113121 (Patent Document 3). This hydrogen sensor has a detection element consisting of a laminated structure comprising a hydrogen detection layer whose optical properties change upon contact with the substance to be detected, a reflective layer that reflects at least a portion of the incident light, and an intermediate layer between the reflective layer and the hydrogen detection layer. By measuring the change in optical properties due to the reaction with hydrogen in the hydrogen detection film formed inside the laminated film, it becomes possible to selectively detect only hydrogen.

[0006] However, this hydrogen sensor requires a translucent layer that reflects or transmits at least a portion of the incident light in order to perform measurements using optical interference. To achieve high detection sensitivity, it is necessary to precisely control the amount of light reflected and transmitted from the translucent layer, and for this purpose, the thickness of the translucent layer must be manufactured with an accuracy of 1 nm or less. Configurations with an even greater number of layers, in addition to the translucent layer, hydrogen detection layer, and intermediate layer, have also been disclosed. Manufacturing detection elements that require high manufacturing precision and complex film structures result in high costs. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Special Publication No. 6-501546 [Patent Document 2] Japanese Patent Publication No. 2007-93588 [Patent Document 3] Japanese Patent Publication No. 2023-113121 [Overview of the project] [Problems that the invention aims to solve]

[0008] Hydrogen sensors using detection elements are required to have high detection accuracy, hydrogen selectivity that allows for the selective detection of only hydrogen gas, and the ability to easily fabricate detection element structures with a high degree of flexibility that can be selected according to the purpose.

[0009] To solve these problems, the objective of the present invention is to easily provide a hydrogen sensor capable of selectively, highly sensitively, and stably detecting only hydrogen. [Means for solving the problem]

[0010] The present invention provides a detection element provided inside a laminated film formed on a transparent substrate, in which a hydrogen detection region whose optical properties change upon reaction with hydrogen is formed. By measuring the difference in surface plasmon resonance that occurs in the hydrogen detection region with altered optical properties when light is obliquely incident on the detection element, it is possible to detect only hydrogen. [Effects of the Invention]

[0011] According to one embodiment of the present invention, a hydrogen sensor capable of selectively, highly sensitively, and stably detecting only hydrogen can be easily provided. [Brief explanation of the drawing]

[0012] [Figure 1] A diagram showing the basic configuration of a hydrogen sensor in the first embodiment of the present invention. [Figure 2A] This characteristic diagram, obtained through optical simulation, shows the relationship between the wavelength of incident light and the reflectance of reflected light when the optical properties change depending on the hydrogen concentration under conditions where surface plasmon resonance occurs. [Figure 2B] This characteristic diagram shows the optical simulation results in Figure 2A, but replaced with the relationship between the change in hydrogen concentration and the rate of change in reflected light. [Figure 3] A characteristic diagram showing the relationship between the film thickness of the hydrogen gas detection layer and the rate of change of reflected light, as determined by optical simulation. [Figure 4] This figure shows an example of a stacked structure of a sensing element for defining the refractive index range of the light guide that irradiates light toward the transparent dielectric layer. [Figure 5] Figure 4 shows a characteristic diagram, obtained through optical simulation, illustrating the relationship between the angle of incidence of incident light and the reflectance of reflected light when the refractive index difference between the transparent dielectric layer and the light guide is changed in the stacked structure. [Figure 6] FIG. 1 is a diagram showing an example of the laminated structure of a sensing element applied to a hydrogen sensor according to a second embodiment of the present invention. [Figure 7A] FIG. 1 is a characteristic diagram showing, through optical simulation, the relationship between the wavelength of incident light and the reflectance of reflected light when optical characteristics change according to hydrogen concentration in a state where surface plasmon resonance occurs. [Figure 7B] FIG. 1 is a characteristic diagram showing the result of the optical simulation of FIG. 7A rearranged to illustrate the relationship between a change in hydrogen concentration and the rate of change in reflected light. [Figure 8] FIG. 1 is a diagram showing a specific configuration of a hydrogen sensor according to a third embodiment of the present invention. [Figure 9] FIG. 1 is a diagram showing an example of the laminated structure of a sensing element used in Simulation Experiment 1. [Figure 10] FIG. 1 is a characteristic diagram showing the rate of change in reflected light with respect to hydrogen exposure as a result of Simulation Experiment 1 of FIG. 9. [Figure 11] FIG. 1 is a diagram showing an example of the laminated structure of a sensing element used in Simulation Experiment 2. [Figure 12] FIG. 1 is a characteristic diagram showing the intensity ratio of polarized signals with respect to hydrogen exposure as a result of Simulation Experiment 2 of FIG. 11. [Figure 13] FIG. 1 is a diagram showing an example of the laminated structure of a sensing element used in Simulation Experiment 3. [Figure 14] FIG. 1 is a characteristic diagram showing the rate of change in reflected light with respect to hydrogen exposure as a result of Simulation Experiment 3 of FIG. 13. DETAILED DESCRIPTION OF THE INVENTION

[0013] First Embodiment FIG. 1 is an overall configuration diagram of a hydrogen gas detection system incorporating a hydrogen sensor 10 according to the first embodiment. The hydrogen gas detection system shown in FIG. 1 is merely an example, and includes the hydrogen sensor 10, an incident optical system, a photodetector 150, and a control device 16.

[0014] As shown in Figure 1, the incident optical system includes a light source 11 and a polarizer 12. It is preferable to use a monochromatic light source (e.g., a semiconductor laser, a gas laser) capable of outputting laser light of a single wavelength as the light source 11. It is preferable to use a polarizer (e.g., a Grant-Thomson prism) that improves the linear polarization characteristics as the polarizer 12.

[0015] The control device 16 is configured to control the light source 11 and the photodetector 150. The laser light output from the light source 11 is converted to linear polarization by passing through the polarizer 12, and is then incident at an oblique angle θ to the hydrogen sensor 10, which will be described later. I The light is incident at an angle (i.e., oblique incidence). Here, the angle of incidence is θ. I This can be defined as the angle formed with the normal H that is perpendicular to the detection element 14 (specifically, the high refractive index transparent substrate 140 as a light guide), which will be described later.

[0016] At this time, the reflected light reflected from the hydrogen sensor 10 is detected by the photodetector 150, and the detected data is output to the control device 16. In the control device 16, for example, the state of change of the reflected light (e.g., reflectance, rate of change of reflected light, rate of change of reflected light amount, reflectance spectrum) is calculated based on the detected data, and the concentration of hydrogen gas is detected based on the calculation result.

[0017] Furthermore, Figure 1 shows the basic configuration of a hydrogen sensor 10 as an example. The hydrogen sensor 10 has a detection element 14 and a high refractive index prism 13 as a light guide. The detection element 14 is constructed by stacking a laminated film 141 on a high refractive index transparent substrate 140 which serves as a light guide.

[0018] The refractive index of the light guide section (high refractive index prism 13, high refractive index transparent substrate 140) is set higher than the refractive index of the low refractive index transparent dielectric layer 142, which will be described later. The refractive index difference Δn between the light guide section 13, 140 and the low refractive index transparent dielectric layer 142 will be described later with reference to Figures 4 and 5.

[0019] As shown in Figure 1, in this basic configuration, both light guides, namely the high refractive index prism 13 and the high refractive index transparent substrate 140, are arranged adjacent to each other. In this case, the high refractive index prism 13 and the high refractive index transparent substrate 140 may be manufactured as an integrated unit beforehand, or they may be manufactured separately and then arranged adjacent to each other without any gaps.

[0020] The above-described laminated film 141 is constructed by laminating a low refractive index transparent dielectric layer 142 and a hydrogen gas detection layer 143. The low refractive index transparent dielectric layer 142 is provided adjacent to the hydrogen gas detection layer 143. The low refractive index transparent dielectric layer 142 is configured to allow laser light to be directed toward the hydrogen gas detection layer 143.

[0021] In the light guide section described above (i.e., the high refractive index prism 13 and the high refractive index transparent substrate 140), the high refractive index transparent substrate 140 is provided adjacent to the low refractive index transparent dielectric layer 142. In this state, the high refractive index prism 13 is positioned opposite the incident optical system described above.

[0022] As a result, the laser light obliquely incident on the detection element 14 passes through the light guide section (i.e., from the high refractive index prism 13 to the high refractive index transparent substrate 140) and is irradiated toward the low refractive index transparent dielectric layer 142. At this time, the laser light irradiated toward the low refractive index transparent dielectric layer 142 passes through the low refractive index transparent dielectric layer 142 and irradiates the hydrogen gas detection layer 143.

[0023] Here, the low refractive index transparent dielectric layer 142 is preferably made of a material with excellent transmittance (i.e., a transparent oxide, transparent nitride, or transparent fluoride), such as silicon dioxide (SiO2), zinc oxide (ZnO), magnesium oxide (MgO), titanium oxide (TiO2), aluminum nitride (AlN), or magnesium fluoride (MgF2).

[0024] The hydrogen gas detection layer 143 is composed of a hydrogen permeable region 143a and a hydrogen detection region 143b. The hydrogen permeable region 143a is configured to allow hydrogen gas (i.e., hydrogen molecules) to permeate after being dissociated into atomic form. The hydrogen detection region 143b is provided adjacent to the hydrogen permeable region 143a. The hydrogen detection region 143b is provided along the lamination interface between the hydrogen gas detection layer 143 and the low refractive index transparent dielectric layer 142.

[0025] Of the hydrogen gas detection layer 143 (hydrogen permeable region 143a), a sensor surface Sf is provided on the side opposite to the aforementioned laminated interface, i.e., the hydrogen detection region 143b. The sensor surface Sf is configured as the only part of the hydrogen sensor 10, including the detection element 14, that comes into contact with the atmospheric environment containing hydrogen gas.

[0026] This enables the realization of a detection element 14 in which a hydrogen detection region 143b, whose optical properties change upon reaction with hydrogen, is provided inside. In this case, the hydrogen detection region 143b is housed inside the detection element 14 and is not exposed to the outside, so as not to be affected by substances other than hydrogen or chemical reactions.

[0027] Here, the hydrogen gas detection layer 143 is preferably made of a material mainly composed of palladium (Pd), which has excellent reactivity with hydrogen gas. Palladium (Pd) has the property that its optical properties, such as refractive index and absorption coefficient, change significantly when it reacts with hydrogen gas (i.e., hydrogen molecules). Palladium (Pd) has hydrogen gas absorption and release properties at room temperature.

[0028] With the hydrogen gas detection layer 143 having these characteristics, hydrogen gas (i.e., hydrogen molecules) that come into contact with the sensor surface Sf dissociates atomically in the hydrogen permeable region 143a, diffuses, and solid-solves, thereby changing the optical properties in the hydrogen detection region 143b.

[0029] In the hydrogen sensor 10 of this embodiment, when laser light output via the above-described incident optical system (light source 11 to polarizer 12) is obliquely incident on the hydrogen sensor 10 (detection element 14), hydrogen gas can be detected by utilizing the surface plasmon resonance (SPR) that occurs at the stacked interface, i.e., the hydrogen detection region 143b.

[0030] The conditions for achieving surface plasmon resonance vary depending on factors such as the wavelength, polarization state, and angle of incidence of the incident light, as well as the optical properties in the hydrogen detection region 143b, which change depending on the hydrogen concentration.

[0031] Figure 2A shows the results of an optical simulation to demonstrate this. In this optical simulation, for example, as shown in Figure 1, a hydrogen sensor 10 was prepared by combining a high refractive index prism 13 made of glass (S-TIH57) with a refractive index of 1.96 and a detection element 14 having a structure described later, and laser light output from the incident optical system (light source 11 to polarizer 12) was obliquely incident on this hydrogen sensor 10.

[0032] The detection element 14 is constructed by laminating a laminated film 141 on a high refractive index transparent substrate 140 made of glass (S-TIH57). The laminated film 141 consists of a hydrogen gas detection layer 143 with a thickness of 200 nm made of palladium (Pd) and a low refractive index transparent dielectric layer 142 with a thickness of 190 nm made of silicon dioxide (SiO2), arranged adjacent to each other.

[0033] As shown in Figures 1 and 2A, the incident angle θ of the laser beam I With the temperature set to 49.4 degrees, the wavelength of the incident light is changed while varying the hydrogen concentration in the hydrogen gas detection layer 143 from 0% to 100%. As a result, the optical properties of the hydrogen detection region 143b change according to the hydrogen concentration. At this time, different surface plasmon resonances occur in accordance with the changes in optical properties.

[0034] For example, if we focus on the surface plasmon resonance that occurs when the incident light wavelength is approximately 630 nm at a hydrogen concentration of 0%, the surface plasmon resonance that occurs when the incident light wavelength is approximately 660 nm at a hydrogen concentration of 20%, and the surface plasmon resonance that occurs when the incident light wavelength is approximately 680 nm at a hydrogen concentration of 40%, the differences in each surface plasmon resonance can be measured as a change in the reflectance of the reflected light from the hydrogen detection region 143b, whose optical properties have changed.

[0035] In this case, the reflected light from the hydrogen detection area 143b is detected by the photodetector 150, and the detection data is output to the control device 16. The control device 16 calculates the reflectance of the reflected light based on the detection data, and calculates the change in the reflectance of the reflected light based on the calculation result.

[0036] In this case, if, for example, the control device 16 has a database in which changes in reflectance and differences in surface plasmon resonance corresponding to hydrogen concentration are correlated, then the differences in surface plasmon resonance can be matched as changes in the reflectance of light reflected from the hydrogen detection region 143b whose optical properties have changed. By doing so, the change in reflectance of the reflected light corresponding to the differences in surface plasmon resonance can be calculated, and the concentration of hydrogen gas can be detected based on the calculation result.

[0037] Figure 2B shows the rate of change of reflected light with respect to change in hydrogen concentration, when the wavelength of incident light that resonates at a hydrogen concentration of 0% (i.e., 630 nm) is fixed. This shows that as the hydrogen concentration increases, the rate of change in reflected light also increases. Therefore, it is demonstrated that by measuring the difference in surface plasmon resonance (i.e., the change in reflected light) according to hydrogen concentration, it is possible to detect only hydrogen.

[0038] Figures 2A and 2B also show the optical simulation results when the low refractive index transparent dielectric layer 142 is absent. In this case, surface plasmon resonance cannot be generated. Therefore, the reflectance and rate of change of the reflected light are maintained at a nearly constant state, and hydrogen concentration cannot be detected. Thus, it is clear that the low refractive index transparent dielectric layer 142 is an indispensable component for the hydrogen sensor 10 (detection element 14).

[0039] Figure 3 shows the results of an optical simulation to determine the acceptable range for the thickness (film thickness) of the hydrogen gas detection layer 143. In this optical simulation, the hydrogen sensor 10 (detection element 14) shown in Figure 1 was placed in an atmospheric environment with a hydrogen gas concentration of 4% (an atmosphere where hydrogen explosions do not occur).

[0040] Then, the rate of change in the amount of reflected light from the hydrogen detection region 143b described above was calculated as the sensor surface Sf was covered with a 5 nm thick carbon film (not shown), while varying the thickness of the hydrogen gas detection layer 143.

[0041] As shown in Figures 1 and 3, it can be seen that the hydrogen gas detection layer 143 is affected by surface contamination in the range where its thickness is less than 50 nm (i.e., the range below 50 nm that does not include 50 nm). Therefore, it is preferable to set the thickness of the hydrogen gas detection layer 143 to a range of at least 50 nm (i.e., the range above 50 nm that includes 50 nm).

[0042] Ideally, the thickness of the hydrogen gas detection layer 143 is set to a range where the rate of change in reflected light is 0%. For example, the thickness of the hydrogen gas detection layer 143 is set to a range greater than 70 nm (i.e., a range above 70 nm that does not include 70 nm). In this case, the thickness of the hydrogen gas detection layer 143 can be set to, for example, 80 nm, 100 nm, 150 nm, 200 nm, etc.

[0043] Furthermore, the thickness of the hydrogen gas detection layer 143 may be set to a range exceeding 200 nm (i.e., a range above 200 nm that does not include 200 nm). In this case, while the increased thickness of the hydrogen gas detection layer 143 makes it less susceptible to surface contamination, it also increases the permeation time of hydrogen gas in the hydrogen gas detection layer 143 (specifically, the hydrogen permeation region 143a). Therefore, it is preferable to set the thickness of the hydrogen gas detection layer 143 according to the application, purpose of use, and operating environment of the hydrogen sensor 10.

[0044] Furthermore, the thickness of the hydrogen gas detection layer 143 may be set to a range below the ideal value described above. For example, the thickness of the hydrogen gas detection layer 143 may be set to a range of less than 70 nm (i.e., a range below 70 nm that does not include 70 nm) and a range of 50 nm or more (i.e., a range above 50 nm that includes 50 nm).

[0045] Figures 4 and 5 show the results of optical simulations for setting the refractive index difference Δn between the low refractive index transparent dielectric layer 142 and the high refractive index transparent substrate 140. In this optical simulation, for example, a detection element 14 was prepared consisting of a laminated film 141 in which a 200 nm thick hydrogen gas detection layer 143 made of palladium (Pd) and a low refractive index transparent dielectric layer 142 made of silicon dioxide (SiO2) were adjacent to each other, and a high refractive index transparent substrate 140 adjacent to the low refractive index transparent dielectric layer 142 (see Figure 4). Laser light output from an incident optical system (light source 11 to polarizer 12) was obliquely incident on this detection element 14 (see Figure 1).

[0046] In this case, as an example shown in Figure 5, the refractive index n of the low refractive index transparent dielectric layer 142 L Set to 1.45, and the refractive index n of the high refractive index transparent substrate 140 H We set it to 1.45 + Δn.

[0047] Then, for each of a set number of predetermined refractive index differences Δn between the low refractive index transparent dielectric layer 142 and the high refractive index transparent substrate 140, the incident angle θ of the laser light is set. IThe change in the reflectance of reflected light when the variable is changed was calculated through simulation.

[0048] According to the calculation results, it was demonstrated that when the refractive index difference Δn between the low refractive index transparent dielectric layer 142 and the high refractive index transparent substrate 140 was set to, for example, Δn = 0.15, 0.2, 0.4, 0.6, 1, 2, 4, and 8, surface plasmon resonance as shown in Figure 2A could be generated. This indicates that the refractive indices of the low refractive index transparent dielectric layer 142 and the high refractive index transparent substrate 140 should be set so that the refractive index difference Δn is in the range of 0.15 to 8 (see Figure 5).

[0049] As described above, according to this embodiment, by housing the hydrogen detection region 143b, whose optical properties change due to reaction with hydrogen, inside the detection element 14 without exposing it to the outside, it is possible to measure the difference in surface plasmon resonance occurring in the hydrogen detection region 143b with altered optical properties without being affected by substances other than hydrogen or chemical reactions, thereby enabling high-precision detection of hydrogen only.

[0050] According to this embodiment, the difference in surface plasmon resonance can be measured as a change in the reflectance of light reflected from the hydrogen detection region 143b, which has altered optical properties. Therefore, hydrogen can be safely and stably detected while avoiding the danger of contact with hydrogen during detection.

[0051] According to this embodiment, by simply constructing a detection element 14 having a two-layer laminated film 141 consisting of a hydrogen gas detection layer 143 and a low refractive index transparent dielectric layer 142, a hydrogen detection region 143b that generates surface plasmon resonance along the laminated interface of the laminated film 141 can be provided. As a result, the element structure of the detection element 14 is simplified, and the hydrogen sensor 10 can be manufactured at low cost.

[0052] "Second Embodiment" Figure 6 is a diagram of the stacked structure of a detection element 14 applied to the hydrogen sensor 10 according to the second embodiment. The detection element 14 shown in Figure 6 is an improved version of a part of the first embodiment described above (i.e., the hydrogen gas detection layer 143). The hydrogen gas detection layer 143 is constructed by stacking a hydrogen reaction layer 146 on a low refractive index transparent dielectric layer 142, and further stacking a hydrogen permeable layer 145 and a catalyst layer 144 on top of the hydrogen reaction layer 146 in this order. Note that the catalyst layer 144 is not necessarily a required component.

[0053] As shown in Figure 6, the hydrogen reaction layer 146 is made of a material mainly composed of palladium (Pd), which has excellent reactivity with hydrogen gas. The hydrogen permeable layer 145 is made of an amorphous material (PdCuSi) that has hydrogen permeability. The catalyst layer 144 is made of a platinum material (Pt) that has catalytic activity. The other components are the same as those of the first embodiment described above, so their description is omitted.

[0054] In the optical simulation of this embodiment, as an example, the thickness of the hydrogen reaction layer 146 was set to 5 nm, the thickness of the hydrogen permeation layer 145 to 200 nm, and the thickness of the catalyst layer 144 to 5 nm, and the laser light was incident at an oblique angle, similar to the first embodiment described above.

[0055] As shown in Figures 6 and 7A, the incident angle θ of the laser beam I With the temperature set to 48.2 degrees, the wavelength of the incident light is changed while varying the hydrogen concentration in the hydrogen gas detection layer 143 from 0% to 100%. As a result, the optical properties of the hydrogen reaction layer 146 change according to the hydrogen concentration. At this time, different surface plasmon resonances occur in accordance with the changes in optical properties.

[0056] For example, if we focus on the surface plasmon resonance that occurs when the incident light wavelength is approximately 650 nm at a hydrogen concentration of 0%, the surface plasmon resonance that occurs when the incident light wavelength is approximately 660 nm at a hydrogen concentration of 20%, and the surface plasmon resonance that occurs when the incident light wavelength is approximately 666 nm at a hydrogen concentration of 40%, the differences in each surface plasmon resonance can be measured as a change in the reflectance of the reflected light from the hydrogen reaction layer 146 (i.e., the laminated interface between the hydrogen gas detection layer 143 and the low refractive index transparent dielectric layer 142) whose optical properties have changed.

[0057] In this case, the reflected light from the laminated interface is detected by the photodetector 150, as in the first embodiment described above, and the detected data is output to the control device 16. Then, the change in reflectance of the reflected light according to the difference in surface plasmon resonance is calculated, and the concentration of hydrogen gas can be detected based on the calculation result.

[0058] Figure 7B shows the rate of change of reflected light with respect to change in hydrogen concentration, when the wavelength of incident light that resonates at a hydrogen concentration of 0% (i.e., 650 nm) is fixed. From this, it can be seen that as the hydrogen concentration increases, the rate of change of reflected light also increases. Therefore, similar to the first embodiment described above, it is demonstrated that only hydrogen can be detected by measuring the difference in surface plasmon resonance (i.e., the change in reflected light) according to the hydrogen concentration.

[0059] As described above, according to this embodiment, by stacking the hydrogen permeable layer 145 and the catalyst layer 144 so as to cover the hydrogen reaction layer 146 to form the hydrogen gas detection layer 143, the thickness of the hydrogen reaction layer 146 can be reduced. This improves the response speed in the hydrogen reaction. Other effects are the same as those of the first embodiment described above, so their explanation will be omitted.

[0060] "Third Embodiment" Figure 8 is an overall configuration diagram of a hydrogen gas detection system incorporating the hydrogen sensor 10 according to the third embodiment. The hydrogen gas detection system shown in Figure 8 is an improvement over the first embodiment described above and comprises a hydrogen sensor 10, an incident optical system, a polarizing beam splitter 18, two photodetectors 151 and 152, and a control device 16.

[0061] As shown in Figure 8, the incident optical system has a light source 11 and a polarizer 12 similar to those in the first embodiment described above. The control device 16 is configured to control the light source 11 and the photodetectors 151 and 152, which are improvements on the first embodiment described above. One of the photodetectors 151 is configured to detect transmitted light of P polarization that has passed through the polarizing beam splitter 18. The other photodetector 152 is configured to detect reflected light of S polarization that has been reflected from the polarizing beam splitter 18.

[0062] Figure 8 shows, as an example, a specific configuration of the hydrogen sensor 10, in which an optical bonding oil 20 is interposed between a high refractive index prism 13 and a high refractive index transparent substrate 140. This maintains the high refractive index prism 13 and the high refractive index transparent substrate 140 in a state of being stacked in close contact with each other without any gaps. The optical bonding oil 20 is preferably made of a material that does not cause total internal reflection of light. In this case, the optical bonding oil 20 can be made of a material having a refractive index similar to that of the high refractive index prism 13 or the high refractive index transparent substrate 140.

[0063] Here, similar to the first embodiment described above, the laser light output through the incident optical system (light source 11 to polarizer 12) was obliquely incident on the hydrogen sensor 10 (detection element 14). At this time, the reflected light from the laminated interface was split into P-polarized transmitted light and S-polarized reflected light via the polarizing beam splitter 18, detected by the photodetectors 151 and 152 described above, and the detection data was output to the control device 16.

[0064] In the control device 16, the ratio of the P / S polarization components of the two reflected lights is calculated based on the detection data. In this case, under the resonance conditions of surface plasmons, the P-polarization component and the S-polarization component of linearly polarized light exhibit different reflectance spectra. At this time, the P-polarization component exhibits a steep (sensitive) reflectance characteristic at the laminated interface, while the S-polarization component exhibits a gentle (slow) reflectance characteristic. Therefore, when the optical identification of the laminated interface changes with increasing hydrogen gas concentration, the P / S polarization of the reflected light takes on a different ratio than that of the incident light. Here, since the ratio of the P / S polarization components of the two reflected lights does not depend on the reflected light intensity, stable measurement is possible even when the intensity of the measured light fluctuates due to fluctuations in the output of the light source, etc. As a result, the hydrogen gas concentration can be stably detected based on the calculation result, similar to the first embodiment described above. Note that the other configurations are the same as in the first embodiment described above, so their explanation is omitted.

[0065] As described above, according to this embodiment, the reflected light from the hydrogen sensor 10 is split into P-polarized transmitted light and S-polarized reflected light via the polarizing beam splitter 18, and measured simultaneously by the two photodetectors 151 and 152, thereby enabling stable detection of hydrogen gas without being affected by fluctuations in the intensity of the measured light. Furthermore, by interposing the optical bonding oil 20 between the high refractive index prism 13 and the high refractive index transparent substrate 140, the high refractive index prism 13 and the high refractive index transparent substrate 140 are maintained in a state of continuous stacking without gaps, thereby improving the light transmittance or directivity. Other effects are the same as those of the first embodiment described above, so their explanation will be omitted.

[0066] "Simulation Experiment 1" Figure 9 is a diagram of the stacked structure of the hydrogen sensor 10 used in the simulation experiment 1. The hydrogen sensor 10 shown in Figure 9 is composed of a light guide section in which an optical bonding oil 20 is interposed between a high refractive index prism 13 and a high refractive index transparent substrate 140, and a laminated film 141 stacked on top of this light guide section. The optical bonding oil 20 can be made of the same material as the optical bonding oil 20 of the third embodiment described above.

[0067] The laminated film 141 is composed of a low refractive index transparent dielectric layer 142 and a hydrogen gas detection layer 143 adjacent to each other. The hydrogen gas detection layer 143 is composed of a hydrogen reaction layer 146 and a hydrogen permeable layer 145 stacked on top of the low refractive index transparent dielectric layer 142 in that order.

[0068] In the first simulation, for example, a hydrogen sensor 10 was prepared by combining a light guide made of glass (S-TIH57) (high refractive index prism 13, high refractive index transparent substrate 140) with a laminated film 141 having a structure described later. Laser light output through the incident optical system (light source 11 to polarizer 12) shown in Figure 1 was obliquely incident on this hydrogen sensor 10. The reflected light was detected by the photodetector 150 shown in Figure 1, and the control device 16 calculated the rate of change of the reflected light based on the detected data.

[0069] As shown in Figure 9, the laminated film 141 is composed of a 120 nm thick low refractive index transparent dielectric layer 142 made of silicon dioxide (SiO2) and a hydrogen gas detection layer 143 having a structure described later, arranged adjacent to each other. The hydrogen gas detection layer 143 is composed of a 30 nm thick hydrogen reaction layer 146 made of a palladium-gold mixed material (PdAu) and a 100 nm thick hydrogen permeable layer 145 made of a hydrogen permeable amorphous material (PdCuSi), arranged adjacent to each other.

[0070] Figure 10 shows the rate of change of reflected light from the lamination interface between the hydrogen gas detection layer 143 and the low refractive index transparent dielectric layer 142 in response to hydrogen exposure. This indicates that the rate of change of reflected light shows a response corresponding to the introduction / deactivation of hydrogen gas.

[0071] As demonstrated in Simulation Experiment 1, since palladium (Pd) is prone to degradation due to hydrogen embrittlement, the hydrogen reaction layer 146 was constructed using a material that mixes palladium (Pd) with gold (Au), and this hydrogen reaction layer 146 was covered with a hydrogen permeable layer 145. This demonstrated that it is possible to stably detect only hydrogen without being affected by surface contamination.

[0072] "Simulated Experiment 2" Figure 11 shows the stacked structure of the hydrogen sensor 10 used in Simulation Experiment 2. The hydrogen sensor 10 shown in Figure 11 is an improved version of a part of the hydrogen sensor 10 from Simulation Experiment 1 described above (i.e., the hydrogen reaction layer 146). The hydrogen reaction layer 146 is composed of a material in which silver (Ag) is mixed with palladium (Pd). In this case, the thickness of the hydrogen reaction layer 146 is 5 nm, and the thickness of the low refractive index transparent dielectric layer 142 is 140 nm. The other components are the same as those in Simulation Experiment 1 described above, so their explanation is omitted.

[0073] In Simulation Experiment 2, laser light output through the incident optical system (light source 11 to polarizer 12) shown in Figure 8 was obliquely incident on the hydrogen sensor 10. The reflected light was detected by the two photodetectors 151 and 152 shown in Figure 8, and the control device 16 calculated the ratio of the P / S polarization components of the two reflected lights based on the detected data.

[0074] Figure 12 shows the intensity ratio of the polarization signal in response to hydrogen exposure. This simulation experiment 2 demonstrates that by using the ratio of P / S polarization components, which is unaffected by fluctuations in reflected light intensity, as the measurement signal, it is possible to achieve greater stability and accuracy of the measurement signal (i.e., improved signal-to-noise ratio) compared to Figure 10 shown in the simulation experiment 1.

[0075] "Simulation Experiment 3" Figure 13 is a diagram of the stacked structure of the hydrogen sensor 10 used in Simulation Experiment 3. The hydrogen sensor 10 shown in Figure 13 is an improved version of a part of the hydrogen sensor 10 from Simulation Experiment 1 described above (i.e., the hydrogen reaction layer 146 and the low refractive index transparent dielectric layer 142). The hydrogen reaction layer 146 is made of a material (2 nm thick) which is a mixture of palladium (Pd) and silver (Ag). The low refractive index transparent dielectric layer 142 is made of a material which is a combination of zinc oxide (ZnO) with a thickness of 10 nm and silicon dioxide (SiO2) with a thickness of 104 nm. The other components are the same as those in Simulation Experiment 1 described above, so their explanation is omitted.

[0076] In simulation experiment 3, laser light output through the incident optical system (light source 11 to polarizer 12) shown in Figure 1 was obliquely incident on the hydrogen sensor 10 described above. The reflected light was detected by the photodetector 150 shown in Figure 1, and the control device 16 calculated the rate of change of the reflected light based on the detected data.

[0077] Here, the refractive index of zinc oxide (ZnO) used in simulation experiment 3 is 1.99, which is not low compared to S-TIH57 (refractive index of 1.96) used in the high refractive index prism 13 and the high refractive index transparent substrate 140. However, by combining it with silicon dioxide (SiO2), which has a refractive index of 1.45, if the refractive index of the low refractive index transparent dielectric layer 142 as a whole falls within the range explained in Figures 4 and 5, hydrogen gas can be detected using surface plasmon resonance.

[0078] Figure 14 shows the rate of change of reflected light from the lamination interface between the hydrogen gas detection layer 143 and the low refractive index transparent dielectric layer 142 in response to hydrogen exposure. This indicates that the rate of change of reflected light remains stable in accordance with the hydrogen concentration.

[0079] In summary, as demonstrated in Simulation Experiment 3, the overall thickness of the low refractive index transparent dielectric layer 142 can be reduced by constructing the low refractive index transparent dielectric layer 142 using a material that combines zinc oxide (ZnO) and silicon dioxide (SiO2). [Explanation of Symbols]

[0080] 10...Hydrogen sensor, 11...Light source, 12...Polarizer, 13...High refractive index prism, 14...Detection element, 16...Control device, 18...Polarizing beam splitter, 20...Optical coupling oil, 140...High refractive index transparent substrate, 141...Laminated film, 142...Low refractive index transparent dielectric layer, 143...Hydrogen gas detection layer, 143a...Hydrogen permeation region, 143b...Hydrogen detection region, 144...Catalyst layer, 145...Hydrogen permeation layer, 146...Hydrogen reaction layer, 150, 151, 152...Photodetector, Sf...Sensor surface.

Claims

1. The device comprises a detection element provided inside a laminated film formed on a transparent substrate, in which a hydrogen detection region whose optical properties change upon reaction with hydrogen is located. A hydrogen sensor capable of detecting only hydrogen by measuring the difference in surface plasmon resonance that occurs in the hydrogen detection region where the optical properties have changed when light is obliquely incident on the detection element.

2. The hydrogen sensor according to claim 1, wherein the difference in surface plasmon resonance can be measured as a change in the reflectance of light reflected from the hydrogen detection region whose optical properties have been altered.

3. The hydrogen sensor according to claim 1, wherein the hydrogen detection region is not exposed to the outside and is housed inside the laminated film of the detection element, so as not to be affected by substances other than hydrogen or chemical reactions.

4. The aforementioned detection element is A hydrogen gas detection layer comprising the hydrogen detection region and a hydrogen permeable region provided adjacent to the hydrogen detection region and capable of permeating hydrogen gas, The laminated film is configured by stacking a transparent dielectric layer, which is provided adjacent to the hydrogen gas detection layer and causes light obliquely incident on the detection element to irradiate the hydrogen gas detection layer, The hydrogen sensor according to claim 1, wherein the hydrogen detection region is provided along the laminated interface between the hydrogen gas detection layer and the transparent dielectric layer in the laminated film.

5. The hydrogen sensor according to claim 4, wherein the hydrogen gas detection layer constituting the laminated film is made of a material mainly composed of palladium (Pd).

6. The hydrogen sensor according to claim 4, wherein the transparent dielectric layer is made of a material with excellent transmittance, which includes at least one of a transparent oxide, a transparent nitride, or a transparent fluoride.

7. The hydrogen sensor according to claim 4, wherein the hydrogen gas detection layer changes the optical properties in the hydrogen detection region by causing hydrogen molecules in contact with the sensor surface to dissociate atomically, diffuse, and solid-solve in the hydrogen permeable region.

8. The detection element is constructed by stacking the laminated film on the light guide portion. The light guide portion is provided adjacent to the transparent dielectric layer and irradiates the light obliquely incident on the sensing element toward the transparent dielectric layer, The hydrogen sensor according to claim 4, wherein the refractive index of the light guide portion is set to be higher than the refractive index of the transparent dielectric layer.

Images