A methane gas sensor and monitoring system based on optical materials

Abstract

A methane gas sensor and monitoring system based on optical materials, wherein the methane gas sensor includes a substrate, a nano dielectric column layer and a gas sensitive layer which are sequentially arranged in a stacked structure from bottom to top. The nano dielectric column layer is composed of a plurality of nano dielectric columns arranged in an array. The upper and lower ends of each nano dielectric column are respectively connected to the gas sensitive layer and the substrate. The gas sensitive layer is made of a material sensitive to methane gas. The nano dielectric column is made of a material with a dielectric constant greater than 10 in the 1530-1565nm infrared band. The substrate is made of a material without absorption loss in the 1530-1565 infrared band. The present invention realizes the monitoring of the CH4 gas concentration by using the gas sensitive mechanism, and the detection data is accurate, stable and reliable. Moreover, the contact between the gas sensitive layer of the methane gas sensor and the CH4 gas causes a change in the refractive index of the gas sensitive layer, so that the reaction in the gas cell can greatly avoid the influence of environmental factors such as temperature and humidity in coal mines on the detection.

Description

Technical Field

[0001] The present invention relates to the field of micro-nano optical technologies, and particularly to a methane gas sensor and a monitoring system based on optical materials. Background Art

[0002] Nano-optical technology is one of the most active frontiers in the current development of the optical discipline, combining the forefront achievements of photonics and nanotechnology. Its main advantage is that it can achieve many new functions based on local electromagnetic interactions.

[0003] In recent years, with the development of micro-nano optical technologies, the application of optical metamaterials in the field of sensing and monitoring has received extensive attention. Optical metamaterials can enhance the local electromagnetic field to form characteristic resonance responses; and these resonance responses are very sensitive to changes in the refractive index of the surrounding medium environment, and gas molecules can cause changes in the refractive index of gas-sensitive materials. Therefore, by monitoring the changes in the resonance responses of optical metamaterials, the concentration of the gas to be detected can be deduced.

[0004] Comparing with the currently known technologies capable of monitoring methane, such as gas chromatographs, electrochemical sensors, gas photoacoustic spectroscopy technologies, spectral absorption fiber optic gas sensors, etc. Due to the complex coal mine environment, the existing monitoring technologies have problems such as low sensitivity, poor accuracy, and short service life, and it is difficult to achieve accurate monitoring of CH4 gas concentration. Therefore, researching a more sensitive and higher detection accuracy CH4 gas concentration monitoring device is an urgent problem to be solved at present. Summary of the Invention

[0005] Based on this, the present invention provides a methane gas sensor and a monitoring system based on optical materials to solve the technical problems that the existing monitoring technologies have problems such as low sensitivity, poor accuracy, and short service life, and it is difficult to achieve accurate monitoring of CH4 gas concentration.

[0006] To achieve the above object, the present invention provides a methane gas sensor based on optical materials, which includes a substrate, a nano dielectric column layer, and a gas-sensitive layer that are sequentially arranged in a stacked structure from bottom to top. The nano dielectric column layer is composed of a plurality of nano dielectric columns arranged in an array. The upper and lower ends of each nano dielectric column are respectively connected to the gas-sensitive layer and the substrate. The gas-sensitive layer is a material sensitive to methane gas. The nano dielectric column is a material with a dielectric constant greater than 10 in the infrared band of 1530 - 1565 nm. The substrate is a material without absorption loss in the infrared band of 1530 - 1565.

[0007] As a further preferred technical solution of the present invention, a plurality of the nano dielectric columns are arranged in a periodic array.

[0008] As a further preferred technical solution of the present invention, the nano-medium columns are in a cuboid structure. A plurality of the nano-medium columns are arranged in an array in the x-y horizontal plane to form a nano-medium column layer. Each nano-medium column has a width of 10-300 nm in the x direction, a length of 100-700 nm in the y direction, and a height of 00-300 nm perpendicular to the x-y horizontal plane. The thickness of the gas-sensitive layer is 100-1000 nm, and the thickness of the substrate is 10-500 μm.

[0009] As a further preferred technical solution of the present invention, the nano-medium columns and the substrate are of an integral structure, and the nano-medium columns are formed on the surface of the substrate by epitaxial growth or ion beam deposition.

[0010] As a further preferred technical solution of the present invention, the refractive index of the gas-sensitive layer for light changes with the concentration of methane gas and satisfies the following formula:

[0011] n eff = 1.4478 - 0.0038c

[0012] where n eff is the refractive index of the gas-sensitive layer, and c is the concentration of methane gas.

[0013] As a further preferred technical solution of the present invention, the material of the substrate is one of quartz, aluminum oxide, and glass; the nano-scale material of the nano-medium columns is one of silicon, titanium dioxide, manganese oxide, and zirconium oxide; the material of the gas-sensitive layer is one of cavitand-A, cavitand-E, titanium dioxide, and tin dioxide.

[0014] According to another aspect of the present invention, the present invention further provides a monitoring system using the methane gas sensor based on an optical material described in any one of the above. The monitoring system includes a gas cell, a broadband light source, a spectrometer, a coupler, and an optical fiber. The broadband light source and the coupler are respectively disposed on two sides outside the gas cell. The gas cell is provided with a light incident hole corresponding to the broadband light source and a light output hole corresponding to the coupler. Converging lenses are disposed between the light incident hole and the broadband light source and between the light output hole and the coupler. Two ends of the optical fiber are respectively connected to the coupler and the spectrometer;

[0015] The light emitted by the broadband light source passes through the corresponding converging lens on one side and then enters the inner cavity of the gas cell through the light inlet hole. After entering the inner cavity of the gas cell, it passes through the light outlet hole and the corresponding converging lens on one side and then enters the coupler. The methane gas sensor is arranged in the inner cavity of the gas cell and is located in the optical path between the light inlet hole and the light outlet hole. When the light transmitted through this optical path passes through the methane gas sensor, the methane gas sensor changes the resonant wavelength of the light according to the concentration of methane gas.

[0016] As a further preferred technical solution of the present invention, plano-convex lenses that seal the inner cavity of the gas cell and are light-transmissive are installed in both the light inlet hole and the light outlet hole. The gas cell is also provided with an air outlet and an air inlet. The methane gas to be measured flows in through the air inlet and flows out through the air outlet.

[0017] As a further preferred technical solution of the present invention, the broadband light source, the spectrometer, the coupler, the plano-convex lens, and the converging lens are respectively arranged on the same axis.

[0018] As a further preferred technical solution of the present invention, the spectrometer is also connected to a data processor.

[0019] The methane gas sensor and monitoring system based on optical materials of the present invention can achieve the following beneficial effects by adopting the above technical solutions:

[0020] 1) The present invention utilizes the gas-sensing mechanism to monitor the concentration of CH4 gas, and the detection data is accurate, stable, and reliable, solving the deficiencies of the existing CH4 gas concentration detection;

[0021] 2) The present invention can be applied to the monitoring of CH4 gas concentration in industries such as coal mines. The gas-sensing layer of the methane gas sensor contacts with CH4 gas, resulting in a change in the refractive index of the gas-sensing layer, so that the reaction in the gas cell can largely avoid the influence of environmental factors such as temperature and humidity in coal mines on the detection;

[0022] 3) The broadband light source adopted by the present invention is a fixed light source and will not be affected by external light sources or other environmental factors. The methane gas sensor detects through the offset of the resonant wavelength and transmission valley of the broadband light source and will not be affected by the layout of external instruments and environmental factors, that is, it has strong applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0024] Figure 1 It is a schematic diagram of the stacked structure of an example provided for the methane gas sensor based on optical materials of the present invention;

[0025] Figure 2 Top view of the nano dielectric column layer of the present invention in the x-y horizontal plane;

[0026] Figure 3 System composition structure diagram of the monitoring system of the present invention;

[0027] Figure 4 Data and curve graph of the monitoring system of the present invention.

[0028] In the figure: 1. Substrate, 2. Nano dielectric column layer, 3. Gas sensitive layer, 4. Nano dielectric column, 100. Methane gas sensor, 101. Broadband light source, 102. Converging lens, 103. Air inlet, 104. Air outlet, 105. Plano-convex lens, 106. Gas cell, 107. Coupler, 108. Optical fiber, 109. Spectrometer, 110. Data processor.

[0029] The realization of the purpose, functional features and advantages of the present invention will be further described in conjunction with the embodiments and with reference to the accompanying drawings. Detailed implementation manners

[0030] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation manners. Terms such as "upper", "lower", "left", "right", "middle" and "one" cited in the preferred embodiments are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments in their relative relationships shall also be regarded as the scope of implementation of the present invention without substantial changes in the technical content.

[0031] As Figure 1 and 2 shown, the present invention provides a methane gas sensor based on optical materials, including a substrate 1, a nano dielectric column layer 2 and a gas sensitive layer 3 which are sequentially arranged in a stacked structure from bottom to top. The nano dielectric column layer 2 is composed of a number of nano dielectric columns 4 arranged in an array. The upper and lower ends of each nano dielectric column 4 are respectively connected to the gas sensitive layer 3 and the substrate 1. The gas sensitive layer 3 is a material sensitive to methane gas. The nano dielectric column 4 is a material with a dielectric constant greater than 10 in the infrared band of 1530 - 1565 nm. The substrate 1 is a material in the infrared band of 1530 - 1565 and has no absorption loss (here it means that the absorption loss can be ignored). The refractive index of the gas sensitive layer 3 for light changes with the concentration of methane gas and satisfies the following formula:

[0032] n eff = 1.4478 - 0.0038c

[0033] where n eff is the refractive index of the gas sensitive layer 3, and c is the concentration of methane gas.

[0034] The working principle of the methane gas sensor of the present invention is as follows:

[0035] Due to the array distribution structure of the nano dielectric column layer 2, which is a periodic structure, it can excite a resonant signal with a high Q value and sensitive to the dielectric constant of the gas-sensitive layer 3 in the near-infrared band. When the concentration of methane gas in the environment around the nano dielectric column 4 changes, it will cause a change in the refractive index of the material of the gas-sensitive layer 3, that is, a change in the dielectric constant of the gas-sensitive layer 3. The resonant wavelength of this resonant signal will change accordingly. By analyzing the resonant signal with the changed resonant wavelength through an external optical measurement device, the monitoring of the methane gas concentration can be realized.

[0036] The nano dielectric column 4 and the substrate 1 are of an integral structure. The nano dielectric column 4 is formed on the surface of the substrate 1 by epitaxial growth or ion beam deposition. Among them, taking the material of the nano dielectric column 4 as silicon and the material of the substrate 1 as quartz as an example, hydrogen (H2) gas carries silicon tetrachloride (SiCl4) or trichlorosilane (SiHCl3), silane (SiH4) or dichlorosilane (SiH2Cl2), etc. into the reaction chamber where the quartz substrate 1 is placed. High-temperature chemical reactions occur in the reaction chamber to reduce or thermally decompose the silicon-containing reaction gas. The generated silicon atoms epitaxially grow on the surface of the substrate 1, thereby generating the nano dielectric column 4. The nano dielectric column 4 and the substrate 1 of an integral structure are obtained by ion beam deposition, which belongs to the gas-phase deposition method. That is, the material used for deposition is ionized by an ion source and is shot onto the surface of the workpiece (substrate 1) under the action of an electric field to deposit a film layer, aiming to change the surface properties of the workpiece. For example, an si film layer is deposited on the surface of quartz (sio2) as the substrate 1 to obtain the nano dielectric column 4, so that the nano dielectric column 4 and the substrate 1 are of an integral structure.

[0037] Preferably, several of the nano dielectric columns 4 are periodically distributed in a 60*60 matrix array. Of course, in specific implementations, other numbers of matrix arrays can also be selected according to different regional restrictions, different nano dielectric column sizes and spacings.

[0038] In a specific implementation, the nano dielectric column 4 has a cuboid structure. Several of the nano dielectric columns 4 are arrayed in the x-y horizontal plane to form the nano dielectric column layer 2. And the width of each nano dielectric column 4 in the x direction is 10 - 300 nm, the length in the y direction is 100 - 700 nm, and the height perpendicular to the x-y horizontal plane is 00 - 300 nm. The thickness of the gas-sensitive layer 3 is 100 - 1000 nm, and the thickness of the substrate 1 is 10 - 500 um.

[0039] Preferably, the material of the substrate 1 is one of quartz, aluminum oxide, and glass; the nanoscale material of the nanoscale dielectric column 4 is one of silicon, titanium dioxide, manganese oxide, and zirconium oxide; the material of the gas-sensitive layer 3 is one of Cryptophane-A, Cryptophane-E, titanium dioxide, and tin dioxide.

[0040] In the present invention, by combining the gas-sensitive characteristics of Cryptophane-A and the resonance characteristics of silicon-based optical metamaterials, precise monitoring of the CH4 gas concentration can be achieved. It can be applied in the coal mine production environment to effectively monitor the CH4 gas concentration, realize the identification and early warning of gas leakage accidents, and has great practical significance for promoting safe production in the coal mine industry.

[0041] As Figure 3 As shown, the present invention also provides a monitoring system using the methane gas sensor of any one of the above embodiments. The monitoring system includes a gas cell 106, a broadband light source 101, a spectrometer 109, a coupler 107, and an optical fiber 108. The broadband light source 101 and the coupler 107 are respectively arranged on both sides outside the gas cell 106. An incident light hole corresponding to the broadband light source 101 and an output light hole corresponding to the coupler 107 are formed on the gas cell 106. Converging lenses 102 are arranged between the incident light hole and the broadband light source 101 and between the output light hole and the coupler 107. Both ends of the optical fiber 108 are respectively connected to the coupler 107 and the spectrometer 109. The spectrometer 109 is also connected to a data processor 110, and the data processor 110 is used to process and analyze the data of the spectrometer 109 to obtain the methane gas concentration value actually monitored by the methane gas sensor 100.

[0042] The broadband light source 101, the spectrometer 109, the coupler 107, the plano-convex lens 105, and the converging lens 102 are arranged on the same axis. The light emitted by the broadband light source 101 passes through the corresponding converging lens 102 on the corresponding side and then enters the inner cavity of the gas cell 106 through the incident light hole. After entering the inner cavity of the gas cell 106, it passes through the output light hole and the corresponding converging lens 102 on the corresponding side and enters the coupler 107. The coupler 107 transmits the incident light to the spectrometer 109 through the optical fiber. The methane gas sensor 100 is arranged in the inner cavity of the gas cell 106 and in the optical path between the incident light hole and the output light hole. When the light transmitted through this optical path passes through the methane gas sensor 100, the methane gas sensor 100 changes the resonance wavelength of the light according to the methane gas concentration.

[0043] In a specific embodiment, plano-convex lenses 105 that are light-transmissive and seal the inner cavity of the gas cell 106 are respectively installed in the light incident aperture and the light exit aperture. The gas cell 106 is also provided with an air outlet 104 and an air inlet 103. The methane gas to be measured flows in through the air inlet 103 and flows out through the air outlet 104.

[0044] In another specific embodiment, a tungsten halogen light source is used as the broadband light source 101. The material of the gas-sensitive layer 3 is selected as Cryptophane-A, the material of the nano dielectric column 4 is selected as silicon, and the material of the substrate 1 is quartz. According to Figure 3 the system diagram shown, the concentration of methane gas flowing in the gas cell 106 is monitored. Refer to Figure 4 as shown. When the gas-sensitive layer 3 contacts CH4, since the relationship between the refractive index (n eff ) of the gas-sensitive layer 3 and the CH4 gas concentration (c) is: n eff = 1.4478 - 0.0038c, as shown in Figure 4 (d) therein. When the refractive index of the gas-sensitive layer 3 changes, it will cause a change in the resonant wavelength of the broadband light source 101, resulting in a transmission valley, as shown in Figure 4 (a) therein, which can be observed on the spectrometer 109. When the CH4 concentration is higher, the transmission valley will shift to the left, as shown in Figure 4 (c) therein. That is, the change in the methane concentration will cause a change in the refractive index of the gas-sensitive layer, thereby changing the spectral position of the resonant signal of the nano dielectric column layer 2 of the optical metamaterial. By monitoring the spectral position of the resonant signal, the methane gas concentration in the gas cell 106 (environment) can be deduced inversely.

[0045] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that these are only examples. Various changes or modifications can be made to these embodiments without departing from the principle and essence of the present invention. The protection scope of the present invention is only limited by the appended claims.

Claims

1. A methane gas sensor based on optical materials, characterized in that, The invention comprises a substrate, a nano-medium column layer and a gas-sensitive layer which are sequentially arranged in a stacked structure from bottom to top, wherein the nano-medium column layer is composed of a plurality of nano-medium columns distributed in an array, and the upper and lower ends of each nano-medium column are respectively connected to the gas-sensitive layer and the substrate, the gas-sensitive layer is made of a material sensitive to methane gas, the nano-medium column is made of a material having a dielectric constant greater than 10 in the infrared band of 1530-1565 nm, and the substrate is made of a material having no absorption loss in the infrared band of 1530-1565 nm; wherein: The refractive index of the gas-sensitive layer to light changes with the concentration of methane gas, satisfying the following formula: ； Among them, is the refractive index of the gas-sensitive layer, is the concentration of methane gas; Working principle of methane gas sensor: The array distribution structure of the nano-dielectric column layer excites a resonant signal with a high Q value and sensitive to the dielectric constant of the gas-sensitive layer in the near-infrared band. When the methane gas concentration in the environment around the nano-dielectric column changes, the refractive index of the gas-sensitive layer material to light will change, causing the dielectric constant of the gas-sensitive layer to change. The resonant wavelength of the resonant signal will change accordingly. The resonant signal with the changed resonant wavelength is analyzed by external optical measuring equipment, thereby realizing the monitoring of methane gas concentration.

2. The methane gas sensor based on an optical material according to claim 1, characterized in that, The plurality of nano-medium columns are distributed in a periodic array.

3. The methane gas sensor based on an optical material according to claim 1, wherein The nano-medium column and the substrate are an integrated structure, and the nano-medium column is formed on the surface of the substrate by epitaxial growth or ion beam deposition.

4. The methane gas sensor based on an optical material according to any one of claims 1-3, characterized in that, The material of the substrate is one of quartz, aluminum oxide, and glass; the nanoscale material of the nano-medium column is one of silicon, titanium dioxide, manganese oxide, and zirconium oxide; the material of the gas-sensitive layer is one of quartz-A, quartz-E, titanium dioxide, and tin dioxide.

5. A monitoring system using the methane gas sensor based on optical materials according to any one of claims 1-4, characterized in that, The monitoring system includes a gas pool, a broad-spectrum light source, a spectrometer, a coupler and an optical fiber. The broad-spectrum light source and the coupler are arranged on two sides of the outside of the gas pool. The gas pool is provided with a light entrance hole corresponding to the broad-spectrum light source and a light exit hole corresponding to the coupler. Converging lenses are arranged between the light entrance hole and the broad-spectrum light source and between the light exit hole and the coupler. The two ends of the optical fiber are connected to the coupler and the spectrometer respectively. The light emitted by the broadband light source passes through the converging lens on the corresponding side and then enters the inner cavity of the gas pool through the light entrance hole. The light entering the inner cavity of the gas pool passes through the light exit hole and the converging lens on the corresponding side and enters the coupler. The methane gas sensor is arranged in the inner cavity of the gas pool and is located in the optical path between the light entrance hole and the light exit hole. When the light transmitted through the optical path passes through the methane gas sensor, the methane gas sensor changes the resonant wavelength of the light according to the methane gas concentration.

6. The monitoring system according to claim 5, characterized in that, The light entrance hole and the light exit hole are both embedded with a plano-convex lens that seals the inner cavity of the gas pool and is light-transmissive. The gas pool is also provided with an air outlet and an air inlet. The methane gas to be measured flows in through the air inlet and flows out through the air outlet.

7. The monitoring system according to claim 6, characterized in that The broadband light source, spectrometer, coupler, plano-convex lens and converging lens are arranged on the same axis.

8. The monitoring system according to claim 7, characterized in that, The spectrometer is also connected to a data processor.

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