A non-dispersive multi-gas detection device and method based on surface-enhanced infrared absorption spectrum

Abstract

The application provides a non-dispersive multi-gas infrared gas detection device and method based on surface enhanced infrared absorption spectroscopy, and relates to the field of infrared gas detection. The device comprises an infrared LED light source, a beam combiner, a plano-concave mirror, an off-axis parabolic mirror, a reflective gas chamber based on surface enhanced infrared absorption spectroscopy, a CaF2 focusing lens, an infrared detector, an LED temperature control driver, a preamplifier, a digital lock-in amplifier, a detector temperature control driver and a main controller unit. The reflective gas chamber is a polydimethylsiloxane (PDMS) gas chamber composed of a silicon substrate, a gold layer, an aluminum oxide (Al2O3) layer, a combined metal array antenna and a CaF2 window. The application adopts the combined metal array, adjusts the characteristic absorption position, makes the multi-gas analyte fully utilize the electric field of the enhanced surface area, thereby effectively enhances the absorption of the analyte to the infrared light, and improves the sensing performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of infrared non-dispersive multi-gas detection, and particularly relates to a non-dispersive multi-gas detection device and method based on surface enhanced infrared absorption spectroscopy. BACKGROUND

[0002] Gas detection plays an important role in the fields of industry, agriculture, environment, aerospace, etc. Compared with contact sensors such as electrochemical sensors and semiconductor sensors, optical gas sensors have better selectivity, long service life, are not prone to poisoning, and are highly practical, and are suitable for detecting gases with asymmetric molecular structures. Common optical gas sensing technologies include non-dispersive infrared (NDIR), tunable diode laser absorption spectroscopy (TDLAS), and photoacoustic spectroscopy (PAS) technologies. NDIR gas sensing technology is widely used due to its simplicity and cost-effectiveness. An NDIR gas sensing system mainly consists of an infrared light source, an optical gas cell, and a detector. Currently, a hot topic in NDIR technology research is to improve the detection sensitivity while reducing the size and cost. At the same time, on-chip sensing of multiple greenhouse gases (such as methane and carbon dioxide) is very important in industry, agriculture, and meteorology, but this sensing application is still challenging due to mutual interference between gases.

[0003] Surface enhanced infrared absorption (SEIRA) technology has attracted widespread attention by using metal nanoantennas to amplify near-field intensity in the mid-infrared "molecular fingerprint" range. Localized surface plasmons of metal nanoantennas can produce a large local electromagnetic field enhancement. When the infrared vibration of a gas molecule couples with the localized surface plasmons, the vibration signal of the gas molecule is greatly enhanced, enabling trace detection of gas molecules. Therefore, combining SEIRA technology with NDIR technology can address the current requirements of miniaturization and high performance of NDIR sensors. However, in existing reports, SEIRA technology generally uses infrared microscopes as analytical instruments, which are bulky, expensive, and cannot display gas analysis results in real time, limiting the on-site application of this technology. In addition, there are very few existing studies on multi-gas detection based on surface enhanced infrared absorption, and there is no systematic solution implementation. SUMMARY

[0004] In view of the problem that in the prior SEIRA-NDIR technology, no multi-gas detection implementation solution, high equipment requirements and large analysis instrument, and on-site application, the present application provides a non-dispersive multi-gas detection device and detection method based on surface enhanced infrared absorption spectroscopy, which combines a combined circular antenna array, uses an enhanced electric field to improve the absorption of gas, and can significantly improve the sensitivity of the sensor; at the same time, a reasonable metamaterial structure is adopted to simultaneously enhance the infrared absorption of methane and carbon dioxide gas, a reflective gas chamber structure is combined, a small light source and a detector are selected, the SEIRA-NDIR multi-gas sensor is miniaturized, and the needs of on-site application are met.

[0005] The technical scheme adopted by the present application is:

[0006] In the first aspect, the present application provides a non-dispersive multi-gas detection device based on surface enhanced infrared absorption spectroscopy, which comprises a main controller, an infrared LED temperature control driver, an infrared LED light source, a first flat concave mirror, a beam combiner, an off-axis parabolic mirror, a reflective gas chamber, a second flat concave mirror, a focusing lens, an infrared detector unit, a detector temperature control driver, a dual-channel preamplifier, and a dual-channel digital lock-in amplifier.

[0007] The main controller, the infrared LED temperature control driver, the infrared LED light source, the first flat concave mirror, the beam combiner, the off-axis parabolic mirror, the reflective gas chamber, the second flat concave mirror, the focusing lens, the infrared detector unit, the dual-channel preamplifier, and the dual-channel digital lock-in amplifier are connected in series to form a loop; wherein the main controller is connected to the digital lock-in amplifier.

[0008] In the above technical scheme, further, the reflective gas chamber comprises a silicon substrate, a gold layer, an aluminum oxide layer, a combined metal array antenna, and a PDMS gas chamber shell, the gold layer is arranged on the silicon substrate, the aluminum oxide layer is arranged on the gold layer, the combined metal array antenna is arranged on the aluminum oxide layer, the PDMS gas chamber shell covers the combined metal array antenna and is fixed at the edge of the silicon substrate at the bottom, and the top of the PDMS gas chamber shell is provided with a CaF2 window, and the two sides of the CaF2 window are respectively provided with an air inlet hole and an air outlet hole.

[0009] In the above technical scheme, further, the combined metal array antenna is an array antenna structure formed by a large circular surface and a small circular surface arranged in sequence and spaced apart, the diameter of the large circular surface is 1010nm, the diameter of the small circular surface is 762nm, the period is 3.6μm, and the height of the metal array antenna is 80nm.

[0010] In the above technical scheme, further, the reflective gas chamber is connected with a gas pretreatment unit through the air inlet hole and is connected with a waste gas treatment unit through the air outlet hole.

[0011] In the above technical solution, further, the preparation process of the reflective gas chamber is as follows:

[0012] Step 1: gold layer is prepared on a silicon substrate by using a magnetron sputtering method, and an aluminum oxide layer is prepared on the gold layer by using a thermal evaporation method;

[0013] Step 2: a combined circular photoresist mask structure is prepared on the basis of step 1, and after development, the target pattern is obtained;

[0014] Step 3: a gold antenna array is prepared on the substrate after development by using a magnetron sputtering method;

[0015] Step 4: excess photoresist is removed by using acetone, and finally a combined metal antenna array is formed;

[0016] Step 5: a PDMS gas chamber shell with a CaF2 window is bonded to the silicon substrate, and a reflective gas chamber based on surface-enhanced infrared absorption spectroscopy is obtained.

[0017] In the above technical solution, further, the infrared LED light source includes an infrared methane LED light source and an infrared carbon dioxide LED light source, and the infrared methane LED light source and the infrared carbon dioxide LED light source are controlled to work in a constant temperature and constant current mode by an infrared LED temperature control driver, the driving signal frequency of the infrared methane LED light source is 2 kHz, and the driving signal frequency of the infrared carbon dioxide LED light source is 5 kHz.

[0018] In the above technical solution, further, the infrared detector unit is internally provided with a beam splitter, an infrared methane detector and an infrared carbon dioxide detector, and the light rays converging to the infrared detection unit are split by the beam splitter to the surfaces of the infrared methane detector and the infrared carbon dioxide detector.

[0019] In a second aspect, the present application provides a method for detecting a gas to be measured by a non-dispersive multi-gas detection device based on surface-enhanced infrared absorption spectroscopy, comprising the following steps:

[0020] Step S1: different concentrations of the gas to be measured are sent into a gas pretreatment unit by a gas distribution system, and after treatment, the gas is introduced into a reflective gas chamber until the gas fills the entire gas chamber;

[0021] Step S2: the temperature of the infrared methane LED light source and the infrared carbon dioxide LED light source is controlled to be 25℃ by a main controller driving an infrared LED temperature control driver, and the current is controlled to be 200 mA, the duty cycle is controlled to be 50%, the driving signal frequency of the infrared methane LED light source is controlled to be 2 kHz, and the driving signal frequency of the infrared carbon dioxide LED light source is controlled to be 5 kHz;

[0022] Step S3: the light emitted by the infrared methane LED light source and the infrared carbon dioxide LED light source is combined by the combiner and then enters the reflective gas chamber through the off-axis parabolic mirror;

[0023] Step S4: the first flat-concave mirror, the combiner, the off-axis parabolic mirror, the second flat-concave mirror, the focusing lens and the reflective gas chamber are adjusted so that the signal-to-noise ratio of the output signal of the infrared detector unit is maximum; the light entering the reflective gas chamber is absorbed by the gas, and a small part of the reflected light enters the infrared detector through the second flat-concave mirror and the focusing lens;

[0024] Step S5: the output light signal of the reflective gas chamber is converted into an electric signal by the infrared detector unit, and the absorption signal of the to-be-detected object is obtained through the double-channel preamplifier and the digital lock-in amplifier;

[0025] Step S6: the main controller characterizes the absorption of the to-be-detected gas to light according to the measured absorption signal, analyzes the enhancement effect of the metal antenna on the absorption of the to-be-detected multi-gas, performs fitting, and obtains the relationship between the absorption signal and the gas concentration.

[0026] The beneficial effects of the present application are as follows:

[0027] 1. The present application designs a circular combined metal antenna array, the enhanced electric field near the combined metal antenna array fully interacts with the to-be-detected gas, the absorption signals of methane and carbon dioxide are simultaneously enhanced by optimizing the antenna array radius and period, the detection sensitivity is improved, and NDIR multi-gas sensing is realized.

[0028] 2. The present application grows the combined metal antenna array on a silicon wafer, designs and manufactures a small reflective surface-enhanced PDMS gas chamber, combines a small infrared LED light source and a detector, adopts frequency division multiplexing combined with digital lock-in amplifier technology, improves the detection sensitivity, and realizes the miniaturization of the NDIR multi-gas sensor. DETAILED DESCRIPTION

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0030] Figure 1 The system structure diagram of the present application;

[0031] Figure 2 The gas chamber structure diagram of the present application;

[0032] Figure 3Structure diagram of the combined circular metal antenna photoetching plate of the present application;

[0033] Figure 4 Electric field enhancement effect of the combined circular metal antenna of the present application;

[0034] Figure 5 Absorption spectrum of the metamaterial structure of the present application;

[0035] Figure 6 Preparation process of the metamaterial structure of the present application;

[0036] Figure 7 Flow chart for measuring multiple gas analytes by using the present application.

[0037] Wherein, 1, infrared methane LED light source; 2, infrared carbon dioxide LED light source; 3, infrared LED temperature control driver; 4, first flat concave mirror; 5, beam combiner; 6, off-axis parabolic mirror; 7, reflection type gas cell based on surface enhanced infrared absorption spectroscopy; 8, second flat concave mirror; 9, CaF2 focusing lens; 10, infrared detector unit; 11, detector temperature control driver; 12, dual-channel preamplifier; 13, dual-channel digital lock-in amplifier; 14, main controller; 15, gas pretreatment unit; 16, waste gas treatment unit.

[0038] Wherein, 701, silicon substrate; 702, gold layer; 703, aluminum oxide layer; 704, combined metal array antenna; 705, air inlet hole; 706, PDMS gas cell shell; 707, CaF2 window; 708, air outlet hole. DETAILED DESCRIPTION

[0039] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0040] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0041] Reference Figure 1The application specifically provides a non-dispersive multi-gas detection device based on surface-enhanced infrared absorption spectroscopy, which comprises an infrared methane LED light source 1, an infrared carbon dioxide LED light source 2, a first flat-concave mirror 4, a second flat-concave mirror 8, a beam combiner 5, an off-axis parabolic mirror 6, a CaF2 focusing lens 9, a reflective gas chamber based on surface-enhanced infrared absorption spectroscopy 7, an infrared detector unit 10, an infrared LED temperature control driver 3, a detector temperature control driver 11, a dual-channel preamplifier 12, a dual-channel digital lock-in amplifier 13 and a main controller 14. The main controller 14, the infrared LED temperature control driver 3, the infrared methane LED light source 1, the infrared carbon dioxide LED light source 2, the beam combiner 5, the off-axis parabolic mirror 6, the reflective gas chamber based on surface-enhanced infrared absorption spectroscopy 7, the second flat-concave mirror 8, the CaF2 focusing lens 9, the infrared detector unit 10, the dual-channel preamplifier 12 and the dual-channel digital lock-in amplifier 13 are sequentially connected in a loop; the main controller is connected with the detector temperature control driver 11 and the infrared photoelectric detector unit 10. The infrared carbon dioxide LED light source 2 is connected with the beam combiner 5 through the first flat-concave mirror 4. The reflective gas chamber is connected with a gas pretreatment unit 15 through a gas inlet hole 705 and is connected with a waste gas treatment unit 16 through a gas outlet hole 708.

[0042] The infrared methane LED light source 1 is Lms34LED-TEM-R of LEDMicrosensor NT Company; the infrared carbon dioxide LED light source 2 is Lms43LED-TEM-R of LEDMicrosensor NT Company; the infrared detector unit 10 is Lms36PD-05-TEM-R (methane) and Lms43PD-03-TEM-R (carbon dioxide) of LEDMicrosensor NT Company; the input end of the light source module is connected with the output end of the infrared LED temperature control driver 3 in the electrical part; after the output end of the light source module is combined by the beam combiner 5, the combined light enters the reflective gas chamber based on surface-enhanced infrared absorption spectroscopy 7 through the off-axis parabolic mirror 6; the exiting light enters the CaF2 focusing lens 9 through the second flat-concave mirror 8 and is converged to the infrared detector unit 10. The lock-in amplifier is a dual-channel digital lock-in amplifier 13 based on DSP28335.

[0043] The infrared detector unit 10 is internally provided with a beam splitter, an infrared methane detector and an infrared carbon dioxide detector; the light converged to the infrared detection unit is split by the beam splitter to the surfaces of the infrared methane detector and the infrared carbon dioxide detector.

[0044] The infrared LED light source is internally provided with a thermoelectric cooler and a thermistor, and is controlled to work in a constant temperature and constant current mode by an LED temperature control driver, the driving signal frequency of the infrared methane LED light source 1 is 2 kHz, and the driving signal frequency of the infrared carbon dioxide LED light source 2 is 5 kHz.

[0045] The reflection-type gas chamber 7 based on the surface-enhanced infrared absorption spectrum comprises a silicon substrate 701, a gold layer 702, an aluminum oxide layer 703, a combined metal antenna 704, an air inlet hole 705, a PDMS gas chamber shell 706, a CaF2 window 707 and an air outlet hole 708. Figure 2 The volume of the gas chamber is 10*20*10mm 3 , and the material of the gas chamber is PDMS.

[0046] Referring to Figure 3 , the photomask plate of the combined circular metal antenna structure, the combined metal antenna array 704 is formed by the array antenna structure of the large circular surface and the small circular surface arranged in sequence and spaced.

[0047] Referring to Figure 4 , the electric field enhancement effect of the combined circular metal antenna of the application, the electric field enhancement reaches 3.2*10 3 .

[0048] Referring to Figure 5 , the infrared absorption spectrum of the combined circular metal antenna of the application, it can be seen that the structure has characteristic absorption peaks at 3.3 μm and 4.2 μm.

[0049] Referring to Figure 6 , the process flow chart for preparing the application.

[0050] Step 1: gold layer 702 is prepared on silicon substrate 701 by magnetron sputtering method, and aluminum oxide layer 703 is prepared on gold layer 702 by thermal evaporation method;

[0051] Step 2: prepare a combined circular photoresist mask structure based on step 1, and after development, the target pattern is obtained;

[0052] Step 3: gold antenna array is prepared on the substrate after development by magnetron sputtering method;

[0053] Step 4: remove the excess photoresist by acetone to finally form a combined metal antenna array;

[0054] Step 5: bond the PDMS gas chamber shell 706 with the CaF2 window 707 to the silicon substrate 701 to obtain the reflection-type gas chamber 7 based on the surface-enhanced infrared absorption spectrum.

[0055] Step one, see Figure 6 (a), gold layer 702 was prepared on silicon substrate 701 by magnetron sputtering method, thickness was 40 nm; step two, see Figure 6 (b), Al2O3 layer was prepared on gold layer 702 by thermal evaporation method, thickness was 65 nm; step three, see Figure 6 (c), UV stepper lithography technology was used to perform lithography on the disc antenna array; step four, see Figure 6 (d), after development, gold layer 702 was sputtered by magnetron, thickness was 80 nm; step five, see Figure 6 (e), acetone ultrasonic was used to remove the excess photoresist, and the final metamaterial structure was obtained; see Figure 7 (f) is the top view of the metamaterial structure; the final enhanced structure was adhered to the PDMS gas chamber shell 706, forming a reflection-type gas chamber 7 based on surface-enhanced infrared absorption spectroscopy.

[0056] In this embodiment, the metamaterial structure is divided into four layers, the first layer is silicon substrate 701; the second layer is gold layer 702, thickness is 40 nm; the third layer is Al2O3 layer 703, thickness is 65 nm; the fourth layer is a combined circular gold array, the metal antenna thickness is 80 nm.

[0057] The detection method of the gas to be detected using the above structure is shown in ​ , the main steps include:

[0058] Step S1: different concentrations of the gas to be detected were sent into the gas pretreatment unit 15 by the gas distribution system, and after treatment, they were introduced into the reflection-type gas chamber until the gas filled the entire gas chamber;

[0059] Step S2: the temperature of the infrared methane LED light source 1 and the infrared carbon dioxide LED light source 2 was controlled at 25℃ by the main controller 14 driving the infrared LED temperature control driver 3; and the current was controlled at 200 mA, the duty cycle was controlled at 50%, the driving signal frequency of the infrared methane LED light source 1 was 2 kHz, and the driving signal frequency of the infrared carbon dioxide LED light source 2 was 5 kHz;

[0060] Step S3: the light emitted by the infrared methane LED light source 1 and the infrared carbon dioxide LED light source 2 was combined by the beam combiner, and then entered the reflection-type gas chamber through the off-axis parabolic mirror 6;

[0061] Step S4: the signal-to-noise ratio of the output signal of the infrared detector unit 10 was maximized by adjusting the first flat concave mirror 4, the beam combiner 5, the off-axis parabolic mirror 6, the second flat concave mirror 8, the focusing lens, and the reflection-type gas chamber; the light entering the reflection-type gas chamber was absorbed by the gas, and a small part of the reflected light entered the infrared detector through the second flat concave mirror 8 and the focusing lens;

[0062] Step S5: the output light signal of the reflective gas cell is converted into an electric signal by the infrared detector unit 10, and the absorption signal of the measured object is obtained through a double-channel preamplifier 12 and a digital lock-in amplifier;

[0063] Step S6: the main controller 14 characterizes the absorption of light by the measured gas according to the measured absorption signal, analyzes the enhancement effect of the metal antenna on the absorption of the measured multi-gas, performs fitting, and obtains the relationship between the absorption signal and the gas concentration.

[0064] The above description is only to illustrate the technical solutions of the present application and not to limit the present application. Other modifications or equivalent replacements of the technical solutions of the present application made by those skilled in the art should be covered in the scope of the claims of the present application as long as they do not deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A nondispersive multi-gas detection device based on surface-enhanced infrared absorption spectroscopy, characterized in that, It includes a main controller, an infrared LED temperature control driver, an infrared LED light source, a first plano-concave reflector, a beam combiner, an off-axis parabolic mirror, a reflective air chamber, a second plano-concave reflector, a focusing lens, an infrared detector unit, a detector temperature control driver, a dual-channel preamplifier, and a dual-channel digital lock-in amplifier. The main controller, infrared LED temperature control driver, infrared LED light source, first plano-concave reflector, beam combiner, off-axis parabolic mirror, reflective air chamber, second plano-concave reflector, focusing lens, infrared detector unit, dual-channel preamplifier, and dual-channel digital lock-in amplifier are connected end to end to form a loop; wherein, the main controller is connected to the detector temperature control driver and the infrared photodetector unit. The reflective gas chamber includes a silicon substrate, a gold layer, an aluminum oxide layer, a combined metal array antenna, and a PDMS gas chamber shell. The gold layer is disposed on the silicon substrate, the aluminum oxide is disposed on the gold layer, the combined metal array antenna is disposed on the aluminum oxide layer, the PDMS gas chamber shell covers the combined metal array antenna and its bottom is fixed to the edge of the silicon substrate, and the top of the PDMS gas chamber shell is provided with a CaF2 window, and air inlet and air outlet are respectively provided on both sides. The combined metal array antenna is an array antenna structure formed by arranging a large circular surface and a small circular surface in a circular shape when viewed from above, with the large circular surface having a diameter of 1010 nm and the small circular surface having a diameter of 762 nm, and a period of 3.6 μm.

2. The nondispersive multi-gas detection device based on surface-enhanced infrared absorption spectroscopy according to claim 1, characterized in that, The reflective gas chamber is connected to the gas pretreatment unit through the air inlet and to the exhaust gas treatment unit through the exhaust outlet.

3. The nondispersive multi-gas detection device based on surface-enhanced infrared absorption spectroscopy according to claim 1, characterized in that, The preparation process of the reflective gas chamber is as follows: Step 1: Prepare a gold layer on a silicon substrate using magnetron sputtering, and prepare an aluminum oxide layer on the gold layer using thermal evaporation. Step 2: Based on Step 1, prepare a combined circular photoresist mask structure, and after development, obtain the target pattern; Step 3: Fabricate a gold antenna array on the developed substrate using magnetron sputtering; Step 4: Remove excess photoresist with acetone to finally form the combined metal antenna array; Step 5: Bond the PDMS gas cell shell with the CaF2 window to the silicon substrate to obtain a reflective gas cell based on surface-enhanced infrared absorption spectroscopy.

4. The nondispersive multi-gas detection device based on surface-enhanced infrared absorption spectroscopy according to claim 1, characterized in that, The infrared LED light source includes an infrared methane LED light source and an infrared carbon dioxide LED light source. The infrared methane LED light source and the infrared carbon dioxide LED light source are controlled to operate in a constant temperature and constant current mode by an infrared LED temperature control driver. The driving signal frequency of the infrared methane LED light source is 2 kHz, and the driving signal frequency of the infrared carbon dioxide LED light source is 5 kHz.

5. A nondispersive multi-gas detection device based on surface-enhanced infrared absorption spectroscopy according to claim 4, characterized in that, The infrared detector unit is equipped with a beam splitter, an infrared methane detector, and an infrared carbon dioxide detector. The light rays that converge to the infrared detector unit are split by the beam splitter onto the surfaces of the infrared methane detector and the infrared carbon dioxide detector.

6. A method for detecting a gaseous analyte using a nondispersive multigas detection device based on surface-enhanced infrared absorption spectroscopy according to any one of claims 1-5, characterized in that, Includes the following steps: Step S1: Through the gas mixing system, the gas to be tested at different concentrations is sent into the gas pretreatment unit. After processing, it is introduced into the reflective gas chamber and the gas fills the entire chamber. Step S2: The main controller drives the infrared LED temperature control driver to control the temperature of the infrared methane LED light source and the infrared carbon dioxide LED light source at 25℃; and controls its current to be 200mA, duty cycle to be 50%, and the driving signal frequency of the infrared methane LED light source to be 2 kHz, and the driving signal frequency of the infrared carbon dioxide LED light source to be 5 kHz. Step S3: The light emitted by the infrared methane LED light source and the infrared carbon dioxide LED light source is combined by the beam combiner and then enters the reflective gas chamber through the off-axis parabolic mirror; Step S4: By adjusting the first plano-concave reflector, beam combiner, off-axis parabolic mirror, second plano-concave reflector, focusing lens, and reflective gas cell, the signal-to-noise ratio of the output signal of the infrared detector unit is maximized; the light entering the reflective gas cell is absorbed by the gas, and a small portion of the reflected light passes through the second plano-concave reflector and focusing lens to enter the infrared detector. Step S5: The output optical signal of the reflective gas cell is converted into an electrical signal using an infrared detector unit. After passing through a dual-channel preamplifier and a digital lock-in amplifier, the absorption signal of the analyte is obtained. Step S6: The main controller characterizes the absorption of light by the gas under test based on the measured absorption signal, analyzes the enhancement effect of the metal antenna on the absorption of multiple gases under test, and performs fitting to obtain the relationship between the absorption signal and the gas concentration.

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