A window sheet for enhancing sensitivity of optical absorption type gas detection and a method for manufacturing the same

Abstract

The application discloses a window piece for enhancing the sensitivity of optical absorption type gas detection and a preparation method thereof. The window piece comprises a transmission piece substrate, and a graphene oxide layer is uniformly solidified on the transmission piece substrate. The method comprises the following steps: preparing graphene oxide; preparing a graphene oxide water dispersion solution; preparing a graphene oxide solution; solidifying a graphene oxide layer; according to the absorption peak of the gas to be detected, a corresponding amount of the graphene oxide solution is titrated onto the transmission piece substrate, and drying is performed to completely evaporate the moisture on the transmission piece substrate, so that the solidified graphene oxide layer is obtained. The application changes and improves the sensitivity of gas detection by controlling the graphene oxide layer. The sensitivity of gas detection of the equipment can be improved by replacing the window piece with the solidified graphene oxide layer on the basis of the existing absorption spectrometer. The window piece is simple to prepare and easy to implement.

Description

Technical Field

[0001] This invention belongs to the field of gas detection technology, and relates to optical absorption gas detection accessories and a method for preparing the accessories. Background Technology

[0002] People are increasingly aware of their living environment and health, and are placing higher demands on air quality monitoring. The ability to achieve timely and accurate detection of flammable, explosive, and toxic gases with high sensitivity and reliability is attracting growing attention.

[0003] Absorption-type optical gas sensors, such as CN209231196U, a trace gas absorption cell and absorption spectrometer, are based on the theory of selective absorption of gas molecules and the Lambert-Beer law. They mainly utilize the absorption of light of a specific wavelength by the gas being measured, thereby causing light attenuation. The degree of light intensity attenuation is proportional to the concentration of the gas being measured. The concentration of the gas being measured is obtained by detecting the change in light intensity before and after gas flow.

[0004] In the process of realizing this invention, the inventors discovered that at least one of the following technical problems exists in the prior art:

[0005] 1. In order to improve the sensitivity of gas detection, the light intensity of the light source is usually increased, or the length of the gas chamber is increased, or a reflector is added in the gas chamber to make the light beam reflect multiple times to increase the effective optical path of gas absorption. This increases the amount of light intensity change under the same gas concentration. However, this method has the problems of high system cost, large size, complex optical path structure and poor stability.

[0006] 2. Methods to increase the light intensity of the light source include using lasers or LEDs. Lasers are coherent light sources with a single radiation wavelength, limiting their detection to a single gas. This results in poor selectivity, high cost, and the need for cryogenic cooling systems. LEDs, on the other hand, utilize semiconductor light-emitting devices that are robust, long-lasting, require low driving power, and are cost-effective, making them suitable for absorption-based gas concentration measurements. However, the light power emitted by such sources is typically only a few hundred microwatts.

[0007] 3. To improve the sensitivity of gas detection, the effective working distance of the gas chamber can be increased. This can be achieved by adding a reflector to the gas chamber or by increasing the length of the gas chamber. However, this method is not suitable for beams with large numerical apertures. It has strict requirements on the reflector parameters and installation position in the system, and is expensive or bulky.

[0008] 4. Traditional thermal radiation infrared light sources have problems such as low radiation power, low electro-optical conversion efficiency, and short service life. Summary of the Invention

[0009] Therefore, one of the objectives of this invention is to provide a window for improving the gas detection sensitivity of an absorptive optical gas sensor. This window is simple to manufacture, has low manufacturing cost, and is easy to implement.

[0010] The second objective of this invention is to provide a method for preparing the aforementioned window.

[0011] Through long-term exploration and experimentation, as well as numerous trials and efforts, the inventors have continuously reformed and innovated to solve the above-mentioned technical problems. The technical solution provided by this invention is to provide a window that enhances the sensitivity of optical absorption gas detection, including a transmissive substrate on which a graphene oxide layer is uniformly cured.

[0012] According to one embodiment of the window for enhancing the sensitivity of optical absorption gas detection according to the present invention, the transmissive film substrate is a CaF2 window.

[0013] According to one embodiment of the window for enhancing the sensitivity of optically absorptive gas detection based on the present invention, the cured graphene oxide has a curing amount of 0.25–1.5 μg / cm³. 2 .

[0014] According to one embodiment of the window for enhancing the sensitivity of optically absorptive gas detection of the present invention, the gas is a polar gas, and the curing amount of graphene oxide is 0.4–0.5 μg / cm³. 2 .

[0015] According to one embodiment of the window for enhancing the sensitivity of optical absorption gas detection according to the present invention, the graphene oxide contains one or more functional groups selected from hydroxyl, carboxyl, and epoxy groups.

[0016] The present invention also provides a method for preparing the aforementioned enhanced optical absorption gas detection sensitivity window, comprising the following steps:

[0017] S1. Preparation of graphite oxide;

[0018] S2. Prepare an oxidized graphite ink dispersion;

[0019] S3. Prepare graphene oxide solution;

[0020] S4, Cured graphene oxide layer;

[0021] Based on the absorption peak of the gas to be tested, a corresponding amount of graphene oxide solution is titrated onto the transmission sheet substrate, dried, and the moisture on the transmission sheet substrate is completely evaporated to obtain a solidified graphene oxide layer.

[0022] According to one embodiment of the method for preparing an optically enhanced gas detection sensitivity window according to the present invention, step S1 is as follows:

[0023] S11. Add graphite powder to concentrated sulfuric acid, stir under ice-water bath conditions, then slowly add potassium permanganate and wait for the reaction to proceed in a low-temperature water bath.

[0024] S12. Transfer to a constant temperature water bath and continue stirring;

[0025] S13. Transfer the solution to a large-capacity container. While stirring, add deionized water at a constant rate, keeping the reaction temperature below 70°C until the temperature of the reaction system no longer rises.

[0026] S14. Add hydrogen peroxide until no more bubbles are generated in the system, continue stirring, add hydrochloric acid, and wash the sol thoroughly with deionized water until neutral.

[0027] S15. Centrifuge to remove impurities and obtain graphite oxide.

[0028] According to one embodiment of the method for preparing an optically enhanced gas detection sensitivity window according to the present invention, step S1 is as follows:

[0029] S11. Add a unit weight of graphite powder to concentrated sulfuric acid, stir magnetically for 20 minutes under ice-water bath conditions, then slowly add 1 to 5 times the unit weight of potassium permanganate, and control the water bath temperature at <4℃ for 1.5 hours.

[0030] S12. Transfer to a 37℃ constant temperature water bath and continue magnetic stirring for 2 hours;

[0031] S13. Transfer the solution to a large-capacity container. While stirring, add deionized water at a constant rate, keeping the reaction temperature below 70°C until the temperature of the reaction system no longer rises.

[0032] S14. Add 5% hydrogen peroxide until no more bubbles are generated in the system, and stir magnetically for 0.5 hours; add 5% hydrochloric acid and wash the sol thoroughly with deionized water until neutral.

[0033] S15. Centrifuge to remove impurities and obtain graphite oxide sample.

[0034] According to one embodiment of the method for preparing an optically enhanced gas detection sensitivity window according to the present invention, step S2 and / or S3 is as follows:

[0035] Using ultrapure water as a solvent, the mixture is ultrasonically vibrated until the water and solute are completely mixed.

[0036] According to one embodiment of the method for preparing an optically enhanced absorption-type gas detection sensitivity window of the present invention, the absorption peak of the gas to be measured is determined by the following steps:

[0037] S41. The gas cell of the absorption spectrometer is equipped with windows of different thicknesses of graphene oxide layers, and the first infrared absorption spectrum of the graphene oxide layer is obtained by the spectrometer.

[0038] S42. The gas cell of the absorption spectrometer is equipped with windows of different thicknesses of graphene oxide layers. A specific amount of the gas to be measured is introduced, and the second infrared absorption spectrum of the graphene oxide layer and the gas to be measured is obtained by the spectrometer.

[0039] S43. Obtain the infrared absorption curve of the gas to be tested based on the first infrared absorption spectrum and the second infrared absorption spectrum.

[0040] S44. Obtain the peak height of the characteristic absorption peak of the gas to be tested in the infrared band, obtain the curve of the characteristic absorption peak height changing with the thickness of the graphene oxide layer, and select the graphene oxide layer thickness corresponding to the optimal peak height as the graphene oxide layer thickness for detecting the gas to be tested.

[0041] Compared with the prior art, one of the above technical solutions has the following advantages:

[0042] a) This invention modifies and improves gas detection sensitivity by controlling the graphene oxide layer. The gas detection sensitivity of the device can be improved simply by replacing the window with one that has been cured with graphene oxide on the basis of the existing absorption spectrometer.

[0043] b) The graphene oxide cured on the window serves as the adsorption layer for the gas to be tested. Compared to the graphene layer, the graphene oxide layer has abundant oxygen-containing functional groups, such as hydroxyl, carboxyl, and epoxy groups, which give it attachment sites for polar gas molecules. The type and number of functional groups in the graphene oxide can be controlled by the oxidation conditions.

[0044] c) The inventors discovered that the graphene oxide layer solidified on the transmission plate at the end of the gas cell of the absorption spectrometer, and the change in the thickness of the graphene oxide layer will lead to the change in light intensity under the same gas concentration detection conditions. Therefore, by optimizing the thickness of the graphene oxide layer, the characteristic absorption peaks of the gas to be measured can be effectively utilized to improve the sensitivity of gas detection.

[0045] d) The window of the present invention is simple to prepare and easy to implement. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0047] Figure 1 These are FT-IR spectra of GO with different amounts of oxidant added in the embodiments of the present invention.

[0048] Figure 2These are XPS C1s spectra of different amounts of GO added as oxidant in embodiments of the present invention.

[0049] Figure 3 This is the first infrared absorption spectrum of the graphene oxide layer.

[0050] Figure 4 This is the second infrared absorption spectrum of the graphene oxide layer and methane.

[0051] Figure 5 This is the infrared absorption curve of methane.

[0052] Figure 6 It has an infrared wavenumber of 1305 cm⁻¹ -1 The curve showing the variation of the peak height of the characteristic absorption peak with the thickness of the GO-3 layer.

[0053] Figure 7 It has an infrared wavenumber of 3016 cm⁻¹ -1 The curve showing the variation of the peak height of the characteristic absorption peak with the thickness of the GO-3 layer.

[0054] Figure 8 It has an infrared wavenumber of 1305 cm⁻¹ -1 The curve showing the variation of the peak height of the characteristic absorption peak with the thickness of the GO-5 layer.

[0055] Figure 9 It has an infrared wavenumber of 3016 cm⁻¹ -1 The curve showing the variation of the peak height of the characteristic absorption peak with the thickness of the GO-5 layer. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0057] Example 1

[0058] This embodiment describes a window for enhancing the sensitivity of optical absorption gas detection, comprising a transmission film substrate, wherein the transmission film substrate is a CaF2 window. The CaF2 window is a component disposed at the end of the absorption cell of an absorption spectrometer. The absorption spectrometer includes a gas absorption cell, which comprises a cylindrical cell body with transmission windows disposed at both ends of the cell body. In this embodiment, a graphene oxide layer is uniformly cured on the transmission film substrate. The graphene oxide contains one or more functional groups selected from hydroxyl, carboxyl, and epoxy groups. Compared to graphene coatings, the graphene oxide layer of this invention contains abundant functional groups, which has a significant impact on improving the detection sensitivity of polar gases.

[0059] Experiments show that graphene oxide layers with different oxidation degrees exhibit significant differences in the types and numbers of functional groups, which significantly affect the sensitivity of polar gas detection. Those skilled in the art can determine the optimal oxidation degree of graphene oxide based on the type of gas to be detected using the technical solution disclosed in this invention.

[0060] The experiment also showed that graphene oxide layers of different thicknesses significantly affected the sensitivity of polar gas detection.

[0061] Recommendedly, the curing amount of the graphene oxide is set at 0.25–1.5 μg / cm³. 2 The selection can be made within a certain range. Those skilled in the art can determine the optimal graphene oxide layer thickness based on the type of gas to be tested according to the technical solution disclosed in this invention.

[0062] In one specific embodiment, the gas is methane, or the gas is a mixture including methane, and the curing amount of the graphene oxide is 0.4–0.5 μg / cm³. 2 Recommendedly, the curing amount of the graphene oxide is 0.44 μg / cm³. 2 At this time, the absorption spectrometer was set to an infrared wavenumber of 3016 cm⁻¹. -1 At this time, better sensitivity for methane gas detection can be obtained.

[0063] Example 2

[0064] This embodiment is a preparation example of the graphene oxide described in Example 1. Table

[0065] Add 2g of graphite powder to 70mL of concentrated sulfuric acid and stir magnetically for 20min in an ice-water bath. Then, slowly add 2, 4, 6, 8, and 10g of potassium permanganate respectively, controlling the water bath temperature to <4℃ and reacting for 1.5h. Transfer to a 37℃ constant temperature water bath and continue stirring magnetically for 2h. Transfer the solution to a 1000mL beaker, and while stirring, add a certain amount of deionized water at a uniform rate (using a 100℃ thermometer to guide the flow and observe the temperature within the range), controlling the reaction temperature to below 70℃ until the temperature of the reaction system no longer rises. Then, add an appropriate amount of 5% hydrogen peroxide until no bubbles are generated in the system, stir magnetically for 0.5h, add 5mL of 5% hydrochloric acid, and wash the sol thoroughly with deionized water until neutral. Centrifuge to remove impurities, and obtain graphite oxide samples GO-1, GO-2, GO-3, GO-4, and GO-5.

[0066] Example 2

[0067] This embodiment is a preparation embodiment of the graphene oxide described in Example 1.

[0068] Add 2g of graphite powder to 70mL of concentrated sulfuric acid and stir magnetically for 20min in an ice-water bath. Then, slowly add 2g of potassium permanganate, controlling the water bath temperature to <4℃ and reacting for 1.5h. Transfer to a 37℃ constant temperature water bath and continue stirring magnetically for 2h. Transfer the solution to a 1000mL beaker, and while stirring, add a certain amount of deionized water at a uniform rate (using a 100℃ thermometer to guide the flow and observe the temperature within the range), controlling the reaction temperature to below 70℃ until the temperature of the reaction system no longer rises. Then, add an appropriate amount of 5% hydrogen peroxide until no more bubbles are generated in the system, stir magnetically for 0.5h, add 5mL of 5% hydrochloric acid, and wash the sol thoroughly with deionized water until neutral. Centrifuge to remove impurities and obtain graphite oxide sample GO-1.

[0069] Example 3

[0070] This embodiment is a preparation embodiment of the graphene oxide described in Example 1.

[0071] Add 2g of graphite powder to 70mL of concentrated sulfuric acid and stir magnetically for 20min in an ice-water bath. Then, slowly add 4g of potassium permanganate, controlling the water bath temperature to <4℃ and reacting for 1.5h. Transfer to a 37℃ constant temperature water bath and continue stirring magnetically for 2h. Transfer the solution to a 1000mL beaker, and while stirring, add a certain amount of deionized water at a uniform rate (using a 100℃ thermometer to guide the flow and observe the temperature within the range), controlling the reaction temperature to below 70℃ until the temperature of the reaction system no longer rises. Then, add an appropriate amount of 5% hydrogen peroxide until no more bubbles are generated in the system, stir magnetically for 0.5h, add 5mL of 5% hydrochloric acid, and wash the sol thoroughly with deionized water until neutral. Centrifuge to remove impurities and obtain graphite oxide sample GO-2.

[0072] Example 4

[0073] This embodiment is a preparation embodiment of the graphene oxide described in Example 1.

[0074] Add 2g of graphite powder to 70mL of concentrated sulfuric acid and stir magnetically for 20min in an ice-water bath. Then, slowly add 6g of potassium permanganate, controlling the water bath temperature to <4℃ and reacting for 1.5h. Transfer to a 37℃ constant temperature water bath and continue stirring magnetically for 2h. Transfer the solution to a 1000mL beaker, and while stirring, add a certain amount of deionized water at a uniform rate (using a 100℃ thermometer to guide the flow and observe the temperature within the range), controlling the reaction temperature to below 70℃ until the temperature of the reaction system no longer rises. Then, add an appropriate amount of 5% hydrogen peroxide until no more bubbles are generated in the system, stir magnetically for 0.5h, add 5mL of 5% hydrochloric acid, and wash the sol thoroughly with deionized water until neutral. Centrifuge to remove impurities and obtain graphite oxide sample GO-3.

[0075] Example 5

[0076] This embodiment is a preparation embodiment of the graphene oxide described in Example 1.

[0077] Add 2g of graphite powder to 70mL of concentrated sulfuric acid and stir magnetically for 20min in an ice-water bath. Then, slowly add 8g of potassium permanganate, controlling the water bath temperature to <4℃ and reacting for 1.5h. Transfer to a 37℃ constant temperature water bath and continue stirring magnetically for 2h. Transfer the solution to a 1000mL beaker, and while stirring, add a certain amount of deionized water at a uniform rate (using a 100℃ thermometer to guide the flow and observe the temperature within the range), controlling the reaction temperature to below 70℃ until the temperature of the reaction system no longer rises. Then, add an appropriate amount of 5% hydrogen peroxide until no more bubbles are generated in the system, stir magnetically for 0.5h, add 5mL of 5% hydrochloric acid, and wash the sol thoroughly with deionized water until neutral. Centrifuge to remove impurities and obtain graphite oxide sample GO-4.

[0078] Example 6

[0079] This embodiment is a preparation embodiment of the graphene oxide described in Example 1.

[0080] Add 2g of graphite powder to 70mL of concentrated sulfuric acid and stir magnetically for 20min in an ice-water bath. Then, slowly add 10g of potassium permanganate, controlling the water bath temperature to <4℃ and reacting for 1.5h. Transfer to a 37℃ constant temperature water bath and continue stirring magnetically for 2h. Transfer the solution to a 1000mL beaker, and while stirring, add a certain amount of deionized water at a uniform rate (using a 100℃ thermometer to guide the flow and observe the temperature within the range), controlling the reaction temperature to below 70℃ until the temperature of the reaction system no longer rises. Then, add an appropriate amount of 5% hydrogen peroxide until no more bubbles are generated in the system, stir magnetically for 0.5h, add 5mL of 5% hydrochloric acid, and wash the sol thoroughly with deionized water until neutral. Centrifuge to remove impurities and obtain graphite oxide sample GO-5.

[0081] The functional groups of GO-1, GO-2, GO-3, GO-4, and GO-5 in the graphene oxide samples obtained in Examples 2-6 were characterized using FTIR (Fourier Transform Infrared Spectroscopy). (See attached image.) Figure 1 Characterized by XPS, see Table 1 and Figure 2 .

[0082] from Figure 1 It can be seen that graphite oxide contains a variety of functional groups, and its absorption peak is significantly enhanced with the increase of oxidant dosage. (1048 cm⁻¹) -1 875cm -1 1388cm -1 1731cm -1 1225cm -1 1629cm -1 The absorption peaks at these locations represent the stretching vibration of C-OH, the out-of-plane bending vibration of COC, the bending vibration of the hydroxyl group, the stretching vibration of C=O, the stretching vibration of COC, and the bending vibration of H2O molecules, respectively. Among these characteristic peaks, the C-OH absorption peak is the strongest. COC shows relatively obvious absorption peaks in samples GO-4 and GO-5, indicating that C-OH is converted to COC when the amount of oxidant (potassium permanganate) is excessive.

[0083] The XPS patterns of GO-1, GO-2, GO-3, GO-4 and GO-5 are shown in Figure 2 The results in Table 1 were obtained using XPS peak fitting. Figure 2It can be seen that the content of each functional group in GO varies greatly with different oxidation levels, and the C / O ratio gradually decreases with increasing oxidation level. At low oxidation levels (GO-1, GO-2, GO-3), the relative content of C-OH gradually increases, with the highest content in sample GO-3. When the mass ratio of oxidant to graphite reaches 4 or 5, the relative content of C-OH decreases rapidly, and more COC appears. This is because at excessively high oxidation levels, C-OH combines with oxygen and is further oxidized to form COC. The C=O content is unstable, while COOH appears in samples with higher oxidation levels, GO-4 and GO-5, indicating that the carbonyl and carboxyl functional groups at the edges of the GO structure are easily decomposed or transformed.

[0084] Table 1. Relative content of each functional group in GO-1, GO-2, GO-3, GO-4, and GO-5.

[0085]

[0086] Example 7

[0087] This embodiment is a preparation embodiment of the graphene oxide layer, specifically a preparation embodiment of the method for preparing the enhanced optical absorption gas detection sensitivity window described in Example 1, including the following steps:

[0088] S1. Prepare graphite oxide according to Examples 2 to 6.

[0089] S2. Prepare an oxidized graphite ink dispersion.

[0090] The graphene oxide obtained in step S1 was mixed with ultrapure water to prepare a graphene oxide ink dispersion with a concentration of 1 mg / mL, and then ultrasonically vibrated. The resistivity of the ultrapure water was >18.25 MΩ·cm, the ultrasonic power was 240 W, and the ultrasonication time was 2 h.

[0091] The oxidized graphite ink dispersion prepared using GO-3 is the dispersion recommended in this embodiment.

[0092] S3. Prepare graphene oxide solution.

[0093] The graphene oxide dispersion prepared in step S2 and ultrapure water (resistivity > 18.25 MΩ·cm) were diluted at ratios of 1:300, 1:600, 1:900, 1:1200, and 1:1500 to prepare graphene oxide solutions of different dilutions. The ultrasonic power was 240 W, and the mixture was sonicated for 2 hours to ensure complete mixing of the water and GO.

[0094] The graphene oxide solution obtained by diluting at a ratio of 1:900 is the diluent recommended in this embodiment.

[0095] S4, Cured graphene oxide layer;

[0096] Take 400 μL of graphene oxide solutions with different dilutions prepared in step S3 and titrate them onto different 25 mm * 4 mm transmission sheet substrates. Then, place the transmission sheet with the graphene oxide solution onto a drying oven and dry it at 60 °C for 4 hours to completely evaporate the water, thereby obtaining a solidified graphene oxide layer. Finally, windows with graphene oxide layers of different thicknesses are obtained.

[0097] In this embodiment, the recommended degree of graphene oxide oxidation and the recommended dilution are derived from the curve of the characteristic absorption peak of the gas to be tested (methane in this embodiment) changing with the thickness of the graphene oxide layer.

[0098] The curve showing the change in the characteristic absorption peak of methane gas with the thickness of the graphene oxide layer was prepared using the following steps:

[0099] S41. Windows of different thicknesses of GO-3 graphene oxide layers prepared in step S4 are assembled into the gas cell of the absorption spectrometer, and the first infrared absorption spectrum of the graphene oxide layer is obtained by the spectrometer; such as Figure 3 As shown.

[0100] S42. The gas chamber of the absorption spectrometer is equipped with windows of varying thicknesses of graphene oxide layers. A specific amount of the analyte gas is introduced, and the spectrometer acquires the second infrared absorption spectra of the graphene oxide layer and the analyte gas. Figure 4 As shown.

[0101] S43. Obtain the infrared absorption curve of the gas to be measured based on the first and second infrared absorption lines; such as Figure 5 As shown.

[0102] Figures 3-5 In the diagram, □0 represents a window prepared from undiluted GO-3 graphene oxide, 3□ represents a window prepared from a 1:300 dilution of GO-3 graphene oxide solution, □6 represents a window prepared from a 1:600 ​​dilution of GO-3 graphene oxide solution, 9□ represents a window prepared from a 1:900 dilution of GO-3 graphene oxide solution, 1□2 represents a window prepared from a 1:1200 dilution of GO-3 graphene oxide solution, and 1□5 represents a window prepared from a 1:1500 dilution of GO-3 graphene oxide solution.

[0103] The infrared absorption curve of a gas is the second infrared absorption line minus the first infrared absorption line. It reflects the direct proportionality between the absorption intensity (absorbance) of any emitted light as it passes through a gas cell and the gas concentration, i.e., the Lambert-Beer law. For the infrared absorption spectrum of a single solute in a non-absorbing solvent, the absorbance at any wavenumber (ν) is:

[0104]

[0105] In the formula, A(ν) and T(ν) represent the absorbance and transmittance at wavenumber (ν), respectively; α(ν) represents the absorbance coefficient at wavenumber (ν), which is the absorbance of the sample at wavenumber (ν) at unit concentration and unit thickness; b represents the optical path length (sample thickness); and c represents the concentration of the sample.

[0106] S44. Obtain the peak height of the characteristic absorption peak of the gas to be tested in the infrared band, such as... Figure 5 As shown, the characteristic infrared absorption peaks of methane are located at a wavenumber of 1305 cm⁻¹. -1 and 3016cm -1 At this location, the characteristic absorption peak height was obtained as a function of the graphene oxide layer thickness, and the curves are shown in the figure. Figure 6 and Figure 7 , Figure 6 It has an infrared wavenumber of 1305 cm⁻¹ -1 The curve showing the variation of the peak height of the characteristic absorption peak with the thickness of the GO-3 layer. Figure 7 It has an infrared wavenumber of 3016 cm⁻¹ -1 The curve showing the variation of the peak height of the characteristic absorption peak with the thickness of the GO-3 layer.

[0107] based on Figure 6 and Figure 7 The thickness of the graphene oxide layer corresponding to the optimal peak height was selected as the thickness of the graphene oxide layer for detecting the gas to be tested, that is, 400 μL of GO-3 graphene oxide in a solution with a dilution of 1:900 was cured on a 25 mm * 4 mm transmission sheet substrate.

[0108] In comparison, aside from the different dilutions, the characteristic absorption peak height versus graphene oxide layer thickness curves were generated using the same method described above based on GO-5. The dilutions of GO-5 were set to 1:500, 1:600, 1:1000, 1:1500, 1:2000, 1:2500, and 1:3000, respectively, as shown in the figures. Figure 8 and Figure 9 , Figure 8 It has an infrared wavenumber of 1305 cm⁻¹ -1 The curve showing the variation of the peak height of the characteristic absorption peak with the thickness of the GO-5 layer. Figure 9 It has an infrared wavenumber of 3016 cm⁻¹ -1 The curve showing the variation of the characteristic absorption peak height with the thickness of the GO-5 layer. From... Figure 8 and Figure 9It can be seen that changes in the thickness of GO-5 still affect the sensitivity of gas measurement. However, although the oxidation degree of GO-5 is higher than that of GO-3, the highest peak in the GO-5 change curve is significantly different from that in the GO-3 change curve. When used for methane gas detection, the sensitivity of the window made of GO-5 is not as good as that of the window made of GO-3.

[0109] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A window for enhancing the sensitivity of optical absorption gas detection, characterized in that, The device includes a transmission sheet substrate, which is a CaF2 window; a graphene oxide layer is uniformly cured on the transmission sheet substrate; the graphene oxide is GO-3, and the relative contents of each functional group are C=C / CC 49.94%, C-OH 43.75%, and C=O 6.3%, with a C / O ratio of 2.18; the curing amount of the graphene oxide is 0.4~0.5 μg / cm³. 2 The gas is methane or a mixture of gases including methane.

2. A method for preparing the enhanced optical absorption gas detection sensitivity window as described in claim 1, characterized in that, Includes the following steps: S1. Preparation of graphite oxide: S11. Add a unit weight of graphite powder to concentrated sulfuric acid, stir magnetically for 20 min under ice-water bath conditions, then slowly add 3 times the unit weight of potassium permanganate, and control the water bath temperature at <4℃ for 1.5 h. S12. Transfer to a 37℃ constant temperature water bath and continue magnetic stirring for 2 hours; S13. Transfer the solution to a large-capacity container. While stirring, add deionized water at a constant rate, keeping the reaction temperature below 70°C until the temperature of the reaction system no longer rises. S14. Add 5% hydrogen peroxide until no more bubbles are generated in the system, and stir magnetically for 0.5 h; add 5% hydrochloric acid and wash the sol thoroughly with deionized water until neutral. S15. Centrifuge to remove impurities and obtain graphite oxide sample; S2. Prepare an oxidized graphite ink dispersion; S3. Prepare graphene oxide solution; S4, Cured graphene oxide layer; Based on the absorption peak of the gas to be tested, a corresponding amount of graphene oxide solution is titrated onto the transmission sheet substrate, dried, and the moisture on the transmission sheet substrate is completely evaporated to obtain a solidified graphene oxide layer.

3. The method according to claim 2, characterized in that, Step S2 and / or S3 are as follows: Using ultrapure water as a solvent, the mixture is ultrasonically vibrated until the water and solute are completely mixed.

4. The method according to claim 2, characterized in that, The absorption peak of the gas to be tested is determined through the following steps: S41. The gas cell of the absorption spectrometer is equipped with windows of different thicknesses of graphene oxide layers, and the first infrared absorption spectrum of the graphene oxide layer is obtained by the spectrometer. S42. The gas cell of the absorption spectrometer is equipped with windows of different thicknesses of graphene oxide layers. A specific amount of the gas to be measured is introduced, and the second infrared absorption spectrum of the graphene oxide layer and the gas to be measured is obtained by the spectrometer. S43. Obtain the infrared absorption curve of the gas to be tested based on the first infrared absorption spectrum and the second infrared absorption spectrum. S44. Obtain the peak height of the characteristic absorption peak of the gas to be tested in the infrared band, obtain the curve of the characteristic absorption peak height changing with the thickness of the graphene oxide layer, and select the graphene oxide layer thickness corresponding to the optimal peak height as the graphene oxide layer thickness for detecting the gas to be tested.

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