Molybdenum disulfide-based gas sensor with high moisture resistance as well as preparation method and application of molybdenum disulfide-based gas sensor
By preparing MoS2 nanosheets through mechanical exfoliation and combining them with a hydrophobic encapsulation layer of a metal-organic framework, the signal instability problem of existing gas sensors under humidity fluctuations is solved, achieving high selectivity and high sensitivity for nitrogen dioxide detection, which is suitable for environmental monitoring and other fields.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-25
- Publication Date
- 2026-03-27
AI Technical Summary
Existing gas sensors exhibit good sensing performance at high temperatures, but they have poor selectivity and low response, and are sensitive to changes in relative humidity, resulting in unstable signals. In particular, the performance of two-dimensional materials is affected by humidity fluctuations.
MoS2 nanosheets were prepared by mechanical exfoliation and then transferred to the surface of the substrate electrode by dry method. They were then combined with a hydrophobic encapsulation layer UiO-66-NH2 of a metal-organic framework to form a non-covalent bond, which enhanced the hydrophobic effect and improved the selectivity and stability of nitrogen dioxide.
It achieves stable, reversible, and highly sensitive gas detection over a wide range of relative humidity, with particularly high selectivity for nitrogen dioxide. This reduces the contaminant level of the sensing material, improves the detection limit and response value, and enhances its moisture resistance.
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Figure CN121740962A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of gas detection, and particularly relates to a high-humidity-resistant molybdenum disulfide-based gas sensor and a preparation method and application thereof. BACKGROUND
[0002] Gas sensors have been widely used in aerospace, environmental monitoring, medical diagnosis and public safety, etc. Especially, with the continuous advancement of industrialization and modernization, the role of gas sensors in environmental monitoring is becoming increasingly evident. Existing gas sensors mostly use metal oxides such as zinc oxide, tin dioxide and titanium dioxide as the core sensing material, but such sensing materials can only exhibit good sensing performance at high temperatures greater than 200℃, and have poor selectivity to target gases and low response. These shortcomings have become important factors limiting the further widespread use of metal oxide materials in gas sensors.
[0003] In recent years, two-dimensional materials such as graphene and transition metal sulfides have the advantages of adjustable layer number, large specific surface area, high carrier mobility, etc., and are expected to replace traditional metal oxides to become the main sensing material in future gas sensors. Compared with graphene, transition metal sulfides can control their energy band structure by adjusting the layer number, and thus control their electrical and optoelectronic properties, so they have more practical application value. The larger specific surface area of two-dimensional materials brings them better gas sensing performance, while various environmental variables also correspondingly more easily negatively affect the gas sensing performance, among which relative humidity has the greatest impact on the performance of two-dimensional materials. With the frequent occurrence of extreme weather in recent years, the rapid fluctuation of relative humidity in a short time has gradually become a common natural phenomenon, which will significantly cause the instability of the signal of the gas sensor. In addition, water molecules in the environment are more likely to be adsorbed on the surface of the material, occupying the active sites of the target gas and blocking the carrier path, which will seriously affect the performance of the gas sensor.
[0004] Therefore, it is necessary to provide a gas sensor capable of realizing stable, reversible and high-sensitivity response under the condition of wide variation of relative humidity working range. SUMMARY
[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a high-humidity-resistant molybdenum disulfide (MoS2) based gas sensor and a preparation method and application thereof, which can realize stable, reversible and high-sensitivity response under the condition of wide variation of relative humidity range, and has high selectivity to nitrogen dioxide.
[0006] To solve the above technical problems, the first aspect of the present application provides a gas sensor, which comprises, from bottom to top, a substrate electrode, a MoS2 nanosheet and a metal-organic framework hydrophobic encapsulation layer, wherein the MoS2 nanosheet is prepared by a mechanical exfoliation method and is transferred to the surface of the substrate electrode by a dry method.
[0007] Specifically, the MoS2 nanosheet of the present application is prepared by a physical and mechanical exfoliation method and is transferred to the surface of the substrate electrode by a dry method. Compared with traditional chemical methods such as a hydrothermal method and a chemical vapor deposition method, the MoS2 nanosheet obtained by the mechanical exfoliation method can effectively avoid the use of organic solvents and other auxiliary reagents, greatly reduce the pollutants on the surface of the sensing material, and thus maximize the intrinsic gas sensing performance of the sensing material. Meanwhile, the MoS2 nanosheet is encapsulated by a metal-organic framework hydrophobic material, which can realize stable, reversible and high-sensitivity detection of extremely low-concentration gases (such as nitrogen dioxide) within a wide relative humidity range.
[0008] In some embodiments of the present application, the thickness of the MoS2 nanosheet is 10-100 nm; preferably, the thickness of the MoS2 nanosheet is 20-100 nm; further preferably, the thickness of the MoS2 nanosheet is 20-50 nm.
[0009] In some embodiments of the present application, the metal-organic framework hydrophobic encapsulation layer is UiO-66-NH2, and the UiO-66-NH2 is grown in situ on the surface of the MoS2 nanosheet.
[0010] Specifically, the metal-organic framework hydrophobic encapsulation layer of the present application is combined with the MoS2 nanosheet by an in-situ growth method, and there is a non-covalent bond (van der Waals force) interaction between the two, which is much stronger than the traditional coating or direct contact method, thereby having a more optimal hydrophobic encapsulation effect. Meanwhile, the hydrophobic encapsulation material of the present application uses UiO-66-NH2, and the amino group (-NH2) in the UiO-66-NH2 has a strong attraction to the acidic gas nitrogen dioxide. Therefore, the gas sensor of the present application has high selectivity for the detection of nitrogen dioxide. In addition, the UiO-66-NH2 hydrophobic encapsulation layer of the present application is an insulating material, and electrons cannot be conducted, so it does not directly participate in gas sensing.
[0011] In some embodiments of the present application, the thickness of the metal-organic framework hydrophobic encapsulation layer is 1-10 nm; preferably, the thickness of the metal-organic framework hydrophobic encapsulation layer is 2-10 nm; further preferably, the thickness of the metal-organic framework hydrophobic encapsulation layer is 2-5 nm.
[0012] In some embodiments of the present application, the substrate electrode comprises a substrate, a first electrode and a second electrode, the first electrode and the second electrode are fixed on the surface of the substrate, and the first electrode and the second electrode are connected in series through the MoS2 nanosheet.
[0013] In some embodiments of the present application, the substrate can adopt the materials commonly used in the art, such as silicon dioxide.
[0014] In some embodiments of the present application, the first electrode and the second electrode can adopt the electrodes commonly used in the art, such as chromium / gold electrodes. And the first electrode and the second electrode are separated from each other.
[0015] The second aspect of the present application provides a preparation method of the above-mentioned gas sensor, comprising the following steps: (1) MoS2 nanosheets are adhered from MoS2 bulk crystals by mechanical exfoliation, and then the MoS2 nanosheets are transferred to a polymer film; (2) After the polymer film is attached to the substrate electrode, it is separated, so that the MoS2 nanosheets are transferred to the surface of the substrate electrode, and a substrate electrode containing MoS2 nanosheets is prepared; (3) The substrate electrode containing MoS2 nanosheets is inverted and floated on the surface of a metal organic framework ligand solution to react, and a metal organic framework hydrophobic encapsulation layer is generated in situ on the surface of the MoS2 nanosheet, thereby preparing the gas sensor.
[0016] In some embodiments of the present application, the metal organic framework ligand solution contains 2-amino terephthalic acid and zirconium 6 clusters, the concentration of the metal organic framework ligand solution is 1.0-5.0 mmol / L, and the volume ratio of the 2-amino terephthalic acid and zirconium 6 cluster solution is 1:1-1:3, and they are reacted to synthesize UiO-66-NH2.
[0017] In some embodiments of the present application, the process of adhering MoS2 nanosheets comprises the following steps: a first adhesive tape is used to adhere initial MoS2 nanosheets from MoS2 bulk crystals, then a second adhesive tape is compounded with the first adhesive tape, and then separated, so that part of the MoS2 nanosheets are adhered on the first adhesive tape and the second adhesive tape, and then a new adhesive tape is introduced to repeat the above-mentioned compounding and separating process until smooth MoS2 nanosheets appear on the adhesive tape, and the thickness of the MoS2 nanosheets is 10-100 nm.
[0018] In some embodiments of the present application, the first adhesive tape, the second adhesive tape, and the introduced new adhesive tape are all Scotch adhesive tapes.
[0019] In some embodiments of the present application, the polymer film is a polydimethylsiloxane film.
[0020] In some embodiments of the present application, after the metal-organic framework hydrophobic encapsulation layer is generated in situ in step (3), the method further comprises the steps of washing the metal-organic framework hydrophobic encapsulation layer with deionized water and vacuum drying the metal-organic framework hydrophobic encapsulation layer. In some embodiments of the present application, the temperature of the vacuum drying is 60-80℃, and the time of the vacuum drying is 50-70 min.
[0021] In some embodiments of the present application, in step (3), the reaction time is 50-70 min.
[0022] The third aspect of the present application provides the use of the above-mentioned gas sensor in detecting the concentration of nitrogen dioxide.
[0023] In some embodiments of the present application, the process of detecting the concentration of nitrogen dioxide by the gas sensor is as follows: first, applying voltage and light to the gas sensor, and contacting the gas sensor with the gas to be detected, and then detecting the change in the electrical signal of the gas sensor before and after the gas sensor contacts the gas to be detected, to obtain the concentration of nitrogen dioxide in the gas to be detected.
[0024] In some embodiments of the present application, the concentration of nitrogen dioxide obtained by the change in the electrical signal can be obtained at least by the following method or other methods well known in the art: detecting standard gas samples with different concentrations to obtain a standard curve of the change amount and the concentration or a corresponding correlation equation, and substituting the detection result of the gas to be detected into the standard curve or the correlation equation to obtain the concentration of the gas to be detected.
[0025] In some embodiments of the present application, the gas sensor is detected under the condition that the power density of the light is 50-150 μW / cm 2 The wavelength of the light is 400-450 nm; preferably, the wavelength of the light is 400-440 nm; further preferably, the wavelength of the light is 400-420 nm; more preferably, the wavelength of the light is 400-410 nm.
[0026] In some embodiments of the present application, the electrical signal is resistance.
[0027] In some embodiments of the present application, the detection environment temperature is room temperature, and the relative humidity is below 75%. Preferably, the relative humidity is 20-75%; further preferably, the relative humidity is 35-75%.
[0028] The above technical solutions of the present application have at least the following technical effects or advantages compared with the prior art: (1) The MoS2 nanosheet of the present application is prepared by a mechanical exfoliation method and is transferred to the surface of the base electrode by a dry method, thereby minimizing the use of auxiliary reagents, greatly reducing the level of pollutants on the surface of the MoS2 nanosheet, and thus retaining the intrinsic gas sensing performance of the sensing material to the greatest extent, enabling stable, reversible and high-sensitivity detection of extremely low-concentration gases (such as nitrogen dioxide) within a wide relative humidity range, achieving a wide relative humidity working range of less than 75% relative humidity, and the relative standard deviation at each relative humidity is less than 6%, and the minimum detection limit is less than 20 ppb.
[0029] (2) The MoS2 nanosheet is encapsulated by a metal organic framework hydrophobic material (such as UiO-66-NH2) in the present application, The encapsulation layer is closely combined with the MoS2 nanosheet and has a strong attraction to the acidic gas nitrogen dioxide. Therefore, the gas sensor of the present application has high selectivity for the detection of nitrogen dioxide. BRIEF DESCRIPTION OF DRAWINGS
[0030] Figure 1 is a structural schematic diagram of the gas sensor of the present application. Among them: 110-base, 121-first electrode, 122-second electrode, 130-MoS2 nanosheet, 140-metal organic framework hydrophobic encapsulation layer.
[0031] Figure 2 is an optical image of the single MoS2 gas sensor prepared in the comparative example 1 of the present application.
[0032] Figure 3 is an atomic force microscope height topography diagram of the gas sensor prepared in the example 1 and the comparative example 1 of the present application.
[0033] Figure 4 is a response fold line diagram of the UiO-66-NH2 / MoS2 gas sensor prepared in the example 1 of the present application for nitrogen dioxide within a relative humidity range of 35-75%.
[0034] Figure 5 is a response fold line diagram of the single MoS2 gas sensor prepared in the comparative example 1 of the present application for nitrogen dioxide.
[0035] Figure 6 is a response curve diagram of the UiO-66-NH2 / MoS2 gas sensor prepared in the example 1 of the present application for nitrogen dioxide under different relative humidities.
[0036] Figure 7 is the sensing performance test result of the UiO-66-NH2 / MoS2 gas sensor prepared in the example 1 of the present application for different gases. DETAILED DESCRIPTION
[0037] The present application will be described in detail below with reference to the embodiments, so as to facilitate the understanding of the present application by those skilled in the art. It is necessary to point out here that the embodiments are only used to further illustrate the present application and cannot be understood as limiting the protection scope of the present application. Non-essential improvements and adjustments of the present application made by those skilled in the art according to the above description should still fall within the protection scope of the present application. Meanwhile, the raw materials mentioned below are not described in detail, which are all commercially available products; the process steps or preparation methods not mentioned in detail are all known to those skilled in the art.
[0038] As shown in Figure 1 The gas sensor of the present application comprises, from bottom to top, a substrate electrode, a MoS2 nanosheet 130 and a metal organic framework hydrophobic encapsulation layer 140. The substrate electrode comprises a substrate 110, a first electrode 121 and a second electrode 122, the first electrode 121 and the second electrode 122 are separated from each other, and the first electrode 121 and the second electrode 122 are fixed on the substrate 110.
[0039] In some embodiments, the substrate 110 is silicon dioxide, and the first electrode 121 and the second electrode 122 are chromium / gold electrodes.
[0040] In some embodiments, the chromium / gold electrode comprises a chromium layer with a thickness of 3-15 nm on the substrate 110 and a gold layer with a thickness of 30-80 nm on the chromium layer (not shown in the figure).
[0041] In some embodiments, the distance between the first electrode 121 and the second electrode 122 is 5-20 µm. The two sides of the MoS2 nanosheet 130 are respectively overlapped on the first electrode 121 and the second electrode 122, so that the first electrode 121 and the second electrode 122 are in communication with each other.
[0042] In some embodiments, the thickness of the MoS2 nanosheet 130 is 10-100 nm; and the MoS2 nanosheet 130 is prepared by mechanical exfoliation and transferred to the surface of the substrate electrode by dry method.
[0043] In some embodiments, the metal organic framework hydrophobic encapsulation layer 140 is UiO-66-NH2, with a thickness of 1-10 nm, and the UiO-66-NH2 is grown in situ on the surface of the MoS2 nanosheet.
[0044] Example 1 A preparation method of a high-humidity-resistant molybdenum disulfide-based gas sensor, comprising the following steps: (1) Take MoS2 bulk crystal material, and use a piece of blank Scotch tape (first tape) to stick a small amount of MoS2 nanosheet on the surface of the crystal as an initial MoS2 nanosheet. Then use another piece of blank Scotch tape (second tape) to combine with the first tape, so that the second tape covers the surface of the initial MoS2 nanosheet. Press the contact part of the first tape and the second tape with a cotton swab to make them fully contact. Then slowly pull up the first tape (or the second tape) from one side to separate the two tapes. At this time, the surfaces of the first tape and the second tape are both stuck with part of the MoS2 nanosheet. Introduce a new Scotch tape and repeat the above combination and separation process several times until a large number of smooth and flat MoS2 nanosheets are stuck on the Scotch tape.
[0045] (2) Cover a polydimethylsiloxane film on the surface of the Scotch tape with a large number of smooth and flat MoS2 nanosheets prepared in step (1), and press the film with a cotton swab to make it combine with the tape and make close contact. Then slowly pull up the film from one side of the film, at this time the film is stuck with a small amount of MoS2 nanosheet. Place the film under a microscope and observe the quality of the MoS2 nanosheet, and select MoS2 nanosheets with appropriate length and thickness for transfer.
[0046] (3) After selecting the target MoS2 nanosheet (thickness about 27 nm), first turn the film with MoS2 nanosheet upside down, move the target MoS2 nanosheet on the film to the position directly above the chromium / gold electrode pair through the microscope, then slowly adjust the moving platform to make it contact with the substrate where the electrode is located, then press the surface of the film with a cotton swab to make the electrode and the MoS2 nanosheet on the film closely adhere to each other. Slowly pull up the film, and under the action of van der Waals force, the MoS2 nanosheet will remain on the surface of the chromium / gold electrode, thus preparing a single MoS2 gas sensor. Figure 2 From the optical image of the gas sensor, Figure 2 it can be seen that the MoS2 nanosheet is connected to the surfaces of the two chromium / gold electrodes, thereby connecting the two electrodes.
[0047] (4) Mix the zirconium 6 cluster solution with a concentration of 2.4 mmol / L and the 2-amino terephthalic acid solution with a concentration of 2.4 mmol / L in a volume ratio of 1:1 into a culture dish to prepare a ligand mixed solution. Then turn the MoS2 gas sensor prepared in step (3) upside down by 180 degrees and float it on the surface of the ligand mixed solution, and stand for 1 hour of reaction. After the reaction is completed, wash the surface of the electrode of the substrate with deionized water, and dry it at 70°C under vacuum for 1 hour to prepare the UiO-66-NH2 / MoS2 gas sensor of the present embodiment.
[0048] Comparative Example 1 The single MoS2 gas sensor prepared in steps (1)-(3) of Example 1.
[0049] Figure 3 Figure 6 is a height profile of atomic force microscopy of the UiO-66-NH2 / MoS2 gas sensor prepared in Example 1 and the single MoS2 gas sensor prepared in Comparative Example 1. From Figure 3 It can be seen that the thickness of the MoS2 nanosheet in the single MoS2 gas sensor before packaging is about 27.8 nm, and the total thickness of the MoS2 nanosheet and the UiO-66-NH2 packaging layer in the UiO-66-NH2 / MoS2 gas sensor after packaging is about 24.7 nm, and the thickness of the UiO-66-NH2 is about 2.9 nm.
[0050] Performance test The sensing performance of the gas sensors prepared in Example 1 and Comparative Example 1 to nitrogen dioxide was tested respectively, and the test procedure was as follows: (1) The gas sensor was placed on the test table, a direct current voltage of 5-20 V was applied by a Keithley 2450 tester, and was placed in a closed gas sensitive test chamber.
[0051] (2) 500 ppb of nitrogen dioxide with air as the background was introduced into the gas sensitive test chamber, and the change of the electrical signal of the gas sensor under the condition of 75 μW / cm 2 of power density and 405 nm wavelength light was measured.
[0052] (3) After the electrical signal on the Keithley 2450 tester was stable, the gas sensitive test chamber was opened, and the gas sensor was restored to the initial electrical state in the atmospheric environment.
[0053] The change amount of the electrical signal in the above detection process is the response value of the gas sensor. When the concentration of nitrogen dioxide in the to-be-tested gas is unknown, the concentration of nitrogen dioxide in the to-be-tested gas can be calculated according to the response value.
[0054] Figure 4 The room temperature response value of the UiO-66-NH2 / MoS2 gas sensor prepared in Example 1 to 500 ppb of nitrogen dioxide under the condition of 35-75% relative humidity, 75 μW / cm 2 of power density and 405 nm wavelength light. From Figure 4 It can be seen that the response value of the UiO-66-NH2 / MoS2 gas sensor after packaging with the hydrophobic layer to 500 ppb of nitrogen dioxide is about 3.9, and the relative standard deviation under each relative humidity is less than 6%. Figure 5The test results of the single MoS2 gas sensor prepared for Comparative Example 1 under the same conditions. It can be seen from Figure 5 that the response value of the single MoS2 gas sensor without hydrophobic layer packaging can only reach about 0.5, which is nearly 8 times different from the above. It is proved that the anti-humidity performance of the high anti-humidity MoS2-based gas sensor of the present application is related to the packaging layer.
[0055] Figure 6 is the response curve of the UiO-66-NH2 / MoS2 gas sensor prepared in Example 1 to 500 ppb nitrogen dioxide under different relative humidity and power density of 75 μW / cm 2 of 405 nm wavelength light irradiation conditions. It can be seen from Figure 6 that the UiO-66-NH2 / MoS2 gas sensor can realize stable response to nitrogen dioxide of the same concentration under the condition of relative humidity of 35-75%, and the lowest detection limit of nitrogen dioxide can reach 20 ppb, which has a lower detection limit than the existing sensor. It is proved that the high anti-humidity MoS2-based gas sensor of the present application has excellent anti-humidity, stability and reversibility, and has great application prospect in the field of gas sensing.
[0056] Using the same test method as above, the sensing performance of the UiO-66-NH2 / MoS2 gas sensor prepared in Example 1 of the present application to nitrogen dioxide, ammonia, ethanol, formaldehyde, methanol, ethanol and propanol was tested, wherein the concentration of nitrogen dioxide was 500 ppb, and the concentration of the remaining gases was 500 ppm, and the results are shown in Figure 7 . Figure 7 It can be seen that the high anti-humidity MoS2-based gas sensor prepared in the present application has high selectivity to nitrogen dioxide.
[0057] For those skilled in the art to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made without having to undergo creative labor. Therefore, the simple improvements made by those skilled in the art to the present application according to the disclosure of the present application should be within the protection scope of the present application. The above examples are preferred embodiments of the present application, and any similar processes and equivalent changes made should be within the protection scope of the present application.
Claims
1. A gas sensor, characterized in that, From bottom to top, it includes a base electrode, molybdenum disulfide nanosheets, and a metal-organic framework hydrophobic encapsulation layer. The molybdenum disulfide nanosheets are prepared by mechanical exfoliation and transferred to the surface of the base electrode by dry method.
2. The gas sensor according to claim 1, characterized in that, The thickness of the molybdenum disulfide nanosheets is 10-100 nm.
3. The gas sensor according to claim 1, characterized in that, The metal-organic framework hydrophobic encapsulation layer is UiO-66-NH2, and the UiO-66-NH2 is grown in situ on the surface of molybdenum disulfide nanosheets.
4. The gas sensor according to claim 1 or 3, characterized in that, The thickness of the hydrophobic encapsulation layer of the metal-organic framework is 1-10 nm.
5. The gas sensor according to claim 1 or 3, characterized in that, The substrate electrode includes a substrate, a first electrode, and a second electrode. The first electrode and the second electrode are fixed to the surface of the substrate, and the first electrode and the second electrode are connected by overlapping molybdenum disulfide nanosheets.
6. A method for preparing a gas sensor as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) Using a mechanical peeling method, molybdenum disulfide nanosheets are adhered to the molybdenum disulfide bulk crystals with adhesive tape, and then the molybdenum disulfide nanosheets are transferred to a polymer film; (2) After the polymer film is attached to the substrate electrode, it is separated to transfer the molybdenum disulfide nanosheets to the surface of the substrate electrode, thereby obtaining a substrate electrode containing molybdenum disulfide nanosheets. (3) The substrate electrode containing molybdenum disulfide nanosheets is inverted and floated on the surface of the metal-organic framework ligand solution to react and grow a hydrophobic metal-organic framework encapsulation layer in situ on the surface of the molybdenum disulfide nanosheets to obtain the gas sensor.
7. The method for preparing a gas sensor according to claim 6, characterized in that, The metal-organic framework ligand solution contains 2-aminoterephthalic acid and zirconium 6 cluster, the concentration of the metal-organic framework ligand solution is 1.0-5.0 mmol / L, and the volume ratio of the 2-aminoterephthalic acid and zirconium 6 cluster solution is 1:1-1:
3.
8. The method for preparing a gas sensor according to claim 6, characterized in that, The process of adhering molybdenum disulfide nanosheets The process includes the following steps: taking a first tape to adhere initial molybdenum disulfide nanosheets from the molybdenum disulfide bulk crystal, then taking a second tape to combine with the first tape, separating them so that both the first and second tapes have some molybdenum disulfide nanosheets adhered to them, and then introducing a new tape to repeat the above combination and separation process.
9. The application of a gas sensor as described in any one of claims 1-5 in detecting the concentration of nitrogen dioxide.
10. The application according to claim 9, characterized in that, The ambient temperature for the test was room temperature, and the relative humidity was below 75%.