A gas sensor for detecting dimethyl trisulfide, its preparation method, and its application.

Abstract

This invention discloses a gas sensor for detecting dimethyl trisulfide (DMT). It uses Cu-doped Co3O4 porous nanorods as the sensing element, obtained by coating a dispersion of Co3O4 onto an electrode surface and then drying it. This invention employs Cu-doping Co3O4 combined with porous structure optimization to significantly increase the interaction between DMT molecules on the sensor surface, effectively ensuring the sensor's selectivity and sensitivity for DMT, achieving efficient detection. Furthermore, the preparation method is simple, reproducible, and the detection method is simple and accurate, making it suitable for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of gas sensor technology, specifically relating to a gas sensor for detecting dimethyl trisulfide and its preparation method. Background Technology

[0002] Flavor is an important product attribute and characteristic marker of edible vegetable oils, with characteristic flavor components mainly consisting of aldehydes, alcohols, pyrazines, and sulfides. Studies on the formation pathways and mechanisms of different flavor substances in vegetable oils have revealed that sulfides have low odor thresholds and are an important class of key flavor compounds; their content best reflects the characteristics and quality changes of oil products. Currently, the detection of these flavor substances mainly relies on analytical equipment such as gas chromatography-mass spectrometry (GC-MS). However, due to the low chemical activity of these sulfides (such as dimethyl trisulfide), high-sensitivity detection presents certain challenges.

[0003] Gas sensors based on semiconductor metal oxides have been widely used in various fields such as industry, environmental monitoring, and food detection due to their advantages such as small size, low power consumption, and good stability. However, due to the limitations of the gas-sensing mechanism, most metal oxide gas sensors typically respond to multiple gases. When detecting mixed gases or in the presence of interfering gases, it is difficult to effectively identify and detect target components, especially for low-activity sulfide substances. Summary of the Invention

[0004] The main objective of this invention is to provide a highly selective and sensitive gas sensor for detecting dimethyl trisulfide, addressing the problems and shortcomings of existing technologies.

[0005] Another objective of this invention is to provide a method for preparing and applying the above-mentioned dimethyl trisulfide gas sensor, which involves simple preparation steps, is easy to operate, and is suitable for widespread application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A gas sensor for detecting dimethyl trisulfide (DMT) is disclosed, wherein the DMT gas sensor uses Cu-doped Co3O4 porous nanorods as the sensing element; the pore size of the Cu-doped Co3O4 porous nanorods is 2–50 nm, the length is 2–10 μm, and the diameter is 0.5–2 μm; the gas sensor uses the porous Cu-doped Co3O4 material as the sensing element, and by optimizing its microstructure and porous structure, more catalytic oxidation active sites are constructed on the surface, promoting the specific adsorption and catalytic oxidation reaction of low-activity DMT molecules on the surface of the porous Cu-doped Co3O4 material, effectively ensuring the specific detection of DMT molecules and improving its detection sensitivity.

[0008] In the above scheme, the gas sensor for detecting methyl trisulfide comprises several sensitive layers composed of Cu-doped Co3O4 porous nanorod material.

[0009] Furthermore, the sensitive layer is formed by coating the electrode surface with a dispersion of Cu-doped Co3O4 porous nanorod material and then drying it.

[0010] Furthermore, the gas sensor for detecting methyl trisulfide contains 2 to 7 sensitive layers.

[0011] Optionally, the resistance of the dimethyl trisulfide gas sensor is 100 to 1000 kΩ.

[0012] Optionally, the resistance value of the dimethyl trisulfide gas detection gas sensor is selected from any value among 100KΩ, 200KΩ, 300KΩ, 500KΩ, 600KΩ, 800KΩ, and 1000KΩ, or a range between any two of the above.

[0013] In the above scheme, the Cu-doped Co3O4 porous nanorod material is obtained by solvothermal reaction and annealing using cobalt salt, copper salt, organic ligand, and solvent as the main raw materials; the specific preparation steps are as follows:

[0014] 1) Disperse cobalt salt, copper salt and organic ligand in solvent to obtain a well mixed dispersion;

[0015] 2) The obtained dispersion was subjected to a solvothermal reaction, followed by washing and drying;

[0016] 3) Anneal the obtained dried product in air to obtain Cu-doped Co3O4 porous nanorod material.

[0017] Optionally, the cobalt salt is selected from at least one of cobalt nitrate, cobalt acetate, etc.

[0018] Optionally, the copper salt is selected from copper nitrate, copper chloride, etc.

[0019] Optionally, the organic ligand may be 2-methylimidazole or the like.

[0020] Optionally, the molar ratio of the cobalt salt to the organic ligand is 1:1 to 32.

[0021] Furthermore, the molar ratio of the cobalt salt to the organic ligand is selected from any value of 1:1, 1:2, 1:4, 1:8, 1:16, 1:32 or a range between any two of the above.

[0022] Optionally, the molar ratio of the copper salt to the cobalt salt is 1:20 to 100.

[0023] Furthermore, the molar ratio of the copper salt to the cobalt salt is selected from any value of 1:20, 1:40, 1:60, 1:80, 1:100 or a range between any two of the above.

[0024] Optionally, the solvent is selected from one or more of water, ethanol, methanol, etc.

[0025] Optionally, the ratio of the cobalt salt to the solvent is 0.1–2.5 mol: 3–60 mL.

[0026] Optionally, the temperature of the solvothermal reaction is 60–180°C, and the time is 12–20 h.

[0027] Optionally, the annealing temperature is 300–600°C, and the annealing time is 2–6 hours.

[0028] Furthermore, the annealing step employs a heating regime comprising: first, heating to 150–200°C at a rate of 2–5°C / min and holding at that temperature for 1–2 hours; then heating to 300–600°C at a rate of 1–3°C / min and holding at that temperature for 2–6 hours.

[0029] This invention also provides a method for preparing a dimethyl trisulfide gas detection sensor, comprising the following steps:

[0030] A dispersion of Cu-doped Co3O4 porous nanorod material was coated onto the electrode surface and allowed to dry naturally at room temperature to obtain the dimethyl trisulfide gas sensor.

[0031] Optionally, the coating may be applied by means such as drop coating.

[0032] Optionally, the solvent used in the dispersion of Cu-doped Co3O4 porous nanorod material is selected from at least one of ethanol, methanol, acetone, acetonitrile, toluene, and n-hexane; the mass-to-volume ratio of Cu-doped Co3O4 porous nanorod material to solvent is 2-20 mg: 0.5-20 mL.

[0033] Optionally, for a unit area of ​​electrode surface, the droplet amount of Cu-doped Co3O4 porous nanorod material dispersion used is 0.002–0.006 mL / cm². 2 .

[0034] Optionally, the number of times the drop is applied is 2 to 8.

[0035] Optionally, the room temperature natural drying conditions are 15–30°C and 10–90% RH.

[0036] The present invention also provides an application method for the gas sensor for detecting dimethyl trisulfide described above, wherein the operating temperature is 100-200°C and the concentration of dimethyl trisulfide that can be detected is as low as 1-100 ppm.

[0037] Furthermore, the gas sensor for detecting dimethyl trisulfide exhibits high selectivity for dimethyl trisulfide under complex multi-gas conditions, including other gases such as alcohols and aldehydes.

[0038] The dimethyl trisulfide (DMT) gas sensor of this invention uses cobalt salts, copper salts, and organic ligands as main raw materials. Through hydrothermal treatment and annealing, porous Cu-doped Co3O4 nanorods are synthesized. These nanorods serve as the sensing element, enhancing the interaction of DMT molecules on their surface to achieve high selectivity and sensitivity. The Cu-doped Co3O4 porous nanorods are deposited on the electrode surface using a solution coating process to fabricate a gas sensor for the detection of the flavor compound DMT. The resulting sensor exhibits excellent response to DMT gas, with detectable concentrations as low as 10 ppb. Furthermore, it demonstrates selectivity in the presence of other organic gases. This sensor can serve as an effective tool for detecting the flavor of samples such as vegetable oils and for assessing the quality of edible vegetable oil samples.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] 1) This invention uses Cu-doped porous Co3O4 material as the sensing element to enhance the specific interaction of dimethyl trisulfide molecules on its surface, which can effectively ensure the selectivity of the sensing element.

[0041] 2) This invention achieves high sensitivity detection of dimethyl trisulfide gas by optimizing the surface pore size structure and Cu doping with Co3O4.

[0042] 3) The preparation and application methods of the sensor described in this invention are simple, reliable, easy to operate, and have good practicality. Attached Figure Description

[0043] Figure 1 Transmission electron microscope image of the porous Cu-doped Co3O4 nanomaterial obtained in Example 1;

[0044] Figure 2 The N2 adsorption-desorption curves and pore size distribution of the Cu-doped Co3O4 nanomaterials obtained in Example 1 are shown.

[0045] Figure 3 The response of the two-layer sensitive membrane sensor obtained in Example 1 to 10 ppb dimethyl trisulfide gas is shown.

[0046] Figure 4 The scanning electron microscope (SEM) image and XRD pattern of the porous Cu-doped Co3O4 nanomaterial obtained in Example 2 are shown.

[0047] Figure 5 The N2 adsorption-desorption curves and pore size distribution of the porous Cu-doped Co3O4 material in Example 2 are shown.

[0048] Figure 6 The response of the 5-layer sensitive membrane sensor obtained in Example 2 to 20 ppb dimethyl trisulfide gas is shown. Detailed Implementation

[0049] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. These descriptions are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention.

[0050] Unless otherwise specified, all raw materials used in the following embodiments were purchased commercially.

[0051] In the following embodiments, the gas sensor uses porous Cu-doped Co3O4 nanorods as the sensing material to achieve high-sensitivity detection of low concentrations of dimethyl trisulfide gas; the preparation steps of the porous Cu-doped Co3O4 material are as follows:

[0052] 1) Disperse cobalt salt, copper salt and 2-methylimidazole evenly in 40 mL of deionized water at a molar ratio of 1:0.02:1 to 32;

[0053] 2) Transfer all the solution to a 50 mL PTFE-lined autoclave and maintain it at 60–180 °C for 12 hours;

[0054] 3) The precipitate was collected by centrifugation and washing with deionized water several times. Finally, it was dried overnight at 60°C and annealed at 300–600°C in air atmosphere for 2 hours to obtain the porous Co3O4 nanorods.

[0055] Individual sensors were fabricated using a spin-coating method, with the specific steps as follows:

[0056] 1) Take 2-20 mg of porous Cu-doped Co3O4 material and uniformly disperse it in 0.5-20 mL of solvent (one or more of ethanol, methanol, acetone, acetonitrile, toluene, and n-hexane);

[0057] 2) Take a certain volume of the dispersed porous Cu-doped Co3O4 material described in step 1) and drop it onto the surface of 2 to 8 planar interdigitated electrodes, and dry it thoroughly at room temperature to construct a porous Cu-doped Co3O4 sensitive film; add the dispersion liquid to the surface of different ceramic tube interdigitated electrodes a different number of times to obtain multiple sensitive films with different thicknesses and surface densities; thus, the gas sensor is obtained.

[0058] The gas sensor operates at 100–200°C and has a resistance of 100–1000 kΩ in air.

[0059] Example 1

[0060] A gas sensor for detecting dimethyl trisulfide, the preparation method of which includes the following steps:

[0061] 1) Disperse 2.5 mmol of cobalt nitrate hexahydrate, 0.05 mmol of copper nitrate trihydrate, and 40 mmol of 2-methylimidazole into 40 mL of deionized water and mix thoroughly under magnetic stirring;

[0062] 2) Transfer all the solution to a 50 mL polytetrafluoroethylene-lined autoclave and keep it at 120 °C for 12 h;

[0063] 3) Collect the precipitate by centrifugation and washing with deionized water several times; dry it overnight at 60℃; in an air atmosphere, first heat it to 200℃ at a rate of 5℃ / min and hold it for 2h, then heat it to 500℃ at a rate of 3℃ / min and hold it for 2h to obtain Cu-doped Co3O4 porous nanorod material.

[0064] 4) 5 mg of the prepared Cu-doped Co3O4 porous nanorod material was ultrasonically dispersed into 5 mL of ethanol to obtain a nanorod dispersion.

[0065] 5) Take 5 μL of the obtained nanorod dispersion and add 5 μL of the dispersion dropwise to 5 ceramic tube interdigitated electrodes (ceramic tube length is 4 mm, outer diameter is 1.2 mm, wall thickness is 0.2 mm, and the channel of the two pairs of gold interdigitated electrodes is 2 mm) 1, 2, ... 5 times respectively to obtain 5 sensors with 1 layer, 2 layers, ... 5 layers of sensitive film respectively; The specific steps for preparing the single layer of sensitive film are as follows: drop the porous Co3O4 nanorod dispersion onto the surface of a ceramic tube interdigitated electrode and place it at room temperature (25°C) to dry naturally for 6 h until the organic solvent is completely evaporated to construct a single layer of sensitive film.

[0066] Figure 1 The image shown is a transmission electron microscope (TEM) image of the Cu-doped Co3O4 porous nanomaterial obtained in this embodiment. It can be seen that the obtained material exhibits a nanorod-like structure with a length of about 5 to 7 μm and an average diameter of about 1 μm for a single nanorod, thus demonstrating a porous structure. Figure 2 The pore size distribution further proves that its surface pore size is 2-50 nm, with the surface pore size concentrated at 30.1 nm.

[0067] The sensors with different numbers of sensitive film layers obtained in this embodiment exhibit resistance values ​​ranging from 100 to 1000 kΩ under a heating condition of 150°C. The sensor's response value is defined as S = R. g / R a , where R a R g These are the resistance values ​​of the sensor in air and the gas being measured, respectively.

[0068] The five gas sensors prepared in this embodiment were used to test the sensitivity response performance of dimethyl trisulfide (DMT). The operating temperature of the sensors was 150°C. The results showed that the highest response value to DMT was obtained when the porous Cu-doped Co3O4 sensor was spin-coated twice. Figure 3 As shown, the sensor with optimized film thickness (spin-coated twice) can achieve a significant response to 10 ppb dimethyl trisulfide gas; it can also perform preliminary identification of the flavor and quality of samples such as edible vegetable oils.

[0069] Further testing showed that the gas sensor for detecting dimethyl trisulfide obtained in this embodiment still exhibits high selectivity for dimethyl trisulfide under conditions containing a variety of complex gases (including formaldehyde, methanol, ethanol, etc.).

[0070] Example 2

[0071] A gas sensor for detecting dimethyl trisulfide, the preparation method of which includes the following steps:

[0072] 1) Disperse 2 mmol of cobalt nitrate hexahydrate, 0.02 mmol of copper nitrate trihydrate, and 60 mmol of 2-methylimidazole into 40 mL of methanol and mix thoroughly under magnetic stirring;

[0073] 2) Transfer all the solution to a 50 mL polytetrafluoroethylene-lined autoclave and keep it at 80 °C for 12 h;

[0074] 3) Collect the precipitate by centrifugation and washing with methanol several times; dry it overnight at 60℃; in an air atmosphere, first heat it to 150℃ at a rate of 5℃ / min and hold it for 2 hours, then heat it to 300℃ at a rate of 1℃ / min and hold it for 2 hours to obtain Cu-doped Co3O4 porous nanorod material.

[0075] 4) 2 mg of the prepared Cu-doped Co3O4 porous nanorod material was uniformly dispersed in 10 mL of ethanol by ultrasonication to obtain a nanorod dispersion.

[0076] 5) Take 5 μL of the obtained nanorod dispersion and drop 5 μL of the dispersion onto 5 ceramic tube interdigitated electrodes (ceramic tube length is 4 mm, outer diameter is 1.2 mm, wall thickness is 0.2 mm, and the channel of the two pairs of gold interdigitated electrodes is 2 mm) 1, 2, ... 5 times respectively to obtain 5 sensors with 1 layer, 2 layers, ... 5 layers of sensitive film thickness; the preparation steps of the single layer of sensitive film are as follows: drop the porous Co3O4 nanorod dispersion onto the surface of one ceramic tube interdigitated electrode and place it at room temperature (25°C) to dry naturally for 6 h until the organic solvent is completely evaporated to construct a sensitive film.

[0077] Figure 4 The image shown is a scanning electron microscope (SEM) image of the Cu-doped Co3O4 porous nanomaterial obtained in this embodiment. It can be seen that the obtained material exhibits a nanorod-like structure with a length of approximately 0.5–3 μm, a diameter of 200–500 nm for a single nanorod, and a surface pore size of 5–50 nm. Figure 5 The N2 adsorption-desorption experiment further confirmed that its surface pore size is concentrated at 12 nm.

[0078] The sensor obtained in this embodiment exhibits a resistance value ranging from 100 to 1000 kΩ under a heating condition of 180°C. The sensor's response value is defined as S = R. g / R a , where R a R g These are the resistance values ​​of the sensor in air and the gas being measured, respectively.

[0079] Five gas sensors prepared in this embodiment were used to test the sensitivity response performance of dimethyl trisulfide (DMT). The operating temperature of the sensors was 180°C. The results showed that the highest response value to DMT was obtained when the porous Cu-doped Co3O4 sensor was spin-coated five times. Figure 6 As shown, the sensor with optimized film thickness (spin-coated 5 times) can achieve a significant response to 20 ppb dimethyl trisulfide gas, enabling preliminary identification of oil flavor and quality.

[0080] Further testing showed that the gas sensor for detecting dimethyl trisulfide obtained in this embodiment still exhibits high selectivity for dimethyl trisulfide under conditions containing a variety of complex gases (including formaldehyde, methanol, ethanol, etc.).

[0081] Comparative Example 1

[0082] A gas sensor for detecting dimethyl trisulfide is prepared in a manner largely similar to that of Example 1, except that the corresponding copper salt (copper nitrate trihydrate) is not introduced during the preparation process.

[0083] The results show that the obtained sensor is almost unresponsive to the target gas (dimethyl trisulfide).

[0084] Comparative Example 2

[0085] A gas sensor for detecting dimethyl trisulfide is prepared in a manner similar to that of Example 1, except that the annealing step in step 3) is performed by directly heating the sensor to 500°C at a rate of 5°C / min in air and holding it therefore for 2 hours to obtain porous Co3O4 nanorods.

[0086] The results showed that the obtained sensor did not respond to dimethyl trisulfide.

[0087] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A gas sensor for detecting dimethyl trisulfide, characterized in that, The dimethyl trisulfide gas sensor uses Cu-doped Co3O4 porous nanorods as the sensing element; the pore size of the Cu-doped Co3O4 porous nanorods is 2-50 nm; the length is 2-10 μm; and the diameter is 0.5-2 μm.

2. The gas sensor according to claim 1, characterized in that, The gas sensor for detecting methyl trisulfide comprises several sensitive layers composed of Cu-doped Co3O4 porous nanorod material.

3. The gas sensor according to claim 1, characterized in that, The Cu-doped Co3O4 porous nanorod material is obtained by solvothermal reaction and annealing using cobalt salt, copper salt, organic ligand, and solvent as the main raw materials.

4. The gas sensor according to claim 3, characterized in that, The cobalt salt is at least one of cobalt nitrate and cobalt acetate; the copper salt is one of copper nitrate and copper chloride; and the organic ligand is 2-methylimidazole.

5. The gas sensor according to claim 3, characterized in that, The molar ratio of cobalt salt to organic ligand is 1:1 to 32; the molar ratio of copper salt to cobalt salt is 1:20 to 100.

6. The gas sensor according to claim 3, characterized in that, The solvothermal reaction is carried out at a temperature of 60–180°C for 12–20 h; the annealing temperature is 300–600°C for 2–6 h.

7. The gas sensor according to claim 3, characterized in that, The annealing step employs a heating regime comprising: first, heating to 150–200°C at a rate of 2–5°C / min and holding at that temperature for 1–2 hours; then heating to 300–600°C at a rate of 1–3°C / min.

8. The method for preparing the gas sensor for detecting dimethyl trisulfide according to claim 1, characterized in that, The process includes the following steps: coating a dispersion of Cu-doped Co3O4 porous nanorod material onto the electrode surface and drying it at room temperature to obtain the gas sensor for detecting dimethyl trisulfide.

9. The preparation method according to claim 8, characterized in that, The solvent used in the dispersion of the Cu-doped Co3O4 porous nanorod material is at least one of ethanol, methanol, acetone, acetonitrile, toluene, and n-hexane; the mass-volume ratio of the Cu-doped Co3O4 porous nanorod material to the solvent is 2-20 mg: 0.5-5 mL.

10. A method for applying the gas sensor for detecting dimethyl trisulfide according to any one of claims 1 to 7 or the gas sensor for detecting dimethyl trisulfide obtained by the preparation method according to any one of claims 8 to 9, characterized in that, Its operating temperature is 100–200℃; the concentration of dimethyl trisulfide detected is as low as 1–100 ppm.

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