ZIF-8 / SnO2 composite nanomaterial-based gas sensor and preparation method thereof
By combining ZIF-8/SnO2 composite nanomaterial with micro-hot plate chips, the lack of sensors in gas selectivity and response speed is solved, and a gas sensor application with high sensitivity and low power consumption is achieved.
Patent Information
- Application Number
- CN202510337110.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-21
- Publication Date
- 2025-07-11
AI Technical Summary
Existing metal oxide semiconductor gas sensors have shortcomings in gas selectivity and response speed, making it difficult to achieve high sensitivity and specific detection.
ZIF-8/SnO2 composite nanomaterial is used to prepare tin oxide into an ordered sphere-like or sheet-like structure through hydrothermal method to form heterojunctions, and combine with micro-hot plate chip design to improve the sensitivity and selectivity of the sensor.
It improves the sensor's response sensitivity and selectivity to carbon monoxide gas, reduces operating temperature and power consumption, is suitable for large-scale production, and reduces costs.
Smart Images
Figure CN120294079A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of gas sensors, and in particular to a gas sensor based on ZIF-8 / SnO2 composite nanomaterials and a preparation method thereof. Background Art
[0002] Metal oxide semiconductor (MOS) gas sensor is a gas sensor with semiconductor metal oxide as sensitive material. Its gas-sensing mechanism is the reaction of metal semiconductor material gaining and losing electrons with oxygen and target detection gas at high temperature. This sensor generally has the advantages of high sensitivity, fast response time, small size and long life. However, the gas-sensing mechanism of MOS gas sensor also leads to poor specificity of this type of sensor, and it also has non-negligible response to some gases other than target gas. Through doping, morphology control and other technologies, the selectivity of metal oxide sensors can be improved to a certain extent, and their response and recovery speed can be accelerated, but it still cannot fundamentally solve the current problems.
[0003] Metal-Organic Frameworks (MOFs) are a class of porous materials formed by coordination between metal ions or metal clusters and organic ligands, with high chemical and structural tunability, excellent thermal stability, ultra-high porosity and large surface area. MOFs materials have abundant functional sites, including open metal sites and organic ligands, which can interact specifically with target gas molecules to achieve selective adsorption and detection. At the same time, MOFs materials have high specific surface area and adjustable pore size, which improves the response of gas sensors to gases, and the specificity of sensors can be further improved by adjusting the pore size. ZIF-8 is a special metal-organic framework material, composed of metal ions and imidazole ester ligands, with a structure similar to traditional aluminosilicate zeolites. It has inherent porous characteristics, rich functionality, and excellent thermal and chemical stability. Due to its unique structure and properties, it shows great application potential in the field of gas sensors. In view of this, the present invention is proposed. Summary of the invention
[0004] In view of the above shortcomings, the present invention provides a gas sensor based on ZIF-8 / SnO2 composite nanomaterials and a preparation method thereof. The gas-sensitive material on the sensor has the characteristics of being porous and having a large specific surface area, so that the sensor has high specificity and sensitivity to carbon monoxide gas. The specific technical scheme is as follows:
[0005] A gas sensor based on ZIF-8 / SnO2 composite nanomaterials, wherein the ZIF-8 / SnO2 composite nanomaterials are coated on a sensitive area of a micro-hot plate chip of the gas sensor.
[0006] Further, the preparation method of the ZIF-8 / SnO2 composite nanomaterial comprises the following steps:
[0007] (1) Preparation of ZIF-8 material: Dissolve zinc acetate dihydrate in deionized water to obtain a first solution; dissolve 2-methylimidazole in deionized water to obtain a second solution; slowly add the first solution to the second solution to form a mixed solution, place the mixed solution in an oil bath and stir for reaction, after the reaction is completed, centrifuge and wash the product, and dry it under vacuum to obtain ZIF-8 powder;
[0008] (2) Preparation of ZIF-8 / SnO2: Dissolve tin (II) chloride dihydrate in 50 mL of ethylene glycol to obtain a tin precursor solution, add sodium hydroxide to the tin precursor solution, stir for 10 - 15 min, control the mass ratio of tin (II) chloride dihydrate to sodium hydroxide to be (1 - 4):1, then add the ZIF-8 powder, control the mass ratio of tin (II) chloride dihydrate to ZIF-8 to be (8 - 13):1, and then carry out a high-pressure water bath reaction at 150 - 200 °C for 10 - 15 h. After the reaction is completed, centrifuge, wash and dry the product, and calcine it at 180 - 250 °C for 5 - 7 h to obtain ZIF-8 / SnO2 powder.
[0009] Further, in step (1), the concentration of the first solution is 40 - 60 mg / mL.
[0010] Further, in step (1), the concentration of the second solution is 40 - 60 mg / mL.
[0011] Further, in step (1), the temperature of the oil bath reaction is 60 - 80 °C, and the reaction time is 20 - 24 h.
[0012] Further, in step (2), the mass ratio of tin (II) chloride dihydrate to sodium hydroxide is (1 - 3):1.
[0013] Further, in step (2), the mass ratio of tin (II) chloride dihydrate to ZIF-8 is (9 - 11):1.
[0014] Further, in step (2), the calcination temperature is 220 - 240 °C, and the calcination time is 5 - 6 h.
[0015] Further, the coating method of the ZIF-8 / SnO2 composite nanomaterial is as follows: Grind the ZIF-8 / SnO2 composite nanomaterial to obtain a powder with a particle size of 10-500 μm. Dissolve the powder in absolute ethanol, mix evenly to obtain a 50 mg / mL slurry. Coat the slurry on the sensitive area, then anneal it at 350 °C for 4 h, and place it in a sealed gas chamber. Apply electricity to the heating electrodes of the micro-hotplate chip for aging. The voltage during aging is 2.5 V - 3.3 V, and the time is 1 - 2 days to obtain the gas sensor.
[0016] The present invention also provides the application of the gas sensor based on the ZIF-8 / SnO2 composite nanomaterial in the detection of carbon monoxide gas.
[0017] The gas sensing of the present invention includes a micro-hotplate chip. The middle part of the micro-hotplate chip is a sensitive area. The sensitive area is connected to the micro-hotplate surface insulation layer through a suspended beam. The sensitive area of the micro-hotplate chip is coated with the ZIF-8 / SnO2 composite nanomaterial. The sensitive area is also connected with a pair of heating electrodes and a pair of sensitive electrodes, and the sensitive electrodes are connected to an external circuit.
[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0019] 1. The present invention uses the hydrothermal method to composite the ZIF-8 material with tin oxide. By controlling the synthesis conditions (high-pressure water bath reaction at 150 - 200 °C, calcination at 180 - 250 °C), the tin oxide in the prepared ZIF-8 / SnO2 composite nanomaterial forms an ordered arrangement of spherical or flaky structures, which increases the specific surface area and helps improve the sensitivity of the sensor. At the same time, this preparation method can also form a heterojunction between zinc and tin oxide, forming an electron depletion layer, effectively improving the sensitivity of the composite material to carbon monoxide gas response and reducing the optimal operating temperature and other properties.
[0020] 2. The present invention uses ZIF-8 to control a large number of nanomaterials to stack into a desired shape, regulating the overall specific surface area and pore size of the material, which can improve the selectivity of the sensor.
[0021] 3. The present invention composites the ZIF-8 material with tin oxide, uses the organic framework to control a large number of nanomaterials to stack into a desired shape, and regulates the overall specific surface area and pore size of the material, which can improve the selectivity of the sensor.
[0022] 4. The present invention makes the material into the nanoscale, which can improve the sensitivity of the sensor while reducing the volume of the sensor. Coating the material on a low-power micro-hotplate is convenient for the integrated use of the sensor with the circuit board. In addition, the large specific surface area of the nanoscale material helps gas adsorption and desorption.
[0023] 5. The sensitive area of the micro-hotplate of the present invention is connected to the surface insulation layer of the micro-hotplate through a beam. The suspended structure reduces the voltage required for the material to reach the desired working temperature, helps reduce the power consumption of the sensor, and lowers the cost.
[0024] 6. The ZIF-8 / SnO2 composite nanomaterial of the present invention is prepared by a hydrothermal method. The preparation process is simple, and the material can be mass-produced, improving the material preparation efficiency and helping to reduce the cost of the sensor. Brief Description of the Drawings
[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments.
[0026] Figure 1 It is a scanning electron microscope (SEM) image of the composite nanomaterial in Example 1;
[0027] Figure 2 It is a scanning electron microscope (SEM) image of the composite nanomaterial in Example 2;
[0028] Figure 3 It is the response result of the sensor in Example 2 to the carbon monoxide concentration gradient of 50 - 500 ppm;
[0029] Figure 4 It is the selectivity result of the sensor in Example 2 to different gases;
[0030] Figure 5 It is a schematic structural diagram of the gas sensor based on the ZIF-8 / SnO2 composite nanomaterial of the present invention. Detailed Embodiments
[0031] The following will describe the detailed embodiments of the present invention in detail, but it should be understood that the protection scope of the present invention is not limited by the detailed embodiments.
[0032] Example 1
[0033] A gas sensor based on the ZIF-8 / SnO2 composite nanomaterial, as Figure 5 shown. The gas sensor includes a micro-hotplate chip 1. The middle part of the micro-hotplate chip 1 is a sensitive area 4. The sensitive area 4 is connected to the surface insulation layer of the micro-hotplate through a suspended beam 2. The sensitive area 4 of the micro-hotplate chip 1 is coated with the ZIF-8 / SnO2 composite nanomaterial. The sensitive area 4 is also connected with a pair of heating electrodes 3 and a pair of sensitive electrodes 5, and the sensitive electrodes 5 are connected to an external circuit.
[0034] The preparation method of the ZIF-8 / SnO2 composite nanomaterial includes the following steps:
[0035] (1) Preparation of ZIF-8 material: Zinc acetate dihydrate (Zn(OAc)2·2H2O) was used as the zinc source and dissolved in deionized water to form a solution with a concentration of 50 mg / mL; 2-methylimidazole was used as the organic ligand and dissolved in deionized water to form a solution with a concentration of 50 mg / mL; the two solutions were mixed and reacted with stirring in an oil bath at 60 °C for 24 h. After the reaction was completed, the product was centrifuged and washed, and then dried in a vacuum drying oven to obtain ZIF-8 powder.
[0036] (2) Preparation of ZIF-8 / SnO2: Tin chloride dihydrate (SnCl2·2H2O) was used as the tin source and dissolved in an appropriate amount of ethylene glycol to prepare a tin precursor solution. An appropriate amount of sodium hydroxide (NaOH) was added to the solution and stirred for 10 min, controlling the mass ratio of tin chloride dihydrate to sodium hydroxide to be 2:1. The prepared ZIF-8 powder was added to the mixed solution, controlling the mass ratio of tin chloride dihydrate to ZIF-8 to be 10:1. The mixed solution was placed in a high-pressure reaction kettle and reacted in a high-pressure water bath at 180 °C for 12 h. After the reaction was completed, the product was centrifuged, washed, and dried, and calcined at 180 °C for 6 h to obtain the ZIF-8 / SnO2 nanocomposite. Through the observation of a scanning electron microscope, the microscopic morphology of the ZIF-8 / SnO2 nanocomposite is as Figure 1 shown in the figure. The figure shows that the composite material is composed of a large number of spherical nanoparticles. The average size of the nanoparticles is dozens of nanometers. This structure has the characteristics of being porous and having a large specific surface area.
[0037] The coating method of the ZIF-8 / SnO2 composite nanomaterial is as follows: Grind the ZIF-8 / SnO2 composite nanomaterial to obtain a powder with a particle size in the micron range. Dissolve the powder in absolute ethanol and mix evenly to obtain a 50 mg / mL slurry. Coat the slurry on the sensitive area, anneal at 350 °C for 4 h, and place it in a sealed gas chamber. Apply electricity to the heating electrode of the microhotplate chip to age. The voltage during aging is 2.5 V and the time is 2 d to obtain the gas sensor.
[0038] Example 2
[0039] A gas sensor based on ZIF-8 / SnO2 composite nanomaterial, as Figure 5 shown. The gas sensor includes a microhotplate chip 1. The middle part of the microhotplate chip 1 is a sensitive area 4. The sensitive area 4 is connected to the surface insulation layer of the microhotplate through a suspended beam 2. The sensitive area 4 of the microhotplate chip 1 is coated with ZIF-8 / SnO2 composite nanomaterial. The sensitive area 4 is also connected with a pair of heating electrodes 3 and a pair of sensitive electrodes 5. The sensitive electrodes 5 are connected to an external circuit.
[0040] The preparation method of the ZIF-8 / SnO2 composite nanomaterial includes the following steps:
[0041] (1) Preparation of ZIF-8 material: Zinc acetate dihydrate (Zn(OAc)2·2H2O) was used as the zinc source and dissolved in deionized water to form a solution with a concentration of 50 mg / mL; 2-methylimidazole was used as the organic ligand and dissolved in deionized water to form a solution with a concentration of 50 mg / mL. The two solutions were mixed and reacted with stirring in an oil bath at 60 °C for 24 h. After the reaction was completed, the product was centrifuged and washed, and then dried in a vacuum drying oven to obtain ZIF-8 powder.
[0042] (2) Preparation of ZIF-8 / SnO2: Tin chloride dihydrate (SnCl2·2H2O) was used as the tin source and dissolved in an appropriate amount of ethylene glycol to prepare a tin precursor solution. An appropriate amount of sodium hydroxide (NaOH) was added to the solution and stirred for 10 min, controlling the mass ratio of tin chloride dihydrate to sodium hydroxide to be 2:1. The prepared ZIF-8 powder was added to the mixed solution, controlling the mass ratio of tin chloride dihydrate to ZIF-8 to be 10:1. The mixed solution was placed in a high-pressure reaction kettle and reacted in a high-pressure water bath at 180 °C for 12 h. After the reaction was completed, the product was centrifuged, washed, and dried, and calcined at 230 °C for 6 h to obtain the ZIF-8 / SnO2 nanocomposite material. Through the observation of a scanning electron microscope, the microscopic morphology of the final product is as Figure 2 shown. It can be seen that compared with Example 1, due to the change in the calcination temperature, the product has become a structure composed of a large number of flaky nanoparticles. Compared with spheres, the flaky structure has a larger specific surface area.
[0043] The coating method of the ZIF-8 / SnO2 composite nanomaterial is as follows: The ZIF-8 / SnO2 composite nanomaterial is ground to obtain a powder with a particle size in the micron range. The powder is dissolved in absolute ethanol and mixed evenly to obtain a 50 mg / mL slurry. After the slurry is coated on the sensitive area, it is annealed at 350 °C for 4 h and placed in a sealed gas chamber. The heating electrode of the micro-hotplate chip is energized for aging. The voltage during aging is 2.5 V and the time is 2 d to obtain the gas sensor.
[0044] Example 3
[0045] A gas sensor based on the ZIF-8 / SnO2 composite nanomaterial, as Figure 5 shown. The gas sensor includes a micro-hotplate chip 1. The middle part of the micro-hotplate chip 1 is a sensitive area 4. The sensitive area 4 is connected to the surface insulation layer of the micro-hotplate through a suspended beam 2. The sensitive area 4 of the micro-hotplate chip 1 is coated with the ZIF-8 / SnO2 composite nanomaterial. The sensitive area 4 is also connected to a pair of heating electrodes 3 and a pair of sensitive electrodes 5. The sensitive electrodes 5 are connected to an external circuit.
[0046] The preparation method of the ZIF-8 / SnO2 composite nanomaterial includes the following steps:
[0047] (1) Preparation of ZIF-8 material: Using zinc acetate dihydrate (Zn(OAc)2·2H2O) as the zinc source, dissolve it in deionized water to form a solution with a concentration of 60 mg / mL; using 2-methylimidazole as the organic ligand, dissolve it in deionized water to form a solution with a concentration of 40 mg / mL; mix the two solutions and stir and react in an 80 °C oil bath for 20 h. After the reaction is completed, centrifuge and wash the product, and then dry it in a vacuum drying oven to obtain ZIF-8 powder.
[0048] (2) Preparation of ZIF-8 / SnO2: Using tin(II) chloride dihydrate (SnCl2·2H2O) as the tin source, dissolve it in an appropriate amount of ethylene glycol to prepare a tin precursor solution. Add an appropriate amount of sodium hydroxide (NaOH) to the solution and stir for 15 min, controlling the mass ratio of tin(II) chloride dihydrate to sodium hydroxide to be 3:1. Add the prepared ZIF-8 powder to the mixed solution, controlling the mass ratio of tin(II) chloride dihydrate to ZIF-8 to be 9:1. Put the mixed solution into a high-pressure reaction kettle and carry out a high-pressure water bath reaction at 150 °C for 15 h. After the reaction is completed, centrifuge, wash, and dry the product, and calcine it at 200 °C for 6 h to obtain the ZIF-8 / SnO2 nanocomposite material.
[0049] The coating method of the ZIF-8 / SnO2 composite nanomaterial is as follows: Grind the ZIF-8 / SnO2 composite nanomaterial to obtain powder with a micron-sized particle size. Dissolve the powder in absolute ethanol and mix evenly to obtain a 50 mg / mL slurry. After coating the slurry on the sensitive area, anneal it at 350 °C for 4 h and place it in a sealed gas chamber. Apply electricity to the heating electrode of the microhotplate chip for aging. The voltage during aging is 3.3 V and the time is 1 d to obtain the gas sensor.
[0050] Gas sensing performance test
[0051] Sensitivity test: Use a gas diluter to output the gas with the required concentration to test the gas sensing performance. The response of the gas sensor prepared in Example 2 to carbon monoxide with a concentration of 50 - 500 ppm is as Figure 3 shown. The calculation method of the response is the ratio R of the resistance value of the sensor in air to the resistance value of the sensor in the test gas a / R g . It can be seen that as the concentration of carbon monoxide increases, the response of the sensor gradually increases.
[0052] Selectivity test: Tested the response of the gas sensor prepared in Example 2 to carbon monoxide, hydrogen, ethylene, ethane, and methane with a concentration of 500 ppm. The results are as Figure 4As shown, the figure shows that the sensor of the present invention has a significantly higher response to carbon monoxide.
[0053] The foregoing description of specific exemplary embodiments of the invention has been presented for purposes of illustration and example. It is not intended to limit the invention to the precise form disclosed, and obviously, many modifications and variations are possible in light of the above teaching. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the invention and its practical application so that those skilled in the art can implement and utilize the various different exemplary embodiments of the invention, as well as various different selections and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.
Claims
1. A gas sensor based on ZIF-8 / SnO2 composite nanomaterials, characterized in that, The sensitive area of the micro-hotplate chip of the gas sensor is coated with ZIF-8 / SnO2 composite nanomaterials.
2. The gas sensor based on the ZIF-8 / SnO2 composite nanomaterial according to claim 1, characterized in that, The preparation method of the ZIF-8 / SnO2 composite nanomaterials comprises the following steps: (1) Preparation of ZIF-8 material: Dissolve zinc acetate dihydrate in deionized water to obtain a first solution; dissolve 2-methylimidazole in deionized water to obtain a second solution; slowly add the first solution to the second solution to form a mixed solution, place the mixed solution in an oil bath and stir for reaction, after the reaction is completed, centrifuge and wash the product, and dry it under vacuum to obtain ZIF-8 powder; (2) Preparation of ZIF-8 / SnO2: Dissolve tin dichloride dihydrate in ethylene glycol to obtain a tin precursor solution, add sodium hydroxide to the tin precursor solution and stir, control the mass ratio of tin dichloride dihydrate to sodium hydroxide to be (1-4):1, then add the ZIF-8 powder, control the mass ratio of tin dichloride dihydrate to ZIF-8 to be (8-13):1, then carry out a high-pressure water bath reaction at 150-200 °C for 10-15 h, after the reaction is completed, centrifuge, wash and dry the product, and calcine it at 180-250 °C for 5-7 h to obtain ZIF-8 / SnO2 powder.
3. A gas sensor based on a ZIF-8 / SnO2 composite nanomaterial according to claim 2, characterized in that, In step (1), the concentration of the first solution is 40-60 mg / mL.
4. The gas sensor based on the ZIF-8 / SnO2 composite nanomaterial according to claim 2, wherein, In step (1), the concentration of the second solution is 40-60 mg / mL.
5. A gas sensor based on a ZIF-8 / SnO2 composite nanomaterial according to claim 2, characterized in that, In step (1), the temperature of the oil bath reaction is 60-80 °C, and the reaction time is 20-24 h.
6. The gas sensor based on the ZIF-8 / SnO2 composite nanomaterial according to claim 2, characterized in that, In step (2), the mass ratio of tin dichloride dihydrate to sodium hydroxide is (1-3):
1.
7. A gas sensor based on a ZIF-8 / SnO2 composite nanomaterial according to claim 2, characterized in that, In step (2), the mass ratio of tin dichloride dihydrate to ZIF-8 is (9-11):
1.
8. The gas sensor based on the ZIF-8 / SnO2 composite nanomaterial according to claim 2, characterized in that, In step (2), the calcination temperature is 220-240 °C, and the calcination time is 5-6 h.
9. The gas sensor based on the ZIF-8 / SnO2 composite nanomaterial according to claim 1, characterized in that, The coating method of the ZIF-8 / SnO2 composite nanomaterials is as follows: Grind the ZIF-8 / SnO2 composite nanomaterials to obtain powder with a particle size in the micron range, dissolve the powder in absolute ethanol, mix evenly to obtain a slurry, coat the slurry on the sensitive area, place it in a sealed gas chamber, and energize the heating electrode of the micro-hotplate chip for aging to obtain the gas sensor.
10. Application of a gas sensor based on ZIF-8 / SnO2 composite nanomaterials according to any one of claims 1 to 9 in the detection of carbon monoxide gas.