Noble metal COF-LZU MOS quantum grain carbon nanotube composite film sensor and preparation method

Abstract

The application discloses a kind of noble metal COF-LZU MOS quantum grain carbon nanotube composite film sensor and preparation method, the composite film with carbon nanotube as substrate, metal oxide semiconductor quantum grain, covalent organic framework compound COF-LZU and noble metal are sequentially loaded on substrate, the sensor with sensor device as substrate, noble metal COF-LZU MOS quantum grain carbon nanotube composite film is deposited on the surface of substrate, and can be used to detect acetone.The application uses noble metal COF-LZU MOS quantum grain carbon nanotube composite film as sensitive layer and applies in acetone (CP) gas-sensitive sensor, the composite film has low working temperature, high sensitivity to gas, high selectivity to acetone, good repeatability, good stability, low cost, simple preparation method, and can be mass-produced.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of sensors, in particular to a noble metal@COF-LZU@MOS quantum grain@carbon nanotube composite film sensor and a preparation method. BACKGROUND

[0002] Real-time detection of ambient air quality has become a frontier research direction of gas sensors. Acetone (CP) is a typical biomarker of diabetes. In recent years, gas sensors based on metal oxide semiconductors (MOS) have become a research hotspot in the field of acetone detection due to their controllable physical and chemical properties, low manufacturing cost, fast response speed, and low detection cost. It is worth noting that two challenges should be solved for MOS sensing materials: 1. In a high relative humidity (RH) environment, the performance of the sensing material will decrease due to the reaction of water vapor (H2O) with the adsorbed cations on the material surface to generate inactive hydroxyl (OH), and the influence of water vapor on the sensor device should be reduced or eliminated; 2. There are various volatile organic compounds in breath detection, and quantum-based MOS sensors are easily disturbed and contaminated during the detection process. Therefore, it is necessary to improve the sensitivity and selectivity of the acetone detection sensor device. SUMMARY

[0003] The application aims to provide a noble metal@COF-LZU@MOS quantum grain@carbon nanotube composite film with low working temperature, high sensitivity, high selectivity to acetone, good repeatability, good stability, low cost and simple preparation method, and the application also provides a sensor based on the noble metal@COF-LZU@MOS quantum grain@carbon nanotube composite film and a preparation method thereof.

[0004] Technical scheme: The noble metal@COF-LZU@MOS quantum grain@carbon nanotube composite film comprises a carbon nanotube as a substrate, metal oxide semiconductor quantum grains, a COF-LZU covalent organic framework compound and a noble metal loaded on the substrate in sequence.

[0005] Further, the molar ratio of the carbon nanotube, the metal oxide semiconductor MOS quantum grain, the COF-LZU covalent organic framework compound and the noble metal in the composite film is 32-38%:29-37%:20-30%:5-9%; the average diameter of the carbon nanotube is 40-50 nm, the average wall thickness of the carbon nanotube is 10-20 nm, the average particle size of the metal oxide semiconductor quantum grain is 3-5 nm, and the average thickness of the film layer formed by the COF-LZU covalent organic framework compound is 5-17 nm.

[0006] The present invention relates to a sensor based on the above-mentioned noble metal@COF-LZU@MOS quantum grains@carbon nanotube composite film, which uses the sensor device as a substrate and deposits a noble metal@COF-LZU@MOS quantum grains@carbon nanotube composite film on the substrate surface.

[0007] Furthermore, the sensor is used to detect acetone gas, and the average thickness of the noble metal@COF-LZU@MOS quantum grains@carbon nanotube composite film is 600-700 nm.

[0008] The method for fabricating a sensor based on a noble metal@COF-LZU@MOS quantum grain@carbon nanotube composite film of the present invention includes the following steps:

[0009] (1) A carbon nanotube substrate is prepared on the surface of the sensor device to obtain a sensor device loaded with a carbon nanotube substrate;

[0010] (2) The sensor device loaded with carbon nanotube substrate is immersed in metal oxide semiconductor precursor solution for dip coating, taken out and dried, and then placed in a sealed container for water vapor-assisted crystallization treatment. After treatment, glow discharge treatment is performed to obtain the sensor device loaded with metal oxide semiconductor@carbon nanotube composite film.

[0011] (3) The sensor device loaded with metal oxide semiconductor@carbon nanotube composite film is immersed in the precursor solution of covalent organic framework compound COF-LZU for dip coating, taken out and vacuum dried, and then subjected to organic solvent vapor-assisted crystallization treatment, cleaned and dried to obtain the sensor device loaded with covalent organic framework compound COF-LZU@MOS quantum grains@carbon nanotube composite film.

[0012] (4) Under a protective gas, the sensor device loaded with the covalent organic framework compound COF-LZU@MOS quantum grains@carbon nanotube composite film is immersed in a mixed solution of noble metal salts for dip coating, dried, placed in an argon protective atmosphere, and subjected to thermal evaporation in organic solvent vapor. After cleaning and drying, it is then subjected to glow discharge treatment to obtain the sensor based on the noble metal@COF-LZU@MOS quantum grains@carbon nanotube composite film.

[0013] Further, in step (1), the step of preparing a carbon nanotube substrate on the surface of the sensor device is as follows: the sensor device is placed in an alumina ceramic boat, and together they are placed in the middle of a quartz tube in a tubular furnace. N2 is introduced into the quartz tube, and the temperature is raised to the reaction temperature. Then, carbon-containing gas methane is introduced to provide an additional carbon source and a nitrogen-hydrogen mixture to carry out the deposition reaction. The carbon-containing gas decomposes to generate carbon nanotubes, which are deposited on the surface of the sensor device, thus obtaining a sensor device loaded with a carbon nanotube substrate; the flow rate of N2 is 50-100 ml / min. The heating parameters are as follows: uniform heating within 30-60 min; the reaction temperature is 750-950℃, preferably 800-900℃; the flow rate of carbon-containing gas is 15-35 ml / min, preferably 15 ml / min; the flow rate of nitrogen-hydrogen mixed gas is 15-20 ml / min; the deposition reaction time is 1-3 h, preferably 1.5-2.5 h; the average diameter of the generated carbon nanotubes is 40-50 nm, and the average wall thickness of the carbon nanotubes is 10-20 nm.

[0014] Further, in step (2), the preparation method of the metal oxide semiconductor precursor solution is as follows: dissolve the metal oxide semiconductor precursor in an organic solvent, add a surfactant and mix evenly to obtain a precursor sol solution; then, add hydrochloric acid dropwise into the precursor solution and disperse it ultrasonically using ultrasound to obtain the metal oxide semiconductor precursor solution; the metal oxide semiconductor is zinc dichloride, ferric chloride, titanium tetrachloride or tin tetrachloride, preferably zinc dichloride or ferric chloride; the organic solvent is anhydrous isopropanol, anhydrous butanol or anhydrous ethanol, preferably anhydrous isopropanol, and the mass of the metal oxide semiconductor precursor is related to the organic solvent. The volume ratio of the agent is 1.2-2.4g:6-12ml, preferably 1.2-2g:6-10ml, and the surfactant is P123, F127, or Brij35, preferably P123; the water vapor crystallization treatment is as follows: the temperature of the sealed container is controlled at 100-180℃, the relative humidity inside the sealed container is 75-95%, and the reaction time is 40-50h, preferably, the temperature of the sealed container is controlled at 140-150℃, and the relative humidity inside the sealed container is 90-95%; the glow discharge treatment is as follows: oxygen glow discharge treatment is performed at a power of 100-300W for 10-12min.

[0015] Further, in step (3), the preparation method of the covalent organic framework compound COF-LZU precursor solution is as follows: in a protective gas, pyromellitic aldehyde and p-phenylenediamine are dissolved in anhydrous dioxane to obtain a mixed solution; under ultrasonic assistance, an aqueous acetic acid solution is added to the mixed solution, ultrasonically treated, and then vacuumed to obtain the solution; the molar ratio of pyromellitic aldehyde and p-phenylenediamine is 1:1-3, preferably 1:3; the organic solvent vapor-assisted crystallization treatment method is as follows: exposed to an anhydrous dioxane at a temperature of 120-150℃ and a pressure of 50-100kPa under a protective atmosphere for 20-60h, preferably at a temperature of 120-130℃ and a pressure of 65-70kPa under a protective atmosphere for 30-35h.

[0016] Further, in step (4), the method for preparing the noble metal mixed solution is as follows: 30-50 mg of noble metal salt is added to 3-6 ml of organic solvent, and after stirring, a homogeneous mixture is formed to obtain the noble metal mixed solution; preferably, the mass of the noble metal salt is 30-40 mg, and the volume of the organic solvent is 4-6 ml; the noble metal salt is PdCl2 or PtCl4, and the organic solvent is isopropanol; the thermal evaporation treatment in the organic solvent vapor is as follows: under argon protection, exposed to isopropanol vapor at a temperature of 100-135℃ and a pressure of 50-100 kPa for 18-54 h, preferably exposed to isopropanol vapor at a temperature of 100-110℃ and a pressure of 90-100 kPa for 20-24 h; the glow discharge treatment is as follows: argon plasma cleaning is performed with a power of 100-300 W and a plasma cleaning time of 5-20 min.

[0017] Further, in steps (2) to (4), the parameters for the lifting coating are: lifting speed of 5-15 mm / min, coating time of 10-45 s, and lifting times of 1-5 times.

[0018] Invention Principle: Covalent organic framework compounds (COF-LZU) are a class of two-dimensional covalent organic crystal materials with predetermined properties, possessing a low-dimensional π-electron framework and a highly ordered topological structure. The structural units are arranged in a periodic planar network and stacked vertically to form a layered structure with consistent atomic precision. High crystallinity, ordered π-charge carrier transport capabilities, and unique stacking characteristics make them ideal for applications in the sensing field. Furthermore, COF-LZU exhibits tunable porosity and the ability to selectively carry specific guest molecules, thus serving as a powerful tool for detecting harmful volatile organic compounds (VOCs) in exhaled breath. Modular COF-LZU design allows for the matching and combination of electron-rich and electron-deficient structural modules to generate periodic lattices of covalently linked donor-acceptor pairs, effectively promoting charge transition and transport. Therefore, COF-LZU offers numerous advantages in enhancing sensing response.

[0019] To fully realize the potential of COF-LZU in gas-sensitive element design, an economical and feasible method is needed to obtain composite materials with MOS / high conductivity and high sensing sensitivity. Immobilizing COF-LZU on carbon nanotubes can improve its conductivity in sensor applications. By uniformly growing COF-LZU along the surface of rGO nanosheets, the obtained COF-LZU / rGO exhibits low density, good conductivity, good mechanical strength, and excellent adsorption and electrical properties. Although COF-LZU possesses certain crystallinity, its long-term ordered growth in micro / nano functional materials is limited due to internal defects and dynamic trapping of small particles. Therefore, combining COF-LZU with metal oxide semiconductor-carbon nanocomposites with extended properties can achieve a considerable specific surface area and a strong synergistic effect.

[0020] In this invention, the noble metal@COF-LZU@MOS quantum crystal@carbon nanotube composite film possesses a three-dimensional porous structure, thus exhibiting a large specific surface area and providing numerous active sites. This lowers the activation energy for the reaction, reducing the sensor's operating temperature requirements and consequently reducing power consumption. This enhances the response intensity and sensitivity to acetone gas, while also improving the repeatability and long-term stability of the sensing performance. The covalent organic framework compound forms a superior heterojunction with the metal oxide semiconductor quantum crystal and carbon nanotubes. The carbon nanotubes are grown in situ on the planar sensor, ensuring full contact between the metal oxide semiconductor quantum crystal and the carbon nanotubes. The interaction between the covalent organic framework compound and the carbon nanotubes forms a composite structure, effectively improving electron transport capability and gas-sensing activity. This solves the technical problems of low gas-sensing activity and unstable impedance of metal oxide semiconductor carbon nanotubes. Furthermore, the excellent conductivity of carbon nanotubes significantly increases electron transport capability, thereby achieving high sensitivity and selectivity for acetone sensing performance.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0022] (1) In this invention, a noble metal@COF-LZU@MOS quantum grains@carbon nanotube composite film is used as a sensitive layer in an acetone gas sensor, which achieves high selectivity, high repeatability and high stability for acetone gas, and has a low operating temperature and high sensitivity.

[0023] (2) The method for preparing the sensor based on the noble metal@COF-LZU@MOS quantum grains@carbon nanotube composite film of the present invention has the advantages of low cost, simple process and large-scale production. Attached Figure Description

[0024] Figure 1 This is a scanning electron microscope image of the Pt@COF-LZU@zinc oxide quantum grains@carbon nanotube composite film prepared in Example 1 of the present invention;

[0025] Figure 2 The test graph shows the response of the gas sensor prepared in Example 1 of the present invention to different concentrations of acetone gas.

[0026] Figure 3 This is a test graph showing the sensing performance of the gas sensor prepared in Example 1 of the present invention for 0.5 ppm acetone under different humidity conditions.

[0027] Figure 4 This is a test chart of the gas sensor prepared in Embodiment 1 of the present invention for the selectivity of different gases;

[0028] Figure 5 This is a test graph showing the response of the gas sensor prepared in Example 2 of the present invention to different concentrations of acetone gas. Detailed Implementation

[0029] The present invention will now be further described in conjunction with specific embodiments and accompanying drawings.

[0030] Example 1: The Pd@COF-LZU@zinc oxide quantum grains@carbon nanotube composite film of the present invention uses carbon nanotubes as a substrate, on which zinc oxide quantum grains, covalent organic framework compound COF-LZU and Pd are sequentially loaded.

[0031] The present invention relates to a sensor based on the above-mentioned Pd@COF-LZU@zinc oxide quantum grains@carbon nanotube composite film. The sensor uses the sensor device as a substrate, and a Pd@COF-LZU@zinc oxide quantum grains@carbon nanotube composite film is deposited on the surface of the substrate. It can be used to detect acetone gas. The thickness of the Pd@COF-LZU@zinc oxide quantum grains@carbon nanotube composite film is 600-700 nm.

[0032] The method for manufacturing the above-mentioned sensor includes the following steps:

[0033] (1) The basic characteristics of the sensor are: silicon substrate, silicon dioxide is deposited on the silicon substrate, then titanium layer and platinum layer are deposited, and finally platinum interdigitated electrode array is etched on the surface. Each platinum interdigitated electrode has a width of 10μm and a length of 1mm, the interdigitated electrode spacing is 8μm, and the interdigitated electrodes overlap by 800μm.

[0034] The sensor was placed in an alumina ceramic boat, which was then placed in the middle of a quartz tube in a tubular furnace. A nitrogen atmosphere of 50 mL / min was introduced into the quartz tube, and the temperature was uniformly raised to 800 °C over 30 min. A mixture of methane and nitrogen-hydrogen gas at a flow rate of 15 mL / min was then introduced, and the reaction time was 1.5 h. After the reaction was complete, the methane gas was turned off. The device was cooled to room temperature under a 100 mL / min nitrogen atmosphere and removed from the alumina ceramic boat, yielding a sensor with a carbon nanotube substrate.

[0035] (2) 1.2 g of zinc dichloride, a precursor for metal oxide semiconductors, was dissolved in 6 ml of anhydrous isopropanol, and 0.3 g of P123 was added and mixed thoroughly to obtain a precursor sol solution. Then, 0.4 ml of 12M HCl was added dropwise to the precursor solution and ultrasonically dispersed for 6 min. Under Ar atmosphere protection, the precursor solution was dip-coated onto a sensor device loaded with carbon nanotubes at a speed of 20 mm / min. The sensor device was immersed in the solution for 25 s, and this was repeated 3 times. After each dip-coating, the sensor device was dried at 60 °C for 1 h. The dried sensor device was placed in a sealed container and subjected to water vapor-assisted crystallization treatment: it was exposed to water vapor with 95% relative humidity at 150 °C for 40 h. After the reaction, glow discharge treatment was performed: the sensor device was subjected to oxygen plasma treatment (frequency 40 kHz, power 300 W) for 10 min to obtain a sensor device loaded with zinc oxide@carbon nanotube composite film.

[0036] (3) Weigh the molar ratio of pyromellitic aldehyde to p-phenylenediamine in a glove box filled with protective gas at 1:3. Then, add 10 mL of anhydrous dioxane to obtain a mixture. Under ultrasonic assistance, add 2.5 mL of 3M acetic acid aqueous solution to the mixture. After ultrasonication for 6 min, vacuum treatment is performed. Under argon protection, the above mixture is coated at a speed of 8 mm / min. The sensor obtained in step (2) is immersed in the mixture for 30 s each time, and the coating is repeated 3 times. Under argon protection, the sensor is placed in anhydrous dioxane vapor at a temperature of 130℃ and a pressure of 65 kPa for 35 h to induce self-assembly. After the reaction is completed, the sensor is taken out, cleaned with anhydrous acetone, and then immersed in anhydrous tetrahydrofuran for 24 h. Then, it is vacuum dried at 60℃ for 12 h to obtain a sensor with a covalent organic framework compound COF-LZU@zinc oxide quantum crystals@carbon nanotube composite film.

[0037] (4) Add 30 mg PdCl2 to 4 ml of anhydrous isopropanol and stir magnetically for 1 h to obtain a noble metal salt mixed solution; under argon protection, immerse the sensor obtained in step (3) in the noble metal salt mixed solution for pull coating, the immersion time is 10 s, the pull speed is 5 mm / min, and the pull is preferably 3 times. The coated device is vacuum dried at 50 °C for 12 h; under argon protection, the sensor is exposed to isopropanol vapor at 110 °C and 90 kPa for 24 h; the vapor-treated sensor is rinsed with acetone and then dried under vacuum for 12 h; the sensor is treated with argon plasma (frequency 40 kHz, power 300 W) for 10 min to obtain a gas sensor based on Pd@COF-LZU@zinc oxide quantum grains@carbon nanotube composite film.

[0038] XPS surface elemental analysis revealed that the proportions of carbon nanotubes, zinc oxide, covalent organic framework compounds, and Pd in ​​the Pd@COF-LZU@zinc oxide quantum crystals@carbon nanotube composite film were 38%, 37%, 20%, and 5%, respectively.

[0039] like Figure 1 The average diameter of the carbon nanotubes used to construct the composite film is 40-50 nm, the average wall thickness of the carbon nanotubes is 10-20 nm, the average particle size of the zinc oxide quantum grains is 3-5 nm, and the average thickness of the COF-LZU film layer is 5-17 nm.

[0040] Performance testing was conducted on the gas sensor with a surface-loaded composite thin film: First, the gas sensor was operated at a certain voltage. After the initial baseline stabilized, acetone gas of a corresponding concentration was introduced. Once the resistance of the gas sensor decreased and reached equilibrium, air was introduced into the test chamber until the baseline stabilized again. The corresponding gas-sensing test data was collected by a computer, and the gas-sensing test was completed. The real-time response curves of the sensor to acetone concentrations of 0.2-25 ppm at room temperature are shown below. Figure 2 As shown. From Figure 2 As can be seen, the sensor exhibits a rapid increase in size with increasing gas concentration; when the acetone gas concentration is 0.2-25 ppm, the sensor's output characteristic curve for acetone shows good correlation characteristics.

[0041] The gas sensor with surface-loaded composite thin film was tested for performance under different humidity conditions: First, the gas sensor was operated at room temperature. After the initial baseline stabilized, acetone gas at concentrations of 0.5 ppm was introduced under different humidity conditions, such as 50%, 70%, and 90%. Once the resistance of the gas sensor decreased and reached equilibrium, air was introduced into the test chamber until the baseline stabilized again, completing the gas sensor test. Figure 3 It can be seen that the sensitivity of the gas sensor remains basically constant after the humidity exceeds 70%. Even at 90% humidity, the sensitivity remains high, with a sensitivity of 29.5 for 0.5 ppm acetone gas, enabling rapid detection of acetone. The sensor's response time is within 5 seconds, and its recovery time is within 2 seconds. Gas selectivity tests were performed on the gas sensor with surface-loaded composite thin film, such as... Figure 4 As shown, the gas sensor's sensitivity to acetone is much higher than that to toluene, isopropanol, diethyl ether, formaldehyde, dimethylacetamide, and ethanol, and is more than four times more sensitive to other target gases, indicating that the gas sensor has excellent selectivity for acetone gas.

[0042] Example 2: The Pt@COF-LZU@iron oxide quantum grains@carbon nanotube composite film of the present invention uses carbon nanotubes as a substrate, on which iron oxide quantum grains, covalent organic framework compound COF-LZU and Pt are sequentially loaded.

[0043] The present invention relates to a sensor based on the above-mentioned Pt@COF-LZU@iron oxide quantum grains@carbon nanotube composite film. The sensor uses the sensor device as a substrate, and a Pt@COF-LZU@iron oxide quantum grains@carbon nanotube composite film is deposited on the surface of the substrate. It can be used to detect acetone gas. The thickness of the Pt@COF-LZU@iron oxide quantum grains@carbon nanotube composite film is 600-700 nm.

[0044] The method for fabricating a sensor based on a Pt@COF-LZU@iron oxide quantum grains@carbon nanotube composite film of the present invention includes the following steps:

[0045] (1) The basic characteristics of the sensor are: silicon substrate, silicon dioxide is deposited on the silicon substrate, then titanium layer and platinum layer are deposited, and finally platinum interdigitated electrode array is etched on the surface. Each platinum interdigitated electrode has a width of 10μm and a length of 1mm, the interdigitated electrode spacing is 8μm, and the interdigitated electrodes overlap by 800μm.

[0046] The sensor was placed in an alumina ceramic boat, which was then placed in the middle of a quartz tube in a tubular furnace. An N2 atmosphere was introduced into the quartz tube at a flow rate of 80 mL / min, and the temperature was uniformly increased to 900 °C over 60 min. A mixture of methane and nitrogen-hydrogen gas was then introduced at a flow rate of 15 mL / min for 2.5 h. After the reaction was complete, the methane gas was turned off. The device was cooled to room temperature under a 100 mL / min N2 atmosphere and removed from the alumina ceramic boat, yielding a sensor with a carbon nanotube substrate.

[0047] (2) 2.0 g of ferric chloride, a metal oxide semiconductor precursor, was dissolved in 10 ml of anhydrous isopropanol, and 0.5 g of P123 was added and mixed thoroughly to obtain a precursor sol solution. Then, 0.6 ml of 12M HCl was added dropwise to the precursor solution and ultrasonically dispersed for 8 min. Under Ar atmosphere protection, the precursor solution was dip-coated onto a sensor device loaded with carbon nanotubes at a speed of 15 mm / min. The sensor device was immersed in the solution for 30 s, and this was repeated 4 times. After each dip-coating, the sensor device was dried at 50 °C for 1 h. The dried sensor device was placed in a sealed container and subjected to water vapor-assisted crystallization treatment: it was exposed to water vapor with 90% relative humidity at 140 °C for 50 h. After the reaction, glow discharge treatment was performed: the sensor device was subjected to oxygen plasma treatment (frequency 40 kHz, power 300 W) for 12 min to obtain a sensor device with an iron oxide semiconductor@carbon nanotube composite film.

[0048] (3) Weigh the molar ratio of pyromellitic aldehyde to p-phenylenediamine in a glove box filled with protective gas at 1:3. Then, add 12 ml of anhydrous dioxane to obtain a mixture. Under ultrasonic assistance, add 3.5 ml of 3M acetic acid aqueous solution to the mixture. After ultrasonication for 8 min, vacuum treatment is performed. Under argon protection, the above mixture is coated at a speed of 10 mm / min. The sensor obtained in step (2) is immersed in the mixture for 25 s each time, and the coating is repeated 4 times. Under argon protection, the sensor is placed in anhydrous dioxane vapor at a temperature of 120℃ and a pressure of 70 kPa for 30 h to induce self-assembly. After the reaction is completed, the sensor is taken out, cleaned with anhydrous acetone, and then immersed in anhydrous tetrahydrofuran for 18 h. Then, it is vacuum dried at 60℃ for 14 h to obtain a sensor with a covalent organic framework compound COF-LZU@iron oxide quantum crystals@carbon nanotube composite film.

[0049] (4) Add 40 mg PtCl4 to 6 ml of anhydrous isopropanol and stir magnetically for 1 h to obtain a noble metal salt mixed solution; under argon protection, immerse the sensor obtained in step (3) in the noble metal salt mixed solution for pull coating, the immersion time is 25 s, the pull speed is 10 mm / min, and the pull-up times are preferably 5 times. The coated device is vacuum dried at 50 °C for 12 h; under argon protection, the sensor is exposed to isopropanol vapor at 100 °C and 100 kPa for 20 h; the vapor-treated sensor is rinsed with acetone and then dried under vacuum for 12 h; the sensor is treated with argon plasma (frequency 40 kHz, power 300 W) for 15 min to obtain a sensor based on Pt@COF-LZU@iron oxide quantum grains@carbon nanotube composite film.

[0050] XPS surface elemental analysis revealed that the molar percentages of carbon nanotubes, iron oxide quantum grains, covalent organic framework compound COF-LZU, and Pt in the composite film were 32%, 29%, 30%, and 9%, respectively.

[0051] The real-time response curves of the composite thin-film gas sensor to acetone concentrations of 0.2-25 ppm at room temperature are shown in the figure below. Figure 5 As shown, from Figure 5 As can be seen, when the acetone gas concentration is 0.2-25 ppm, the sensor exhibits excellent correlation characteristics with the acetone output curve.

Claims

1. A sensor of a noble metal@COF-LZU@MOS quantum grain@carbon nanotube composite thin film, characterized in that, The composite film uses carbon nanotubes as a substrate, on which metal oxide semiconductor quantum grains, a covalent organic framework compound COF-LZU, and a noble metal are sequentially loaded. The sensor uses a sensor device as a substrate, on which a noble metal@COF-LZU@MOS quantum grains@carbon nanotube composite film is deposited. The method for fabricating the sensor based on the noble metal@COF-LZU@MOS quantum grains@carbon nanotube composite film includes the following steps: (1) A carbon nanotube substrate is prepared on the surface of the sensor device to obtain a sensor device loaded with a carbon nanotube substrate; (2) The sensor device loaded with carbon nanotube substrate is immersed in metal oxide semiconductor precursor solution for dip coating, taken out and dried, and then placed in a sealed container for water vapor-assisted crystallization treatment. After treatment, glow discharge treatment is performed to obtain the sensor device loaded with metal oxide semiconductor@carbon nanotube composite film. (3) The sensor device loaded with metal oxide semiconductor@carbon nanotube composite film is immersed in the precursor solution of covalent organic framework compound COF-LZU for dip coating, taken out and vacuum dried, and then subjected to organic solvent vapor-assisted crystallization treatment, cleaned and dried to obtain the sensor device loaded with covalent organic framework compound COF-LZU@MOS quantum grains@carbon nanotube composite film. (4) In a protective gas, the sensor device loaded with the covalent organic framework compound COF-LZU@MOS quantum grains@carbon nanotube composite film is immersed in a mixed solution of noble metal salts for dip coating, dried, placed in an argon protective atmosphere, and subjected to thermal evaporation in organic solvent vapor. After cleaning and drying, it is then subjected to glow discharge treatment to obtain the sensor based on the noble metal@COF-LZU@MOS quantum grains@carbon nanotube composite film.

2. The sensor according to claim 1, characterized in that, The composite film contains carbon nanotubes, metal oxide semiconductor quantum grains, covalent organic framework compound COF-LZU, and noble metals in a molar ratio of 32-38%:29-37%:20-30%:5-9%. The carbon nanotubes have an average diameter of 40-50 nm and an average wall thickness of 10-20 nm. The metal oxide semiconductor quantum grains have an average particle size of 3-5 nm, and the film layer formed by the covalent organic framework compound COF-LZU has an average thickness of 5-17 nm.

3. The sensor according to claim 1, characterized in that, The sensor is used to detect acetone gas, and the average thickness of the noble metal@COF-LZU@MOS quantum grains@carbon nanotube composite film is 600-700 nm.

4. The sensor according to claim 1, characterized in that, In step (1), the step of preparing a carbon nanotube substrate on the surface of the sensor device is as follows: the sensor device is placed in an alumina ceramic boat and placed together in the middle of the quartz tube of a tubular electric furnace. N2 is introduced into the quartz tube, the temperature is raised to the reaction temperature, and then carbon-containing gas methane is introduced to provide an additional carbon source and a nitrogen-hydrogen mixture for deposition reaction. The carbon-containing gas decomposes to generate carbon nanotubes which are deposited on the surface of the sensor device, thus obtaining a sensor device loaded with a carbon nanotube substrate. The reaction temperature is 750-950 ℃, the flow rate of the carbon-containing gas is 15-35 ml / min, and the deposition reaction time is 1-3 h.

5. The sensor according to claim 1, characterized in that, In step (2), the preparation method of the metal oxide semiconductor precursor solution is as follows: dissolve the metal oxide semiconductor precursor in an organic solvent, add a surfactant and mix evenly to obtain a precursor sol solution. Then, add hydrochloric acid dropwise into the precursor solution and disperse it by ultrasonication to obtain the metal oxide semiconductor precursor solution. The metal oxide semiconductor precursor is zinc dichloride, ferric chloride, titanium tetrachloride or tin tetrachloride, the organic solvent is anhydrous isopropanol, anhydrous butanol or anhydrous ethanol, the mass ratio of the metal oxide semiconductor precursor to the volume of the organic solvent is 1.2-2.4 g: 6-12 ml, and the surfactant is P123, F127 or Brij35. The water vapor crystallization treatment is as follows: the temperature of the sealed container is controlled at 100-180 ℃, the relative humidity inside the sealed container is 75-95%, and the reaction time is 40-50 h. The glow discharge treatment is as follows: oxygen glow discharge treatment is performed with a power of 100-300 W and a time of 10-12 min.

6. The sensor according to claim 1, characterized in that, In step (3), the preparation method of the COF-LZU precursor solution of the covalent organic framework compound is as follows: in a protective gas, pyromellitic aldehyde and p-phenylenediamine are dissolved in anhydrous dioxane to obtain a mixed solution; under ultrasonic assistance, an aqueous acetic acid solution is added to the mixed solution, ultrasonically treated, and then vacuumed to obtain the solution; the molar ratio of pyromellitic aldehyde and p-phenylenediamine is 1:1-3; the organic solvent vapor-assisted crystallization treatment method is as follows: exposed to an organic solvent anhydrous dioxane at a temperature of 120-150 ℃, a pressure of 50-100 kPa, and a protective atmosphere for 20-60 h.

7. The sensor according to claim 1, characterized in that, In step (4), the method for preparing the noble metal mixed solution is as follows: 30-50 mg of noble metal salt is added to 3-6 ml of organic solvent, and after stirring, a homogeneous mixture is formed to obtain the noble metal mixed solution; the noble metal salt is PdCl2 or PtCl4, and the organic solvent is isopropanol; the thermal evaporation treatment of the organic solvent vapor is as follows: under argon protection, it is exposed to isopropanol vapor at a temperature of 100-135 ℃ and a pressure of 50-100 kPa for 18-54 h; the glow discharge treatment is as follows: argon plasma cleaning is performed with a power of 100-300 W and a plasma cleaning time of 5-20 min.

8. The sensor according to claim 1, characterized in that, In steps (2) to (4), the parameters for the lifting coating are: lifting speed of 5-15 mm / min, coating time of 10-45 s, and lifting times of 1-5 times.

Images