A thin film nitric oxide sensor and a method of making the same

Abstract

The application discloses a kind of thin film nitric oxide sensor and preparation method, preparation method includes: water-soluble zinc salt is mixed with water and is obtained A solution;2-methylimidazole, CTAB and water are mixed and obtained B solution;A solution and B solution are mixed and obtained reaction liquid, MOFs material is obtained by hydrothermal reaction;In reaction liquid, the mass fraction of CTAB is 0.01-0.1%;MOFs material is calcined and obtained zinc oxide nanomaterial, is dissolved in terpineol, after stirring, obtained slurry, add to silicon piece, then carry out glue, after glue, dry, anneal and obtain annealing device;Annealing device is welded, packaged and obtained the thin film nitric oxide sensor in the present application Surfactant (CTAB) is used to control the shape and size of MOFs particle, so that gas sensor has high sensitivity and selectivity;Meanwhile, the working temperature of the gas sensitive material is low, and the energy consumption is also low, which can be used for nitric oxide gas detection.

Description

Technical Field

[0001] This invention relates to the field of gas sensor technology, specifically to a thin-film nitric oxide sensor and its preparation method. Background Technology

[0002] Nitrogen oxides (NOx) detection has wide applications in environmental monitoring, exhaust emission monitoring, and medicine. NOx is one of the waste gases produced by industrial production. x NOx primarily originates from the combustion of fossil fuels such as gasoline and coal, with vehicle exhaust and power plant emissions being the two main sources. The combustion process produces NOx. x Nitrogen oxides are primarily nitric oxide (NO), accounting for approximately 90%, while nitrogen dioxide (NO2) constitutes only a small portion. Excessive nitrogen oxides in the air have a significant impact on human life and the environment. For example, they can cause respiratory diseases such as emphysema and bronchitis, and also damage the ozone layer, leading to environmental disasters. Therefore, the accuracy of nitrogen oxide emission detection is crucial in further implementing nitrogen oxide emission reduction measures. In addition, the monitoring of inhaled nitric oxide (INO) is widely used in the treatment of adult heart valve surgery. INO delivery and monitoring systems need to precisely control NO concentrations below 40 ppm; the accuracy of nitrogen oxide detection cannot be ignored.

[0003] Current methods for NO detection typically include electron spin resonance spectroscopy, chemiluminescence immunoassay, fluorescence spectrophotometry, and semiconductor gas sensor detection. Electron spin resonance spectroscopy is convenient and rapid, but suffers from low sensitivity, a narrow linear range, and requires expensive equipment and advanced technology, making it unsuitable for widespread application. Chemiluminescence immunoassay offers high sensitivity and specificity, but requires specific conditions such as specialized equipment, large sample volumes, acidification, and heating; temperature and gas flow rate significantly affect the instrument. Fluorescence spectrophotometry offers high sensitivity and specificity, but fluorescent probe preparation is complex and time-consuming, and it exhibits poor selectivity under acidic conditions, while detection under alkaline conditions limits its application in biological samples. In recent years, semiconductor gas sensors have been applied to NO detection due to their high sensitivity and small size. Currently, most NO sensors operate at temperatures exceeding 200°C, which leads to high energy consumption and potential safety hazards. Furthermore, NO is a corrosive gas, and sensors operating in an NO atmosphere for extended periods may deactivate. Therefore, there is a need to develop NO gas sensors with high sensitivity, fast response, low detection limit (ppb), low energy consumption, and high corrosion resistance.

[0004] In recent years, metal-organic frameworks (MOFs) have emerged as a promising new type of inorganic-organic hybrid material due to their diverse types, high porosity, ultra-high specific surface area, and easily tunable pore size. However, the relatively poor stability of MOFs significantly limits their practical applications and development. Conversely, their thermal instability and easy decomposition can be utilized in reverse, turning waste into treasure. Using MOFs as sacrificial templates and high-temperature annealing can produce stable and reliable nanoporous structures that exhibit excellent performance in gas adsorption, heterogeneous catalysis, and drug delivery.

[0005] Currently, there are few research reports on semiconductor nitric oxide sensor sensitive materials and the use of MOFs as sacrificial templates to prepare sensor sensitive materials. Most related reports focus on the direct preparation of sensitive materials using MOFs, which presents several problems. Chinese patent application CN111392719A discloses a silicon-doped graphene and its preparation method, as well as a silicon-doped graphene-based chemielectric resistive nitrogen oxide room-temperature sensor. This patent mainly involves placing graphene oxide powder and a silane coupling agent reactant into a sealed container filled with inert gas to maintain a certain pressure, followed by heat treatment to generate a silicon-doped graphene-based sensor. The prepared high-quality fractionally bonded graphene exhibits significant sensing performance for nitrogen oxide gas molecules, with low detection limits and high selectivity. However, the preparation conditions are demanding, making industrialization challenging. Chinese patent application CN114544714A discloses a MOF / conductive polymer composite thin film gas sensor suitable for chemical resistance sensors, which is prepared by blending CoCe-BTC and PEDOT. The prepared composite sensing material has good gas sensitivity, conductivity and cycle stability. However, it directly responds to the MOFs coated gas sensing material, and its long-term stability is difficult to maintain due to the easy decomposition of MOFs themselves. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a nitric oxide sensor with high sensitivity, selectivity, low power consumption and high corrosion resistance.

[0007] The present invention solves the above-mentioned technical problems through the following technical means:

[0008] A method for fabricating a thin-film nitric oxide sensor includes the following steps:

[0009] S1. A solution A is obtained by uniformly mixing water-soluble zinc salt with water; B solution B is obtained by uniformly mixing 2-methylimidazole, CTAB and water; C reaction solution is obtained by uniformly mixing solution A and solution B; Dry the reaction solution under hydrothermal reaction, and then dry the solid after cooling to obtain MOF material; wherein, the mass fraction of CTAB in the reaction solution is 0.01-0.1 wt%.

[0010] S2. Calcination of MOF materials yields zinc oxide nanomaterials;

[0011] S3. Mix zinc oxide nanomaterials with terpineol and stir to obtain a slurry;

[0012] S4. Add the slurry to the silicon wafer, then perform homogenization. After homogenization, dry and anneal to obtain the annealed device.

[0013] S5. The annealed components are welded and packaged to obtain the thin-film nitric oxide sensor.

[0014] Preferably, in S1, the water-soluble zinc salt is one or a mixture of zinc acetate, zinc nitrate, zinc chloride, zinc sulfate, and zinc gluconate; and in the reaction solution, the mass-volume ratio of zinc content, 2-methylimidazole, CTAB, and water in the water-soluble zinc salt is 0.131g:1.31g:0.003-0.0317g:30ml.

[0015] Preferably, the zinc acetate is zinc acetate dihydrate; the zinc nitrate is zinc nitrate hexahydrate; and the zinc sulfate is zinc sulfate heptahydrate.

[0016] Preferably, in S1, solution A and solution B are mixed and stirred evenly at a speed of 200-400 rpm to obtain a reaction solution.

[0017] Preferably, in S1, the hydrothermal reaction is carried out at a temperature of 135-175°C for a time of 0.5-2 hours.

[0018] Preferably, in S1, the hydrothermal reaction is carried out at a temperature of 150°C for 1 hour.

[0019] Preferably, in S2, the calcination includes heating to 400°C at a heating rate of 0.5-2°C / min, and then holding at that temperature for 2 hours.

[0020] Preferably, in S2, the calcination includes heating to 400°C at a heating rate of 1°C / min, and then holding at that temperature for 2 hours.

[0021] Preferably, in S3, the mass ratio of the zinc oxide nanomaterial to terpineol is 30:70-60:40.

[0022] Preferably, in S3, the stirring speed is 5000-10000 rpm and the time is 0.5-2h.

[0023] Preferably, in step S4, the spin coating includes a first spin coating and a second spin coating; the first spin coating has a rotation speed of 500 r / min and a time of 8 s, and the second spin coating has a rotation speed of 2500 r / min and a time of 60 s.

[0024] Preferably, in step S4, the drying temperature is 50-80°C and the time is 2-4 hours; the annealing temperature is 400°C and the time is 2 hours.

[0025] Preferably, in step S4, the drying temperature is 65°C and the time is 2 hours.

[0026] Preferably, in S5, the welding is performed using a gold wire ball bonding machine; the encapsulation is a ceramic encapsulation.

[0027] The present invention also proposes a thin-film nitric oxide sensor, which is prepared by the aforementioned method for preparing a thin-film nitric oxide sensor.

[0028] The advantages of this invention are as follows: This invention proposes a thin-film nitric oxide sensor and its preparation method. It mainly involves controlling the growth of MOFs (Metal-Oxide-Foil) shape and size using a specific surfactant CTAB, generating metal oxide materials through thermal decomposition using MOFs as sacrificial templates, and then constructing the thin-film gas-sensitive material using a spin coater. The prepared nitric oxide sensor exhibits both high sensitivity and selectivity. Furthermore, the gas-sensitive material operates at a low temperature (low power consumption) and has high corrosion resistance, making it a highly applicable method for preparing nitric oxide sensors. Attached Figure Description

[0029] Figure 1 This is a SEM image of the MOFs material in Example 1 of the present invention;

[0030] Figure 2 This is a SEM image of the MOFs material in Comparative Example 1 of this invention;

[0031] Figure 3 This is a SEM image of the MOFs material in Comparative Example 2 of this invention;

[0032] Figure 4 The graph shows the sensitivity characteristics of the sensor in Embodiment 1 of the present invention for testing nitric oxide and interfering gases (operating power 0.01W).

[0033] Figure 5 The response recovery curve of the nitric oxide sensor prepared in Example 1 of the present invention to 1 ppm nitric oxide (operating power 0.01W);

[0034] Figure 6 The image shows the response recovery curve of the nitric oxide sensor prepared in Example 1 of this invention to 50 ppm nitric oxide (operating power 0.01 W). Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0037] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0038] Example 1

[0039] A method for fabricating a thin-film nitric oxide sensor, comprising the following specific steps:

[0040] (1) Preparation of MOF materials

[0041] ① Weigh 0.439g of zinc acetate dihydrate into a beaker, add 10ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution A;

[0042] ② Weigh 1.31g of 2-methylimidazole and 0.0060g of CTAB into a beaker, add 20ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution B;

[0043] ③ Pour solution A into solution B and stir at 200 rpm for 5 minutes;

[0044] ④ Pour the mixed solution into a hydrothermal reactor, place it in an oven, react at 150°C for 1 hour, then remove and cool to room temperature;

[0045] ⑤ Centrifuge to obtain a solid, place it in an oven and dry at 60℃ for 12 hours to obtain MOFs material;

[0046] (2) Preparation of zinc oxide

[0047] Metal oxides were prepared using MOFs as sacrificial templates by placing the MOFs in a muffle furnace and heating it to 400°C at a heating rate of 1°C / min, then holding it at that temperature for 2 hours, and finally allowing it to cool naturally to room temperature to obtain zinc oxide nanomaterials.

[0048] (3) Homogenization of sensitive materials

[0049] ① Weigh the zinc oxide nanomaterials prepared above and dissolve them in terpineol, wherein the mass ratio of zinc oxide nanomaterials to terpineol is 40:60. Disperse the mixture in a high-speed disperser at a speed of 6000 rpm for 2 hours to obtain a sensitive material slurry with good extensibility and flowability.

[0050] ② Place the 6-inch silicon wafer with the printed circuit electrodes onto the spin coater, set the spin coater speed and time. The spin coater program for this sensitive material is set to two segments: the first segment is 500 rpm for 8 seconds, and the second segment is 2500 rpm for 60 seconds. Take 75g of the above sensitive material paste and drop it onto the silicon wafer. Turn on the spin coater and run the set spin coater program. After the spin coater is finished, put the silicon wafer into the oven and dry it at 65°C for 2 hours. After removing the sensitive material adhering to the electrodes with a pin, put it into a muffle furnace and anneal at 400°C for 2 hours.

[0051] (4) Sample cutting, component soldering and packaging

[0052] The annealed sample was cut, the prepared device was soldered using a gold wire bonding machine, and then ceramic encapsulated to obtain the thin-film nitric oxide sensor.

[0053] Example 2

[0054] A method for fabricating a thin-film nitric oxide sensor, comprising the following specific steps:

[0055] (1) Preparation of MOF materials

[0056] ① Weigh 0.439g of zinc acetate dihydrate into a beaker, add 10ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution A;

[0057] ② Weigh 1.31g of 2-methylimidazole and 0.0159g of CTAB into a beaker, add 20ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution B;

[0058] ③ Pour solution A into solution B and stir at 400 rpm for 5 minutes;

[0059] ④ Pour the mixed solution into a hydrothermal reactor, place it in an oven at 135°C for 2 hours, and then remove it and cool it to room temperature;

[0060] ⑤ Centrifuge to obtain a solid, place it in an oven and dry at 60℃ for 12 hours to obtain MOFs material;

[0061] (2) Preparation of zinc oxide

[0062] Metal oxides were prepared using MOFs as sacrificial templates by placing the MOFs in a muffle furnace and heating it to 400°C at a heating rate of 1°C / min, then holding it at that temperature for 2 hours, and finally allowing it to cool naturally to room temperature to obtain zinc oxide nanomaterials.

[0063] (3) Homogenization of sensitive materials

[0064] ① Weigh the zinc oxide nanomaterials prepared above and dissolve them in terpineol, wherein the mass ratio of zinc oxide nanomaterials to terpineol is 50:50. Disperse the slurry of the sensitive material in a high-speed disperser at a speed of 7500 rpm for 1 hour to obtain a slurry of the sensitive material with good extensibility and flowability.

[0065] ② Place the 6-inch silicon wafer with the printed circuit electrodes onto the spin coater, set the spin coater speed and time. The spin coater program for this sensitive material is set to two segments: the first segment is 500 rpm for 8 seconds, and the second segment is 2500 rpm for 60 seconds. Take 60g of the above sensitive material paste and drop it onto the silicon wafer. Turn on the spin coater and run the set spin coater program. After the spin coater is finished, put the silicon wafer into the oven and dry it at 50°C for 4 hours. After removing the sensitive material adhering to the electrodes with a pin, put it into a muffle furnace and anneal at 400°C for 2 hours.

[0066] (4) Sample cutting, component soldering and packaging

[0067] The annealed sample was cut, the prepared device was soldered using a gold wire bonding machine, and then ceramic encapsulated to obtain the thin-film nitric oxide sensor.

[0068] Example 3

[0069] A method for fabricating a thin-film nitric oxide sensor, comprising the following specific steps:

[0070] (1) Preparation of MOF materials

[0071] ① Weigh 0.439g of zinc acetate dihydrate into a beaker, add 10ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution A;

[0072] ② Weigh 1.31g of 2-methylimidazole and 0.0317g of CTAB into a beaker, add 20ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution B;

[0073] ③ Pour solution A into solution B and stir at 300 rpm for 5 minutes;

[0074] ④ Pour the mixed solution into a hydrothermal reactor, place it in an oven at 175℃ for 0.5 hours, and then remove it and cool it to room temperature;

[0075] ⑤ Centrifuge to obtain a solid, place it in an oven and dry at 60℃ for 12 hours to obtain MOFs material;

[0076] (2) Preparation of zinc oxide

[0077] Metal oxides were prepared using MOFs as sacrificial templates by placing the MOFs in a muffle furnace and heating it to 400°C at a heating rate of 0.5°C / min, then holding it at that temperature for 2 hours, and finally allowing it to cool naturally to room temperature to obtain zinc oxide nanomaterials.

[0078] (3) Homogenization of sensitive materials

[0079] ① Weigh the zinc oxide nanomaterials prepared above and dissolve them in terpineol, wherein the mass ratio of zinc oxide nanomaterials to terpineol is 30:70. Disperse the slurry of the sensitive material in a high-speed disperser at a speed of 10,000 rpm for 0.5 h to obtain a slurry of sensitive material with good extensibility and flowability.

[0080] ② Place the 6-inch silicon wafer with the printed circuit electrodes onto the spin coater, set the spin coater speed and time. The spin coater program for this sensitive material is set to two segments: the first segment is 500 rpm for 8 seconds, and the second segment is 2500 rpm for 60 seconds. Take 100g of the above sensitive material paste and drop it onto the silicon wafer. Turn on the spin coater and run the set spin coater program. After the spin coater is finished, put the silicon wafer into the oven and dry it at 65°C for 3 hours. After removing the sensitive material adhering to the electrodes with a pin, put it into a muffle furnace and anneal at 400°C for 2 hours.

[0081] (4) Sample cutting, component soldering and packaging

[0082] The annealed sample was cut, the prepared device was soldered using a gold wire bonding machine, and then ceramic encapsulated to obtain the thin-film nitric oxide sensor.

[0083] Example 4

[0084] A method for fabricating a thin-film nitric oxide sensor, comprising the following specific steps:

[0085] (1) Preparation of MOF materials

[0086] ① Weigh 0.595g of zinc nitrate hexahydrate into a beaker, add 10ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution A;

[0087] ② Weigh 1.31g of 2-methylimidazole and 0.0035g of CTAB into a beaker, add 20ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution B;

[0088] ③ Pour solution A into solution B and stir at 300 rpm for 5 minutes;

[0089] ④ Pour the mixed solution into a hydrothermal reactor, place it in an oven, react at 150°C for 1 hour, then remove and cool to room temperature;

[0090] ⑤ Centrifuge to obtain a solid, place it in an oven and dry at 60℃ for 12 hours to obtain MOFs material;

[0091] (2) Preparation of zinc oxide

[0092] Metal oxides were prepared using MOFs as sacrificial templates by placing the MOFs in a muffle furnace and heating it to 400°C at a heating rate of 2°C / min, then holding it at that temperature for 2 hours, and finally allowing it to cool naturally to room temperature to obtain zinc oxide nanomaterials.

[0093] (3) Homogenization of sensitive materials

[0094] ① Weigh the zinc oxide nanomaterials prepared above and dissolve them in terpineol, wherein the mass ratio of zinc oxide nanomaterials to terpineol is 60:40. Disperse the mixture in a high-speed disperser at a speed of 5000 rpm for 2 hours to obtain a sensitive material slurry with good extensibility and flowability.

[0095] ② Place the 6-inch silicon wafer with the printed circuit electrodes onto the spin coater, set the spin coater speed and time. The spin coater program for this sensitive material is set to two segments: the first segment is 500 rpm for 8 seconds, and the second segment is 2500 rpm for 60 seconds. Take 75g of the above sensitive material paste and drop it onto the silicon wafer. Turn on the spin coater and run the set spin coater program. After the spin coater is finished, put the silicon wafer into the oven and dry it at 80°C for 2 hours. After removing the sensitive material adhering to the electrodes with a pin, put it into a muffle furnace and anneal at 400°C for 2 hours.

[0096] (4) Sample cutting, component soldering and packaging

[0097] The annealed sample was cut, the prepared device was soldered using a gold wire bonding machine, and then ceramic encapsulated to obtain the thin-film nitric oxide sensor.

[0098] Example 5

[0099] A method for fabricating a thin-film nitric oxide sensor, comprising the following specific steps:

[0100] (1) Preparation of MOF materials

[0101] ① Weigh 0.911g of zinc gluconate into a beaker, add 10ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution A;

[0102] ② Weigh 1.31g of 2-methylimidazole and 0.0060g of CTAB into a beaker, add 20ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution B;

[0103] ③ Pour solution A into solution B and stir at 200 rpm for 5 minutes;

[0104] ④ Pour the mixed solution into a hydrothermal reactor, place it in an oven, react at 150°C for 1 hour, then remove and cool to room temperature;

[0105] ⑤ Centrifuge to obtain a solid, place it in an oven and dry at 60℃ for 12 hours to obtain MOFs material;

[0106] (2) Preparation of zinc oxide

[0107] Metal oxides were prepared using MOFs as sacrificial templates by placing the MOFs in a muffle furnace and heating it to 400°C at a heating rate of 1°C / min, then holding it at that temperature for 2 hours, and finally allowing it to cool naturally to room temperature to obtain zinc oxide nanomaterials.

[0108] (3) Homogenization of sensitive materials

[0109] ① Weigh the zinc oxide nanomaterials prepared above and dissolve them in terpineol, wherein the mass ratio of zinc oxide nanomaterials to terpineol is 40:60. Disperse the slurry of the sensitive material in a high-speed disperser at a speed of 8000 rpm for 1.5 h to obtain a slurry of sensitive material with good extensibility and flowability.

[0110] ② Place the 6-inch silicon wafer with the printed circuit electrodes onto the spin coater, set the spin coater speed and time. The spin coater program for this sensitive material is set to two segments: the first segment is 500 rpm for 8 seconds, and the second segment is 2500 rpm for 60 seconds. Take 75g of the above sensitive material paste and drop it onto the silicon wafer. Turn on the spin coater and run the set spin coater program. After the spin coater is finished, put the silicon wafer into the oven and dry it at 65°C for 2 hours. After removing the sensitive material adhering to the electrodes with a pin, put it into a muffle furnace and anneal at 400°C for 2 hours.

[0111] (4) Sample cutting, component soldering and packaging

[0112] The annealed sample was cut, the prepared device was soldered using a gold wire bonding machine, and then ceramic encapsulated to obtain the thin-film nitric oxide sensor.

[0113] Comparative Example 1

[0114] A method for preparing a nitric oxide sensor, which differs from Example 1 in that no surfactant is added during the preparation of the MOFs material to control the growth of the MOFs, and the specific steps include:

[0115] (1) Preparation of MOF materials

[0116] ① Weigh 0.439g of zinc acetate dihydrate into a beaker, add 10ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution A;

[0117] ② Weigh 1.31g of 2-methylimidazole into a beaker, add 20ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution B;

[0118] ③ Pour solution A into solution B and stir at 200 rpm for 5 minutes;

[0119] ④ Pour the mixed solution into a hydrothermal reactor, place it in an oven at 150°C for 1 hour, and then remove it and cool it to room temperature;

[0120] ⑤ Centrifuge to obtain a solid, place it in an oven and dry at 60℃ for 12 hours to obtain MOFs material;

[0121] (2) Preparation of zinc oxide

[0122] Metal oxides were prepared using MOFs as sacrificial templates by placing the MOFs in a muffle furnace and heating it to 400°C at a heating rate of 1°C / min, then holding it at that temperature for 2 hours, and finally allowing it to cool naturally to room temperature to obtain zinc oxide nanomaterials.

[0123] (3) Homogenization of sensitive materials

[0124] ① Weigh the zinc oxide nanomaterials prepared above and dissolve them in terpineol, wherein the mass ratio of zinc oxide nanomaterials to terpineol is 40:60. Disperse the mixture in a high-speed disperser at a speed of 6000 rpm for 2 hours to obtain a sensitive material slurry with good extensibility and flowability.

[0125] ② Place the 6-inch silicon wafer with the printed circuit electrodes onto the spin coater, set the spin coater speed and time. The spin coater program for this sensitive material is set to two segments: the first segment is 500 rpm for 8 seconds, and the second segment is 2500 rpm for 60 seconds. Take 75g of the above sensitive material paste and drop it onto the silicon wafer. Turn on the spin coater and run the set spin coater program. After the spin coater is finished, put the silicon wafer into the oven and dry it at 65°C for 2 hours. After removing the sensitive material adhering to the electrodes with a pin, put it into a muffle furnace and anneal at 400°C for 2 hours.

[0126] (4) Sample cutting, component soldering and packaging

[0127] The annealed sample was cut, the prepared device was soldered using a gold wire bonding machine, and then ceramic encapsulated to obtain the nitric oxide sensor.

[0128] Comparative Example 2

[0129] A method for preparing a nitric oxide sensor, which differs from Example 1 in that an excess of surfactant is added during the preparation of the MOFs material, and the specific steps include:

[0130] (1) Preparation of MOF materials

[0131] ① Weigh 0.439g of zinc acetate dihydrate into a beaker, add 10ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution A;

[0132] ② Weigh 1.31g of 2-methylimidazole and 0.0634g of CTAB into a beaker, add 20ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution B;

[0133] ③ Pour solution A into solution B and stir at 200 rpm for 5 minutes;

[0134] ④ Pour the mixed solution into a hydrothermal reactor, place it in an oven at 150°C for 1 hour, and then remove it and cool it to room temperature;

[0135] ⑤ Centrifuge to obtain a solid, place it in an oven and dry at 60℃ for 12 hours to obtain MOFs material;

[0136] (2) Preparation of zinc oxide

[0137] Metal oxides were prepared using MOFs as sacrificial templates by placing the MOFs in a muffle furnace and heating it to 400°C at a heating rate of 1°C / min, then holding it at that temperature for 2 hours, and finally allowing it to cool naturally to room temperature to obtain zinc oxide nanomaterials.

[0138] (3) Homogenization of sensitive materials

[0139] ① Weigh the zinc oxide nanomaterials prepared above and dissolve them in terpineol, wherein the mass ratio of zinc oxide nanomaterials to terpineol is 40:60. Disperse the mixture in a high-speed disperser at a speed of 6000 rpm for 2 hours to obtain a sensitive material slurry with good extensibility and flowability.

[0140] ② Place the 6-inch silicon wafer with the printed circuit electrodes onto the spin coater, set the spin coater speed and time. The spin coater program for this sensitive material is set to two segments: the first segment is 500 rpm for 8 seconds, and the second segment is 2500 rpm for 60 seconds. Take 75g of the above sensitive material paste and drop it onto the silicon wafer. Turn on the spin coater and run the set spin coater program. After the spin coater is finished, put the silicon wafer into the oven and dry it at 65°C for 2 hours. After removing the sensitive material adhering to the electrodes with a pin, put it into a muffle furnace and anneal at 400°C for 2 hours.

[0141] (4) Sample cutting, component soldering and packaging

[0142] The annealed sample was cut, the prepared device was soldered using a gold wire bonding machine, and then ceramic encapsulated to obtain the nitric oxide sensor.

[0143] Comparative Example 3

[0144] In the preparation of the MOFs material in Example 1, an excess of surfactant was added. The specific steps included:

[0145] ① Weigh 0.439g of zinc acetate dihydrate into a beaker, add 10ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution A;

[0146] ② Weigh 1.31g of 2-methylimidazole and 0.1267g of CTAB into a beaker, add 20ml of deionized water, and sonicate in an ultrasonic machine for 15min to obtain solution B;

[0147] ③ Pour solution A into solution B and stir at 200 rpm for 5 minutes;

[0148] ④ Pour the mixed solution into a hydrothermal reactor, place it in an oven at 150°C for 1 hour, and then remove it and cool it to room temperature;

[0149] ⑤ Centrifugation resulted in the formation of no MOF materials.

[0150] Comparative Example 4

[0151] A method for fabricating a thin-film nitric oxide sensor, which differs from Example 1 in that the nano-zinc oxide is not prepared using MOF templates, but directly uses commercially available nano-zinc oxide. The specific steps include:

[0152] (1) Homogenization of sensitive materials

[0153] ① Weigh commercial zinc oxide nanomaterials and dissolve them in terpineol, wherein the mass ratio of zinc oxide nanomaterials to terpineol is 40:60. Disperse the mixture in a high-speed disperser at a speed of 6000 rpm for 2 hours to obtain a sensitive material slurry with good extensibility and flowability.

[0154] ② Place the 6-inch silicon wafer with the printed circuit electrodes onto the spin coater, set the spin coater speed and time. The spin coater program for this sensitive material is set to two segments: the first segment is 500 rpm for 8 seconds, and the second segment is 2500 rpm for 60 seconds. Take 75g of the above sensitive material paste and drop it onto the silicon wafer. Turn on the spin coater and run the set spin coater program. After the spin coater is finished, put the silicon wafer into the oven and dry it at 65°C for 2 hours. After removing the sensitive material adhering to the electrodes with a pin, put it into a muffle furnace and anneal at 400°C for 2 hours.

[0155] (2) Sample cutting, component soldering and packaging

[0156] The annealed sample was cut, the prepared device was soldered using a gold wire bonding machine, and then ceramic encapsulated to obtain the thin-film nitric oxide sensor.

[0157] Device gas-sensing performance testing:

[0158] The nitric oxide sensors prepared in Examples 1-5 and Comparative Examples 1, 2, and 4 were subjected to gas-sensing tests. The test platform was the source-meter level multi-channel gas sensing test platform (SMP-4) developed by the Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences. The platform used a multimeter (Agilent U3606A) and a DC power supply (U8002A) to provide the voltage source and for signal acquisition. During the test, gas was injected into the test chamber through a syringe from the inlet, and two symmetrically distributed 300rpm rotating fans were used at the inlet to rapidly mix the gas in the chamber. When the device encountered gas, its resistance changed, which was reflected in the change of voltage value in the multimeter. The parameters of the test platform were set and adjusted using LabVIEW software. All tests were conducted under environmental conditions of 60% RH relative humidity and 25℃ room temperature, with heating powers of 0.01W and 0.025W. The test results are shown in Table 1.

[0159] Table 1. Gas-sensing performance test results of the devices prepared in Examples 1-5 and Comparative Examples 1, 2, and 4.

[0160]

[0161]

[0162] Table 2. Corrosion resistance failure tests of devices prepared in Examples 1-5 and Comparative Examples 1, 2, and 4.

[0163]

[0164] In the table, "OK" indicates that the initial performance can be maintained after a certain number of cycles of injecting 10ppm NO.

[0165] “NG” indicates that the device performance cannot be maintained or the device fails if the required number of cycles of injecting 10ppm NO is not reached.

[0166] from Figure 1 , 2As shown in Tables 1 and 2, the content of the surfactant CTAB affects the morphology and particle size of MOFs. Without surfactant, the particles exhibit irregular shapes; with the addition of a suitable small amount of surfactant (0.02 wt%), the particles exhibit a regular cubic structure with a particle size of approximately 200 nm; when the surfactant concentration is too high (0.2 wt%), the particles gradually increase in size; when the surfactant concentration exceeds 0.2 wt%, the particles break down and the MOF structure disappears. Using the above structure as a template to prepare nano-ZnO sensitive materials ultimately affects the gas-sensing performance of the sensitive materials. Combining Tables 1 and 2, it can be seen that the sensitive materials prepared with relatively regular and compact structural templates can detect low concentrations (10 ppb) of gas, have high sensitivity to high concentrations of gas, and can respond to longer cycles in NO atmospheres, exhibiting higher corrosion resistance. The surfactant content can indirectly control the morphology and particle size of the gas-sensing material, making it suitable for nitric oxide concentration detection in various scenarios.

[0167] from Figure 4 It can be seen that the nitric oxide sensor has good selectivity and is resistant to interference from ammonia, carbon monoxide, methane, and propane gases, thus possessing certain practical application value. Figure 5 and Figure 6 It can be seen that the sensor has a short response and recovery time in both low (1 ppm) and high (50 ppm) nitric oxide environments, and can quickly detect the concentration of nitric oxide, showing good sensitivity.

[0168] This invention first prepares MOF (Metal-Oxide-Factory) materials, then uses the MOF materials as sacrificial templates to prepare metal oxide materials. The thin-film gas-sensitive material is coated onto a silicon wafer with printed electrode circuitry using a spin coater. After annealing and dicing, the device is soldered on a gold wire bonder and then ceramic-encapsulated to obtain a nitric oxide sensor. The surfactant content can indirectly control the morphology and particle size of the gas-sensitive material. The prepared nitric oxide sensor exhibits both high sensitivity and selectivity. Furthermore, the gas-sensitive material has a low operating temperature (low power consumption) and high corrosion resistance, making it a highly applicable method for preparing nitric oxide sensors.

[0169] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of fabricating a thin film nitric oxide sensor, comprising: The method comprises the following steps: ​ S1, uniformly mixing a water-soluble zinc salt with water to obtain an A solution; uniformly mixing 2-methylimidazole, CTAB and water to obtain a B solution; uniformly mixing the A solution and the B solution to obtain a reaction liquid; subjecting the reaction liquid to a hydrothermal reaction, and drying the solid after cooling to obtain a MOFs material; in the reaction liquid, the mass fraction of CTAB is 0.01-0.1wt%; the mass-volume ratio of the zinc content in the water-soluble zinc salt, 2-methylimidazole, CTAB and water is 0.131g:1.31g:0.003-0.0317g:30ml; S2, calcining the MOFs material to obtain a zinc oxide nanomaterial; S3, mixing the zinc oxide nanomaterial with terpineol, and stirring to obtain a slurry; S4, adding the slurry to a silicon wafer, then performing uniform coating, and after the uniform coating is completed, drying and annealing to obtain an annealed device; S5, welding and packaging the annealed device to obtain the thin-film nitric oxide sensor.

2. The method of claim 1, wherein: In S1, the water-soluble zinc salt is a mixture of one or more of zinc acetate, zinc nitrate, zinc chloride, zinc sulfate and zinc gluconate; in the reaction liquid, the mass-volume ratio of the zinc content in the water-soluble zinc salt, 2-methylimidazole, CTAB and water is 0.131g:1.31g:0.0317g:30ml.

3. The method of claim 1, wherein the method further comprises: In S1, after the A solution and the B solution are mixed, stirring is performed at a rotation speed of 200-400rpm to obtain the reaction liquid.

4. The method of claim 1, wherein: In S1, the temperature of the hydrothermal reaction is 135-175℃, and the time is 0.5-2h.

5. The method of claim 1, wherein: In S2, the calcining comprises heating at a heating rate of 0.5-2℃ / min to 400℃, and then maintaining the temperature for 2h.

6. The method of claim 1, wherein: In S3, the mass ratio of the zinc oxide nanomaterial to terpineol is 30:70-60:

40.

7. The method of claim 1, wherein: In S3, the rotation speed of the stirring is 5000-10000rpm, and the time is 0.5-2h.

8. The method of claim 1, wherein: In S4, the uniform coating comprises primary uniform coating and secondary uniform coating; the rotation speed of the primary uniform coating is 500r / min, and the time is 8s; the rotation speed of the secondary uniform coating is 2500r / min, and the time is 60s.

9. The method of claim 1-8, wherein: In S4, the temperature of the drying is 50-80℃, and the time is 2-4h; the temperature of the annealing is 400℃, and the time is 2h.

10. A thin film nitric oxide sensor, characterized by The thin-film nitric oxide sensor is prepared by the method according to any one of claims 1-9.

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