阅读说明：本技术 一种对低浓度丙酮敏感的氧化锌/四氧化三钴异质结薄膜 (zinc oxide/cobaltosic oxide heterojunction thin films sensitive to low-concentration acetone ) 是由 薛庆忠 李坤 李小芳 常晓 熊雅 乔煦容 王萍 于 2019-10-25 设计创作，主要内容包括：本发明提供了一种可用于低浓度丙酮检测的氧化锌/四氧化三钴异质结薄膜的制备方法,属于气敏传感器技术领域。我们先在室温下合成ZIF-L,然后再将其与钴源、二甲基咪唑混合得到ZIF-L/ZIF-67复合物,将所得产物在管式炉空气氛围下热处理两小时,所得产物然后进行气敏测试。该样品在低浓度500ppb丙酮下,仍然具有较高的响应值(2.12)和较短的响应/恢复时间(21秒/25秒)。此传感器薄膜制备方法简单,原料成本低,材料膜性能优异,具有很好的应用价值和前景。(The invention provides a preparation method of zinc oxide/cobaltosic oxide heterojunction films for low-concentration acetone detection, which belongs to the technical field of gas sensors.A ZIF-L is synthesized at room temperature, then the ZIF-L/ZIF-67 compound is obtained by mixing the ZIF-L with a cobalt source and dimethylimidazole, the obtained product is subjected to heat treatment for two hours in the air atmosphere of a tube furnace, and then the gas-sensitive test is carried out on the obtained product.)

The preparation process of kinds of zinc oxide/cobaltosic oxide heterojunction film sensitive to low concentration acetone includes the following steps:

(1) dissolving quantitative zinc nitrate hexahydrate and dimethylimidazole in deionized water, and stirring for 4 hours;

(2) centrifuging and washing the reaction product obtained in the step (1) for multiple times by using deionized water, and drying a centrifuged sample at 70 ℃ to obtain ZIF-L powder;

(3) dissolving a proper amount of cobalt nitrate hexahydrate in quantitative methanol solution, and stirring for 15 minutes;

(4) , dissolving the ZIF-L powder in the step (2) in the cobalt source solution in the step (3) quantitatively, and ultrasonically stirring for 30 minutes;

(5) dissolving quantitative dimethyl imidazole in quantitative methanol solution, and stirring for 15 minutes;

(6) injecting the reaction solution in the step (5) into the solution in the step (4), and standing and reacting for 24 hours at room temperature;

(7) centrifuging and washing the product obtained in the step (6) for multiple times by using a methanol solution, and drying a sample obtained after centrifugation at 70 ℃ to obtain ZIF-L/ZIF-67 nano composite powder;

(8) calcining the ZIF-L/ZIF-67 nano composite powder obtained in the step (7) in a tubular furnace in the air atmosphere at the temperature of 400 ℃ and the heating rate of 2 ℃ per minute to obtain zinc oxide/cobaltosic oxide nano composite black powder;

(9) taking a proper amount of zinc oxide/cobaltosic oxide powder, dispersing with deionized water, then dropwise coating the mixture on a ceramic chip printed with a platinum interdigital electrode, putting the dropwise coated film in an oven for 2 hours after the dropwise coated film is completely dried, and setting the temperature in the oven to be 60 ℃, thereby finally obtaining the test substrate.

The zinc oxide/cobaltosic oxide obtained by the process has high response to low-concentration (ppb level) acetone, and has high response/recovery speed and good stability.

Technical Field

The invention belongs to the technical field of gas sensors, and particularly relates to preparation of MOF (metal organic framework) -derived zinc oxide/cobaltosic oxide films and gas-sensitive performance research on low-concentration acetone.

Background

Acetone is an organic solvent for manufacturing materials such as explosives, rubber, plastics, fibers and the like, is also a raw material for synthesizing organic matters such as ketene, polyisoprene rubber, epoxy resin and the like, and has application in fields such as military affairs, chemical engineering, medical treatment and the like in areas (Sens. activators B: chem.,2015,209,368 376). however, acetone gas as colorless toxic gases can cause irreversible damage to human bodies and environment, the human bodies are exposed in an acetone atmosphere for a long time, even trace (less than or equal to 1ppm) of acetone can cause the human bodies to have phenomena of inflammation of the nose and lung, headache, dizziness, chronic poisoning of regurgitation and the like, and can damage the heart, the kidney and the nervous system of the human bodies more seriously, although high-concentration acetone can be sensed through olfaction (the acetone smell threshold of the human bodies is about 100ppm), the trace of acetone cannot be sensed through olfaction), and in addition, in the medical field, diabetes mellitus can be diagnosed through detecting the trace acetone concentration in exhaled air of the human bodies (healthy people: 0.3-0.9ppm, diabetic patients: more than 1.8ppm) (Adv.17037, and the trace of acetone has important value in the field of real-time monitoring and environmental conditions such as the environmental monitoring.

Cobaltosic oxide is a common p-type semiconductor, and research shows that cobaltosic oxide has good gas-sensitive performance to acetone gas (Sens. activators B: Chem.,2017,242, 369-377). Up to date, most of cobaltosic oxide sensors researched by people are composed of too long nano fibers (Sens. activators B: Chem,2019,297,126-746), nano arrays (Sens. activators B: Chem,.2016,235:222-231), MOF (metal organic framework) derived hollow cage structures (Sens. activators B: Chem,.2016,225:158-166), and the like, wherein, cobaltosic oxide derived from ZIF-67 (zeolitic imidazolate framework-67) is still suitable for being recovered in trace acetone detection, has poor performance and is still suitable for being recovered in high acetone detection, and has low recovery time ( ppm).

In recent years, a novel two-dimensional graphene material is applied to fields in the fields of tribology, electrochemistry, optics and the like due to the special structure and excellent performance, wherein, the zinc oxide nano sheet derived from ZIF-L (zeolite imidazole ester framework-L) is taken as a derivative of MOF, so that the zinc oxide nano sheet has relatively large specific surface area and abundant surface pore structure, so that the zinc oxide nano sheet has remarkable gas adsorption capacity, and can play a role of in the field of gas sensing.

In order to realize high-sensitivity and rapid detection of low-concentration acetone, ZIF-L is synthesized by taking a zinc source and imidazole as reactants at room temperature and water as a solvent, then ZIF-L, a cobalt source and imidazole are synthesized into a ZIF-L/ZIF-67 compound by taking methanol as a solvent at room temperature, the ZIF-L, the cobalt source and the imidazole are calcined in a tubular furnace to obtain a zinc oxide/cobaltosic oxide compound, and finally a zinc oxide/cobaltosic oxide device is prepared by using a dripping method, and the sensitivity of pure zinc oxide, pure cobaltosic oxide and the zinc oxide/cobaltosic oxide compound to acetone is compared. The zinc oxide/cobaltosic oxide can be prepared only at room temperature, the method is simple, the response recovery time to low-concentration acetone is short, the stability is high, and the work has important guiding significance for developing low-concentration acetone sensors.

Disclosure of Invention

The invention aims to provide a preparation method of sensor membranes capable of detecting low-concentration acetone.

The implementation of the invention is briefly described below by taking zinc nitrate hexahydrate as an example. Firstly, preparing ZIF-L/ZIF-67 nano composite structure powder, and then calcining to obtain zinc oxide/cobaltosic oxide composite black powder. And ultrasonically stirring and uniformly mixing a proper amount of powder and deionized water, dripping the mixture on a platinum interdigital electrode, drying the membrane, placing the membrane in an oven, drying the membrane for 2 hours at 60 ℃, and taking out the membrane to obtain the test substrate. The zinc oxide/cobaltosic oxide device can be realized by the following specific steps:

(1) dissolving quantitative zinc nitrate hexahydrate and dimethylimidazole in deionized water, and stirring for 4 hours;

(2) centrifuging and washing the reaction product obtained in the step (1) for multiple times by using deionized water, and drying a centrifuged sample at 70 ℃ to obtain ZIF-L powder;

(3) dissolving a proper amount of cobalt nitrate hexahydrate in quantitative methanol solution, and stirring for 15 minutes;

(4) , dissolving the ZIF-L powder in the step (2) in the cobalt source solution in the step (3) quantitatively, and ultrasonically stirring for 30 minutes;

(5) dissolving quantitative dimethyl imidazole in quantitative methanol solution, and stirring for 15 minutes;

(6) injecting the reaction solution in the step (5) into the solution in the step (4), and standing and reacting for 24 hours at room temperature;

(7) centrifuging and washing the product obtained in the step (6) for multiple times by using a methanol solution, and drying a sample obtained after centrifugation at 70 ℃ to obtain ZIF-L/ZIF-67 nano composite powder;

(8) calcining the ZIF-L/ZIF-67 nano composite powder obtained in the step (7) in a tubular furnace in the air atmosphere at the temperature of 400 ℃ and the heating rate of 2 ℃ per minute to obtain zinc oxide/cobaltosic oxide nano composite black powder;

(9) taking a proper amount of zinc oxide/cobaltosic oxide powder, dispersing with deionized water, then dropwise coating the mixture on a ceramic chip printed with a platinum interdigital electrode, putting the dropwise coated film in an oven for 2 hours after the dropwise coated film is completely dried, and setting the temperature in the oven to be 60 ℃, thereby finally obtaining the test substrate.

The zinc oxide/cobaltosic oxide device can be obtained by the process. When no cobalt nitrate hexahydrate is added, pure zinc oxide is obtained by directly calcining ZIF-L, and when no zinc nitrate hexahydrate is added, cobaltosic oxide is obtained by calcining. Comparing the response of pure zinc oxide, pure cobaltosic oxide and zinc oxide/cobaltosic oxide to 500ppb acetone at 300 ℃, the air-sensitive performance of the zinc oxide/cobaltosic oxide to the acetone is found to be the best, the response value is 2.12, and the response/recovery time is only 21 seconds/25 seconds. At the same time, we also tested the response of zinc oxide/cobaltosic oxide to 100-500ppb acetone and found that it still has a good characteristic curve. And 500ppb acetone is subjected to cycle test, so that the stability is good, and the requirement of practical application can be met.

The preparation method of the zinc oxide/cobaltosic oxide film provided by the invention can realize the detection of low-concentration acetone, and has short response/recovery time. The method has the advantages of simple preparation, low raw material cost, good repeatability, and good application value and prospect.

Drawings

FIG. 1 is a scanning electron microscope photograph of ZIF-L, ZIF-67, ZIF-L/ZIF-67, zinc oxide/cobaltosic oxide nanocomposites.

FIG. 2 is a graph showing the response of pure zinc oxide, pure cobaltosic oxide, and zinc oxide/cobaltosic oxide nanocomposite to 100-500ppb acetone.

FIG. 3 is a graph of resistance cycling test of zinc oxide/cobaltosic oxide versus 500ppb acetone at 300 ℃.

Detailed Description

The present invention is described in detail below with reference to the drawings and examples.