Three-dimensional nanoflower composite gas-sensitive material as well as preparation method and application thereof

Abstract

The invention relates to a three-dimensional nanoflower composite gas-sensitive material as well as a preparation method and application thereof, and belongs to the technical field of gas-sensitive materials. In order to solve the problem that an accurate, rapid and low-cost low-concentration nitrogen dioxide detection method is lacked in the field of environmental monitoring, a tungsten disulfide precursor and selenium powder are subjected to heating treatment to obtain a composite gas-sensitive material with a three-dimensional nanoflower structure. The morphology of the three-dimensional nanoflower is regulated and controlled through selenium doping, and the sensitivity of the gas-sensitive material is improved and the response time is shortened by increasing the contact probability between active sites of the gas-sensitive material and NO2 gas molecules. A gas sensitive element prepared from the gas sensitive material provided by the invention is used for NO2 gas detection at room temperature, the sensitivity to 0.03 ppm NO2 gas is 1.3, the response time is 10.7 seconds, accurate and rapid detection of low-concentration NO2 gas below 0.1 ppm can be realized, and the gas sensitive material has an important application prospect in the field of NO2 gas detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas-sensitive materials, relates to cutting-edge new materials, and in particular to a three-dimensional nanoflower composite gas-sensitive material and a preparation method and application thereof. Background Art

[0002] In current environmental monitoring and protection work, the monitoring of nitrogen dioxide mainly focuses on whether it exceeds the statutory or recommended concentration limits to ensure that air quality meets established health and environmental standards. This approach is based on a strict regulatory framework and aims to effectively control and reduce pollutant emissions and protect the public from the harm of air pollution. However, it is worth noting that the current monitoring system often ignores the potential risks that low-concentration nitrogen dioxide pollution may bring.

[0003] In chemical plants, the generation of nitrogen dioxide is mainly related to factors such as raw materials, reaction conditions, and tail gas treatment in the chemical production process. Although chemical plants usually take measures to strictly control the emission of pollutants to ensure compliance with environmental protection standards, nitrogen dioxide pollution below 0.1ppm may still be generated in certain specific circumstances. For example, when the sealing of chemical equipment is poor, the reaction conditions are improperly controlled, or the tail gas treatment facilities fail, a small amount of nitrogen dioxide may leak into the environment. In addition, in the surrounding areas of chemical plants, low-concentration nitrogen dioxide pollution may also occur due to the influence of meteorological conditions such as wind direction and atmospheric stability.

[0004] If low-concentration nitrogen dioxide pollution cannot be accurately monitored, and the emission of pollutants cannot be discovered and controlled in a timely manner, long-term accumulation will lead to a gradual deterioration of environmental quality and pose a potential threat to the surrounding ecological environment. Although the concentration of nitrogen dioxide below 0.1ppm is relatively low, long-term exposure may still have adverse effects on human health, such as irritating the respiratory mucosa and causing respiratory symptoms; it may also affect lung function and reduce lung capacity.

[0005] An important reason why nitrogen dioxide monitoring rarely pays attention to low-concentration detection is the sensitivity limitation of the detection method. Existing nitrogen dioxide detection technologies, such as electrochemical sensors and non-dispersive ultraviolet absorption methods, have high sensitivity, but when detecting extremely low concentrations (such as below 0.1ppm), they may be affected by factors such as the sensor's own noise and drift, resulting in a decrease in the accuracy of the detection results. Moreover, highly sensitive detection equipment often has a higher cost. For many application scenarios, detecting nitrogen dioxide concentrations below 0.1ppm may not be economically beneficial.

[0006] The invention patent with the authorization number CN118255392B discloses the application of a three-dimensional molybdenum disulfide nanoflower composite material in the detection of nitrogen dioxide gas. Although the material shortens the response time of the nitrogen dioxide material detection, the minimum detection limit is only 0.1ppm, which cannot be used for the detection of nitrogen dioxide gas below 0.1ppm. The field urgently needs a low-cost detection method that can accurately and quickly monitor low-concentration nitrogen dioxide below 0.1ppm, so as to achieve comprehensive and accurate evaluation and control of nitrogen dioxide pollution. Summary of the invention

[0007] In order to solve the problem of lack of accurate, fast and low-cost low-concentration nitrogen dioxide detection method in the field of environmental monitoring, the present invention provides a three-dimensional nanoflower composite gas-sensitive material and its preparation method and application.

[0008] The technical solution of the present invention:

[0009] A method for preparing a three-dimensional nanoflower composite gas-sensitive material, the steps are as follows:

[0010] Step 1: Sodium tungstate dihydrate, thiourea and deionized water are stirred and mixed in a certain mass ratio, sodium dodecylbenzene sulfonate is added to the obtained mixed system and ultrasonically treated, and then oxalic acid is added and stirred to obtain a mixed solution;

[0011] Step 2: Place the mixed solution in a high pressure reactor and heat the high pressure reactor in a water bath at 160-220° C. for 18-24 hours;

[0012] Step 3: The liquid obtained in step 2 is centrifuged with deionized water and ethanol successively, and the precipitate is collected and dried to obtain a tungsten disulfide precursor;

[0013] Step 4: Place the tungsten disulfide precursor obtained in step 3 and selenium powder in a tubular furnace according to a certain mass ratio, and heat them in a mixed atmosphere of hydrogen and argon to obtain a composite gas-sensitive material with a three-dimensional nanoflower structure.

[0014] Furthermore, in step 1, the mass ratio of sodium tungstate dihydrate to thiourea is 1-10:1, the mass ratio of the sum of the mass of sodium tungstate dihydrate and thiourea to deionized water is 1.0-2.5:55-85; the mass ratio of deionized water, sodium dodecylbenzene sulfonate and oxalic acid is 55-85:0.3-0.8:1-4.

[0015] Furthermore, the stirring and mixing time in step 1 is 10 to 40 minutes, the ultrasonic treatment time is 10 to 40 minutes, the ultrasonic treatment power is 200 W, and the stirring time after adding oxalic acid is 10 to 40 minutes.

[0016] Furthermore, the centrifugal speed in step 3 is 5000-8000 rpm, and the centrifugal time is 5-15 min.

[0017] Furthermore, the drying treatment in step three is drying in a vacuum drying oven at 60-120° C. for 12-48 hours.

[0018] Furthermore, in step 4, the mass ratio of the tungsten disulfide precursor to the selenium powder is 1:1-10, the volume percentage of hydrogen in the hydrogen and argon mixed atmosphere is 5%, and the heating treatment is performed at a constant temperature of 400-700° C. for 0.5-3.5 h.

[0019] A three-dimensional nanoflower composite gas-sensitive material prepared by the preparation method provided by the present invention, wherein the three-dimensional nanoflower is composed of a plurality of patterned rod-like structures, the patterned rod-like structures have a plurality of sheet structures, the diameter of the three-dimensional nanoflower is 2 μm, and the specific surface area is 13 m 2 / g.

[0020] A three-dimensional nanoflower composite gas-sensitive material prepared by the present invention in NO 2 Gas detection applications.

[0021] Furthermore, a gas-sensitive element is prepared using a three-dimensional nanoflower composite gas-sensitive material. The preparation method of the gas-sensitive element is as follows: ultrasonically disperse the three-dimensional nanoflower composite gas-sensitive material prepared by the present invention in 1 to 10 times the volume of an ethanol solution to obtain a uniformly dispersed suspension, and then coat the suspension on an Au interdigital electrode that has been cleared with ethanol, and place it at 50 to 120° C. and dry it for 2 to 10 hours to obtain the gas-sensitive element.

[0022] Furthermore, the gas sensor prepared by the three-dimensional nanoflower composite gas-sensitive material prepared by the present invention is placed under the conditions of temperature of 15-35°C and humidity of 20-80% to detect NO in the gas to be tested. 2 The gas concentration is detected.

[0023] Beneficial effects of the present invention:

[0024] The present invention uses selenium Se as an anion dopant to achieve the control of the morphology and interlayer spacing of the three-dimensional nanoflower composite gas-sensitive material, forming a NO- 2 The gas adsorption and desorption channels improve the gas sensing properties. The three-dimensional nanoflowers assembled by Se doping have a rich layer structure, which improves the active sites of the gas-sensitive material and NO 2 The contact probability between gas molecules is more conducive to the improvement of gas sensing properties. The structural distortion caused by Se doping produces abundant sulfur defects, which provide more active sites for NO 2 Gas molecules can more easily enter the gas-sensitive material, shortening the NO 2 Response time of gas detection.

[0025] The three-dimensional nanoflower composite gas-sensitive material provided by the present invention is used to prepare a gas-sensitive element and is used for NO 2 Gas detection, NO concentration of 100ppm 2 The gas sensitivity is 40.78, the response time is 4.6 seconds, and the response time is 0.03ppm NO 2 The gas sensitivity is 1.3, the response time is 10.7 seconds, and it has good repeatability. The three-dimensional nanoflower composite gas-sensitive material provided by the present invention can be used at room temperature of 15-35°C and humidity of 20%-80%, and has a simple use method and high sensitivity.

[0026] The preparation method of the three-dimensional nanoflower composite gas-sensitive material provided by the present invention has the advantages of simple process, low cost, environmentally friendly and non-toxic production process, and the prepared three-dimensional nanoflower composite gas-sensitive material can realize the detection of low-concentration NO below 0.1ppm. 2 Accurate and rapid detection of gases, especially low-concentration NO 2 The field of gas detection has important application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is an X-ray diffraction pattern of the composite gas-sensitive material with a three-dimensional nanoflower structure prepared in Example 1;

[0028] Figure 2 This is a scanning electron microscope image of the composite gas-sensitive material with a three-dimensional nanoflower structure prepared in Example 1;

[0029] Figure 3 This is an atomic force micrograph of the composite gas-sensitive material with a three-dimensional nanoflower structure prepared in Example 1;

[0030] Figure 4 and Figure 5 In order Figure 3 The morphological characteristic curves of position 1 and position 2;

[0031] Figure 6 This is a comparison chart of the sensitivity of the composite gas-sensitive material with a three-dimensional nanoflower structure prepared in Example 1 to detect nitrogen dioxide at different humidity levels;

[0032] Figure 7 This is a sensitivity curve diagram of the gas sensor prepared in Example 5 for detecting nitrogen dioxide at room temperature. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below in conjunction with the embodiments, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the protection scope of the present invention. The process equipment or devices not specifically noted in the following embodiments are all conventional equipment or devices in the art. If not specifically specified, the raw materials used in the embodiments of the present invention can be obtained commercially; if not specifically specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0034] Embodiment 1

[0035] This embodiment provides a method for preparing a three-dimensional nanoflower composite gas-sensitive material, and the specific preparation steps are as follows:

[0036] Step 1: weigh 2 g of sodium tungstate dihydrate and 0.4 g of thiourea, add 70 mL of deionized water and stir for 20 min, add 0.4 g of sodium dodecylbenzene sulfonate to the obtained mixed system and ultrasonically treat for 35 min at 200 W ultrasonic power, then add 2 g of oxalic acid and stir for 25 min to obtain a mixed solution;

[0037] Step 2: placing the mixed solution in a stainless steel autoclave, heating the stainless steel autoclave in a 180° C. water bath for 22 h, and then cooling the stainless steel autoclave to room temperature;

[0038] Step 3: The liquid obtained in step 2 is centrifuged with deionized water and ethanol at 7000 rpm for 10 min, and the precipitate is collected and placed in a vacuum drying oven, and dried at 70° C. for 13 h to obtain a tungsten disulfide precursor;

[0039] Step 4: Take 0.3 g of the tungsten disulfide precursor obtained in step 3 and 1.2 g of selenium powder and place them in a tubular furnace. In a mixed atmosphere of hydrogen and argon with a hydrogen volume percentage of 6%, keep the temperature at 500°C for 3 hours, then collect the product to obtain a composite gas-sensitive material with a three-dimensional nanoflower structure.

[0040] Embodiment 2

[0041] This embodiment provides a method for preparing a three-dimensional nanoflower composite gas-sensitive material, and the specific preparation steps are as follows:

[0042] Step 1: weigh 2 g of sodium tungstate dihydrate and 0.4 g of thiourea, add 70 mL of deionized water and stir for 20 min, add 0.4 g of sodium dodecylbenzene sulfonate to the obtained mixed system and ultrasonically treat for 35 min at 200 W ultrasonic power, then add 2 g of oxalic acid and stir for 25 min to obtain a mixed solution;

[0043] Step 2: placing the mixed solution in a stainless steel autoclave, heating the stainless steel autoclave in a 180° C. water bath for 22 h, and then cooling the stainless steel autoclave to room temperature;

[0044] Step 3: The liquid obtained in step 2 is centrifuged with deionized water and ethanol at 7000 rpm for 10 min, and the precipitate is collected and placed in a vacuum drying oven, and dried at 70° C. for 13 h to obtain a tungsten disulfide precursor;

[0045] Step 4: Take 0.3g of the tungsten disulfide precursor obtained in step 3 and 1.2g of selenium powder and place them in a tubular furnace. In a mixed atmosphere of hydrogen and argon with a hydrogen volume percentage of 7%, keep the temperature at 500°C for 3h, then collect the product to obtain a composite gas-sensitive material with a three-dimensional nanoflower structure.

[0046] Embodiment 3

[0047] This embodiment provides a method for preparing a three-dimensional nanoflower composite gas-sensitive material, and the specific preparation steps are as follows:

[0048] Step 1: Weigh 1.8 g of sodium tungstate dihydrate and 0.3 g of thiourea, add 60 mL of deionized water and stir for 30 min, add 0.3 g of sodium dodecylbenzene sulfonate to the obtained mixed system and ultrasonically treat for 30 min at 200 W ultrasonic power, then add 1.5 g of oxalic acid and stir for 30 min to obtain a mixed solution;

[0049] Step 2: placing the mixed solution in a stainless steel autoclave, heating the stainless steel autoclave in a 200° C. water bath for 20 h, and then cooling the stainless steel autoclave to room temperature;

[0050] Step 3: The liquid obtained in step 2 is centrifuged with deionized water and ethanol at 6000 rpm for 12 min, and the precipitate is collected and placed in a vacuum drying oven, and dried at 80° C. for 10 h to obtain a tungsten disulfide precursor;

[0051] Step 4: Take 0.3 g of the tungsten disulfide precursor obtained in step 3 and 1.5 g of selenium powder and place them in a tubular furnace. In a mixed atmosphere of hydrogen and argon with a hydrogen volume percentage of 6%, keep the temperature at 600°C for 2 hours, then collect the product to obtain a composite gas-sensitive material with a three-dimensional nanoflower structure.

[0052] Embodiment 4

[0053] This embodiment provides a method for preparing a three-dimensional nanoflower composite gas-sensitive material, and the specific preparation steps are as follows:

[0054] Step 1: weigh 2.1 g of sodium tungstate dihydrate and 0.3 g of thiourea, add 75 mL of deionized water and stir for 30 min, add 0.4 g of sodium dodecylbenzene sulfonate to the obtained mixed system and ultrasonically treat for 40 min at 200 W ultrasonic power, then add 2 g of oxalic acid and stir for 35 min to obtain a mixed solution;

[0055] Step 2: placing the mixed solution in a stainless steel autoclave, heating the stainless steel autoclave in a 220° C. water bath for 18 h, and then cooling the stainless steel autoclave to room temperature;

[0056] Step 3: The liquid obtained in step 2 is centrifuged with deionized water and ethanol at 5000 rpm for 15 min, and the precipitate is collected and placed in a vacuum drying oven, and dried at 100° C. for 12 h to obtain a tungsten disulfide precursor;

[0057] Step 4: Take 0.3 g of the tungsten disulfide precursor obtained in step 3 and 1.8 g of selenium powder and place them in a tubular furnace. In a mixed atmosphere of hydrogen and argon with a hydrogen volume percentage of 6%, keep the temperature at 700°C for 1 hour, then collect the product to obtain a composite gas-sensitive material with a three-dimensional nanoflower structure.

[0058] Figure 1 The X-ray diffraction pattern of the composite gas-sensitive material with three-dimensional nanoflower structure prepared in Example 1; Figure 1 It can be seen that the diffraction peaks of the compound, i.e., the 2θ angle values, are 14.2°, 28.9°, 32.7°, 33.5°, 39.5°, 49.5°, 58.4°, 60.4°, and 69.1°, respectively, which are consistent with WS 2 The (002), (004), (100), (101), (103), (105), (110), (112), and (200) crystal phases of the standard card are consistent, confirming the successful synthesis of Se-doped WS 2 Composite material. The 2θ angle value is 14.2° and WS 2 The (100) crystal plane of the standard card is shifted compared to the standard card, which is caused by Se doping.

[0059] Figure 2 This is a scanning electron microscope image of the composite gas-sensitive material with a three-dimensional nanoflower structure prepared in Example 1; Figure 2 It can be clearly seen that Se-doped WS 2 The three-dimensional nanoflower structure of the composite material is composed of several patterned rod-like structures. The diameter of the three-dimensional nanoflower is 2μm and the specific surface area is 13m 2 / g. The patterned rod morphology increases the active sites and NO 2 The contact rate is more conducive to improving gas sensitivity and selectivity.

[0060] Figure 3This is an atomic force micrograph of the composite gas-sensitive material with a three-dimensional nanoflower structure prepared in Example 1; Figure 4 and Figure 5 They are Figure 3 The morphological characteristic curves of position 1 and position 2; Figure 3-Figure 5 It can be seen intuitively that Se-doped WS 2 The composite material has a distinct lamellar structure, and this unique structure helps to improve the sensitivity and selectivity of the gas.

[0061] Figure 6 This is a comparison chart of the sensitivity of the composite gas-sensitive material with a three-dimensional nanoflower structure prepared in Example 1 under different humidity conditions; Figure 6 The change in sensitivity of the composite material under different humidity conditions can be seen intuitively, and combined with the contact angle, it is proved that the material is moisture-resistant.

[0062] Embodiment 5

[0063] This embodiment provides a gas sensing element prepared using the composite gas sensing material with a three-dimensional nanoflower structure prepared in Embodiment 1 as a gas sensing material.

[0064] The specific method for preparing the gas sensor in this embodiment is:

[0065] The two-dimensional WS prepared in Example 1 2 The Se-doped nanosheet assembled three-dimensional nanoflower composite material was ultrasonically dispersed in 6 times the volume of ethanol solution to obtain a uniformly dispersed suspension, which was then spin-coated on an Au interdigital electrode and dried at 70°C for 6 hours to obtain a gas sensor.

[0066] The gas sensing element was tested by static gas distribution method. The specific steps were as follows: first, the gas sensing element to be tested was installed in the gas chamber and connected to the information collection and analysis equipment. At the test temperature of 25°C and the test humidity of 25%, 100 ppm of NO was injected. 2 When the gas-sensitive response is observed to be stable according to the information fed back by the data acquisition system, the air pump is used to pump air to make NO 2 After desorption, the device under test returns to its initial state, completing a gas injection cycle; then 100ppm, 50ppm, 30ppm, 10ppm, 5ppm, 3ppm, 1ppm, 0.5ppm, 0.3ppm, 0.1ppm, 0.05 and 0.03 NO 2 After the gas injection cycle is completed, the following is obtained: Figure 7 The sensitivity curve of the gas sensor for detecting nitrogen dioxide at room temperature is shown in Figure 2. 2 The sensitivity of the gas with a concentration of 100ppm is 40.78, and the sensitivity of NO 2The sensitivity is 1.3 for gases with concentrations as low as 0.03 ppm (30 ppb), and the material has a fast response speed and good adsorption reversibility.

[0067] Table 1 shows the sensitivity and response time of the gas sensor prepared in Test Example 5 at different nitrogen dioxide concentrations, where sensitivity S = R a / R g , R a is the resistance of the sensor in air, R g NO 2 The resistance of the sensor in the atmosphere. During the gas adsorption and desorption process, the time required for the resistance to change by 90% is the response time.

[0068] Table 1

[0069]

[0070]

[0071] Embodiment 6

[0072] This embodiment provides a gas sensing element prepared using the composite gas sensing material with a three-dimensional nanoflower structure prepared in Example 2 as a gas sensing material.

[0073] The specific method for preparing the gas sensor in this embodiment is:

[0074] The two-dimensional WS prepared in Example 2 2 The Se-doped assembled three-dimensional nanoflower composite material of nanosheets was ultrasonically dispersed in 6 times the volume of ethanol solution to obtain a uniformly dispersed suspension, which was then spin-coated on Au interdigital electrodes and dried at 60°C for 4 hours to obtain a gas sensor.

[0075] The gas sensing element was tested by static gas distribution method. The specific steps were as follows: first, the gas sensing element to be tested was installed in the gas chamber and connected to the information collection and analysis equipment. At the test temperature of 30°C and the test humidity of 40%, 100 ppm of NO was injected. 2 When the gas-sensitive response is observed to be stable according to the information fed back by the data acquisition system, the air pump is used to pump air to make NO 2 After desorption, the device under test returns to its initial state, completing a gas injection cycle; then 100ppm, 50ppm, 30ppm, 10ppm, 5ppm, 3ppm, 1ppm, 0.5ppm, 0.3ppm, and 0.1ppm of NO 2 After the gas injection is completed, the sensitivity curve of the gas sensor for detecting nitrogen dioxide is obtained. 2 The sensitivity of the gas with a concentration of 100ppm is 40.78, and the sensitivity of NO 2The sensitivity is 1.1 for gases as low as 0.03 ppm.

Claims

1. A method for preparing a three-dimensional nanoflower composite gas-sensitive material, characterized in that: Here are the steps: Step 1: Sodium tungstate dihydrate, thiourea and deionized water are stirred and mixed in a certain mass ratio, sodium dodecylbenzene sulfonate is added to the obtained mixed system and ultrasonically treated, and then oxalic acid is added and stirred to obtain a mixed solution; Step 2: Place the mixed solution in a high pressure reactor and heat the high pressure reactor in a water bath at 160-220° C. for 18-24 hours; Step 3: The liquid obtained in step 2 is centrifuged with deionized water and ethanol successively, and the precipitate is collected and dried to obtain a tungsten disulfide precursor; Step 4: Place the tungsten disulfide precursor obtained in step 3 and selenium powder in a tubular furnace according to a certain mass ratio, and heat them in a mixed atmosphere of hydrogen and argon to obtain a composite gas-sensitive material with a three-dimensional nanoflower structure.

2. The method for preparing a three-dimensional nanoflower composite gas-sensitive material according to claim 1, characterized in that: In step 1, the mass ratio of sodium tungstate dihydrate to thiourea is 1-10:1, the mass ratio of the sum of the mass of sodium tungstate dihydrate and thiourea to deionized water is 1.0-2.5:55-85; the mass ratio of deionized water, sodium dodecylbenzene sulfonate and oxalic acid is 55-85:0.3-0.8:1-4.

3. The method for preparing a three-dimensional nanoflower composite gas-sensitive material according to claim 1 or 2, characterized in that: The stirring and mixing time in step 1 is 10 to 40 minutes, the ultrasonic treatment time is 10 to 40 minutes, the ultrasonic treatment power is 200W, and the stirring time after adding oxalic acid is 10 to 40 minutes.

4. The method for preparing a three-dimensional nanoflower composite gas-sensitive material according to claim 3, characterized in that: The centrifugal speed in step 3 is 5000-8000 rpm, and the centrifugal time is 5-15 min.

5. The method for preparing a three-dimensional nanoflower composite gas-sensitive material according to claim 4, characterized in that: The drying process in step 3 is to dry the product in a vacuum drying oven at 60 to 120° C. for 12 to 48 hours.

6. The method for preparing a three-dimensional nanoflower composite gas-sensitive material according to claim 5, characterized in that: In step 4, the mass ratio of the tungsten disulfide precursor to the selenium powder is 1:1-10, the volume percentage of hydrogen in the hydrogen and argon mixed atmosphere is 5-8%, and the heating treatment is performed at a constant temperature of 400-700° C. for 0.5-3.5 h.

7. A three-dimensional nanoflower composite gas-sensitive material prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The three-dimensional nanoflower is composed of a plurality of patterned rod-like structures, each of which has a plurality of lamellae. The diameter of the three-dimensional nanoflower is 2 μm, and the specific surface area is 13 m 2 / g.

8. Application of the three-dimensional nanoflower composite gas-sensitive material as claimed in claim 7 in NO2 gas detection.

9. The use of the three-dimensional nanoflower composite gas-sensitive material in NO2 gas detection according to claim 8, characterized in that: A gas-sensitive element is prepared using a three-dimensional nanoflower composite gas-sensitive material. The preparation method of the gas-sensitive element is as follows: ultrasonically disperse the three-dimensional nanoflower composite gas-sensitive material according to claim 7 in 1 to 10 times the volume of an ethanol solution to obtain a uniformly dispersed suspension, and then coat the suspension on an Au interdigital electrode that has been cleared with ethanol, and place it at 50 to 120° C. and dry it for 2 to 10 hours to obtain the gas-sensitive element.

10. The use of the three-dimensional nanoflower composite gas-sensitive material in NO2 gas detection according to claim 9, characterized in that: The gas-sensitive element prepared from the three-dimensional nanoflower composite gas-sensitive material according to claim 7 is placed at a temperature of 15 to 35° C. and a humidity of 20 to 80% to detect the NO2 gas concentration in the gas to be tested.

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