Three-dimensional nanometer flower ball Co3O4-x gas sensitive material, preparation method thereof and acetone gas sensor

Abstract

The invention discloses a three-dimensional nano flower ball Co3O4-x gas sensitive material, a preparation method thereof and an acetone gas sensor, and the preparation method comprises the following steps: preparing a precursor alpha-Co (OH) 2 with a hydrotalcite structure by using cobalt sulfate as a metal salt, ammonia water as a morphology guiding agent and deionized water as a solvent through a coprecipitation method; the precursor alpha-Co (OH) 2 is calcined at the temperature of 200-500 DEG C, three-dimensional nano flower balls Co3O4-x with different sintering temperatures are obtained, and x represents 200 DEG C, 300 DEG C, 400 DEG C and 500 DEG C; the three-dimensional nano flower ball Co3O4-x gas sensitive material prepared by the method is applied to an acetone gas sensor, the acetone gas sensor comprises a chromium-nickel heating wire, a ceramic tube, two gold electrodes, four platinum wires and a hexagonal base, and three-dimensional nano flower ball Co3O4-x gas sensitive reaction layers are uniformly arranged on the outer sides of the ceramic tube and the gold electrodes. The three-dimensional nano flower ball Co3O4-x gas-sensitive material disclosed by the invention has unique three-dimensional nano flower ball morphology and relatively large specific surface area, and the gas-sensitive detection capability of Co3O4 on acetone gas is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas sensors, and relates to a three-dimensional nano-flower sphere Co 3 O 4 -x gas-sensitive material, its preparation method, and an acetone gas sensor. Background Technique

[0002] Acetone is classified as a volatile organic compound (VOC) and has flammable and toxic characteristics. It is very volatile at room temperature, and its volatiles can cause explosions when exposed to open flames in high temperatures or in the air. In addition, acetone also emits a pungent odor, and excessive inhalation of acetone gas by the human body can cause symptoms such as fatigue, headache, and nausea. Acetone gas sensors can also be used as diagnostic tools for diabetic patients because a large number of medical studies have shown that the concentration of acetone gas exhaled by diabetic patients (greater than 1.8 ppm) is 2 to 3 times that of healthy people (0.3 - 0.9 ppm). Monitoring the acetone gas exhaled by the human body provides a new method for non-invasive and timely detection of diabetes.

[0003] Therefore, developing an acetone gas sensor with good selectivity, high sensitivity, and low detection limit has important value, which can be used as both an environmental monitoring tool and an innovative medical detection device. Metal oxide semiconductor (MOS) gas sensors are widely used in chemiresistive gas sensors due to their excellent performance. In the detection of acetone gas, typical p-type materials include Co 3 O 4 Because it has a mixed valence state (Co 2+ / Co 3+ ) Co 3 O 4 is widely used as a gas-sensitive material. The reversible change between the two valence states not only facilitates the generation of adsorbed oxygen but also promotes the generation of oxygen vacancies. In addition, Co 2+ exhibits higher catalytic activity, which is beneficial to the occurrence of the gas-sensitive reaction with acetone. However, Co 3 O 4 also has some defects as a gas-sensitive material, such as poor moisture resistance, low response, and long response / recovery time.

[0004] Regarding the reaction mechanism of MOS materials, active adsorption sites are crucial for the occurrence of the reaction process. Therefore, Co 3 O 4The improvement of gas-sensing performance is mainly considered from the perspective of improving its active sites. Morphology control is an effective means to improve the porous structure and large specific surface area. It can not only increase the diffusion rate of the target gas but also provide more active adsorption sites for the target gas. In addition, defect engineering (such as oxygen vacancies) is also considered an effective method to enhance the active adsorption sites of MOS. However, the current methods for generating oxygen vacancies are relatively complex and difficult to implement. Therefore, it is also very important to develop a green, efficient, and simple strategy for preparing oxygen vacancies. Among the reported synthetic Co 3 O 4 gas-sensing materials, the synthesis methods mostly use hydrothermal methods or prepare unique and excellent morphologies using MOF (Metal Organic Framework) as a template, and then form the gas-sensing material Co 3 O 4 through high-temperature calcination. Although these preparation methods can effectively prepare materials with good performance, they are often relatively complex. There are few reports on preparing the gas-sensing material Co 2 using α-Co(OH) 3 O 4 with a hydrotalcite structure as the raw material. SUMMARY OF THE INVENTION

[0005] The present invention aims to solve the technical problems of low response and poor moisture resistance of the Co 3 O 4 acetone gas sensor in the prior art. The present invention provides a three-dimensional nano-flower sphere Co 3 O 4 -x gas-sensing material, its preparation method, and an acetone gas sensor. The technical solutions adopted are as follows:

[0006] A preparation method of a three-dimensional nano-flower sphere Co 3 O 4 -x gas-sensing material, comprising the steps of:

[0007] S1. Using cobalt sulfate as the metal salt, ammonia water as the morphology guiding agent, and deionized water as the solvent, preparing a precursor α-Co(OH) 2 with a hydrotalcite structure through a co-precipitation method;

[0008] S2. Calcining the precursor α-Co(OH) 2 at 200-500 °C to obtain three-dimensional nano-flower spheres Co 3 O 4 -x at different sintering temperatures, where x represents 200 °C, 300 °C, 400 °C, and 500 °C.

[0009] In one embodiment of the present invention, the step S1 includes:

[0010] S11. Dissolve cobalt sulfate in deionized water and stir at room temperature to obtain a homogeneous cobalt sulfate aqueous solution;

[0011] S12. Add ammonia water to the cobalt sulfate aqueous solution and continuously stir at room temperature until the reaction is complete;

[0012] S13. Centrifuge the fully reacted mixture at a centrifugation speed of 7000 - 9000 rpm to obtain a blue - green precipitate, and wash the blue - green precipitate to obtain the product α - Co(OH) 2 ;

[0013] S14. Lyophilize the product α - Co(OH) 2 for 8 - 12 h to obtain a blue - green precursor α - Co(OH) with a hydrotalcite structure 2 .

[0014] In one embodiment of the present invention, in step S1, the cobalt sulfate is 1 - 3 mmol; the deionized water is 50 - 70 mL; the ammonia water is 145 - 290 μL.

[0015] In one embodiment of the present invention, step S2 includes: placing the precursor α - Co(OH) 2 in a muffle furnace, calcining in an air atmosphere at 200 - 500 °C for 1 - 3 h, with a heating rate of 1 - 5 °C / min, to obtain three - dimensional nanoflower spheres Co 3 O 4 -x at different sintering temperatures.

[0016] A three - dimensional nanoflower sphere Co 3 O 4 -x gas - sensitive material is prepared by using the preparation method of the above - mentioned three - dimensional nanoflower sphere Co 3 O 4 -x gas - sensitive material.

[0017] In one embodiment of the present invention, the above - mentioned three - dimensional nanoflower sphere Co 3 O 4 -x gas - sensitive material is applied to an acetone gas sensor.

[0018] An acetone gas sensor based on the three - dimensional nanoflower sphere Co 3 O 4 -x gas - sensitive material includes: a nichrome heating wire, a ceramic tube, two gold electrodes, four platinum wires, and a hexagonal base;

[0019] The nichrome heating wire passes through the ceramic tube, and both ends of the nichrome heating wire are connected to the hexagonal base;

[0020] Two of the gold electrodes are arranged in parallel on the outer side of the ceramic tube, and each gold electrode is connected to one end of two of the platinum wires, and the other ends of the platinum wires are connected to the hexagonal base;

[0021] The outer sides of the ceramic tube and the gold electrodes are uniformly coated with the three-dimensional nano-flower sphere Co 3 O 4 -x gas-sensitive material to form a three-dimensional nano-flower sphere Co 3 O 4 -x gas-sensitive reaction layer.

[0022] In one embodiment of the present invention, both ends of the chromium-nickel heating wire and the four platinum wires are welded to six corners of the hexagonal base.

[0023] In one embodiment of the present invention, the three-dimensional nano-flower sphere Co 3 O 4 -x gas-sensitive reaction layer preparation method includes:

[0024] a. Mix the three-dimensional nano-flower sphere Co 3 O 4 -x with ethanol by grinding to form a uniformly mixed paste-like gas-sensitive material;

[0025] b. Uniformly apply the paste-like gas-sensitive material on the outer surface of the ceramic tube to form a uniform three-dimensional nano-flower sphere Co 3 O 4 -x thin film;

[0026] c. Place the ceramic tube coated with the three-dimensional nano-flower sphere Co 3 O 4 -x thin film in a muffle furnace for calcination to form a three-dimensional nano-flower sphere Co 3 O 4 -x gas-sensitive reaction layer.

[0027] In one embodiment of the present invention, in step S33, the calcination temperature is 200-500 °C and the calcination time is 1-3 h.

[0028] Advantages of the present invention:

[0029] 1. The present invention synthesizes a three-dimensional nano-flower sphere with a unique morphology and a Co with a rich oxygen vacancy content through a simple two-step method 3 O 4 -x gas-sensitive material. First, a precursor α-Co(OH) with a hydrotalcite structure is prepared by a coprecipitation method 2 , and then the precursor α-Co(OH) is calcined at different temperatures 2 to obtain gas-sensitive materials Co 3 O4 -x has a simple preparation process. By calcining at different temperatures, the content of oxygen vacancies in the material can be effectively controlled. Using α-Co(OH) with a hydrotalcite structure 2 as a raw material to prepare the gas-sensitive material Co 3 O 4 -x can effectively retain its unique morphology;

[0030] 2. The three-dimensional nano-flower sphere Co 3 O 4 -x gas-sensitive material of the present invention has a unique three-dimensional nano-flower sphere morphology and a large specific surface area, providing more active adsorption sites for the target gas (acetone) to be detected. At the same time, the existence of a rich content of oxygen vacancies results in a large number of free electrons on the material surface, which will promote the formation of more active adsorption sites, thus effectively improving the detection ability of Co 3 O 4 -x for acetone, providing a new means for detecting acetone gas for diabetic patients;

[0031] 3. The acetone gas sensor of the present invention exhibits excellent gas-sensitive performance at a low working temperature for acetone gas (200 °C, 100 pmm: 42.11). At the same time, the acetone gas sensor also has an ultra-low theoretical detection ability (8.34 ppb) and an ultra-low actual detection ability (31.25 ppb), which brings great potential for detecting acetone gas at ultra-low concentrations. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flowchart of a method for preparing a three-dimensional nano-flower sphere Co 3 O 4 -x gas-sensitive material provided by an embodiment of the present invention;

[0033] Figure 2 is a scanning electron microscope image of the precursor α-Co(OH) 2 ( Figure 2 a and Figure 2 c) and the gas-sensitive material Co 3 O 4 -200( Figure 2 b and Figure 2 d) provided by an embodiment of the present invention;

[0034] Figure 3 is the gas-sensitive material Co 3 O 4 -200( Figure 3 a), the gas-sensitive material Co 3 O 4 -300( Figure 3 b), the gas-sensitive material Co 3 O4 -400(3c) and gas sensitive material Co 3 O 4 -500( Figure 3 d) SEM image;

[0035] Figure 4 The precursor α-Co(OH) provided in the embodiment of the present invention is 2 X-ray diffraction pattern of

[0036] Figure 5 The gas-sensitive material Co provided in the embodiment of the present invention 3 O 4 -X-ray diffraction pattern of x;

[0037] Figure 6 The embodiment of the present invention provides a three-dimensional nano flower ball Co 3 O 4 -Schematic diagram of the structure of the acetone gas sensor made of x gas sensitive material;

[0038] Figure 7 The embodiment of the present invention provides a three-dimensional nano flower ball Co 3 O 4 -x gas-sensitive material acetone gas sensor's response trend chart to 2ppm acetone at different working temperatures;

[0039] Figure 8 The embodiment of the present invention provides a three-dimensional nano flower ball Co 3 O 4 -x acetone gas sensor at the optimal working temperature (200 ℃) to different concentrations of acetone continuous response change curve;

[0040] Figure 9 The gas-sensitive material Co provided in the embodiment of the present invention 3 O 4 -Electron paramagnetic resonance pattern of x;

[0041] Figure 10 The embodiment of the present invention provides a three-dimensional nano flower ball Co 3 O 4 -200 acetone gas sensor at the optimal working temperature (200℃) with the lowest theoretical detection limit;

[0042] Figure 11 The embodiment of the present invention provides a three-dimensional nano flower ball Co 3 O 4 -200 gas sensitive material acetone gas sensor response value to 2ppm of each gas at the optimal working temperature (200℃);

[0043] Figure 12is the acetone gas sensor based on the three-dimensional nano-flower ball Co 3 O 4 -200 gas-sensitive material's response value to 2 ppm acetone at different humidities. Detailed implementation manners

[0044] The present invention will be described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0045] Example 1:

[0046] The present invention provides a preparation method of a three-dimensional nano-flower ball Co 3 O 4 -x gas-sensitive material. Referring to the attached Figure 1 , it includes the following steps:

[0047] S1. Using cobalt sulfate as the metal salt, ammonia water as the morphology guiding agent, and deionized water as the solvent, a precursor α-Co(OH) 2 is prepared by the coprecipitation method;

[0048] S2. Calcining the precursor α-Co(OH) 2 at 200 - 500 °C to obtain three-dimensional nano-flower balls Co 3 O 4 -x at different sintering temperatures, where x represents 200 °C, 300 °C, 400 °C, and 500 °C.

[0049] The present invention uses α-Co(OH) 2 with a hydrotalcite structure as the raw material to prepare the gas-sensitive material Co 3 O 4 -x, which can effectively retain its unique morphology and has a simple preparation process.

[0050] In this example, step S1 includes:

[0051] S11. Dissolve 1 - 3 mmol of cobalt sulfate in 50 - 70 mL of deionized water and stir at room temperature to obtain a uniform cobalt sulfate aqueous solution;

[0052] S12. Add 145 - 290 μL of ammonia water to the cobalt sulfate aqueous solution and continuously stir at room temperature until the reaction is complete;

[0053] S13. Centrifuge the fully reacted mixture at a centrifugation speed of 7000 - 9000 rpm to obtain a blue-green precipitate, and wash the blue-green precipitate to obtain the product α-Co(OH) 2 ;

[0054] S14. The product α-Co(OH) 2Freeze-dry for 8 to 12 h to obtain a blue-green precursor α-Co(OH) with a hydrotalcite structure 2 .

[0055] In S1, the hydroxide ions in ammonia water combine with the cobalt ions in cobalt sulfate to form Co(OH) 2 nanosheets; at the same time, due to the spatial effect caused by the presence of ammonium ions and sulfate ions, the nanosheets curl, forming a nano-flower spherical morphology of Co(OH) 2 , that is, having a hydrotalcite structure.

[0056] In this embodiment, step S2 includes: placing the precursor α-Co(OH) 2 in a muffle furnace and calcining it at 200 to 500 °C for 1 to 3 h in an air atmosphere with a heating rate of 1 to 5 °C / min to obtain three-dimensional nano-flower spheres Co 3 O 4 -x. Calcining at different temperatures can effectively control the oxygen vacancy content in the material, and at the same time, the morphology of the material will also change.

[0057] This embodiment also provides a three-dimensional nano-flower sphere Co 3 O 4 -x gas-sensitive material, which is prepared by using the preparation method of the above three-dimensional nano-flower sphere Co 3 O 4 -x gas-sensitive material.

[0058] The precursor α-Co(OH) with a hydrotalcite structure prepared by the preparation method in this embodiment 2 and the three-dimensional nano-flower sphere Co 3 O 4 -x. Specifically, the preparation method: Step S1: Dissolve 2 mmol of cobalt sulfate in 60 mL of deionized water and stir at room temperature for 60 min to obtain a uniform cobalt sulfate aqueous solution; add 220 μL of ammonia water to the cobalt sulfate aqueous solution and continuously stir at room temperature until the reaction is complete, and the stirring time is 10 h; transfer the fully reacted mixture to a centrifuge tube for centrifugation at a speed of 8000 rpm to obtain a blue-green precipitate, and wash the blue-green precipitate with deionized water and ethanol respectively to obtain the product α-Co(OH) 2 ; place the product α-Co(OH) 2 in a freeze dryer and freeze-dry for 10 h to obtain a blue-green precursor α-Co(OH) with a hydrotalcite structure 2 . Step S2: Place the precursor α-Co(OH) 2 in a muffle furnace and calcine it at 200 to 500 °C for 2 h in an air atmosphere with a heating rate of 1 °C / min to obtain three-dimensional nano-flower spheres Co 3 O4 -x.

[0059] The precursor α-Co(OH) obtained by the above preparation method 2 and the gas-sensitive material Co 3 O 4 -x were detected. The precursor α-Co(OH) 2 ( Figure 2 a and Figure 2 c) and the gas-sensitive material Co 3 O 4 -200( Figure 2 b and Figure 2 d) are shown in the attached Figure 2 . It can be observed from the attached Figure 2 that α-Co(OH) 2 and Co 3 O 4 -200 both exhibit the morphology of three-dimensional nano-flower spheres, with a relatively large specific surface area. At the same time, by calcining at a temperature of 200 °C to form the gas-sensitive material, its unique morphology can be effectively retained.

[0060] The scanning electron micrograph of the gas-sensitive material Co 3 O 4 -200 is shown in the attached Figure 3 a. The scanning electron micrograph of the gas-sensitive material Co 3 O 4 -300 is shown in the attached Figure 3 b. The scanning electron micrograph of the gas-sensitive material Co 3 O 4 -400 is shown in the attached Figure 3 c. The scanning electron micrograph of the gas-sensitive material Co 3 O 4 -500 is shown in the attached Figure 3 d. It can be found from the attached Figure 3 that as the temperature increases, the collapse of the nano-flower spheres with a three-dimensional morphology occurs in the structure, resulting in a denser morphology of the material, a decrease in the specific surface area of the material, a decrease in the active sites, a decrease in the oxygen species adsorbed on the surface of the gas-sensitive material, and thus a decrease in the gas-sensitive performance of the material.

[0061] The X-ray diffraction pattern of the precursor α-Co(OH) 2 is referred to the attached Figure 4 . The X-ray diffraction pattern of the gas-sensitive material Co 3 O 4 -x is referred to the attached Figure 5 . It can be found that the precursor α-Co(OH) 2 is consistent with the standard card JCPDS NO. 46-0605. In addition, the gas-sensitive material Co 3 O 4-x corresponds to the standard card JCPDS NO. 43-1003, indicating that the prepared gas-sensitive material is relatively pure without other impurity elements.

[0062] The three-dimensional nanoflower sphere Co 3 O 4 -x in this example can be applied to an acetone gas sensor. Since the three-dimensional nanoflower sphere Co 3 O 4 -x has a unique three-dimensional nanoflower spherical morphology and a large specific surface area, providing more active adsorption sites for the target gas (acetone) to be detected. Meanwhile, the existence of a rich oxygen vacancy content results in a large number of free electrons on the material surface, which will promote the formation of more active adsorption sites, thus effectively improving the detection ability of Co 3 O 4 -x for acetone.

[0063] Example 2:

[0064] This example provides an acetone gas sensor based on the three-dimensional nanoflower sphere Co 3 O 4 -x gas-sensitive material. Referring to the appendix Figure 5 , this acetone gas sensor includes: a nichrome heating wire 2, a ceramic tube 1, two gold electrodes 3, four platinum wires 5, and a hexagonal base 6. The nichrome heating wire 2 runs through the ceramic tube 1, and both ends of the nichrome heating wire 2 are connected to the hexagonal base 6; the two gold electrodes 3 are arranged in parallel on the outer side of the ceramic tube 1, and each gold electrode 3 is connected to one end of two platinum wires 5, and the other ends of the platinum wires 5 are connected to the hexagonal base 6; the outer sides of the ceramic tube 1 and the gold electrodes 3 are evenly coated with the three-dimensional nanoflower sphere Co 3 O 4 -x gas-sensitive material to form a three-dimensional nanoflower sphere Co 3 O 4 -x gas-sensitive reaction layer 4. The resistance value of the nichrome heating wire 2 is 20 - 50 kΩ, and both ends of the nichrome heating wire 2 and the four platinum wires 5 are respectively welded to six corners of the hexagonal base 6.

[0065] In this example, the preparation method of the three-dimensional nanoflower sphere Co 3 O 4 -x gas-sensitive reaction layer includes:

[0066] a. Mix the three-dimensional nanoflower sphere Co 3 O 4 -x with ethanol by grinding to form a uniformly mixed paste-like gas-sensitive material;

[0067] b. Apply the paste-like gas-sensitive material evenly on the outer surface of the ceramic tube 1 to form a uniform three-dimensional nanoflower sphere Co 3 O 4-x thin film;

[0068] c. Place the ceramic tube coated with three-dimensional nano-flower sphere Co 3 O 4 -x thin film in a muffle furnace for calcination. The calcination temperature is 200 - 500 °C, and the calcination time is 1 - 3 h to form a three-dimensional nano-flower sphere Co 3 O 4 -x gas-sensitive reaction layer 4.

[0069] Take the prepared three-dimensional nano-flower sphere Co 3 O 4 -x as the gas-sensitive material, and perform material coating, assembly, and welding according to the process of a lateral-heating type device to complete the preparation of an acetone gas sensor based on the three-dimensional nano-spherical Co 3 O 4 -x gas-sensitive material.

[0070] The present invention provides an application of an acetone gas sensor based on a three-dimensional nano-flower sphere Co 3 O 4 -x gas-sensitive material in the detection of acetone gas. The acetone gas sensor of this embodiment exhibits excellent gas-sensitive performance at a lower operating temperature for acetone gas (200 °C, 100 pmm: 42.11). At the same time, this acetone gas sensor also has an ultra-low theoretical detection limit (8.34 ppb) and an ultra-low actual detection limit (31.25 ppb), which brings great potential for the detection of ultra-low concentration acetone gas.

[0071] In addition, since the exhaled gas of the human body has a relatively high humidity (89 - 97% RH), the influence of relative humidity on the sensor performance must be considered when it is used as an important medical instrument for diabetes diagnosis. The humidity resistance of the sensor Co 3 O 4 -200 was detected (24.70 - 90.50% RH), and the results show that the sensor Co 3 O 4 -200 has excellent humidity resistance performance. Therefore, the sensor Co 3 O 4 -200 proposed by the present invention can provide a new method for non-invasive and timely detection of diabetes by monitoring the acetone gas exhaled by the human body.

[0072] Figure 7 For the change trend of the response of the acetone gas sensor based on the three-dimensional nano-flower sphere Co 3 O 4 -x gas-sensitive material to 2 ppm acetone gas at different temperatures, it can be observed that the optimal operating temperature of the sensor Co 3 O 4 -x is 200 °C.

[0073] Figure 8 For the acetone gas sensor based on the three-dimensional nano-flower sphere Co 3 O 4 -x gas-sensitive material, the continuous response change curve of different concentrations of acetone at the optimal working temperature (200 °C) can be observed. It can be seen that the gas-sensing performance of the sensor Co 3 O 4 -200 is significantly higher than that of other sensors.

[0074] In addition, Figure 9 For the electron paramagnetic resonance diagram of the gas-sensitive material Co 3 O 4 -x, as the calcination temperature increases, the peak intensity of the gas-sensitive material Co 3 O 4 -x weakens, indicating that the gas-sensitive material Co 3 O 4 -200 has the highest oxygen vacancy content. Through gas-sensing performance testing and electron paramagnetic resonance characterization, it is shown that calcination at different temperatures can effectively control the oxygen vacancy content in the material, and a good relationship is established between the surface defects (oxygen vacancies) of the material and the gas-sensing performance.

[0075] Figure 10 For the calculation of the lowest theoretical detection limit of the acetone gas sensor based on the three-dimensional nano-flower sphere Co 3 O 4 -200 gas-sensitive material, the sensor Co 3 O 4 -200 has an ultra-low detection limit of 8.34 ppb, which brings great potential for the detection of ultra-low concentration acetone gas.

[0076] Figure 11 For the detection of 2 ppm different interfering gases by the acetone gas sensor based on the three-dimensional nano-flower sphere Co 3 O 4 -200 gas-sensitive material at the optimal working temperature (200 °C), it can be seen that the sensor Co 3 O 4 -200 has good selectivity for acetone.

[0077] Figure 12 For the response change of the acetone gas sensor based on the three-dimensional nano-flower sphere Co 3 O 4 -200 gas-sensitive material to 2 ppm acetone in different humidity atmospheres, it can be seen that the sensor Co 3 O 4 -200 has good anti-humidity performance.

[0078] Through the above experimental data, the prepared three-dimensional nano-flower sphere Co 3 O 4 -x acetone gas sensor has excellent gas-sensing performance for acetone gas. The optimal working temperature is 200 °C, the response to 100 ppm acetone is 42.11, and it has good anti-humidity performance. The acetone gas sensor based on the three-dimensional nano-flower sphere Co 3 O 4 -x of the present invention has good gas-sensing performance and can effectively meet the needs of environmental monitoring and health monitoring.

[0079] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be covered by the protection scope of the present invention.

Claims

1. A method for preparing a three-dimensional nano-flower ball Co3O4-x gas-sensitive material, characterized in that: Includes steps: S1. Using cobalt sulfate as metal salt, ammonia water as morphology directing agent and deionized water as solvent, a precursor α-Co(OH)2 with a hydrotalcite structure was prepared by coprecipitation method; S2. calcining the precursor α-Co(OH)2 at 200-500°C to obtain three-dimensional nano flower balls Co3O4-x with different sintering temperatures, where x represents 200°C, 300°C, 400°C and 500°C.

2. The method for preparing a three-dimensional nano-flower ball Co3O4-x gas-sensitive material according to claim 1, characterized in that: The step S1 comprises: S11, dissolving cobalt sulfate in deionized water, and stirring at room temperature to obtain a uniform cobalt sulfate aqueous solution; S12, adding aqueous ammonia to the aqueous cobalt sulfate solution, and continuously stirring at room temperature until the reaction is sufficient; S13, centrifuging the mixed solution after sufficient reaction at a centrifugal speed of 7000-9000 rpm to obtain a blue-green precipitate, washing the blue-green precipitate to obtain a product α-Co(OH)2; S14. Freeze-dry the product α-Co(OH)2 for 8 to 12 hours to obtain a blue-green precursor α-Co(OH)2 having a hydrotalcite structure.

3. The method for preparing a three-dimensional nano-flower ball Co3O4-x gas-sensitive material according to claim 2, characterized in that: In the step S1, the amount of cobalt sulfate is 1-3 mmol; the amount of deionized water is 50-70 mL; and the amount of ammonia water is 145-290 μL.

4. The method for preparing a three-dimensional nano-flower ball Co3O4-x gas-sensitive material according to claim 1, characterized in that: The step S2 comprises: placing the precursor α-Co(OH)2 in a muffle furnace, calcining at 200-500°C for 1-3h in an air atmosphere, with a heating rate of 1-5°C / min, to obtain three-dimensional nano-flower balls Co3O4-x with different sintering temperatures.

5. A three-dimensional nano-flower ball Co3O4-x gas-sensitive material, characterized in that: The three-dimensional nano flower ball Co3O4-x gas-sensitive material is prepared by the preparation method of any one of claims 1 to 4.

6. The three-dimensional nano-flower ball Co3O4-x gas-sensitive material according to claim 5, characterized in that: Used in acetone gas sensor.

7. An acetone gas sensor based on three-dimensional nano-flower ball Co3O4-x gas-sensitive material, characterized in that: include: Chrome-nickel heating wire, ceramic tube, two gold electrodes, four platinum wires and hexagonal base; The chromium-nickel heating wire runs through the ceramic tube, and both ends of the chromium-nickel heating wire are connected to the hexagonal base; The two gold electrodes are arranged in parallel on the outside of the ceramic tube, and each of the gold electrodes is connected to one end of the two platinum wires, and the other end of the platinum wire is connected to the hexagonal base; The outer sides of the ceramic tube and the gold electrode are uniformly coated with the three-dimensional nano-flower ball Co3O4-x gas-sensitive material according to claim 5 to form a three-dimensional nano-flower ball Co3O4-x gas-sensitive reaction layer.

8. The acetone gas sensor based on the three-dimensional nano-flower ball Co3O4-x gas-sensitive material according to claim 7 is characterized in that: The two ends of the chromium-nickel heating wire and the four platinum wires are respectively welded to the six corners of the hexagonal base.

9. The acetone gas sensor based on the three-dimensional nano-flower ball Co3O4-x gas-sensitive material according to claim 7, characterized in that: The preparation method of the three-dimensional nano flower ball Co3O4-x gas-sensitive reaction layer comprises: a. Grinding and mixing the three-dimensional nano flower ball Co3O4-x with ethanol to form a uniformly mixed paste-like gas-sensitive material; b. Evenly apply the paste-like gas-sensitive material on the outer surface of the ceramic tube to form a uniform three-dimensional nano-flower ball Co3O4-x film; c. The ceramic tube coated with the three-dimensional nano flower ball Co3O4-x film is placed in a muffle furnace for calcination to form a three-dimensional nano flower ball Co3O4-x gas-sensitive reaction layer.

10. The acetone gas sensor based on the three-dimensional nano-flower ball Co3O4-x gas-sensitive material according to claim 9, characterized in that: In the step S33, the calcination temperature is 200-500°C, and the calcination time is 1-3 hours.

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