Acetone sensor based on boron-doped cobalt tetroxide with amorphous / crystalline heterostructure, preparation method and application thereof

Abstract

An acetone sensor based on boron-doped cobalt tetroxide with an amorphous / crystalline heterostructure, as well as its preparation method and application, belongs to the field of gas sensor technology. The sensor consists of an Al2O3 ceramic tube substrate, two parallel and separate annular Au electrodes coated on the outer surface of the ceramic tube substrate, a gas-sensitive film coated on the outer surface of the ceramic tube and the annular Au electrodes, and a nickel-chromium alloy heating coil passing through the interior of the ceramic tube. The gas-sensitive film is made of boron-doped cobalt tetroxide with an amorphous / crystalline heterostructure. This unique amorphous / crystalline heterostructure not only maintains the stable structure of the crystalline material but also leverages the advantages of the amorphous structure, such as high electron delocalization and a large number of reaction sites, thereby improving the acetone gas-sensing performance of the cobalt tetroxide material. The resulting sensor has high sensitivity to acetone and a low detection limit, and has good application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas sensors, and in particular relates to an acetone sensor based on boron-doped cobalt tetroxide with an amorphous / crystalline heterostructure, a preparation method and application of the sensor in acetone detection. Background Art

[0002] Accurately detecting acetone gas concentration in the atmospheric environment has significant research significance and practical value in the field of gas detection. Acetone, a typical volatile organic compound, poses a serious threat to human health, making it a toxic and hazardous gas that urgently needs detection. Furthermore, acetone can serve as a unique exhaled breath marker, potentially useful for the early diagnosis of diabetes. For example, the acetone concentration in the exhaled breath of healthy individuals ranges from 0.3 to 0.9 ppm, while that of diabetics typically exceeds 1.8 ppm. Therefore, accurate acetone gas detection not only provides theoretical data for monitoring atmospheric pollution and improving atmospheric environmental governance, but also offers a non-invasive detection technology for the diagnosis and monitoring of diabetes.

[0003] Traditional analytical instruments, such as gas chromatography, offer high precision for detecting gaseous acetone. However, their bulk and complex operating procedures make them difficult to use in portable instruments and for on-site testing. In contrast, resistive gas sensors based on semiconductor oxides offer a novel approach for detecting gaseous acetone. These devices, with their low cost, simple structure, and ease of device integration, have become a rapidly developing gas detection technology. While n-type semiconductor oxides, such as tin dioxide and zinc oxide, offer high sensitivity and fast response for acetone detection, they suffer from poor selectivity and stability. In recent years, p-type semiconductor materials, such as cobalt tetroxide, have provided an alternative approach for acetone detection. In particular, cobalt tetroxide exhibits excellent catalytic activity in the catalytic oxidation of acetone, providing a theoretical basis for the construction of high-performance acetone sensors. However, the gas sensitivity of cobalt tetroxide materials for acetone detection still needs to be further improved, and manipulating the microstructure of cobalt tetroxide materials is an effective approach to enhancing their acetone sensing performance. Therefore, designing and preparing cobalt tetroxide materials with excellent gas-sensing properties is an important issue that needs to be solved urgently. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to combine the unique structural advantages of the amorphous / crystalline heterostructure and the doping effect of boron atoms to improve the gas-sensing performance of cobalt tetroxide materials to acetone. An acetone sensor based on boron-doped cobalt tetroxide with an amorphous / crystalline heterostructure, a preparation method, and an application in acetone detection are provided to overcome the problems existing in the background technology.

[0005] The present invention discloses an acetone sensor based on boron-doped cobalt tetroxide with an amorphous / crystalline heterostructure. The sensor comprises an Al2O3 ceramic tube substrate, two parallel and separate annular Au electrodes coated on the outer surface of the Al2O3 ceramic tube substrate, a gas-sensitive film coated on the outer surface of the Al2O3 ceramic tube and on the annular Au electrodes, and a nickel-chromium alloy heating coil passing through the interior of the Al2O3 ceramic tube. The gas-sensitive film is made of boron-doped cobalt tetroxide with an amorphous / crystalline heterostructure, and the preparation steps are as follows:

[0006] (1) Add 1.0-3.0 g of cobalt nitrate powder to 200-300 mL of ethanol and stir at room temperature for 2-3 hours to obtain an aqueous solution of cobalt nitrate;

[0007] (2) adding 0.5-1.0 g of sodium borohydride to 30-50 mL of water and stirring at room temperature for 5-10 minutes to obtain an aqueous solution of sodium borohydride;

[0008] (3) adding the aqueous solution of sodium borohydride obtained in step (2) to the aqueous solution of cobalt nitrate obtained in step (1), stirring at room temperature for 2 to 3 hours, so that an oxidation-reduction reaction occurs between the sodium borohydride and the cobalt nitrate to obtain a dispersion of a solid mixture containing cobalt and boron;

[0009] (4) centrifuging the dispersion of the solid mixture containing cobalt and boron obtained in step (3) to obtain a solid product, washing the solid product with water and ethanol multiple times, placing it in a constant temperature drying oven, and drying it at 50-60° C. for 30-50 minutes to obtain a solid mixture powder containing cobalt and boron;

[0010] (5) calcining the solid mixture powder containing cobalt and boron obtained in step (4) at 250-350° C. for 3-5 hours to obtain the boron-doped cobalt oxide material having an amorphous / crystalline heterostructure.

[0011] The Al2O3 ceramic tube used in the present invention has a length of 3 to 5 mm, an outer diameter of 1.1 to 1.3 mm, and an inner diameter of 0.7 to 0.9 mm. A nickel-chromium alloy heating coil provides operating temperature for the sensor, and the heating coil has a resistance of 30 to 40 Ω. The width of the annular Au electrode is 0.7 to 0.9 mm, the spacing between the two Au electrodes is 1.7 to 1.9 mm, the thickness of the Au electrode is 0.05 to 0.08 mm, and the thickness of the gas-sensitive film is 180 to 220 μm. The resistance of the gas-sensitive film changes before and after contact with the gas to be measured. The sensitivity of the sensor can be obtained by measuring the change in resistance between the two annular Au electrodes. The sensitivity is calculated by dividing the resistance of the two annular Au electrodes in air by their resistance in the target gas.

[0012] The method for preparing a resistive acetone sensor based on boron-doped cobalt tetroxide with an amorphous / crystalline heterostructure according to the present invention comprises the following steps:

[0013] (1) mixing a boron-doped cobalt oxide material having an amorphous / crystalline heterostructure with deionized water in a mass ratio of 3 to 5:1 and grinding the mixture into a paste-like slurry; and coating the paste onto the surface of an Al2O3 ceramic tube having two parallel and separate annular Au electrodes on its outer surface;

[0014] (2) baking the device obtained in step (1) under an infrared lamp for 20 to 40 minutes. After the sensitive material is dried, a nickel-chromium alloy heating coil with a resistance value of 30 to 40 Ω is passed through the interior of the Al2O3 ceramic tube as a heating wire, and welding and packaging are performed according to the indirect heating type gas sensor;

[0015] (3) The device obtained in step (2) is aged at 280-320° C. for 8-12 hours, thereby obtaining the resistive acetone sensor based on boron-doped cobalt tetroxide with an amorphous / crystalline heterostructure.

[0016] The advantages of the present invention are:

[0017] 1) The boron-doped cobalt tetroxide material with an amorphous / crystalline heterostructure of the present invention contains a unique amorphous / crystalline heterostructure, which not only maintains the stable structure of the crystalline material but also takes advantage of the amorphous structure's high degree of electron delocalization and a large number of reaction sites, thereby improving the acetone gas-sensing performance of the cobalt tetroxide material;

[0018] 2) The boron-doped cobalt tetroxide material with an amorphous / crystalline heterostructure in the present invention contains boron atoms. Compared with traditional metal ion dopants, boron atoms, as non-metallic dopants, have high electronegativity and unique electronic structure, which endow cobalt tetroxide with unique structural characteristics;

[0019] 3) The present invention utilizes the gas generated by the reaction of cobalt nitrate and sodium borohydride as a template to hinder the agglomeration of cobalt oxide nanostructures, and the resulting material has a rich porous structure;

[0020] 4) The present invention adopts a method combining solution phase reaction and direct calcination to prepare boron-doped cobalt tetroxide materials with an amorphous / crystalline heterostructure. The preparation method is simple, efficient, and has a high yield, making it suitable for mass production;

[0021] 5) The boron-doped cobalt tetroxide sensor with an amorphous / crystalline heterostructure prepared in the present invention has high sensitivity and a low detection limit for acetone and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the X-ray diffraction pattern of boron-doped cobalt oxide with amorphous / crystalline heterostructure prepared in Example 1;

[0023] Figure 2 1 is a transmission electron microscope photograph of boron-doped cobalt oxide with an amorphous / crystalline heterostructure prepared in Example 1 at different magnifications; Figure 2 The scale bar in (a) is 100 nm. Figure 2 The scale bar in (b) is 5 nm;

[0024] Figure 3 The amorphous / crystalline heterojunction boron-doped cobalt tetroxide O1s prepared in Example 1 ( Figure 3 (a)) and B1s peak ( Figure 3 (b));

[0025] Figure 4 : is the temperature-programmed desorption curve of oxygen for the amorphous / crystalline heterojunction boron-doped cobalt tetroxide prepared in Example 1;

[0026] Figure 5 is a temperature-programmed reduction curve of the amorphous / crystalline heterojunction boron-doped cobalt tetroxide prepared in Example 1 to hydrogen;

[0027] Figure 6 1 is the response recovery curve of the acetone sensor based on amorphous / crystalline heterojunction boron-doped cobalt tetroxide prepared in Example 1 to 100 ppm acetone at 190° C.;

[0028] Figure 7 Response recovery curve of the acetone sensor based on amorphous / crystalline heterojunction boron-doped cobalt tetroxide prepared in Example 1 to 20-140 ppb acetone at 190° C.;

[0029] Figure 8 8 consecutive response recovery curves of the acetone sensor based on amorphous / crystalline heterojunction boron-doped cobalt tetroxide prepared in Example 1 to 100 ppm acetone at 190° C.;

[0030] Figure 9 1 is the response recovery curve of the acetone sensor based on amorphous / crystalline heterojunction boron-doped cobalt tetroxide prepared in Example 2 to 100 ppm acetone at 190° C.;

[0031] Figure 10 3 is the response recovery curve of the acetone sensor based on amorphous / crystalline heterojunction boron-doped cobalt tetroxide prepared in Example 3 to 100 ppm acetone at 190° C.;

[0032] Figure 113 is the response recovery curve of the acetone sensor based on amorphous / crystalline heterojunction boron-doped cobalt tetroxide prepared in Example 4 to 100 ppm acetone at 190° C.;

[0033] The X-ray diffraction pattern of the boron-doped cobalt oxide with amorphous / crystalline heterostructure prepared in Example 1 is as follows: Figure 1 As shown. Different from the standard crystal diffraction peaks of perfect cobalt tetroxide, boron-doped cobalt tetroxide with an amorphous / crystalline heterostructure gives two weaker diffraction peaks at 36.6° and 66.2°. Moreover, the diffraction intensity of the diffraction peaks is low and the spectrum peaks are broad, indicating that the prepared material has poor crystallinity. The reason for this result is the formation of an amorphous / crystalline heterostructure within the material.

[0034] The transmission electron microscope photo of the boron-doped cobalt oxide with amorphous / crystalline heterostructure prepared in Example 1 is as follows: Figure 2 As shown. From the low-power electron microscope photo ( Figure 2 (a)) shows that the boron-doped cobalt oxide with amorphous / crystalline heterostructure is a typical lamellar structure. From the high-magnification transmission electron microscope photo ( Figure 2 (b)) It can be seen that the material is composed of crystalline and amorphous structures, indicating the formation of an amorphous / crystalline heterostructure;

[0035] The O1s and B1s spectra of boron-doped cobalt tetroxide with amorphous / crystalline heterostructure prepared in Example 1 are as follows: Figure 3 As shown, from Figure 3 (a) It can be seen that the oxygen element in the material is composed of lattice oxygen, oxygen vacancies and surface adsorbed oxygen. Due to the existence of amorphous and crystalline heterogeneous structures in the material, the content of oxygen vacancies in the material is relatively high. B 1s spectrum peak ( Figure 3 (b)) shows that the B element is indeed doped into the structure of cobalt trioxide, and the boron element exists in the form of BO bond;

[0036] The temperature-programmed desorption curve of oxygen for the amorphous / crystalline heterojunction boron-doped cobalt tetroxide prepared in Example 1 is as follows: Figure 4 As shown, it can be seen that the material contains three types of oxygen species: adsorbed oxygen, surface vacancy oxygen and lattice oxygen;

[0037] The temperature-programmed reduction curve of the amorphous / crystalline heterojunction boron-doped cobalt tetroxide to hydrogen prepared in Example 1 is as follows: Figure 5 As shown. It can be seen that with the increase of temperature, three reduction peaks can be observed, corresponding to the reduction of Co 3+ To Co 2+ , reducing Co 2+ to Co and reduce B2O3 to B;

[0038] The response recovery transient curve of the acetone gas sensor based on amorphous / crystalline heterojunction boron-doped cobalt tetroxide prepared in Example 1 to 100 ppm acetone at 190°C is shown in FIG. Figure 6 As shown in the figure, it can be seen that the sensor has obvious response characteristics to acetone. By analyzing the ratio of the device's resistance value in acetone to the resistance value in air, it is calculated that the device's response value reaches 106;

[0039] The response recovery transient curve of the acetone gas sensor based on amorphous / crystalline heterojunction boron-doped cobalt tetroxide prepared in Example 1 to 20-140 ppb acetone at 190°C is as follows: Figure 7 As shown in the figure, it can be seen that as the acetone concentration increases, the response value of the sensor gradually increases. The sensor also shows a fast response recovery characteristic to low concentration acetone. The lowest detection concentration of the device is 20ppb.

[0040] The response repeatability curve of the acetone gas sensor based on amorphous / crystalline heterojunction boron-doped cobalt tetroxide prepared in Example 1 to 100 ppm acetone at 190°C is shown in FIG. Figure 8 It can be seen that the amorphous / crystalline heterojunction boron-doped cobalt tetroxide sensor shows a stable and repetitive response when repeatedly exposed to 100 ppm acetone, indicating that the sensor has excellent repeatability;

[0041] The response recovery transient curve of the acetone gas sensor based on amorphous / crystalline heterojunction boron-doped cobalt tetroxide prepared in Example 2 to 100 ppm acetone at 190°C is as follows: Figure 9 As shown. It can be seen that the sensor has good response and recovery characteristics to acetone;

[0042] The response recovery transient curve of the acetone gas sensor based on amorphous / crystalline heterojunction boron-doped cobalt tetroxide prepared in Example 3 to 100 ppm acetone at 190°C is as follows: Figure 10 As shown in the figure, it can be seen that the sensor has good response and recovery characteristics to 100ppm acetone;

[0043] The response recovery transient curve of the acetone gas sensor based on amorphous / crystalline heterojunction boron-doped cobalt tetroxide prepared in Example 4 to 100 ppm acetone at 190°C is shown in FIG. Figure 11 It can be seen that the sensor has good response and recovery characteristics to 100 ppm acetone. DETAILED DESCRIPTION

[0044] The present invention is further described below with reference to the accompanying drawings and examples.

[0045] Example 1

[0046] (1) Add 1.0 g of cobalt nitrate powder to 200 mL of ethanol and stir at room temperature for 3 h to obtain an aqueous solution of cobalt nitrate;

[0047] (2) Add 0.5 g of sodium borohydride to 50 mL of water and stir at room temperature for 5 min to obtain an aqueous solution of sodium borohydride;

[0048] (3) adding the aqueous solution of sodium borohydride obtained in step (2) to the aqueous solution of cobalt nitrate obtained in step (1), stirring at room temperature for 3 hours, so that an oxidation-reduction reaction occurs between the sodium borohydride and the cobalt nitrate to obtain a dispersion of a solid mixture containing cobalt and boron;

[0049] (4) centrifuging the dispersion of the solid mixture containing cobalt and boron obtained in step (3) to obtain a solid product, washing the solid product with water and ethanol multiple times, placing it in a constant temperature drying oven, and drying it at 50° C. for 50 minutes to obtain a solid mixture powder containing cobalt and boron;

[0050] (5) The solid mixture powder containing cobalt and boron obtained in step (4) was calcined at 350° C. for 5 h to obtain a boron-doped cobalt oxide material having an amorphous / crystalline heterostructure, with a product mass of 0.27 g; (6) The cobalt ion-doped cerium dioxide aerogel material prepared in step (5) was mixed with deionized water in a mass ratio of 3:1 and ground into a paste slurry, which was then coated on the surface of an Al2O3 ceramic tube having two parallel, annular and separate gold electrodes on its outer surface. After baking under infrared light for 20 minutes, a 180μm-thick sensitive film based on cobalt ion-doped ceria aerogel was formed on the surface of the ceramic tube. A 30Ω nickel-chromium alloy heating coil was then passed through the Al2O3 ceramic tube as a heating filament, and finally the tube was welded and packaged as a indirectly heated gas sensor. The Al2O3 ceramic tube was 3mm long, with an outer diameter of 1.1mm and an inner diameter of 0.7mm. The annular Au electrode was 0.7mm wide, and the distance between the two electrodes was 1.7mm.

[0051] (7) The acetone gas sensor based on the cobalt ion-doped ceria aerogel material obtained in step (6) is aged at 280° C. for 12 hours to complete the aging treatment of the gas sensor, thereby obtaining a resistive acetone sensor based on the cobalt ion-doped ceria aerogel material.

[0052] Example 2

[0053] (1) Add 1.0 g of cobalt nitrate powder to 200 mL of ethanol and stir at room temperature for 3 h to obtain an aqueous solution of cobalt nitrate;

[0054] (2) Add 1.0 g of sodium borohydride to 40 mL of water and stir at room temperature for 5 min to obtain an aqueous solution of sodium borohydride;

[0055] (3) adding the aqueous solution of sodium borohydride obtained in step (2) to the aqueous solution of cobalt nitrate obtained in step (1), stirring at room temperature for 3 hours, so that an oxidation-reduction reaction occurs between the sodium borohydride and the cobalt nitrate to obtain a dispersion of a solid mixture containing cobalt and boron;

[0056] (4) centrifuging the dispersion of the solid mixture containing cobalt and boron obtained in step (3) to obtain a solid product, washing the solid product with water and ethanol multiple times, placing it in a constant temperature drying oven, and drying it at 50° C. for 50 minutes to obtain a solid mixture powder containing cobalt and boron;

[0057] (5) The solid mixture powder containing cobalt and boron obtained in step (4) was calcined at 350° C. for 3 h to obtain a boron-doped cobalt oxide material having an amorphous / crystalline heterostructure, with a product mass of 0.26 g; (6) The cobalt ion-doped cerium dioxide aerogel material prepared in step (5) was mixed with deionized water in a mass ratio of 3:1 and ground into a paste slurry, which was then coated on the surface of an Al2O3 ceramic tube having two parallel, annular and separate gold electrodes on its outer surface. After baking under infrared light for 20 minutes, a 180μm-thick sensitive film based on cobalt ion-doped ceria aerogel was formed on the surface of the ceramic tube. A 30Ω nickel-chromium alloy heating coil was then passed through the Al2O3 ceramic tube as a heating filament, and finally the tube was welded and packaged as a indirectly heated gas sensor. The Al2O3 ceramic tube was 3mm long, with an outer diameter of 1.1mm and an inner diameter of 0.7mm. The annular Au electrode was 0.7mm wide, and the distance between the two electrodes was 1.7mm.

[0058] (7) The acetone gas sensor based on the cobalt ion-doped ceria aerogel material obtained in step (6) is aged at 280° C. for 12 hours to complete the aging treatment of the gas sensor, thereby obtaining a resistive acetone sensor based on the cobalt ion-doped ceria aerogel material.

[0059] Example 3

[0060] (1) Add 2.0 g of cobalt nitrate powder to 200 mL of ethanol and stir at room temperature for 3 h to obtain an aqueous solution of cobalt nitrate;

[0061] (2) Add 0.5 g of sodium borohydride to 30 mL of water and stir at room temperature for 5 min to obtain an aqueous solution of sodium borohydride;

[0062] (3) adding the aqueous solution of sodium borohydride obtained in step (2) to the aqueous solution of cobalt nitrate obtained in step (1), stirring at room temperature for 3 hours, so that an oxidation-reduction reaction occurs between the sodium borohydride and the cobalt nitrate to obtain a dispersion of a solid mixture containing cobalt and boron;

[0063] (4) centrifuging the dispersion of the solid mixture containing cobalt and boron obtained in step (3) to obtain a solid product, washing the solid product with water and ethanol multiple times, placing it in a constant temperature drying oven, and drying it at 60° C. for 30 minutes to obtain a solid mixture powder containing cobalt and boron;

[0064] (5) The solid mixture powder containing cobalt and boron obtained in step (4) was calcined at 300° C. for 5 h to obtain a boron-doped cobalt oxide material having an amorphous / crystalline heterostructure, with a product mass of 0.50 g; (6) The copper ion-doped cerium dioxide aerogel material prepared in step (5) was mixed with deionized water in a mass ratio of 3:1 and ground into a paste slurry, which was then coated on the surface of an Al2O3 ceramic tube having two parallel, annular and separate gold electrodes on its outer surface. After baking under infrared light for 20 minutes, a 180μm-thick copper-ion-doped ceria aerogel-based sensitive film was formed on the surface of the ceramic tube. A 30Ω nickel-chromium alloy heating coil was then passed through the Al2O3 ceramic tube as a heating filament, and finally the tube was welded and packaged as a indirectly heated gas sensor. The Al2O3 ceramic tube was 3mm long, with an outer diameter of 1.1mm and an inner diameter of 0.7mm. The annular Au electrode was 0.7mm wide, and the distance between the two electrodes was 1.7mm.

[0065] (7) The acetone gas sensor of the copper metal ion-doped ceria aerogel material obtained in step (6) is aged at 280° C. for 12 hours to complete the aging treatment of the gas sensor, thereby obtaining a resistive acetone sensor based on the copper ion-doped ceria aerogel material.

[0066] Example 4

[0067] (1) Add 2.0 g of cobalt nitrate powder to 300 mL of ethanol and stir at room temperature for 2 h to obtain an aqueous solution of cobalt nitrate;

[0068] (2) Add 1.0 g of sodium borohydride to 50 mL of water and stir at room temperature for 10 min to obtain an aqueous solution of sodium borohydride;

[0069] (3) adding the aqueous solution of sodium borohydride obtained in step (2) to the aqueous solution of cobalt nitrate obtained in step (1), stirring at room temperature for 2 hours, so that an oxidation-reduction reaction occurs between the sodium borohydride and the cobalt nitrate to obtain a dispersion of a solid mixture containing cobalt and boron;

[0070] (4) centrifuging the dispersion of the solid mixture containing cobalt and boron obtained in step (3) to obtain a solid product, washing the solid product with water and ethanol multiple times, placing it in a constant temperature drying oven, and drying it at 60° C. for 30 minutes to obtain a solid mixture powder containing cobalt and boron;

[0071] (5) The solid mixture powder containing cobalt and boron obtained in step (4) was calcined at 300° C. for 3 h to obtain a boron-doped cobalt oxide material having an amorphous / crystalline heterostructure, with a product mass of 0.54 g; (6) The copper ion-doped cerium dioxide aerogel material prepared in step (5) was mixed with deionized water in a mass ratio of 3:1 and ground into a paste slurry, which was then coated on the surface of an Al2O3 ceramic tube having two parallel, annular and separate gold electrodes on its outer surface. After baking under infrared light for 20 minutes, a 180μm-thick copper-ion-doped ceria aerogel-based sensitive film was formed on the surface of the ceramic tube. A 30Ω nickel-chromium alloy heating coil was then passed through the Al2O3 ceramic tube as a heating filament, and finally the tube was welded and packaged as a indirectly heated gas sensor. The Al2O3 ceramic tube was 3mm long, with an outer diameter of 1.1mm and an inner diameter of 0.7mm. The annular Au electrode was 0.7mm wide, and the distance between the two electrodes was 1.7mm.

[0072] (7) The acetone gas sensor of the copper metal ion-doped ceria aerogel material obtained in step (6) is aged at 280° C. for 12 hours to complete the aging treatment of the gas sensor, thereby obtaining a resistive acetone sensor based on the copper ion-doped ceria aerogel material.

[0073] Example 5

[0074] (1) Add 3.0 g of cobalt nitrate powder to 300 mL of ethanol and stir at room temperature for 2 h to obtain an aqueous solution of cobalt nitrate;

[0075] (2) Add 0.5 g of sodium borohydride to 40 mL of water and stir at room temperature for 10 min to obtain an aqueous solution of sodium borohydride;

[0076] (3) adding the aqueous solution of sodium borohydride obtained in step (2) to the aqueous solution of cobalt nitrate obtained in step (1), stirring at room temperature for 2 hours, so that an oxidation-reduction reaction occurs between the sodium borohydride and the cobalt nitrate to obtain a dispersion of a solid mixture containing cobalt and boron;

[0077] (4) centrifuging the dispersion of the solid mixture containing cobalt and boron obtained in step (3) to obtain a solid product, washing the solid product with water and ethanol multiple times, placing it in a constant temperature drying oven, and drying it at 50° C. for 40 minutes to obtain a solid mixture powder containing cobalt and boron;

[0078] (5) The solid mixture powder containing cobalt and boron obtained in step (4) was calcined at 250° C. for 5 h to obtain a boron-doped cobalt oxide material having an amorphous / crystalline heterostructure, with a product mass of 0.79 g; (6) The manganese ion-doped cerium dioxide aerogel material prepared in step (5) was mixed with deionized water in a mass ratio of 3:1 and ground into a paste slurry, which was then coated on the surface of an Al2O3 ceramic tube having two parallel, annular and separate gold electrodes on its outer surface. After baking under infrared light for 20 minutes, a sensitive film based on manganese ion-doped ceria aerogel was formed on the surface of the ceramic tube. The thickness of the sensitive film was 180 μm. A nickel-chromium alloy heating coil with a resistance of 30 Ω was then passed through the Al2O3 ceramic tube as a heating filament. Finally, the tube was welded and packaged as a indirectly heated gas sensor. The Al2O3 ceramic tube was 3 mm long, with an outer diameter of 1.1 mm and an inner diameter of 0.7 mm. The width of the annular Au electrode was 0.7 mm, and the distance between the two electrodes was 1.7 mm.

[0079] (7) The acetone gas sensor based on the manganese ion-doped ceria aerogel material obtained in step (6) is aged at 280° C. for 12 hours to complete the aging treatment of the gas sensor, thereby obtaining a resistive acetone sensor based on the manganese ion-doped ceria aerogel material.

[0080] Example 6

[0081] (1) Add 3.0 g of cobalt nitrate powder to 300 mL of ethanol and stir at room temperature for 2 h to obtain an aqueous solution of cobalt nitrate;

[0082] (2) Add 1.0 g of sodium borohydride to 30 mL of water and stir at room temperature for 10 min to obtain an aqueous solution of sodium borohydride;

[0083] (3) adding the aqueous solution of sodium borohydride obtained in step (2) to the aqueous solution of cobalt nitrate obtained in step (1), stirring at room temperature for 2 hours, so that an oxidation-reduction reaction occurs between the sodium borohydride and the cobalt nitrate to obtain a dispersion of a solid mixture containing cobalt and boron;

[0084] (4) centrifuging the dispersion of the solid mixture containing cobalt and boron obtained in step (3) to obtain a solid product, washing the solid product with water and ethanol multiple times, placing it in a constant temperature drying oven, and drying it at 60° C. for 40 minutes to obtain a solid mixture powder containing cobalt and boron;

[0085] (5) The solid mixture powder containing cobalt and boron obtained in step (4) was calcined at 250° C. for 3 h to obtain a boron-doped cobalt oxide material having an amorphous / crystalline heterostructure, with a product mass of 0.80 g; (6) The manganese ion-doped cerium dioxide aerogel material prepared in step (5) was mixed with deionized water in a mass ratio of 3:1 and ground into a paste slurry, which was then coated on the surface of an Al2O3 ceramic tube having two parallel, annular and separate gold electrodes on its outer surface. After baking under infrared light for 20 minutes, a sensitive film based on manganese ion-doped ceria aerogel was formed on the surface of the ceramic tube. The thickness of the sensitive film was 180 μm. A nickel-chromium alloy heating coil with a resistance of 30 Ω was then passed through the Al2O3 ceramic tube as a heating filament. Finally, the tube was welded and packaged as a indirectly heated gas sensor. The Al2O3 ceramic tube was 3 mm long, with an outer diameter of 1.1 mm and an inner diameter of 0.7 mm. The width of the annular Au electrode was 0.7 mm, and the distance between the two electrodes was 1.7 mm.

[0086] (7) The acetone gas sensor based on the manganese ion-doped ceria aerogel material obtained in step (6) is aged at 280° C. for 12 hours to complete the aging treatment of the gas sensor, thereby obtaining a resistive acetone sensor based on the manganese ion-doped ceria aerogel material.

Claims

1. An acetone sensor based on boron-doped cobalt tetroxide with an amorphous / crystalline heterostructure, comprising an Al2O3 ceramic tube substrate, two parallel and separate annular Au electrodes coated on the outer surface of the Al2O3 ceramic tube substrate, a gas-sensitive film coated on the outer surface of the Al2O3 ceramic tube and the annular Au electrodes, and a nickel-chromium alloy heating coil extending through the interior of the Al2O3 ceramic tube; characterized in that: The material of the gas sensitive film is boron-doped cobalt tetroxide with an amorphous / crystalline heterostructure. The preparation steps are as follows: (1) Add 1.0-3.0 g of cobalt nitrate powder to 200-300 mL of ethanol and stir at room temperature for 2-3 h to obtain an ethanol solution of cobalt nitrate; (2) Add 0.5-1.0 g of sodium borohydride to 30-50 mL of water and stir at room temperature for 5-10 min to obtain an aqueous solution of sodium borohydride; (3) adding the aqueous solution of sodium borohydride obtained in step (2) to the ethanol solution of cobalt nitrate obtained in step (1), stirring at room temperature for 2 to 3 hours, so that an oxidation-reduction reaction occurs between the sodium borohydride and the cobalt nitrate to obtain a dispersion of a solid mixture containing cobalt and boron; (4) The dispersion of the solid mixture containing cobalt and boron obtained in step (3) is centrifuged to obtain a solid product, and the solid product is washed with water and ethanol several times and placed in a constant temperature drying oven for drying at 50-60°C for 30-50 minutes to obtain a solid mixture powder containing cobalt and boron; (5) The solid mixture powder containing cobalt and boron obtained in step (4) is calcined at 250-350° C. for 3-5 h to obtain the boron-doped cobalt oxide material having an amorphous / crystalline heterostructure.

2. The acetone sensor based on boron-doped cobalt tetroxide with an amorphous / crystalline heterostructure according to claim 1, characterized in that: The Al2O3 ceramic tube has a length of 3-5 mm, an outer diameter of 1.1-1.3 mm, and an inner diameter of 0.7-0.9 mm. The nickel-chromium alloy heating coil provides the operating temperature for the sensor, and the resistance of the heating coil is 30-40 Ω. The width of the annular Au electrode is 0.7-0.9 mm, the distance between the two Au electrodes is 1.7-1.9 mm, and the thickness of the Au electrode is 0.05-0.08 mm.

3. The acetone sensor based on boron-doped cobalt tetroxide with an amorphous / crystalline heterostructure according to claim 1, characterized in that: The thickness of the gas sensitive film is 180~220 μm.

4. A method for preparing an acetone sensor based on boron-doped cobalt tetroxide having an amorphous / crystalline heterostructure according to any one of claims 1 to 3, comprising the following steps: (1) A boron-doped cobalt oxide material with an amorphous / crystalline heterostructure is mixed with deionized water in a mass ratio of 3 to 5:1 and ground into a paste slurry; the paste is coated on the surface of an Al2O3 ceramic tube with two parallel and separate ring-shaped Au electrodes on the outer surface; (2) Bake the device obtained in step (1) under an infrared lamp for 20 to 40 minutes. After the sensitive material is dried, pass a nickel-chromium alloy heating coil with a resistance value of 30 to 40 Ω through the interior of the Al2O3 ceramic tube as a heating wire, and weld and package it according to the indirect heating type gas sensor; (3) The device obtained in step (2) is aged at 280-320° C. for 8-12 h, thereby obtaining the resistive acetone sensor based on boron-doped cobalt tetroxide with an amorphous / crystalline heterostructure.

5. Use of an acetone sensor based on boron-doped cobalt tetroxide having an amorphous / crystalline heterostructure according to any one of claims 1 to 3 in acetone detection.

Images