A preparation method of acetone gas sensor based on rGO / V2O5 composite material

Abstract

A method for fabricating an acetone gas sensor based on rGO / V₂O₅ composite material is disclosed. This invention utilizes a simple one-step hydrothermal method, employing readily available and inexpensive ammonium metavanadate, polyvinylpyrrolidone, citric acid, and GO as reactants. Flower-like microsphere structured rGO / V₂O₅ composite material is prepared by selecting appropriate process parameters. The prepared composite material has a size of 1-3 μm, is self-assembled from nanosheets, exhibits good dispersibility, and has numerous pores on its surface. The flower-like microsphere structured rGO / V₂O₅ composite material is used to fabricate a gas sensor. The resulting rGO / V₂O₅-based acetone gas sensor is simple to fabricate and small in size. Due to its unique three-dimensional spatial structure, it exhibits high sensitivity, good selectivity, and long-term stability for acetone gas at relatively low operating temperatures.

Description

Technical Field

[0001] The present invention relates to a method for preparing a gas sensor, in particular to a method for preparing a gas sensor based on rGO / V 2 O 5 Preparation method of composite material acetone gas sensor. Background Art

[0002] With the rapid development of industrial technology, a large number of harmful gases (including acetone, NO 2 , benzene and toluene) are released into the atmosphere, which can cause serious environmental problems and human diseases. As a good organic solvent, acetone is widely used in laboratories and industrial production workshops. It is also a common raw material for synthesizing a variety of organic substances. Due to its active chemical properties, acetone is very volatile at room temperature. Long-term or high-dose exposure to acetone can anesthetize the central nervous system and even cause death. In addition, acetone in exhaled breath is also considered a biomarker for diabetes. Therefore, accurate and rapid detection of acetone is of great significance for industrial safety production and human health.

[0003] At present, the main methods for monitoring acetone gas include gas chromatography, colorimetry and metal oxide semiconductor sensor. Among them, metal oxide semiconductor (MOS) gas sensors have attracted much attention due to their low cost, high stability and controllable preparation. 2 O 5 As an important n-type semiconductor, it has a unique layered structure and good thermal stability and has been widely studied in the field of gas sensing in recent years. In particular, three-dimensional V 2 O 5 The hierarchical structure has potential applications as a sensitive material due to its high specific surface area and porous structure. 2 O 5 In practical applications, gas sensors still have the problem of high operating temperature and poor gas sensing performance. Therefore, it is necessary to design a V sensor that can work effectively at a lower operating temperature. 2 O 5 Gas sensors, studying their sensitivity to volatile organic compounds such as acetone has important commercial value. Summary of the invention

[0004] The purpose of the present invention is to provide a method based on rGO / V 2 O 5 The present invention adopts a simple one-step hydrothermal synthesis method to prepare a flower-like microsphere structure rGO / V 2 O 5The composite material is used as a gas sensitive material in gas sensors, which can achieve selective detection of acetone gas at a lower operating temperature. It overcomes the problems of high operating temperature and low selectivity of existing gas sensors, is used to detect acetone, has low cost, high product purity, and is suitable for large-scale industrial applications.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A rGO / V-based 2 O 5 A method for preparing a composite material acetone gas sensor, the method comprising the following preparation steps:

[0007] (1) Weigh graphene oxide (GO) and dissolve it in 15 mL of distilled water, and continue ultrasonication for 3 hours to obtain aqueous solution A; weigh ammonium metavanadate and polyvinyl pyrrolidone and continue magnetic stirring for 1 hour in 20 mL of distilled water to obtain aqueous solution B; then mix aqueous solution A and aqueous solution B and stir for 1 hour to prepare a stable suspension; then dissolve citric acid in 5 mL of distilled water to obtain a citric acid solution, add it dropwise to the above mixed solution under stirring, and continue to stir for 30 minutes to prepare a hydrothermal synthesis precursor reaction solution;

[0008] (2) The hydrothermal synthesis precursor reaction solution was transferred into a 50 mL polytetrafluoroethylene-lined stainless steel autoclave with a filling degree of 80% sealed; the reaction solution was kept at 180°C for 12 hours, and then naturally cooled to room temperature to obtain a reaction product;

[0009] (3) The reaction solution was centrifuged to obtain a black reaction product, and then the product was washed alternately with distilled water and anhydrous ethanol for 6 times;

[0010] (4) placing the washed black reaction product in a constant temperature drying oven at 60°C for 12 hours, and cooling after drying;

[0011] (5) The dried black product was placed in a clean crucible and placed in a muffle furnace. It was calcined at 350 °C under nitrogen protection for 2 hours to obtain flower-like microsphere structure rGO / V 2 O 5 The composite material is stored in a desiccator until analytical testing;

[0012] (6) Take flower-like microsphere structure rGO / V 2 O 5 The composite material was mixed with an ethanol solution to form a paste, which was coated on an alumina substrate equipped with a pair of interdigitated gold electrodes and four platinum wires;

[0013] (7) Welding four platinum wires to the bases of four probes to obtain a gas sensor element;

[0014] (8) Placing the prepared components on a desktop gas sensor aging table for aging;

[0015] (9) WS-30A gas sensor tester, used to test the gas sensitivity characteristics of the sensor.

[0016] The rGO / V 2 O 5 The preparation method of the composite material acetone gas sensor comprises aging on the aging table at 200° C. for 2 days.

[0017] The rGO / V 2 O 5 The invention discloses a method for preparing a composite material acetone gas sensor. The gas sensitivity characteristic of the sensor is tested at a test temperature of 50-350°C.

[0018] The advantages and effects of the present invention are:

[0019] 1. The present invention uses a simple one-step hydrothermal method, cheap and readily available ammonium metavanadate, polyvinyl pyrrolidone, citric acid and GO as reaction materials, and selects appropriate process parameters to prepare flower-like microsphere structure rGO / V 2 O 5 Composite material. The prepared composite material has a size of 1~3 μm, which is self-assembled by nanosheets, has good dispersion, and has a large number of pores on the powder surface. 2 O 5 The composite material was prepared into a gas sensor, and the obtained rGO / V 2 O 5 The acetone gas sensor has a simple device process and a small size. Due to its unique three-dimensional spatial structure, it exhibits high sensitivity, good selectivity and long-term stability to acetone gas at a lower operating temperature.

[0020] 2. Flower-like microsphere structure rGO / V prepared by the present invention 2 O 5 Composite materials can effectively promote gas transmission and diffusion due to their unique three-dimensional spatial structure and large specific surface area. Gas sensors prepared as gas-sensitive materials show fast response-recovery speed, high sensitivity, good selectivity and long-term stability to acetone gas at relatively low working temperature, and have broad application prospects in the detection of organic volatile gases. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Is the XRD spectrum of the product of the present invention;

[0022] FIG2( a) is a scanning electron microscope image of the product prepared in Example 1 of the present invention;

[0023] FIG2( b ) is a scanning electron microscope image of the product prepared in Example 1 of the present invention;

[0024] FIG2( c ) is a scanning electron microscope image of the product prepared in Example 2 of the present invention;

[0025] FIG2( d ) is a scanning electron microscope image of the product prepared in Example 2 of the present invention;

[0026] FIG2( e ) is a scanning electron microscope image of the product prepared in Example 3 of the present invention;

[0027] FIG2( f) is a scanning electron microscope image of the product prepared in Example 3 of the present invention;

[0028] FIG2( g) is a scanning electron microscope image of the product prepared in Example 4 of the present invention;

[0029] FIG2(h) is a scanning electron microscope image of the product prepared in Example 4 of the present invention;

[0030] FIG3( a ) is a schematic diagram of the structure of an acetone gas sensor according to the present invention;

[0031] FIG3( b ) is a curve showing the relationship between the sensitivity of the gas sensor of the present invention to 5 ppm acetone gas and the operating temperature;

[0032] FIG3( c ) is a real-time sensitivity curve of the gas sensor of the present invention to acetone gas of different concentrations at 100° C.;

[0033] FIG3( d ) is an acetone gas concentration-sensitivity characteristic curve of the gas sensor of the present invention at 100° C.;

[0034] FIG3( e ) is a comparison diagram of the sensitivity of the gas sensor of the present invention to 6 different gases at 5 ppm at 100° C.;

[0035] FIG3( f ) is a long-term stability curve of the sensitivity of the gas sensor of the present invention in 5 ppm acetone gas at 100° C. DETAILED DESCRIPTION

[0036] The present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.

[0037] Flower-like microsphere structure rGO / V 2 O 5 The method for preparing a composite material comprises the following steps:

[0038] Step 1: Weigh an appropriate amount of GO and dissolve it in 15 mL of distilled water. Continue ultrasonication for 3 hours to obtain aqueous solution A. Weigh an appropriate amount of ammonium metavanadate and polyvinyl pyrrolidone and continue magnetic stirring for 1 hour in 20 mL of distilled water to obtain aqueous solution B. Then mix aqueous solution A and aqueous solution B and stir for 1 hour to prepare a stable suspension. Then dissolve an appropriate amount of citric acid in 5 mL of distilled water to obtain a citric acid solution, add it dropwise to the above mixed solution under stirring, continue to stir fully for 30 minutes, and prepare a hydrothermal synthesis precursor reaction solution;

[0039] Step 2: The hydrothermal synthesis precursor reaction solution of step 1 is transferred into a 50 mL polytetrafluoroethylene-lined stainless steel autoclave with a filling degree of 80% sealed; maintained at 180° C. for 12 hours, and then naturally cooled to room temperature to obtain a reaction product;

[0040] Step 3: Centrifuge the solution after the reaction in step 2 to obtain a black reaction product, and then wash it alternately with distilled water and anhydrous ethanol for 6 times;

[0041] Step 4: Place the black reaction product after washing in step 3 into a constant temperature drying oven, dry it at 60°C for 12 hours, and cool it after drying;

[0042] Step 5: Place the black product dried in step 4 into a clean crucible and place it in a muffle furnace, and calcine it at 350°C under nitrogen protection for 2 hours to obtain flower-like microsphere structure rGO / V 2 O 5 The composite material was stored in a desiccator until further analysis.

[0043] The present invention utilizes flower-like microsphere structure rGO / V 2 O 5 Steps for preparing gas sensors from composite materials:

[0044] Step 1: Add appropriate amount of flower-like microsphere structure rGO / V 2 O 5 The composite material was mixed with a small amount of ethanol solution to form a paste, which was coated on an alumina substrate equipped with a pair of interdigitated gold electrodes and four platinum wires;

[0045] Step 2: Weld four platinum wires onto the bases of four probes to obtain a gas sensor element;

[0046] Step 3: Place the prepared component on a desktop gas sensor aging table and age it at 200°C for 2 days;

[0047] Step 4: Use WS-30A gas sensor tester to test the gas sensitivity of the sensor. The test temperature is 50-350℃.

[0048] Example 1

[0049] (1) Preparation of flower-like microsphere structure V 2 O 5 Material

[0050] Step 1: Weigh 0.117 g of ammonium metavanadate and 0.1125 g of polyvinyl pyrrolidone and dissolve them in 35 mL of distilled water and stir them magnetically for 1 hour. Then, dissolve 0.3150 g of citric acid in 5 mL of distilled water to obtain a citric acid solution, add it dropwise to the above solution under stirring, and continue to stir well for 30 minutes to prepare a hydrothermal synthesis precursor reaction solution;

[0051] Step 2: The hydrothermal synthesis precursor reaction solution of step 1 is transferred into a 50 mL polytetrafluoroethylene-lined stainless steel autoclave with a filling degree of 80% sealed; maintained at 180° C. for 12 hours, and then naturally cooled to room temperature to obtain a reaction product;

[0052] Step 3: Centrifuge the solution after the reaction in step 2 to obtain a black reaction product, and then wash it alternately with distilled water and anhydrous ethanol for 6 times;

[0053] Step 4: Place the black reaction product after washing in step 3 into a constant temperature drying oven, dry it at 60°C for 12 hours, and cool it after drying;

[0054] Step 5: Store the black product after drying in step 4 in a desiccator for analysis and testing.

[0055] (2) Flower-like microsphere structure V 2 O 5 Structural characterization of materials

[0056] The crystal structure of the product was characterized by XRD powder diffractometer (XRD, PANalytical X'Pert Pro). Figure 1 The XRD spectrum of the product shows that pure V 2 O 5 The diffraction peaks of the product are strong and sharp, and there are no other impurity peaks, indicating that it has high purity and good crystallinity. The diffraction peaks are consistent with NO.41-1426 in the standard PDF card, indicating that the sample is rhombohedral V 2 O 5 .

[0057] The product morphology was characterized by scanning electron microscopy (FESEM, ZEISS Ultra Plus). As shown in Figure 2 (ab), the product showed a flower-like microsphere structure with a size of 1 to 3 μm, relatively uniform dispersion, and a large number of pores on the surface of the powder, which greatly improved the detection of acetone gas.

[0058] Example 2

[0059] (1) Preparation of flower-like microsphere structure rGO / V 2 O 5 Composite Materials

[0060] Step 1: Weigh 0.003 g GO and dissolve it in 15 mL distilled water. Continue ultrasonication for 3 hours to obtain aqueous solution A. Weigh 0.1170 g ammonium metavanadate and 0.1125 g polyvinyl pyrrolidone and stir magnetically in 20 mL distilled water for 1 hour to obtain aqueous solution B. Then mix aqueous solution A and aqueous solution B and stir for 1 hour to prepare a stable suspension. Then dissolve 0.3150 g citric acid in 5 mL distilled water to obtain a citric acid solution, add it dropwise to the above mixed solution under stirring, continue to stir well for 30 minutes, and prepare a hydrothermal synthesis precursor reaction solution;

[0061] Step 2: The hydrothermal synthesis precursor reaction solution of step 1 is transferred into a 50 mL polytetrafluoroethylene-lined stainless steel autoclave with a filling degree of 80% sealed; maintained at 180° C. for 12 hours, and then naturally cooled to room temperature to obtain a reaction product;

[0062] Step 3: Centrifuge the solution after the reaction in step 2 to obtain a black reaction product, and then wash it alternately with distilled water and anhydrous ethanol for 6 times;

[0063] Step 4: Place the black reaction product after washing in step 3 into a constant temperature drying oven, dry it at 60°C for 12 hours, and cool it after drying;

[0064] Step 5: Place the black product dried in step 4 into a clean crucible and place it in a muffle furnace, and calcine it at 350°C under nitrogen protection for 2 hours to obtain flower-like microsphere structure rGO / V 2 O 5 The composite material was stored in a desiccator until further analysis.

[0065] (2) Flower-like microsphere structure rGO / V 2 O 5 Structural characterization of composite materials

[0066] The crystal structure of the product was characterized by XRD powder diffractometer (XRD, PANalytical X'Pert Pro). Figure 1 The XRD spectrum of the product shows that the main diffraction peak is 2 O 5 Consistent with V 2 O 5The barrier effect of the microspheres and the relatively low content of rGO result in the absence of diffraction peaks of rGO. All diffraction peaks are strong and sharp, with no other impurity peaks, indicating high purity and good crystallinity.

[0067] The morphology of the product was characterized by scanning electron microscopy (FESEM, ZEISS Ultra Plus). As shown in Figure 2 (cd), the product still presents a flower-like microsphere structure, which is tightly attached to the surface of the wrinkled and curled rGO nanosheets.

[0068] Example 3

[0069] (1) Preparation of flower-like microsphere structure rGO / V 2 O 5 Composite Materials

[0070] Step 1: Weigh 0.006 g GO and dissolve it in 15 mL distilled water. Continue ultrasonication for 3 hours to obtain aqueous solution A. Weigh 0.1170 g ammonium metavanadate and 0.1125 g polyvinyl pyrrolidone and stir magnetically in 20 mL distilled water for 1 hour to obtain aqueous solution B. Then mix aqueous solution A and aqueous solution B and stir for 1 hour to prepare a stable suspension. Then dissolve 0.3150 g citric acid in 5 mL distilled water to obtain a citric acid solution, add it dropwise to the above mixed solution under stirring, continue to stir fully for 30 minutes, and prepare a hydrothermal synthesis precursor reaction solution;

[0071] Steps 2, 3, 4 and 5 are the same as those in Example 2.

[0072] (2) Flower-like microsphere structure rGO / V 2 O 5 Structural characterization of composite materials

[0073] The crystal structure of the product was characterized by XRD powder diffractometer (XRD, PANalytical X'Pert Pro). Figure 1 The XRD spectrum of the product shows that the main diffraction peak is 2 O 5 The phases are still consistent, and due to the relatively low content of rGO, the rGO diffraction peak is still not displayed. The intensity of all diffraction peaks is slightly weakened, and no other impurity peaks appear.

[0074] The product morphology was characterized by scanning electron microscopy (FESEM, ZEISS Ultra Plus). As shown in Figure 2(ef), V 2 O 5 The product still presents a flower-like microsphere structure, which is tightly attached to the surface of rGO nanosheets. The content of rGO nanosheets increases, presenting a clean and transparent wrinkled shape.

[0075] Example 4

[0076] (1) Preparation of flower-like microsphere structure rGO / V 2 O 5 Composite Materials

[0077] Step 1: Weigh 0.012 g GO and dissolve it in 15 mL distilled water. Continue ultrasonication for 3 hours to obtain aqueous solution A. Weigh 0.1170 g ammonium metavanadate and 0.1125 g polyvinyl pyrrolidone and stir magnetically in 20 mL distilled water for 1 hour to obtain aqueous solution B. Then mix aqueous solution A and aqueous solution B and stir for 1 hour to prepare a stable suspension. Then dissolve 0.3150 g citric acid in 5 mL distilled water to obtain a citric acid solution, add it dropwise to the above mixed solution under stirring, continue to stir well for 30 minutes, and prepare a hydrothermal synthesis precursor reaction solution;

[0078] Steps 2, 3, 4 and 5 are the same as those in Example 2.

[0079] (2) Flower-like microsphere structure rGO / V 2 O 5 Structural characterization of composite materials

[0080] The crystal structure of the product was characterized by XRD powder diffractometer (XRD, PANalytical X'Pert Pro). Figure 1 The XRD spectrum of the product shows that V 2 O 5 The diffraction peaks become weaker and the characteristic peaks of rGO are still not shown.

[0081] The morphology of the product was characterized by scanning electron microscopy (FESEM, ZEISS Ultra Plus). As shown in Figure 2 (gh), the product still showed a flower-like microsphere structure, the layers of the flower-like microspheres became tight and connected, the surface of the microspheres became blurred and agglomerated, the content of rGO nanosheets increased, and some nanosheets were stacked to a certain extent.

[0082] The flower-like microsphere structure rGO / V 2 O 5 The composite material product was made into a gas sensor, and the gas-sensing performance of acetone gas was tested:

[0083] A certain amount of flower-like microsphere structure rGO / V 2 O 5 The composite material is mixed with a small amount of ethanol solution to form a paste, which is then coated on an alumina substrate equipped with a pair of interdigitated gold electrodes and four platinum wires. The four platinum wires are welded to the bases of four probes to obtain a gas sensor element, as shown in FIG3( a ).

[0084] The relationship curve between the sensitivity of the gas sensor to 5 ppm acetone gas and the working temperature is shown in Figure 3(b). It can be seen from the figure that between the test temperature of 50-350°C, the sensitivity of all gas sensors shows a trend of "first rising and then falling", showing the typical characteristics of semiconductor gas sensors. Among them, Example 1 reaches a maximum sensitivity of 2.17 at the optimal working temperature of 300°C, Example 2 reaches a maximum sensitivity of 3.01 at the optimal working temperature of 100°C, Example 3 reaches a maximum sensitivity of 3.87 at the optimal working temperature of 100°C, and Example 4 reaches a maximum sensitivity of 2.17 at the optimal working temperature of 100°C. By comparison, it can be found that Example 3 exhibits the best gas-sensitive characteristics. Figure 3(c) is the response-recovery curve of the gas sensor of Example 3 to 1-100 ppm acetone gas at the optimal working temperature of 100°C. It can be obtained that when the environmental component of the sensor changes from air to acetone gas, the resistance of the sensor drops rapidly. As the concentration of acetone gas increases, the sensor's drop amplitude also increases, that is, as the concentration of acetone gas increases, the sensitivity also increases, as shown in Figure 3(d). Figure 3(e) is a sensitivity comparison diagram of Example 3 at the optimal working temperature of 100°C for 6 different gases at 5 ppm. It can be seen from the figure that the sensitivity of Example 3 to acetone gas is much higher than that of toluene, benzene, methanol, trimethylamine and ethanol, showing good selectivity. Figure 3(f) is a long-term stability test of Example 3 at the optimal working temperature of 100°C for 5 ppm acetone. It can be seen that there is no obvious decline in sensitivity within the 60 days tested, indicating that Example 3 has good long-term stability.

Claims

1. A method for preparing an acetone gas sensor based on rGO / V2O5 composite material, characterized in that: The method comprises the following preparation steps: (1) Weighing graphene oxide and dissolving it in 15 mL of distilled water, and then continuously ultrasonicating for 3 hours to obtain aqueous solution A; weighing ammonium metavanadate and polyvinyl pyrrolidone and continuously magnetically stirring them in 20 mL of distilled water for 1 hour to obtain aqueous solution B; then mixing aqueous solution A and aqueous solution B and stirring them for 1 hour to prepare a stable suspension; then dissolving citric acid in 5 mL of distilled water to obtain a citric acid solution, and adding it dropwise to the mixed solution of aqueous solution A and aqueous solution B under stirring, and continuing to stir them for 30 minutes to prepare a hydrothermal synthesis precursor reaction solution; (2) The hydrothermal synthesis precursor reaction solution was transferred into a 50 mL polytetrafluoroethylene-lined stainless steel autoclave with a filling degree of 80% sealed; the reaction solution was kept at 180°C for 12 hours, and then naturally cooled to room temperature to obtain a reaction product; (3) The reaction solution was centrifuged to obtain a black reaction product, and then the product was washed alternately with distilled water and anhydrous ethanol for 6 times; (4) placing the washed black reaction product in a constant temperature drying oven at 60°C for 12 hours, and cooling after drying; (5) The dried black product was placed in a clean crucible in a muffle furnace and calcined at 350 °C for 2 hours under nitrogen protection to obtain a flower-like microsphere structured rGO / V2O5 composite material, which was stored in a desiccator for analysis and testing; (6) Mix the flower-like microsphere structured rGO / V2O5 composite material with an ethanol solution to form a paste, and coat it on an alumina substrate equipped with a pair of interdigitated gold electrodes and four platinum wires; (7) Welding four platinum wires to the bases of four probes to obtain a gas sensor element; (8) Placing the prepared components on a desktop gas sensor aging table for aging; (9) WS-30A gas sensor tester, used to test the gas sensitivity characteristics of the sensor.

2. The method for preparing an acetone gas sensor based on rGO / V2O5 composite material according to claim 1, characterized in that: The aging was carried out on the aging table at 200° C. for 2 days.

3. The method for preparing an acetone gas sensor based on rGO / V2O5 composite material according to claim 1, characterized in that: The gas sensitivity characteristic of the test sensor is tested at a temperature of 50-350°C.

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