Triethylamine gas sensor based on Bi2MoO6 / Bi2O3 nano-sensitive material and preparation method thereof

Abstract

The present invention relates to a triethylamine gas sensor based on Bi2MoO6 / Bi2O3 nanosensitive materials and a preparation method thereof, belonging to the technical field of semiconductor oxide gas sensors. The sensor comprises an Al2O3 ceramic tube substrate with two parallel, annular, and separate gold electrodes on its outer surface; a nanosensitive material coated on the outer surface of the Al2O3 ceramic tube and on the gold electrodes; and a nickel-cadmium heating coil placed within the Al2O3 ceramic tube. Each gold electrode is connected to two platinum wires. Advantages of the sensor include: by regulating the sintering temperature of the sensitive material, the sensitive material can acquire a micro-nanostructure conducive to chemical reactions with gases, while also achieving high chemical activity, thereby enhancing the sensor's sensitivity. The Bi2MoO6 / Bi2O3 nanosensitive material has a simple synthesis method, high repeatability, and low cost; the device process is simple, compact, and suitable for mass production; and the response time is extremely short, providing an effective sensitive material for the development of high-performance triethylamine sensors.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor oxide gas sensors, and in particular relates to a triethylamine gas sensor based on Bi2MoO6 / Bi2O3 nano-sensitive materials and a preparation method thereof. Background Art

[0002] Due to the rapid development of industry, environmental issues are becoming increasingly prominent, with various toxic and harmful gases posing a serious threat to human health. Triethylamine is a colorless, transparent, oily liquid with a strong ammoniacal odor. It is widely used as an organic solvent, preservative, catalyst, and synthetic dye. However, triethylamine is flammable and explosive, and prolonged exposure to it can cause burning sensations in the eyes and skin, breathing difficulties, and nausea, seriously endangering human health and life safety. Therefore, the development of a gas sensor for triethylamine gas detection is of great significance. To date, methods for detecting triethylamine include ion mobility spectrometry, electrochemical analysis, and colorimetry. However, these methods require high-cost detection equipment and complex detection processes. Therefore, it is highly desirable to develop a gas sensor that is low-cost, simple to manufacture, and has a fast detection speed.

[0003] Oxide semiconductor-based gas sensors have the advantages of low cost, high sensitivity, fast response recovery, and good selectivity, and are suitable for the rapid detection of triethylamine. Some existing oxide-based triethylamine gas sensors have the disadvantage of slow response recovery. Bismuth molybdate is a typical perovskite-type oxide semiconductor. Its good photocatalytic properties and non-toxicity have made it widely used in the field of photocatalysis. However, research on bismuth molybdate in the field of gas sensors is rare. Some existing bismuth molybdate-based gas sensors have certain limitations in the types of target gases they can detect. The only target gases that have been reported are hydrogen sulfide, ethanol, NO, and other gases, and they have problems such as low sensitivity and poor response recovery characteristics. Summary of the Invention

[0004] The present invention provides a triethylamine gas sensor based on Bi2MoO6 / Bi2O3 nano-sensitive material and a preparation method thereof, so as to realize rapid and effective identification of triethylamine and improve the sensitivity of the sensor to triethylamine.

[0005] The technical solution adopted by the present invention is that its structure is a indirectly heated structure, which consists of an Al2O3 ceramic tube substrate with two parallel, annular and separate gold electrodes on the outer surface, a nano-sensitive material coated on the outer surface of the Al2O3 ceramic tube and the gold electrodes, and a nickel-cadmium heating coil placed in the Al2O3 ceramic tube. Each gold electrode is connected to two platinum wires. The nano-sensitive material is a Bi2MoO6 / Bi2O3 nanomaterial. Its preparation steps are as follows:

[0006] (1) Add 2-3 mmol of bismuth nitrate pentahydrate to 10-20 mL of ethylene glycol and stir for 40-50 minutes to form solution A;

[0007] (2) Add 0.1-0.2 mmol of ammonium molybdate tetrahydrate to 10-20 mL of ethylene glycol and sonicate for 20-30 min to form solution B;

[0008] (3) Pour solution B into solution A, stir for 5-20 minutes, then drop 0.5-1 ml of NaOH solution, and continue stirring for 10-20 minutes. The concentration of NaOH solution is 1-2 mol / L.

[0009] (4) The mixed solution obtained in step (3) was placed in a 50 ml hydrothermal kettle, and then placed in a hydrothermal oven with the oven parameters set at 120-160°C for 20-30 hours;

[0010] (5) The precipitated product obtained in step (4) was washed by alternating centrifugation with hydrated ethanol and then dried in a drying oven at 80°C;

[0011] (6) The dried sample is sintered at 250-500°C for 1-3 hours to obtain BiMoO6 / Bi2O3 nanomaterials.

[0012] The Al2O3 ceramic tube of the present invention has an inner diameter of 0.6-0.8 mm, an outer diameter of 1.0-1.5 mm, and a length of 4-5 mm;

[0013] The width of a single gold electrode of the present invention is 0.4-0.5 mm, and the distance between two gold electrodes is 0.5-0.6 mm;

[0014] The length of the platinum wire of the present invention is 4 to 6 mm;

[0015] The nickel-cadmium heating coil of the present invention has 50 to 60 turns and a resistance of 30 to 40Ω.

[0016] A method for preparing a triethylamine sensor based on Bi2MoO6 / Bi2O3 nano-sensitive materials comprises the following steps:

[0017] (1) The sintered Bi2MoO6 / Bi2O3 nano-sensitive material is evenly dispersed in ethanol to form a paste slurry. The mixing ratio of the sensitive material to ethanol is 0.25mg~0.5mg:1mg. A small amount of slurry is evenly coated on the surface of the Al2O3 ceramic tube with a brush, covering the two gold electrodes on the surface of the ceramic tube to form a 15~30μm thick sensitive material film.

[0018] (2) After coating, the ceramic tube is placed under an infrared lamp and baked for 10 to 20 minutes until the surface sensitive material film is firmly attached to the surface of the ceramic tube. Then, a nickel-cadmium heating coil is passed through the interior of the Al2O3 ceramic tube as a heating wire. Finally, the above devices are welded and packaged using four platinum wires and the heating wire to obtain a triethylamine sensor based on Bi2MoO6 / Bi2O3 nano-sensitive material.

[0019] The advantages of the present invention are: by regulating the sintering temperature of the sensitive material, the sensitive material can obtain a micro-nano structure that is conducive to chemical reaction with the gas, and at the same time the sensitive material can obtain higher chemical activity, thereby improving the sensitivity of the sensor; the synthesis method of the Bi2MoO6 / Bi2O3 nano-sensitive material is simple, highly repeatable, and low-cost; the device process is simple, the volume is small, and it is suitable for mass production; the response time is extremely short, providing an effective sensitive material for the development of high-performance triethylamine sensors, and is of great significance in the fields of new sensitive material development, environmental testing, and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic structural diagram of the Bi2MoO6 / Bi2O3-based triethylamine sensor of the present invention, wherein the Al2O3 insulating ceramic tube 1, the platinum wire 2, the gold electrode 3, the nickel-cadmium alloy coil 4, and the nano-sensitive material 5 are shown;

[0021] Figure 2 The XRD patterns of the Bi2MoO6 / Bi2O3 nano-sensitive materials prepared in Example 1 and in Example 4 are shown; all diffraction peaks of the two samples can be well classified as a mixture of Bi2MoO6 (JCPDS 21-102) and Bi2O3 (JCPDS 27-50). From the intensities of the diffraction peaks in the XRD patterns, it can be seen that the contents of Bi2MoO6 and Bi2O3 in the two samples are different, but this does not affect the crystalline phase.

[0022] Figure 3The SEM images (ab) of Bi2MoO6 / Bi2O3 prepared in Example 1 and Example 4, the HRTEM images (cd) of Bi2MoO6 / Bi2O3 prepared in Example 1; the TEM image (e) and element distribution spectrum (fh) of Bi2MoO6 / Bi2O3 prepared in Example 1; as shown in Figures a and b, both samples are hollow sphere structures, but the microstructure of the sample surface has obvious changes at different sintering temperatures, the surface a is nanosheets, and the surface b is nanoparticles. Figures c and d are HRTEM images of Example 1, 0.319nm corresponds to the (100) crystal plane of Bi2O3, and 0.315nm corresponds to the (131) crystal plane of Bi2MoO6. Figure e is the TEM image of Example 1, (fh) is the element distribution spectrum, where (f) is Bi element, (g) is Mo element, and (h) is O element;

[0023] Figure 4 1 is the sensitivity curve of the sensor prepared in Example 1 and Example 4 to 100 ppm triethylamine in the operating temperature range of 225 to 300° C.;

[0024] Figure 5 1 is a bar graph showing the sensitivity of the sensors prepared in Example 1 and Example 4 to triethylamine at different concentrations at an operating temperature of 250° C.;

[0025] Figure 6 The instantaneous response curves of the sensors prepared in Examples 1 and 4 to 100 ppm triethylamine at an operating temperature of 250°C are shown. Both sensors have fast response recovery rates, but Example 4 has a higher resistance in air.

[0026] Figure 7 The response time of the sensors prepared in Example 1 and Example 4 to different concentrations of triethylamine at an operating temperature of 250° C. The response time of Examples 1 and 4 to different concentrations of triethylamine is extremely short, both not exceeding 10 seconds, and the response time to 100 ppm of triethylamine is only 1 second.

[0027] Among them: For reducing gases, the response (sensitivity) of the sensor to the target gas is defined as S = Ra / Rg, where Ra and Rg represent the resistance values ​​of the sensor in air and in the target gas, respectively. The response time and recovery time are defined as the time required for the sensor resistance to reach 90% of the total resistance change from a stable value during the adsorption or desorption process. DETAILED DESCRIPTION

[0028] like Figure 1As shown, it consists of an Al2O3 ceramic tube 1 substrate with two parallel, annular and separate gold electrodes 3 on the outer surface, a nano-sensitive material 5 coated on the outer surface of the Al2O3 ceramic tube 1 and the gold electrodes 3, and a nickel-cadmium heating coil 4 placed in the Al2O3 ceramic tube. Each gold electrode 3 is connected to two platinum wires 2.

[0029] Example 1

[0030] 1. Add 2.6mmol of bismuth nitrate pentahydrate to 15mL of ethylene glycol and stir for 45 minutes to form solution A; add 0.18mmol of ammonium molybdate tetrahydrate to 15mL of ethylene glycol and ultrasonicate for 25 minutes to form solution B; pour solution B into solution A, stir for 10 minutes, then drop 0.5ml of NaOH solution and continue stirring for 15 minutes. The concentration of NaOH solution is 1mol / L. The above mixed solution is placed in a 50ml hydrothermal kettle and then placed in a hydrothermal oven with the oven parameters set to 150℃ for 24h; then the precipitated product obtained after the reaction is washed by alternating centrifugation with hydrated ethanol and dried in an 80℃ drying oven;

[0031] 2. The dried sample was sintered at 400°C for 2 h to obtain BiMoO6 / Bi2O3 nanomaterials;

[0032] 3. The sintered Bi2MoO6 / Bi2O3 nano-sensitive material is evenly dispersed in ethanol to form a paste slurry. The mixing ratio of sensitive material to ethanol is 0.3mg:1mg. A small amount of slurry is dipped with a brush and evenly coated on the surface of the Al2O3 ceramic tube, covering the two gold electrodes on the surface of the ceramic tube, to form a 20μm thick sensitive material film.

[0033] 4. After coating, the ceramic tube was baked under an infrared lamp for 15 minutes until the surface sensitive material film was firmly attached to the ceramic tube surface. A nickel-cadmium heating coil was then passed through the interior of the Al2O3 ceramic tube as a heating wire. Finally, the device was soldered and packaged using four platinum wires and the heating wire, resulting in a triethylamine sensor based on the Bi2MoO6 / Bi2O3 nanomaterial.

[0034] The inner diameter of the Al2O3 ceramic tube is 0.7 mm, the outer diameter is 1.2 mm, and the length is 4.5 mm. The width of a single gold electrode is 0.45 mm, and the distance between two gold electrodes is 0.55 mm. The length of the platinum wire extending from the gold electrode is 5 mm. The nickel-cadmium heating coil has 55 turns and a resistance of 35 Ω.

[0035] Example 2

[0036] 1. Add 2.0mmol of bismuth nitrate pentahydrate to 10mL of ethylene glycol and stir for 40min to form solution A; add 0.10mmol of ammonium molybdate tetrahydrate to 10mL of ethylene glycol and ultrasonicate for 20min to form solution B; pour solution B into solution A, stir for 5min, then drop 0.8ml of NaOH solution and continue stirring for 10min. The concentration of NaOH solution is 1.5mol / L. The above mixed solution is placed in a 50ml hydrothermal kettle and then placed in a hydrothermal oven with the oven parameters set to 120℃ for 20h; then the precipitated product obtained after the reaction is washed by alternating centrifugation with hydrated ethanol and dried in an 80℃ drying oven;

[0037] 2. The dried sample was sintered at 250°C for 1 h to obtain BiMoO6 / Bi2O3 nanomaterials;

[0038] 3. The sintered Bi2MoO6 / Bi2O3 nano-sensitive material is evenly dispersed in ethanol to form a paste slurry. The mixing ratio of sensitive material to ethanol is 0.25mg:1mg. A small amount of slurry is evenly coated on the surface of the Al2O3 ceramic tube with a brush, covering the two gold electrodes on the surface of the ceramic tube to form a 15μm thick sensitive material film.

[0039] 4. After coating, the ceramic tube was baked under an infrared lamp for 10 minutes until the surface sensitive material film was firmly attached to the ceramic tube surface. A nickel-cadmium heating coil was then passed through the interior of the Al2O3 ceramic tube as a heating wire. Finally, the device was welded and packaged using four platinum wires and the heating wire, thereby obtaining a triethylamine sensor based on the Bi2MoO6 / Bi2O3 nano-sensitive material.

[0040] The inner diameter of the Al2O3 ceramic tube is 0.6 mm, the outer diameter is 1.0 mm, and the length is 4 mm; the width of a single gold electrode is 0.4 mm, and the distance between two gold electrodes is 0.5 mm; the length of the platinum wire leading from the gold electrode is 4 mm; the nickel-cadmium heating coil has 50 turns and a resistance of 30 Ω.

[0041] Example 3:

[0042] 1. Add 3.0mmol of bismuth nitrate pentahydrate to 20mL of ethylene glycol and stir for 50min to form solution A; add 0.20mmol of ammonium molybdate tetrahydrate to 20mL of ethylene glycol and ultrasonicate for 30min to form solution B; pour solution B into solution A, stir for 20min, then drop 1.0ml of NaOH solution and continue stirring for 20min. The concentration of NaOH solution is 2mol / L. The above mixed solution is placed in a 50ml hydrothermal kettle and then placed in a hydrothermal oven with the oven parameters set to 160℃ for 30h; then the precipitated product obtained after the reaction is washed by alternating centrifugation with hydrated ethanol and dried in an 80℃ drying oven;

[0043] 2. The dried sample was sintered at 500°C for 3 h to obtain BiMoO6 / Bi2O3 nanomaterials;

[0044] 3. The sintered Bi2MoO6 / Bi2O3 nano-sensitive material is evenly dispersed in ethanol to form a paste slurry. The mixing ratio of sensitive material to ethanol is 0.5mg:1mg. A small amount of slurry is dipped with a brush and evenly coated on the surface of the Al2O3 ceramic tube, covering the two gold electrodes on the surface of the ceramic tube, to form a 30μm thick sensitive material film.

[0045] 4. After coating, the ceramic tube was baked under an infrared lamp for 20 minutes until the surface sensitive material film was firmly attached to the ceramic tube surface. A nickel-cadmium heating coil was then passed through the interior of the Al2O3 ceramic tube as a heating wire. Finally, the device was soldered and packaged using four platinum wires and the heating wire, resulting in a triethylamine sensor based on the Bi2MoO6 / Bi2O3 nano-sensitive material.

[0046] The inner diameter of the Al2O3 ceramic tube is 0.8mm, the outer diameter is 1.5mm, and the length is 5mm; the width of a single gold electrode is 0.5mm, and the distance between two gold electrodes is 0.6mm; the length of the platinum wire leading from the gold electrode is 6mm; the nickel-cadmium heating coil has 60 turns and a resistance of 40Ω.

[0047] Example 4

[0048] 1. Add 2.6mmol of bismuth nitrate pentahydrate to 15mL of ethylene glycol and stir for 45 minutes to form solution A; add 0.18mmol of ammonium molybdate tetrahydrate to 15mL of ethylene glycol and ultrasonicate for 25 minutes to form solution B; pour solution B into solution A, stir for 10 minutes, then drop 0.5ml of NaOH solution and continue stirring for 15 minutes. The concentration of NaOH solution is 1mol / L. The above mixed solution is placed in a 50ml hydrothermal kettle and then placed in a hydrothermal oven with the oven parameters set to 150℃ for 24h; then the precipitated product obtained after the reaction is washed by alternating centrifugation with hydrated ethanol and dried in an 80℃ drying oven;

[0049] 2. The dried sample was sintered at 300℃ for 2h to obtain BiMoO6 / Bi2O3 nanomaterials.

[0050] 3. The sintered Bi2MoO6 / Bi2O3 nano-sensitive material is evenly dispersed in ethanol to form a paste slurry. The mixing ratio of sensitive material to ethanol is 0.3mg:1mg. A small amount of slurry is dipped with a brush and evenly coated on the surface of the Al2O3 ceramic tube, covering the two gold electrodes on the surface of the ceramic tube, to form a 20μm thick sensitive material film.

[0051] 4. After coating, the ceramic tube was baked under an infrared lamp for 15 minutes until the surface sensitive material film was firmly attached to the ceramic tube surface. A nickel-cadmium heating coil was then inserted into the Al2O3 ceramic tube as a heating wire. Finally, the device was soldered and packaged using four platinum wires and the heating wire, resulting in a triethylamine sensor based on the Bi2MoO6 / Bi2O3 nanomaterial.

[0052] like Figure 7 As shown, the response time of Example 1 and Example 4 to different concentrations of triethylamine is extremely short, both not exceeding 10 seconds, and the response time to 100 ppm of triethylamine is only 1 second. Compared with some existing triethylamine sensors based on other sensitive materials, the response time of existing sensors is generally longer.

[0053] For example, a reported triethylamine sensor based on Bi2WO6 material has a response time of 7s to 100ppm triethylamine; a triethylamine sensor based on Co3O4 / ZnO material has a response time of 25s to 200ppm triethylamine; a triethylamine sensor based on In2O3 material has a response time of 10s to 50ppm triethylamine; a triethylamine sensor based on SnO2 / Co3O4 material has a response time of 10s to 100ppm triethylamine; a triethylamine sensor based on RGO / SnO2 material has a response time of 10s to 50ppm triethylamine; a triethylamine sensor based on In2O3 / Mn2O3 material has a response time of 69s to 100ppm triethylamine; and a triethylamine sensor based on CuO@In2O3 / ZnO material has a response time of 246s to 10ppm triethylamine.

Claims

1. A triethylamine gas sensor based on Bi2MoO6 / Bi2O3 nano-sensitive materials, comprising an Al2O3 ceramic tube substrate with two parallel, annular, and discrete gold electrodes on its outer surface; a nano-sensitive material coated on the outer surface of the Al2O3 ceramic tube and the gold electrodes; and a nickel-cadmium heating coil placed within the Al2O3 ceramic tube. Each gold electrode is connected to two platinum wires. The sensor is characterized by: The nano-sensitive material is Bi2MoO6 / Bi2O3 nano-material, and its preparation steps are as follows: (1) Add 2-3 mmol of bismuth nitrate pentahydrate to 10-20 mL of ethylene glycol and stir for 40-50 minutes to form solution A; (2) Add 0.1-0.2 mmol of ammonium molybdate tetrahydrate to 10-20 mL of ethylene glycol and sonicate for 20-30 min to form solution B; (3) Pour solution B into solution A, stir for 5-20 minutes, then drop 0.5-1 ml of NaOH solution and continue stirring for 10-20 minutes. The concentration of NaOH solution is 1-2 mol / L. (4) The mixed solution obtained in step (3) was placed in a 50 ml hydrothermal kettle, and then placed in a hydrothermal oven with the oven parameters set at 120-160 °C for 20-30 h; (5) The precipitated product obtained in step (4) was washed by alternating centrifugation with water and ethanol, and then dried in a drying oven at 80°C; (6) The dried sample was sintered at 250-500 °C for 1-3 hours to obtain Bi2MoO6 / Bi2O3 nanomaterials.

2. The triethylamine gas sensor based on Bi2MoO6 / Bi2O3 nano-sensitive material according to claim 1, characterized in that: The Al2O3 ceramic tube has an inner diameter of 0.6-0.8 mm, an outer diameter of 1.0-1.5 mm, and a length of 4-5 mm.

3. The triethylamine gas sensor based on Bi2MoO6 / Bi2O3 nano-sensitive material according to claim 1, characterized in that: The width of the gold electrode is 0.4-0.5 mm, and the distance between the two gold electrodes is 0.5-0.6 mm.

4. The triethylamine gas sensor based on Bi2MoO6 / Bi2O3 nano-sensitive material according to claim 1, characterized in that: The length of the platinum wire is 4-6 mm.

5. The triethylamine gas sensor based on Bi2MoO6 / Bi2O3 nano-sensitive material according to claim 1, characterized in that: The nickel-cadmium heating coil has 50 to 60 turns and a resistance of 30 to 40Ω.

6. The method for preparing a triethylamine gas sensor based on Bi2MoO6 / Bi2O3 nano-sensitive materials according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) The sintered Bi2MoO6 / Bi2O3 nano-sensitive material is evenly dispersed in ethanol to form a paste slurry. The mixing ratio of the nano-sensitive material to ethanol is 0.25mg~0.5mg:1mg. A small amount of slurry is evenly coated on the surface of the Al2O3 ceramic tube with a brush, covering the two gold electrodes on the surface of the ceramic tube to form a 15~30μm thick sensitive material film. (2) After coating, the ceramic tube is placed under an infrared lamp and baked for 10 to 20 minutes until the surface sensitive material film is firmly attached to the surface of the ceramic tube. Then, a nickel-cadmium heating coil is passed through the interior of the Al2O3 ceramic tube as a heating wire. Finally, four platinum wires and heating wires are used to weld and package the two gold electrodes and the ceramic tube that are firmly attached to the sensitive material film to obtain a triethylamine sensor based on Bi2MoO6 / Bi2O3 nano-sensitive material.

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