Triethylamine sensor of Zr-doped Co3O4 nanosheet sensitive material prepared based on coprecipitation method and preparation method of triethylamine sensor

Abstract

The invention discloses a triethylamine sensor of a Zr-doped Co3O4 nanosheet sensitive material prepared based on a coprecipitation method and a preparation method of the triethylamine sensor, and belongs to the technical field of semiconductor metal oxide gas sensors. The sensor is composed of an Al2O3 ceramic tube, a Ni-Cr heating wire and a nanosheet sensitive material, wherein the outer surface of the Al2O3 ceramic tube is provided with two parallel, annular and independent gold electrodes, the Ni-Cr heating wire is arranged in the ceramic tube, and the surfaces of the Al2O3 ceramic tube and the gold electrodes are coated with the nanosheet sensitive material. The preparation method comprises the following steps: firstly, synthesizing a Co3O4 nanosheet sensitive material by using cobalt nitrate hexahydrate and sodium hydroxide through a coprecipitation method, and synthesizing the Zr-doped Co3O4 nanosheet sensitive material by adding zirconyl nitrate hydrate. The material has high response (146.6-100ppm) and fast response recovery time (156 / 60s) to low-concentration triethylamine gas under the working condition of 150 DEG C, so that the material has a wide application prospect in the aspect of detecting triethylamine in a specific environment.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor metal oxide gas sensor technology, specifically relating to a triethylamine sensor based on Zr-doped Co3O4 nanosheet sensitive material prepared by co-precipitation method and its preparation method. Background Technology

[0002] Triethylamine (TEA) is a flammable and toxic volatile organic compound (VOC). It is widely used in various industrial settings as a solvent, inhibitor, and preservative. However, exposure to TEA can cause severe irritation to facial skin, eyes, and respiratory tract. Accidental inhalation can damage the circulatory system, central nervous system, respiratory organs, and liver, and in extreme cases, may even lead to death. The National Institute for Occupational Safety and Health (NIOSH) recommends an indoor TEA concentration limit of 10 ppm. Therefore, developing efficient TEA gas sensors to detect and monitor TEA concentrations is of great significance for human safety in specific environments.

[0003] There are various methods for detecting triethylamine gas, such as liquid / gas chromatography and mass spectrometry. However, these methods suffer from drawbacks such as large equipment size, high cost, complex operation procedures, and long detection times, which limit their widespread application to some extent. In contrast, gas sensors, due to their small size, simple fabrication methods, and ease of integration, can achieve real-time monitoring and detection of specific gases. Among the many types of gas sensors, resistive gas sensors using semiconductor metal oxides as sensing materials have advantages such as high response value, high stability, good selectivity, fast response and recovery speed, and low cost, making them one of the most widely used gas sensors currently.

[0004] Co3O4 is a p-type metal-oxide semiconductor with a typical AB2O4 spinel structure. It is a cubic spinel structure with a band gap of 1.6–2.2 eV and a lattice constant of 0.8084 nm, in which oxygen ions are arranged in a cubic close-packed configuration. 2+ Occupying 1 / 8 of the tetrahedral interstitial space and coordinated with oxygen in all four lattice spaces, Co 3+ Occupying half of the octahedral interstitial space and coordinating with oxygen in six lattice spaces, Co3O4's multivalent nature, weak Co-O bond strength, low oxygen vacancy formation energy, and high lattice oxygen mobility are conducive to redox reactions. Furthermore, Co3O4 exhibits high catalytic activity and is frequently used by researchers in the field of gas sensing to detect gases such as carbon monoxide (CO), hydrogen sulfide (H2S), and acetone. Numerous studies have explored improving the gas-sensing performance of Co3O4 nanomaterials through doping (e.g., with Ti, Ag, Cd, Mn, etc.), thus the preparation of Zr-doped Co3O4 nanomaterials shows promise as a sensing material for high-performance triethylamine detection devices. Summary of the Invention

[0005] The purpose of this invention is to provide a triethylamine sensor based on Zr-doped Co3O4 nanosheet sensitive material prepared by co-precipitation method and its preparation method.

[0006] This invention first synthesizes Co3O4 nanosheet sensing materials via a co-precipitation method using cobalt nitrate hexahydrate (Co(NO3)2・6H2O) and sodium hydroxide (NaOH). Then, Zr-doped Co3O4 nanosheet sensing materials are synthesized by adding zirconium oxynitrate hydrate (ZrO(NO3)2・xH2O) during the synthesis process. This material exhibits high response (146.6~100ppm) and rapid response recovery time (156 / 60s) to low concentrations of triethylamine gas under operating conditions at 150℃. The commercially available side-heated sensor structure used in this invention has a simple fabrication process, small size, and is suitable for industrial mass production, possessing significant application value and broad application prospects in detecting triethylamine in specific environments.

[0007] The present invention discloses a triethylamine sensor based on Zr-doped Co3O4 nanosheet sensitive material prepared by co-precipitation method, which consists of an Al2O3 ceramic tube with two parallel, ring-shaped and discrete gold electrodes on its outer surface, a Ni-Cr heating wire inserted into the Al2O3 ceramic tube, Zr-doped Co3O4 nanosheet sensitive material prepared by co-precipitation method coated on the Al2O3 ceramic tube and the gold electrode surface, and a hexagonal base.

[0008] The present invention discloses a method for preparing a triethylamine sensor based on Zr-doped Co3O4 nanosheet sensitive material prepared by co-precipitation, the steps of which are as follows: (1) Dissolve 1~2g of cobalt nitrate hexahydrate (Co(NO3)2・6H2O) and 0.02~0.03g of zirconium oxynitrate hydrate (ZrO(NO3)2・xH2O) in 40~60mL of deionized water; (2) Add 40-60 mL of 15 mg / mL sodium hydroxide (NaOH) aqueous solution to the solution obtained in step (1) and stir thoroughly for 0.5-1.5 hours; (3) The solution obtained in step (2) is washed by centrifugation with deionized water and anhydrous ethanol several times, and then the solid product is dried at 50~70℃; the powder obtained after drying is calcined in air at 450~550℃ for 2~4 hours, and then cooled to room temperature to obtain Zr-doped Co3O4 nanosheet sensitive material. (4) Take 40~60mg of Zr-doped Co3O4 nanosheet sensitive material obtained in step (3) and put it into an agate mortar, then add 1.5~3.0mL of deionized water and grind to form a uniform slurry; then use a fine-tipped brush to evenly coat the slurry onto the surface of the Al2O3 ceramic tube with two parallel, ring-shaped and independent gold electrodes on the outer surface, covering the surface of the Al2O3 ceramic tube and the gold electrodes, and the thickness of the sensitive material layer obtained is 0.1~0.3 mm; (5) Bake the ceramic tube coated in step (4) under an infrared lamp for 5 to 10 minutes. After the sensitive material is dry, weld the gold electrode of the Al2O3 ceramic tube to the four corners of the hexagonal base through a platinum wire lead; then pass a Ni-Cr heating wire through the inside of the Al2O3 ceramic tube and then weld it to the remaining two corners of the hexagonal base through a platinum wire lead, thereby obtaining the triethylamine sensor based on the Zr-doped Co3O4 nanosheet sensitive material prepared by the co-precipitation method.

[0009] The inner and outer diameters of the Al2O3 ceramic tube are 0.6~0.8 mm and 1.0~1.5 mm, respectively, and the length is 4~5 mm; the width of a single ring gold electrode is 0.4~0.5 mm, and the spacing between two gold electrodes is 0.5~0.6 mm; the length of the platinum wire leads drawn from the gold electrodes and Ni-Cr heating wire is 4~6 mm.

[0010] The present invention has the following advantages: 1. Zr-doped Co3O4 nanosheet sensitive materials were successfully prepared using a simple co-precipitation method, and the synthesis method is simple; 2. By doping a small amount of Zr into the Co3O4 sensitive material, the response value of the Co3O4-based sensor to TEA was significantly improved (146.6~10ppm) and the response time was reduced. The sensor also has excellent selectivity and good long-term stability, and has broad application prospects in detecting low concentrations of TEA gas in specific environments. 3. It adopts a commercially available off-grid sensor structure, which has a simple manufacturing process, small size, and is suitable for mass production. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of the triethylamine sensor based on Zr-doped Co3O4 prepared in this invention; Figure 2 XRD patterns of pure Co3O4 and Zr-doped Co3O4 (Zr-Co3O4) sensitive materials prepared in Comparative Example 1 and Example 1; Figure 3 (a) and (c) are SEM images of pure Co3O4 sensitive material at different magnification ratios; Figure 3(b) and (d) are SEM images of Zr-doped Co3O4 sensitive materials at different magnification ratios; Figure 4 (a) and (b) are TEM images of pure Co3O4 sensitive material and Zr-doped Co3O4 sensitive material, respectively; (c) is an HRTEM image of Zr-doped Co3O4 sensitive material. Figure 5 (a), (b), and (c) are the Co 2p XPS spectrum, O 1s XPS spectrum, and Zr 3d XPS spectrum of the Zr-doped Co3O4 sensitive material, respectively. Figure 6 The response curves of the sensors in Comparative Example 1 and Example 1 to 100ppm TEA gas at different operating temperatures are shown. Figure 7 The bar chart shows the response values ​​of the sensors to the six test gases in Comparative Example 1 and Example 1. Figure 8 (a) and (b) are the dynamic resistance curves of the sensors in Comparative Example 1 and Example 1, respectively, at the optimal operating temperature (150°C) of the sensors in 100ppm TEA gas as a function of time. Figure 9 (a) and (b) are the response recovery curves of the sensor in Example 1 at the optimal operating temperature (150°C) in 1ppm~20ppm and 20ppm~100ppm TEA gas, respectively; Figure 10 (a) and (b) are the response-TEA concentration characteristic curves of the sensor in Example 1 at the optimal operating temperature (150°C) in TEA gas at 1ppm~20ppm and 20ppm~100ppm, respectively; Figure 11 : This is the repeatability curve of the sensor in Example 1 at 150°C for 100ppm TEA, obtained in five cycles. Figure 12 : This is the long-term stability curve of the sensor's response to 100ppm TEA gas in Example 1; like Figure 1 As shown, the device consists of four parts: a hexagonal base 1, an Al2O3 ceramic tube 2 with two parallel, ring-shaped and separate gold electrodes, a sensitive material layer 3, and a Ni-Cr heating wire 4 passing through the Al2O3 ceramic tube. like Figure 2As shown, the XRD spectra of pure Co3O4 and Zr-doped Co3O4 are consistent with the Co3O4 standard card JCPDS 00-042-1467, confirming that the material is Co3O4. For Zr-doped Co3O4, because the amount of Zr is very small, it is difficult to find the Zr-related peaks in the XRD spectrum, but the peak shift confirms the successful incorporation of Zr. like Figure 3 As shown in the SEM images, the pure Co3O4 sample has densely packed nanosheets with uneven particle size and sparse and narrow pores, exhibiting a dense packing state; the Zr-doped Co3O4 sample shows significantly improved nanosheet dispersion, with the formation of a large number of open pore structures and clear gaps between nanosheets. like Figure 4 As shown, the TEM image reveals that the morphology of the material body is composed of nanosheets; the HRTEM image shows three lattice fringe spacings of 0.244 nm, 0.466 nm and 0.285 nm, which correspond to the (3,1,1), (1,1,1) and (2,2,0) crystal planes of Co3O4, respectively. like Figure 5 (a) shows the XPS spectrum of Co2p, and observations were made of the spectrum corresponding to Co2p. 3 / 2 and Co2p 1 / 2 The two strong peaks, at approximately 781.04 eV and 796.25 eV, correspond to Co. 2+ The oxidation state, and the peaks at approximately 779.74 eV and 794.80 eV correspond to Co. 3+ The oxidation state proves that Co is in the form of Co 2+ and Co 3+ It exists in the form of; Figure 5 (b) This indicates that the XPS spectrum of O 1s can be decomposed into three peaks located at 529.9, 530.6, and 531.7 eV, corresponding to lattice oxygen (O) and other peaks respectively. L ), oxygen vacancy (O V ) and adsorbed oxygen (O C ).like Figure 5 (c) This indicates that the XPS spectrum of Zr 3d can be decomposed into two peaks located at 181.9 and 184.3 eV, respectively, corresponding to the 3d peaks of Zr. 5 / 2 3D with Zr 3 / 2 Spin orbital peaks. Zr 3d 5 / 2 The spin-orbit peak can be deconvolved into two peaks, one of which, near 181.7 eV, belongs to Zr. 4+ Another peak near 182.3 eV belongs to relatively reduced Zr. δ+ This proves the existence of the valence state of Zr.

[0012] like Figure 6As shown, the optimal operating temperature of the sensors in Example 1 and Comparative Example 1 is 150°C; at the optimal operating temperature, the response values ​​of the devices in Example 1 and Comparative Example 1 to 100ppm TEA are 146.6 and 11.2, respectively; compared with the sensor in Comparative Example 1, the response value of the sensor in Example 1 is 12.1 times higher. like Figure 7 As shown, the sensors in Example 1 and Comparative Example 1 have the highest response to TEA, which is much higher than the responses to toluene, ethanol, methanol, acetone and formaldehyde. This indicates that the sensor in Example 1 has good selectivity for TEA gas while having a high response value. like Figure 8 As shown in (a), the sensor in Comparative Example 1 exhibits a relatively slow response and recovery curve to 100 ppm TEA gas at an operating temperature of 150°C, with a response time of 501 s and a recovery time of 557 s; Figure 8 As shown in (b), the sensor in Example 1 has a relatively fast response recovery curve to 100ppm TEA at an operating temperature of 150°C, with a response time of 156s, a recovery time of 60s, and a high response value. like Figure 9 As shown, the sensor in Example 1 exhibits excellent response and recovery characteristics to different concentrations (1ppm~100ppm) of TEA; like Figure 10 As shown, the sensor in Example 1 exhibits good response-concentration linear fitting relationships for both low concentrations (1~20ppm) and high concentrations (20~100ppm) of TEA, with fitting equations of y=0.04x+1.19 and y=1.80x-32.36, respectively, corresponding to... Figure 10 (a) and Figure 10 (b), where y represents the response value and x represents the gas concentration; like Figure 11 As shown, the sensor in Example 1 exhibits consistent response recovery characteristics in five 100ppm TEA gas tests, indicating that the sensor in Example 1 has good repeatability for TEA gas. like Figure 12 As shown, during 21 consecutive days of testing, the sensor in Example 1, operating at 150°C, showed a slight decrease in response to 100 ppm TEA gas, but still maintained high sensitivity.

[0013] Note: In this invention, the response value of the device (P-type semiconductor) in the test reducing gas is defined as the ratio of resistance (Rresponse). g / R a), where R a R represents the resistance between two gold electrodes in air. g This represents the resistance value between the two gold electrodes in the gas being tested. A static testing system is used during the test. The device is placed in a 1L gas cylinder, a certain amount of the VOC to be tested is injected, and the change in resistance is observed and recorded. The corresponding response value is then calculated. Detailed Implementation

[0014] Comparative Example 1 The fabrication process of the triethylamine sensor based on pure Co3O4 nanosheet sensitive material is as follows: (1) Dissolve 1.455g of cobalt nitrate hexahydrate (Co(NO3)2・6H2O) in 50mL of deionized water; (2) Add 50 mL of freshly prepared sodium hydroxide (NaOH) aqueous solution (15 mg / mL) to the solution obtained in step (1) and stir thoroughly for 1 hour; (3) The solution obtained in step (2) was washed by centrifugation with deionized water and anhydrous ethanol several times, and then the solid product was dried at 60°C; the dried powder was calcined in air at 500°C for 3 hours, and then cooled to room temperature to obtain Co3O4 nanosheet sensitive material with a product mass of 0.26g. (4) Take 50 mg of the Co3O4 nanosheet sensitive material obtained in step (3) and put it into an agate mortar. Then add 2 mL of deionized water and grind to form a uniform slurry. Then use a fine-tipped brush to evenly coat the slurry onto the surface of the Al2O3 ceramic tube with two parallel, ring-shaped and independent gold electrodes on the outer surface, covering the surface of the Al2O3 ceramic tube and the gold electrodes. The thickness of the sensitive material layer is 0.2 mm. (5) Bake the ceramic tube coated in step (4) under an infrared lamp for 8 minutes. After the sensitive material is dry, weld the gold electrode of the Al2O3 ceramic tube to the four corners of the hexagonal base through a platinum wire. Then, pass a Ni-Cr heating wire through the Al2O3 ceramic tube and weld it to the remaining two corners of the hexagonal base through a platinum wire to obtain the triethylamine sensor based on the pure Co3O4 nanosheet sensitive material prepared by the co-precipitation method.

[0015] The Al2O3 ceramic tube has an inner diameter of 0.7 mm, an outer diameter of 1.2 mm, and a length of 4.5 mm; the width of a single ring gold electrode is 0.45 mm, and the spacing between two gold electrodes is 0.55 mm; the length of the platinum wire leads drawn from the gold electrodes and the Ni-Cr heating wire is 5 mm.

[0016] Example 1 The fabrication process of the triethylamine sensor based on Zr-doped Co3O4 nanosheet sensitive material (Zr-Co3O4) is as follows: (1) Dissolve 1.455g of cobalt nitrate hexahydrate (Co(NO3)2・6H2O) and 0.023g of zirconium oxynitrate hydrate (ZrO(NO3)2・xH2O) in 50mL of deionized water; (2) Add 50 mL of freshly prepared sodium hydroxide (NaOH) aqueous solution (15 mg / mL) to the solution obtained in step (1) and stir thoroughly for 1 hour; (3) The solution obtained in step (2) was washed by centrifugation with deionized water and anhydrous ethanol several times, and the solid product obtained was dried at 60°C; the dried powder was calcined in air at 500°C for 3 hours, and cooled to room temperature to obtain Zr-doped Co3O4 nanosheet sensitive material with a product mass of 0.27g. (4) Take 50 mg of Zr-doped Co3O4 nanosheet sensitive material obtained in step (3) and put it into an agate mortar. Then add 2 mL of deionized water and grind to form a uniform slurry. Then use a fine-tipped brush to evenly coat the slurry onto the surface of the Al2O3 ceramic tube with two parallel, ring-shaped and independent gold electrodes on the outer surface, covering the surface of the Al2O3 ceramic tube and the gold electrodes. The thickness of the sensitive material layer is 0.2 mm. (5) Bake the ceramic tube coated in step (4) under an infrared lamp for 8 minutes. After the sensitive material is dry, weld the gold electrode of the Al2O3 ceramic tube to the four corners of the hexagonal base through a platinum wire. Then, pass a Ni-Cr heating wire through the Al2O3 ceramic tube and weld it to the remaining two corners of the hexagonal base through a platinum wire to obtain the triethylamine sensor based on the Zr-doped Co3O4 nanosheet sensitive material prepared by the co-precipitation method.

[0017] The Al2O3 ceramic tube has an inner diameter of 0.7 mm, an outer diameter of 1.2 mm, and a length of 4.5 mm; the width of a single ring gold electrode is 0.45 mm, and the spacing between two gold electrodes is 0.55 mm; the length of the platinum wire lead drawn from the Ni-Cr heating wire of the gold electrode is 5 mm.

Claims

1. A method for preparing a triethylamine sensor based on Zr-doped Co3O4 nanosheet sensitive material prepared by co-precipitation, the steps of which are as follows: (1) Dissolve 1~2g of cobalt nitrate hexahydrate and 0.02~0.03g of zirconium oxynitrate hydrate in 40~60mL of deionized water; (2) Add 40-60 mL of 15 mg / mL sodium hydroxide aqueous solution to the solution obtained in step (1) and stir thoroughly for 0.5-1.5 hours; (3) The solution obtained in step (2) is washed by centrifugation with deionized water and anhydrous ethanol several times, and then the solid product is dried at 50~70℃; the powder obtained after drying is calcined in air at 450~550℃ for 2~4 hours, and then cooled to room temperature to obtain Zr-doped Co3O4 nanosheet sensitive material. (4) Take 40~60mg of Zr-doped Co3O4 nanosheet sensitive material obtained in step (3) and put it into an agate mortar, then add 1.5~3.0mL of deionized water and grind to form a uniform slurry; then evenly coat the slurry onto the surface of the Al2O3 ceramic tube with two parallel, ring-shaped and independent gold electrodes on the outer surface, covering the surface of the Al2O3 ceramic tube and the gold electrodes; (5) Bake the ceramic tube coated in step (4) under an infrared lamp for 5 to 10 minutes. After the sensitive material is dry, weld the gold electrode of the Al2O3 ceramic tube to the four corners of the hexagonal base through a platinum wire lead; then pass a Ni-Cr heating wire through the inside of the Al2O3 ceramic tube and then weld it to the remaining two corners of the hexagonal base through a platinum wire lead, thereby obtaining the triethylamine sensor based on the Zr-doped Co3O4 nanosheet sensitive material prepared by the co-precipitation method.

2. The method for preparing a triethylamine sensor based on Zr-doped Co3O4 nanosheet sensitive material prepared by co-precipitation as described in claim 1, characterized in that: The thickness of the sensitive material layer obtained in step (4) is 0.1~0.3 mm.

3. The method for preparing a triethylamine sensor based on Zr-doped Co3O4 nanosheet sensitive material prepared by co-precipitation as described in claim 1, characterized in that: The inner and outer diameters of the Al2O3 ceramic tube are 0.6~0.8 mm and 1.0~1.5 mm, respectively, and the length is 4~5 mm; the width of a single ring gold electrode is 0.4~0.5 mm, and the spacing between two gold electrodes is 0.5~0.6 mm; the length of the platinum wire leads drawn from the gold electrodes and Ni-Cr heating wire is 4~6 mm.

4. A triethylamine sensor based on Zr-doped Co3O4 nanosheet sensitive material prepared by co-precipitation method, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 3.

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