Zinc oxide / cobaltosic oxide Janus nanofiber gas-sensitive sensing material and preparation method thereof

Abstract

The invention provides a preparation method of a zinc oxide / cobaltosic oxide Janus nanofiber gas-sensitive sensing material and application of the zinc oxide / cobaltosic oxide Janus nanofiber gas-sensitive sensing material in triethylamine gas detection, and relates to the technical field of gas-sensitive sensing materials. Zinc nitrate hydrate and cobalt nitrate hydrate are used as raw materials, ethanol and N, N-dimethylformamide are used as solvents, polyvinylpyrrolidone is used as a template agent, and a parallel electrostatic spinning method is adopted to prepare a series of zinc oxide / cobaltosic oxide Janus nanofibers with different molar ratios. The semiconductor type gas sensor prepared from the Janus nanofiber gas-sensitive sensing material in which the molar ratio of zinc oxide to cobaltosic oxide is 2: 1 shows good gas-sensitive sensing characteristic and detection capability on triethylamine gas. The sensor has the advantages of high sensitivity, high response speed, good selectivity, stable work and the like on the triethylamine gas at 300 DEG C, and is beneficial to rapid detection and long-term monitoring of the triethylamine gas in the environment. According to the preparation method of the gas-sensitive sensing material, the used equipment is simple, the raw material cost is low, the preparation period is short, and large-scale production is easy to realize.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas-sensitive sensing materials, and particularly relates to a zinc oxide / cobalt tetroxide Janus nanofiber gas-sensitive sensing material, a preparation method thereof, and an application thereof in the detection of triethylamine gas. Background Art

[0002] Triethylamine is an amine organic compound, a colorless transparent oily liquid with a strong ammonia odor, flammable, toxic, and highly irritating. Industrially, it is mainly used as a solvent, curing agent, catalyst, polymerization inhibitor, preservative, and for the synthesis of dyes, etc. Once triethylamine leaks, it poses great hazards to the physical health and safe production of relevant practitioners, and seriously pollutes the surrounding atmospheric environment. Therefore, developing a gas sensor with high sensitivity, good selectivity, fast response speed, and stable operation for triethylamine gas is of great significance for the leakage warning and long-term monitoring of triethylamine gas.

[0003] Oxide semiconductor gas sensors are widely used in the detection of toxic, harmful, flammable, and explosive gases, the monitoring of environmental air quality and indoor air pollution, and medical diagnosis of respiratory gases. The core of such gas sensors for detecting gases lies in oxide semiconductor gas-sensitive sensing materials. Designing and constructing semiconductor heterostructures in gas-sensitive sensing materials can effectively improve their gas-sensitive sensing properties. By adjusting the Fermi level and controlling the carrier concentration in the semiconductor, a space charge region is formed in the heterostructure, changing and enhancing the resistivity of the semiconductor heterostructure in air and the degree of oxidation reaction with triethylamine gas, thereby improving its gas-sensitive sensing properties, increasing sensitivity, enhancing selectivity, accelerating the response speed, and strengthening stability.

[0004] Electrospinning is one of the commonly used technical means for preparing one-dimensional nanofibers. This method has the characteristics of simple operation, wide application range, high production efficiency, mild conditions, low equipment cost, and short product synthesis cycle. It is currently the main method for industrial synthesis of nanofibers. In addition, nanofibers have the characteristics of high specific surface area and anti-agglomeration, and are suitable for application in gas-sensitive sensing materials. Therefore, preparing one-dimensional zinc oxide / cobalt tetroxide Janus nanofibers by electrospinning has important practical application value and practical significance. Summary of the Invention

[0005] One of the purposes of the present invention is to provide for the first time a one-dimensional nanofiber with a Janus heterostructure and a preparation method thereof. The constituent materials in the Janus nanofiber are a zinc oxide / cobalt tetroxide Janus heterostructure, and its preparation method can be prepared by combining parallel electrospinning technology with a calcination oxidation method.

[0006] The second object of the present invention is to apply the Janus heterostructure to an oxide semiconductor gas sensor for the first time, explore and study the promoting effect of the Janus heterostructure on the gas sensing characteristics of triethylamine, and the mechanism of sensitivity enhancement of the Janus heterostructure.

[0007] The zinc oxide / cobalt tetroxide Janus nanofiber gas sensing material provided by the present invention can be prepared by the following method:

[0008] (1) Weigh 6.0 mL of DMF and 3.0 mL of C2H5OH and place them in a beaker. Under magnetic stirring, form a uniform and transparent solution. Then, according to the molar ratios of 2:1, 1:1, and 1:2, respectively weigh Zn(NO3)2·6H2O and Co(NO3)2·6H2O, and add them to the above transparent solution to prepare two salt solutions A and B. Finally, add 1.5 g of PVP to each and stir magnetically for 12 hours to obtain electrospinning solutions A and B;

[0009] (2) Use the parallel electrospinning technique for the above-prepared electrospinning solutions A and B to obtain zinc oxide / cobalt tetroxide precursor Janus nanofibers. After calcination at 550 °C for 1.5 hours, zinc oxide / cobalt tetroxide Janus nanofibers can be prepared;

[0010] (3) The zinc oxide / cobalt tetroxide Janus nanofibers prepared by the above method are characterized by X-ray powder diffraction (XRD, see Appendix Figure 1 ) to determine the composition. It can be found in the XRD pattern that the diffraction peaks of the synthesized material are consistent with those of zinc oxide and cobalt tetroxide, proving that the material synthesized by the above method is zinc oxide and cobalt tetroxide;

[0011] (4) The zinc oxide / cobalt tetroxide Janus nanofibers prepared by the above method are characterized by scanning electron microscopy (SEM, see Appendix Figures 2 - 4 ) to determine the microscopic morphology. It can be found in the SEM photograph that the synthesized material is nanofibers and has a Janus heterostructure, which proves that the material synthesized by the above method is indeed Janus nanofibers;

[0012] (5) The application of the zinc oxide / cobalt tetroxide Janus nanofiber gas sensing material provided by the present invention in gas sensing has the following working conditions:

[0013] (6) Fabricate the above gas-sensitive sensing material into a side-heated gas-sensitive element. The gas-sensitive element consists of a ceramic tube, a Cr-Ni alloy heating wire, and a hexagonal base. The surface of the ceramic tube is provided with two parallel, annular, and independent gold electrodes. Two platinum wires are led out from each gold electrode as signal electrodes, for a total of four signal electrodes. The fabrication process of the gas-sensitive element is as follows: First, weld the four signal electrodes on the ceramic tube to the hexagonal base, then place a Cr-Ni alloy heating wire in the ceramic tube and weld it to the hexagonal base to complete the assembly of the gas-sensitive element. Then, slightly grind the above gas-sensitive sensing material and add a slurry made of a small amount of ethanol, and evenly coat it on the surface of the ceramic tube with a fine brush. Finally, dry the gas-sensitive element at 80 °C for 24 hours to finally complete the fabrication of the gas-sensitive element.

[0014] (7) The advantages of the gas sensor based on the zinc oxide / cobalt tetroxide Janus nanofiber gas-sensitive sensing material provided by the present invention are as follows:

[0015] (8) 1. The microscopic morphology of the zinc oxide / cobalt tetroxide Janus nanofiber can be clearly seen by SEM as nanofibers formed by the parallel arrangement of two nanofibers, with an obvious Janus structure.

[0016] (9) 2. The zinc oxide / cobalt tetroxide Janus nanofiber has good gas-sensitive sensing characteristics such as high sensitivity, good selectivity, fast response speed, and stable operation to 100 ppm triethylamine gas.

[0017] (10) 3. The side-heated gas-sensitive element fabricated with the zinc oxide / cobalt tetroxide Janus nanofiber gas-sensitive sensing material has gas-sensitive sensing characteristics to triethylamine gas at a working temperature of 300 °C. The Janus heterostructure is first applied in the field of oxide semiconductor gas-sensitive sensing to study the mechanism of the improvement of the gas-sensitive performance of triethylamine gas by the Janus heterostructure. Description of the Drawings

[0018] Figure 1 : Powder X-ray diffraction (XRD) patterns of a series of zinc oxide / cobalt tetroxide Janus nanofiber gas-sensitive sensing materials with different molar ratios, zinc oxide, and cobalt tetroxide, and their standard XRD cards.

[0019] Figure 2 : Scanning electron microscope (SEM) photos of the zinc oxide / cobalt tetroxide Janus nanofiber (molar ratio 2:1) gas-sensitive sensing material obtained in Example 1.

[0020] Figure 3 : Scanning electron microscope (SEM) photos of the zinc oxide / cobalt tetroxide Janus nanofiber (molar ratio 1:1) gas-sensitive sensing material obtained in Example 2.

[0021] Figure 4 : Scanning electron microscope (SEM) photograph of the zinc oxide / cobalt tetroxide Janus nanofiber (molar ratio 1:2) gas-sensing material obtained in Example 3.

[0022] Figure 5 : Line graph of the response amplitude of the zinc oxide / cobalt tetroxide Janus nanofiber obtained in Example 1 to 100 ppm triethylamine gas at different temperatures.

[0023] Figure 6 : Histogram of the response characteristics of the zinc oxide / cobalt tetroxide Janus nanofiber obtained in Example 1 to 100 ppm different types of gases at the optimal temperature.

[0024] Figure 7 : Curve graph of the dynamic response and recovery time of the zinc oxide / cobalt tetroxide Janus nanofiber obtained in Example 1 to 5 ppm to 100 ppm triethylamine gas at the optimal temperature.

[0025] Figure 8 : Curve graph of the five-time repeated dynamic response and recovery time of the zinc oxide / cobalt tetroxide Janus nanofiber obtained in Example 1 to 100 ppm triethylamine gas at the optimal temperature. Detailed implementation method

[0026] To further illustrate the present invention, the following implementation examples are listed, but they do not limit the scope of the invention defined by the appended claims.

[0027] Example 1: Preparation of a zinc oxide / cobalt tetroxide Janus nanofiber gas-sensing material with a molar ratio of 2:1.

[0028] (1) Weigh 6.0 mL of DMF and 3.0 mL of C2H5OH and place them in a beaker, stir to form a uniform transparent solution, add 1.80 g of Zn(NO3)2·6H2O and 1.5 g of PVP, and after magnetic stirring for 12 hours, it serves as electrospinning solution A;

[0029] (2) Weigh 6.0 mL of DMF and 3.0 mL of C2H5OH and place them in a beaker, stir to form a uniform transparent solution, add 0.87 g of Co(NO3)2·6H2O and 1.5 g of PVP, and after magnetic stirring for 12 hours, it serves as electrospinning solution B;

[0030] (3) Electrospinning solution A and electrospinning solution B are used to obtain zinc oxide / cobalt tetroxide precursor Janus nanofibers through parallel electrospinning, and then calcined at 550 °C for 1.5 hours. Finally, a gas-sensitive material for detecting triethylamine described in the present invention is obtained, and this material is zinc oxide / cobalt tetroxide Janus nanofibers with a molar ratio of 2:1.

[0031] Example 2: Preparation of a gas-sensitive sensing material of zinc oxide / cobalt tetroxide Janus nanofibers with a molar ratio of 1:1.

[0032] (1) Weigh 6.0 mL of DMF and 3.0 mL of C2H5OH and place them in a beaker, stir to form a uniform transparent solution, add 0.90 g of Zn(NO3)2·6H2O and 1.5 g of PVP, and after magnetic stirring for 12 hours, it serves as electrospinning solution A;

[0033] (2) Weigh 6.0 mL of DMF and 3.0 mL of C2H5OH and place them in a beaker, stir to form a uniform transparent solution, add 0.87 g of Co(NO3)2·6H2O and 1.5 g of PVP, and after magnetic stirring for 12 hours, it serves as electrospinning solution B;

[0034] (3) Electrospinning solution A and electrospinning solution B are used to obtain zinc oxide / cobalt tetroxide precursor Janus nanofibers through parallel electrospinning, and then calcined at 550 °C for 1.5 hours. Finally, a gas-sensitive material for detecting triethylamine described in the present invention is obtained, and this material is zinc oxide / cobalt tetroxide Janus nanofibers with a molar ratio of 1:1.

[0035] Example 3: Preparation of a gas-sensitive sensing material of zinc oxide / cobalt tetroxide Janus nanofibers with a molar ratio of 1:2.

[0036] (1) Weigh 6.0 mL of DMF and 3.0 mL of C2H5OH and place them in a beaker, stir to form a uniform transparent solution, add 0.90 g of Zn(NO3)2·6H2O and 1.5 g of PVP, and after magnetic stirring for 12 hours, it serves as electrospinning solution A;

[0037] (2) Weigh 6.0 mL of DMF and 3.0 mL of C2H5OH and place them in a beaker, stir to form a uniform transparent solution, add 1.74 g of Co(NO3)2·6H2O and 1.5 g of PVP, and after magnetic stirring for 12 hours, it serves as electrospinning solution B;

[0038] (3) Electrospinning solution A and electrospinning solution B are used to obtain zinc oxide / cobalt ferrite precursor Janus nanofibers through parallel electrospinning, and then they are calcined at 550 °C for 1.5 hours. Finally, a gas-sensitive material for detecting triethylamine described in the present invention is obtained. This material is zinc oxide / cobalt ferrite Janus nanofibers with a molar ratio of 1:2.

Claims

1. A zinc oxide / cobalt tetroxide Janus nanofiber gas sensitive sensing material, characterized in that: It has gas sensing performance, the morphology is a nanofiber with a Janus heterostructure, the composition is a zinc oxide / cobalt tetroxide composite material, and the molecular formula is: ZnO / Co3O4.

2. The zinc oxide / cobalt tetroxide Janus nanofiber gas sensitive sensing material according to claim 1, characterized in that: The semiconductor gas sensor is prepared by parallel electrospinning technology and high-temperature calcination oxidation, and is produced by coating a gas-sensitive sensing material film.

3. The zinc oxide / cobalt tetroxide Janus nanofiber gas sensitive sensor material according to claim 1, characterized in that: Under a certain working temperature, the presence of triethylamine gas in the air can be detected by utilizing the change in the electrical signal of the semiconductor gas sensor, such as the resistance value, to realize the gas-sensitive sensing characteristics.

4. The zinc oxide / cobalt tetroxide Janus nanofiber gas sensitive sensor material according to claim 1, characterized in that: Its microscopic morphology is mainly nanofibers with Janus heterostructure, which is a left-right arranged structure composed of two oxide semiconductors, zinc oxide on one side and cobalt tetroxide on the other side. The left and right sides can be interchanged and can be an asymmetric structure. The two oxide semiconductors each form nanofibers, which are arranged in parallel to form Janus nanofibers. The composition and morphology of the material are determined. This gas-sensitive sensing material can stably exist in the form of a thin film on the ceramic tube electrode, so that gas-sensitive sensing can be carried out directly in the air. The gas-sensitive sensing material film can be reused and the gas-sensitive performance can still be maintained.

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