Gas sensor for detecting content of 3-vinylpyridine in real time and preparation method thereof

Abstract

The invention relates to the technical field of tobacco smoke analysis, and discloses a gas sensor for detecting the content of 3-vinylpyridine in real time and a preparation method of the gas sensor. In order to realize accurate detection of tobacco smoke in the environment, 3-vinylpyridine in environmental gas is taken as a detection object, a SnO2 nanofiber material is further taken as a gas sensitive element, the detection sensitivity of the 3-vinylpyridine is remarkably improved, the SnO2 nanofiber material is arranged on the heating substrate, and the gas sensitive element is arranged on the heating substrate. The gas sensor generates a resistance change signal which linearly changes along with the change of the content of 3-vinylpyridine, so that the environmental tracing of the tobacco smoke is realized. Therefore, the invention provides the gas sensor with high sensitivity and high accuracy for tobacco smoke environment tracing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tobacco smoke analysis, and particularly relates to a gas sensor for real-time detection of the content of 3-vinylpyridine in tobacco smoke. BACKGROUND

[0002] In the tobacco industry, it is necessary to detect and analyze the content of components in tobacco smoke or tobacco smoke, with the purpose of studying the characteristics of tobacco smoke or tobacco smoke, controlling the quality of tobacco products, or tracing the environment of tobacco smoke. Accurate content detection and in-depth analysis of various components contained in tobacco smoke or tobacco smoke, such as nicotine, tar, carbon monoxide, etc., are beneficial to achieve the above purposes.

[0003] The current commonly used technology for detection and analysis of tobacco smoke is: using adsorption materials to filter tobacco smoke, adsorbing chemical components in tobacco smoke by adsorption materials, then separating the adsorbed chemical components from the adsorption materials by solvent desorption or thermal desorption, and then detecting these chemical components by gas chromatography, nitrogen specific detector or gas chromatography / mass spectrometry. However, this method has the following disadvantages: Firstly, this detection method needs to contain adsorption and desorption operations for chemical components, and its detection accuracy depends on the adsorption and desorption characteristics of the adsorption material for the chemical components in the smoke. Generally, the adsorption performance of the adsorption material for the chemical components in the smoke is good, but its desorption performance may be poor, so the detection sensitivity and resolution of this method are poor. Secondly, it has the disadvantages of complicated sample preparation and inability to perform real-time detection.

[0004] In order to improve the detection accuracy of tobacco smoke, the existing technology improves the adsorption material. For example, a Chinese patent with application number 2021100295949 discloses a composite filter sheet for smoke detection and its preparation method and application, which forms a composite filter sheet as an adsorption material by sequentially stacking a glass fiber layer and a synthetic fiber layer. Specifically, the glass fiber layer ensures the filtration accuracy of the composite filter sheet, and the synthetic fiber layer effectively intercepts water vapor in the smoke, thereby enabling the composite filter sheet to effectively capture chemical components including nicotine in tobacco smoke, and ultimately achieving accurate detection of the content of chemical components in tobacco smoke. However, the detection method provided by this patent still has the disadvantages of complicated detection process and inability to perform real-time detection, and cannot be effectively applied to environmental tracing of tobacco smoke or smoke, such as identification and tracing of "second-hand smoke" environment.

[0005] A gas sensor is a kind of converter that converts the volume fraction of a certain gas into a corresponding electrical signal. It converts the relevant characteristics of the gas into measurable electrical signals such as voltage and current by detecting the composition and concentration of a specific gas, so as to realize sensitive and accurate detection of specific components in the gas. In the prior art, gas sensors can be used for detecting gas components such as CO, nitrogen oxides (NOx) and H2S in the environment, but since the above-mentioned gases can be the source of non-tobacco smoke, the above-mentioned gas components cannot become the identifying tracer detection object for environmental tracing of tobacco smoke or smoke.

[0006] 3-vinylpyridine is a main pyrolysis product of nicotine and mainly exists in tobacco aerosol. 3-vinylpyridine can be used as an environmental tracer of tobacco smoke. Therefore, sensitive and efficient detection of 3-vinylpyridine in the environment is of great significance for environmental tracing of tobacco smoke. However, in the prior art, there is no accurate detection method for the content of 3-vinylpyridine in the gas. SUMMARY

[0007] In order to solve the technical problem of environmental tracing of tobacco smoke, and more specifically, to provide a tobacco smoke tracing method and a sensitive detection method taking 3-vinylpyridine as the detection object, the present application provides a gas sensor for real-time detection of the content of 3-vinylpyridine and a preparation method thereof.

[0008] The specific technical scheme of the present application is as follows: In one aspect, the present application provides a gas sensor for real-time detection of the content of 3-vinylpyridine, which comprises a heating substrate and a gas sensitive element arranged on the heating substrate. The gas sensitive element is a SnO2 nanofiber material, which is used for specific adsorption of 3-vinylpyridine molecules in environmental smoke, and generates a linearly changed resistance change signal with the change of the content of 3-vinylpyridine.

[0009] In the prior art, in order to realize the detection of a certain component in tobacco smoke, in addition to the adsorption step of the component to be detected, the component to be detected needs to be resolved by solvent or thermal desorption, and finally the content of the component to be detected can be detected. This method has a complicated detection process and cannot realize real-time detection, which cannot meet the sensitivity requirements of environmental tracing of tobacco smoke.

[0010] In order to realize accurate detection of tobacco smoke in the environment, the present application takes 3-vinylpyridine in the environmental gas as the detection object, and further takes SnO2 nanofiber material as the gas sensitive element, significantly improves the detection sensitivity of 3-vinylpyridine, sets the SnO2 nanofiber material on the heating substrate to form a gas sensor that generates a linearly changed resistance change signal with the change of the content of 3-vinylpyridine, and realizes the environmental tracing of tobacco smoke. Thus, the present application provides a gas sensor with high sensitivity and high accuracy for the environmental tracing of tobacco smoke.

[0011] The present application has high sensitivity and high accuracy for the environmental tracing of tobacco smoke, which is due to the selection of the detection object 3-vinylpyridine and the selection of the gas sensitive element SnO2 nanofiber material specifically matched therewith. The SnO2 nanofiber material generates a linearly changed resistance change signal with the change of the concentration of 3-vinylpyridine in the environmental gas, and the higher the concentration of 3-vinylpyridine, the higher the resistance value of the gas sensitive element formed by the SnO2 nanofiber material. It has been verified by experiments that even in the environmental gas with a concentration as low as 5 ppm, the SnO2 nanofiber material can show a larger resistance value change information, which reflects the sensitive sensing performance of the SnO2 nanofiber material to the change of the concentration of 3-vinylpyridine gas.

[0012] And it has been verified by experiments that among nicotine, pyridine, glycerol, toluene, methanol, chloroform and 3-vinylpyridine, the resistance signal change amount of the SnO2 nanofiber material with the change of the content of 3-vinylpyridine is much larger than the resistance signal change amount caused by the change of the content of other components, that is, if a small amount of nicotine, pyridine, glycerol, toluene and other substances is produced in the air, the resistance signal change amount caused by nicotine, pyridine, glycerol, toluene and other substances is small, and it is difficult to detect the resistance change amount signal; if a very small amount of 3-vinylpyridine is produced in the air, it can cause a large resistance value change of the gas sensor of the present application, therefore, a very small amount of 3-vinylpyridine can cause the response detection of the gas sensor of the present application.

[0013] In the present application, the heating substrate is used to heat the gas sensitive element to reach the required working temperature of the present application, and as an electric element that provides a certain resistance value in a general gas sensor.

[0014] As a preferred embodiment of the above-mentioned gas sensor, the heating substrate makes the temperature of the gas sensitive element 170℃-240℃ by electric heating in the working state of detection.

[0015] The SnO2 nanofiber material forms specific coordination with the pyridine ring and vinyl group in the 3-vinylpyridine molecule due to its special surface electronic structure, and exhibits selective adsorption capacity for the 3-vinylpyridine molecule. After the SnO2 conduction band captures electrons to form specific coordination, an electron depletion layer is formed on the surface of the material, resulting in an increase in resistance. Therefore, after the 3-vinylpyridine molecule is adsorbed, the resistance change signal of the SnO2 nanofiber material after adsorbing the 3-vinylpyridine is obvious, and the resistance change signal is much larger than the resistance change signal caused by other components. The resistance change signal is more obvious when the temperature of the SnO2 nanofiber material is 170-240°C. Therefore, the working temperature of the SnO2 nanofiber material as a gas sensor of a gas sensing element is preferably 170-240°C.

[0016] Further preferably, in the working state of detection, the heating substrate makes the temperature of the gas sensing element 225°C through electric heating. The above resistance change signal is most obvious when the temperature of the SnO2 nanofiber material is 225°C.

[0017] As the preferred gas sensor, the heating substrate comprises an Al2O3 ceramic tube, a heating coil arranged in the Al2O3 ceramic tube, and an electrode arranged on the Al2O3 ceramic tube.

[0018] As the preferred gas sensor, the gas sensing element is arranged on the surface of the Al2O3 ceramic tube.

[0019] On the other hand, the application provides a preparation method of a gas sensor for real-time detection of the content of 3-vinylpyridine, comprising the steps of preparing a SnO2 nanofiber material, and coating a slurry formed by the SnO2 nanofiber material on the surface of a heating substrate to form a gas sensing element.

[0020] The preparation method of the gas sensor comprises the following steps: Step S1, preparing a SnO2 nanofiber material: (1) dissolving polyvinylpyrrolidone (PVP) in a mixed solvent to obtain a spinning template agent; the mixed solvent comprises at least two solvents, and the boiling point difference of the two solvents is 65-90°C; (2) adding stannous chloride dihydrate (SnCl2·2H2O) to the spinning template agent, stirring to obtain a precursor solution; (3) taking the precursor solution for electrospinning to obtain a spinning product; (4) taking the spinning product for calcination to obtain a SnO2 nanofiber material.

[0021] Step S2, preparing a gas sensing element slurry: The SnO2 nanofiber material prepared in step S1 is added into an organic solvent to obtain a coating slurry.

[0022] Step S3, preparing a gas sensor: The coating slurry prepared in step S2 is coated on the surface of a heated substrate to obtain a gas sensor.

[0023] In step S1, the long-chain molecular structure of PVP forms a three-dimensional network skeleton in the mixed solvent, and PVP is used as a spinning template agent. When SnCl2·2H2O is added, Sn 2+ ions are coordinated with the amide groups of PVP, and Sn 2+ is uniformly dispersed in the polymer network to form a stable precursor solution. Through the molecularly dispersed precursor solution, the uniformity of the final product composition is ensured. Then, through electrospinning, the formation of the fiber structure is promoted under the driving of the electric field, and due to the mixed solvent system of the high-boiling-point solvent and the low-boiling-point solvent, a gradient volatilization effect is generated during the spinning process, resulting in phase separation to form a hollow structure. Finally, through calcination, a SnO2 nanofiber material with a hollow tubular fiber structure is prepared. Due to the presence of the hollow tubular structure, sufficient and active reaction sites can be provided for capturing 3-vinylpyridine in the environment, thereby achieving sensitive detection of 3-vinylpyridine.

[0024] In steps S2 and S3, the slurry of the SnO2 nanofiber material is coated on the surface of a heated substrate to form a gas sensing element. Using SnO2 nanofiber material as the gas sensing element of the gas sensor can achieve high sensitivity and high accuracy detection in tobacco smoke environment tracing.

[0025] As a preferred embodiment of the above method, in step (1), the mixed solvent is N,N-dimethylformamide (DMF) and anhydrous ethanol mixed in a volume ratio of 1:0.5-1.

[0026] As a preferred embodiment of the above method, in step (1), the concentration of polyvinylpyrrolidone in the spinning template agent is 0.05-0.1 g / mL.

[0027] As a preferred embodiment of the above method, in step (2), the mass ratio of SnCl2·2H2O to polyvinylpyrrolidone in the precursor solution is 1.5-3:1.

[0028] As a preferred embodiment of the above method, in step (4), the calcination temperature is 500-600°C, and the calcination time is 1-10 hours.

[0029] As the above method is preferred, in step S2, the preparation method of the coating slurry is: according to the mass ratio of SnO2 nanofiber material: ethanol is 0.2~0.8:1, the SnO2 nanofiber material is mixed with ethanol uniformly, and the coating slurry is obtained.

[0030] Based on the above, the application provides an application of a gas sensor in detecting the content of 3-vinylpyridine in a gas environment.

[0031] Compared with the prior art, the application has the following technical effects: (1) The application is a detection means based on a gas sensor, and the application realizes high sensitivity and high accuracy detection in tobacco smoke environment tracing by taking 3-vinylpyridine as a detection object and providing a gas sensitive element SnO2 nanofiber material specifically matched therewith. The application realizes real-time detection of 3-vinylpyridine based on a gas sensor for the first time, has low detection limit, good stability, and high specificity, and meets the requirements of environmental smoke analysis. It is verified by experiments that even in an environmental gas with a concentration as low as 5 ppm, the SnO2 nanofiber material can also show a large resistance value change signal, which reflects a very high sensitive performance to the concentration change of 3-vinylpyridine gas.

[0032] (2) The gas sensor of the application traces the tobacco smoke in the environment, which is simple to operate, does not need to pretreat the environmental smoke, and does not need to post-treat the detection sample such as solvent analysis or thermal desorption, and has the advantage of short detection time compared with the existing detection methods, and can realize detection at any time.

[0033] (3) The application realizes the preparation of the SnO2 nanofiber material with a hollow tubular fiber structure by taking PVP as a precursor solution and by electrospinning technology in a mixed solvent with a boiling point difference. Due to the existence of the hollow tubular structure, enough and active reaction sites can be provided for capturing 3-vinylpyridine in the environment, so as to realize sensitive detection of 3-vinylpyridine.

[0034] (4) The SnO2 nanofiber material with a hollow tubular fiber structure prepared by the application has high stability, and can realize continuous and multiple stable detection of 3-vinylpyridine by the gas sensor. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The figure shows the SEM pattern of the SnO2 nanofiber film material prepared in Example 1 of the application.

[0036] Figure 2The figure shows the structure of the gas sensor for detecting 3-vinylpyridine in real time according to the present application, wherein 1 represents a nickel-chromium heating wire, 2 represents a platinum wire, 3 represents an Al2O3 ceramic tube, 4 represents a SnO2 nanofiber film, 5 represents a gold electrode, and 6 represents a plug-in electrode.

[0037] Figure 3 The figure shows the sensing response results of the gas sensor with the SnO2 nanofiber film as the gas-sensitive element to 3-vinylpyridine in the concentration range of 5-50 ppm, wherein a shows the response results of the gas sensor under different concentrations of 3-vinylpyridine in the range of 5-50 ppm, and b shows the fitting curve of the response value peak with the concentration under different concentrations of 3-vinylpyridine.

[0038] Figure 4 The figure shows the working temperature-sensitivity curve of the gas sensor with the SnO2 nanofiber film as the gas-sensitive element under the atmosphere of 3-vinylpyridine at a concentration of 35 ppm.

[0039] Figure 5 The figure shows the response selectivity of the gas sensor with the SnO2 nanofiber film as the gas-sensitive element to common harmful gases at a concentration of 50 ppm.

[0040] Figure 6 The figure shows the sensing response results of the gas sensor with the SnO2 nanofiber film as the gas-sensitive element to 3-vinylpyridine for six times in succession. DETAILED DESCRIPTION

[0041] In the present application, the response of the resistance change signal generated by the gas-sensitive element in the gas sensor after adsorbing 3-vinylpyridine can be detected by the existing technology, for example, by connecting a sensing circuit, giving a specific voltage to both ends of the gas sensor, and calculating the response value of the resistance value change generated by the gas-sensitive element in the gas sensor after adsorbing 3-vinylpyridine through the current change of the detection circuit. The response value is: ; wherein S represents the response value of the gas sensor, Ra and Rg represent the resistance values of the gas sensor in the air and in the environment of the gas to be tested, respectively. Ra is a constant value.

[0042] In practical applications, the fitting curve of the response value peak with the concentration under different concentrations of 3-vinylpyridine is prepared as a standard curve, and then the response value of the environment to be tested is detected by the gas sensor provided by the present application, so that the concentration of 3-vinylpyridine in the environment to be tested can be calculated through the standard curve. For example, Figure 3The fitting curve shown in Figure b of the drawing is a fitting curve of the peak value of the response value of 3-vinylpyridine at different concentrations of 5-50 ppm, which can be used as a standard curve for the detection of 3-vinylpyridine at 5-50 ppm.

[0043] The application will be further described in conjunction with the following examples. Those skilled in the art will be able to implement the application based on these descriptions. In addition, the examples of the application described in the following description are generally only examples of a part of the application, not all examples. Therefore, all other examples obtained by those skilled in the art based on the examples in the application without creative labor should be within the scope of protection of the application.

[0044] Example 1 A gas sensitive element material is provided, which is prepared according to the following steps: (1) 10 mL of DMF and 8 mL of anhydrous ethanol are mixed to prepare a mixed solvent, and then 1.2 g of PVP is dissolved in the mixed solvent to prepare a spinning template agent; (2) 2.8 g of SnCl2·2H2O is added to the spinning template agent in step (1), and stirred for 12 h to form a spinning solution; (3) The mixed spinning solution in step (2) is injected into a glass syringe with a capacity of 10 mL for electrospinning, and the operation process parameters are: electrospinning voltage is 18 kV, and injection speed is 1.2 mL / h. During the electrospinning process, the distance between the glass syringe and the collection roller covered with aluminum-plated paper is set to 18 cm.

[0045] (4) The product obtained by electrospinning in step (3) is dried in an oven at 80℃ for 0.5 h.

[0046] (5) The dried product obtained by electrospinning is placed in a tube furnace under air atmosphere, and the temperature is raised to 550℃ at a rate of 2℃ / min, and then calcined at 550℃ for 2 h to obtain SnO2 nanofiber material with hollow tubular fiber structure.

[0047] (6) The SnO2 nanofiber material obtained in step (5) is observed by electron microscopy, and the results are shown in Figure 1 , Figure 1 Figure a is an electron micrograph at a scale of 1 μm, and Figure b is an electron micrograph at a scale of 5 μm. The results show that the prepared SnO2 nanofiber material has a hollow tubular fiber structure.

[0048] Example 2 A gas sensitive element material is provided, which is prepared according to the following steps: (1) 10 mL DMF and 5 mL anhydrous ethanol were mixed to prepare a mixed solvent, and then 0.75 g PVP was dissolved in the mixed solvent to prepare a spinning template agent; (2) 1.2 g SnCl2·2H2O was added to the spinning template agent in step (1), and stirred for 12 h to form a spinning solution; (3) The mixed spinning solution in step (2) was injected into a glass syringe with a capacity of 10 mL for electrospinning, and the operation process parameters were as follows: the electrospinning voltage was 18 kV, and the injection speed was 1.2 mL / h. During the electrospinning process, the distance between the glass syringe and the collection roller covered with aluminum-plated paper was set to 18 cm.

[0049] (4) The product obtained by electrospinning in step (3) was dried in an oven at 80°C for 1 h.

[0050] (5) The dried product obtained by electrospinning was placed in a tube furnace under an air atmosphere, and the temperature was raised to 520°C at a rate of 2°C / min, and then calcined at 520°C for 3 h to obtain a SnO2 nanofiber material with a hollow tubular fiber structure.

[0051] (6) The SnO2 nanofiber material obtained in step (5) was observed by electron microscopy, and the results showed that the prepared SnO2 nanofiber material had a hollow tubular fiber structure.

[0052] Example 3 A gas sensitive element material is provided, which is prepared according to the following steps: (1) 10 mL DMF and 10 mL anhydrous ethanol were mixed to prepare a mixed solvent, and then 2.0 g PVP was dissolved in the mixed solvent to prepare a spinning template agent; (2) 6.0 g SnCl2·2H2O was added to the spinning template agent in step (1), and stirred for 15 h to form a spinning solution; (3) The mixed spinning solution in step (2) was injected into a glass syringe with a capacity of 10 mL for electrospinning, and the operation process parameters were as follows: the electrospinning voltage was 18 kV, and the injection speed was 1.2 mL / h. During the electrospinning process, the distance between the glass syringe and the collection roller covered with aluminum-plated paper was set to 18 cm.

[0053] (4) The product obtained by electrospinning in step (3) was dried in an oven at 80°C for 0.5 h.

[0054] (5) The electrospun product after drying is taken out and put into a tube furnace under an air atmosphere, and the temperature is raised to 580°C at a rate of 2°C / min, and then calcined at 580°C for 2 hours to obtain a SnO2 nanofiber material with a hollow tubular fiber structure.

[0055] (6) The SnO2 nanofiber material obtained in step (5) is observed by electron microscopy, and the results show that the prepared SnO2 nanofiber material has a hollow tubular fiber structure.

[0056] Example 4 A gas sensitive element material is provided, and is prepared according to the following steps: (1) 10 mL of DMF and 8 mL of water are mixed to obtain a mixed solvent, and then 1.2 g of PVP is dissolved in the mixed solvent to obtain a spinning template agent after mixing; (2) 2.8 g of SnCl2·2H2O is added to the spinning template agent in step (1), and stirred for 12 h to form a spinning solution; (3) The mixed spinning solution in step (2) is injected into a glass syringe with a capacity of 10 mL for electrospinning, and the operation process parameters are: the electrospinning voltage is 18 kV, and the injection speed is 1.2 mL / h. During the electrospinning process, the distance between the glass syringe and the collection roller covered with aluminum-plated paper is set to 18 cm.

[0057] (4) The electrospun product obtained in step (3) is dried in an oven at 80°C for 0.5 hours.

[0058] (5) The electrospun product after drying is taken out and put into a tube furnace under an air atmosphere, and the temperature is raised to 580°C at a rate of 2°C / min, and then calcined at 580°C for 2 hours to obtain a SnO2 nanofiber material with a hollow tubular fiber structure.

[0059] (6) The SnO2 nanofiber material obtained in step (5) is observed by electron microscopy, and the results show that the prepared SnO2 nanofiber material has a hollow tubular fiber structure.

[0060] Example 5 A gas sensor for real-time detection of 3-vinylpyridine content is provided, and the gas sensitive element materials obtained in examples 1 to 4 are taken respectively, and prepared according to the following steps: Step S1, take the gas sensitive element material, gently grind in a mortar for 5 minutes, mix the gas sensitive element material with anhydrous ethanol according to a mass ratio of 0.5:1 to obtain a paste-like slurry.

[0061] Step S2, this step provides a gas sensor, which comprises a heating substrate and a gas sensitive element arranged on the heating substrate. The heating substrate comprises an Al2O3 ceramic tube 3, a heating coil 1 arranged in the Al2O3 ceramic tube 3, and an electrode 5 arranged on the Al2O3 ceramic tube. The structural schematic diagram is shown in the left drawing of Figure 2 .

[0062] This step coats the paste slurry obtained in step S1 on the outer surface of the Al2O3 ceramic tube 3, and after drying, a thin film layer, i.e., a SnO2 nanofiber thin film 4, is formed. Then, the gas sensitive element is welded and packaged according to a side heating type, the heating coil 1 arranged in the Al2O3 ceramic tube 3 and the electrode 5 arranged on the Al2O3 ceramic tube are connected, and a gas sensor with a structural schematic diagram as shown in the left drawing of Figure 2 is obtained. The heating coil 1 is a nickel-chromium heating coil with 30 turns (resistance value: 25-35 Ω), and the electrode 5 is a gold electrode.

[0063] Then, as shown in the right drawing of Figure 2 , the obtained gas sensor is connected to a plug-in electrode 6, and a voltage of 3.4 V is applied to both ends to age for one week to enhance the stability.

[0064] Step S3, according to steps S1 and S2, SnO2 nanofiber thin films 4 are prepared by using the SnO2 nanofiber materials obtained in examples 1 to 4 to obtain gas sensors, which are numbered as gas sensor 1, gas sensor 2, gas sensor 3, and gas sensor 4.

[0065] Example 6 The gas sensor obtained in example 5 is subjected to response detection in different gas environments, and the process is as follows: After the gas sensor is connected to the plug-in electrode 6, the plug-in electrode 6 is connected to a sensing circuit, and the sensing circuit is connected to a computer end to form a complete detector. The computer end can process the current / resistance change signal of the complete detector and output the current / resistance change signal response value of the gas environment change. In this step, the gas sensor obtained in example 5 is subjected to response detection in different gas environments by using a WS-30A gas sensor measurement system (TS64, Zhengzhou Weisheng Electronic Technology Co., Ltd.).

[0066] The specific detection method in the actual gas environment is as follows: The heating coil 1 is heated by the circuit to make the gas sensor detect at the working temperature of 225℃, and the corresponding heating power is 0.52W and the heating voltage is 3.6V. In the working state of the gas sensor, after the baseline is stable in the debugging detection, the gas sensor is placed in the space with the gas environment to be tested, and the response value appears by starting the test, the inductive signal rises until the balance at the top, and then the signal decreases to the baseline after removing the gas environment to be tested. The response value is: ; In the formula, S represents the response value of the gas sensor, Ra and Rg represent the resistance values of the gas sensor in air and in the gas environment to be tested, respectively.

[0067] In this embodiment, an evaporation table is arranged in the gas environment to be tested. In order to realize the air environment gas atmosphere with different concentrations of 3-vinylpyridine in the test process, different volumes of 3-vinylpyridine solution are injected into the evaporation table, and 3-vinylpyridine gas is obtained by evaporation, so that the space of the gas environment to be tested contains different contents of 3-vinylpyridine. The sample amount is obtained according to the following formula: ; In the formula, V L is the injection amount of the solution (mL), V is the volume of the space of the gas environment to be tested (mL), C is the concentration of 3-vinylpyridine vapor (ppm), M is the molar mass of the liquid (g / mol), d is the specific gravity of the liquid (g / cm 3 ), p is the purity of the liquid, Tr is the room temperature (℃), and Tc is the temperature of the gas environment to be tested (℃).

[0068] The detection process of this embodiment shows that the gas sensing element of the gas sensor has high sensitivity, the gas sensing element and the gas adsorption time are short, and rapid detection response can be realized. The gas sensing element gas sensor is prepared by using the gas sensing element materials prepared in embodiments 1 to 4. The response peak value and the time to reach the peak value of the gas sensor in the 3-vinylpyridine gas environment of 30 ppm are shown in Table 1.

[0069] Table 1 Gas sensor Gas sensitive element material Response peak Time to peak (s) 1 Example 1 14 25 2 Example 2 14 26 3 Example 3 14 25 4 Example 4 10 30 The detection results of the gas sensor 1 in the 3-vinylpyridine sensing response in the concentration range of 5-50 ppm are shown in Figure 3 , Figure 3 , wherein a is the response peak value and the adsorption time of the gas sensor in the 3-vinylpyridine of 5-50 ppm, and b is the fitting curve of the response value peak value with the concentration in the different concentrations of 3-vinylpyridine.

[0070] From Figure 3It can be seen that the gas sensor has high sensitivity, short gas adsorption time and fast detection response. Figure 3 As shown in FIG. 2B, the gas sensor has good linearity in the 3-vinylpyridine concentration range of 5-50 ppm, R 2 =0.99489, and the detection limit is 1 ppm, indicating that the sensor can effectively and sensitively detect 3-vinylpyridine in a gas environment.

[0071] Example 7 The gas sensor 1 obtained in Example 5 was used to detect the response at different temperatures in an air environment containing 35 ppm of 3-vinylpyridine as the to-be-detected gas environment. The difference between the implementation and Example 6 is that the 3-vinylpyridine content of the to-be-detected gas environment is 35 ppm, and the working temperature of the gas sensor is 160°C, 180°C, 200°C, 225°C, 240°C or 280°C, respectively. The other implementation operations are the same as those in Example 6.

[0072] The detection results show that the response detection results at different temperatures in an air environment containing 35 ppm of 3-vinylpyridine as the to-be-detected gas environment are shown in FIG. 3B. Figure 4 .

[0073] The detection results show that the optimal working temperature of the gas sensor is 225°C.

[0074] Example 8 The gas sensor 1 obtained in Example 5 was used to detect the response at different temperatures in an air environment containing 50 ppm of different substances as the to-be-detected gas environment. The difference between the implementation and Example 6 is that the to-be-detected gas environment is an air environment containing 50 ppm of different substances. The different substances are ammonia, pyridine, glycerol, toluene, methanol, chloroform, 3-vinylpyridine and nicotine. The other implementation operations are the same as those in Example 6.

[0075] The detection results show that the response detection results at different temperatures in an air environment containing 50 ppm of different substances as the to-be-detected gas environment are shown in FIG. 4B. Figure 5 .

[0076] The detection results show that the response effect of the gas sensor on 3-vinylpyridine is much greater than that on other substances, and the response on the remaining substances is poor. The presence of 50 ppm of 3-vinylpyridine in air can cause a large change in the resistance value of the gas sensor and a large response value. The presence of 50 ppm of nicotine, pyridine, glycerol, toluene and other substances in air causes a small change in the resistance signal and a small response value.

[0077] Example 9 The gas sensor 1 obtained in Example 5 was subjected to sensing detection test in an air environment containing 50 ppm of 3-vinylpyridine as the gas environment to be detected, and was continuously measured for 6 times without interruption, and the operation was performed according to Example 6. In the test, the uninterrupted measurement means that the gas sensor is placed in a space with the gas environment to be detected in the working state of the gas sensor, and the test is started, the response value appears, the sensing signal rises until the peak balance is reached, then the gas environment to be detected is removed, the signal decreases to the baseline, and then the gas sensor is immediately placed in a space with the gas environment to be detected again for measurement, and the measurement is continuously performed for 6 times. The test results of this example are shown in Table 1. Figure 6 .

[0078] The detection results show that the response values between the 6 continuous measurements have no significant change, and the relative standard deviation is 2.514%, indicating that the gas sensor can realize continuous detection for multiple times in the detection environment.

[0079] The raw materials and equipment used in the present application are conventional raw materials and equipment in the art unless otherwise specified; the methods used in the present application are conventional methods in the art unless otherwise specified.

[0080] The above is only a preferred embodiment of the present application, and does not limit the present application in any way. Any simple modification, change and equivalent transformation of the above embodiment according to the technical essence of the present application still belongs to the protection scope of the technical solution of the present application.

Claims

1. A gas sensor for real-time detection of 3-vinylpyridine content, characterized in that: It includes a heating substrate and a gas sensing element arranged on the heating substrate; The gas sensor is made of SnO2 nanofiber material, which is used to specifically adsorb 3-vinylpyridine molecules in ambient smoke and generate a linear resistance change signal as the 3-vinylpyridine content changes.

2. A gas sensor for real-time detection of 3-vinylpyridine content according to claim 1, characterized in that: In the detection working state, the heating substrate is electrically heated to keep the temperature of the gas sensor at 170° C. to 240° C.

3. A gas sensor for real-time detection of 3-vinylpyridine content according to claim 1 or 2, characterized in that: In the detection working state, the heating substrate is electrically heated to keep the temperature of the gas sensor at 225°C.

4. A gas sensor for real-time detection of 3-vinylpyridine content according to claim 1, characterized in that: The heating substrate comprises an Al2O3 ceramic tube, a heating coil arranged in the Al2O3 ceramic tube and an electrode arranged on the Al2O3 ceramic tube.

5. A gas sensor for real-time detection of 3-vinylpyridine content according to claim 4, characterized in that: The gas sensor is arranged on the surface of the Al2O3 ceramic tube.

6. A method for preparing a gas sensor for real-time detection of 3-vinylpyridine content, characterized in that: The method comprises the steps of preparing a SnO2 nanofiber material and applying a slurry formed by the SnO2 nanofiber material to a surface of a heated substrate to form a gas sensor. The step of preparing the SnO2 nanofiber material comprises the following steps: (1) dissolving polyvinyl pyrrolidone in a mixed solvent to obtain a spinning template; the mixed solvent comprises at least two solvents, and the boiling point difference between the two solvents is 65-90°C; (2) adding stannous chloride dihydrate to the spinning template agent and stirring to obtain a precursor solution; (3) taking the precursor solution and performing electrospinning to obtain a spinning product; (4) The spinning product is calcined to obtain SnO2 nanofiber material.

7. The preparation method according to claim 6, wherein: In step (1), the mixed solvent is N,N-dimethylformamide and anhydrous ethanol mixed in a volume ratio of 1:0.5~1.

8. The preparation method according to claim 6, wherein: In step (2), in the precursor solution, the mass ratio of stannous chloride dihydrate to polyvinyl pyrrolidone is 1.5-3:

1.

9. The preparation method according to claim 6, wherein: In step (4), the calcination temperature is 500-600° C., and the calcination time is 1-10 hours.

10. Use of the gas sensor according to any one of claims 1 to 5 or the gas sensor prepared by the preparation method according to any one of claims 6 to 9 for detecting 3-vinylpyridine content in a gas environment.

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