Polyaniline composite gas-sensitive material as well as preparation method and application thereof

Abstract

The invention relates to a polyaniline composite gas-sensitive material which comprises a two-dimensional ordered macroporous polyaniline film, and the two-dimensional ordered macroporous polyaniline film is doped and compounded with noble metal to form a two-dimensional ordered macroporous polyaniline / noble metal composite gas-sensitive material. In a word, the gas-sensitive property of the pure polyaniline is improved through morphological control and precious metal modification, and the method has the advantages of high sensitivity to ammonia gas, short response recovery time and high selectivity, can effectively solve the problems of low sensitivity and poor selectivity of the pure polyaniline material, and has a very good application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor gas sensors, and particularly relates to a polyaniline composite gas-sensitive material and a preparation method and application thereof. BACKGROUND

[0002] Ammonia is a toxic gas with strong irritating odor, which can stimulate the skin and respiratory system. As an atmospheric and indoor pollutant, it has great harmfulness. When people are exposed to low-concentration NH3 for a long time, it will pose a serious threat to human health. Therefore, in recent years, it has become an urgent demand to develop a gas sensor that can reliably detect ammonia. Such a sensor is essential for monitoring these gases in various environments and is widely used in scenarios including industrial sites, medical facilities, and even daily life, which can effectively ensure personal safety and health.

[0003] Compared with commonly used metal oxide semiconductor materials, conductive polymers have good self-conductivity, easy synthesis, excellent redox reaction characteristics, and reversible doping-dedoping mechanism, etc. The materials prepared by these conductive polymers can work at room temperature, which significantly expands their application range. However, there are still some problems in their use, such as relatively low sensitivity and selectivity to target gases. Therefore, as a good sensing material, it still faces many challenges in practical application.

[0004] In order to meet the complexity and diversification of application scenarios, researchers are constantly exploring strategies to optimize the performance of conductive polymer gas sensors, such as controlling micro-morphology, constructing heterojunctions, and doping with noble metals. Controlling micro-morphology can not only increase the specific surface area of the material, provide more active sites to enhance gas adsorption capacity, but also optimize the electron transport path to promote the chemical reaction of gas and material surface. Noble metal (such as silver, gold, platinum, etc.) nanoparticles can significantly enhance the adsorption and reaction activity of the sensor to specific gases through catalytic effect, electronic sensitization effect and chemical modification, thereby improving its selectivity. However, there is no mature solution for practical gas sensors.

[0005] In order to overcome the above-mentioned shortcomings of existing polyaniline materials, such as low sensitivity, high working temperature and poor selectivity, there is an urgent need for a polyaniline composite gas-sensitive material and a preparation method and application thereof. The polyaniline nanosphere composite gas-sensitive material is prepared and can be applied to semiconductor gas sensors, effectively solving the above-mentioned problems. SUMMARY

[0006] Therefore, the present application provides a polyaniline composite gas sensitive material, a preparation method and application thereof, the gas sensitive performance of pure polyaniline is improved through morphology control and noble metal modification, and the polyaniline composite gas sensitive material has high sensitivity, fast response and recovery time and high selectivity for specific organic volatile gases, effectively solves the problems of low sensitivity, high working temperature and poor selectivity of the existing pure polyaniline material, and has great application prospect.

[0007] In order to achieve the above technical purpose, the specific technical scheme adopted by the present application is: The polyaniline composite gas sensitive material comprises a two-dimensional ordered macroporous polyaniline film, and the two-dimensional ordered macroporous polyaniline film is formed by doping and compounding of noble metals to form a two-dimensional ordered macroporous polyaniline / noble metal composite gas sensitive material.

[0008] The preparation method of the polyaniline composite gas sensitive material comprises the following steps: S1, a polystyrene emulsion with uniform particle size is prepared by an emulsion polymerization method, low-carbon alcohol solvent is first added to the polystyrene emulsion and ultrasonic treatment is performed, then the polystyrene mixed solution after ultrasonic treatment is extracted and slowly injected into a culture dish containing deionized water, and the polystyrene microspheres are spread on the water surface, so that a two-dimensional polystyrene (PS) photonic crystal template is prepared; S2, the water under the two-dimensional polystyrene (PS) photonic crystal template obtained in step S1 is extracted, aniline and ammonium persulfate (APS) are added as a precursor solution in the water layer under the film, and reaction is performed at low temperature, so that a two-dimensional PS photonic crystal / PANI film is obtained; S3, the two-dimensional PS photonic crystal / PANI film prepared in step S2 is added with a precursor solution containing noble metals to continue low-temperature polymerization, the carrier is used to transfer the liquid surface film by leaching, and the film is dried and solidified, so that a single-layer PANI / noble metal composite film is prepared, and then the above operation is repeated to obtain a multi-layer composite film; S4, the carrier after drying in step S3 is soaked in an excess amount of N,N-dimethylformamide (DMF) solution and sealed to remove the PS template, and after washing with hydrochloric acid-deionized water and drying, a polyaniline composite material with two-dimensional ordered macropores is obtained.

[0009] Further, in step S1, the amount of the polystyrene emulsion removed is 1-3 ml, the low-carbon alcohol solvent is any one of n-propanol and n-butanol, the amount of the low-carbon alcohol solvent is 0.5-3 ml, and the ultrasonic treatment time of the polystyrene emulsion after adding the solvent is 10-30 min.

[0010] Further, in step S2, the precursor solution contains 10-20 ml of aniline and 10-20 ml of ammonium persulfate (APS), and the reaction time in the low-temperature environment is 12-36 h.

[0011] Furthermore, in step S3, the precursor solution containing precious metals includes one or more of silver, gold, platinum, palladium and ruthenium, and the doping mass range of the precious metals is 0.1 wt% to 1.0 wt%.

[0012] Furthermore, the time for continuing the low-temperature polymerization after adding the noble metal precursor solution in step S3 is 12 to 36 hours.

[0013] Furthermore, the composite membrane in step S3 includes a three-layer membrane, a six-layer membrane and a nine-layer membrane.

[0014] Furthermore, in step S4, the carrier includes one of a glass slide and a flexible interdigitated electrode, the coating area of ​​the two-dimensional PS photonic crystal / PANI film on the carrier is 2 to 3 cm × 3 to 5 cm, the flexible interdigitated electrode includes a polyimide (PI) substrate, the substrate is plated with Au, and the electrode line width and spacing are both 50-200 μm.

[0015] Furthermore, the concentration of the hydrochloric acid solution used for washing in step S4 is 0.5M to 2M.

[0016] An application of the polyaniline composite gas-sensitive material as described above in a gas sensor.

[0017] The principle of the present invention is mainly based on the excellent conductive polymer, unique doping-dedoping mechanism and low production cost of two-dimensional ordered macroporous conductive polymer. The two-dimensional ordered macroporous conductive polymer has a large specific surface area and a special pore structure, so it has more active sites, thereby improving the sensitivity to gas. At the same time, the conductive polymer is modified with precious metal nanoparticles. The introduction of precious metals makes it easier to activate the target gas and promote its catalytic cracking. By reducing the activation energy of the surface reaction between the target gas and the adsorbed oxygen, the gas-sensitive reaction is made more sufficient and thorough. In addition, after the precious metal modification, the surface of the sensitive material will adsorb more chemical oxygen anions, and the thickness of the electron depletion layer will also be significantly deepened, showing better gas-sensing performance than a single conductive polymer material. At the same time, compared with the single conductive polymer material without morphology, the nanomaterial has a larger specific surface area, rich active sites, adjustable surface chemistry and higher reaction activity, which reduces the activation energy required for the reaction, thereby further improving the sensitivity and selectivity of the material to NH3, greatly improving the gas-sensing performance of the material.

[0018] By adopting the above technical solution, the present invention can also bring the following beneficial effects: 1. The polyamine composite gas sensitive material can obtain two-dimensional ordered macroporous structure polyamine, has larger specific surface area, rich active site, surface chemical controllable and higher reaction activity compared with pure polyamine, can effectively improve the gas sensitive performance of the material, and has simple operation, easy preparation and good repeatability, can significantly improve the sensitivity of the gas sensor for NH3 gas monitoring, and has very good production and application prospect.

[0019] 2. The polyamine composite gas sensitive material can obtain polyamine microsphere / gold composite gas sensitive material, the microsphere structure has no change before and after being combined with gold, maintains the original characteristics, not only improves the specific surface area to a certain extent, but also greatly improves the oxygen vacancy content, which is very beneficial to improving the gas sensitive performance of the material, and the combination of gold reduces the working temperature of the material and reduces the energy consumption, which is very suitable for large-scale promotion. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0021] Figure 1 is the SEM diagram of the polyamine composite gas sensitive material in example 1 in the present application; Figure 2 is the TEM diagram of the polyamine composite gas sensitive material in example 1 in the present application; Figure 3 is the sensitivity curve of the gas sensor prepared by the polyamine composite gas sensitive material in example 1 in the present application to 100ppm ammonia gas at the optimum working temperature; Figure 4 is the short-term repeatability curve of the gas sensor prepared by the polyamine composite gas sensitive material in example 1, example 2, example 3 and example 4 to 100ppm ammonia gas at the optimum working temperature; Figure 5 is the concentration gradient curve of the gas sensor prepared by the polyamine composite gas sensitive material in example 1, example 2, example 3 and example 4 to ammonia gas at the optimum working temperature; Figure 6 is the selectivity of the gas sensor prepared by the polyamine composite gas sensitive material in example 1, example 2, example 3 and example 4 to 100ppm different gases at the optimum working temperature. DETAILED DESCRIPTION

[0022] The embodiments of the present application will be described below in detail with reference to the accompanying drawings.

[0023] The above objects, features and advantages of the present application will become more apparent from specific description of embodiments of the present application referring to the attached drawings. The following description is of embodiments of the present application with reference to the drawings, in which like reference numerals refer to like elements throughout. The embodiments of the present application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art. Like reference numerals refer to like elements throughout. It will be appreciated that like reference numerals are used to denote like elements throughout the detailed description and drawings.

[0024] It is to be understood that the foregoing description is exemplary of the various aspects of embodiments described herein. Thus, various modifications can be made to the embodiments described and illustrated herein, without departing from the spirit and scope of the application. For example, the aspects described herein can be used in combination with each other and with other aspects not expressly described but which would still fall within the scope of the present application. Additionally, it is contemplated that each feature described herein can be implemented with or without other features already described, as well as, new features being added. Furthermore, it should be appreciated that layers and / or structures illustrated herein are exemplary

[0025] It is also to be understood that the above description is only illustrative of the aspects of the embodiments described herein. Numerous modifications can be made by those skilled in the art, without departing from the spirit and scope of the application.

[0026] Furthermore, in the following description, numerous specific details are set forth in order to provide a thorough understanding of the examples. However, it will be recognized by one skilled in the art that the aspects described herein can be practiced without these specific details. Example 1

[0027] As shown in Figure 1 and Figure 2 A polyaniline composite gas sensitive material includes a two-dimensional ordered macroporous polyaniline film, and the two-dimensional ordered macroporous polyaniline film is doped and compounded by a noble metal to form a two-dimensional ordered macroporous polyaniline / noble metal composite gas sensitive material.

[0028] A preparation method of a polyaniline composite gas sensitive material, comprising the following steps: preparing polyaniline by an emulsion polymerization method, and then preparing a polyaniline / silver composite material ammonia gas sensor by compounding the polyaniline with a noble metal, and the specific manufacturing process is as follows: S1, first, 0.25 g of sodium dodecyl sulfate, 20 g of styrene solution is added to 135 mL of deionized water and stirred for 15 min, heated to 80℃, then 0.20 g of potassium persulfate is added, and the reaction is continued in a water bath for 7 h to obtain a uniform particle size polystyrene (PS) emulsion; S2, add n-propanol, n-butanol solvent to the polystyrene emulsion obtained in step S1 and ultrasonic for 30 min. Extract the ultrasonic treated polystyrene mixture and slowly inject it into a petri dish containing deionized water, so that the polystyrene microspheres cover the water surface, and a two-dimensional polystyrene (PS) photonic crystal template is prepared; S3, the water under the two-dimensional PS photonic crystal template obtained in step S2 is extracted, 10 ml of aniline and 10 ml of ammonium persulfate (APS) are added as a precursor solution, and the reaction is carried out at low temperature for 12 h to obtain a two-dimensional PS photonic crystal / PANI film; S4, add 2.0 ml of silver nitrate solution to the film prepared in step S3 and continue to polymerize at low temperature for 12 h, transfer the liquid surface film by flexible electrode extraction and dry curing to prepare a single-layer PANI / noble metal composite film. In actual use, three-layer composite films are obtained by repeating the above operation.

[0029] S5, place the planar electrode after drying in step S4 in excess N,N-dimethylformamide (DMF) solution and seal to remove the PS template, and after washing with 1 M hydrochloric acid and deionized water and drying, a polyaniline / silver composite gas sensitive material is obtained. Example 2

[0030] Different from example 1, a two-dimensional macroporous polyaniline is prepared by an emulsion polymerization method, comprising the following steps: S1, first, 0.25 g of sodium dodecyl sulfate, 20 g of styrene solution is added to 135 mL of deionized water and stirred for 15 min, heated to 80℃, then 0.20 g of potassium persulfate is added, and the reaction is continued in a water bath for 7 h to obtain a uniform particle size polystyrene (PS) emulsion; S2, add n-propanol, n-butanol solvent to the polystyrene emulsion obtained in step S1 and ultrasonic for 30 min. Extract the ultrasonic treated polystyrene mixture and slowly inject it into a petri dish containing deionized water, so that the polystyrene microspheres cover the water surface, and a two-dimensional polystyrene (PS) photonic crystal template is prepared; S3, the water under the two-dimensional PS photonic crystal template obtained in step S2 is extracted, 10 ml of aniline and 10 ml of ammonium persulfate (APS) are added to the water layer under the film as a precursor solution, and then the reaction is carried out at low temperature for 12 h to obtain a two-dimensional PS photonic crystal / PANI film; S4, the film prepared in step S3 is transferred by immersion extraction through a flexible electrode and is dried and solidified to obtain a two-dimensional macroporous polyaniline material gas sensor. Example 3

[0031] Different from example 1, a pure polyaniline is prepared by an in-situ polymerization method, and then a polyaniline / silver composite material gas sensor is prepared by compounding with a noble metal, including the following steps: S1, a certain amount of deionized water is placed in a culture dish, 20 mL of hydrochloric acid (1 mol / L), 10 ml of aniline and 10 ml of ammonium persulfate (APS) are added to the water layer, and then the mixture is reacted at low temperature for 12 h to obtain a pure polyaniline film; S2, 2.0 ml of silver nitrate solution is added under the film prepared in step S1 to continue the low-temperature polymerization for 12 h, and then the liquid surface film is transferred by immersion extraction through a flexible electrode and is dried and solidified to prepare a polyaniline / noble metal composite film; S3, the liquid surface film is transferred by immersion extraction through a flexible electrode and is dried and solidified to obtain a polyaniline / silver composite material gas sensor. Example 4

[0032] A preparation method of a pure polyaniline gas-sensitive material, including the following steps: S1, a certain amount of deionized water is placed in a culture dish, 20 mL of hydrochloric acid (1 mol / L), 10 ml of aniline and 10 ml of ammonium persulfate (APS) are added to the water layer, and then the mixture is reacted at low temperature for 12 h to obtain a pure polyaniline film; S2, the liquid surface film is transferred by immersion extraction through a flexible electrode and is dried and solidified to obtain a pure polyaniline material gas sensor.

[0033] The two-dimensional ordered macroporous polyaniline / silver composite materials with different morphologies / dopings in example 1, example 2, example 3 and example 4 are detected by a WS-30A gas sensitive element tester, so as to obtain corresponding response values, and the data are shown in the following table: It can be concluded that the two-dimensional ordered macroporous polyaniline / silver composite material prepared in example 1 has the highest response value, that is, the two-dimensional ordered macroporous polyaniline / silver composite material prepared in example 1 has the highest sensitivity to ammonia gas, and is most suitable for use as a gas-sensitive material of an ammonia gas sensor.

[0034] The corresponding analysis is carried out on the two-dimensional ordered macroporous polyaniline / silver composite material of example 1 with the best gas-sensitive performance, and the analysis results are referred toFigures 1 to 6 wherein Figure 1 It is shown that the two-dimensional ordered macroporous polyaniline / silver composite material prepared by Example 1 exhibits a clear two-dimensional highly ordered structure.

[0035] Figure 2 It is shown that the two-dimensional ordered macroporous polyaniline / silver composite material prepared by Example 1 shows clear lattice fringes with a spacing of 0.1227 nm, 0.144 nm and 0.236 nm, respectively, corresponding to the (311), (220) and (111) planes of face-centered cubic Ag, respectively, confirming the presence of Ag nanoparticles, which is beneficial to improve the charge transport efficiency and increase the density of gas-sensitive active sites.

[0036] Figure 3 It is shown that the response recovery curve of the two-dimensional ordered macroporous polyaniline / silver composite material prepared by Example 1 at the optimum working temperature (room temperature) has a response time of 3 seconds and a recovery time of 56 seconds at room temperature. The response time is the time required to reach 90% of the change amount, and the change amount is the change in resistance value of the sensor from the initial resistance value in the atmosphere to the resistance value after reaching the equilibrium state in the target gas. The recovery time is the time required to reach 90% of the change amount, and the change amount is the change in resistance value of the sensor from the resistance value in the target gas to the resistance value after remaining stable in the environment.

[0037] By Figures 4 to 6 Comparative analysis of the four implementation cases shows that the semiconductor gas sensor prepared in Example 1 has a higher sensitivity to 100 ppm ammonia at room temperature, a faster response and recovery speed relative to the sensors prepared in the other three implementation cases, a better short-term repeatability to 100 ppm ammonia, a better positive correlation between the sensitivity and the concentration of different concentrations of gas, and a generally lower sensitivity to other gases of the same concentration, indicating that the sensor in this example has a higher selectivity to the target gas. The sensor prepared in Example 1 has a larger specific surface area and gas diffusion channel than the sensors prepared in the other three implementation cases, which is beneficial to the diffusion of gas to the surface of the gas-sensitive material, so it is fully demonstrated that the polyaniline composite gas-sensitive material of the present application has a large specific surface area, abundant active sites, controllable surface chemistry and high reactivity, which is beneficial to improve the gas-sensitive performance of the material. Moreover, the preparation method is simple, easy to prepare and has good repeatability. The prepared gas sensor has high sensitivity and selectivity, good airtightness, and in general, the prepared sensor has good gas-sensitive performance and can meet the actual use. The present application has the advantages of high sensitivity to organic volatile gases, fast response and recovery time and high selectivity, and has a very good popularization space.

[0038] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A polyaniline composite gas-sensitive material, characterized by: The invention comprises a two-dimensional ordered macroporous polyaniline film, wherein the two-dimensional ordered macroporous polyaniline film is compounded by doping with noble metals to form a two-dimensional ordered macroporous polyaniline / noble metal composite gas-sensitive material.

2. A method for preparing the polyaniline composite gas-sensitive material according to claim 1, characterized in that: The steps are as follows: S1. Prepare a polystyrene emulsion with uniform particle size using emulsion polymerization. First, add a low-carbon alcohol solvent to the polystyrene emulsion and sonicate. Then, extract the sonicated polystyrene mixture and slowly inject it into a culture dish filled with deionized water until the polystyrene microspheres cover the water surface, thereby preparing a two-dimensional polystyrene (PS) photonic crystal template. S2, extracting the water under the two-dimensional polystyrene (PS) photonic crystal template obtained in step S1, adding aniline and ammonium persulfate (APS) as precursor solutions to the water layer under the membrane, and reacting them at low temperature to obtain a two-dimensional PS photonic crystal / PANI film; S3, adding a precursor solution containing a noble metal under the two-dimensional PS photonic crystal / PANI film prepared in step S2 to continue low-temperature polymerization, transferring the liquid surface film by carrier leaching and drying and solidifying to obtain a single-layer PANI / noble metal composite film, and then repeating the above operation to obtain a multi-layer composite film; S4. Place the carrier dried in step S3 in an excess of N,N-dimethylformamide (DMF) solution to immerse and seal to remove the PS template. After washing with hydrochloric acid-deionized water and drying, a polyaniline composite material with two-dimensional ordered macropores is obtained.

3. The method for preparing a polyaniline composite gas-sensitive material according to claim 2, wherein: In step S1, the amount of polystyrene emulsion pipetted is 1-3 ml, the low-carbon alcohol solvent is any one of n-propanol and n-butanol, the amount of low-carbon alcohol solvent used is 0.5-3 ml, and the polystyrene emulsion is ultrasonically treated for 10-30 minutes after adding the solvent.

4. The method for preparing a polyaniline composite gas-sensitive material according to claim 3, wherein: The precursor solution added in step S2 contains 10-20 ml of aniline and 10-20 ml of ammonium persulfate (APS), and the reaction time is 12-36 hours under a low temperature environment.

5. The method for preparing a polyaniline composite gas-sensitive material according to claim 4, wherein: The precursor solution containing precious metals added in step S3 includes one or more of silver, gold, platinum, palladium and ruthenium, and the doping mass range of the precious metals is 0.1 wt% to 1.0 wt%.

6. The method for preparing a polyaniline composite gas-sensitive material according to claim 5, wherein: The time for continuing the low-temperature polymerization after adding the noble metal precursor solution in step S3 is 12 to 36 hours.

7. The method for preparing a polyaniline composite gas-sensitive material according to claim 6, wherein: The composite membrane in step S3 includes a three-layer membrane, a six-layer membrane and a nine-layer membrane.

8. The method for preparing a polyaniline composite gas-sensitive material according to claim 7, wherein: The carrier in step S4 is one of a glass slide and a flexible interdigitated electrode. The coating area of ​​the two-dimensional PS photonic crystal / PANI film on the carrier is 2 to 3 cm × 3 to 5 cm. The flexible interdigitated electrode comprises a polyimide (PI) substrate coated with Au. The electrode line width and spacing are both 50-200 μm.

9. The method for preparing a polyaniline composite gas-sensitive material according to claim 8, wherein: The concentration of the hydrochloric acid solution used for washing in step S4 is 0.5M to 2M.

10. Use of the polyaniline composite gas-sensitive material according to claim 1 in a gas sensor.

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