An asymmetric polypyrrole nanopillar array thin film, its preparation method, and its application in gas sensors.

Abstract

This invention relates to an asymmetric polypyrrole nanopillar array thin film, its preparation method, and its application in gas sensors. The method includes the following steps: immersing a flexible, biodegradable porous filter membrane in a polymerization catalyst solution; adding a pyrrole dispersion dropwise to the polymerization catalyst solution with the porous filter membrane immersed in it, followed by freezing and static reaction; removing the reacted porous filter membrane, washing, and drying it; performing surface treatment on one side of the dried porous filter membrane; placing the surface-treated porous filter membrane in a solvent to remove the porous membrane, and then washing and drying it to obtain the asymmetric polypyrrole nanopillar array thin film, which is used to construct a gas sensor. Compared with existing technologies, the preparation method of this invention mainly involves impregnation and dropwise addition. Through simple dip-coating and oxygen plasma surface treatment steps, the asymmetric polypyrrole nanopillar array thin film is prepared without the need for prolonged ultrasonication, simplifying the process.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, specifically to an asymmetric polypyrrole nanopillar array thin film, its preparation method, and its application in gas sensors. Background Technology

[0002] Currently, a large number of commercial gas sensors have emerged, widely used in monitoring and managing industrial production processes, environmental pollutant emissions, and public health. However, gas sensors on the market still have significant shortcomings in terms of cost, power consumption, sensitivity, and manufacturing processes, and many problems urgently need to be solved. Currently, the sensitive materials used in gas sensors can be broadly classified into two categories: inorganic materials and organic materials. Research on inorganic gas-sensitive materials has been quite extensive. However, the preparation of materials such as zinc oxide, tin dioxide, and ferrous oxide, which are representative of inorganic gas-sensitive materials, is relatively complex, energy-intensive, and has limited applications.

[0003] Patent application CN102505124A discloses a polypyrrole nanopillar embedded nanopore array material. This material comprises a polypyrrole matrix with arrayed, permeable nanopores at both ends. Polypyrrole nanopillars are embedded within these nanopores, with gaps between the nanopillar faces and the inner walls of the nanopores. A concentric, solid polypyrrole-coated titanium dioxide nanotube composite array material is formed by electropolymerization using pulsed voltammetry, comprising titanium dioxide nanotubes, a polypyrrole nanofilm coating the outer wall of the nanotubes, and polypyrrole nanopillars embedded within the nanotube cavities. The polypyrrole nanopillar embedded nanopore array material is then obtained by completely removing the ordered titanium dioxide nanotube template using hydrofluoric acid via chemical etching. This polypyrrole nanopillar embedded nanopore array material is used as an electrode material for supercapacitors in electrochemical energy storage applications. In this scheme, the fabrication of nanopillar arrays requires the use of a hard template, titanium dioxide, and an additional etching process, which is very troublesome. Moreover, the final application is for energy storage materials.

[0004] Patent application CN112851968A discloses a method for preparing a one-dimensional conductive polymer nanoarray. The method involves modifying a silicon pillar array; preparing a dispersion; pretreating a substrate; dropping the dispersion onto the surface of the modified silicon pillar array; covering the surface of the silicon pillar array with the substrate and applying pressure to press the two together; then drying the pressed silicon pillar array and substrate at a specific temperature to obtain a one-dimensional conductive polymer nanoarray. Using a pre-designed silicon pillar array, the conductive polymer dispersion is induced to self-assemble in a confined manner on various substrate surfaces, resulting in a one-dimensional nanowire array with precisely controlled position and shape. This method also requires the silicon pillar array as a hard template. Summary of the Invention

[0005] The purpose of this invention is to overcome at least one of the defects of the prior art and provide an asymmetric polypyrrole nanopillar array thin film, which is simple, efficient, controllable, and easy to implement without the need for a hard template, as well as its preparation method and its application in gas sensors.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] The inventors learned that organic materials, especially conductive polymers, are favored by researchers in the field of sensing due to their advantages such as flexibility, tunable conductivity, and good biocompatibility. Nanoscale one-dimensional conductive polymers can promote charge transport along the long axis, thereby achieving high sensitivity in sensors.

[0008] Therefore, developing nanostructured polymer materials holds promise for realizing gas sensors with high sensitivity and selectivity. Polypyrrole, as a typical conductive polymer, is simple to prepare, has a controllable structure, good conductivity, and a rapid response to ammonia, making it widely used in the field of gas sensors. Asymmetric thin-film structures, including porous films and arrays of hollow tubes on the film, provide ultra-high contact surface area, which can significantly improve the sensitivity of gas sensors.

[0009] This invention provides a simple, efficient, and controllable method for preparing asymmetric polypyrrole nanopillar array films. By immersing a porous polycarbonate membrane in a ferric chloride solution and then adding a pyrrole dispersion, a symmetrical polypyrrole nanopillar array can be formed. After oxygen plasma surface treatment and removal of the template, an asymmetric polypyrrole nanopillar array film can be obtained. This asymmetric film can be used to construct an ultrasensitive ammonia gas sensor. The specific method is as follows:

[0010] A method for preparing an asymmetric polypyrrole nanopillar array thin film, the method comprising the following steps:

[0011] The flexible biodegradable porous filter membrane is immersed in the polymerization catalyst solution;

[0012] The pyrrole dispersion was added dropwise to a polymerization catalyst solution that had been soaked in a porous filter membrane, and then the mixture was frozen and allowed to stand for reaction.

[0013] Remove the porous filter membrane after the reaction, and wash and dry it;

[0014] One side of the dried porous filter membrane is surface treated;

[0015] The surface-treated porous filter membrane was placed in a solvent to remove the porous filter membrane. After washing and drying, an asymmetric polypyrrole nanopillar array film was obtained.

[0016] Furthermore, the biodegradable porous filter membrane includes a polycarbonate filter membrane;

[0017] The preparation process of pyrrole dispersion is as follows: pyrrole monomer is mixed with a protic acid aqueous solution to obtain a pyrrole monomer solution;

[0018] The polymerization catalyst solution includes acidic iron salt solution, ammonium persulfate solution, or hydrogen peroxide solution;

[0019] The solvents include dichloromethane, water is used for washing, and ethanol is used for rinsing.

[0020] Furthermore, the biodegradable porous filter membrane is a polycarbonate filter membrane; the protic acid includes hydrochloric acid; and the polymerization catalyst solution is an acidic iron salt solution.

[0021] Furthermore, the pore size of the polycarbonate filter membrane is 0.05-20 μm, preferably 0.2-2 μm; different pore sizes of polycarbonate porous membranes can be selected, and the pore size of the resulting polypyrrole array will change accordingly.

[0022] In the pyrrole dispersion, the ratio of pyrrole monomer to hydrochloric acid aqueous solution is (50-400) μL: 15 mL, the concentration of hydrochloric acid is 0.1-1 M, and the concentration of pyrrole monomer is 0.1-0.4 M; the amount of pyrrole monomer used is 50-400 μL. Under certain conditions of pyrrole dispersion, the thickness of the polypyrrole layer will increase with the increase of pyrrole concentration.

[0023] In the acidic ferric salt solution, the ratio of ferric salt to acid is (0.1-1) g: 15 mL, the acid concentration is 0.1-1 M, and the ferric salt concentration is 0.1-0.4 M. This invention uses a polycarbonate porous membrane as a template for forming a polypyrrole hollow nanopillar array. Ferric chloride at concentrations of 0.1-0.4 M can be used to polymerize pyrrole. The conductivity of the polypyrrole nanopillar array film prepared with different concentrations of ferric chloride varies. As the ferric chloride concentration decreases, the polymerization rate slows down, the polypyrrole chains lengthen, and the conductivity increases.

[0024] The volume ratio of pyrrole dispersion to acidic ferric salt solution is (50-1000) μL:(3-5) mL. The amount of pyrrole dispersion used is 50-1000 μL. The pyrrole monomer dispersion is added dropwise to a ferric chloride solution impregnated with a polycarbonate porous membrane. Under the action of π-π bonds and hydrogen bonds, the pyrrole monomer spontaneously attaches to the surface and pores of the polycarbonate membrane, and is oxidized by ferric chloride to form a polypyrrole layer on the surface and within the pores of the polycarbonate porous membrane. The thickness of the polypyrrole layer increases with the increase of the amount of pyrrole dispersion used.

[0025] Furthermore, in the acidic iron salt solution, the iron salt is ferric chloride, and the acid is hydrochloric acid.

[0026] Furthermore, the surface treatment is oxygen plasma surface treatment, specifically under the following conditions: an oxygen atmosphere, a gas flow rate of 60-100 mL / min (preferably 80 mL / min), a power of 80-120 W (preferably 100 W), and a treatment time of 12-25 min. Oxygen plasma surface treatment can thin the membrane by removing the polypyrrole layer on one side of the porous membrane. The treatment time is selected based on the thickness of the polypyrrole layer; the thicker the polypyrrole layer, the longer the treatment time.

[0027] Furthermore, during surface treatment, the porous filter membrane is laid flat on a glass slide and placed in a plasma cleaner for oxygen plasma surface treatment.

[0028] Furthermore, the time spent in the solvent shall not be less than 5 minutes, the number of cleaning and washing cycles shall not be less than 3, the freezing temperature shall be below 10°C, and the standing time shall not be less than 4 hours.

[0029] An asymmetric polypyrrole nanopillar array film prepared by the method described above.

[0030] An application of the asymmetric polypyrrole nanopillar array thin film as described above, which is used to construct a gas sensor.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] (1) The asymmetric thin film of the present invention uses a polycarbonate porous membrane as a template, and the asymmetric thin film structure can be obtained by impregnation and oxygen plasma treatment. The preparation is simple, efficient and easy to realize. Compared with the prior art (CN102505124A, CN102517638A), it is superior to the titanium dioxide template method and silicon template method in terms of both cost and process convenience.

[0033] (2) The preparation method of the present invention mainly involves impregnation and drop addition. Through simple dip coating and oxygen plasma surface treatment steps, an asymmetric polypyrrole nanopillar array film is prepared without the need for long-term ultrasound, which simplifies the process.

[0034] (3) The asymmetric thin film prepared by the present invention can be used to construct gas sensors, which are low in cost and high in efficiency. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating the preparation process of the asymmetric polypyrrole film in this invention.

[0036] Figure 2 The image shows a scanning electron microscope (SEM) image of the asymmetric polypyrrole film prepared from a 0.2 μm polycarbonate porous membrane in Example 1.

[0037] Figure 3The image shows a scanning electron microscope (SEM) image of the asymmetric polypyrrole film prepared from a 0.6 μm polycarbonate porous membrane in Example 2.

[0038] Figure 4 This is a scanning electron microscope image of the asymmetric polypyrrole film prepared from a 1 μm polycarbonate porous membrane in Example 3;

[0039] Figure 5 This is a scanning electron microscope image of the asymmetric polypyrrole film prepared from a 2μm polycarbonate porous membrane in Example 4;

[0040] Figure 6 The graph shows the resistance change of the asymmetric polypyrrole film after ammonia gas is introduced in Example 6. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0042] A method for preparing an asymmetric polypyrrole nanopillar array thin film, the method comprising the following steps:

[0043] A flexible, biodegradable porous filter membrane is immersed in a polymerization catalyst solution. The biodegradable porous filter membrane includes a polycarbonate filter membrane. The polymerization catalyst solution includes an acidic iron salt solution, an ammonium persulfate solution, or a hydrogen peroxide solution. The biodegradable porous filter membrane is a polycarbonate filter membrane. The protic acid includes hydrochloric acid. The polymerization catalyst solution is an acidic iron salt solution. The pore size of the polycarbonate filter membrane is 0.05-20 μm, preferably 0.2-2 μm. Different pore sizes of polycarbonate porous membranes can be selected, and the pore size of the resulting polypyrrole array will change accordingly. In the acidic iron salt solution, the ratio of iron salt to acid is (0.1-1) g:15 mL, the concentration of acid is 0.1-1 M, and the concentration of iron salt is 0.1-0.4 M. Using the polycarbonate porous membrane as a template for the formation of the polypyrrole hollow nanopillar array, 0.1-0.4 M ferric chloride can be selected to polymerize pyrrole. The conductivity of the polypyrrole nanopillar array film prepared with different concentrations of ferric chloride varies. As the concentration of ferric chloride decreases, the polymerization rate slows down, the polypyrrole chains lengthen, and the electrical conductivity increases. In acidic ferric salt solutions, the ferric salt is ferric chloride, and the acid is hydrochloric acid.

[0044] The pyrrole dispersion was added dropwise to a polymerization catalyst solution soaked in a porous filter membrane, and then frozen and allowed to stand for reaction. The preparation process of the pyrrole dispersion was as follows: pyrrole monomer was mixed with a protic acid aqueous solution to obtain a pyrrole monomer solution. In the pyrrole dispersion, the volume ratio of pyrrole monomer to hydrochloric acid aqueous solution was (50-400) μL:15 mL, the concentration of hydrochloric acid was 0.1-1 M, and the concentration of pyrrole monomer was 0.1-0.4 M. The amount of pyrrole monomer used was 50-400 μL. Under certain conditions of pyrrole dispersion, the thickness of the polypyrrole layer would increase with the increase of pyrrole concentration. The volume ratio of pyrrole dispersion to acidic iron salt solution was (50-1000) μL:(3-5) mL. The amount of pyrrole dispersion used is 50-1000 μL. The pyrrole monomer dispersion is added dropwise to a ferric chloride solution impregnating a polycarbonate porous membrane. Under the action of π-π bonds and hydrogen bonds, the pyrrole monomer spontaneously attaches to the surface and pores of the polycarbonate membrane, and is oxidized by ferric chloride to form a polypyrrole layer on the surface and within the pores of the polycarbonate porous membrane. The thickness of the polypyrrole layer increases with the amount of pyrrole dispersion used. The freezing temperature is below 10°C, and the standing time is not less than 4 hours.

[0045] Remove the porous filter membrane after the reaction, and wash and dry it; use clean water for washing, and wash and rinse at least 3 times.

[0046] One side of the dried porous filter membrane undergoes surface treatment. The surface treatment is oxygen plasma surface treatment, with the following conditions: oxygen atmosphere, gas flow rate of 60-100 mL / min (preferably 80 mL / min), power of 80-120 W (preferably 100 W), and treatment time of 12-25 min. Oxygen plasma surface treatment can thin the membrane by removing the polypyrrole layer on one side of the porous membrane surface. The treatment time is selected based on the thickness of the polypyrrole layer; the thicker the polypyrrole layer, the longer the treatment time. During surface treatment, the porous filter membrane is laid flat on a glass slide and placed in a plasma cleaner for oxygen plasma surface treatment.

[0047] The surface-treated porous filter membrane was immersed in a solvent to remove the porous membrane. After washing and drying, an asymmetric polypyrrole nanopillar array film was obtained, which was used to construct a gas sensor. The solvent included dichloromethane, and ethanol was used for washing. The immersion time in the solvent was no less than 5 minutes, and the washing and rinsing were performed no less than 3 times.

[0048] Typical operating methods, such as Figure 1 This includes the following steps:

[0049] Step 1: Dissolve a certain amount of ferric chloride in 15 mL of 0.1 M hydrochloric acid solution to obtain ferric chloride solution; the concentration of ferric chloride is 0.1-0.4 M.

[0050] Step 2: Take 3-5 mL of ferric chloride solution and immerse the polycarbonate porous membrane in the solution; the pore size of the polycarbonate porous membrane is 0.05-20 μm.

[0051] Step 3: Disperse a certain amount of pyrrole monomer evenly with 15 mL of hydrochloric acid solution to obtain a pyrrole dispersion; the concentration of the pyrrole dispersion is 0.1-0.4 M. The volume of the pyrrole dispersion used is 50-1000 μL.

[0052] Step 4: Take a certain amount of pyrrole dispersion and add it dropwise into the ferric chloride solution soaked in polycarbonate porous membrane, and place it in the refrigerator to stand for 4 hours;

[0053] Step 5: Remove the reacted polycarbonate porous membrane, wash it three times with deionized water, and place it in an oven to dry.

[0054] Step 6: Lay the dried porous membrane flat on a glass slide and place it in a plasma cleaner for oxygen plasma surface treatment; the plasma treatment atmosphere is oxygen, the gas flow rate is 80mL / min, the power is 100W, and the treatment time is 12-20 minutes.

[0055] Step 7: Immerse the oxygen plasma-cleaned membrane in dichloromethane for 5 minutes to remove the polycarbonate porous membrane template, then wash it three times in ethanol and dry it to obtain the asymmetric polypyrrole membrane, which can then be used to construct a gas sensor.

[0056] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail with reference to the following specific embodiments and the accompanying drawings.

[0057] Example 1

[0058] An asymmetric polypyrrole nanopillar array thin film and its preparation method are detailed below:

[0059] 1 g of ferric chloride was dissolved in 15 mL of 0.1 M hydrochloric acid solution to prepare a ferric chloride solution. A 0.2 μm pore size polycarbonate porous membrane was immersed in 3 mL of the ferric chloride solution. 200 μL of pyrrole monomer was evenly dispersed in 15 mL of hydrochloric acid solution to obtain a pyrrole dispersion. 200 μL of the pyrrole dispersion was added dropwise to the ferric chloride solution containing the polycarbonate porous membrane, and the mixture was placed in a refrigerator and allowed to stand for 4 hours. The reacted polycarbonate porous membrane was removed, washed three times with deionized water, and dried in an oven. The dried porous membrane was laid flat on a glass slide and subjected to oxygen plasma surface treatment for 15 minutes in a plasma cleaner. The membrane was then immersed in dichloromethane for 5 minutes to remove the polycarbonate porous membrane template. Finally, it was washed three times in ethanol and dried to obtain the final product. Figure 2 Asymmetric polypyrrole film.

[0060] Example 2

[0061] An asymmetric polypyrrole nanopillar array thin film and its preparation method are detailed below:

[0062] 0.5 g of ferric chloride was dissolved in 15 mL of 0.1 M hydrochloric acid solution to prepare a ferric chloride solution. A 0.6 μm pore size polycarbonate porous membrane was immersed in 3 mL of the ferric chloride solution. 200 μL of pyrrole monomer was evenly dispersed in 15 mL of hydrochloric acid solution to obtain a pyrrole dispersion. 200 μL of the pyrrole dispersion was added dropwise to the ferric chloride solution containing the polycarbonate porous membrane, and the mixture was placed in a refrigerator and allowed to stand for 4 hours. The reacted polycarbonate porous membrane was removed, washed three times with deionized water, and dried in an oven. The dried porous membrane was laid flat on a glass slide and subjected to oxygen plasma surface treatment for 18 minutes in a plasma cleaner. The membrane was then immersed in dichloromethane for 5 minutes to remove the polycarbonate porous membrane template. Finally, it was washed three times in ethanol and dried to obtain the final product. Figure 3 Asymmetric polypyrrole film.

[0063] Example 3

[0064] An asymmetric polypyrrole nanopillar array thin film and its preparation method are detailed below:

[0065] 0.5 g of ferric chloride was dissolved in 15 mL of 0.1 M hydrochloric acid solution to prepare a ferric chloride solution. A 1 μm pore size polycarbonate porous membrane was immersed in 5 mL of the ferric chloride solution. 200 μL of pyrrole monomer was evenly dispersed in 15 mL of hydrochloric acid solution to obtain a pyrrole dispersion. 200 μL of the pyrrole dispersion was added dropwise to the ferric chloride solution containing the polycarbonate porous membrane, and the mixture was placed in a refrigerator and allowed to stand for 4 hours. The reacted polycarbonate porous membrane was removed, washed three times with deionized water, and dried in an oven. The dried porous membrane was laid flat on a glass slide and subjected to oxygen plasma surface treatment in a plasma cleaner. The membrane was immersed in dichloromethane for 5 minutes to remove the polycarbonate porous membrane template, then washed three times in ethanol and dried to obtain the final product. Figure 4 Asymmetric polypyrrole film.

[0066] Example 4

[0067] An asymmetric polypyrrole nanopillar array thin film and its preparation method are detailed below:

[0068] 0.1 g of ferric chloride was dissolved in 15 mL of 0.1 M hydrochloric acid solution to prepare a ferric chloride solution. A 2 μm pore size polycarbonate porous membrane was immersed in 3 mL of the ferric chloride solution. 200 μL of pyrrole monomer was evenly dispersed in 15 mL of hydrochloric acid solution to obtain a pyrrole dispersion. 200 μL of the pyrrole dispersion was added dropwise to the ferric chloride solution containing the polycarbonate porous membrane, and the mixture was placed in a refrigerator and allowed to stand for 4 hours. The reacted polycarbonate porous membrane was removed, washed three times with deionized water, and dried in an oven. The dried porous membrane was laid flat on a glass slide and subjected to oxygen plasma surface treatment for 25 minutes in a plasma cleaner. The membrane was then immersed in dichloromethane for 5 minutes to remove the polycarbonate porous membrane template. Finally, it was washed three times in ethanol and dried to obtain the final product. Figure 5 Asymmetric polypyrrole film.

[0069] Example 5

[0070] An asymmetric polypyrrole nanopillar array thin film and its preparation method are detailed below:

[0071] 0.1 g of ferric chloride was dissolved in 15 mL of 0.1 M hydrochloric acid solution to prepare a ferric chloride solution. A 0.6 μm pore size polycarbonate porous membrane was immersed in 3 mL of the ferric chloride solution. 150 μL of pyrrole monomer was evenly dispersed in 15 mL of hydrochloric acid solution to obtain a pyrrole dispersion. 200 μL of the pyrrole dispersion was added dropwise to the ferric chloride solution containing the polycarbonate porous membrane, and the mixture was placed in a refrigerator and allowed to stand for 4 hours. The reacted polycarbonate porous membrane was removed, washed three times with deionized water, and dried in an oven. The dried porous membrane was laid flat on a glass slide and subjected to oxygen plasma surface treatment for 20 minutes in a plasma cleaner. The membrane was then immersed in dichloromethane for 5 minutes to remove the polycarbonate porous membrane template. It was then washed three times in ethanol and dried to obtain a similar membrane. Figure 3 Asymmetric polypyrrole film.

[0072] Example 6

[0073] An asymmetric polypyrrole nanopillar array thin film, its preparation method, and its application in a gas sensor are detailed below:

[0074] 0.1 g of ferric chloride was dissolved in 15 mL of 0.1 M hydrochloric acid solution to prepare a ferric chloride solution. A 1 μm pore size polycarbonate porous membrane was immersed in 3 mL of the ferric chloride solution. 200 μL of pyrrole monomer was evenly dispersed in 15 mL of hydrochloric acid solution to obtain a pyrrole dispersion. 200 μL of the pyrrole dispersion was added dropwise to the ferric chloride solution containing the polycarbonate porous membrane, and the mixture was placed in a refrigerator and allowed to stand for 4 hours. The reacted polycarbonate porous membrane was removed, washed three times with deionized water, and dried in an oven. The dried porous membrane was laid flat on a glass slide and subjected to oxygen plasma surface treatment for 20 minutes in a plasma cleaner. The membrane was then immersed in dichloromethane for 5 minutes to remove the polycarbonate porous membrane template. It was then washed three times in ethanol and dried to obtain an asymmetric polypyrrole film.

[0075] Take the asymmetric polypyrrole film prepared in the above steps, cut it into 0.5×0.5mm pieces, connect copper wires to both ends, with an electrode spacing of 0.4mm, place it on an alumina sheet, and connect the wires to form a gas-sensitive detector. Apply a bias voltage of 1V and introduce 45ppm ammonia gas, then measure the change in device resistance, as shown in the attached figure. Figure 6 As shown, when 45 ppm of ammonia gas is introduced, the current response is rapid and the change is obvious. After the ammonia gas is stopped, the current recovers quickly, and the rapid response and recovery are maintained when the gas is introduced again, demonstrating good gas-sensitive performance.

[0076] Example 7

[0077] An asymmetric polypyrrole nanopillar array thin film, its preparation method, and its application in a gas sensor are detailed below:

[0078] Step 1: Dissolve a certain amount of ferric chloride in 15 mL of 0.1 M hydrochloric acid solution to obtain a ferric chloride solution; the concentration of ferric chloride is 0.1 M.

[0079] Step 2: Take 3 mL of ferric chloride solution and immerse the polycarbonate porous membrane in the solution; the pore size of the polycarbonate porous membrane is 0.05 μm.

[0080] Step 3: Disperse a certain amount of pyrrole monomer evenly with 15 mL of hydrochloric acid solution to obtain a pyrrole dispersion; the concentration of the pyrrole dispersion is 0.1 M. The volume of the pyrrole dispersion used is 50 μL.

[0081] Step 4: Take a certain amount of pyrrole dispersion and add it dropwise into the ferric chloride solution soaked in polycarbonate porous membrane, and place it in the refrigerator to stand for 4 hours;

[0082] Step 5: Remove the reacted polycarbonate porous membrane, wash it three times with deionized water, and place it in an oven to dry.

[0083] Step 6: Lay the dried porous membrane flat on a glass slide and place it in a plasma cleaner for oxygen plasma surface treatment; the plasma treatment atmosphere is oxygen, the gas flow rate is 80 mL / min, the power is 100 W, and the treatment time is 12 minutes.

[0084] Step 7: Immerse the oxygen plasma-cleaned membrane in dichloromethane for 5 minutes to remove the polycarbonate porous membrane template, then wash it three times in ethanol and dry it to obtain the asymmetric polypyrrole membrane, which can then be used to construct a gas sensor.

[0085] Example 8

[0086] An asymmetric polypyrrole nanopillar array thin film, its preparation method, and its application in a gas sensor are detailed below:

[0087] Step 1: Dissolve a certain amount of ferric chloride in 15 mL of 0.1 M hydrochloric acid solution to obtain a ferric chloride solution; the concentration of ferric chloride is 0.4 M.

[0088] Step 2: Take 5 mL of ferric chloride solution and immerse the polycarbonate porous membrane in the solution; the pore size of the polycarbonate porous membrane is 20 μm.

[0089] Step 3: Disperse a certain amount of pyrrole monomer evenly with 15 mL of hydrochloric acid solution to obtain a pyrrole dispersion; the concentration of the pyrrole dispersion is 0.4 M. The volume of the pyrrole dispersion used is 1000 μL.

[0090] Step 4: Take a certain amount of pyrrole dispersion and add it dropwise into the ferric chloride solution soaked in polycarbonate porous membrane, and place it in the refrigerator to stand for 4 hours;

[0091] Step 5: Remove the reacted polycarbonate porous membrane, wash it three times with deionized water, and place it in an oven to dry.

[0092] Step 6: Lay the dried porous membrane flat on a glass slide and place it in a plasma cleaner for oxygen plasma surface treatment; the plasma treatment atmosphere is oxygen, the gas flow rate is 80 mL / min, the power is 100 W, and the treatment time is 20 minutes.

[0093] Step 7: Immerse the oxygen plasma-cleaned membrane in dichloromethane for 5 minutes to remove the polycarbonate porous membrane template, then wash it three times in ethanol and dry it to obtain the asymmetric polypyrrole membrane, which can then be used to construct a gas sensor.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing an asymmetric polypyrole nanopillar array thin film, characterized in that, The method includes the following steps: The flexible biodegradable porous filter membrane is immersed in the polymerization catalyst solution; The pyrrole dispersion was added dropwise to the polymerization catalyst solution soaked in the porous filter membrane, and then the mixture was frozen and allowed to stand for reaction. The freezing temperature was below 10°C and the standing time was not less than 4 hours. Remove the porous filter membrane after the reaction, and wash and dry it; One side of the dried porous filter membrane is surface treated; The surface-treated porous filter membrane was placed in a solvent to remove the porous filter membrane. After washing and drying, an asymmetric polypyrrole nanopillar array film was obtained. The preparation process of pyrrole dispersion is as follows: pyrrole monomer is mixed with a protic acid aqueous solution to obtain a pyrrole monomer solution; The biodegradable porous filter membrane is a polycarbonate filter membrane; The protic acid mentioned includes hydrochloric acid; The polymerization catalyst solution is an acidic iron salt solution; The pore size of the polycarbonate filter membrane is 0.2-2 μm; In the pyrrole dispersion, the ratio of pyrrole monomer to hydrochloric acid aqueous solution is (50-400) μL: 15 mL, the concentration of hydrochloric acid is 0.1-1 M, and the concentration of pyrrole monomer is 0.1-0.4 M. In an acidic iron salt solution, the ratio of iron salt to acid is (0.1-1) g: 15 mL, the concentration of acid is 0.1-1 M, and the concentration of iron salt is 0.1-0.4 M. The volume ratio of pyrrole dispersion to acidic iron salt solution is (50-1000) μL : (3-5) mL; The surface treatment is oxygen plasma surface treatment, with the following specific conditions: oxygen atmosphere, gas flow rate of 60-100 mL / min, power of 80-120 W, and treatment time of 12-25 min.

2. The method for preparing an asymmetric polypyrrole nanopillar array thin film according to claim 1, characterized in that, The solvents include dichloromethane, water is used for washing, and ethanol is used for rinsing.

3. The method for preparing an asymmetric polypyrrole nanopillar array thin film according to claim 1, characterized in that, In an acidic iron salt solution, the iron salt is ferric chloride and the acid is hydrochloric acid.

4. The method for preparing an asymmetric polypyrrole nanopillar array thin film according to claim 1, characterized in that, During surface treatment, the porous filter membrane is laid flat on a glass slide and placed in a plasma cleaner for oxygen plasma surface treatment.

5. The method for preparing an asymmetric polypyrrole nanopillar array thin film according to claim 1, characterized in that, The time spent in the solvent shall not be less than 5 minutes, and the number of cleaning and washing cycles shall not be less than 3.

6. An asymmetric polypyrrole nanopillar array thin film prepared by the method according to any one of claims 1-5.

7. An application of the asymmetric polypyrrole nanopillar array thin film as described in claim 6, characterized in that, This thin film is used to construct gas sensors.

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