Modified Polyaniline For The Application In Gas Sensing

Conductive polymers(CP)can change their electrical conductivity through exposure to different types of gas.For this reason we use CP as materials for prepare gas sensor.Among those conductive polymers,polyaniline(PANI)has attracted much attention because of its unique conductive mechanism,ease of synthesis,environmental stability,and ease of processing.However,the PANI-based gas sensor still have many disadvantages such as low selectivity,poor environment stability,and many PANIbased sensors also strongly depends on the ambient humidity.In order to solve these problems,we optimized the performance about PANI by the following method in this paper.And explore the relationship between mechanism and nature through a series of characterized.1.Explored the self-assembly process of organic acids with different alkyl chain length on the surface of PANI film.Because PANI-based gas sensors usually show response to water molecules.In practical applications,when the concentration of the gas to be measured is too low,the response of the water molecule will seriously interfere the detection signal.In order to reduce the interference of water vapor,a layer of hydrophobic alkyl chain was modified on the membrane surface in this experiment.This experiment uses the "toluene-water" two-phase contact method to form an arrangement in which the carboxyl group is down and the alkyl group is up at the interface.Successfully modified the long-chain alkyl acid on the surface of polyaniline film.Considering various test environments and requirements,we designed three gas detection devices to meet different test requirements.2.Study on moisture resistance of polyaniline film gas sensor which selfassembled with long-chain alkyl acid.In order to explore the anti-humidity effect of the modified film,we did a series anti-humidity performance test about PANI films which modified with alkyl chains of different lengths.Through the calculated of the Young's equation and the Langmuir adsorption equation,we summarized the relationship between the alkyl acid modified chain length and the anti-humidity.3.Preparation of Polyaniline Nanowire Array and Exploration the gas sensitivity about MOF@PANIIn order to improve the response value of polyaniline to reduce interference,the commonly used method is to modify the functional group of selective response and add a second material to prepare a composite material.Therefore,in this experiment,we used two methods to optimize gas sensitivity: First,prepared one-dimensional polyaniline nanowires with high specific surface area,and modification with silane coupling agents to prepared nanowires arrays.The second methods is to use the threedimensional porosity of the metal-organic framework(MOF)to prepare MOF @ PANI core-shell structure composite materials,which prevent the phenomenon of reunite during prepared polyaniline by chemical oxidation method,and we use MOF to enrich the detected-gas to improve the response.And according to the time difference of gas absorption and desorption,the type of gas can be distinguished from the aspect of molecular movement diameter.