The Construction And Application Of Ionic Liquid Composites In The Gas Sensor Array

Human health is threatened by the volatile organic compounds (VOCs) and other toxic gases. There is a critical need for good performance, portable, sensitive, fast and low cost gas sensors. Gas sensing material with excellent performance is an important prerequisite for gas sensing technology. At present, the commercial gas sensors are usually used to detect sole gas, rether than mixed one. In order to improve the recognization ability for mixed gases, the gas sensor array techonology received extensive attention of scientists. The physicochemical properties of ionic liquids (ILs), which are made up of anions and cations, can be tuned by adjusting the anion cation pair, resulting in diverse structures. It provides possibility for constructing an array to enhance selectivity of gas sensor. The ILs also have good conductivity and stability. Therefore, ILs have great application potential in electrical gas sensor.(1) This thesis reviewed the classification of gas sensor based on different detection principle, the research progress of gas sensitive materials used in the electrical gas sensor and the development of ionic liquids.(2) A chemiresistive sensor array consisting of ionogels was constructed to detect VOCs. ILs, as the sensing materials, also provide selectivity for different VOCs. But liquid ILs are not convenient to construct sensors. So ILs are confined in silica gel retaining the good conductivity by sol-gel method to improve the possibility of ILs in gas sensor. The sensing mechanism of the ionogels was based on the change in ion mobility responding to the absorption of VOCs. This mechanism significantly differed from the currently used chemiresistive sensors, usually relying on the modulation of charge densities. When the ILs exposured to VOCs, the visconsity decreased resulting in the increase of the ion mobility and current. A chemiresistive sensor array comprising nine types of ionogels with diverse chemical structures can generate a pattern of cross-reactive responses to a specific vapor because of the specific molecular interaction between ionic liquids and the target organic vapor, thereby leading to the discrimination of VOCs using principal component analysis.(3) A flexible reduced graphene oxide-ionic liquids (rGO-ILs) sensing array has been fabricated by a simple method. The ILs were modificated on rGO surface to combine the high sensitivity of graphene with selectivity of ILs, resulting in enhancing recognization ability of the rGO-ILs composites. The modification of ILs changed the response behavior of rGO to gases possibly because that ILs changed the band gap of rGO. The mechanism of the relationship between rGO-ILs composites and gases was discussed in detail in this paper, that was the synergy of the intro-sheet effect and inter-sheet effect. Meanwhile, rGO surface modification improved the performance of the reversibility, solving the problem of poor reversibility in the area of graphene’s application in gas sensing. The array can response to both inorganic gases and VOCs. At last, PCA method was used to recognise the gases.