Based On Room Temperature Ionic Liquid Conductivity Type Gas Sensor

Gas sensors have attracted many attentions due to their potential applications in environment protection, mass production control and clinic diagnosis etc. One of the hot points in the studies of gas sensors is to find out the new sensing material. Ionic liquids are the liquids at room temperature which contain essentially only ions. The ionic liquids show high ionic conductivity, low vapor pressure, low combustibility, excellent thermal stability, a wide liquid range, and favorable solvating properties for diverse compounds, which might be used as a new kind of gas sensing material. This thesis focused on developing a new kind of conductivity gas sensors based on ionic liquid. Several interesting results as shown in follow were obtained.1. ) Two ionic liquids, 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6) and 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4) were successfully synthesized.2.)The influence of trance impurity on the conductivity of ionic liquids was investigated. Results suggested that the conductivity of the ionic liquid increased with the increasing of the concentration of the organic solvents in it, and the influence by the polar solvents is greater than that by nonpolar solvents. In addition, though the conductivity of ionic liquids increased with the temperature increasing, but the influence of the same impurity at different temperature are almost the same.3.)A novel gas sensor using room temperature ionic liquid, BmimPF6, as the sensing material was proposed based on the increasing of the ionic conductivity of BmimPF6 when it was exposed in humid or organic solvent vapor. This mple-structure sensor showed a good stability and wide linear range for humidity or organic solvent vapor detection. By chemometrics, the relationship between the impedance response of the sensor towards different kinds of saturated organic solvent vapors and the physicochemical property constants of the organic solvents was also studied.4.)Five different kinds ionic liquids were used for construct the gas sensors. These sensors showed quit different sensitivity toward the organic vapors. For example, the sensor using BmimPF6 showed largest sensitivity towards ethyl acetate, while which using EmimCF3SO3 showed largest sensitivity towards isopropanol. Such results suggested the possibility of using different ionic liquids to design sensor array for the Enose system.