| Functional ionic liquids with special physicochemical properties could be prepared by introducing functional groups to anion or cation of ionic liquids. Starting from the hydroxylamine (dimethyl amino ethanol, triethanolamine) and 1, 3-propane sultone, a series of hydroxyl and sulfonyl dual-functionalized zwitterionic salts were synthesized. Then dual-functionalized ionic liquids containing both hydroxyl and sulfonyl functional groups were produced successfully by zwitterionic salts and three kinds of strong acids (p-toluene sulfonic acid, trifluoromethanesulfonic acid, methanesulfonic acid) respectively. The structure of zwitterionic salts and dual-functional ionic liquids were confirmed by the 1H NMR and IR. The advantage of this synthetic method is simple and with high yield. The thermal decomposition temperatures of all the dual-functionalized ionic liquids which were detected by thermogravimetry analyzer were between 563K and 573K. As hydroxyl and sulfonyl dual-functionalized zwitterionic salts and ionic liquids, they may be used for synthesizing other functionalized ionic liquids or ionic liquid-polymer (polyelectrolyte).A novel amperometric humidity sensor with hydrophobic 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF6) ionic liquids as the sensing material, 7,7,8,8-tetracyanoquinodimethane (TCNQ) as electrochemical probe was demonstrated. To prepare the sensor, the BMIPF6 solution containing TCNQ was incorporated into the porous polyethylene membrane, and then closely mounted on the surface of sensor with three electrodes. The humidity sensor was operated with differential pulse voltammetry, cyclic voltammetry and square wave voltammetry, and the oxidation and reduction peak currents, as well as the charging currents of the voltammograms under different atmosphere were evaluated. Results showed that the first step redox behavior of TCNQ were stable under oxygen atmosphere. The diffusion coefficient of TCNQ in ionic liquid (BMIPF6) under dry nitrogen atmosphere increased 2.9 times than that under water saturation nitrogen atmosphere. The peak current response of sensor to relative humidity over 0% to 100% is linear. The charge current which was determinated by square wave voltammetry to relative humidity over 0% to 100% is also linear. Both currents could be used to detect relative humidity in atmosphere. The humidity sensor with a high sensitivity and an excellent reproducibility and short response time which was about 21-28s under water saturation nitrogen and 42-49s under dry nitrogen using square wave voltammetry, which make this novel amperometric electrochemical humidity sensor used in practical application.Mixture of BMIPF6 ionic liquid and acdic ionic liquid (triethyl(propyl-3-sulfonyl) ammonium methanesulfonate) was prepared. Membrane absorbing the mixture was covered on the surface of sensor with three electrodes. A new kind of oxygen sensor was developed. Oxygen was reduced to hydrogen peroxide which was produced by superoxide ion and proton, avoiding the affection of the strong oxidant, the superoxide ion, to the sensor. Due to the high viscosity of the mixture, the diffusion coefficient of oxygen in it became smaller than that in pure BMIPF6 ionic liquid and the reduction current of oxygen decreased and the response time was about 50s increased. Potential step chronoamperometry was used to characterize the steady reduction current of oxygen under different humidity and different concentration of oxygen. The concentration of oxygen was regulated by gas mixer and humidity of gas mixture was commanded by water saturated salt solution. Thus, with the humidity sensor and the oxygen sensor developed above, the sensor system could be used for determining both the relative humidity and oxygen concentration in atmosphere. |
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