Enhanced CO2 Sensing with Ionic Liquid Modified Electrospun Nanofibers: Effect of Ionic Liquid Type

摘要

High solubility of CO2(g) in ionic liquids has been reported many times. In addition, fluorination of ionic liquids increases the gas solubility. In this study, we gathered these two advantages exploiting the ionic liquids and perfluorocompounds in the same matrix for more sensitive determination of CO2(g). A ratiometric CO2 sensor based on the spectrophotometric signal change of bromothymol blue (BTB) is proposed. Effects of ionic liquids (ILs) with different anionic and cationic parts on the sensor signal intensity were tested. The ion pair form of the dye was encapsulated in ethyl cellulose (EC) matrix. The sensing agents were produced both in form of nanofibrous materials and continuous thin films. The nanofibers were fabricated by electrospinning technique. The ratiometric response to CO2 was monitored at 396 nm and 640 nm. The offered sensing material can be used for quantitative determination of carbon dioxide in the concentration range of 0.0-100.0% pCO(2). With respect to continuous thin films, the electrospun nanofibers offered enhanced sensitivity extending to 98% relative signal change, lower detection limits and shorter response times. BTB also satisfies best the requirement of a distinguishable color change with naked eye when encapsulated in nanofibers. The exploited ionic liquids enhanced the long-term stabilities of the sensing slides. Besides, they facilitated the fabrication of nano fibers providing an electrical conductivity in the polymer by the effect of ionic groups.