Ionic Liquids for Gas and Vapor Sensing Applications

Abstract

Robust miniaturized low-cost and low-power gas sensors that can accurately detect and quantify important gaseous analytes in real-time and be in continuous use are needed for a broad range of applications. In this book chapter, we discuss the challenges and requirements for real-time gas sensing. We focus on elucidating ionic liquids (ILs), the non-volatile environmentally benign media, and their multiple benefits for real-time gas sensing applications. In particular, we demonstrate nanomaterials coupled with ILs, as electrolytes and solvents, which offer great opportunities in electrochemical gas sensors with high sensitivity and selectivity for real-time and continuous-use gas detection in real-world harsh conditions. We discuss various methods of immobilization of ILs on transducer electrodes to prepare IL thin films for chemical analysis (gas detection) in which ILs’ unique solvation properties, varying with the nature of the constituent ions, render them ideal for selective gas detection strategies in array-based piezoelectric mass sensors. We show examples of using ILs coupled with low-cost, low-power, and miniaturized mass sensors for high temperature gas sensing applications. In addition, we illustrate an example to show that the absorption of analytes and the redox behavior of electro-active analytes in IL sensing films allow simultaneous detection of two properties of the same target analyte, i.e., sorption/partition and redox activity via electrochemical and piezoelectric mass transducers in real-time allowing one to cross-validate the measurement results, enhancing selectivity and accuracy for gas detection.