Chapter 2 Gas Sensing Ionic Liquids on Quartz Crystal Microbalance

Recent advances in “designer solvents” have facilitated the development of ultrasensi‐ tive gas sensing ionic liquids (SILs) based on quartz crystal microbalance (QCM) that can real‐time detect and discriminate volatile molecules. The amalgamation of tailored‐made SILs and label‐free QCM resulted in a new class of qualitative and semi‐quantitative gas sensing device, which represents a model system of electronic nose. Because a myriad of human‐made or naturally occurring volatile organic compounds (VOCs) are of great interest in many areas, several functional SILs have been designed to detect gaseous alde‐ hyde, ketone, amine and azide molecules chemoselectively in our laboratory. The versa‐ tility of this platform lies in the selective capture of volatile compounds by thin‐coated reactive SILs on QCM at room temperature. Notably, the detection limit of the proto‐ type system can be as low as single‐digit parts‐per‐billion. This chapter briefly introduces some conventional gas sensing approaches and collates recent research results in the inte‐ gration of SILs and QCM and finally gives an account of the state‐of‐the‐art gas sensing technology.