Ionic liquids tailored for reaction-based gas sensing on quartz crystal microbalance

Gas sensing technologies are of importance for a variety of industrial, environmental, medical, and even military applications. Many gases, such as man-made or naturally occurring volatile organic compounds (VOCs), can adversely affect human health or cause harm to the environment. Recent advances in “designer solvents” and sensor technologies have facilitated the development of ultrasensitive gas sensing ionic liquids (SILs) based on quartz crystal microbalance (QCM) that can real-time detect and discriminate VOCs. Based on specific chemical reactions at room temperature, thin-coated functionalized ionic liquids on quartz chips are able to capture VOCs chemoselectively with a single-digit parts-per-billion detection limit. The amalgamation of tailor-made functional SILs and QCM results in a new class of qualitative and semiquantitative gas sensing device, which represents a prototype of electronic nose. This review vignettes some conventional gas sensing approaches and collates latest research results in the exploration of SIL-on-QCM chips and gives an account of the state-of-the-art gas sensing technology.