A Langasite Crystal Microbalance Coated with Graphene OxidePlatinum Nanocomposite as a Volatile Organic Compound Sensor: Detection and Discrimination Characteristics We propose a novel langasite crystal microbalance (LCM) sensor with a graphenebased sensing medium to detect and discriminate volatile organic compounds (VOCs) at room temperature. A thin film of graphene oxide embedded with Pt nanostructures (GOPt nanocomposite) was deposited on the electrode surface of the LCM, a thicknessshear acoustic wave resonator. Ethyl acetate, acetic acid, and ethanol were chosen as typical VOCs for this study. Sensitivity and selectivity of coated LCM were investigated for different concentrations of the VOCs by analysing the resonant properties of the sensor. When exposed to VOCs, a negative shift in series resonance frequency was observed due to the mass loading of VOC molecules. Simultaneously, changes in equivalent resistance and parallel resonance frequency of the sensor were also observed due to the interaction of VOCs with charge carriers on the GOPt nanocomposite film surface. This dual measurement of both series and parallel resonance frequencies allowed for detection and discrimination of VOCs. Moreover, the high thermal stability of langasite makes the proposed sensor suitable even for harsh environmental conditions.

Quartz Crystal Microbalance Based Sensor Arrays for Detection and Discrimination of VOCs Using Phosphonium Ionic Liquid Composites Herein, we examine two sensing schemes for detection and discrimination of chlorinated volatile organic compounds (VOCs). In this work, phosphonium ionic liquids (ILs) were synthesized and vapor sensing properties examined and compared to phosphonium ILpolymer composites. Pure IL sensors were used to develop a QCMbased multisensory array (MSA), while ILpolymer composites were used to develop an MSA and virtual sensor arrays (VSAs). It was found that by employing the composite MSA, five chlorinated VOCs were accurately discriminated at 95.56%, which was an increase in accuracy as compared to pure ILs MSA (84.45%). Data acquired with two out of three VSAs allowed discrimination of chlorinated VOCs with 100% accuracy. These studies have provided greater insight into the benefits of incorporating polymers in coating materials for enhanced discrimination accuracies of QCMbased sensor arrays. To the best of our knowledge, this is the first report of a QCMbased VSA for discrimination of closely related chlorinated VOCs.