Biopolymer based ionogels as active layers in low-cost gas sensors for electronic noses

Electronic noses are formed by an array of gas sensors connected to a pattern recognition computational system and have been applied in a wide range of fields. In this work we describe chemiresistive gas sensors produced by the deposition of ionogels onto metallic interdigitated electrodes. Three ionogels were formed by a single ionic liquid, EMIMDCA, and three different biopolymers (gelatine, agar and sodium alginate). As a proof of concept, this nose was tested with five organic volatile compounds (methanol, ethanol, acetone, ethyl acetate and hexane) having different polarities and different room temperature vapour pressures. Principal components analysis (PCA) was used for dimensionality reduction and to represent the separation of these solvents. Applying five different machine learning classification algorithms and two cross-validation methods (leave-one-out and K-fold), the accuracy of the e-nose was evaluated in discriminating the solvents studied. Hit rates of at least 96% were obtained.