Toward the OFET-Based Electronic Nose without Receptor Layers

The development of electronic nose systems is an important but rather challenging task nowadays. Organic field-effect transistors provide a powerful platform that is promising for electronic nose creation. In this work the sensory properties of a recently synthesized series of siloxane dimers of benzothieno[3,2-b][1]benzothiophene (BTBT) with different terminal alkyl groups (D2-Und-BTBT-Alkyl) as well as the possible mechanism of their sensitivity were investigated in detail. It was found that in spite of very similar chemical structure the dimers demonstrated dissimilar sensitivity and selectivity to various analytes─H2S, NH3, SO2, NO2, and several volatile organic compounds. The proposed mechanism of the patterns observed depends on both the correlations between the HOMO/LUMO energy levels of the dimer and the analyte and the dimer layer morphology/molecular packing. PCA analysis allowed us to choose the best four OFETs based on different siloxane dimers without any receptor layer for separation of the analytes and determining their concentrations on a 2D plot. These findings demonstrate that a rather small difference in the chemical structure of the organic semiconducting materials used for the OFET fabrication makes it possible to apply them as an array for the electronic nose creation.