Molecular recognition of SWCNTs/polythiophene chemiresistor toward xylene isomers. (a) Chemical structures of xylene isomers, poly(3-hexylthiophene) (P3HT), and synthesis scheme of p-tert-butylcalix[4]arene-substituted polythiophene (P1). Conductance change of the chemiresistor of (b) SWCNTs and P1 and (c) SWCNT and P3HT to p-xylene, o-xylene, and m-xylene at 400 ppm. Reproduced with permission from Ref. 97. Copyright 2008, Wiley-VCH Verlag GmbH & Co.