  Organic semiconductors have enough molecular versatility to feature
chemo-specific electrical sensitivity to large families of chemical
substituents via different intermolecular bonding modes. This study
demonstrates that one single conducting polymer can be tuned to either
discriminate water-, ethanol- or acetone-vapors, on demand, by changing the
nature of its dopant. Seven triflate salts differ from mild to strong p-dopant
on poly(3hexylthiophene) sensing micro-arrays. Each material shows a pattern of
conductance modulation for the polymer which is reversible, reproducible, and
distinctive of other gas exposures. Based on principal component analysis, an
array doped with only two different triflates can be trained to reliably
discriminate gases, which re-motivates using conducting polymers as a class of
materials for integrated electronic noses. More importantly, this method points
out the existence of tripartite donor-acceptor charge-transfer complexes
responsible for chemospecific molecular sensing. By showing that molecular
acceptors can have duality to p-dope semiconductors and to coordinate donor
gases, such behavior can be used to understand the role of frontier orbital
overlapping in organic semiconductors, the formation of charge-transfer
complexes via Lewis acid-base adducts in molecular semiconductors.
