Mildly-Doped Polythiophene with Triflates for Molecular Recognition

TL;DR

This paper demonstrates that by changing dopants in a single conducting polymer, it can selectively detect different vapors, paving the way for integrated electronic noses based on molecular recognition.

Contribution

It introduces a method to tune a single conducting polymer's vapor sensitivity using different triflate dopants, enabling selective gas discrimination.

Findings

Poly(3-hexylthiophene) doped with triflates shows reversible, reproducible conductance changes.

A two-triflate dopant array can reliably discriminate between water, ethanol, and acetone vapors.

Charge-transfer complexes are key to chemospecific sensing in doped polymers.

Abstract

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.