Gas sensing properties of single conducting polymer nanowires and the effect of temperature

We measured the electronic properties and gas sensing responses of template-grown poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS)-based nanowires. The nanowires had a 'striped' structure (gold-PEDOT/PSS-gold), and were typically 8 microm long (1 microm-6 microm-1 microm for the sections, respectively) and 220 nm in diameter. Single-nanowire devices were contacted with pre-fabricated gold electrodes using dielectrophoretic assembly. A polymer conductivity of 11.5 +/- 0.7 S cm(-1) and a contact resistance of 27.6 +/- 4 kOmega were inferred from measurements on nanowires of varying length and diameter. The nanowire sensors detected a variety of odors, with rapid response and recovery (seconds). The response (DeltaR/R) varied as a power law with analyte concentration. The power law exponent was found to increase with the molecular weight of the analyte and as a function of temperature. The detection limits are set by noise intrinsic to the device and are at the ppm level even for very volatile analytes.