A swelling-based chemiresistor for a biogenic odour.

Escherichia coli bacteria release 1-decanol as a byproduct of their metabolism. We demonstrate the detection of 1-decanol odour at a partial pressure in the order 100ppb by the resistance change of a swelling-based sensor, consisting of Langmuir–Schäfer deposited Au core/organic ligand shell nanoparticle films. This is an exceptionally low limit of detection for swelling-based sensors, and relies firstly, in the careful matching of the CSNPs ligands to the targeted odour, and secondly, in the very low volatility of this odour. Sensor response can be substantially increased further when films are cooled below the freezing point of 1-decanol. We observe unexpected quantitative behaviour of our sensors: response is only weakly dependent on the odour's partial pressure, and scales differently with temperature than the response of other Au-CSNP odours to more volatile odours. This may be related to their unusually strong thermal resistance drift, the difficulties in delivering very low partial pressure odour atmospheres, and the proximity to the analyte's freezing point.