Characterization of the Sensor Response of Gold Nanoparticle Chemiresistors

The response time of chemiresistors consisting of gold nanoparticles coated with self-assembled monolayers (SAM) of 1-hexanethiol, exposed to different hydrocarbons dissolved in water, is investigated with respect to the analyte SAM/water partition coefficient, the analyte-water How velocity, and the nano particle film thickness. We show experimentally that the response time is proportional to the analyte SAM/water partition coefficient and that for sufficiently large velocities the response time becomes flow velocity independent. The dependence of the response time on film thickness is found to be different in the two different flow velocity regimes examined. We outline in detail a theoretical model that explains our experimental data.