Effect of film thickness and different electrode geometries on the performance of chemical sensors made of nanostructured conducting polymer films

In this contribution, the effect of film thickness and different microelectrode geometries on the performance of chemical sensors made of nanostructured films of conducting polymer poly(o-ethoxyaniline) (POEA) and sulfonated polystyrene (PSS) is investigated. Both parameters present significant influence on the sensors response. Depending upon the concentration of NaCl solutions, thicker films exhibit higher sensitivity to NaCl in comparison to thinner films according to impedance spectroscopy studies. The larger surface roughness of thicker films seems to be the main reason for such a behavior. Meanwhile, as the area of the gold electrodes is increased more sensitive sensors are obtained. At two different frequencies, namely 100 Hz and 1 kHz, the response of the sensors are found to be linear or exponentially dependent on the NaCl concentration. Furthermore, the sensors response is reproducible and NaCl can be detected at concentrations as low as 10 μM. The potential use of such sensors in an electronic tongue system is discussed.