A novel concept for humidity compensated sub-ppm ammonia detection

We report on the principle of a discriminative sensor for the detection of ammonia gas at varying levels of humidity. This is achieved by using two differently conducting formulations of poly(styrene sulfonate) doped poly(3,4-ethylenedioxythiophene) (PEDOT/PSS) in two sensor elements. Humidity and ammonia concentration can be separated because the sensor elements show opposite response to the two stimuli: contact to ammonia leads to an increase in the electrical resistivity of both formulations, while a change in the surrounding humidity level decreases the resistivity of one of the PEDOT/PSS types, while it increases that of the other. Moreover, it is shown that with the hereby presented discriminative sensor concept ammonia concentrations in the sub-ppm regime can be detected.