PEDOT:PSS coated titania nanofibers for NO2 detection: Study of humidity effects

Nitrogen dioxide concentrations have been measured with a chemoresistor that change its conductance when exposed to NO2. The device uses a nanostructured inorganic scaffold (TiO2 nanofibers) to support a conductive polymer (PEDOT:PSS) used as a sensitive membrane. The electrospinning technique was adopted to deposit the scaffold, since it allows to obtaining materials with a considerable surface to volume ratio. The role of the relative humidity on the gas sensor response has been studied both in terms of relative response and rate of response variation, for RH ranging from 0% to 30%. The presence of humidity in the surrounding atmosphere changes the kinetics of absorption/desorption processes. The measurement of the response rate as a function of the concentration of NO2, for various values of relative humidity, shows a non-monotonic trend that becomes stable for humidity values larger than 17% RH. In best humidity condition the sensor response was about 1% for 250ppb of NO2.