The multimodal detection as a tool for molecular material-based gas sensing

The adsorption of a target gas on a material induces a change in several physical characteristics, such as the dielectric constant, the work function or the conductivity. The use of different transducers sensitive to the variation of these parameters appears to be a relevant methodology worthy of investigation. In the field of sensors, molecular materials present interesting and potentially valuable features as sensing elements for real gas sensor applications. In this article, we review the different types of conductimetric transducers and also show how a molecular material-based microwave transducer can be used for gas sensing. Among conductimetric transducers, resistors have been historically the most commonly exploited way for the detection and quantification of gas pollutants. Herein, we focus on new transducers, either based on the well-known OFETs, or on transducers combining two molecular materials, namely the p-n junctions and the brand new molecular semiconductor-doped insulator (MSDI) heterojunctions. The sensitivity of the devices is demonstrated through the detection of ammonia and ozone in the range of ppm and ppb, respectively.