Development of microwave gas sensors

Microwave gas sensing with a microstrip interDigital capacitor: Detection of NH3 with TiO2 nanoparticles

“…Ammonia exposures were maintained for 1 minute, and followed by 4 minutes of pure argon exposures, as depicted in In our previous work, the response signals were the real and imaginary parts of the reflection coefficient (S11) [4][5][6][7]. In this paper, we extend our analysis to the transmission coefficient (S21).…”

“…4 [6]. The gas flow enters the measuring cell by one side, and leaves by the other side to an extractor hood.…”

“…In our previous works we presented promising results in the detection of ethanol [5], ammonia [6] and toluene [7], on the basis of a microwave antenna adapted to reflection measurements. Various sensitive materials have been used, including metal oxide such as SnO2 and TiO2, dealuminated faujasite DAY zeolite, or organic materials such as cobalt phtalocyanine CoPc.…”

VOCs Detection by Microwave Transduction Using Zeolites as Sensitive Material

“…The response of the microwave sensor leads to the obtention of a reflection coefficient at each frequency. This one is a complex number representing the ratio between the incident electromagnetic wave at the input of the circuit and the reflected wave [1,6].…”

“…Most of the commercialized gas sensors are based on a conductimetric transduction using non-stoichiometric metal oxides as sensitive materials [1]. They are mainly sensitive to redox active species that can accept or give electrons, which induce a variation of the density of charge carriers [2].…”