The features of thin film and ceramic sensors at the detection of CO and NO2

Photoreduction of Mesoporous In2O3: Mechanistic Model and Utility in Gas Sensing

“…However, the above-mentioned partial irreversibility of this effect (i.e., a non-vanishing photoconductivity, which is observed only in the absence of oxygen in the surrounding atmosphere) can only be explained by photoreduction. In the case of In 2 O 3 , oxygen surface groups are not observed [7] and therefore the desorption mechanism (2) is assumed to be a negligible effect. Re-oxidation is suppressed under a pure nitrogen atmosphere, as opposed to synthetic air.…”

“…The gas-sensing properties of In 2 O 3 cannot be explained in a straightforward way by using standard models such as ionosorption mechanisms; [3] some studies rather propose that the strong change in electronic conduction upon interaction with oxidizing gases may be related to a redox-type activity of In 2 O 3 . [7] A photoreduction effect is often explained by the generation of electron-hole pairs due to photoexcitation; [8] this explanation does not describe excitation by sub-bandgap light of In 2 O 3 . Structural and morphological properties of sensing materials at the nanometer length scale often have a strong impact on the utility of a sensor device.…”

Experimental and theoretical studies of indium oxide gas sensors fabricated by spray pyrolysis

“…The sensing mechanism of In 2 O 3 is attributed mainly to oxidation/reduction (redox) mechanism [22][23][24]. This postulation is based on the assumption that chemisorbed oxygen species do not exist at the surface of In 2 O 3 because of its transformation into lattice atomic oxygen immediately after adsorption.…”

Kinetics of indium oxide-based thin film gas sensor response: The role of “redox” and adsorption/desorption processes in gas sensing effects

“…Moreover, if during O3 detection only oxygen and water participate in those reactions; during CO and H2 detection besides oxygen and water we have additional participants in the face of those gases. For explanation of observed effects it has been proposed [23,[28][29][30][31] that the In 2 O 3 response to reducing gases at T oper N 300°C runs through a "redox" (reduction/reoxidation) mechanism and response to oxidizing gases at T oper b 300°C through an adsorption/desorption mechanism. In the adsorption/desorption mechanism of gas detection, one must take into account the processes such as adsorption/desorption of O 3 , O 2 , H 2 O and the detected gases; the dissociation of adsorbed molecules; surface oxygen diffusion; surface reaction between detected gas and adsorbed species; and the desorption of the products of surface reactions.…”