where the estimated parameters are summarized in Table . As the SnSe2 sample might contain a minor secondary phase, its result was not considered. The values found for 𝐿𝐷𝐿 are below those reported in recent studies, and also far below the level which is considered harmful to human health . The reactivity derived from both chalcogenide elements, as well as the exposure of surface defective edges by exfoliation are considered factors that can influence the sensitivity of NO2 sensor devices. Such characteristics can be understood through adsorption phenomena. In general, it is assumed that molecular oxygen (O2) is adsorbed on the surface of the n-type semiconductors, trapping electrons according to the reaction (I) :