Structure-property relationships in NOx sensor materials composed of arrays of vanadium oxide nanoclusters

The mixed-valent vanadium oxide based three-dimensional framework structure species [Cd-3(H2O)(1-2)(V16V2O36)-V-IV-O-V(OH)(6) (AO(4))]center dot 24H(2)O, (A = V,S) (Cd3(VO)(o)) represents a rare example of an interesting sensor material which exhibits NOx {NO + NO2} semiconducting gas sensor properties under ambient conditions. The electrical resistance of the sensor material Cd3(VO())o decreases in air. Combined characterization studies revealed that the building block, {V18O42(AO(4))} cluster, of 3-D framework undergoes oxidation and remains intact for at least 2 months. The decrease in resistance is attributable to the reactivity of molecular oxygen towards vanadium which results in an increase in the oxidation state as well as the coordination number of vanadium center and decrease in band gap of Cd-3(VO)(o). Based on these results we propose that the changes in semiconducting properties of Cd-3(VO) o under ambient conditions are due to the greater overlap between the O 2p and V 3d orbitals occurring during the oxidation. (C) 2017 Elsevier Masson SAS. All rights reserved.