NO2 optical sensing in ZnO nanostructures

The optical response at room temperature of ZnO nanostructures, grown by controlled vapour phase deposition, to low concentrations of NO₂ gas mixed in dry-air has been investigated. In particular the quenching in the emission signal, due to the interactions between oxidizing gas molecules and sample surface, has been monitored in excitonic and defect band, as a function of NO₂ gas concentration. The dynamic responses and the resulting calibration curves, obtained for each emission band, have been compared. Furthermore responses of nanorods with different size and nanostructures with different exotic shape have been discussed in order to clarify the role of the morphology and/or dimensions and structural quality. In particular we have correlated the growth conditions and the resulting structural and optical properties of the samples, highlighting their role in the optical sensing response.