Conductivity of polystyrene film upon exposure to nitrogen dioxide: a novel NO 2 sensor

Abstract

A novel NO 2 sensing device has been developed based on a reversible change in d.c. conductivity in an otherwise insulating film of polystyrene upon exposure to NO 2 gas. The device consists of a polystyrene film-coated interdigitated electrode, for which several orders of magnitude increase in conductivity occurs when an NO 2/N 2 mixture, 1:10 v/v, comes into contact with the film. This rapid (2 min) change in conductivity is reversible and is not associated with any irreversible decomposition of the film. The conductivity of the film is believed to be due to the self-ionization of N 2O 4, the form of NO 2 within the film, to NO +NO 3 −, with the appropriate anodic and cathodic electrochemistry; it is therefore extremely selective for NO 2.