CONDUCTIVITY OF POLYSTYRENE FILM UPON EXPOSURE TO NITROGEN-DIOXIDE - A NOVEL NO2 SENSOR

A novel NO2 sensing device has been developed based on a reversible change in d.c. conductivity in an otherwise insulating film of polystyrene upon exposure to NO2 gas. The device consists of a polystyrene film-coated interdigitated electrode, for which several orders of magnitude increase in conductivity occurs when an NO2/N2 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 N2O4, the form of NO2 within the film, to NO+NO3-, with the appropriate anodic and cathodic electrochemistry; it is therefore extremely selective for NO2.