Gas sensors

Abstract

A gas sensor for use in monitoring gases such as H 2 S, NO 2 or SO 2 comprises a film or layer of non-protonated polyaniline as the gas sensing material.

1 . A gas sensor comprising a film or layer of non-protonated polyaniline as the gas sensing material.  
     
     
         2 . A gas sensor as claimed in  claim 1 , in which the non-protonated polyaniline is in the base emeraldine form having the formula:  
       
         
           
           
               
               
           
         
       
     
     
         3 . A gas sensor as claimed in  claim 1 , in which the non-protonated polyaniline is in the base leuco-emeraldine form having the formula:  
       
         
           
           
               
               
           
         
       
     
     
         4 . A gas sensor as claimed in any of the preceding claims, in which the film or layer of non-protonated organic material is deposited on a substrate which supports spaced electrodes, with the film or layer bridging the spaced electrodes.  
     
     
         5 . A method of making non-protonated polyaniline comprises treating protonated polyaniline with an alkaline solution to de-protonate the material.  
     
     
         6 . A method of sensing a gas, comprising contacting a film or layer of non-protonated polyaniline forming the gas sensing material with the gas, determining the conductivity of the film or layer so contacted, and using the determined conductivity as a measure of the concentration of the gas contacting the film or layer.  
     
     
         7 . A method for the preparation of a gas sensor substantially as hereinbefore described with reference to the Examples.