NOVEL COMPOSITE ORGANIC-INORGANIC SEMICONDUCTOR SENSORS FOR THE QUANTITATIVE DETECTION OF TARGET ORGANIC VAPORS

Composites of tin dioxide (an n-type semiconductor) and derivatives of the conducting polymer polypyrrole (a p-type semiconductor) gave reve rsible changes in electrical resistance at room temperature when expos ed to a range of organic vapours. The optimum amount of polymer giving highest sensitivity was found by experiment to be 2.5% by mass for th e polypyrrole chloride-tin dioxide composite. Composites containing 2. 5% polymer by mass, but differing in polymer derivative, were fabricat ed and exposed to low concentrations of ethanol, methanol, acetone, me thyl acetate and ethyl acetate. All were found to give significant and reversible decreases in electrical resistance. Direct comparison with sensors constructed solely of tin dioxide or polypyrrole at room temp erature showed the composites to be more sensitive. The gas sensitivit y of the composite materials depended on the type of polymer derivativ e incorporated and the dopant anion associated with the polymer. The c omposites were simple to fabricate and gave differing response profile s to a range of organic vapours.