Polypyrrole-based sensor for hydrazine and ammonia

An ultra-thin layer of polypyrrole can be coated on non-conducting substrates, e.g., acrylic, by dip coating into a colloidal suspension of polypyrrole. This thin coating reversibly combines with low concentrations of ammonia or hydrazine with a concomitant reversible increase in resistance; 0.1 μg cm^?3 of ammonia can readily be detected with a 1 cm² area of sensor.