Fibre optic ammonia sensing employing novel near infrared dyes

Two dye materials that display near infrared absorption bands have been synthesised and applied successfully to the optical sensing of ammonia vapour. Methyl- and ethyl-derivatives of a 5-(4'-dialkylaminophenylimino)quinolin-8-one copper(II)perchlorate complex were immobilised in a thin-film PVC matrix coated on a 600 mu m optical fibre. Evanescent wave absorption was used to interrogate the dye under exposure to 10-100 ppm ammonia in nitrogen carrier gas. The immobilised dyes were found to show large absorption bands at 740 and 770 nm for the methylated and ethylated forms, respectively. The peak maxima were monitored in real-time using a CCD array microspectrometer. The response and recovery times were found to be in the order of seconds and the reversibility excellent. (C) 1998 Elsevier Science S.A. All rights reserved.