Optical thin ®lm polymeric sensors for the determination of aqueous chloride, bromide and iodide ions at high pH, based on the quenching of ̄uorescence of two acridinium dyes

Two halide sensitive acridinium ̄uorophores have been synthesised and immobilised in a hydrophilic copolymer. Thin ®lms of the copolymers swell in aqueous media allowing dye ̄uorescence to be dynamically quenched by the di€usion of halide ions. The new sensor ®lms have been characterised in terms of their sensitivity and selectivity towards halide and are compared to ®lms containing both bound and unbound Rhodamine B. The sensor ®lms are reversibly capable of determining halide ions at mildly alkaline pH with typical 90% response times of 1±2 min. The sensor ®lms are cheap to produce, can readily be coated on disposable glass microscope slides or on the tip of a ®bre optic bundle and have a shelf life in excess of 2 years. # 2000 Published by Elsevier Science Ltd. All rights reserved.