Chemical Sensing Using Indicator Dyes

T h i s chapter describes the des ign, f a b r i c a t i o n , a n d propert ies of mater ia ls that respond to the presence of a chemical species by a change i n their opt ical properties. Ideally, such effects are reversible. They may be detected by conventional methods of absorpt ion, reflection, or luminescence spectrometry, a n d appl ied i n various formats such as test strips and disposable tests, but preferably by m a k i n g use of optical waveguides i n c l u d i n g optical fibers, integrated optics, capi l lary type devices, and the l ike . Specifically, we describe the design and use of appropriate indicator dyes, polymers , and addit ives, w i t h a part icular focus on materials for sensing p H , oxygen, carbon dioxide, a m m o n i a , and certain ions. These materials (or their solutions i n an appropriate solvent) may be deposited on various supports i n c l u d i n g simple plastic strips (e.g.. by spin-coat ing) , on fibers (e.g., by dip coating), inside porous materials (e.g., by soaking) , on integrated waveguides or walls of disposable cuvettes (e.g., by spreading the solutions as th in films), inside capil laries (e.g., by passing the solution through the capi l lary) , on the bottom of microtitre plates, or inside disposable vials.