Reversible chemical reactions as the basis for optical sensors used to detect amines, alcohols and humidity

A new class of indicator dyes for use in analytical chemistry is presented. In contrast to most existing indicator dyes, which change colour upon comp lexation or protonation/deprotonation, the dyes presented here perform reve rsible chemical reactions with the analyte, resulting in changes in absorba nce or fluorescence. Specifically, azo and stilbene dyes which exhibit a re active trifluoroacetyl group, reversibly interact with alcohols, amines or water to give the respective diol, hemiaminal, hemiacetal or zwitterion. Indicator dyes that combine the properties of a chemical reagent and a liga nd molecule are termed 'chromo-' or 'fluororeactands'. They are embedded in various polymer materials and have been characterised for the optical sens ing of aliphatic amines, alcohols and humidity. Furthermore, methacrylate d erivatives of the dyes have been tested. They were prepared to link the dye s covalently to the polymer matrix. The optical and physical properties of the dye methacrylates make them promising candidates not only for optical s ensing but also for applications in molecularly imprinted polymers and non- linear optics.