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 complexation or protonation/deprotonation, the dyes presented here perform reversible chemical reactions with the analyte, resulting in changes in absorbance or fluorescence. Specifically, azo and stilbene dyes which exhibit a reactive 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 ligand molecule are termed 'chromo-' or 'fluororeactands'. They are embedded in various polymer materials and have been characterised for the optical sensing of aliphatic amines, alcohols and humidity. Furthermore, methacrylate derivatives of the dyes have been tested. They were prepared to link the dyes covalently to the polymer matrix. The optical and physical properties of the dye methacrylates make them promising candidates not only for optical sensing but also for applications in molecularly imprinted polymers and non-linear optics.