REDUCED DICYANOVINYL DYES - A CHROMOPHORE TO BE USED FOR OPTICAL SENSING IN THE RED AND NEAR-INFRARED SPECTRAL RANGE

Reduced dicyanovinyl dyes, a new type of pH-sensitive chromophores wit h absorption bands reaching into the near-infrared (near-IR) spectral range, are presented, Side-chain residues with different properties we re attached to the chromophore backbone to influence the pK(a) values of the indicator dyes. The resulting dyes were suitable to be incorpor ated into lipophilic optical sensing bulk membranes (optodes) made fro m plasticized poly(vinylchloride), The characteristics of the indicato rs were studied in pH-sensitive membranes. Full signal reversibility f or protonation and deprotonation and high chromophore stability were o bserved. As an example of application for ion-sensing, a calcium-selec tive optode is demonstrated. The dynamic measuring range for calcium w as 10(-6)-10(-1) M in aqueous solutions, buffered at pH 2.7. The respo nse behavior, short-time reproducibility, and stability of the optodes are discussed.