Synthesis and characterization of ¯uorophore-absorber pairs for sensing of ammonia based on ¯uorescence

A new and simple preparation procedure for ¯uorophore absorber pairs which enable optical sensing of ammonia is reported. In ion pairs formed between organoruthenium complexes (¯uorophore) and triphenylmethane dyes (absorber), a deprotonation of the absorber leads to an absorbance band which overlaps the emission of the ¯uorophore whereby both the ¯uorescence intensity and the ¯uorescence lifetime of the ¯uorophore are altered. Dissolving these ion pairs in polymer materials such as poly (vinyl chloride) or porous glass obtained by the sol±gel process results in membranes which respond to ammonia. Plasticized PVC membranes containing the ¯uorophore-absorber pair and coated with a PTFE layer allow a continuous assay of dissolved ammonia in the range of 0.01 to 25 mg lÿ1. Membranes composed of the ion pair dissolved in a sol±gel-based glass and coated with PTFE respond to ammonia with a similar sensitive range and a limit of detection of 0.01 mg lÿ1.