Synthesis and characterization of fluorophore-absorber pairs for sensing of ammonia based on fluorescence

A new and simple preparation procedure for fluorophore absorber pairs which enable optical sensing of ammonia is reported. In ion pairs formed between organoruthenium complexes (fluorophore) and triphenylmethane dyes (absorber), a deprotonation of the absorber leads to an absorbance band which overlaps the emission of the fluorophore whereby both the fluorescence intensity and the fluorescence lifetime of the fluorophore 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 fluorophore-absorber pair and coated with a PTFE layer allow a continuous assay of dissolved ammonia in the range of 0.01 to 25 mg l−1. 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 l−1.