Dual lifetime referenced trace ammonia sensors

Dual lifetime referencing is applied to trace ammonia sensors. Two schemes are presented to achieve luminescence lifetime based measurements in the frequency domain: the first is based on a resonance energy transfer (RET) system with eosin ethylester as indicator applying a coumarin derivative as donor. The second consists of a resonance energy transfer cascade with a coumarin derivative, sulforhodamine B and the absorption dye bromophenol blue as ammonia-sensitive dye. The large Stokes shift due to the energy transfer and the resulting spectral properties of the sensing layers enable dual lifetime referencing using an Ir(III)-coumarin complex for both ammonia detection systems. The sensing systems are applicable for the monitoring of ammonia in the range of either 1–5000 μg/l or 50–50,000 μg/l, respectively.