Optical Oxygen Sensors Show Reversible Cross-Talk and/or Degradation in the Presence of Nitrogen Dioxide.

A variety of luminescent dyes including the most common indicators for optical oxygen sensors were investigated in regard to their stability and photophysical properties in the presence of nitrogen dioxide. The dyes were immobilized in polystyrene and subjected to NO concentrations from 40 to 5500 ppm. The majority of dyes show fast degradation of optical properties due to the reaction with NO.

Background-Free Fluorescence-Decay-Time Sensing and Imaging of pH with Highly Photostable Diazaoxotriangulenium Dyes.

Novel fluorescent diazaoxatriangulenium (DAOTA) pH indicators for lifetime-based self-referenced pH sensing are reported. The DAOTA dyes were decorated with phenolic-receptor groups inducing fluorescence quenching via a photoinduced-electron-transfer mechanism. Electron-withdrawing chlorine substituents ensure response in the most relevant pH range (apparent p K values of ∼5 and 7.