Temperature-sensitive europium(III) probes and their use for simultaneous luminescent sensing of temperature and oxygen

Abstract

Highly photostable and strongly luminescent europium(III) beta-diketonate complexes are presented that can act as new probes for optical sensing of temperature. They can be excited with the light of a 405-nm LED and possess strong brightnesses. The decay times of the probes contained in a poly(vinyl methyl ketone) film and in poly(tert-butyl styrene) microparticles are highly temperature-dependent between 0 and 70 degrees C. The temperature-sensitive microparticles were dispersed, along with oxygen-sensitive microbeads consisting of a palladium porphyrin oxygen indicator in poly(styrene-co-acrylonitrile), in a thin layer of a hydrogel to give a dually sensing material which is excitable by a single light source. The two emissions can be separated by appropriate optical filters. The response to oxygen and temperature is described by 3D plots, and unbiased values can be obtained for temperature and oxygen, respectively, from the two luminescence signals if refined in an iteration step. The sensing scheme is intended for use in temperature-compensated sensing of oxygen, in contactless sensing of oxygen and temperature in (micro)biological and medical applications, in high-resolution oxygen profiling, and for simultaneous imaging of air pressure and temperature in wind tunnels.