A novel kind of composite material is presented that contains two indicators incorporated into a single polymer matrix, thus allowing simultaneous determination of oxygen partial pressure and temperature. The temperature‐sensitive dye (ruthenium tris‐1,10‐phenanthroline) was chosen for its highly temperature‐dependent luminescence which is the highest among the RuII polypyridyl complexes. A fluorinated palladium(II) tetraphenylporphyrin served as the oxygen probe. The indicators were incorporated into either poly(styrene‐co‐acrylonitrile) microparticles (to sense oxygen) or into poly(acrylonitrile) (for temperature sensing, since this polymer is virtually impermeable to oxygen). The luminescence of both dyes can be separated either spectrally (due to different absorption and emission spectra of the indicators) or via luminescence decay time. The material is suitable for temperature‐compensated oxygen sensing, for example, in high‐resolution oxygen profiling, and for imaging temperature in the range between 0 and 60 °C. This enables one to “see” (rather than to “feel”) temperature in this important range. Simultaneous imaging of pressure and temperature also has been achieved. It enables contactless imaging of the two parameters, for example, in wind tunnels. Due to the use of a biocompatible hydrogel matrix, the material conceivably is suited for biomedical applications.

A new family of coumarin-based pH indicators was synthesized. They are sensitive to pH in either weakly acidic or weakly basic solution. The indicators possess moderate to high brightness, excellent photostability and compatibility with light-emitting diodes. The indicators were covalently immobilized on the surface of amino-modified polymer microbeads which in turn were incorporated into a hydrogel matrix to obtain novel pH-sensitive materials. When a mixture of two different microbeads is used, the membranes are capable of optical pH sensing over a very wide range comparable to the dynamic range of the glass electrode (pH 1-11).