Thermally populated "bright" states for wide-range and high temperature sensing in air.

A series of air-stable triarylphosphine oxide-based thermosensitive ratiometric sensors based on local excited (LE) and charge transfer (CT) emissions have been designed and synthesized. The fluorescence intensity of tri(pyren-1-yl)phosphine oxide exhibits a prominent temperature-dependent feature over a wide temperature range due to thermally populated emissive LE states. The wide ratiometric temperature sensing range and high stability/reversibility in an ambient atmosphere indicate their great potentials in facile and practical applications.