Triboluminescence, Applications in Sensors

Abstract

Triboluminescence is the emission of photons caused by applying mechanical energy to a solid. Triboluminescence (TL) has very long history. At present, it is known that nearly one‐half of all inorganic compounds and between one‐quarter to one‐third of all organic compounds exhibit TL. Spectroscopic examination and characterization of the emitted light are useful for determining the excited‐state origins of TL. The best general spectroscopic characteristics that can be expected from a crystal is that the TL is similar to photoluminescence (PL) at the same temperature. TL and PL spectra are expected to be identical if the sole effect of a fracture is a population of excited electronic states. The importance of perturbations to the crystal and/or the emitting centers caused by fracture is evidenced by the differences between PL and TL spectra. For instance, some crystals show TL at room temperature but do not exhibit PL at that temperature. More commonly, a triboluminescent crystal exhibits PL, but the TL spectrum contains features that are absent from the PL spectrum. These features may be emission bands that do not occur in the PL spectrum or changes in the relative intensities of bands in the TL spectrum compared to those in the PL spectrum. A number of different mechanisms are required to account for the phenomenon of TL, although its details are still poorly understood. In this article, the mechanisms of different types of TL along with their spectroscopic experimental examples are given first. Then, experimental results on TL in inorganic crystals that contain rare‐earth ions are presented. Finally, the potential applications of TL are briefly described.