Glow-in-the-dark traffic markings: feasible or not feasible?

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A review of mechanoluminescence in inorganic solids : compounds, mechanisms, models and applications

Mechanoluminescence (ML) is the non-thermal emission of light as a response to mechanical stimuli on a solid material. While this phenomenon has been observed for a long time when breaking certain materials, it is now being extensively explored, especially since the discovery of non-destructive ML upon elastic deformation. A great number of materials have already been identified as mechanoluminescent, but novel ones with colour tunability and improved sensitivity are still urgently needed. The physical origin of the phenomenon, which mainly involves the release of trapped carriers at defects with the help of stress, still remains unclear. This in turn hinders a deeper research, either theoretically or application oriented. In this review paper, we have tabulated the known ML compounds according to their structure prototypes based on the connectivity of anion polyhedra, highlighting structural features, such as framework distortion, layered structure, elastic anisotropy and microstructures, which are very relevant to the ML process. We then review the various proposed mechanisms and corresponding mathematical models. We comment on their contribution to a clearer understanding of the ML phenomenon and on the derived guidelines for improving properties of ML phosphors. Proven and potential applications of ML in various fields, such as stress field sensing, light sources, and sensing electric (magnetic) fields, are summarized. Finally, we point out the challenges and future directions in this active and emerging field of luminescence research

Designing phosphors for brighter LEDs

Light-emitting diodes or LEDs are increasing their share as components in lighting and display markets on a daily basis. In this article, an overview is given of the scientific research that is still going on to improve the quality of the end products and to lower the price as much as possible. It is dwelled upon how white LEDs are constructed from a semiconductor diode and one or multiple photoluminescent materials or phosphors. Different applications require different specifications for white LEDs, implying the need for a dedicated design strategy of the optical materials forming the key components of a white LED