Luminescent Lanthanides

Lanthanide Luminescence for Dummies

When lanthanide ions are incorporated into certain materials, such as glasses, crystals and powders, these materials may become luminescent, which means that they emit light after having been stimulated ("excited") to do so. This excitation may for example be achieved by passing an electrical current through the material (electroluminescence) or by having it absorb light (photoluminescence). Note that in the case of photoluminescence, light is first absorbed by the material, and subsequently emitted. Usually the absorbed and the emitted light have different colours.

The electrical current or the absorbed light puts the lanthanide ions in an "excited state". As the ions relax to their fundamental state (the "ground state"), they emit light. This way of producing light is very different from what happens inside incandescent light bulbs. There, an electrical current heats a metallic wire to such high temparatures that it starts glowing. A lot of energy that is used by incandescent lamps is not turned into light but into heat: you have probably noticed that these lamps become quite hot! Luminescent materials can be much more efficient for turning energy into light. The light that they generate is sometimes referred to as "cold light".

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