Lanthanide Luminescence: From a Mystery to Rationalization, Understanding, and Applications

What is it about?

Lanthanide luminescence is at the heart of applications as diverse as lighting, telecommunications, lasers, security marking, barcoding, luminescent molecular thermometers, immunoassays, or optical medical imaging. The subject is fascinating and has always accompanied the development of lanthanide science and technology, from the early discovery of the 4f elements to present high-technology applications. The large added value of luminescent phosphors, probes, and materials explains the enthusiasm research groups are coming up with in looking for new and better systems, in addition to simple fascination for light emission.The chapter highlights the various facets of lanthanide light emission, with special emphasis on historical developments, understanding the underlying mechanisms, and presentation of leading applications. The 4fn and 4fn - 15d electronic configurations of lanthanide ions generate numerous electronic levels and most of the transitions are forbidden by Laporte's rule, therefore very faint. Systematic experimental work had therefore to be substantiated by theoretical concepts, leading to the elaboration of energy diagrams and to modeling of the energy migration mechanisms during sensitization of lanthanide luminescence.The major applications mentioned above are still vivid today, in parallel to more futuristic ones such as photocatalysts, solar energy conversion, optical cooling, and quantum information processing eventually leading to optical computers. All these fields trigger materials developments (particularly at the nanoscale) and development of new theoretical concepts.

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