Russian chemists have made a breakthrough in controlling the luminescence of rare earth metals. Researchers from the HSE University and the Topchiev Institute of Petrochemical Synthesis of the Russian Academy of Sciences have developed a method that allows changing the color and brightness of the luminescence of these elements by selecting a special chemical environment.
Rare earth elements, such as lanthanum, cerium, and terbium, are widely used in microelectronics, LEDs, and luminescent materials (neon signs, LED lamps, and screens of modern gadgets). Their main feature is the ability to emit light of a strictly defined color. Now, scientists have learned to change these properties by creating new compounds with specified characteristics.
Chemists have created a series of compounds from cerium to terbium, which made it possible to identify general patterns in the change of properties. Particularly impressive results were shown by cerium ionomers — instead of the usual ultraviolet glow, it was possible to obtain yellow radiation.
Previously, a change in the color of luminescence had already been observed, but it was not understood how it works. Now, with the participation of our physicist colleagues, we have managed to understand the mechanism of this effect.
The secret of the new method lies in the use of special organic ligand molecules. They create a specific electrostatic field around the ion, which changes the energy of electronic orbitals and allows controlling the luminescence spectrum.
Usually, a ligand molecule absorbs ultraviolet light, transitions to an excited state, and transfers this energy to a metal atom. But in new compounds, the process went differently: energy was transferred not directly to 4f-electrons, but through an intermediate 5d-state.
The discovery has great practical significance. The new approach will allow more efficient design of materials with specified properties for creating modern light sources, displays, and lasers. This is especially important for the development of domestic electronics and optical industry.
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