Fluorescent aluminum compound with 70% quantum efficiency

With the participation of the ACP principal scientists Stefanie Gräfe, Maria Wächtler, Benjamin Dietzek and Christian Eggeling, chemists of the University of Jena have set a new record: they have discovered a fluorescent aluminum compound that exhibits the highest quantum efficiency yet known. The compound emits a light particle for nearly every light particle that radiates onto it. The discovery could prove beneficial to applications like LED technology.

Luck-based science

„This discovery was serendipity, through-and-through: pure chance”, explains Robert Kretschmer, Junior Professor of inorganic catalytic chemistry at the Friedrich Schiller University Jena. “We actually wanted to perform catalysis with the substance, but my team noticed quickly that the substance is strongly fluorescent. We followed up on these observations and verified this unique property.”

Fluorescence is a process in which a substance emits light if other light shines onto it. This phenomenon is exploited, for example, in fluorescent bulbs. The white coating of the bulb comes into contact with invisible UV radiation that causes the coating to emit light. The light emitted from light-emitting diodes (LEDs) is also caused by fluorescence. As in all other cases whenever energy is transferred, some light energy is lost in the process of fluorescence.

“The previous record for aluminum compounds is about 70 percent”, said Kretschmer. “This quantum efficiency means that, for every ten light particles irradiating the substance, seven new light particles are emitted. In the case of our compound, almost every light particle is transformed into a new one.”

Cheap aluminum starts the chemical process

A further benefit of the likely record-setting compound is its use of aluminum, a relatively cheap raw material. “Two aluminum ions are bound in an organic molecule, a so-called ligand, in our substance”, explains Kretschmer further. “The production is very simple and can be performed in large quantities, that is in units of grams, in the laboratory. We could also weave the substance into a fabric that still fluoresces with a respectable 90 percent quantum efficiency.”

Next, Kretschmer and his team want to investigate the molecule more thoroughly and better understand the record-breaking fluorescence. “We will replace the aluminum ions with other metals and also modify the organic ligand.” A further goal is also to make the molecule more stable. The molecule cannot presently be used in water, for example, which is important for biological applications. “We already have some ideas about how this can be achieved."