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A spot of color


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Diario de Navarra

José Ramón Isasi

Full Professor of Chemistry of the School of Sciences of the University of Navarra

To purpose of the Nobel Prize of Chemistry 2023

The atomic world is "strange" if we look at it from our macroscopic point of view. In the nanoworld, unusual phenomena are observed. In the microscopic world, capillary forces matter more than gravitational forces. Tiny beings and microorganisms live in their world, which is somewhat different from ours, in that sense. Another example: an infinitesimal particle of a pure material melts at a considerably lower temperature than a solid of larger dimensions, because a large part of its atoms are at the edge, and are easier to tear off. For something of tiny size, there will always be a lot of surface area for little volume. (Small) size matters (a lot). However, these are examples that can be explained by classical physics.

Every year, in my first course class of Chemistry General, I show my students the double slit experiment: electrons are not simple particles, since they produce interferences. This is impossible for a material corpuscle. However, electrons can also behave like waves. This is a "non-classical" effect, inexplicable outside quantum theory. Thus, a "quantum dot" is a nanoparticle, of imperceptible dimensions, whose color depends on its size. As has happened on other occasions, this curious property had already been predicted by theorists before technology and scientific ingenuity had been able to manufacture these particles at will. Well, not exactly. The Chemistry is not only science and technology born in the Modern Age; before that, from Prehistory and up to the Age average, it was art: metals, ceramics and ... glass. The master glassmakers of antiquity knew well how to get all the colors of the rainbow, adding for example different metallic salts. And why, sometimes, with an identical composition, a glass ended up with a different color than another? Not very logical, is it? Unless the size of those particles added to the glass does matter. The way they were ground and mixed or the temperature during the production process. This influenced.

How beautiful, isn't it? Colored glasses. With identical composition Chemistry, but different nano-sizes in their coloring additives. And what is this for? It could be useless and fascinating at the same time. Alfred Nobel left his bequest to reward the architects of a better world. Just by unraveling this beauty, Ekimov and Brus would already deserve the Nobel Prize, but the fact is that, in addition, behind a fundamental research there is always someone who finds a use for it. For better or worse, I might add. Once Bawendi managed to prepare these "quantum dots" with excellent quality in the 1990s, applications began to flood in: QLED monitors and televisions or mapping of biological tissues, for example. And whatever remains to be developed in the fields of electronics, clean energy and encrypted communications.