Laboratory flasks are used for rationalization through the announcement of the winners of the 2023 Nobel Prize in chemistry at Royal Swedish Academy of Sciences in Stockholm on October 4, 2023.
| Photo Credit: AFP
The story to date: Alexei I. Ekimov, Louis E. Brus, and Moungi G. Bawendi have been awarded the 2023 Nobel Prize for chemistry “for the discovery and synthesis of quantum dots”.
What is a quantum dot?
A quantum dot is a extremely small meeting of atoms (just some thousand) round a number of nanometres broad. The ‘quantum’ in its identify comes from the truth that the electrons in these atoms have little or no area to maneuver round, so the crystal as a complete shows the quirky results of quantum mechanics — results that in any other case can be exhausting to ‘see’ with out extra refined devices. Quantum dots have additionally been known as ‘artificial atoms’ as a result of the dot as a complete behaves like an atom in some circumstances.
Why are they of curiosity?
There are two broad varieties of supplies: atomic and bulk. Atomic of course refers to particular person atoms and their particular properties. Bulk refers to massive assemblies of atoms and molecules. Quantum dots lie someplace in between and behave in ways in which neither atoms nor bulk supplies do. One specific behaviour distinguishes them: the properties of a quantum dot change primarily based on how massive it’s. Just by tweaking its dimension, scientists can change, say, the quantum dot’s melting level or how readily it participates in a chemical response.
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When gentle is shined on a quantum dot, it absorbs after which re-emits it at a unique frequency. Smaller dots emit bluer gentle and bigger dots, redder gentle. This occurs as a result of gentle shone on the dot energises some electrons to leap from one power stage to the next one, earlier than leaping again down and releasing the power at a unique frequency. So, quantum dots will be simply tailored for a spread of purposes together with surgical oncology, superior electronics, and quantum computing.
What did the Nobel laureates do?
For centuries, individuals have been creating colored glass by tinting it with a small quantity of some compound. How a lot of the compound, or dopant, is added and the way the glass is ready modified which color the glass lastly had. By the late Nineteen Seventies, scientists had developed methods to deposit very skinny movies on different surfaces and observe quantum results in the movies. But they didn’t have a cloth per se — an object wholly reigned by quantum results. In the early Eighties, Alexei Ekimov, from the erstwhile Soviet Union, and his colleagues modified this. They added totally different quantities of copper chloride to a glass earlier than heating it to totally different temperatures for various durations, monitoring the dopants’ construction and properties. They discovered that the glass’s color modified relying on the scale of the copper chloride nanocrystals (which trusted the preparation course of) — a telltale signal that the crystals had been quantum dots. In 1983, a gaggle led by Louis Brus in the U.S. succeeded in making quantum dots in a liquid — fairly than trapped inside glass, as in Dr. Ekimov’s work. Both Dr. Brus and Dr. Ekimov additional studied quantum dots, figuring out a mathematical description of their behaviour and the way it associated to their construction. But each of them lacked one factor: a easy option to make quantum dots with simply the proper properties.
A staff led by Moungi Bawendi on the Massachusetts Institute of Technology achieved this in 1993, with the hot-injection methodology. A reagent is injected right into a fastidiously chosen solvent (with a excessive boiling level) till it’s saturated, and heated till the expansion temperature, that’s, when the reagent’s atoms clump collectively to type nanocrystals in the answer. Larger crystals type if the answer is heated for longer. Their delivery inside a liquid makes their surfaces easy. Finally, crystals of the specified dimension can merely be filtered out. This methodology accelerated the adoption of quantum dots in a spread of applied sciences.
What are quantum dots’ purposes?
An array of quantum dots could be a TV display by receiving electrical indicators and emitting gentle of totally different colors. Scientists can management the trail of a chemical response by inserting some quantum dots in the combination and making them launch electrons by shining gentle on them. If one of the power ranges an electron jumps between in a quantum-dot atom is the conduction band, the dot can function like a semiconductor. Also, photo voltaic cells made with quantum dots are anticipated to have a thermodynamic effectivity as excessive as 66%. A quantum dot can even spotlight a tumour {that a} surgeon must take away, hasten chemical reactions that extract hydrogen from water, and as a multiplexer in telecommunications.
