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Mahesh

08/10/23 04:13 AM IST

Significance of quantum dots in nanotechnology

In News
  • 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”.
Quantum Dots
  • A quantum dot is a really small assembly of atoms (just a few thousand) around a few nanometres wide.
  • The ‘quantum’ in its name comes from the fact that the electrons in these atoms have very little space to move around, so the crystal as a whole displays the quirky effects of quantum mechanics — effects that otherwise would be hard to ‘see’ without more sophisticated instruments.
  • Quantum dots have also been called ‘artificial atoms’ because the dot as a whole behaves like an atom in some circumstances.
Why they are of interest?
  • There are two broad types of materials: atomic and bulk. Atomic of course refers to individual atoms and their specific properties.
  • Bulk refers to large assemblies of atoms and molecules.
  • Quantum dots lie somewhere in between and behave in ways that neither atoms nor bulk materials do.
  • One particular behaviour distinguishes them: the properties of a quantum dot change based on how big it is.
  • Just by tweaking its size, scientists can change, say, the quantum dot’s melting point or how readily it participates in a chemical reaction.
  • When light is shined on a quantum dot, it absorbs and then re-emits it at a different frequency.
  • Smaller dots emit bluer light and larger dots, redder light.
  • This happens because light shone on the dot energises some electrons to jump from one energy level to a higher one, before jumping back down and releasing the energy at a different frequency.
  • So, quantum dots can be easily adapted for a variety of applications including surgical oncology, advanced electronics, and quantum computing.
Applications
  • An array of quantum dots can be a TV screen by receiving electric signals and emitting light of different colours.
  • Scientists can control the path of a chemical reaction by placing some quantum dots in the mix and making them release electrons by shining light on them.
  • If one of the energy levels an electron jumps between in a quantum-dot atom is the conduction band, the dot can operate like a semiconductor.
  • Also, solar cells made with quantum dots are expected to have a thermodynamic efficiency as high as 66%.
  • A quantum dot can also highlight a tumour that a surgeon needs to remove, hasten chemical reactions that extract hydrogen from water, and as a multiplexer in telecommunications.
Source- The Hindu

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