Nobel Prize in Chemistry 2023

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Awarded to :

Moungi G. Bawendi
Massachusetts Institute of Technology (MIT), Cambridge, MA, USA

Louis E. Brus
Columbia University, New York, NY, USA

Alexei I. Ekimov
Nanocrystals Technology Inc., New York, NY, USA


“for the discovery and synthesis of quantum dots”


Quantum dots are nanoparticles. They are so tiny that their size determines their properties. 

Quantum Dot:

A quantum dot is a nanometer-sized semiconductor particle traditionally with a core-shell structure.

They were first discovered in 1980.

They have the same structure and atomic composition as bulk materials, but their properties can be tuned using a single parameter, the particle’s size.

Quantum dots were first produced by Alexei Ekimov and Louis Brus.

Quantum dots can be classified into different types based on their composition and structure.

Core-Type Quantum Dots:

These nano dots can be single component materials with uniform internal compositions, such as chalcogenides (selenides, sulfides or tellurides) of metals like cadmium, lead or zinc, example, CdTe or PbS. The properties can be changed by simply changing the crystallite size.

Core–shell semiconductor nanocrystal:

Core–shell semiconducting nanocrystals (CSSNCs) are a class of materials which have properties intermediate between those of small, individual molecules and those of bulk, crystalline semiconductors. They are unique because of their easily modular properties, which are a result of their size. These nanocrystals are composed of a quantum dot semiconducting core material and a shell of a distinct semiconducting material. The core and the shell are typically composed of type II–VI, IV–VI, and III–V semiconductors, with configurations such as CdS/ZnS, CdSe/ZnS, CdSe/CdS, and InAs/CdSe (typical notation is: core/shell) Organically passivated quantum dots have low fluorescence quantum yield due to surface related trap states. CSSNCs address this problem because the shell increases quantum yield by passivating the surface trap states. In addition, the shell provides protection against environmental changes, photo-oxidative degradation, and provides another route for modularity. Precise control of the size, shape, and composition of both the core and the shell enable the emission wavelength to be tuned over a wider range of wavelengths than with either individual semiconductor. These materials have found applications in biological systems and optics.

ALLOYED QUANTUM DOTS:

An alloyed semiconductor quantum dot comprising an alloy of at least two semiconductors, wherein the quantum dot has a homogeneous composition and is characterized by a band gap energy that is non-linearly related to the molar ratio of the at least two semiconductors; 

Significance of Research:

The methods used to produce quantum dots resulted in unpredictable quality. They contained defects. They were of varying size. What the researchers wanted is all the particles in a solution to be about the same size they had to sort them after they were made.

This was a problem that this year’s third Nobel Prize Laureate in Chemistry addressed.

Moungi Bawendi and his research group successfully grown nanocrystals of a specific size.

The nanocrystals that Bawendi produced were almost perfect, giving rise to distinct quantum effects.

Potential applications of quantum dots include single-electron transistors, solar cells, LEDs, lasers, single-photon sources, second-harmonic generation, quantum computing, cell biology research, microscopy, and medical imaging. Their small size allows for some QDs to be suspended in solution, which may lead to their use in inkjet printing, and spin coating. They have been used in Langmuir-Blodgett thin films. These processing techniques result in less expensive and less time-consuming methods of semiconductor fabrication.

The luminous properties of quantum dots are utilised in display devices based on QLED technology.
In these devices, colour of some of the blue light generated by diodes is transformed into rd or green using Quantum dots. This is how three primary colours are produced in QLED Devices.  



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