Nobel Prize in Chemistry 2023, Quantum Dots, Applications of Quantum Dots

Nobel Prize in Chemistry 2023

• Context (TH | IE | IE): The Nobel Prize in Chemistry 2023 has been awarded to Moungi G. Bawendi, Louis E. Brus and Alexei I. Ekimov for discovering and synthesising quantum dots.

What are Quantum Dots?

• Each element’s properties are defined by its atomic structure, primarily the number and arrangement of electrons around the nucleus.
• All pure elements display consistent properties, regardless of their size. For example, every piece of gold, whether a large 100 gm or a small 10 mg, has the same properties (fundamental facts).
• However, at the nanoscale, when the matter is really small, the electrons are squeezed together, so its properties depend on size.
• Quantum dots are semiconductor nanoparticles that exhibit size and composition-dependent optical and electronic properties.

Nanoscale materials exhibit size-dependent properties due to quantum forces, while gravity and classical physics govern at the macroscopic scale. Nanoparticles: Particles whose sizes range between 1 to 100 billionth of a metre. Semiconductor: A material with an electrical conductivity value falling between a conductor (such as copper) and an insulator (such as glass).

• Quantum dots constitute a new class of materials that is neither molecular nor bulk material.
• They have the same structure and atomic composition as bulk materials, but their properties can be tuned using a single parameter, i.e., the particle’s size.

What did Ekimov, Brus, and Bawendi do?

Dr. Ekimov’s Research

• Dr. Ekimov used copper chloride to colour glass under various heating and cooling conditions.
• He discovered that the glass’s light absorption depended on the particle size of copper chloride.
• Larger particles behaved as expected, but smaller particles absorbed bluer light.
• Ekimov recognised this as a size-dependent quantum effect.

Dr. Brus’s Reseacrh

• Dr. Brus prepared similar size-dependent particles (crystals) of cadmium sulphide in a liquid solution rather than in a glass. This allowed the researchers to manipulate better and study the crystals.

Dr. Bawendi Research

• Dr. Bawendi developed a technique to make these peculiar crystals, i.e. quantum dots, of well-defined sizes and with high optical quality.

What is the Discovery of Quantum Dots Important

• At the nanoscale, quantum dots attain new, size-dependent properties that can be harnessed and controlled for novel applications.

Applications of Quantum Dots

• Optoelectronics and Displays: Quantum dots are used in displays and lighting to enhance colour accuracy, brightness, and energy efficiency. QLED (Quantum-dot Light Emitting Diode) technology has led to the developing of high-quality, vivid displays in televisions and monitors.
• Biological Imaging: Quantum dots are valuable in biological and medical imaging. They offer bright, stable fluorescence for precise cell and biomolecule tracking in living organisms.
• Solar Cells: Quantum dots are studied for use in solar cells to boost efficiency and broaden the light absorption spectrum.
• Quantum Dot Lasers: They are used to develop lasers with low threshold current and tunable emission, which find applications in telecommunications and optical signal processing.
• Quantum Dot Computing: Quantum dots may serve as qubits (quantum bits) in quantum computing, advancing the development of robust, efficient quantum computers.
• Sensors and Detection: Quantum dots can be used in sensors for substance detection and environmental monitoring due to their sensitivity and tunable traits.
• Telecommunications: Quantum dots can amplify and transmit optical signals efficiently.
• Material Science: Quantum dots provide insights into nanoscale quantum effects and material behaviour, driving innovation for novel materials and technologies.
• Energy Storage: Quantum dots are explored for use in energy storage devices (like batteries and supercapacitors), where their unique properties can enhance energy storage and efficiency.
• Drug Delivery: Quantum dots serve as drug delivery carriers in medicine, enabling precise and controlled pharmaceutical release. E.g., cancer treatments.
• Environmental Remediation: Quantum dots have applications in environmental remediation, such as removing pollutants from water and soil through photocatalysis.
• Security and Authentication: Tunable optical properties of quantum dots enhance their value in anti-counterfeiting measures used in document and product security features.