Quantum Dots: Applications in Biotechnology
A quantum dot is a nanoscale crystal of semiconducting material with dimensions smaller than the Bohr exciton radius. This produces a quantum confinement effect, causing the electrons trapped in the valence band of the semiconductor to become quantised, giving them properties similar to particles in a potential well.
The first observation of optical effects of quantum dots was done by Alexei Ekimov in the early 1980s while working at the Vavilov State Optical Institute in St. Petersburg, Russia. He discovered optical transitions due to quantum confinement of electron-hole pairs in semiconductor nanocrystals known as CuCl. Independently, Louis E Brus, a researcher at AT&T labs, was the first to observe these confinement effects in colloidal solutions.
Later work by Moungi Bawendi at MIT helped develop reliable methods for synthesising high-quality quantum dots. These developments were the foundation for much of the current research on the applications of quantum dots. For their contributions to the discovery and synthesis of quantum dots, Ekimov, Brus and Bawendi were awarded the Nobel Prize in Chemistry in 2023.
Quantum dots can be made from two main types of materials. Cadmium-based dots such as CdSe are very bright, and their emission wavelengths are easily controlled by their size. However, cadmium is toxic, limiting its use in biological settings. Indium-based dots (like InP/ZnS) are safer and show promise for in vivo medical imaging.
Photoluminescence allows quantum dots to emit light under UV excitation, making them highly useful in biological imaging. Unlike organic dyes, quantum dots are more photostable and can emit under repeated UV exposure without degrading.
In his seminar, Dr. Matthew Booth highlighted some of their applications in biotechnology, such as their use in bioimaging and their potential in future vaccination programs. Since quantum dots emit specific wavelengths of NIR light, they can be used to make ‘invisible tattoos’ that can be used to track and record vaccinations. These tattoos can be scanned by equipment such as a modified smartphone camera. This technique would be helpful in developing countries where vaccine records are limited.
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This article was very well written and covered most of the material which was brought up in Dr. Matt Booth’s seminar. Well done!
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This article gives an excellent summary of Dr Booth’s lecture. I particularly enjoyed learning about the discovery of quantum dots and their key properties. It includes relevant citations and covers important topics like photoluminescence and their potential use in vaccination technology.