Nanocrystal quantum dots and interfaces

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In the blooming field of nanotechnology, we are still in the infancy of tool development at this small scale. The interaction of these tools with the environment surrounding them, including complex molecules which can be bigger than the tool itself (!), is not well understood. The tools we are interested in are nanocrystals made of semiconductors which are so small that one could fit more than ten thousands of them on the edge of a piece of paper. They are also called quantum dots to underline how their behavior is governed by the laws of quantum mechanics. In this sense, they behave like artificial atoms for which we can engineer the properties eventually leading to novel materials. However, we don't have the equivalent of a periodic table of elements to guide us on how the nanocrystals interact together and with other molecules. In this research program, we will gather more information on these interactions by two different ways. First, we will look at quantum dots embedded in a different semiconductor and placed at various distances from its surface. As the semiconductor-semiconductor interface has well-known properties, this will allow us to study the role played by the surface exposed to air. We will then control the surface environment by adding different substances on it to see how the quantum dots interact with the substances. To observe these effects, we will monitor the spectrum of the light emitted by quantum dots. Second, we will study nanocrystals which are directly exposed to a layer of ligands (molecules bonding with the nanocrystals) and then the external environment. Again we will control the environment and observe the effect of different ligands, but to obtain more precise information, we will look at the emission spectrum of one nanocrystal at a time. The results of this work will help other nanotechnologists determine if the problems they encounter are due to an interaction with the outside environment and find ways to solve these problems. Moreover, our research is likely to have an impact in biology where nanocrystals are used like a light beacon to find biomolecules which would otherwise be invisible. In the long-term, applications of our research in the life sciences could help improve the health of Canada's citizens.