IMX Seminar Series - Optical Materials
Event details
| Date | 21.11.2022 |
| Hour | 13:15 › 14:15 |
| Speaker | Prof. David Norris, ETH Zürich, Switzerland |
| Location | |
| Category | Conferences - Seminars |
| Event Language | English |
The Dream of the Perfect Nanocrystal
Quantum dots are nanometer-sized crystallites of semiconductor that have a roughly spherical shape. Due to extensive research, quantum dots are now commercially used as a robust fluorescent material in displays and lighting. However, even with our best procedures, state-of-the-art samples still contain particles with a distribution in size and shape. Because this causes variations in their optical properties, their performance for applications is reduced. This leads to a fundamental question: can we achieve a sample of semiconductor nanocrystals in which all the particles are exactly the same? In this talk we will discuss this possibility by examining two classes of nanomaterials. First, we will consider thin rectangular particles known as semiconductor nanoplatelets. Amazingly, nanoplatelet samples can be synthesized in which all crystallites have the same atomic-scale thickness (e.g., 4 monolayers). This uniformity in one dimension suggests that routes to monodisperse samples might exist. After describing the underlying growth mechanism for nanoplatelets, we will then move to a much older nanomaterial—magic-sized clusters (MSCs). Such species are believed to be molecular-scale arrangements (i.e., clusters) of semiconductor atoms with a specific (“magic”) structure with enhanced stability compared to particles slightly smaller or larger. Their existence implies that MSC samples can in principle be the same size and shape. Unfortunately, despite three decades of research, the formation mechanism of MSCs remains unclear, especially considering recent experiments that track the evolution of MSCs to sizes well beyond the “cluster” regime. Again, we will discuss the underlying growth mechanism and its implications for nanocrystal synthesis. Finally, we will present an outlook if perfect nanomaterials can be obtained.
Bio: David J. Norris received his B.S. and Ph.D. degrees in Chemistry from the University of Chicago (1990) and Massachusetts Institute of Technology (1995), respectively. After an NSF postdoctoral fellowship with W. E. Moerner at the University of California, San Diego, he led a small independent research group at the NEC Research Institute in Princeton (1997). He then became an Associate Professor (2001–2006) and Professor (2006–2010) of Chemical Engineering and Materials Science at the University of Minnesota, where he also served as Director of Graduate Studies in Chemical Engineering (2004–2010). In 2010, he moved to ETH Zurich where he is currently Professor of Materials Engineering. From 2016 to 2019 he served as the Head of the Department of Mechanical and Process Engineering. He has received the Credit Suisse Award for Best Teacher at ETH, twice the Golden Owl Award for Best Teacher in his department, the Max Rössler Research Prize, an ERC Advanced Grant, and the ACS Nano Lectureship Award. He is a Fellow of the American Physical Society and the American Association for the Advancement of Science, and an editorial board member for ACS Photonics and Nano Letters. His research focuses on how materials can be engineered to create new and useful optical properties.
Quantum dots are nanometer-sized crystallites of semiconductor that have a roughly spherical shape. Due to extensive research, quantum dots are now commercially used as a robust fluorescent material in displays and lighting. However, even with our best procedures, state-of-the-art samples still contain particles with a distribution in size and shape. Because this causes variations in their optical properties, their performance for applications is reduced. This leads to a fundamental question: can we achieve a sample of semiconductor nanocrystals in which all the particles are exactly the same? In this talk we will discuss this possibility by examining two classes of nanomaterials. First, we will consider thin rectangular particles known as semiconductor nanoplatelets. Amazingly, nanoplatelet samples can be synthesized in which all crystallites have the same atomic-scale thickness (e.g., 4 monolayers). This uniformity in one dimension suggests that routes to monodisperse samples might exist. After describing the underlying growth mechanism for nanoplatelets, we will then move to a much older nanomaterial—magic-sized clusters (MSCs). Such species are believed to be molecular-scale arrangements (i.e., clusters) of semiconductor atoms with a specific (“magic”) structure with enhanced stability compared to particles slightly smaller or larger. Their existence implies that MSC samples can in principle be the same size and shape. Unfortunately, despite three decades of research, the formation mechanism of MSCs remains unclear, especially considering recent experiments that track the evolution of MSCs to sizes well beyond the “cluster” regime. Again, we will discuss the underlying growth mechanism and its implications for nanocrystal synthesis. Finally, we will present an outlook if perfect nanomaterials can be obtained.
Bio: David J. Norris received his B.S. and Ph.D. degrees in Chemistry from the University of Chicago (1990) and Massachusetts Institute of Technology (1995), respectively. After an NSF postdoctoral fellowship with W. E. Moerner at the University of California, San Diego, he led a small independent research group at the NEC Research Institute in Princeton (1997). He then became an Associate Professor (2001–2006) and Professor (2006–2010) of Chemical Engineering and Materials Science at the University of Minnesota, where he also served as Director of Graduate Studies in Chemical Engineering (2004–2010). In 2010, he moved to ETH Zurich where he is currently Professor of Materials Engineering. From 2016 to 2019 he served as the Head of the Department of Mechanical and Process Engineering. He has received the Credit Suisse Award for Best Teacher at ETH, twice the Golden Owl Award for Best Teacher in his department, the Max Rössler Research Prize, an ERC Advanced Grant, and the ACS Nano Lectureship Award. He is a Fellow of the American Physical Society and the American Association for the Advancement of Science, and an editorial board member for ACS Photonics and Nano Letters. His research focuses on how materials can be engineered to create new and useful optical properties.
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Practical information
- General public
- Free
Organizer
- Maartje Bastings & Anirudh Natarajan
Contact
- Maartje Bastings & Anirudh Natarajan