Energy Transfer, Charge Separation and Electric Field Controlled Single Particle Photoluminescence Spectroscopy with Semiconductor Nanocrystals
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Date: 08-21-2006
Start Time:
2:00pm
End Time: 3:00pm
Speaker: Andrey L Rogach
From:
Ludwig-Maximilians-Universität München, Germany
Location: Interschool Lab, 7th floor, Schapiro/CEPSR
Hosted by:
Center for Integrated Science
Abstract:
Colloidal semiconductor nanocrystals can be produced nowadays in a variety of sizes, shapes and compositions. Due to their flexible surface chemistry, colloidal nanocrystals are also very attractive objects for use as building blocks in different functional structures within the bottom-up self-assembly approaches. In this presentation, we touch three different topics related to semiconductor nanocrystal assemblies and physics, as outlined in the title. We start with discussion of energy transfer in multilayer structures comprising luminescent CdTe nanocrystals, which are constructed in an energy gap gradient manner, and report on a highly efficient funneling of excitation energy from layers comprising smaller nanocrystals towards the layer with the largest nanocrystals. Further on, we show that nanocrystals of CdSe, CdTe or InP can very effectively photosensitize needle-like fullerene microcrystals that act as photoconductors, and discuss this in terms of a “photodoping” effect based on the charge separation. Finally, we present single particle photoluminescence spectroscopy data on the “nanocrystals of mixed dimensionality”, consisting of spherical CdSe cores surrounded by elongated CdS shells. The Stark effect is in particular pronounced in these nanorod-like particles, and we demonstrate this by direct manipulation of the excited state of the nanorods using strong external electric fields. In the hybrid structures of CdSe/CdS nanorods and organic dye molecules, electrical control of energy transfer is possible, which can lead to realization of a single molecule field effect switch.