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NSTC/AMPAC Seminars

Tuning Organic-Inorganic and Inorganic-Inorganic Interfaces of Quantum Dots for Quantitative Fluorescence Applications

Colin D. Heyes, Ph.D.
Department of Chemistry and Biochemistry
University of Arkansas

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Light refreshments will be served

Contact:

Ushaben Lal
NanoScience Technology Center
Phone: 407-882-0032
Email: ulal@ucf.edu

Date: Wednesday, March 13, 2013; 2:00pm - 3:00pm
Location: Research Pavilion, Room 475 (NanoScience Technology Center)

Due to the high surface-to-volume ratio of nanoparticles, the fluorescence properties of colloidal quantum dots (QDs) are strongly affected by the various interfaces present. Simple core-only QDs have an inorganic-organic surface-ligand interface, while core-shell (or core-multishell) quantum dots have, in addition, inorganic-inorganic core-shell interfaces. We have systematically tuned the interfaces of cadmium-chalcogenide or copper-indium-chalcogenide cores and upon adding cadmium- and zinc-chalcogenide shells. The optical and structural properties at the ensemble and single particle level are analyzed by a combination of time-resolved fluorescence spectroscopy, single-particle fluorescence microscopy, quantitative FT-IR absorption spectroscopy, X-ray photoelectron (XPS) spectroscopy and high-resolution TEM/HAADF-STEM/EELS microscopy. In particular, we explore connections between the structural details of the interfaces and the quantum yield, radiative and non-radiative excited state decay rates, ligand binding, fluorescence blinking and the formation of a dark fraction. We also evaluate the response of these properties to external environments will be discussed to help devise strategies to tailor QDs for various applications. To illustrate these connections, I will present several applications utilizing bandgap and lifetime engineering of quantum dots – in particular for ultrasensitive biophysical and biomedical imaging.

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