March 29, 2017
Andrew B. Greytak
University of South Carolina
Assistant Professor of Chemistry
“Quantum Dot Purification and Metrics for Rational Control of Shell Growth, Ligand Exchange, and Quantum Yield”
4:10 PM, 134 Featheringill Hall Refreshments served at 3:45
Abstract:
The unique and size-tunable fluorescence and absorption spectra of nanocrystal quantum dots (QDs) have led to considerable interest and commercial development for display and lighting applications, fluorescence microscopy in biomedicine, and solution processable solar cells that can be scaled sustainably to meet demand. However, many applications of QDs depend sensitively on chemical reactivity or surface-mediated non-radiative decay rates, which depend strongly on interfacial structure. The achievement of suitable metrics to permit precise descriptions of QD samples is complicated by the fact that the surfaces of colloidal nanocrystals are subject to dynamic exchange with solution-phase species.
We have shown that gel permeation chromatography can serve as a highly repeatable method to separate QDs from small molecules on the basis of size. We are using these purified QDs as a reference point from which to study the effect of ligand association on quantum yield, to make quantitative measurements of ligand exchange and shell growth, and as a starting material in the development of robust, biocompatible QD fluorophores. By correlating these outcomes with analytical measurements of purified NCs, we hope to arrive at a set of metrics for colloidal QDs that allows their chemical and physical behavior to be abstracted from the details of earlier synthetic steps.