Quantum Dot Metrics for Preparative Chemistry and Fluorescence Applications

Colloidal semiconductor quantum dots (QDs) are considered to be a promising candidate for bio-imaging and solar cells because of their extraordinary photo-physical properties. The ultimate goal of this dissertation is to design a reliable matrix and a reproducible method to prepare QDs-based biocompatible probe for fluorescence applications. Synthesis of quantum dots requires a large amount of ligands to improve the stability at high temperature. However, for further application and surface modification of QDs, excess ligands must be removed. In this dissertation, I will first describe using gel permeation chromatography (GPC) as a media to purify different types of QDs. A more systematic study of the tolerance of the GPC purification method against other nanocrystal materials will also be addressed. I will further demonstrate that GPC can be used as a reactor to perform solvent change and ligand exchange reactions with QDs. With the help of GPC purification technique, well-isolated and characterized nanomaterials are prepared to study the sequential chemistry of QDs. I specifically study the effect of neutral ligands on the photo-physical properties of the QDs and their influence on the inorganic surface overcoating (shell growth) reaction. This information is essential in preparing bio-compatible QDs with high brightness and long term stability. The GPC purified QDs have also been used to perform surface modification reactions with a range of polymeric imidazole ligands (PILs). The PIL capped QDs display colloidal stability, low toxicity and non-specific binding, and high brightness in aqueous solution. Measles virus, a model envelope virus, has been labeled by these bio-compatible QDs and retained its infectious ability against host cells