Ratiometric Sensing of Unlabeled Analytes via Quantum Dot/Forster Resonance Energy Transfer

In this thesis, the synthesis of a highly robust blue emitting CdZnS/ZnS quantum dots (QDs) is discussed. With a narrow size distrubution and emission profile these QDs are very stable and can be efficiently functionalized using a variety of strategies. Surface modfications of these QDs have been studied to understand there role as photocatalyst for the production of H2. They were also used as a platform for making QD ratiometric sensors. The control of Förster Resonance Energy Transfer (FRET) in semiconductor quantum dots as an efficient way to impart sensing capability in QDs is discussed. The sensors function by manipulating the efficiency of FRET from a QD donor to a fluorescent organic dye acceptor that has a chemically sensitive absorption spectrum. Energy transfer efficiency from the QD to dye is modulated when environmental factors cause the dye absorption to move into or out of resonance with the QD luminescence. The emission of the construct has a ratiometric or ‘self referencing’ response towards targeted analytes. From this a coupled dye-QD ratiometric FRET sensor has been developed that is capable of detecting aqueous Hg2+, a toxic metal that directly quenches semiconductor QDs. A novel approach for unlabeled biological FRET sensing using a DNA functionalized CdZnS/ZnS QD is also discussed. This approach will open the door for QDs as efficient biomarkers.