Interactions between Redox Complexes and Semiconductor Quantum Dots Coupled via a Peptide Bridge

Colloidal quantum dots (QDs) have a large fraction of their atoms arrayed on their surfaces and are capped with bifunctional ligands, which make their photoluminescence highly sensitive to potential charge transfer to or from the surrounding environment. In this report, we used peptides as bridges between CdSe-ZnS QDs and metal complexes to promote charge transfer between the metal complexes and QDs. We found that quenching of the QD emission is highly dependent on the relative position of the oxidation levels of QDs and metal complex used; it also traces the number of metal complexes brought in close proximity of the nanocrystal surface. In addition, partial bleaching of the absorption was measured for the QD-metal complex assemblies. These proximity driven interactions were further used to construct sensing assemblies to detect proteolytic enzyme activity.