Quantum Dots (QDs) are susceptible to fluorescence intermittency known as blinking which introduces ambiguity in biological imaging applications and lowers efficiency in light-conversion technologies.  We are particularly interested in mitigating blinking by exploring the ligand surface chemistry on the QD. The non-emissive dark state of the QD can in part be attributed to the trapping of the excited state electron by surface defect sites.  Thiol-based ligands can passivate these defect sites by donating electrons and therefore have shown promise for QD blinking-suppression, but with mixed results depending on the specific type of QD and ligand.  To further explore this ambiguity in blinking suppression vs. enhancement, we aim to systematically characterize the blinking statistics of QDs coated with various thiol-based ligands using single-particle fluorescence microscopy.  Starting with CdSe/ZnS (core/shell) QDs, we performed ligand exchange to a variety of water-soluble thiols including glutathione, D-penicillamine, and cysteine.  We analyzed the fluorescence intensity distributions and quantified the waiting times of the on and off states.  D-penicillamine coated QDs exhibited the greatest on-to-off state intensity ratio, followed by glutathione, and cysteine.  We aim to rationalize our trends in blinking statistics by comparing thiol reduction potentials and relative QD-ligand stability in an aqueous environment.

Comparison of quantum dot blinking behavior with different thiol-based ligands

2019 Spring National Meeting

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