Water-soluble Quantum Dots (QDs) are highly sensitive fluorescent probes that are used to study biological species. One of the most common ways to render QDs water-soluble for such applications is to apply hydrophilic thiolated ligands to the QD surface. However, these ligands are labile and can be easily exchanged on the QD surface, which can severely limit their application. One way to improve stability is to increase the number of thiols per ligand, but this effect has not been quantified.  To investigate the binding and exchange of monodentate and bidentate ligands on the QD surface, we expose them to fluorescent thiol ligands, and monitor the ligand exchange by absorbance spectroscopy and F�rster Resonance Energy Transfer (FRET). Furthermore, by employing FRET at the single molecule level, the distribution in the ligand exchange to each QD is quantified. These results will contribute to develop better methods of modifying QDs for biological applications.

Binding and exchange of thiol ligands (R-SH) to water-soluble quantum dots monitored by ensemble and single particle spectroscopy

243rd National Meeting (2012)

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