Colloidal nanocrystals surface-coated with organic ligands offer nanoscale platforms with unique optical and physical properties, which can be tuned by varying the nature and overall structure of the surface ligands. Despite advances in the growth and functionalization of these materials, limited information about the molecular arrangements of those ligands is available. We hereby apply several NMR spectroscopy techniques to characterize the ligand structure(s) of the as prepared hydrophobic colloidal nanocrystals as well as after ligand and phase transfer to water. For this, we combine the proton signatures of the ligands with diffusion ordered spectroscopy (DOSY) to distinguish surface-coordinated ligands from those freely-diffusing in the medium. We then combine 1H, 31P and HSQC spectroscopy techniques to identify the composition of the surface bound ligands. We then compare the sharp signature(s) of the lateral groups of the surface-bound ligands to external standards to extract estimate for the number and stoichiometry of ligands per nanocrystal.

Characterizing the ligand structure and stoichiometry on quantum dots using NMR spectroscopy

255th National Meeting (2018)

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