Mechanistic Insight into the Formation of Cationic Naked Nanocrystals Generated Under Equilibrium Control

Pre-JCESR stripping chemistries (for cationic NC):
NOBF4 (strong oxidant, not suitable for many compositions, ~$600/mol)
Et3OBF4 (mild, but still causes adatom desorption for some sensitive compositions, ~$800/mol)

New ligand-stripping chemistry developed within JCESR:
BF3:Et2O (mildest stripping reagent to date, <$18/mol)

Scientific Achievement

Developed a class of ligand-stripping reagents that stabilize the nanocrystal (NC) surface during the stripping reaction, leading to improved dispersibility.

Significance and Impact

  • NCs show promise as energy storage and conversion materials, but they are often synthesized with surface-bound organic ligands that improve dispersibility while blocking charge transport. Existing methods for removing these ligands are expensive and lead to poor dispersibility for some materials.
  • Ligand stripping under equilibrium control can be used to generate materials that are impossible to produce by existing methods at low cost.

Research Details

1H-DOSY showed that ligand-stripping proceeds through the formation of a Lewis acid-base adduct, which stabilizes the NC surface. ESI-MS showed that this adduct breaks down to form neutral species and non-coordinating counter-ions. The resulting NC dispersions were readily deposited as thin films or polymer-NC hybrids.


Work performed at Lawrence Berkeley National Laboratory (JCESR partner) by S. E. Doris, J. J. Lynch, C. Li, A. W. Wills, J. J. Urban and B. A. Helms . J. Am. Chem. Soc. 2014, 136 (44), 15702–15710.

DOI: 10.1021/ja508675t

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