Many reactions use Lewis bases to exchange the L-type ligands of cadmium chalcogenide nanocrystals, but these methods ignore the anionic, X-type ligands which balance excess Cd2+. These exchange reactions cannot remove X-type ligands without charging the nanocrystals or altering the nanocrystal stoichiometry. We have found that cadmium carboxylate is removed from the surface of CdSe and CdS nanocrystals when treated with a variety of Lewis bases. We measure the number of carboxylates removed with different Lewis bases by NMR spectroscopy, from tetrahydrofuran (3% removal) to n-octylamine (93% removal). These treatments also reduce the Cd:Se ratio and reversibly quench the photoluminescence while suppressing the second electronic transition in the absorption spectra. In addition, the cadmium carboxylate complex removed by tri-n-butylphosphine has been characterized. This work emphasizes the importance of nanocrystal stoichiometry and provides a mechanism for prior ligand exchange reactions in light of a modern view of nanocrystal surfaces.

Importance of nanocrystal stoichiometry: Removal of CdX<sub>2</sub> from cadmium chalcogenides using Lewis bases

245th National Meeting (2013)

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Importance of nanocrystal stoichiometry: Removal of CdX2 from cadmium chalcogenides using Lewis bases

Importance of nanocrystal stoichiometry: Removal of CdX₂ from cadmium chalcogenides using Lewis bases