Characterizing mixed phosphonic acid ligand capping on CdSe/ZnS quantum dots using ligand exchange and NMR spectroscopy

Stephen K. Davidowski, Carmen E. Lisowski, Jeffery Yarger

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

The ligand capping of phosphonic acid functionalized CdSe/ZnS core-shell quantum dots (QDs) was investigated with a combination of solution and solid-state 31P nuclear magnetic resonance (NMR) spectroscopy. Two phosphonic acid ligands were used in the synthesis of the QDs, tetradecylphosphonic acid and ethylphosphonic acid. Both alkyl phosphonic acids showed broad liquid and solid-state 31P NMR resonances for the bound ligands, indicative of heterogeneous binding to the QD surface. In order to quantify the two ligand populations on the surface, ligand exchange facilitated by phenylphosphonic acid resulted in the displacement of the ethylphosphonic acid and tetradecylphosphonic acid and allowed for quantification of the free ligands using 31P liquid-state NMR. After washing away the free ligand, two broad resonances were observed in the liquids' 31P NMR corresponding to the alkyl and aromatic phosphonic acids. The washed samples were analyzed via solid-state 31P NMR, which confirmed the ligand populations on the surface following the ligand exchange process.

Original languageEnglish (US)
Pages (from-to)234-238
Number of pages5
JournalMagnetic Resonance in Chemistry
Volume54
Issue number3
DOIs
StatePublished - Mar 1 2016

Keywords

  • CdSe/ZnS
  • NMR
  • phosphonic acid
  • quantum dots

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)

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