Premium
Characterizing mixed phosphonic acid ligand capping on CdSe/ZnS quantum dots using ligand exchange and NMR spectroscopy
Author(s) -
Davidowski Stephen K.,
Lisowski Carmen E.,
Yarger Jeffery L.
Publication year - 2016
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.4372
Subject(s) - chemistry , ligand (biochemistry) , nuclear magnetic resonance spectroscopy , alkyl , proton nmr , spectroscopy , crystallography , stereochemistry , organic chemistry , biochemistry , receptor , physics , quantum mechanics
The ligand capping of phosphonic acid functionalized CdSe/ZnS core–shell quantum dots (QDs) was investigated with a combination of solution and solid‐state 31 P 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 31 P 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 31 P liquid‐state NMR. After washing away the free ligand, two broad resonances were observed in the liquids' 31 P NMR corresponding to the alkyl and aromatic phosphonic acids. The washed samples were analyzed via solid‐state 31 P NMR, which confirmed the ligand populations on the surface following the ligand exchange process. Copyright © 2015 John Wiley & Sons, Ltd.