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Proceedings Paper

Surface characterization of hydrophobic core-shell QDs using NMR techniques
Author(s): Chengqi Zhang; Birong Zeng; Goutam Palui; Hedi Mattoussi
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Paper Abstract

Using a few solution phase NMR spectroscopy techniques, including 1H NMR and 31P NMR, we have characterized the organic shell on CdSe-ZnS core-shell quantum dots and tracked changes in its composition when the QD dispersions are subjected to varying degrees of purification. Combining solution phase NMR with diffusion ordered spectroscopy (DOSY), we were able to distinguish between freely diffusing ligands in the sample from those bound on the surfaces. Additionally, matrix assisted laser desorption ionization (MALDI) and FTIR measurements were used to provide complementary and supporting information on the organic ligand coating for these nanocrystals. We found that the organic shell is dominated by monomeric or oligomeric n-hexylphosphonic acid (HPA), along with small portion of 1-hexadecyl amine (HDA). The presence of TOP/TOPO (tri-n-octylphosphine / tri-noctylphosphine oxide) molecules is much smaller, even though large excess of TOP/TOPO were used during the QD growth. These results indicate that HPA (alkyl phosphonate) exhibits the strongest coordination affinity to ZnS-rich QD surfaces grown using the high temperature injection route.

Paper Details

Date Published: 23 February 2018
PDF: 8 pages
Proc. SPIE 10507, Colloidal Nanoparticles for Biomedical Applications XIII, 105070Q (23 February 2018); doi: 10.1117/12.2291041
Show Author Affiliations
Chengqi Zhang, Florida State Univ. (United States)
Birong Zeng, Xiamen Univ. (China)
Goutam Palui, Florida State Univ. (United States)
Hedi Mattoussi, Florida State Univ. (United States)

Published in SPIE Proceedings Vol. 10507:
Colloidal Nanoparticles for Biomedical Applications XIII
Marek Osiński; Wolfgang J. Parak; Xing-Jie Liang, Editor(s)

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