Surface characterization of hydrophobic core-shell QDs using NMR techniques

Chengqi Zhang; Birong Zeng; Goutam Palui; Hedi Mattoussi

doi:10.1117/12.2291041

23 February 2018 Surface characterization of hydrophobic core-shell QDs using NMR techniques

Chengqi Zhang, Birong Zeng, Goutam Palui, Hedi Mattoussi

Proceedings Volume 10507, Colloidal Nanoparticles for Biomedical Applications XIII; 105070Q (2018) https://doi.org/10.1117/12.2291041
Event: SPIE BiOS, 2018, San Francisco, California, United States

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.

Citation Download Citation

Chengqi Zhang, Birong Zeng, Goutam Palui, and Hedi Mattoussi "Surface characterization of hydrophobic core-shell QDs using NMR techniques", Proc. SPIE 10507, Colloidal Nanoparticles for Biomedical Applications XIII, 105070Q (23 February 2018); https://doi.org/10.1117/12.2291041

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