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Proceedings Paper

Quantifying the density of surface capping ligands on semiconductor quantum dots
Author(s): Naiqian Zhan; Goutam Palui; Jan-Philip Merkl; Hedi Mattoussi
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Paper Abstract

We have designed a new set of coordinating ligands made of a lipoic acid (LA) anchor and poly(ethylene glycol) (PEG) hydrophilic moiety appended with a terminal aldehyde for the surface functionalization of QDs. This ligand design was combined with a recently developed photoligation strategy to prepare hydrophilic CdSe-ZnS QDs with good control over the fraction of intact aldehyde (-CHO) groups per nanocrystal. We further applied the efficient hydrazone ligation to react aldehyde-QDs with 2-hydrazinopyridine (2-HP). This covalent modification produces QD-conjugates with a well-defined absorption feature at 350 nm ascribed to the hydrazone chromophore. We exploited this unique optical signature to accurately measure the number of aldehyde groups per QD when the fraction of LA-PEG-CHO per nanocrystal was varied. This allowed us to extract an estimate for the number of LA-PEG ligands per QD. These results suggest that hydrazone ligation has the potential to provide a simple and general analytical method to estimate the number of surface ligands for a variety of nanocrystals such as metal, metal oxide and semiconductor nanocrystals.

Paper Details

Date Published: 12 March 2015
PDF: 11 pages
Proc. SPIE 9338, Colloidal Nanoparticles for Biomedical Applications X, 93381A (12 March 2015); doi: 10.1117/12.2079590
Show Author Affiliations
Naiqian Zhan, Florida State Univ. (United States)
Goutam Palui, Florida State Univ. (United States)
Jan-Philip Merkl, Florida State Univ. (United States)
Univ. Hamburg (Germany)
Hedi Mattoussi, Florida State Univ. (United States)


Published in SPIE Proceedings Vol. 9338:
Colloidal Nanoparticles for Biomedical Applications X
Wolfgang J. Parak; Marek Osinski; Xing-Jie Liang, Editor(s)

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