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Polyethylene glycol-based bidentate ligands to enhance quantum dot and gold nanoparticle stability in biological media


We describe a simple and versatile scheme to prepare a series of poly(ethylene glycol)-based bidentate ligands that permit strong interactions with colloidal semiconductor nanocrystals (quantum dots, QDs) and gold nanoparticles (AuNPs) alike and promote their dispersion in aqueous solutions. These ligands are synthesized by coupling poly(ethylene glycol)s of various chain length to thioctic acid, followed by ring opening of the 1,2-dithiolane moiety to create a bidentate thiol anchoring group with enhanced affinity for CdSe-ZnS core-shell QDs. These ligands provide a straightforward means of preparing QDs and AuNPs that exhibit greater resistance to environmental changes, facilitating their effective use in bioassays and live cell imaging.

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Figure 1: Synthetic scheme.
Figure 2: 1H-NMR spectra of some of the ligands.
Figure 3: FT-IR spectra of cap-exchanged QDs and AuNPs.
Figure 4: pH stability of cap-exchanged nanoparticles.
Figure 5: Cy3-peptide titration versus 530 nm emitting QDs.


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We acknowledge NRL, Office of Naval Research (ONR), the Army Research Office (ARO) and the CB Directorate/Physical S&T Division (DTRA) for financial support. We thank Dr Horn-Bond Lin for assistance with the FTIR spectra.

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Correspondence to Hedi Mattoussi.

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Mei, B., Susumu, K., Medintz, I. et al. Polyethylene glycol-based bidentate ligands to enhance quantum dot and gold nanoparticle stability in biological media. Nat Protoc 4, 412–423 (2009).

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