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.