Bifunctional Multidentate Ligand Modified Highly Stable Water-Soluble Quantum Dots

We have designed and synthesized a multidentate polymer ligand used for water-solubilization of luminescent quantum dots (QDs). The synthesis of the multidentate ligand (PAA-g-MEA) was based on several thiol groups grafted to a linear polymer chain through a simple carboxy-amine coupling reaction between poly(acryl acid) (PAA) and mercaptoethylamine (MEA). Water-soluble QDs capped with these PAA-g-MEA ligands were prepared via ligand exchange from the original hydrophobic ones. The resulting PAA-g-MEA capped water-soluble QDs with relatively small hydrodynamic diameters possess higher photoluminescence quantum yields than the initial hydrophobic QDs, extraordinary stability over extended periods of time and over a broad pH range (3-14), salt concentrations (up to saturated NaCl solution), and thermal treatment at 100 degrees C.