Reversed-Phase HPLC Separation of Water-Soluble, Monolayer-Protected Quantum Dots

Abstract

The synthesis and characterization of water-soluble, monolayer-protected CdSe and ZnSe quantum dots (QDs) is described. The QDs were prepared using various water-soluble thiol ligands in different metal-to-thiol ratios. This work presents use of reversed-phase, high-performance liquid chromatography (RP-HPLC) to separate QDs of different sizes. Polydisperse QD samples were separated into monodisperse fractions using RP-HPLC, with resulting fwhm values <12 nm. The separation is based on the polarity of the surrounding thiol as well as the size of the nanoparticle. In addition, the pH behavior of the water-soluble QDs was studied. The QDs appear to be most stable in basic solutions and are best preserved over long periods of time when dried.