Large fluorescence quantum yield and low size dispersion from CdSe/ZnSe core/shell nanocrystals

We improved on existing synthesis methods to grow CdSe nanocrystals that present a 0.05 relative size dispersion, as seen in transmission electron microscopy, and correlated to photoluminescence line widths below View the MathML source. The additional growth of a ZnSe shell onto these CdSe cores leads to core/shell nanocrystals that exhibit room temperature photoluminescence quantum yields as high as 0.85. The as-grown nanocrystals are passivated by the growth solvent organic molecules, which present hydrophobic ends. We show that the quantum yield of the core/shell nanocrystals is unchanged, whereas it drops sharply for core-only nanocrystals, upon the exchange of these molecules with ligands bearing hydrophilic ends. This provides highly fluorescent particles that can be dispersed in strong polar solvents, such as water.