International audienceWe investigated the "interdigitated double layer" strategy, with the objective to transfer to water hydrophobic photoluminescent ZnO nanocrystals (Ncs) stabilized by a hydrophobic ligand (octylamine). This strategy relies on the formation of a double layer around the Ncs by interdigitation of an added surfactant within the alkyl chains of the pristine ligand. Various surfactants were evaluated and, surprisingly, transfer could only be achieved with a limited choice of molecular structures. Among them, the family of glycolic acid ethoxylate ethers surfactant yielded transfers up to 60%. The molecular organization of the organic coating in water was characterized using dynamic light scattering, photoluminescence and NMR (including DOSY and NOESY). Our results suggest that the success of this transfer strategy depends on a subtle interplay of interactions between the added surfactant, the ligand and the surface of the Ncs. The ZnO Ncs exhibit a strong luminescence in water

International audienceThe water dispersion of luminescent nanocrystals (NCs) synthesized in organic solvent by encapsulation in a surfactant bilayer is a promising strategy for preserving the optical properties of NCs. The phase transfer of highly monodispersed ZnO NCs using the monomer, dimer, trimer and polymer of a series of alkyl ammonium surfactants is compared. Transfer yields over 60% could be obtained with the oligomers and the polymer. In contrast, we observed no measurable transfer using the single chain surfactant. NMR spectroscopy, including DOSY and NOESY, demonstrated that increasing the oligomerization number ameliorates the stability within the coating bilayer. The NCs exhibit a strong luminescence in water and show long term chemical and photo-chemical stability