Chains, sheets, and droplets: assemblies of hydrophobic gold nanocrystals with saturated phosphatidylcholine lipid and squalene.

Assemblies of saturated 1,2-diacylphosphatidylcholine lipid and hydrophobic dodecanethiol-capped 1.8 nm diameter gold nanocrystals were studied as a function of lipid chain length and the addition of the naturally occurring oil, squalene. The gold nanocrystals formed various lipid-stabilized agglomerates, sometimes fusing with lipid vesicle bilayers. The nanocrystal assembly structure depended on the hydrocarbon chain length of the lipid fatty acids. The lipid with the shortest fatty acid length studied, dilauroylphosphatidylcholine, created extended chains of gold nanocrystals. The lipid with slightly longer fatty acid chains created planar sheets of nanocrystals. Further increases of the fatty acid chain length led to spherical agglomerates. The inclusion of squalene led to lipid- and nanocrystal-coated oil droplets.