Gold nanoparticles grafted with chemically incompatible ligands.

Janus-type structures were obtained from gold nanoparticles grafted with two types of chemically incompatible mesogenic ligands with a strong tendency for nano-segregation. A lamellar arrangement, in which metallic nanoparticle-rich sublayers are separated by organic ligand-rich sublayers of various composition, was formed due to the ligand segregation process. The layers could be easily aligned by mechanical shearing; for most materials the layer normal was parallel to the shearing direction but perpendicular to the shearing gradient, such transverse mode is only rarely observed for lamellar materials. Reversible changes of layer thickness under UV light were observed due to the presence of an azo-moiety in the organic ligand molecules.