Directed Assembly of Multi-Walled Nanotubes and Nanoribbons of Amino Acid Amphiphiles Using a Layer-by-Layer Approach.

Monodisperse unilamellar nanotubes (NTs) and nanoribbons (NRs) were transformed to multilamellar NRs and NTs in a well-defined fashion. This was done by using a step-wise approach in which self-assembled cationic amino acid amphiphile (AAA) forms the initial NTs or NRs, and added polyanion produces an intermediate coating. Successive addition of cationic AAA forms a covering AAA layer, and by repeating this layer-by-layer (LBL) procedure, multi-walled AAA (MWAAA) NTs and NRs are formed. This process was structurally investigated by combining small-angle neutron scattering (SANS) and cryogenic-transmission electron microscopy (cryo-TEM), confirming the multilamellar structure and the precise layer spacing. In this way we demonstrate the controlled formation of MWAAA suprastructures in a simple and reproducible fashion, which allows to control the charge on the surface of these 1D aggregates. This pathway to 1D colloidal materials is interesting for applications in life science and creating well-defined building blocks in nanotechnology.