Ammonium lithocholate nanotubes: stability and copper metallization.

Terech, Pierre; Sangeetha, Neralagatta M; Bhat, Shreedhar; Allegraud, Jean-Jacques; Buhler, Eric

Ammonium lithocholate nanotubes (NHLC) have been prepared in alkaline ammonia solutions and exhibited remarkable monodisperse cross-sectional dimensions (external diameter = 52 nm) as shown by cryo-transmission electron microscopy measurements. A classical electroless metallic replication method was used with a single poly(ethylene-imine) PEI layer coating the negatively charged NHLC nanotubes. Short copper rods (external diameter ∼ 80 nm) were observed by scanning electron microscopy that corresponded to the original organic templates. The results obtained in acidic conditions are analyzed in terms of the lifetime of the self-assembled structures and formation of bundles of tubes. Dynamic light scattering measurements and optical observations show that the system in the presence of controlled amounts of hydrochloric acid is stable enough to account for a metallic replication in acidic conditions. An average apparent diffusion coefficient of the organic NHLC assemblies is extracted (∼ 9.8 × 10 nm s) in homogeneous suspensions where bundles have been dispersed by the acidic additions.