Self-assembly of ordered nanowires in biological suspensions of single-wall carbon nanotubes

We investigate the self-assembly of ordered nanowires from length-purified single-wall carbon nanotubes (SWCNTs) in aqueous suspensions of the biological surfactant sodium deoxycholate. Macroscopically straight and nearly periodic linear arrangements of aligned individual SWCNTs are found to self-assemble in two-dimensional geometries from nanotube suspensions that are otherwise stable in the bulk, which we attribute to a dominance of surface effects under strong confinement. Directed self-assembly is explored through surface patterning, opening up new potential routes to nanotube manipulation for optical diagnostics and applications that require ordered arrangements of mutually aligned SWCNTs. The stability of these structures to thermal fluctuations and changes in solution chemistry are surveyed with near-infrared fluorescence microscopy.