Nanotubes and nanotube array structures comprise (a) a nanotube having an
inner wall portion; and (b) a bilayer coating formed on the inner wall
portions, with the bilayer coating comprised of surfactants. A secondary
compound such as a protein, peptide or nucleic acid may be associated
with the bilayer coating. The structures are useful for, among other
things, affinity purification, catalysis, and as biochips.