Using facile diazonium chemistry, sulfonate groups have been covalently attached to single wall carbon
nanotubes. The resulting sulfonated tubes form a stable aqueous dispersion in the presence of
pyrrole monomer. Subsequent electropolymerisation results in a conductive, electroactive polypyrrole
doped with sulfonated tubes being formed at unusually low potentials. The potential of this
material as a host matrix for biomolecules has been demonstrated by entrapping horse-radish
peroxidase directly in the polypyrrole during composite formation.