  The assembly of aligned carbon nanotubes (CNT) into fibers (CNTF) is a
convenient approach to exploit and apply the unique physico-chemical properties
of CNTs in many fields. CNT functionalization has been extensively used for
their implementation into composites and devices. However, CNTF
functionalization is still in its infancy, due to the challenges associated
with preservation of CNTF morphology. Here, we report a thorough study of the
gas-phase functionalization of CNTF fabrics using ozone that was generated in
situ from a UV-source. By contrast with liquid-based oxidation methods, this
gas-phase approach preserves CNTF morphology, whilst notably increasing its
hydrophilicity. The functionalized material is thoroughly characterized by
Raman, XPS, TEM and SEM. Its newly acquired hydrophilicity enables CNTF
electrochemical characterization in aqueous media, which was not possible for
the pristine material. Through comparison of electrochemical measurements in
aqueous electrolyte and ionic liquid we decouple the effects of
functionalization on pseudocapacitive reactions and quantum capacitance. The
functionalized CNTF fabric is successfully used as active material and current
collector in all-solid supercapacitor flexible devices with ionic liquid-based
polymer electrolyte.
