OVERVIEW ON THE MAJOR RESEARCH ACTIVITIES ON CARBON NANOTUBES BEING DONE IN AMERICA, EUROPE AND ASIA - Carbon Nanotubes: From Bench Chemistry to Promising Biomedical Applications - page 298

offers several advantages towards the development of electronics and
photovoltaics: irst of all, it presents tremendous electron-accepting and
electron-conducting features with a ive-fused ring π-system. Additionally,
it favours the dispersion of SWCNTs by π-π interactions, thus determining
individual SWCNTs in solution. Therefore, it guarantees uniform samples and
ideal conductivity towards advanced (opto)electronic devices.
π-π interactions were also employed to anchor an electron donor (based
on π-extended tetrathiafulvalene [exTTF]) to the surface of SWCNTs. 189 A full
spectroscopic characterisation showed that new conduction band electrons,
injected from photoexcited exTTF, shifted the transitions normally associated
with the van Hove singularities to lower energies.
Alternative photoactive electrodes have been produced by SWCNTs
bearing phthalocyanine chromophores 190 or by grafting polymers onto
SWCNTs either via free-radical polymerisation of (vinylbenzyl)trimethylam
monium chloride (VBTA) into (PVBTA n + ) or by simply wrapping them around
the tubes in the form of aqueous suspensions of positively charged SWCNT/
PVBTA n + . 191 The supramolecular complexes consisted of versatile donor-
acceptor nanohybrids obtained by electrostatic/van der Waals interactions
between covalent SWCNT-PVBTA n + and/or non-covalent SWCNT/PVBTA n +
and porphyrins (H 2 P 8- and/or ZnP 8- ). Photoexcitation of these nanohybrids
afforded radical ion pairs, similarly to those produced by the above-mentioned
perylene dye.
More complex nanometre scale structures, such as SWCNT-ZnPc
conjugates 192 have been produced through click chemistry of SWCNTs with
4-(2-trimethylsilyl)ethynylaniline and the subsequent attachment of a zinc-
phthalocyanine (ZnPc) derivative using the Huisgen 1,3-dipolar cycloaddition
(“click chemistry”). The complex showed remarkable properties, as
demonstrated by monochromatic internal photoconversion eficiencies of
17.3% when the SWCNT-ZnPc hybrid material was tested as photoactive
material in an ITO photoanode.
9.3.4 Funconalisaon of CNTs
In Prato's laboratory, scientists are also developing new procedures for
the strategic functionalisation of CNTs. As mentioned before, they could
be considered the pioneers of the 1,3-dipolar cycloaddition of azomethine
ylides applied onto fullerenes irst and nanotubes later. Besides that, many
other methodologies have been explored and applied on the surface and/or
tips of CNTs, among which a recent publication reported a microwave (MW)
process to functionalised nanostructures in ionic liquids. 193 The application
of MW irradiation and ionic liquids (IL) on the cycloaddition of azomethine