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 289

To a wider extent, 2D and 3D ordered networks could be generated from
1D units that were connected covalently. The research group has indeed
created multi-terminal junctions containing 1D carbon blocks in the form of
ordered networks based on carbon nanotubes (ON-CNTs). 164 These branched
structures have demonstrated speciic super-architectures (hexagonal, cubic,
square and diamond type; Fig. 9.26), which inluence both mechanical and
electronic characteristics. Hence, charges follow speciic paths through
the nodes of these multi-terminal systems, which could result in complex
integrated nanoelectronic circuits. The 3D architectures revealed their
ability to support extremely high unidirectional stress when their mechanical
properties were tested. These networks performed better than standard
carbon aerogels because of their low mass densities, continuous porosities
and high surface areas.
Despite several patterning methods available for the fabrication of
nano-ensembles on various substrates, researchers working in Terrones'
laboratories have decided to explore low-cost and scalable routes that
avoid the use of complicated lithographic approaches. To that purpose,
they reported the growth of aligned MWCNTs-CNx presenting fascinating
structures such as cactus, lower, volcano, and cake. 165 These architectures
were obtained by pyrolyzing ferrocene/toluene/benzylamine solutions
at 850 ° C over electrochemically HF-etched Si substrates. By changing the
current densities, it was possible to control the formation and morphology of
the circular patterns exhibiting different SiO x distributions.

9.2.6.4 Incorporaon of CNTs with different species

Researchers at Terrones' laboratory demonstrated that molybdenum (Mo) has
the ability to self-assemble into nanowires once restrained in a limited space
like the interior of CNTs. 166 In such a situation, it tends to form nanowires that
consist of a subunit of a Mo body-centred cubic crystal rather than assuming
a linear chain conformation. 167 Quantum mechanical calculations have also
demonstrated that tubes need to have a diameter ≥ 0.7 nm to accommodate
the smallest of such wires and thus to make this phenomenon happen.
On the other hand, when lithium and ammonia are intercalated inside
MWCNTs, the tubes could be opened longitudinally by exfoliation, especially
when acid treatment and abrupt heating are applied. 168 In this way, the
authors were able to obtain several structures, consisting of (i) multilayered
lat graphitic structures (nanoribbons), (ii) partially open MWCNTs and (iii)
graphene lakes. On the whole, the completely unwrapped nanotubes were
called “ex-MWCNTs”, the utility of which should be deeply investigated.
The authors also reported the synthesis and characterisation of selenium-
carbon (Se-C) nanocables, 169 which consisted of a SWCNT as core structure,
surrounded by a trigonal selenium shell made of selenium oxide. This