Biomedical Engineering Reference
In-Depth Information
Terrones' group is involved in theoretical and experimental research
of new materials, with the aim to understand and predict the mechanical,
electronic and magnetic properties of nanostructures, and to apply them to
novel technologies; the inal purpose is to obtain more compact tools and
better performance.
In more detail, the main research areas include computational materials
science, low dimensional systems, magnetism in new materials, nanoscience
and nanotechnology, superconductivity, electron microscopy and optical
properties.
9.2.6.1. Doping of CNTs
Terrones' group is specialised on CNTs' “doping”, which consists in the
incorporation of electron acceptors or electron donor species such as
nitrogen (N), boron (B) and phosphorus (P) (
Fig. 9.24)
.
This process enables
the modulation of the tubes' physical, chemical and electronic properties
for a better characterisation of the samples and for potential applications
in chemical sensors. In particular, it seems that chemical attributes of BN-
doped tubes are very important for the production of reinforced composites
with insulating characteristics.
148
From the theoretical point of view, it has
emerged that (BN)-C-hetero-nanotubes could have important implications
for advanced nanoelectronics. Recent articles reporting data obtained from
energy-dispersive X-ray analysis (EDX) and electron energy loss spectroscopy
(EELS) have shown that P and N can be homogeneously incorporated into
the lattice of MWCNTs (with diameters usually above 20 nm).
149
In that case,
MWCNTs doped with phosphorus (P) and nitrogen (N) could be synthesised
using a solution of ferrocene (Fe(C
5
H
5
)
2
), triphenylphosphine (P(C
6
H
5
)
3
)
and benzylamine (C
6
H
5
CH
2
NH
2
) in conjunction with spray pyrolysis. Iron
phosphide (Fe
3
P) nanoparticles acted as catalysts during nanotube growth,
leading to the formation of novel heterodoped PN-MWCNTs. Differently from P,
the doping of CNTs with N has been already highly documented and subjected
to intense debates regarding its role in the formation of unique structural
features, including shortened tubes, smaller diameters and even bamboo-like
multilayered nanotubules.
150
Both theoretical and experimental techniques
have concluded that N acts as a surfactant during growth, favouring the
formation of tubes with reduced diameters. Additionally, it could also induce
tube closure, which implies a relatively large amount of N atoms into the tube
lattice, leading to bamboo-like structures.
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