Chemistry Reference
In-Depth Information
Figure 7.24
Molecular structure of the octadecyl-amide functionalised TTF deriva-
tive.
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(a) Graph showing the resistance-temperature dependence and
the conversion from a-phase to b-phase. (b) and (c) schematic illus-
trations of the proposed peeling process for a doped xerogel film. The
insets are AFM images of the control removal of material in a doped
xerogel sample.
116
(Reproduced with permission from Wiley-VCH.)
The room-temperature resistivity of the b-phase was less than that of the
a-phase by a factor of about 10 (Figure 7.24a). The phase transition from
a-phase to b-phase was proved by four-probe measurements and EPR char-
acterisation. Furthermore, current-sensing AFM studies of the doped b-phase
indicated an apparently Ohmic behaviour of the nanowires, and the EPR
linewidth indicated a metallic state in the material. We also described four
different conducting phases in total from the same doped xerogel sample after
different heat and/or doping treatments,
113
and demonstrated that the solvent
used to form these physical gels can play an important role in the conductivity
of related doped materials.
114,115
In a subsequent study, an unprecedented
controlled peeling of doped xerogel films of the octadecyl-amide TTF-based
gelator was also accomplished with the conducting probe of an AFM
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(Figures 7.22b and c). Remarkably, this study showed the importance of the
electric field in the stability of organic supramolecular conductive systems at the
nanoscale, an aspect that should be further considered in order to achieve
optimal organic-based functional devices from organogelators.
