[
NiPc]I–silica nanocomposites were not measured because the
spectra were recorded on a Perkin Elmer Spectrum 1000
spectrometer using KBr plates. For conductivity measurements,
powdery samples were pressed into pellets under a pressure of
preparation of pellets was difficult, while they may be similar
to that of [CuPc]I–silica nanocomposites considering their
close similarities. Direct measurements of the conductivity
of the nanorods using a scanning probe microscope were
unsuccessful because of their extremely small size and
aggregated structures.
À2
500 kg cm by using a hydraulic molding press. Conductivity
was measured by the ac impedance technique at ambient
temperature with an applied voltage of 1 V using a Solartron
1260 impedance analyzer. XRD patterns were simulated using
Mercury CSD software (v. 2.3) available from Cambridge
Crystallographic Data Centre.
Conclusions
Preparation of [MPc]I–silica nanocomposites
MPc–silica hybrid nanoparticles fabricated via grinding
produced CT salts of [MPc]I through a direct reaction with
iodine. The composite powder was found to be structurally
interesting; the CT salt separated from the silica surface to
form rod-like nanostructures with diameters of about 30 nm.
The remarkably enhanced reactivity of MPc is notable, since
iodine doping of bulk MPc in the solid state does not occur
efficiently. The use of silica hybrid nanoparticles as presented
here is a simple, novel and highly productive method due to
the high reactivity of the surface molecules. The higher
reactivity enables more efficient processes than conventional
solid state reactions, and may even enable the use of poorly-
soluble compounds. In addition, while conventional
investigation of CT salts has focused predominately on single
crystals or films, access to nanosized composite materials
expands the scope and applications of these complexes.
For example, their nanosize may lead to unusual physical
properties, while the high dispersibility of nanosized materials
MPc–silica composite nanoparticles were fabricated according
1
0
to the method reported in the literature. Silica nanoparticles
(100 mg) and a desired amount of MPc were placed in zirconia
vessels (12 mL) and milled with the aid of nylon beads in a
Fritsch P-7 planetary mill at 400 rpm for 1 h. The obtained
composite nanoparticles and an equimolar amount of iodine
were then milled, also with the aid of nylon beads. The
resulting powders were washed with hexane (2 mL) and
the supernatant was removed with the aid of a centrifuge.
The washing was repeated three times, and the powders were
dried in vacuo at room temperature. Alternatively, the reaction
with iodine was carried out under wet conditions as follows.
To MPc–silica composite nanoparticles dispersed in a hexane
solution was dissolved an equimolar amount of iodine, and the
resulting dispersion stirred for 3 h. The supernatant was
separated with aid of a centrifuge, and the resulting powders
washed in a manner similar to the procedure stated above and
then dried in vacuo at room temperature.
1
8
in liquids is advantageous for various applications.
Furthermore, the efficiency as well as the simplicity of the
present method is of merit for large scale production of
functional nanomaterials. Exploration of the functionalities
and nanostructures of various molecular complexes prepared
with the present method is therefore of further interest.
Acknowledgements
We thank Prof. D. Kuwahara (The University of Electro-
communications) for his help with the instrumental analyses
and Prof. T. Uchino (Kobe University) for his support
throughout this work.
Experimental
Materials
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