Communications
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2
their alignment under relatively low magnetic fields, which
emphasizes their potential for further manipulation and
assembly, for example in nanoreinforced fiber materials.
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[
Experimental Section
CNT polyelectrolyte functionalization: CNTs were dispersed in ultra
[
3,4]
pure water (18 MWcm) following a published procedure.
Briefly,
CNTs were dispersed in a 1 wt.% aqueous solution of polyallylamine
À1
hydrochloride (PAH) to a concentration of 150 mgL . A combina-
tion of rapid stirring and sonication was used to ensure the presence
of well dispersed, individual nanotubes. Excess PAH was removed by
several centrifugation and redispersion cycles.
Platinum seeds: The Pt nanoparticles to be deposited onto CNTs
were synthesized as follows. Sodium borohydride (2.9 mL, 0.06m) was
added as a reducing agent to a solution of sodium citrate (2.5 mL,
0
.1m) and K PtCl (0.5 mL, 0.05m) in ultrapure water (44 mL) and the
2 4
resulting solution stirred for 10 min.
Pt deposition on the CNT surface: CNT@PAH (0.6 mL,
À1
0
.5 mgmL ) was added to a solution of Pt seeds (50 mL, 0.5 mm).
After allowing to stand for 30 min, the solution was centrifuged
10 min, 8000 rpm) and redispersed in pure water (20 mL) to remove
(
nondeposited nanoparticles.
Ni growth: The CNT/Pt dispersion (20 mL) was added to an
aqueous solution (30 mL) containing an NiCl2 stocksolution
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(
0.06 mL, 0.25m) and hydrazine (0.12 mL, 2.5m). The mixture was
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magnet and washed with water and ethanol (twice for each solvent).
2002, 106, 1869; b) K.-W. Park, J.-H. Choi, Y.-E. Sun, J. Phys.
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Received: April 16, 2007
[
[
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Keywords: magnetic properties · materials science · nanotubes ·
.
nickel · platinum
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