Biomedical Engineering Reference
In-Depth Information
[173-182]. Basically, 1D conducting polymer nanostructures
can also be synthesized chemically or electrochemically by using
“hard” and “soft” template methods. Obviously, the hard-template
method (e.g., AAO) is an effective and straightforward route for
fabricating conducting polymer nanostructures with diameters
determined by the diameter of the pores in the template. Controlled
conducting PANI nanotubes and nanofibers have been fabricated
in the AAO templates and find promising applications in lithium/
PANI rechargeable batteries [183]. Nanotubes and nanowires
of conducting polymers, including PANI, polypyrrole (PPy), and
poly(3,4-ethylenedioxythiophene) (PEDOT), can be synthesized
by electrochemical methods using the AAO templates [184].
By changing the doping level, dopant, and template-dissolving
solvents, the electrical and optical properties of the nanotubes
and nanowires can be controlled. The diameters of the conducting
polymer nanotubes and nanowires are in the range 100-200 nm,
depending on the diameter of the nanoporous template used. It
was found that the polymerization was initiated from the wall-
side of the AAO template. The synthesized nanotubes have an open
end at the top with the filled end at the bottom. As polymerization
time increases, the nanotubes will be filled and nanowires will be
formed with the length increased. For example, PPy nanotube can
be synthesized by applying current of 2-3 mA for 1 min. When the
time is increased to 15-40 min, PPy nanowires will be produced.
Conducting polymer nanotube and nanowires prepared by this
electrochemical method using AAO templates can be applied in field
emitting applications [185,186]. Figure 1.
16
shows a uniform layer
of polyaniline nanowires produced at constant potential at 1.0 V for
10 min through the AAO template [187].
PPy nanotubes and nanowires can be also electrochemically
synthesized through nanoporous AAO template in ionic liquids
[188]. The electrolyte consisted of pyrrole monomer, solvent, and
room temperature ionic liquid dopant such as 1-butyl-3-methyl
imidazolium tetrafluoroborate ([BMIM][BF
])
and
1-butyl-3-
4
]), which
is stable in air and moisture. The length and diameter of PPy
nanotubes and nanowires were determined by the synthetic
conditions such as polymerization time, current, and dopant. The
methyl imidazolium hexafluorophosphate ([BMIM][PF
6
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