metals, which allows drastic variations in the optical properties by exploiting
the surface plasmon resonance (SPR) coupling effect between the light-emitting
polymer and the nanoscale metal.
4.1 Electrochemical Doping and Dedoping: Cyclic Voltammetry
Electrochemical reduction and oxidation (redox) using CV is widely used to control
the doping characteristics of π-conjugated polymers and their nanostructures
[77–80]. Doping of π-conjugated polymers induces changes in structure and electronic state owing to intercalation of dopants between the polymeric chains. These
structural modifications induce variations in the π-conjugation length, polymeric
chain alignment, and intra-/interchain interactions, which in turn directly influence
the light absorption and emission properties.
Park et al. reported that additional doping and dedoping of the as-prepared
P3MT NTs and PEDOT NWs can be accomplished through electrochemical means
by controlling the applied potentials and scan rates using CV in a mixture of an
ionic liquid and a CH 3 CN solution without monomers [43, 65]. It is noted that
1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF 6 ) is an environmentally stable and recyclable ionic liquid that has shown negligible loss of electroactivity
when used as a dopant [77].
4.1.1 P3MT Nanotubes
Figure 14a shows the normalized UV–vis absorption spectra of P3MT NTs at
different doping levels. The π–π* transition peaks were observed at ~385 nm for all
the P3MT NTs. Broad bipolaron peaks due to doping were observed near
750À800 nm [81]. The relative intensity ratio of the bipolaron peak to the π–π*
transition peak for the doped-P3MT NTs was estimated to be 0.67, 0.52, 0.25, and
0.04, depending on the degree of additional doping or dedoping. The relative
integrated area ratio of the bipolaron peak to the π–π* transition peak was 0.67,
0.54, 0.22, and 0.01, respectively. On the basis of the UV–vis absorption spectra, the
various doped-P3MT NTs are denoted as doped-P3MT(0.04), doped-P3MT(0.25),
doped-P3MT(0.52), and doped-P3MT(0.67) NTs, where the number in brackets
represents the relative doping level. The relatively small ratios of intensity or area
of the bipolaron peaks compared with those of the π–π* transition peaks imply that
the P3MT NTs were lightly doped systems.
Figure 14b shows a comparison of the LCM PL spectra of a single P3MT NT
with various doping levels: doped-P3MT(0.04), doped-P3MT(0.25), doped-P3MT
(0.52), and doped-P3MT(0.67). The peak intensity and area of the LCM PL spectra
of these single strands gradually increased up to 14 times as the doping level
decreased. Two characteristic peaks in the LCM PL spectra for the P3MT materials
were observed at 640 and 685 nm.
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Y.K. Hong et al.
the surface plasmon resonance (SPR) coupling effect between the light-emitting
polymer and the nanoscale metal.
4.1 Electrochemical Doping and Dedoping: Cyclic Voltammetry
Electrochemical reduction and oxidation (redox) using CV is widely used to control
the doping characteristics of π-conjugated polymers and their nanostructures
[77–80]. Doping of π-conjugated polymers induces changes in structure and electronic state owing to intercalation of dopants between the polymeric chains. These
structural modifications induce variations in the π-conjugation length, polymeric
chain alignment, and intra-/interchain interactions, which in turn directly influence
the light absorption and emission properties.
Park et al. reported that additional doping and dedoping of the as-prepared
P3MT NTs and PEDOT NWs can be accomplished through electrochemical means
by controlling the applied potentials and scan rates using CV in a mixture of an
ionic liquid and a CH 3 CN solution without monomers [43, 65]. It is noted that
1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF 6 ) is an environmentally stable and recyclable ionic liquid that has shown negligible loss of electroactivity
when used as a dopant [77].
4.1.1 P3MT Nanotubes
Figure 14a shows the normalized UV–vis absorption spectra of P3MT NTs at
different doping levels. The π–π* transition peaks were observed at ~385 nm for all
the P3MT NTs. Broad bipolaron peaks due to doping were observed near
750À800 nm [81]. The relative intensity ratio of the bipolaron peak to the π–π*
transition peak for the doped-P3MT NTs was estimated to be 0.67, 0.52, 0.25, and
0.04, depending on the degree of additional doping or dedoping. The relative
integrated area ratio of the bipolaron peak to the π–π* transition peak was 0.67,
0.54, 0.22, and 0.01, respectively. On the basis of the UV–vis absorption spectra, the
various doped-P3MT NTs are denoted as doped-P3MT(0.04), doped-P3MT(0.25),
doped-P3MT(0.52), and doped-P3MT(0.67) NTs, where the number in brackets
represents the relative doping level. The relatively small ratios of intensity or area
of the bipolaron peaks compared with those of the π–π* transition peaks imply that
the P3MT NTs were lightly doped systems.
Figure 14b shows a comparison of the LCM PL spectra of a single P3MT NT
with various doping levels: doped-P3MT(0.04), doped-P3MT(0.25), doped-P3MT
(0.52), and doped-P3MT(0.67). The peak intensity and area of the LCM PL spectra
of these single strands gradually increased up to 14 times as the doping level
decreased. Two characteristic peaks in the LCM PL spectra for the P3MT materials
were observed at 640 and 685 nm.
216
Y.K. Hong et al.