The LCM PL peak of the PEDOT single NW was blue-shifted after doping. The PL
peaks of pristine PTh and P3HT film samples are usually observed at 610 and 640 nm
(i.e., orange–red light emission), respectively [84]. The LCM PL peak intensity of the
single de-doped PEDOT NW increased up to a maximum of approximately threefold
as compared with that of the doped PEDOT NW, as shown in Fig. 15b.
Figure 15c shows 3D LCM PL images of isolated single doped and de-doped
PEDOT NWs. The PL image of the single de-doped PEDOT NW is brighter than
that of the doped PEDOT NW. The measured voltages of the PL intensity for the
doped and de-doped PEDOT single NWs were 60À90 and 180À260 mV, respectively. The PL intensity of the de-doped PEDOT single NW was two to three times
higher than that of the doped PEDOT NW because of the reduction in PL quenching
through the dedoping process.
4.2 Unfocused E-Beam Treatment
Hong et al. reported the dedoping and conformational effects of unfocused E-beam
treatment of NTs and NWs of light-emitting and conducting polymers [67, 86, 87].
Compared with the conventional solution-based techniques for the control of doping
level, such as chemical doping [31–33] or electrochemical redox by CV [79, 80],
E-beam treatment enables control of the optical properties of light-emitting polymer
nanostructures in a quantitative manner through adjustment of the E-beam parameters
such as dosage and/or energy. This approach has the advantages of a relatively simple
procedure and reduced of contamination by solvents.
An unfocused E-beam from a linear electron accelerator was directed onto P3MT
NTs along the length direction. The energy of the E-beam was fixed at 1 MeV, and
the dosage of the E-beam was varied in the range from 1.6 Â 10
13 to
8.0 Â 10
16 electrons/cm
2
. The treatment was performed in air at atmospheric pressure and room temperature. The heating effect produced by the E-beam was
compensated for by air cooling [67]. Figure 16a shows the normalized UV–vis
absorption spectra of P3MT NTs in the pristine state (i.e., before E-beam treatment)
and after treatment with an unfocused E-beam of different dosages. For the pristine
P3MT NTs, a broad and relatively strong bipolaron peak and relatively weak π–π*
transition peak were observed at ~800 and 400 nm, respectively, which indicate
highly doped states. As the dose of the E-beam irradiation was increased from
1.6 Â 10
13 to 8.0 Â 10
16 electrons/cm
2
, the doping-induced bipolaron peak considerably decreased and the π–π* transition peak was shifted from 400 to ~550 nm. It is
known that there exist two helical configurations for the polymeric chain in P3MT,
namely, the coil-like and rod-like configurations, which correspond to the peaks at
400 and ~550 nm in the UV–vis absorption spectra, respectively [88–90]. From
Fig. 16a, it is seen that rod-like configurations with π–π* transition peaks at
~550 nm were observed after E-beam treatment with a dose of 4.8 Â 10
16 to
8.0 Â 10
16 electrons/cm
2
. The π–π* transition peaks of the electrochemically
de-doped P3MT NTs were not very far from their original positions [65].
Synthesis, Characteristics, and Applications of Intrinsically Light-Emitting. . .
219
peaks of pristine PTh and P3HT film samples are usually observed at 610 and 640 nm
(i.e., orange–red light emission), respectively [84]. The LCM PL peak intensity of the
single de-doped PEDOT NW increased up to a maximum of approximately threefold
as compared with that of the doped PEDOT NW, as shown in Fig. 15b.
Figure 15c shows 3D LCM PL images of isolated single doped and de-doped
PEDOT NWs. The PL image of the single de-doped PEDOT NW is brighter than
that of the doped PEDOT NW. The measured voltages of the PL intensity for the
doped and de-doped PEDOT single NWs were 60À90 and 180À260 mV, respectively. The PL intensity of the de-doped PEDOT single NW was two to three times
higher than that of the doped PEDOT NW because of the reduction in PL quenching
through the dedoping process.
4.2 Unfocused E-Beam Treatment
Hong et al. reported the dedoping and conformational effects of unfocused E-beam
treatment of NTs and NWs of light-emitting and conducting polymers [67, 86, 87].
Compared with the conventional solution-based techniques for the control of doping
level, such as chemical doping [31–33] or electrochemical redox by CV [79, 80],
E-beam treatment enables control of the optical properties of light-emitting polymer
nanostructures in a quantitative manner through adjustment of the E-beam parameters
such as dosage and/or energy. This approach has the advantages of a relatively simple
procedure and reduced of contamination by solvents.
An unfocused E-beam from a linear electron accelerator was directed onto P3MT
NTs along the length direction. The energy of the E-beam was fixed at 1 MeV, and
the dosage of the E-beam was varied in the range from 1.6 Â 10
13 to
8.0 Â 10
16 electrons/cm
2
. The treatment was performed in air at atmospheric pressure and room temperature. The heating effect produced by the E-beam was
compensated for by air cooling [67]. Figure 16a shows the normalized UV–vis
absorption spectra of P3MT NTs in the pristine state (i.e., before E-beam treatment)
and after treatment with an unfocused E-beam of different dosages. For the pristine
P3MT NTs, a broad and relatively strong bipolaron peak and relatively weak π–π*
transition peak were observed at ~800 and 400 nm, respectively, which indicate
highly doped states. As the dose of the E-beam irradiation was increased from
1.6 Â 10
13 to 8.0 Â 10
16 electrons/cm
2
, the doping-induced bipolaron peak considerably decreased and the π–π* transition peak was shifted from 400 to ~550 nm. It is
known that there exist two helical configurations for the polymeric chain in P3MT,
namely, the coil-like and rod-like configurations, which correspond to the peaks at
400 and ~550 nm in the UV–vis absorption spectra, respectively [88–90]. From
Fig. 16a, it is seen that rod-like configurations with π–π* transition peaks at
~550 nm were observed after E-beam treatment with a dose of 4.8 Â 10
16 to
8.0 Â 10
16 electrons/cm
2
. The π–π* transition peaks of the electrochemically
de-doped P3MT NTs were not very far from their original positions [65].
Synthesis, Characteristics, and Applications of Intrinsically Light-Emitting. . .
219