wave, resulting in collective in-plane oscillations [101]. When the dimensions of
metal nanostructures, such as the thickness of an NT and diameter of an NP are
scaled down to levels comparable to the skin depth, the incident electromagnetic
energy is effectively absorbed by light-emitting polymers. Furthermore, SPR
coupling in hybrid nanostructures occurs if the surface plasmon absorption energy
of the metal matches the photon energy of the light-emitting polymer, which leads
to drastic variations in the optical properties of the hybrid nanostructures [6, 64, 65].
4.4.1 Hybrid Double-Layered Nanowires and Nanotubes
The variation in luminescence efficiency and color of hybrid double-layered (HDL)
NWs or NTs that were fabricated by coating the surface of light-emitting polymer
NWs or NTs with a nanoscale film of metal was reported [103, 104]. Figure 18a–c
shows the SEM and TEM images of pristine and HDL-NWs of P3BT/Ni and P3BT/
Cu [103]. The formation of two clear layers was observed: the inside and outside
layers of the HDL-NWs were P3BT and the metal (Ni or Cu), respectively. The
TEM image of an isolated single HDL-NW shows that the total diameter of the
hybrid P3BT/Cu NW and the thickness of the external Cu NT were ~200 and
~10 nm, respectively, as shown in Fig. 18b. The high-resolution (HR) TEM image
shows the fine and periodic stripe patterns of the outer metal NT, which match the
crystalline structure of Cu (lattice spacing ffi 0.21 nm). As shown in the inset of
Fig. 18c, the crystalline spots in the selected area electron diffraction (SAED)
pattern of the P3BT/Cu HDL-NWs support the conclusion that the outer Cu NT
has a crystalline structure in accordance with the HR-TEM results.
Figure 18d, e shows luminescent color CCD and 3D LCM PL images of an
isolated single P3BT NW and HDL-NWs of P3BT/Ni and P3BT/Cu. Weak green
light emission was observed for the P3BT single NW owing to the lightly doped
states, whereas both HDL-NWs (P3BT/Ni and P3BT/Cu) showed bright
orange–red light emission, as shown in Fig. 18d. The intensity in the 3D LCM PL
image of the P3BT single NW was measured at 22À28 mV. For single HDL-NWs
made of P3BT/Ni or P3BT/Cu, the measured voltages of the LCM PL intensities
were 1.8À2.3 and 1.5À2.0 V, respectively. The application of the nanoscale Ni or
Cu metal coating on the outside of the P3BT NWs led to a 60- to 110-fold increase
in the measured voltages of the 3D LCM PL intensities compared with that of the
P3BT single NW. Similar results for the HDL-NTs of PTh/metals were reported
earlier [64]. Figure 18f shows the averaged LCM PL spectra of corresponding
samples. The main LCM PL peak for a single P3BT NW was observed at ~544 nm,
corresponding to green light emission. With the nanoscale metal coating, the main
LCM PL peaks of the HDL-NWs of P3BT/Ni and P3BT/Cu were red-shifted to
~635 and ~639 nm, respectively, in the range of orange–red light emission. The
peak intensity and integrated area of LCM PL spectra significantly increased up to
about 80À90 times after hybridization with nanoscale metals [61, 68].
The PL enhancement and color variation of the HDL-NWs are attributed to the
energy and charge-transfer effects in SPR coupling. The inset on the right in Fig. 18f
Synthesis, Characteristics, and Applications of Intrinsically Light-Emitting. . .
223
metal nanostructures, such as the thickness of an NT and diameter of an NP are
scaled down to levels comparable to the skin depth, the incident electromagnetic
energy is effectively absorbed by light-emitting polymers. Furthermore, SPR
coupling in hybrid nanostructures occurs if the surface plasmon absorption energy
of the metal matches the photon energy of the light-emitting polymer, which leads
to drastic variations in the optical properties of the hybrid nanostructures [6, 64, 65].
4.4.1 Hybrid Double-Layered Nanowires and Nanotubes
The variation in luminescence efficiency and color of hybrid double-layered (HDL)
NWs or NTs that were fabricated by coating the surface of light-emitting polymer
NWs or NTs with a nanoscale film of metal was reported [103, 104]. Figure 18a–c
shows the SEM and TEM images of pristine and HDL-NWs of P3BT/Ni and P3BT/
Cu [103]. The formation of two clear layers was observed: the inside and outside
layers of the HDL-NWs were P3BT and the metal (Ni or Cu), respectively. The
TEM image of an isolated single HDL-NW shows that the total diameter of the
hybrid P3BT/Cu NW and the thickness of the external Cu NT were ~200 and
~10 nm, respectively, as shown in Fig. 18b. The high-resolution (HR) TEM image
shows the fine and periodic stripe patterns of the outer metal NT, which match the
crystalline structure of Cu (lattice spacing ffi 0.21 nm). As shown in the inset of
Fig. 18c, the crystalline spots in the selected area electron diffraction (SAED)
pattern of the P3BT/Cu HDL-NWs support the conclusion that the outer Cu NT
has a crystalline structure in accordance with the HR-TEM results.
Figure 18d, e shows luminescent color CCD and 3D LCM PL images of an
isolated single P3BT NW and HDL-NWs of P3BT/Ni and P3BT/Cu. Weak green
light emission was observed for the P3BT single NW owing to the lightly doped
states, whereas both HDL-NWs (P3BT/Ni and P3BT/Cu) showed bright
orange–red light emission, as shown in Fig. 18d. The intensity in the 3D LCM PL
image of the P3BT single NW was measured at 22À28 mV. For single HDL-NWs
made of P3BT/Ni or P3BT/Cu, the measured voltages of the LCM PL intensities
were 1.8À2.3 and 1.5À2.0 V, respectively. The application of the nanoscale Ni or
Cu metal coating on the outside of the P3BT NWs led to a 60- to 110-fold increase
in the measured voltages of the 3D LCM PL intensities compared with that of the
P3BT single NW. Similar results for the HDL-NTs of PTh/metals were reported
earlier [64]. Figure 18f shows the averaged LCM PL spectra of corresponding
samples. The main LCM PL peak for a single P3BT NW was observed at ~544 nm,
corresponding to green light emission. With the nanoscale metal coating, the main
LCM PL peaks of the HDL-NWs of P3BT/Ni and P3BT/Cu were red-shifted to
~635 and ~639 nm, respectively, in the range of orange–red light emission. The
peak intensity and integrated area of LCM PL spectra significantly increased up to
about 80À90 times after hybridization with nanoscale metals [61, 68].
The PL enhancement and color variation of the HDL-NWs are attributed to the
energy and charge-transfer effects in SPR coupling. The inset on the right in Fig. 18f
Synthesis, Characteristics, and Applications of Intrinsically Light-Emitting. . .
223