color CCD image. Comparison of the LCM PL spectra showed a PL enhancement
estimated at 220-fold, which shows good agreement with the results in the LCM PL
images.
Figure 20e shows the normalized UV–vis absorption spectra of the P3MT NTs
and hybrid P3MT-NT/Au-NPs. Typical absorption characteristics were observed
for the pristine P3MT NTs with doped states. For the hybrid P3MT-NT/Au-NPs, the
intensity of the doping-induced bipolaron peak was considerably decreased, and
two new absorption peaks were generated at 567 and 616 nm. These new peaks
were assigned to the electrical dipole and quadrupole contributions in the surface
plasmons, which resulted from the matching of the Fermi energy (E F ) levels
between the P3MT NT and the Au NPs.
Figure 20f shows the electric field distributions in hybrid polymer-NT/Au-NPs
according to simulation using the finite-difference time-domain (FDTD) method
[51]. By choosing experimental values as the simulation parameters [114], a strong
local electric field enhancement in the nanogaps between Au NPs was calculated
in the background of the light-emitting P3MT [115–117]. This local electric field
enhancement, represented by the red color parts in Fig. 20f and its inset, also
contributes to the PL enhancement of the hybrid P3MT-NT/Au-NPs. All the
results support the occurrence of energy and/or charge transfer attributed to the
SPR coupling effects in the hybrid nanostructures of light-emitting polymers and
metals.
5 Applications
In this section, various applications of light-emitting polymer nanostructures are
introduced. The application of low-dimensional heterojunction NWs to optoelectronics, photonics, and biotechnologies has received considerable attention
[118–124]. Inorganic material-based heterojunction NWs have been reported, and
their application to optically reflecting barcode NWs has been investigated
[118, 119, 125–130]. This section introduces novel organic-based heterojunction
NWs, light-emitting color barcode (LECB)-NWs, and quasi-superlattice NWs
made using light-emitting polymers. Solid-state and label-free DNA detection is
discussed in terms of PL characteristics. Finally, nano-optoelectronic applications
of light-emitting polymer nanostructures, such as rectifying, photo-switching, and
photovoltaic effects, are presented.
5.1 Barcodes
Conventional black and white barcodes have been used for the identification of
commercial products through optical reflection. For effective identification of
nanoscale products with complex physical shapes, the identification sensitivity,
Synthesis, Characteristics, and Applications of Intrinsically Light-Emitting. . .
227
estimated at 220-fold, which shows good agreement with the results in the LCM PL
images.
Figure 20e shows the normalized UV–vis absorption spectra of the P3MT NTs
and hybrid P3MT-NT/Au-NPs. Typical absorption characteristics were observed
for the pristine P3MT NTs with doped states. For the hybrid P3MT-NT/Au-NPs, the
intensity of the doping-induced bipolaron peak was considerably decreased, and
two new absorption peaks were generated at 567 and 616 nm. These new peaks
were assigned to the electrical dipole and quadrupole contributions in the surface
plasmons, which resulted from the matching of the Fermi energy (E F ) levels
between the P3MT NT and the Au NPs.
Figure 20f shows the electric field distributions in hybrid polymer-NT/Au-NPs
according to simulation using the finite-difference time-domain (FDTD) method
[51]. By choosing experimental values as the simulation parameters [114], a strong
local electric field enhancement in the nanogaps between Au NPs was calculated
in the background of the light-emitting P3MT [115–117]. This local electric field
enhancement, represented by the red color parts in Fig. 20f and its inset, also
contributes to the PL enhancement of the hybrid P3MT-NT/Au-NPs. All the
results support the occurrence of energy and/or charge transfer attributed to the
SPR coupling effects in the hybrid nanostructures of light-emitting polymers and
metals.
5 Applications
In this section, various applications of light-emitting polymer nanostructures are
introduced. The application of low-dimensional heterojunction NWs to optoelectronics, photonics, and biotechnologies has received considerable attention
[118–124]. Inorganic material-based heterojunction NWs have been reported, and
their application to optically reflecting barcode NWs has been investigated
[118, 119, 125–130]. This section introduces novel organic-based heterojunction
NWs, light-emitting color barcode (LECB)-NWs, and quasi-superlattice NWs
made using light-emitting polymers. Solid-state and label-free DNA detection is
discussed in terms of PL characteristics. Finally, nano-optoelectronic applications
of light-emitting polymer nanostructures, such as rectifying, photo-switching, and
photovoltaic effects, are presented.
5.1 Barcodes
Conventional black and white barcodes have been used for the identification of
commercial products through optical reflection. For effective identification of
nanoscale products with complex physical shapes, the identification sensitivity,
Synthesis, Characteristics, and Applications of Intrinsically Light-Emitting. . .
227