Figure 21c shows the LCM PL spectra of the P3BT and PEDOT sections of the
same single LECB-NW. The LCM PL peaks for the P3BT and PEDOT sections of
the same single NW were detected at ~626 nm (i.e., orange–yellow light emission)
and 554 nm (i.e., green light emission), respectively. The LCM PL peak intensity
and integrated area of the sections of the P3BT NW were approximately nine times
higher than those of the PEDOT NW.
Enhanced luminescence efficiency can be expected for polymer-based lightemitting NWs with a nanoscale metal coating, because of energy transfer via SPR
coupling [64, 103]. Figure 21d shows a schematic illustration of an LECB-NW comprising nanoscale Cu metal-coated P3BT-PEDOT (denoted as P3BT-PEDOT/Cu).
The formation of the hybrid P3BT-PEDOT/Cu LECB-NWs was confirmed through
HR-TEM experiments, as shown in Fig. 21e. From the magnified HR-TEM image,
the total diameter of the single P3BTPEDOT/Cu LECB-NW and thickness of the
outside Cu NT were found to be ~200 and ~10 nm, respectively. The fine and
periodic patterns of the outer tube are attributed to the crystalline structure of the Cu
material, as shown in the inset of Fig. 21e.
Figure 21f compares the 3D LCM PL images of isolated single P3BT-PEDOT
and P3BT-PEDOT/Cu LECB-NWs under the same LCM experimental conditions.
The measured voltages of the LCM PL intensities of the hybrid P3BT/Cu and
PEDOT/Cu sections were 1.8À2.0 V and 26À30 mV, whereas those of the P3BT
and PEDOT sections without the Cu coating were 140À180 and 22À25 mV,
respectively. The measured voltages of the LCM PL intensities for the hybrid
P3BT/Cu sections were approximately 10À14 times higher than those of the
P3BT sections. The surface plasmon energy (~2.1 eV or 585 nm) of the nanoscale
Cu closely matched the emissive photon energy of the P3BT materials. Thus, SPR
coupling occurred, which induced energy transfer between the nanoscale Cu and
P3BT materials [103]. This explains the considerable enhancement in the PL
efficiency for the hybrid P3BT/Cu sections.
Figure 21g shows color CCD images of single P3BT-PEDOT/Cu LECB-NW in
the fresh state and after aging by exposure to the atmosphere for 2 months. Green
light emission was observed from the PEDOT/Cu sections of the aged LECB-NWs,
whereas orange–yellow light emission was dominant for the P3BT/Cu sections of
the fresh LECB-NWs. These results imply that the Cu metal-coated P3BT-PEDOT
LECB-NWs are promising optical barcode NWs because of their highly sensitive
light emission and long-term stability for identification. These results were confirmed by measurements of the LCM PL spectra, as shown in Fig. 21h. The LCM
PL peak positions and intensities of the aged samples were found to be comparable
with those of the fresh samples because of the protection from oxidation given by
the nanoscale Cu coating.
LECB-NWs consisting of three different light-emitting polymers (P3MT, P3BT,
and PEDOT) coated with nanoscale Cu were fabricated. Red, orange–yellow, and
green luminescence were observed corresponding to the P3MT/Cu, P3BT/Cu, and
PEDOT/Cu sections of the same LECB-NW, respectively, as shown in the
top image of Fig. 22a. In the color CCD image for the mixture of two different
LECB-NWs, the three luminescence colors (red, orange–yellow, and green) of the
Synthesis, Characteristics, and Applications of Intrinsically Light-Emitting. . .
229
same single LECB-NW. The LCM PL peaks for the P3BT and PEDOT sections of
the same single NW were detected at ~626 nm (i.e., orange–yellow light emission)
and 554 nm (i.e., green light emission), respectively. The LCM PL peak intensity
and integrated area of the sections of the P3BT NW were approximately nine times
higher than those of the PEDOT NW.
Enhanced luminescence efficiency can be expected for polymer-based lightemitting NWs with a nanoscale metal coating, because of energy transfer via SPR
coupling [64, 103]. Figure 21d shows a schematic illustration of an LECB-NW comprising nanoscale Cu metal-coated P3BT-PEDOT (denoted as P3BT-PEDOT/Cu).
The formation of the hybrid P3BT-PEDOT/Cu LECB-NWs was confirmed through
HR-TEM experiments, as shown in Fig. 21e. From the magnified HR-TEM image,
the total diameter of the single P3BTPEDOT/Cu LECB-NW and thickness of the
outside Cu NT were found to be ~200 and ~10 nm, respectively. The fine and
periodic patterns of the outer tube are attributed to the crystalline structure of the Cu
material, as shown in the inset of Fig. 21e.
Figure 21f compares the 3D LCM PL images of isolated single P3BT-PEDOT
and P3BT-PEDOT/Cu LECB-NWs under the same LCM experimental conditions.
The measured voltages of the LCM PL intensities of the hybrid P3BT/Cu and
PEDOT/Cu sections were 1.8À2.0 V and 26À30 mV, whereas those of the P3BT
and PEDOT sections without the Cu coating were 140À180 and 22À25 mV,
respectively. The measured voltages of the LCM PL intensities for the hybrid
P3BT/Cu sections were approximately 10À14 times higher than those of the
P3BT sections. The surface plasmon energy (~2.1 eV or 585 nm) of the nanoscale
Cu closely matched the emissive photon energy of the P3BT materials. Thus, SPR
coupling occurred, which induced energy transfer between the nanoscale Cu and
P3BT materials [103]. This explains the considerable enhancement in the PL
efficiency for the hybrid P3BT/Cu sections.
Figure 21g shows color CCD images of single P3BT-PEDOT/Cu LECB-NW in
the fresh state and after aging by exposure to the atmosphere for 2 months. Green
light emission was observed from the PEDOT/Cu sections of the aged LECB-NWs,
whereas orange–yellow light emission was dominant for the P3BT/Cu sections of
the fresh LECB-NWs. These results imply that the Cu metal-coated P3BT-PEDOT
LECB-NWs are promising optical barcode NWs because of their highly sensitive
light emission and long-term stability for identification. These results were confirmed by measurements of the LCM PL spectra, as shown in Fig. 21h. The LCM
PL peak positions and intensities of the aged samples were found to be comparable
with those of the fresh samples because of the protection from oxidation given by
the nanoscale Cu coating.
LECB-NWs consisting of three different light-emitting polymers (P3MT, P3BT,
and PEDOT) coated with nanoscale Cu were fabricated. Red, orange–yellow, and
green luminescence were observed corresponding to the P3MT/Cu, P3BT/Cu, and
PEDOT/Cu sections of the same LECB-NW, respectively, as shown in the
top image of Fig. 22a. In the color CCD image for the mixture of two different
LECB-NWs, the three luminescence colors (red, orange–yellow, and green) of the
Synthesis, Characteristics, and Applications of Intrinsically Light-Emitting. . .
229