C O M M U N I C A T I O N S
voltage, Rtip is the tip radius of curvature, and R is a modifying
factor. From the above equations, we got
I
1
V
ln
) (-6.8 × 107RRtipφ3/2) + offset
2
( )
V
RRtipφ3/2 can be estimated from the slope of the F-N plot of
ln(I/V2) against (1/V), as depicted in the inset in Figure 3. A plot
of ln(I/V2) versus 1/V yields a straight line, indicating that the field
emission process from the nanowire film is a quantum tunneling
process. Taking R ) 10 (as used in another report12) and Rtip ) 35
nm, in our case, the evaluated work function of the polyCYDIOL
nanowires is around 3.05 eV. This work function is much smaller
than that of graphite, which is typically around 4.34 eV, demon-
strating that the polydiacetylene nanowires have great potential as
a competitive candidate for field emitters.
Figure 2. TEM of (A) polyCYDIOL nanowires; (B) a single polyCYDIOL
nanowire with striation constructions.
In summary, we have shown that the associated self-polymeri-
zation and self-assembly induces production of polydiacetylene
nanowires, which provides a facile and effective method for
fabricating stable low-dimensional nanostructures. The resulting
nanowires show excellent field emission properties, which exhibit
that the turn-on field of the PDA nanowires is 8.2 V/µm at 10 µA/
cm2 and the maximum current density is larger than 5 mA/cm2 at
an applied field of 15 V/µm. This work presents a new concept to
fabricate conducting polymer nanowires, and it may have great
potential for further applications on fabricating supramolecular
materials-based conducting polymer for various fields, such as
sensors, optical materials, nanotips in field emission devices, etc.
Figure 3. Field emission J-E curves of the polyCYDIOL nanowires. The
inset shows the Fowler-Nordheim plot.
the concentration of CYDIOL on the copper foil surface increases,
which causes the increase of the noncovalent forces, including
interaction of π-stacking and H-bonding. Coordinated with the
polymerization process, a balance between self-assembly and
polymerization helped the formation of ordered polymer nanowires.
Further characterization of the nanowires was performed by
TEM. Figure 2A shows some PDA nanowires with a width from
110 to 150 nm. Figure 2B shows a higher magnification view of a
single PDA nanowire with the diameter of about 140 nm, which
shows striation construction. This is coincident with our self-
assembly mechanism.
Acknowledgment. This work was supported by Major State
Basic Research Development Program and the National Nature
Science Foundation of China (20131040, 20418001, 20473102,
20421101, and 50372070).
Supporting Information Available: The detailed Experimental
section, FT-IR and Raman spectra of the PDA, 1H NMR spectroscopy
studies of the self-assembly, probable self-assembly scheme and the
SEM images of PDA at different self-assembly conditions, and the
relevant ester are available. This material is available free of charge
In the construction of supramolecular systems, H-bonding and
π-stacking often play a prominent role. This has also been proven
by others’ works. Ajayaghosh has recently reported H-bonding of
benzalcohol and the π-stacking of OPV skeleton-induced supramo-
lecular assembly of OPV derivatives.11 Olesik has reported π-stack-
ing-induced cross-linking of poly(1,8-dihydroxymethyl-1,3,5,7-
octatetrayne) to form polymer nanospheres.9 Suck-Hyun Lee has
reported the polydiacetylene supramolecular assembly induced by
H-bonds between aromatic dicarboxylic acids and π-stacking of
diacetylene moieties.10 On our side, we suggest that the CYDIOL
molecules possess the capability for forming low-dimensional
nanostructures by the associated effect of self-polymerization and
self-assembly.
The field emission characteristics are presented in Figure 3 by
the curve of current density J versus applied field E. The turn-on
field of the PDA nanowires was 8.2 V/µm at 10 µA/cm2 and the
maximum current density is larger than 5 mA/cm2 at an applied
field of 15 V/µm. The emission characteristics were analyzed using
the Fowler-Nordheim model described as11
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