Composite materials based on carbon nanotubes and poly o-phenylenediamine M. Baibarac*, I. Baltog, I. Smaranda, M.Scocioreanu, I. Gontia, T. Velula, L. Mihut

1
Composite materials based on carbon nanotubes and
poly o-phenylenediamine M. Baibarac, I. Baltog,
I. Smaranda, M.Scocioreanu, I. Gontia, T. Velula,
L. Mihut
Abstract
The chemical polymerization of o-phenylenediamine
(OPD) on single-walled carbon nanotubes (SWCNTs)
in the presence of phosphomolybdic acid
(H3PMo12O40 xH2O) has been studied by surface
enhanced resonant Raman scattering (SERRS)
spectroscopy. One demonstrates that an
organicinorganic hybrid composite of the type
poly(o-phenylenediamine)/polyoxometallate-function
alized SWCNTs is produced by the chemical
interaction between polyoxometallate-functionalize
d SWCNTs and poly(ophenylenediamine) (POPD) doped
with H2PMo12O40 ions. According to TEM
investigations, a result of the chemical
interaction of SWCNT with H3PMo12O40 xH2O is the
formation into the composite mass of tube
fragments of shorter length, which behave like
closed shell fullerenes since and for these the
Raman fingerprint is given by lines situated at
240275 and 14501472 cm-1. The chemical
polymerization of OPD on SWCNTs achieved in the
absence of H3PMo12O40 xH2O leads to a covalent
functionalization of the wall side of the tubes,
which is revealed in Raman spectra at the
excitation wavelength of 514 nm by an
enhancement of the lines associated with the
tangential vibrational modes of SWCNTs. Using
FTIR spectroscopy, significant hindrance steric
effects are evidenced in the POPD/polyoxometalla
te- functionalized SWCNT composite.
Fig.3.FTIR spectra of SWCNTSs (curve
1a), H3PMo12O40xH2O(curve3a),polyoxometallate- fun
ctionalized SWCNTs (curve 2a) and the
polyoxometallate-functionalized SWCNTs sample
interacted with a 1 M NH4OH solution (4a).
Experimental
Fig. 4. SERS spectra recorded at ?exc 514 nm
of the SWCNTs in their initial state (a1,a2),
POPD covalently functionalized SWCNTs (b1,b2)
and POPD (c1).
? The chemical interaction of SWCNTs with
H3PMo12O40 xH2O was studied using the mixture of
the two constituents in the weight ratios of
0.1/5 and 0.01/5. After the interaction of the
two constituents, a washing with water was
carried out to eliminate un-reacted H3PMo12O40.
The final product obtained by a drying until
constant mass corresponds to SWCNTs doped with
anions of H3PMo12O40. Solutions of SWCNTs doped
with anions of H3PMo12O40 in CH3CN of 0.1
concentration were used to prepare films
deposited on the rough Au support to be studied
by SERS spectroscopy. The chemical synthesis of
the hybrid material POPD/polyoxometallate-function
alized SWCNTs was carried out by direct addition
of 1 g OPD to 5 g H3PMo12O40 0.1 g SWCNT or 5 g
H3PMo12O40 0.01 g SWCNTs.In the absence of
H3PMo12O40, the chemical polymerization of OPD
was carried out according to the method was
reported ,which involves the use of 0.09 g OPD
dissolved in 20 ml of water and 2.34 ml of 0.71 M
ferric chloride. To obtain the POPD/ SWNTs
composites. Finally, both POPD and the
POPD/SWCNTs composites were washed several times
with water and dried in vacuum at 50oC for 24 h.
For SERS studies were used films deposited onto
rough Au supports . They were obtained from were
obtained by the evaporation of the solvent using
solutions of POPD and POPD/SWCNTs in CH3CN of
0.1 concentration , ? Raman spectra were
recorded at room temperature in a backscattering
geometry under excitation wavelengths of 514.5
and 676.4 nm with a Jobin Yvon T64000 Raman
spectrophotometer . ? FTIR spectra were obtained
in the 4004000 cm-1 range with a 4 cm-1
resolution, using a FTIR Bruker
spectrophotometer, Vertex 70 model.
? Fig. 5. HRTEM picture of POPD covalent
functionalized SWCNTs.
Fig. 7. SERS spectra recorded at ?exc 647nm of
SWCNT (curve a), the composite based on SWCNTs
functionalized with POPD doped with
H2PMo12O40- ions and tube fragments of shorter
length like closed shell fullerenes
functionalized with POPD (curve b) and POPD
(curve c).
Results and Discussions
Fig. 6. SERS spectra recorded at ?exc 514 nm of
the SWCNTs functionalized with POPD doped with
H2PMo12O40 - ions obtained by the chemical
polymerization of 1g ODP 5g H3PMo12O40 xH2O
in the presence of 0.1g (a1, a2) and 0.01 g
SWCNT (b1, b2).
SWCNT functionalized with POPD doped with
H2PMo12O40- ions. ?
CONCLUSIONS
This paper reports new results obtained by
surface enhanced Raman scattering (SERS) studies
on the chemical polymerization of OPD in the
presence of SWCNTs and H3PMo12O40 xH2O. The
following results may be highlighted (i) the
chemical interaction of SWCNTs with H3PMo12O40
xH2O leads to the formation of the
polyoxometallate-functionalized SWCNTs (ii) the
chemical polymerization of OPD in the presence of
FeCl3 and SWCNTs leads to POPD covalently
functionalized SWCNTs composite characterized by
a significant increase in intensity of the Raman
lines with maximum at 1536 and 1565 cm-1 this
behavior permits to conclude that a
functionalization of the side-wall of the tubes
with polymer took place (iii) the chemical
polymerization of OPD in the presence of SWCNTs
and H3PMo12O40 xH2O leads to the formation of an
organicinorganic hybrid composite of the type
SWCNTs functionalized with POPD doped with
H2PMo12O40- ions and tube fragments of shorter
length like closed shell fullerenes
functionalized with POPD (iv) the SERS spectrum
of tube fragments of shorter length like closed
shell fullerenes functionalized with POPD, is
characterized by new Raman lines situated at ca.
240 275 and 14501472 cm-1 .
Fig. 1. SERS spectra recorded at ? exc514 nm of
films of SWCNTs in their initial state (curve 1),
polyoxometallate-functionalized SWCNTs obtained
from the chemical interaction between 0.1 g
SWCNTs 5 g H3PMo12O40 xH2O (curve 2) and 0.01
g SWCNT 5 g H3PMo12O40 xH2O (curve 3). Curve 4
shows the Raman spectrum of the
polyoxometallate-functionalized SWCNT sample
interacted with 1M NH4OH solution.
Fig.2. SERS specra at ? exc647 nm of films of
SWCNTs in their initial state (a, curve black)
and polyoxometallate-functionalized SWCNTs
obtained fromthe chemical interaction of 0.1g
SWCNTs5gH3PMo12O40xH2O(curve red) and 0.01g
SWCNTs5gH3PMo12O40xH2O (curve green).The curve
blue (c) shows the Raman spectrum of
poly-oxometallate-functionalized SWCNTs sample
interacted with 1M NH4OH