A 10-a editie a Seminarului National de nanostiinta si nanotehnologie

18 mai 2011 Biblioteca Academiei Romane

NATIONAL INSTITUTE OF MATERIALS PHYSICS BUCHAREST-MAGURELE

Atomistilor Str. 105 bis, P.O. Box MG-7, 077125 Magurele-Ilfov, Romania

Phone: +40(0)21 3690185, Fax: +40(0)21 3690177, email: barac@infim.ro, http://www.infim.ro

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 organic–inorganic hybrid composite of the type poly(o-phenylenediamine)/polyoxometallate-functionalized SWCNTs is produced by the chemical interaction between polyoxometallate-functionalized 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 240–275 and 1450–1472 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/polyoxometallate- functionalized SWCNT composite.

Experimental

☛ 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-functionalized 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 400–4000 cm-1 range with a 4 cm-1 resolution, using a FTIR Bruker spectrophotometer, Vertex 70 model.

Results and Discussions

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 organic–inorganic 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 1450–1472 cm-1 .

1200 1300 1440 1520 1600

1200 1300 1440 1520 1600

1200 1300 1440 1520 1600

1465

1320

1543

1518 1541

1563

1588

1588

b

1330

1561 1584

1610

No

rma

lize

d R

am

an

in

ten

sit

y

c

1590

1324

1544

1568

1590

a

Wavenumber (cm-1)

Fig.2. SERS specra at exc=647 nm of films of SWCNTs in their initial state (a, curve black) and polyoxometallate-functionalized SWCNTs obtained fromthe chemical interaction of 0.1g SWCNTs+5gH3PMo12O40xH2O(curve red) and

0.01g SWCNTs+5gH3PMo12O40xH2O (curve green).The curve blue (c) shows the Raman

spectrum of poly-oxometallate-functionalized SWCNTs sample interacted with 1M NH4OH

Fig. 1. SERS spectra recorded at exc=514 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.

1200 1350 1500 1550 1600 1650150 200

4

3

2

1

1340

1340

1593

1587 1593

Wavenumbers (cm-1)

156

4 x 0.8

168

170

165

3 x 0.32 x 0.6

1

170

156

Nor

mal

ized

Ram

an I

nte

nsi

ty

600 700 800 900 1000 1100 1200

a)

1090

852

980

1063

963

869

791

762 852 947

990

1047

1225

1230

1212

1090

3

2

41

Ab

so

rban

ce (

a.u

.)

Wavenumbers (cm-1)

Fig.3.FTIR spectra of SWCNTSs (curve 1a),H3PMo12O40xH2O(curve3a),polyoxometallate-functionalized SWCNTs (curve 2a) and the polyoxometallate-functionalized SWCNTs

sample interacted with a 1 M NH4OH solution (4a).

-1600 -1200 -2000

60

120

200 1200 16000

6000

12000

-1600 -1400 -12000

200

400

600

800

1200 1400 16000

2000

4000

6000

8000

1000 1200 1400 16000

1000

2000

-134

0

-156

9

a1

-170-1595

Ram

an In

ten

sity

a2

170

1340

1569

1594

b1

-159

5-1

569

-140

7-1

377

-135

0-1

322

-124

6

b2

1247

1370

1324

1409

1531

1569

1595

1578

1526

1488

1406

1368

1248

1154

c1

Wavenumbers (cm-1)

Fig. 4. SERS spectra recorded at λexc = 514 nm of the SWCNTs in their initial state (a1,a2), POPD covalently functionalized SWCNTs

(b1,b2) and POPD (c1).

Fig. 5. HRTEM picture of POPD covalent functionalized SWCNTs.

-1600 -1400 -1200 -200 -1000

125

250

100 200 1200 1400 16000

2500

5000

-1600 -1400 -1200 -200 -1000

10

20

30

100 200 1200 1400 16000

200

400

600

Wavenumbers (cm-1)

Ram

an in

ten

sity

(ar

b.u

nit

s)

-155

8

-168

-159

3

a1

168 13

621558

1593

a2

-155

8

-136

1-1

420

-1591

-165

b1

1420

1558

1591

1245

1361

b2

Fig. 6. SERS spectra recorded at λexc = 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).

100 200 3000

100

200

300

1000 1200 1400 1600 18000

600

1200

1800

2400

16

8

240

275

172

Wavenumber (cm-1)

Ram

an in

tens

ity (a

rb.u

nits

)

c

b

a

1367

1152 12

55

1472

1157

1222 12

6013

1513

5914

5014

86

1590

1543

1590

Fig. 7. SERS spectra recorded at λexc =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).

SWCNT functionalized with POPD doped

with [H2PMo12O40]- ions.: ☛