Raman spectra of functionalized
carbon nanotubes
G. Klupp, F. Borondics, R. Hackl*, K. Kamarás, E. Jakab**, S. Pekker
Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences,
Budapest, Hungary, e-mail: klupp@szfki.hu
*Walther Meissner Institute, Bavarian Academy of Sciences and Humanities, Garching, Germany
**Institute of Materials and Environmental Chemistry, Budapest, Hungary
Resonant Raman scattering
Tubes@Rice:
Pulsed laser vaporization  SWCNT + Ni/Co catalyst 
Refluxing with HNO3  SWCNT-COOH 
Heating to 800 ºC  SWCNT
Depth sampling
Intensity (counts/s)
1300
S33+S44
468 nm
Functionalization by modified Birch reduction [1]:
Li + n NH3  Li+ + e- (NH3)n
e- (NH3)n + C  C- + nNH3
C- + BzBr  BzC + BrC- + BuI  BuC + IC- + MeI  MeC + IC- + HX  HC + X(HX = H2O, NH3, CH3OH)
531 nm
S33
676 nm
M11
140
1400
1500
1600
1700
1300
Intensity (counts/s)
The samples
Funding
OTKA T 049338
Alexander von
Humboldt
Foundation
Bz-, H-SWNT
531 nm laser
70
120
1400
1500
1600
1700
1500
1600
1700
Bu-, H-SWNT
531 nm laser
80
40
0
1300
1400
1500
1600
1700
1300
-1
1400
-1
Raman shift (cm )
Raman shift (cm )
The samples are inhomogeneous  average spectra selected for comparison with TG-MS
The degree of functionalization (R+H)/100C was determined from
TG-MS.
[2]
A complete spectrum
900
1200
1500
3000
0.04
468 nm
531 nm
0.03
676 nm
I (counts/s)
0.10
468 nm
676 nm
0.05
531 nm
Gaussian
0.02
0.01
0.00
20
Bz
0
2
Bu
Me
4
6
0
0
0
Lorentzian
40
0.15
0
Bu-,H-SWNT
531 nm laser
ID/IG - ID /IG
60
600
0.05
ID/ID* - ID /ID*
300
Selectivity on tube type
0.00
-0.05
-0.10
8
Bz
0
(R+H)/100C
2
Bu
Me
4
6
8
(R+H)/100C
0
300
600
900
1200
1500
3000
ID/IG and ID/ID* increase with the degree of functionalization, as the change of the electronic structure is only minor. The ratio
depends on the wavelength of the exciting laser, as in Ref. 3. If we substract the value measured in the pristine sample (arising
from the defects of the pristine nanotube) the change is similar for both metallic and semiconducting nanotubes.
 The reaction is not selective for tube type
-1
Raman shift (cm )
No functional groups are visible and nanotubes are still in resonance.
 Electronic structure is not collapsed due to functionalization.
The same degree of functionalization leads to smaller changes in the electronic structure
in the case of apolar alkyl groups than in the case of polar substituted phenyl groups [3].
Selectivity on tube diameter
I (arb. u.)
80
200
250
SWNT
Me-,H-SWNT
468 nm
60
40
150
200
250
-1
Raman shift (cm )
I(small d RBM) / I(sum RBM)
150
Explanation of the selectivity
Most of the functionalization reactions are primarily selective to
metallic tubes [7], as these tubes have the nonzero DOS at the Fermi
level [8].
Birch-type alkylation begins with doping by excess Li, which fills
both S11, S22 and M11[9].
 The selectivity for metallic tubes is masked
0.8
0.7
0.6
0.5
0.4
The charged nanotubes are dispersed in the liquid NH3 solution.
 The size of the cavity in the bundle does not play a role.
0.3
0.2
0
2
4
6
8
(R+H)/100C
Carbanions having greater s-character are more stable.
 Smaller diameter tubes are more reactive
According to the RBM spectrum the small diameter semiconducting nanotubes react more readily.
This is in accordance with NIR[4, 5] and Raman[6] spectroscopic measurements on alkylated HiPCO tubes.
In the case of 531 nm and 676 nm laser excitation the change was obscured by the error.
References
[1]: F. Borondics, E. Jakab, S. Pekker: Journal of Nanoscience and Nanotechnology 7, 1551 (2007)
[2]: H. Kataura, Y. Kumazawa, Y. Maniwa, I. Umezu, S. Suzuki, Y. Ohtsuka, Y. Achiba: Synth. Metals 103, 2555 (1999)
[3]: C. Fantini, M. L. Usrey, M. S. Strano: J. Phys. Chem. C 111, 17941 (2007)
[4]: Á. Pekker, D. Wunderlich, K. Kamarás, A. Hirsch: Phys. Stat. Sol. B 245, 1954 (2008)
[5]: K. Németh, F. Borondics, E. Jakab, Á. Pekker, K. Kamarás, S. Pekker: Poster #5 on SIWAN 2008
[6]: M. Müller, J. Maultzsch, D. Wunderlich, A. Hirsch, C. Thomsen: Phys. Stat. Sol. B 244, 4056 (2007)
[7]: K. Kamarás, Á. Pekker: Handbook of Nanoscience and Technology, Editors: A. V. Narlikar, Y. Y. Fu, Oxford
University Press, 2009
[8]: M. S. Strano: J. Am. Chem. Soc. 125, 16148 (2003)
[9]: S. Kazaoui, N. Minami, R. Jacquemin, H. Kataura, Y. Achiba: Phys. Rev. B 69, 13339 (1999)