Abstract
Due to their unique properties, the single walled carbon nanotubes
(SWNTs) are very interesting candidates for the development of
new electronic devices and sensors. In order to be able to obtain
devices with similar and reproducible properties, it is necessary to
know the purity of SWNTs obtained di®erently, even from synthesis
methods for large scale production. Electron Spin Resonance (ESR),
which is a microwave resonant absorption method, can be a useful
characterization method, as it is very sensitive to the impurities and
defects.
Until now, macroscopic amounts of SWNTs can only be obtained
as mixtures of tubes with di®erent electronic properties. For this
reason the research has always been interested in a simple, fast, and
reliable method to detect the features of the SWNTs.
In this work, we discuss electron spin resonance parameters on se-
veral types of SWNTs and graphite. We recorded the ESR spectra
of di®erent SWNTs, obtained by di®erent methods. By comparing
room temperature ESR spectra of CVD, arc discharge and laser
ablation SWNTs we ¯nd evident di®erences in their parameters. It
is important to note that ESR spectroscopy is very sensitive to the
presence of residual magnetic catalyst particles, which are usually
needed to produce SWNTs. The simulation implemented by the ad-
dition of three lines allows the ¯tting to the experimental spectra.
For this reason, we also use arc discharge SWNTs synthesized with
non-magnetic catalyst. For a further elucidation of the signals ob-
tained, spectra at lower temperature have been recorded, and their
linewidth and intensity analyzed.
The double integration of the ESR line is calculated in order to esta-
blish a relationship between this area and the corresponding concen-
tration of SWNTs. In order to corroborate our results, we compare
the ESR spectra results with their corresponding Raman spectra.
