Abstract
Raman spectroscopy is a common method of studying carbon-based materials such as multi-walled carbon nanotubes (MWCNT). However, the analysis of this technique is non-trivial since recorded spectra may be a convolution of both molecular vibrations and phonon resonances. The energies of these physical processes may occur in the same energy regime, and hence several analytical approaches can be necessary for a full analysis. Due to the negligible quantities of non-graphitic carbon in MWCNT, the present fitting procedure focuses on understanding phonon resonances to elucidate how varying modifications of MWCNT ultimately influence their graphitic bulk structure. We have found this approach to provide greater insight into the structure of MWCNT when low quantities of amorphous carbon are present, when compared with methods which try to interpret both phonon scattering and molecular vibrations simultaneously. Different pre-treatments for the modification of the graphitic structure of MWCNT are compared, including aqueous acidic and gas phase methods, and statistically evaluated. Focusing on phonon resonances enables one to analyze the reaction process of nitrosulfuric acid pre-treatment at different temperatures. Thereby, it is possible to control the ratio between defects and graphitic structures in MWCNT samples and prepare samples with reproducible D/G ratios.
Highlights
Multi-walled carbon nanotubes (MWCNT) are highly interesting materials with many applications in catalysis, electronics, and the bio/medical fields due to their unique electrical and mechanical properties [1]
A fitting procedure based on single-phonon resonances for the Raman spectra of multi-walled carbon nanotubes (MWCNT) has provided us the opportunity to gain detailed and statistically sig
Samples with a high content of amorphous carbon should be analyzed by the fitting approach of Sadezky, et al [9], whereas the present fitting procedure is recommended for samples with high graphitic structure content
Summary
Multi-walled carbon nanotubes (MWCNT) are highly interesting materials with many applications in catalysis, electronics, and the bio/medical fields due to their unique electrical and mechanical properties [1]. It is critical to determine the ratio between defect sites and graphitic areas on MWCNT (here represented in the form of a D/G ratio) if one wishes to understand their material properties To this end, resonance Raman spectroscopy is a promising tool, which is already commonly used to analyze the electronic structure of MWCNT. We have created an analysis method for MWCNT containing high amounts of graphitic structure based on the evaluation of only singlephonon vibrations in Raman spectra [9] With this method, it is possible to describe the influence of different pre-treatment procedures, time, and temperature on MWCNT through the calculated D*/G ratio. Total reflection X-ray fluorescence (TXRF) measurements, which are cross-checked by gravimetric experiments, are performed to determine the influence of the different aqueous acid pre-treatments on removing this excess iron
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
