I am analyzing carbon nanotubes by nanocasting (MNC), using SBA15 as a hard template. Composite C-SBA15 is the intermediate material with the carbon precursor within the SBA15 channels. In the Raman spectra of MNC and C-SBA15 comparing them with graphite, I observe a slight shift to the left of band D in the case of C-SBA15 and a slight shift to the right of band D in the case of MNC. Why does this happen?
The raman shift of the CNT D band is known to be dependent on CNT diameter and chirality. D band is also highly dependant on laser energy, although that is unlikely to be the issue in your case. Check section 4, and specifically 4.4 of this major review paper:
M.S. Dresselhaus et al. Raman spectroscopy on isolated single wall carbon nanotubes Carbon 40 (2002) 2043 –2061.
Article Raman spectroscopy on isolated single wall carbon nanotubes* 1
The raman shift of the D band can also be affected by electron/hole doping of the CNTs. The paper below shows this effect for graphene, but im assuming it applies to CNTs as well. Just haven't had time to search for a paper.
The Dependence of Graphene Raman D-band on Carrier Density
Liu et al., Nano Letters 2013 13 (12), 6170-6175
Article The Dependence of Graphene Raman D-band on Carrier Density
Hope that helps.
The raman shift of the CNT D band is known to be dependent on CNT diameter and chirality. D band is also highly dependant on laser energy, although that is unlikely to be the issue in your case. Check section 4, and specifically 4.4 of this major review paper:
M.S. Dresselhaus et al. Raman spectroscopy on isolated single wall carbon nanotubes Carbon 40 (2002) 2043 –2061.
Article Raman spectroscopy on isolated single wall carbon nanotubes* 1
The raman shift of the D band can also be affected by electron/hole doping of the CNTs. The paper below shows this effect for graphene, but im assuming it applies to CNTs as well. Just haven't had time to search for a paper.
The Dependence of Graphene Raman D-band on Carrier Density
Liu et al., Nano Letters 2013 13 (12), 6170-6175
Article The Dependence of Graphene Raman D-band on Carrier Density
Hope that helps.
The high-energy modes (HEM) of single-walled tubes (just below 1600 cm-1 region) originate from tangential vibrations of the carbon atoms along the nanotube walls. There is often a double-peak structure close to 1600 cm−1 that is a unique feature of single-walled carbon nanotubes, which is more reliable Raman signal for SWCNT than the RBMs in the low-energy range (typically somewhere in the 100-400 cm-1 range). For the SWCNT the most intense peak near 1600 cm-1 appears between 1592 cm−1 and 1596 cm−1, and the exact value depends on SWCNT diameter and the laser excitation energy used. It worth considering that fact that this mode in SWCNT is higher in frequency than the corresponding peak in graphite associated with a peak at 1589 cm−1. The smaller peak often seen between 1560 cm−1 and 1590 cm−1 changes dramatically for resonant excitation of metallic tubes. The overall quality of the SWCNT can also be judged based on the ration of the G-Band and D-Band. Moreover, the location of the D-Band varies for SWCNT, DWCNT, and MWCNT samples. Correlation between D-Band, G-Band, second order peaks of G-band (G*) and D-band (D*), as well as the RBM can shed more light on the natures of the CNT and its properties. Also chirality of the CNT sample and it phase (metallic vs. semiconductor) , etc. will impact the Raman spectra.
You may find a comprehensive article such as the one listed below and the references therein to provide useful information in view of your question.
- http://www.physik.fu-berlin.de/einrichtungen/ag/ag-reich/docs/Thomsen2007.pdf
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