Abstract
We investigated the purity and defects of single-wall carbon nanotubes (SWCNTs) produced by various synthetic methods including chemical vapor deposition, arc discharge, and laser ablation. The SWCNT samples were characterized using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Raman spectroscopy. Quantitative analysis of SEM images suggested that the G-band Raman intensity serves as an index for the purity. By contrast, the intensity ratio of G-band to D-band (G/D ratio) reflects both the purity and the defect density of SWCNTs. The combination of G-band intensity and G/D ratio is useful for a quick, nondestructive evaluation of the purity and defect density of a SWCNT sample.
Highlights
Evaluating the quality of single-wall carbon nanotubes (SWCNTs) is very important, both in basic research and industrial application
We show that the G-band peak intensity around 1593 cm−1 serves as a good index for the purity of as-grown SWCNTs produced by various synthetic methods, such as chemical vapor deposition (CVD), arc discharge, and laser ablation, even though their mean diameters differed
A comparative study of purity and Raman intensity was carried out for SWCNTs produced by various synthetic methods
Summary
Evaluating the quality of single-wall carbon nanotubes (SWCNTs) is very important, both in basic research and industrial application. Purity can be defined as a content ratio of SWCNTs to impurities, and the defect density can be defined as the abundance of structural defects on the nanotube walls. When there are fewer carbon impurities in the sample, the G/D ratio can be used to discuss SWCNT defects To resolve this uncertainty in the evaluation due to the double meaning of the D-band, a clearer scale reflecting either the purity or the defect density is required. We show that the G-band peak intensity around 1593 cm−1 serves as a good index for the purity of as-grown SWCNTs produced by various synthetic methods, such as chemical vapor deposition (CVD), arc discharge, and laser ablation, even though their mean diameters differed. An improved method of purity and defect evaluation using Raman spectroscopy is proposed
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