Single-Walled Carbon Nanotube Purification, Pelletization, and Surfactant-Assisted Dispersion:  A Combined TEM and Resonant Micro-Raman Spectroscopy Study

Abstract

Resonant Raman spectroscopy and transmission electron microscopy were used to characterize the structural changes of three single-walled carbon nanotube samples processed with purification, pelletization, and surfactant-assisted dispersion. A two-stage purification process selectively removes metallic tubes as well as small-diameter ones, enriching large-diameter semiconducting tubes. Pelletizing reduces the intertube distance but greatly increases the intensity ratio of the D band to the G band. Single-walled nanotube (SWNT) bundle size decreases during ultrasonication dispersion aided by a surfactant. SWNT bundles composed of large-diameter tubes are prone to debundling.

Aerosolization System for Experimental Inhalation Studies of Carbon-Based Nanomaterials

“…Grinding, heating, and purification can have an effect on the surface chemistry and size distribution of SW-CNTs (Shen et al 2005;Fenoglio et al 2008). For example, acid treatment can remove amorphous carbon, reduce lengths of entangled bundles, preferentially remove metal impurities, and introduce functional groups on the tube sidewalls (Shen et al 2005).…”

“…For example, acid treatment can remove amorphous carbon, reduce lengths of entangled bundles, preferentially remove metal impurities, and introduce functional groups on the tube sidewalls (Shen et al 2005). Because physicochemistry can potentially influence biological fate and transport and resultant health effects, it is of interest to understand how manipulation (i.e., purification and grinding) of SW-CNTs in our study influences these characteristics.…”

“…Because physicochemistry can potentially influence biological fate and transport and resultant health effects, it is of interest to understand how manipulation (i.e., purification and grinding) of SW-CNTs in our study influences these characteristics. Raman spectroscopy has been used as a means to not only characterize the surface chemistry and carbon bond defects of carbon-based nanomaterials but also evaluate the diameter, length, chirality, and matrix effects of SW-CNTs and MW-CNTs (Saito and Kataura 2001;Shen et al 2005). The intensity of the G band in Raman spectroscopy represents the in-plane stretching vibration of the carbon-carbon bonds within the graphene sheets.…”

“…The intensity of the G band in Raman spectroscopy represents the in-plane stretching vibration of the carbon-carbon bonds within the graphene sheets. The G band is commonly composed of two separate peaks: higher frequency peak (G2) due to vibrations along the axis and one of lower frequency (G1) caused by vibrations along the tube circumference (Shen et al 2005). The patterns of the G1 and G2 bands have been reported to shift depending on the presence of semiconducting versus metallic tubes (Brown et al 2001;Shen et al 2005).…”

“…The G band is commonly composed of two separate peaks: higher frequency peak (G2) due to vibrations along the axis and one of lower frequency (G1) caused by vibrations along the tube circumference (Shen et al 2005). The patterns of the G1 and G2 bands have been reported to shift depending on the presence of semiconducting versus metallic tubes (Brown et al 2001;Shen et al 2005). Comparing the G band spectrum of our FeSW-CNT versus cSW-CNT illustrates a shift of G2 to a lower frequency for cSW-CNTs (Figure 7), which is consistent with prior studies showing that nitric acid treatment preferentially eliminates metallic and smaller diameter tubes (Strano et al 2003;Shen et al 2005).…”