Bundle Size Engineering of Single-Walled Carbon Nanotubes on Silica Nanoparticles

Figure 4

Raman spectra and transmission electron microscopy images from small- and large-bundled SWNTs grown from cobalt clusters on 200 nm silica particle. (a) Raman spectra of large-bundled SWNTs are colored in blue. This curve shows 6 representative peaks (152 cm⁻¹, 208 cm⁻¹, 219 cm⁻¹, 228 cm⁻¹, 236 cm⁻¹, and 268 cm⁻¹). Small-bundled SWNTs (red colored spectra) show 2 representative peaks (158 cm⁻¹ and 207 cm⁻¹). Each peak has information about corresponding nanotubes chirality and electronic property. (, ) shows chiral vector of tube. M means the tube is metallic and S means semiconducting. Raman spectra of large-bundled SWNTs (blue) show more various and higher peaks. (b, c) TEM images of 0.2 wt% (c) and 0.4 wt% (d) samples. Several bundles are grown from Co clusters on the surface of silica particles making connection with each other. (d, e) High magnification TEM images show a bundle of SWNTs. Solutions concentration is 0.2 wt% for (d) and 0.4 wt% for (e). Several SWNTs construct one bundle and they are aligned with the direction of bundle. Bigger bundle is grown from higher concentration (0.4 wt%) sample.

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