Minfang Zhang

Diameter-selective removal of single-wall carbon nanotubes through light-assisted oxidation

Abstract When single-wall carbon nanotubes (SWNTs) were treated with H2O2, rates of SWNT oxidative-degradation were found to be enhanced with irradiation of light. Raman spectroscopic study indicated that, when the irradiation periods were 2 and 5 min, the radial breathing modes of SWNTs having gap energies corresponding to the wavelength of the irradiated light selectively disappeared. This result suggests that SWNTs having a gap energy corresponding to the wavelength of the irradiated light were preferentially removed.

Thermogravimetric analysis of single-wall carbon nanotubes ultrasonicated in monochlorobenzene

The single-wall carbon nanotubes (SWNTs) purified by nitric acid were ultrasonicated in monochlorobenzene solution. Thermogravimetric analysis complemented by transmission electron microscopy and Raman spectroscopy was used to analyze the thus ultrasonicated SWNTs. The results show that two kinds of modified SWNTs and one modification-free SWNT coexist in ultrasonicated SWNTs and burned in three different temperature ranges. The different chemical modifications of SWNTs are likely to arise from their different structures. This provides a possible way to analyze and separate different structures of SWNTs.

Single-wall carbon nanotubes: a high yield of tubes through laser ablation of a crude-tube target

Abstract In the purification of single-wall carbon nanotubes (SWNTs), it has been difficult to remove graphitic particles. We were able to increase the percentage of SWNTs and decrease impurities in the form of graphite particles and amorphous carbon by using a new target. The target material was made of crude SWNTs, which contains SWNTs (20–30%), particles of graphite (about 10–20%), amorphous carbon (50–60%) and a little of Ni and Co (about 0.6%). The high yield of SWNTs obtained was attributed to the composition of the target and its porous structure.

Effect of polymer and solvent on purification and cutting of single-wall carbon nanotubes

Following our recent report that it is possible to purify and cut SWNTs by using a saw-edged homogenizer in a monochlorobenzene (MCB) solution of polymethylmethacrylate (PMMA) [Appl. Phys. A 71 (2000) 451], we report here our investigation of the effect of PMMA and MCB on the purification and cutting of SWNTs by thermogravimetric analyses. Our results show that MCB helps the a-C aggregation states to homogenize during the ultrasonic treatment. The PMMA helps to make bundles of SWNTs thinner and accelerates both the cutting and damaging of them.

Thermogravimetric analysis for the array of C60 molecules formed in single-wall carbon nanotube

Abstract The chemical stability of C 60 molecules encapsulated into single-wall carbon nanotubes (SWNTs), so-called peapods, against oxygen was analyzed by thermogravimetric analysis. The maximum values for the derivative on the weight loss were observed at temperatures higher by 140 °C than that of the C 60 powder and lower by 40 °C than that of SWNTs. This means that the outside SWNT prevented the combustion of C 60 molecules inside the peapods.

Effect of ultrafine gold particles and cationic surfactant on burning as-grown single-wall carbon nanotubes

Abstract Mizoguti et al. (Chem. Phys. Lett. 321 (2000) 297) reported that amorphous carbon (a-C) contained in as-grown single-wall carbon nanotubes could be burned preferentially by using ultrafine gold particles and cationic surfactant, benzalkonium chloride (BKC). We confirmed this result and found additionally that the optimum concentration of the ultrafine gold particles and BKC were, respectively, 0.6 atom% and 7 g/l. We studied the roles of ultrafine gold particles and BKC in this phenomenon; the ultrafine gold particles catalyzed the oxidation of carbonaceous materials leading to the decrease of the burning temperatures. BKC had the function of homogenizing the a-C aggregation states, which resulted in the burning of a-C in a narrow temperature range.