Purification of nanotubes

CN s of exceptionally high purity are required for optimum performance in applications but the synthetic products usually contain impurities such as amorphous carbon, carbon nanoparticles, and some metal catalyst. Different methods have been described for the purification of nanotubes [77] most involve oxidation by use of mineral acids and/or gas phase oxidation to remove catalytic metal particles... 

The purification of nanotubes has been studied. It is relatively easier to purify the catalytically grown nanotubes than that from graphite vaporization. The metal catalysts and the inorganic support can be removed with HCl and HF solution. The transition metals can be dissolved in HNO3 solution. The amorphous carbon can be removed with HNO3 solution, and also by permanganate solution. Oxidation with air at mild temperatures is also effective in removing the amorphous carbon. 

Carbon nanotubes were first thought of as perfeet seamless eylindrieal graphene sheets —a defeet-free strueture. However, with time and as more studies have been undertaken, it is elear that nanotubes are not neeessarily that perfeet this issue is not simple bc-eause of a variety of seemingly eontradictory observations. The issue is further eomplicated by the faet that the quality of a nanotube sample depends very mueh on the type of maehine used to prepare it[l]. Although nanotubes have been available in large quantities sinee 1992[2], it is only recently that a purification method was found[3]. So, it is now possible to undertake various accurate property measurements of nanotubes. However, for those measurements to be meaningful, the presence and role of defeets must be elearly understood. 

Synthesis and Purification of Multi-Walled and Single-Walled Carbon Nanotubes... 

Filtration is also used to purify CNTs. Bandow [29] have reported a procedure for a one-step SWNT purification by microfiltration in an aqueous solution with a cationic surfactant. Shelimov [30] developed an ultrasonically assisted filtration method which allows the purity of nanotubes to reach >90%. 

K.B. Shelimov, R.O. Esenaliev, A.G. Rinzler, C.B. Huffman, and R.E. Smalley, Purification of singlewall carbon nanotubes by ultrasonically assisted filtration. Chem. Phys. Lett. 282, 429—434 (1998). 

Colomer, J.-F., P. Piedigrosso, I. Wilems, C. Journet, P. Bernier, G. Van Tendeloo, A. Fonseca, J.B. Nagy, Purification of catalytically produced multi-wall nanotubes.. Chem. Soc. Faraday Trans. 94,3753,1998. 

Pillai SK, Ray SS, Moodley M (2007) Purification of single-walled carbon nanotubes. J Nanosci Nanotechnol 7 3011-3047... 

Huang X, Mclean RS, Zheng M (2005) High-resolution length sorting and purification of DNA-wrapped carbon nanotubes by size-exclusion chromatography. Anal Chem 77 6225-6228... 

Pyrene and naphthalene were purified by zone refinement for more than 130 passes (Bridgmen method). After such purification the central part of the glass ampoule was extracted and used in the sample preparation. Drop coating of the pyrene (naphthalene) with SWNT suspension in toluene on a quartz substrate was used to form a thin film for Raman measurements. The film was deposited onto the quartz substrate from nanotube suspension in toluene (0.1 mg/mL) and from suspension of nanotube with pyrene (or naphthalene) after short sonication (20 minutes 44 kHz). The weight ratio was 1 1 and 1 4 for mixture with pyrene (samples PI and P2, respectively) and 1 1 with naphthalene (sample N). 

New Method of Purification of Carbon Nanotubes Based on Hydrogen Treatment... 

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