Effect of Mild Nitric Acid Oxidation on Dispersability, Size, and Structure of Single-Walled Carbon Nanotubes
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- 作者：Maxim N. Tchoul ; Warren T. Ford ; Giulio Lolli ; Daniel E. Resasco ; Sivaram Arepalli
- 刊名：Chemistry of Materials
- 出版年：2007
- 出版时间：November 13, 2007
- 年：2007
- 卷：19
- 期：23
- 页码：5765 - 5772
- 全文大小：429K
- 年卷期：v.19,no.23(November 13, 2007)
- ISSN：1520-5002
文摘
Oxidation of single-walled carbon nanotubes (SWNTs) with nitric acid increases their dispersabilityin water, methanol, and N,N-dimethylformamide. Two oxidation protocols, sonication in 8 M HNO3 at40 C and reflux in 2.6 M HNO3, have been examined using SWNTs produced by the CoMoCat, HiPco,and pulsed laser vaporization (PLV) methods. The dispersability of all types of nanotubes increasedsubstantially after 1 h of sonication and after 2-4 h of reflux. Longer treatments resulted in little furtherimprovement in dispersability and at reflux degraded the SWNTs. Stable dispersions of CoMoCat SWNTsin DMF at concentrations as high as 0.4 g/L were achieved without the use of surfactants or polymers.Raman spectroscopy showed greater covalent functionalization of the SWNTs by the reflux procedurethan by the sonication procedure. Concurrent with improved dispersability, oxidation resulted in smallerdiameters and shorter lengths as determined from AFM images, which show mostly bundles rather thanindividual tubes. The lengths of SWNTs after oxidation decreased in the order PLV > HiPco > CoMoCat.Recommendations for the method of conditioning of the various types of SWNTs depend on their intendeduse.