Functionalization of multiwalled carbon nanotubes by mild aqueous sonication.

Sonication has been widely used in the dispersal of carbon nanotubes (CNTs) in various liquids as well as in their functionalization in aqueous acids. Here, for the first time, we study the sonication of multiwalled CNTs (MWCNTs) in deionized water. Our results indicate an improvement in the aqueous dispersal of MWCNTs as well as an increase in their adhesive interaction with Au substrates.

Spectroscopic evidence for pi-pi interaction between poly(diallyl dimethylammonium) chloride and multiwalled carbon nanotubes.

The interaction between multiwalled carbon nanotubes (MWCNTs) and aqueous poly(diallyl dimethylammonium) chloride (PDDA) was studied by X-ray photoelectron (XPS) and photoacoustic Fourier transform infrared (PA-FTIR) spectroscopies. We have found that the mild sonication of MWCNTs in aqueous PDDA results in a significant improvement of CNT dispersibility and greatly enhances their adhesion to Au and Si substrates. The MWCNT-PDDA interaction is due to the presence of an unsaturated contaminant in the PDDA chain, as confirmed by both XPS and PA-FTIR, which enters into a pi-pi interaction with the CNTs.

Controlled chemical functionalization of multiwalled carbon nanotubes by kiloelectronvolt argon ion treatment and air exposure.

The chemical and morphological modifications of multiwalled carbon nanotubes (MWCNTs), by 2 keV Ar(+) treatment, have been followed by field emission scanning (FESEM) and high-resolution transmission (HRTEM) electron microscopies and by X-ray photoelectron (XPS) and Raman spectroscopies. Morphological changes were followed, both in situ and on subsequent air exposure, and the data indicate that free radical defects, initially produced under low Ar(+) treatment doses ( approximately 10(13) ions/cm(2)), act as the nuclei for the formation of localized asperities that form along the walls of the CNTs. Continued treatment results in their stublike elongation that continues with further treatment, forming extensions under heavy treatment doses.