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Posted: April 22, 2010
Hielscher Ultrasonics: Dispersing Individual Single-Walled Carbon Nanotubes by Ultrasonication
(Nanowerk News) Hielscher Ultrasonics offers powerful ultrasonic devices for detangling, dispersing, and the deagglomeration of nano-sized particles, such as Carbon Nanotubes.
Single-Walled Carbon Nanotubes (SWCNTs) are highly cohesive, so one of the major obstacles in processing SWCNTs is the inherent insolubility of the tubes in organic solvents or water. To use the full potential of SWCNTs, a simple, reliable and scalable deagglomeration process of the tubes is needed. Especially, the functionalization of the CNT side walls or open ends to create a suitable interface between the SWCNTs and the organic solvent results in partial exfoliation of the SWCNTs, only. Therefore, SWCNTs are mostly dispersed as bundles rather than individual deagglomerated ropes. If the condition during dispersion are too harsh, the SWCNTs will be shortened to lengths between 80 to 200nm. For the majority of practical applications, i.e. for semiconducting or reinforcing SWCNTs, this length is too small.
Ultrasonication is a very effective method of dispersing and deagglomeration of Carbon Nanotubes. Ultrasonic cavitation creates high shear forces. The liquid jet streams resulting from ultrasonic cavitation, overcome the bonding forces between the tubes and hence, the tubes become deagglomerated. A mild, controlled ultrasonic treatment is an appropriate method to create surfactant-stabilized suspensions of dispersed SWCNTs with high length.
Furthermore, ultrasonication as a polymer-assisted purification method allows to remove impurities from as-grown SWCNTs, effectively. The accurate control of the ultrasonication amplitude allows to limit damages of the SWCNTs.