Mechanical agitation induces counterintuitive aggregation of pre-dispersed carbon nanotubes

Ricardo M.F. Fernandes, Matat Buzaglo, Oren Regev, István Furó, Eduardo F. Marques

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Mechanical agitation is commonly used to fragment and disperse insoluble materials in liquids. However, here we show that when pristine single-walled carbon nanotubes pre-dispersed in water are subject to vortex-shaking for very short periods (typically 10–60 s, power density ∼0.002 W mL−1), re-aggregation counterintuitively occurs. The initial dispersions are produced using surfactants as dispersants and powerful tip sonication (∼1 W mL−1) followed by centrifugation. Detailed imaging by light and electron microscopies shows that the vortex-induced aggregates consist of loose networks (1–102 μm in size) of intertwined tubes and thin bundles. The average aggregate size increases with vortexing time in an apparently logarithmic manner and depends on the dispersant used, initial concentration of nanotubes and size distribution of bundles. The aggregation is, nonetheless, reversible: if the vortex-shaken dispersions are mildly bath-sonicated (∼0.03 W mL−1), the flocs break down and re-dispersal occurs. Molecular insight for the mechanism behind this surprising phenomenon is put forth.

Original languageEnglish
Pages (from-to)398-404
Number of pages7
JournalJournal of Colloid and Interface Science
StatePublished - 1 May 2017


  • Aggregation
  • Dispersion
  • Network
  • Single-walled carbon nanotubes
  • Surfactant
  • Vortex-shaking

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry


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