title: Dispersing Carbon Nanotubes with Ionic Surfactants under Controlled Conditions: Comparisons and Insight.
abstract: A fundamental understanding of the mechanisms involved in the surfactant-assisted exfoliation and dispersion of carbon nanotubes (CNTs) in water calls for well-controlled experimental methodologies and reliable comparative metrics. We have assessed the ability of several ionic surfactants to disperse single and multiwalled carbon nanotubes, resorting to a stringently controlled sonication-centrifugation method for the preparation of the dispersions. The CNT concentration was accurately measured for a wide range of surfactant concentration, using combined thermogravimetric analysis and UV-vis spectroscopy. The obtained dispersibility curves yield several quantitative parameters, which in turn allow for the effects of nanotube morphology and surfactant properties (aromatic rings, chain length, headgroup charge, and cmc) to be assessed and rationalized, both in terms of dispersed nanotube mass and surface area. The data also indicate that the CNT-surfactant association follows patterns that are markedly different from other equilibrium processes governed by hydrophobicity (such as micellization); in particular, the surfactant concentration needed for maximum dispersibility, c(s,max), and the number of surfactant molecules per unit CNT area at c(s,max) are shown to depend linearly on chain length. The results further suggest that the presence of micelles in the exfoliation process is not a key factor either for starting CNT dispersibility or attaining its saturation value.
authors.affiliation: Centro de Investigação em Química, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto , Rua do Campo Alegre, s/n, P-4169-007 Porto, Portugal.|Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology , SE-10044 Stockholm, Sweden.
authors.forename: Ricardo M F
authors.initials: RM
authors.lastname: Fernandes
authors.affiliation: Centro de Investigação em Química, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto , Rua do Campo Alegre, s/n, P-4169-007 Porto, Portugal.
authors.forename: Bárbara
authors.initials: B
authors.lastname: Abreu
authors.affiliation: Centro de Investigação em Química, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto , Rua do Campo Alegre, s/n, P-4169-007 Porto, Portugal.
authors.forename: Bárbara
authors.initials: B
authors.lastname: Claro
authors.forename: Matat
authors.initials: M
authors.lastname: Buzaglo
authors.forename: Oren
authors.initials: O
authors.lastname: Regev
authors.affiliation: Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology , SE-10044 Stockholm, Sweden.
authors.forename: István
authors.initials: I
authors.lastname: Furó
authors.affiliation: Centro de Investigação em Química, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto , Rua do Campo Alegre, s/n, P-4169-007 Porto, Portugal.
authors.forename: Eduardo F
authors.initials: EF
authors.lastname: Marques