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Environment Effects on the Charge States of Metallic and Semiconducting SWCNTs during Their Separation by the Electric-Field Induced Layer Formation Method

Kuwahara, Yuki, Sasaki, Fusako, Saito, Takeshi
Journal of physical chemistry 2019 v.123 no.6 pp. 3829-3835
carbon nanotubes, chemical structure, electric field, electroosmosis, electrophoresis, environmental factors, pH, surfactants, zeta potential
The mechanism of separating metallic (m-) and semiconducting (s-) single-walled carbon nanotubes (SWCNTs) by electric-field induced layer formation (ELF) was investigated, by examining effects from the environmental conditions, that is, the pH and surfactant concentration on the separation process. Time course analysis showed that the pH and surfactant concentration in the cell become inhomogeneous during the ELF separation process. The ζ potential measurements revealed that the s-SWCNTs are much more negatively charged than m-SWCNTs in the specific pH range. The mechanism of ELF separation of m- and s-SWCNTs by forming layers is attributed to the dynamic changing/balancing of the electrophoretic and electroosmotic forces acting on the SWCNTs. The applicability of various surfactants for the ELF method was also discussed in terms of the surfactant types and the molecular structures.