title: Single-Walled Carbon Nanotubes: Mimics of Biological Ion Channels.
abstract: Here we report on the ion conductance through individual, small diameter single-walled carbon nanotubes. We find that they are mimics of ion channels found in natural systems. We explore the factors governing the ion selectivity and permeation through single-walled carbon nanotubes by considering an electrostatic mechanism built around a simplified version of the Gouy-Chapman theory. We find that the single-walled carbon nanotubes preferentially transported cations and that the cation permeability is size-dependent. The ionic conductance increases as the absolute hydration enthalpy decreases for monovalent cations with similar solid-state radii, hydrated radii, and bulk mobility. Charge screening experiments using either the addition of cationic or anionic polymers, divalent metal cations, or changes in pH reveal the enormous impact of the negatively charged carboxylates at the entrance of the single-walled carbon nanotubes. These observations were modeled in the low-to-medium concentration range (0.1-2.0 M) by an electrostatic mechanism that mimics the behavior observed in many biological ion channel-forming proteins. Moreover, multi-ion conduction in the high concentration range (>2.0 M) further reinforces the similarity between single-walled carbon nanotubes and protein ion channels.
authors.affiliation: Department of Chemistry and ‡Department of Electrical Engineering, Columbia University , New York, New York 10027, United States.
authors.forename: Hasti
authors.initials: H
authors.lastname: Amiri
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Shepard
authors.affiliation: Department of Chemistry and ‡Department of Electrical Engineering, Columbia University , New York, New York 10027, United States.
authors.forename: Colin
authors.identifier: 0000-0002-0384-5493
authors.initials: C
authors.lastname: Nuckolls
authors.affiliation: Department of Chemistry and ‡Department of Electrical Engineering, Columbia University , New York, New York 10027, United States.
authors.forename: Raúl
authors.initials: R
authors.lastname: Hernández Sánchez
mesh_terms: D002412:Cations / Q000737:chemistry; D007473:Ion Channels / Q000737:chemistry*; D017136:Ion Transport; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010316:Particle Size; D010539:Permeability; D011108:Polymers / Q000737:chemistry; D016062:Porosity; D055672:Static Electricity; D013329:Structure-Activity Relationship; D013816:Thermodynamics
chemical_list: D002412:Cations; D007473:Ion Channels; D037742:Nanotubes, Carbon; D011108:Polymers
keywords: Ion channel; multi-ion conduction; nanofluidic device; single-walled carbon nanotubes