Abstract
Biological pores regulate the cellular traffic of a large variety of solutes, often with high selectivity and fast flow rates. These pores share several common structural features: the inner surface of the pore is frequently lined with hydrophobic residues, and the selectivity filter regions often contain charged functional groups. Hydrophobic, narrow-diameter carbon nanotubes can provide a simplified model of membrane channels by reproducing these critical features in a simpler and more robust platform. Previous studies demonstrated that carbon nanotube pores can support a water flux comparable to natural aquaporin channels. Here, we investigate ion transport through these pores using a sub-2-nm, aligned carbon nanotube membrane nanofluidic platform. To mimic the charged groups at the selectivity region, we introduce negatively charged groups at the opening of the carbon nanotubes by plasma treatment. Pressure-driven filtration experiments, coupled with capillary electrophoresis analysis of the permeate and feed, are used to quantify ion exclusion in these membranes as a function of solution ionic strength, pH, and ion valence. We show that carbon nanotube membranes exhibit significant ion exclusion that can be as high as 98% under certain conditions. Our results strongly support a Donnan-type rejection mechanism, dominated by electrostatic interactions between fixed membrane charges and mobile ions, whereas steric and hydrodynamic effects appear to be less important.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 17250-17255 |
| Number of pages | 6 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Volume | 105 |
| Issue number | 45 |
| DOIs | |
| State | Published - Nov 11 2008 |
| Externally published | Yes |
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Keywords
- Biomimetic platform
- Ion channel
- Ion transport
- Nanofiltration
ASJC Scopus subject areas
- General
Cite this
Ion exclusion by sub-2-nm carbon nanotube pores. / Fornasiero, Francesco; Hyung, Gyu Park; Holt, Jason K.; Stadermann, Michael; Grigoropoulos, Costas P.; Noy, Aleksandr; Bakajin, Olgica.
In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 105, No. 45, 11.11.2008, p. 17250-17255.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Ion exclusion by sub-2-nm carbon nanotube pores
AU - Fornasiero, Francesco
AU - Hyung, Gyu Park
AU - Holt, Jason K.
AU - Stadermann, Michael
AU - Grigoropoulos, Costas P.
AU - Noy, Aleksandr
AU - Bakajin, Olgica
PY - 2008/11/11
Y1 - 2008/11/11
N2 - Biological pores regulate the cellular traffic of a large variety of solutes, often with high selectivity and fast flow rates. These pores share several common structural features: the inner surface of the pore is frequently lined with hydrophobic residues, and the selectivity filter regions often contain charged functional groups. Hydrophobic, narrow-diameter carbon nanotubes can provide a simplified model of membrane channels by reproducing these critical features in a simpler and more robust platform. Previous studies demonstrated that carbon nanotube pores can support a water flux comparable to natural aquaporin channels. Here, we investigate ion transport through these pores using a sub-2-nm, aligned carbon nanotube membrane nanofluidic platform. To mimic the charged groups at the selectivity region, we introduce negatively charged groups at the opening of the carbon nanotubes by plasma treatment. Pressure-driven filtration experiments, coupled with capillary electrophoresis analysis of the permeate and feed, are used to quantify ion exclusion in these membranes as a function of solution ionic strength, pH, and ion valence. We show that carbon nanotube membranes exhibit significant ion exclusion that can be as high as 98% under certain conditions. Our results strongly support a Donnan-type rejection mechanism, dominated by electrostatic interactions between fixed membrane charges and mobile ions, whereas steric and hydrodynamic effects appear to be less important.
AB - Biological pores regulate the cellular traffic of a large variety of solutes, often with high selectivity and fast flow rates. These pores share several common structural features: the inner surface of the pore is frequently lined with hydrophobic residues, and the selectivity filter regions often contain charged functional groups. Hydrophobic, narrow-diameter carbon nanotubes can provide a simplified model of membrane channels by reproducing these critical features in a simpler and more robust platform. Previous studies demonstrated that carbon nanotube pores can support a water flux comparable to natural aquaporin channels. Here, we investigate ion transport through these pores using a sub-2-nm, aligned carbon nanotube membrane nanofluidic platform. To mimic the charged groups at the selectivity region, we introduce negatively charged groups at the opening of the carbon nanotubes by plasma treatment. Pressure-driven filtration experiments, coupled with capillary electrophoresis analysis of the permeate and feed, are used to quantify ion exclusion in these membranes as a function of solution ionic strength, pH, and ion valence. We show that carbon nanotube membranes exhibit significant ion exclusion that can be as high as 98% under certain conditions. Our results strongly support a Donnan-type rejection mechanism, dominated by electrostatic interactions between fixed membrane charges and mobile ions, whereas steric and hydrodynamic effects appear to be less important.
KW - Biomimetic platform
KW - Ion channel
KW - Ion transport
KW - Nanofiltration
UR - http://www.scopus.com/inward/record.url?scp=56249135271&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=56249135271&partnerID=8YFLogxK
U2 - 10.1073/pnas.0710437105
DO - 10.1073/pnas.0710437105
M3 - Article
C2 - 18539773
AN - SCOPUS:56249135271
VL - 105
SP - 17250
EP - 17255
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 45
ER -