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PHYSICAL SCIENCES / BIOLOGICAL SCIENCES / CHEMISTRY / BIOPHYSICS
Electrostatic gating of a nanometer water channel

Jingyuan Li^*,, Xiaojing Gong, Hangjun Lu^,, Ding Li, Haiping Fang^,, and Ruhong Zhou^,¶,||

*Department of Physics, Zhejiang University, Hangzhou 310027, China; Shanghai Institute of Applied Physics, Chinese Academy of Sciences, P.O. Box 800-204, Shanghai 201800, China; Department of Physics, Zhejiang Normal University, 321004 Jinhua, China; ^¶IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598; and ^||Department of Chemistry, Columbia University, New York, NY 10027

Edited by Ann E. McDermott, Columbia University, New York, NY, and approved January 9, 2007 (received for review June 1, 2006)

Water permeation across a single-walled carbon nanotube (SWNT) under the influence of a mobile external charge has been studied with molecular dynamics simulations. This designed nanopore shows an excellent on–off gating behavior by a single external charge (of value +1.0e): it is both sensitive to the available charge signal when it is close (less than a critical distance of 0.85 Å or about half the size of a water molecule) and effectively resistant to charge noise, i.e., the effect on the flow and net flux across the channel is found to be negligible when the charge is >0.85 Å away from the wall of the nanopore. This critical distance can be estimated from the interaction balance for the water molecule in the SWNT closest to the imposed charge with its neighboring water molecules and with the charge. The flow and net flux decay exponentially with respect to the difference between these two interaction energies when the charge gets closer to the wall of the SWNT and reaches a very small value once the charge crosses the wall, suggesting a dominating effect on the permeation properties from local water molecules near the external charge. These findings might have biological implications because membrane water channels share a similar single-file water chain inside these nanoscale channels.

carbon nanotube | molecular switch | nanogate

The authors declare no conflict of interest.

This article is a PNAS direct submission.

To whom correspondence may be addressed. E-mail: fanghaiping{at}sinap.ac.cn or ruhongz{at}us.ibm.com

© 2007 by The National Academy of Sciences of the USA

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