Abstract
Carbon nanotube (CNT) membranes allow the mimicking of natural ion channels for applications in drug delivery and chemical separation. Double-walled carbon nanotube membranes were simply functionalized with dye in a single step instead of the previous two-step functionalization. Non-faradic electrochemical impedance spectra indicated that the functionalized gatekeeper by single-step modification can be actuated to mimic the protein channel under bias. This functional chemistry was proven by a highly efficient ion rectification, wherein the highest experimental rectification factor of ferricyanide was up to 14.4. One-step functionalization by electrooxidation of amine provides a simple and promising functionalization chemistry for the application of CNT membranes.
Highlights
A protein channel embedded in a cell membrane functions as a natural regulator in the biological system
Carbon nanotube (CNT) membranes were first modified by 4-carboxylphenyl diazonium grafting, and the negatively charged dye molecules were linked with carboxyl sites using carbodiimide coupling chemistry
The functionalization chemistry at the CNT tip determines the applications for CNT membranes, with the ideal gatekeeper being a monolayer grafted at the entrance of CNT cores that can actively pump chemicals through the pores [13]
Summary
A protein channel embedded in a cell membrane functions as a natural regulator in the biological system. Conformational change of proteins actuated by voltage can open or close the gate of the channel, which regulates ion permeation with high selectivity [1,2,3,4]. Transmembrane voltage is an excellent stimulus to open or close the gate of a nanodevice since it is not aggressive, is tunable, and can act over a short time scale [6]. It can modulate ionic flux and rectify ionic transport current through the nanochannel/ nanopore. The fluid velocity of a carbon nanotube membrane is 10,000 times faster than the conventional materials such as anodized aluminum oxide membranes [20]
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