Gated Chemical Transport and Enhance Flow through Carbon Nanotube Membranes

Keywords:
carbon nanotube, membrane, sensor, fluid flow

Abstract:
A promising architecture for ion-channel mimetics is a composite membrane structure containing vertically aligned carbon nanotubes, with inner core diameters of 7 nm, passing across a polystyrene matrix film. Plasma oxidation during the fabrication process introduces carboxylic acid groups on the CNT tips that are modified using carbodiimide mediated coupling between carboxylic acid on the CNTs and accessible amine groups of the functional molecule. Relative selectivity of the permeates was seen to vary from 1.9 to 3.6 as a function of tip-functionalization chemistry. Anionic charged functional groups are seen to sharply increase flux of cationic permeates. Biologically active desthiobiotin was also shown to be reversibly coordinated to stretavidin, showing a reduction in ionic flux through CNT. Pressure driven flux of a variety of solvents (H2O, hexane, decane ethanol, methanol) are 4-5 ORDERS OF MAGNITUDE FASTER than conventional Newtonian flow. There are also experimental indications of the ordering of polar solvents inside CNT pores. Dual functional CNTs (that is different functionality at each end of a CNT) have also been produced by reacting each side of the membrane with different functional solution, then subsequent removal of polymer matrix.

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Nanotech 2006 Conference Program Abstract