Surface Functionalization with Self Assembled Monolayer: A Route to Adoption of Wide Diameter CNTs for Osmotic Processes

Osmotic transport across Carbon Nanotube (CNT) channels is of great scientific and technological interest. Commercial processes such as reverse osmosis, reversed electrodialysis, forward osmosis, pressure retarded osmosis and osmotic power generation can benefit vastly from the high water permeabilities afforded by the narrow hydrophobic CNT channels. The characterization of osmotic transport inside CNT channels therefore becomes imperative for realizing the potential of CNT channels for any of the above applications. Osmotic permeabilities were determined for the first time, last year, using very short CNT porins. However, for realization of CNT membranes for commercial applications, knowledge of osmotic permeabilities of mm-long CNT channels that can form channels in a membrane platform is essential. In my talk, I will introduce results from the osmotic water transport measurements using wider, 2.2 nm CNT channels, that are much more readily amenable for technological adoption. Further, our results have indicated that surface functionalization using a long chain molecule such as octadecylphosphonic acid on the surface of our CNT-titania membrane can be used to reduce the backflux of salt or draw solute (NaCl). Using the CNT membrane platform, we are also able to see occurrence of a related nanofluidic phenomenon of diffusio-osmotic flow that reflects strong ion-channel interactions inside CNT, which can be harnessed for the development of CNT based nanofluidic devices for applications in sensing and drug delivery.