(361g) Study of Unique Thermodynamic Equilibria of Co-Surfactant Systems for Functionalizing Specific Chiralities of Single Walled Carbon Nanotubes

Single walled carbon nanotubes (SWCNTs) find applications in electronics and biosensors owing to their unique optical properties. Current biomedical applications are restricted due to constraints in separating highly monochiral fractions. Surfactant structure around the nanotube plays an important role in stability and separation of (n,m) species. The presence of thermodynamically stable co-surfactants states enables selective coating of species in solution. Our group has previously utilized this approach to elute (6,5) species at at very specific critical exchange ratio concentrations (CERC). The co-surfactant solution utilizes a ratio of sodium dodecyl sulphate (SDS)/sodium deoxycholate (DOC) to obtain single-chiral eluents of (6,5) species. This idea was further extended to obtain CERC values of different (n,m) species for the SDS-DOC co-surfactant system.

Here, we present utilization of this thermodynamic equilibria for selectively eluting a mixture of chiralities and modifying their functionality. Adsorption of added surfactant leads to reorganization of the surfactant shell around nanotube which leads to solvatochromatic shifts that can be probed through optical spectroscopy. Addition of DOC to SWCNT solution results in elution of a mixture of chiralities whose CERC is below the SDS/DOC ratio. Addition of SDS to this mixture results in opposite solvatochromatic shifts whose extent would indicate the surfactant reorganization around a particular (n,m) species. This would enable to functionalize selective species in solution. Different ligands were studied for functionalizing different chiralities for simultaneous detection of analytes in solution. This approach provides a promising pathway for using SWCNTs as biosensors by selectively functionalizing different chiralities without obtaining monochiral fractions.