(460d) Study of Unique Kinetic Vs Thermodynamic Equilibria of Specific Chiralities of Single Walled Carbon Nanotubes

Aniruddha Kulkarni, Stephen Michel, Dr. Yang Zhao and Dr. Kirk J. Ziegler

University of Florida, Gainesville, USA.

kziegler@che.ufl.edu

Single walled carbon nanotubes (SWCNTs) find applications in electronics and biosensors owing to their unique optical properties. The range of applications is limited due to constraints in separating highly pure monochiral fractions. It has been reported that surfactant structure around the nanotubes plays an important role in separating pure fractions of desired (n,m) species. The presence of thermodynamically stable co-surfactant states around single walled carbon nanotubes enables the selective coating of (n,m) species in the solution. The desorption of surfactants is based on formation of these states at very specific ratios. Our group has previously utilized this approach to achieve selective elution of (6,5) nanotubes 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.

The exchange of surfactants on the surface of the nanotubes results in different kinetic and thermodynamic states. Adsorption of surfactant occurring at varying time scales based on the elution time differences suggests kinetically driven exchange. Here, we present unique behavior between kinetically and thermodynamically driven exchange of DOC on SDS coated SWCNTs. The solvatochromatic shifts of (n,m) species attributed to these exchanges taking place on the nanotube surface are probed with optical spectroscopy. The nature and extent of these shifts are based on chirality at specific CERC. Equilibrium studies were performed on specific chiralities to obtain thermodynamic parameters. These findings provide a promising pathway for investigating the possible role of enantiomers in coating of DOC to nanotubes.