(637h) Combining AUC and SANS for the Characterization of Adsorbed Surfactant and Hydration Layers Around Colloidal Particles

Analytical ultracentrifugation (AUC) is a method which is widely used in the pharmacological world to characterize purified proteins and interactions between biomolecules. It is a powerful technique which allows for simultaneous sampling of the entire population distribution of a solute (e.g. proteins, DNA, particles). For colloidal particles, one can use AUC for the determination of particle size distributions, charge distributions, and for characterizing the size of an adsorbed dispersant or stabilizing ligand layer. In our work, we utilize AUC to measure the size of the adsorbed surfactant and hydration shells around the (7,6) species of single wall carbon nanotube (SWCNT). The samples used have been both chirality and length sorted to yield nanotube populations having not only narrow diameter and length distributions but also unique optical properties. In AUC, the sizes of the bound surfactant and hydration shells are determined from the data through a mass balance, but the spatial distribution of the surfactant on the nanotube or in the hydration shell is not elucidated. We aim to overcome this measurement limitation by additional measurements on the same chirality-sorted SWCNTs using small angle neutron scattering (SANS). Neutron scattering can provide information about feature sizes on the same length scales as determined in our AUC experiments and aids in constructing a clearer picture as to the spatial distribution of surfactant molecules on as well as away from the SWCNT surface. Such results not only push the current limits of nanoscale metrology but also improve our understanding of contemporary nanotube separation and purification processes on a broader scale by contributing knowledge pertaining to interactions between SWCNTs of different electronic properties with various types of amphiphilic molecules.