(7hg) Solvation Behavior of Self-Assembled Systems: Investigating the Colloidal Interface Via Molecular Simulations

Single walled-carbon nanotubes (SWCNTs) possess unique properties that make them attractive for a number of applications. However, the difficulty in obtaining uniform samples in terms of size, chirality, and handedness inhibits their widespread use. Various separation techniques address this problem through use of surfactants in order to suspend the tubes in aqueous media and then apply other approaches such as aqueous two phase extraction (ATPE) or ion-exchange chromatography (IEX) to sort the dispersed SWCNTs by their physiochemical properties. Single-stranded DNA (ssDNA) is a very effective dispersant that shows sequence-specific behavior during separation. Previous experimental work has shown that this specificity can be harnessed to tune the separation in favor of particular nanotube chiralities. Currently, the nature of this specificity is not yet well understood and optimal ssDNA/SWCNT pairs must be searched by trial and error. In this study, we use replica exchange molecular dynamics (REMD) simulations to assemble the ssDNA-SWCNT complexes and then apply free energy perturbation methods to obtain an estimate for the solvation energy of the complex. Such systems require the construction of a novel free energy pathway to access the quantity of interest. Additionally, the structure and dynamics of the hydrating water has been analyzed to better understand the solvation behavior on a molecular level and to provide insight into the effects of ssDNA sequence. These investigations work towards our goal to provide better insight into the sequence/chirality specific separation mechanism, and to eventually develop a model that allows for the prediction of other pairs leading to the efficient sorting of a desired nanotube chirality.

Research Interests:

My experience with the tool of molecular simulations has allowed me to explore a number of problems and to increase the breadth of my research interests. Molecular self-assembly, solvation behavior, membrane transport, and non-equilibrium thermodynamics all provide interesting topics which are accessible via various MD schemes. I would particularly be interested in continuing my current work dealing with the solvation of self-assembled systems and to extend this to other assembled species and molecular environments. This would help to focus on the application of such self-assembles complexes as they are often constructed to behave as sensors or delivery mechanisms and the local environments are crucial to their behavior and function.

Teaching Interests:

A strong background in engineering and a wide range of research experiences would allow me to be comfortable teaching many fundamental courses in chemical engineering. Of particular interest are undergraduate courses such as thermodynamics, numerical/computational methods, and transport phenomena; as well as graduate courses: thermodynamics, advanced heat and mass transfer, engineering mathematics. Additionally, I would be interested in developing a course more closely related to my research interests that would serve as an introduction to molecular simulations. This course would not only teach the basic concepts behind this technique, but also focus on application via projects and provide a survey of new directions within the field. Such a course was not available during my time in the classroom and would have been highly beneficial as I began my research career.