Title:
In Silico Study of Nanoparticles in Soft Matter Environments
Abstract:
Nanoparticles have unique, size dependent properties which arise due to their small physical dimen-sions. These unique properties imbue nanoparticles with outstanding potential in most fields of modern technology. However, successful application of nanoparticles is predicated on controlling their syn-thesis, self-assembly and environmental impact. Achieving this control requires an understanding of both the chemical reactivity and physical behavior of nanoparticles. This is particularly true for soft matter applications, where the dynamic and deformable nature of the environment complicates charac-terization.
This dissertation aims to investigate physical properties of several nanoparticle-soft matter systems
using molecular dynamics computer simulations. By utilizing simulations, spatial and temporal reso-lutions unavailable to microscopy are accessed, enabling us to observe molecular behavior and calculate thermodynamic properties through statistical mechanics.
We begin by studying nanoparticles grafted with soft surfactant ligands, known to spontaneously
localize at fluid interfaces. We show that conventional theories treating the energetics of particle loca-lization fail at the nanoscale when the particle shape is deformable. Morever, we show that free surf-actants and nanoparticles exhibit synergy in lowering the oil-water interfacial tension, and propose a simple mechanism for this behavior.
Computer models allow us to consider different nanoparticle geometries by using simple continuum solids. This treatment yields analytical interaction potentials useful in probing nanoparticle behavior in their native environments. Spherical fullerenes can be approximated with a hollow shell, allowing the investigation of fullerene effects on lipid bilayers as a function of particle size. Carbon nanotubes can also be approximated with a cylinder allowing us to study the stability of nanotube dispersions in aqueous media.
Simulations can also be utilized to investigate the role that solvent plays in these systems. The feasibility of using multiparticle collision dynamics in equilibrium simulations is studied to develop
more efficient ways to treat the problem of simulating solvent dynamics, which otherwise accounts
for a majority of computational cost.
Nanoparticles hold immense promise in nanoscience, however a better knowledge of their behavior is essential to realize this promise. Much like in vivo and in vitro research, in silico studies can contribute to expand our knowledge of these unique materials.
Keywords: Nanoparticles, Soft Matter, Molecular Dynamics, Computational Chemistry, Free Energy, Surfactants, Youngs Equation, Carbon Nanotubes, Fullerenes, Lipid Bilayer, Pluronic.
Relevant Publications:
R. J. K. U. Ranatunga, R. J. B. Kalescky, C.-c. Chiu, and S. O. Nielsen. Molecular Dynamics Simulations of Surfactant Functionalized Nanoparticles in the Vicinity of an Oil/Water Interface. Journal of Physical Chemistry C 114, 12151-12157, (2010).
R. J. K. U. Ranatunga, C. T. Nguyen, B. A. Wilson, W. Shinoda, and S. O. Nielsen. Molecular Dynamics Study of Nanoparticles and Non-Ionic Surfactant at an oil/water interface. Soft Matter, 7, 6942-6952, (2011)
R. J. K. U. Ranatunga, and S. O. Nielsen. Application of a Continuum Mean Field Approximation to Fullerenes in Lipid Bilayers. Current Nanoscience, 7, 667-673, (2011)