Confinement-driven self-assembly of charged particles

Abstract

The field of bottom-up self-assembly focuses on the self-organization principles of basic atomic or molecular building blocks into well-ordered functional nano--materials with tailored properties.Assisted by bottom-up processes, nano--electronic devices can be realized and technological applications such as more efficient electrical energy storage devices, nano--machines and molecular drug delivery systems have come within reach.The physical properties of a material are usually determined not only by the related properties of its constituents but also by the microscopic structure of the material.Crucial to the understanding of the corresponding properties of a material is thus to first understand the structure a material will assume under certain external conditions.This thesis is dedicated to a comprehensive computational study of the structure formation processes of two different systems:first, we consider classical point-charges confined to the surface of two parallel, oppositely charged plates, the so-called asymmetric Wigner bilayer system.Second, we investigate a supramolecular system of charged, polycyclic aromatic molecules, deposited on a metal--liquid-interface under electrochemical conditions.We study the structure formation processes of both systems by minimizing the internal energy of the related models of the systems for different sets of the associated system parameters by employing sophisticated numerical tools.We systematically search in the asymmetric Wigner bilayer system for possible quasi-crystalline ordering:quasicrystals exhibit orientationally long-range ordered yet spatially aperiodic particle arrangements and have intriguing conceptual and technological implications.For selected combinations of the system parameters, we observe the formation of dodecagonal clusters and super-clusters of the point-charges, structures that are important precursors of aperiodic quasicrystalline ordering.For the study of the self-assembly processes of the supramolecular system, we propose a computationally lean approach to treat this problem reliably with elaborated numerical tools.In a semi-quantitative agreement with experimental data, the target molecules are seen to self-organize into two- and three-dimensional supramolecular lattices for different sets of the system parameters:the molecules form an open porous structure, an auto-host--guest pattern and a stratified bilayer.