UC Irvine

Despite their inability to been seen with the naked eye, nanopores are ubiquitous to our cell membranes to regulate the passage of ions and molecules. Their superior selectivity, transport and sensitivity to external stimuli have inspired the innovation of solid-state nanopores for applications in single molecule sensing, label-free sequencing, filtration, energy harvesting, and more. Compared to macroscopic channels, nanopores exhibit these unique functionalities due to the large surface-to-volume ratio which facilitates the surface properties on the walls to dictate ion transport. It is imperative to understand the principles which govern transport at nanoscale interfaces to help solid-state systems replicate the superior capabilities observed in their biological inspirations. The solid-liquid interface in nanopores systems is well-understood for aqueous solutions which can often be described by a continuum model. However, standard descriptions fall short when applied to non-aqueous solvents which exhibit long-range ordering. In the first part of this dissertation, we aim to provide a molecular-level understanding of how the spatial organization of solvents at an interface influences electrochemical potential and, in turn, governs electrokinetic phenomena.Many separation platforms and energy-storage systems use non-aqueous solvents and rely on interactions at the interface for determining electrochemical properties. Here we probe the non-aqueous solvent, propylene carbonate, in the presence of salts using electrochemical measurements which rely on nanopores as a model system. We found that this solvent organizes at polar interfaces with a bilayer-like structure which dictates the position of ions in a concentration-dependent manner. We also take into consideration the chiral character of the solvent and show that the enantiomeric excess plays a role in determining interfacial ordering. This work aims to provide a complete description of the organization of solvent molecules at polar surfaces and underscores the need to consider the role of chirality. The second part of this dissertation focuses on preparing solid-state nanopore systems that fluctuate in diameter to better mimic biological channels which are believed to benefit from the ability to gate transport by undergoing conformation changes in pore shape. Here we propose a solid-state nanopore rendered dynamic by modifying a gold electromechanical gate with DNA. We show that the response of the DNA to an external electric field effects the ion transport within the pore and effective opening diameter. This result provides the first steps towards preparing non-equilibrium nanopore systems and achieving the complex functionality of biological nanopores.