Charged Entities Interacting with Electronically Responsive Structures with Implications for the Modeling of Interactions between Carbon Nanotubes and DNA

Understanding interactions between charged entities with electronically responsive structures embedded in an electrolytic environment is important because of the diverse range of practical applications. This study was motivated by the technique where single stranded DNA was used to separate carbon nanotubes (CNTs) with different electronic properties (metallic or semiconducting).;The objective of this study was to create theoretical models which improve the understanding of the DNA-assisted separation technique for CNTs. In the course of this study four models with different levels of complexity at the continuum level were developed, with the electrostatic interaction being the main focus. In each of these models, with certain simplifications on geometry the boundary value problems for the electric potential were formulated using equations of electrostatics and in particular the Debye-H¨uckel theory for electrolyte. Using mathematical techniques, semi-analytical solutions for the electric potential were obtained and its implication for the DNA-CNT interaction and the property of the DNA-CNT hybrid were discussed. It was found that the electric potential due to a metallic CNT-DNA hybrid is weaker than that for a semiconducting CNT-DNA. In addition to that based on the proposed models, it was observed that the obtained results are applicable to a larger class of problems involving charged entities interacting with responsive structures. For example, it was studied how the phenomenon of counterion condensation on a polyelectrolyte (PE) is affected by the presence of a responsive cylinder. It was shown that counterions gradually release from the surface of the PE as it approaches a metallic cylinder, whereas more counterions are condensed on the PE as it approaches a dielectric cylinder where the dielectric constant of that cylinder ia smaller than that of the electrolyte solution.;Results from this dissertation clearly demonstrate that in order to model the interaction between a charged entity and an electronically responsive structure, it is crucial to account for the response of the structure. Therefore, the models developed here have implications for modeling interactions between other charged entities near responsive structures. For example, cells adhering to an implant’s surface and biosensors detecting a specific DNA sequence.