Structure and Diffusion Dynamics of Dopamine and Its Derivatives on Carbon Surfaces with Complex Morphologies

The configuration and surface diffusion dynamics of molecular adsorbates can be strongly affected by nanoscale surface complexities. Rapid and precise \textit{in vivo} electroanalytical detection methods have progressed as a result of advancements in carbon electrode materials with different micromorphologies, and the properties of these aqueous electrochemical interfaces are highly dependent upon their surface structures. In this dissertation, we use molecular dynamics simulations to investigate the adsorbed structures and surface diffusion dynamics of dopamine and its derivatives on pristine carbon surfaces with various surface complexities, including different curvatures, chiralities, edge conditions, and composite surfaces. In addition, we discuss several technical details of the molecular dynamics simulations that may bias the calculation of diffusion dynamics.

The configurational analysis shows that the spatial and orientational distributions of the adsorbates are both curvature-dependent and charge-dependent. The diffusivity analysis shows that diffusion is significantly enhanced by the concavity of the underlying carbon structure. In addition, as compared to a structureless atomic adsorbate, the internal structure of the adsorbed dopamine alters surface diffusion. These results provide insights into the physical processes of small molecular analytes on complex carbon microlectrode-aqueous interfaces, which is a fundamental and critical aspect for further understanding functional electroanalytical measurements across a wide variety of carbon microelectrodes.