Scarlett, Raynaldo Theodore

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  • Publication
    Computational Study of DNA-Directed Self-Assembly of Colloids
    (2010-05-17) Scarlett, Raynaldo Theodore
    Immense insight into fundamental processes necessity for the fabrication of nanostructures is gathered from studying the self-assembly of colloidal suspensions. These fundamental processes include crystal nucleation and particle aggregation. In this thesis, we developed an efficient computational framework to study the self-assembly of same-sized, spherical colloids with intermolecular interactions, such as the programmable DNA-mediated interaction. In the first part of this thesis, we studied the interfacial dynamics during colloidal crystallization. The interfacial dynamics of binary crystals was probed by weak impurity segregated growth. This segregated growth was interpreted as the number of surface bonds required to crystallize a fluid particle. For short-ranged DNA-mediated interactions, an integer number of surface bonds are needed for a particle to crystallize, which was verified by experiments. This demonstrates the utility of our computational framework to replicate growth kinetics of DNA-directed particle self-assembly. In the second part of this thesis, we studied the kinetic control of crystal structure in DNA-directed self-assembly. For a dilute colloidal suspension, with weak intermolecular interaction between similar particles, binary crystals can assemble into close-packed (cp) or body-centered-cubic (bcc) structures based on thermodynamic or kinetic factors. Under fast kinetic conditions bcc crystals assemble from the suspension. For the same intermolecular interactions and slow kinetic conditions, cp crystals are observed within the suspension.
  • Publication
    Computational Analysis of Binary Segregation During Colloidal Crytallization with DNA-mediated Interactions
    (2010-06-17) Scarlett, Raynaldo T; Crocker, John C; Sinno, Talid
    A detailed computational study of compositional segregation during growth of colloidal binary solid-solution crystals is presented. Using a comprehensive set of Metropolis Monte Carlo simulations, we probe the influence of colloid size, interaction strength, and interaction range on the segregation process. The results are interpreted in terms of a simple, but descriptive mechanistic model that allows us to connect to studies of binary segregation in atomic systems. The validity of Metropolis Monte Carlo simulations for the nonequilibrium phenomena investigated in this work is established theoretically and by connections to Brownian dynamics and molecular dynamics simulations. It is demonstrated that standard Metropolis Monte Carlo, properly applied, can provide an efficient framework for studying many aspects of crystallization in colloidal systems.