Synthesis and Applications of Non-spherical Dimer Colloids

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Synthesis and Applications of Non-spherical Dimer Colloids

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Title: Synthesis and Applications of Non-spherical Dimer Colloids
Author: Yoon, Kisun
Citation: Yoon, Kisun. 2012. Synthesis and Applications of Non-spherical Dimer Colloids. Doctoral dissertation, Harvard University.
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Abstract: Colloids are promising building blocks in material synthesis because of their controllability of size and surface properties. The synthesis of chemically and/or geometrically anisotropic colloidal particles has received attentions with the expectation of building blocks for complex structures. However, the synthesis of anisotropic colloidal particles is by far more difficult than the synthesis of spherical colloidal particles. Lack of monodispersity and productivity of many anisotropic particles often limits their applications as a building block for complex structures. Thus, it is highly desirable to develop methods which can produce a large amount of monodisperse non-spherical particles with controllable asymmetric surface properties. This dissertation details the work for developing such a method. The major result of this dissertation is a synthetic method to produce monodisperse non-spherical colloids with anisotropic surface property in a large quantity. The anisotropic colloid, which we call it as Dimer particle, has two fused lobes like a dumbbell and each lobe’s size can be independently controlled. We present a novel method to synthesize sub-micron size Dimer particles. This method can produce a large amount of submicron-sized Dimer particles with good monodispersity and well-controlled shape. Submicron-sized Dimer particles have been highly desired since they can be used as a building block for self assembly using Brownian motion, colloidal surfactant for Pickering emulsion, and photonic materials. To fully take advantage of the anisotropy of the particles, we develop a facile method to tailor the surface property of each lobe independently by asymmetrically coating the particles with gold nanoparticles. This method doesn’t need the arrangement of particles onto any type of interfaces. Asymmetric coating of gold nanoparticles can be carried out simply by mixing Dimer particles with gold nanoparticles. The formation mechanism of the submicron-sized Dimer particles is explained with evidences. Finally, we illustrate that Dimer particles show rich phase behavior under electric fields and explain the behavior by considering various interactions involved in the system. Our investigation shows that electric field can effectively control the orientation and assembled structure of Dimer particles. In conclusion, these asymmetrically functionalized Dimer particles are promising building blocks to generate suprastructures that will be useful in photonic, electronic and diagnostic applications.
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Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:9767979
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