Date of Degree

2-2014

Document Type

Dissertation

Degree Name

Ph.D.

Program

Chemistry

Advisor(s)

Ilona Kretzschmar

Subject Categories

Chemistry | Nanoscience and Nanotechnology | Physical Chemistry

Keywords

asymmetric, chiral, colloid, GLAD, patchy particle, template

Abstract

Patchy colloidal particles have been widely studied as the self-assembly building blocks to illustrate their potential for forming complex structures. The parameters affecting the final assembly structures include (i) patch size, shape, and number per particle, (ii) their relative positions, and (iii) the surface properties of the patch material. Recent computational studies have highlighted the impact of patch shape on assembly structure; however, there are only a limited number of methods that can provide control over patch shape and size. In this thesis, a template is introduced to the Glancing Angle Vapor Deposition method (GLAD) to create surface anisotropy on colloidal particles with uniform and controlled patch size and shape. Further, a mathematical model is derived that instructs the patchy particle fabrication process and also assists in the quantitative description of patch area.

The template-assisted GLAD method is used to fabricate patchy particles, i.e., colloidal particles with a predefined patch on their surface. The patch size is controlled by varying the incident angle and rotation angle when particle size and template dimension are fixed. Due to the shadowing effect of the template and adjacent particles, a large variety of patch shapes can be achieved, including but not limited to symmetric semi-spherical caps and asymmetric crescent moon and triangular-shaped patches. A second vapor deposition enables the addition of another patch, which partly overlaps with the first patch. The mathematical model provides instruction on selecting adequate parameters to achieve a specific patch shape. In addition, it can also be used to calculate the patch size. In the model, the patch shape is defined in a three-dimensional space thereby enabling the description of various patch shapes obtained from the different fabrication parameters. Last but not least, the model also predicts patch position and calculates the size of the overlapping region of two patches.

Overall, the template-assisted GLAD method is illustrated to be a powerful tool for the control of patch size, shape and uniformity, while providing the opportunity for scalability and reduced occurrence of defects. Such patchy particles with a specific patch shape and/or multiple patches made of different materials have great potential to provide more intricate assembly structures and potential applications.

 
 

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