Strategies to Create Interfacial Patterning and Epitaxial Architectures Using Controllable Anisotropic Wetting at Scales < 10 nm on Polyfunctional Noncovalent Ligand Layers

Shi Wah Choong, Purdue University

Abstract

Chemical orthogonality at sub-10 nm is important in synthetic material applications. Synthetic materials require surfaces with two very different types of chemistry. For instance, nanoelectronics require repeating units of metal and oxide at 5- and 7-nm length scales. In polymer solar cells, the capability to cause n-type and p-type blocks to phase segregate at length scales < 10 nm would provide more efficient charge transport. Increasingly high resolution patterning has been achieved using lithographic techniques to manufacture devices with features as small as 14 nm and in some cases smaller. It is extremely difficult to precisely engineer and fabricate 3D interfaces with features less than 10 nm and high cost is associated with it. However, nature routinely addresses a similar challenge in the context of lipid bilayer, which has a thickness of about 6 nm. Lipid bilayer is made of phospholipids with an alternating hydrophilic and hydrophobic pattern to control the flow of water, ions and other small molecules across the cell membrane. The orthogonality of the lipid bilayer is hidden in the membrane core along the z-axis but for applications in nanoelectronics and organic photovoltaics, both chemical functionalities need to be displayed on the surface. My dissertation research focused on using bioinspired molecules to create precisely patterned layered materials with chemical orthogonality of ~6 nm, and utilizing these noncovalent monolayers to achieve molecular-scale wetting control, to create nanometer-thick film along the rows of headgroups using polar liquid as well as utilizing these polyfunctional layered materials to template epitaxial nanocrystals of small organic molecules. In this dissertation work, I have created nanoplates with thickness of ca. 1 nm as well as nanorods with length ~21 nm and width ~6 nm, which is similar to the lamellar width of the templating monolayers. These nanostructures adopt epitaxial alignment along the lamellae of the amphiphilic monolayers. My thesis work shows potential strategies useful for precise interfacial patterning for synthetic material applications at very short length scales.

Degree

Ph.D.

Advisors

Claridge, Purdue University.

Subject Area

Analytical chemistry

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