Doctor of Philosophy (PhD)
The capabilities for accomplishing fundamental surface studies with molecular systems are demonstrated in this dissertation using measurement and imaging modes of scanning probe microscopy. Model systems were chosen for investigations of surface self-assembly mechanisms, with an emphasis on understanding the role of interfacial water in surface reactivity. A key strategy for molecular level studies was to prepare nanostructures using protocols with colloidal lithography and scanning probe-based lithography (SPL). Nanofabricated samples were characterized ex situ with contact and tapping-mode atomic force microscopy (AFM) after key reaction steps, providing direct views of changes in surface morphology at the nanoscale. Magnetic sample modulation (MSM) combined with contact mode AFM provided a route to detect the vibration of magnetic nanomaterials in response to an externally applied electromagnetic field. Nanoscale measurements of the size-scaling effects for physical properties such as conductance and nanomagnetism are contemporary topics in the field of nanoscience. Protocols of SPL were used for studies with organic thin films; nanoshaving and nanografting experiments provided a means to prepare ultra-small nanostructures. Nickel-coated nanostructures were constructed on amine-terminated nanorings of aminopropyltriethoxysilane (APTES) using colloidal lithography and chemical steps of electroless deposition (ELD), nickel was deposited by an autocatalytic redox reaction using palladium as a catalyst. Protocols were developed to investigate the role of water in the association and placement of silane molecules on surfaces as a strategy for indirectly tracking the location of water on surfaces. Visible light photocatalysis was used to prepare nanostructured films by immersing surface masks of monodisperse spheres in solutions of an aryl halide and then irradiating the solution with blue light. Films of aryl halide are linked to the surface by C-Au bonds to form robust films that resist the effects of oxidation. Nanostructured films of octaethylporphyrin (OEP) were prepared with immersion particle lithography by reaction with silicon tetrachloride. Porphyrins bound to the surface through covalent Si-O-surface linkages coordinated to the centers of the macrocycles in a "kebob" arrangement. The Si-O-Si “skewer” strategy was also successful for encapsulating Au nanoparticles with porphyrins to make core-shell nanoparticles. Fundamental studies targeted questions related to controlling surface assembly and interfacial chemistry details.
Kuruppu Arachchige, Neepa Malsi Kumari, "Chemical Approaches for Nanofabrication Based on Colloidal Lithography with Organosilanes, Nanoparticles and Nickel Films: The Role of Water in Directing Surface Self-Assembly" (2019). LSU Doctoral Dissertations. 4921.
Garno, Jayne C