Degree

Doctor of Philosophy (PhD)

Department

Chemistry

Document Type

Dissertation

Abstract

This dissertation details the development of new fabrication strategies for the preparation of spatially selective surfaces by combining techniques of particle lithography and scanning probe microscopy (SPM). This combination of lithography and nanoscale surface characterization was applied to study the mechanisms of molecular level surface-assembly of organosilanes and porphyrin on surfaces of Si(111). Particle lithography was used to investigate the surface assembly of 4-chloromethylphenyltrichlorosilane (CMPS) within exposed sites of nanoholes in selected solvents and at selected temperatures to gain insight into the details of self-polymerization. Nanopillars of CMPS were generated under selected conditions of solvent and temperature and characterized with atomic force microscopy (AFM). CMPS nanopillars were shown to grow taller with more layers at higher reactions temperatures. It was also observed that CMPS nanopillars grown in toluene formed more fractured pillars with multiple domains from a single nanoholes, compared to nanopillars grown in bicyclohexane that were observed to have more structured growth and less diverse morphology. The self-assembly of CMPS was strictly confined to nanoholes with the surrounding matrix showing very little evidence of non-specific adsorption. Surface platforms of nanopatterned CMPS nanopillars were fabricated within a resistive thin film of octadecyltrichlorosilane (OTS) to spatially direct and pattern the addition of 5,10,15,20-Tetra(4-pyridyl)porphyrin. The generation of CMPS-porphyrin heterostructures was studied ex-situ and confirmed by statistically significant changes in nanostructure height before and after the porphyrin addition. The fabrication of CMPS-porphyrin heterostructures from morphologically diverse CMPS nanopillar foundations was studied to provide insight into the mechanisms of CMPS nanopillar self-assembly. The morphology of final stage heterostructures closely resembled the original morphology of the CMPs nanopillars with little evidence of non-specific adsorption across the OTS thin film resist. Particle lithography was used to fabricate silicon porphyrin nanostructures on surfaces of Si(111) via a porphyrin-silane coupling reaction. Previous steps for nanopatterning porphyrin on a surface included an additional step to of an organosilane linker molecular that the porphyrin molecules could bind and assembly from. This new protocol coordinates a silane to each porphyrin macrocycle though a simple single vessel reaction system developed by Kurihara et al.1 Through this coupling reaction porphyrins can be directly assembled on surfaces of silicon and glass. Porphyrin nanostructures of nanoholes, nanorings and nanopillars as well as porphyrin thin films were generated using this technique.

Date

11-3-2017

Committee Chair

Garno, Jayne C.

DOI

10.31390/gradschool_dissertations.4150

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