Doctor of Philosophy (PhD)
Chemically patterned surfaces were fabricated using a combination of molecular self-assembly and particle lithography to generate billions of nanostructures of organosilane self-assembled monolayers (SAMs). Monodisperse mesospheres were used as surface masks to prepare nanostructures on flat surfaces using the simple benchtop chemistry steps of mixing, centrifuging, evaporation, and drying. Periodic arrays of well-defined organosilane nanostructures serve as discrete surface sites for the selective deposition of polymers and magnetic nanoparticles.
In this dissertation, particle lithography approaches for surface patterning provide new directions for studying surface chemistry at the molecular-level using high resolution investigations with scanning probe microscopy (SPM). Atomic force microscopy (AFM) can be used to analyze samples in ambient and liquid environments. The solvent responsive nature of OTS nanostructures were investigated using in-situ liquid imaging with AFM. AFM provides unique capabilities for molecular visualization and ultrasensitive measurements of changes in heights, widths and surface coverage of the swollen OTS nanostructures with nanoscale resolution. Ring nanostructures of OTS presented a 3D interface for studying the interaction of solvents at the molecular level.
The vibrational response of patterned magnetic Fe3O4 nanoparticles in response to an applied external magnetic field was detected using magnetic sample modulation AFM (MSM-AFM). The vibration of Fe3O4 nanoparticles can be detected with a nonmagnetic AFM tip operated in continuous contact mode. In MSM-AFM, an AC current applied to the wire coil solenoid within the special sample plate drives the actuation of magnetic nanomaterials that are attached to surfaces. The magnetic Fe3O4 nanoparticles were induced to vibrate in the presence of externally applied electromagnetic field. Parameters such as frequency and magnetic field strength can be tuned in-situ to study dynamic changes in the vibrational response of samples. The AFM tip serves as a force and motion sensor for mapping the vibrational response of magnetic nanomaterials. The information acquired from MSM images includes the distribution of individual magnetic domains as well as spectra of the characteristic resonance frequencies of the vibrating magnetic nanomaterials.
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Kulkarni, Shalaka, "Chemically Patterned Surfaces as Test Platforms to Study Magnetic and Solvent-Responsive Properties at the Nanoscale: Investigations Using Scanning Probe Microscopy" (2015). LSU Doctoral Dissertations. 3046.