Synthesis and Characterization of Porphyrin-Encapsulated Nanoparticles: Investigations with Scanning Probe Microscopy
Doctor of Philosophy (PhD)
Scanning probe microscopy (SPM) encompasses a family of surface measurements that use a sharp probe to “feel” a surface. The tip is scanned point-by-point to build a map of the sample topography, which can be correlated with local measurements of surface properties. This dissertation outlines the history of SPM and describes techniques, operational modes, and applications. A review of force volume mapping (FVM), a 3D characterization mode of SPM used to map material properties detailed. Force volume mapping can be achieved by measuring multiple force measurements point-by-point in a grid pattern. Local properties such as chemical forces, dielectric properties, nanomechanical properties, electrical properties, and elastic response can be obtained from FVM.
Nanoparticles are materials that are less than 100 nm in diameter. Multiple approaches have been developed to synthesize nanoparticles and a survey of strategies for synthesizing nanoparticles of porphyrins is presented in this dissertation. The review focuses on the synthesis of porphyrinoid nanoparticles and emerging applications. A broad view of the different methods of synthesizing porphyrinoid nanoparticles provided fundamental background information for developing a new protocol for synthesizing core-shell nanoparticles.
A protocol for encapsulating metal nanoparticles with porphyrin macrocycles linked via silane coupling was investigated. Multilayers of porphyrins were covalently linked to the metal nanoparticles with metal-O-Si bridges. Porphyrins are macrocyclic compounds which have a rigid aromatic structure , are thermally stable, and have useful optical and electronic properties that have potential for molecular electronics. Incorporating porphyrins into nanoparticles or surface assemblies can introduce useful functionalities to the designed nanoparticles. A synthetic approach based on Si-O-Si coupling with tetrachlorosilane was used to form a skewered arrangement of coplanar porphyrins to form an organic shell on the outer periphery of metal nanoparticles (e.g gold, iron oxide, silver) in a core-shell assembly. Samples were characterized with tapping-mode AFM to compare the sizes and shapes of nanoparticles before and after encapsulation. Tapping-mode phase images sensitively pinpoints the differences in surface chemistry between the softer organic shell and hard metal cores. Colloidal lithography was used to control the arrangement of nanoparticles on glass substrates through direct deposition and immersion technique.
Olubowale, Olajumoke Helen, "Synthesis and Characterization of Porphyrin-Encapsulated Nanoparticles: Investigations with Scanning Probe Microscopy" (2023). LSU Doctoral Dissertations. 6158.
Garno, Jayne C.
Available for download on Tuesday, May 14, 2024