Synthesis, characterization, and functionalization of transition metal phosphide nanomaterials from single source molecular precursors
Kelly, Anna Therese
Whitmire, Kenton H.
Doctor of Philosophy
This thesis details the synthesis, characterization, and functionalization of transition metal phosphide nanomaterials from single source molecular precursors. The decomposition of the organometallic cluster, H2Fe3(CO) 9PtBu, yielded iron phosphide (Fe2P) nanomaterials of various morphologies depending on the surfactants used for the decomposition. Branched nanostructures were observed as a result of crystal splitting in a few of the surfactant systems. Cross-shaped structures were also observed and attributed to the twinning of two individual bundles during growth as the result of an interrupted growth process. The role of the solvents in particular the use of oleic acid for the formation of nanorods, in the formation of Fe2P nanoparticles will be discussed. Magnetic measurements taken of a variety of different morphologies of these iron phosphide nanoparticles will also be presented. Fe2P nanoparticles were also isolated via the decomposition of other clusters, including Fe3(CO) (P tBu)2, Fe2(CO)6(PHtBu) 2, Fe4(CO)11PtBu2, and Fe3(CO)10PtBu. In order to study the mechanism by which the clusters decompose, the decompositions were monitored using infrared spectroscopy. For all of the systems studied, the clusters rearranged in the surfactant solutions, ultimately resulting in Fe2(CO) 6(PHtBu)2 prior to decomposition. This rearrangement is believed to be a result of the interaction of the clusters with the surfactants employed, suppored by the finding that the solid state decomposition of H 2Fe3(CO)pPtBu was found to result in a combination of Fe 3P, Fe2P, and Fe3O4. In addition to the formation of the binary phases of transition metal phosphide nanomaterials, investigation into the formation of mixed metal phosphides of iron and manganese were also performed. For these experiments, H2 Fe3(CO)9PtBu with a manganese source, either Mn2(CO)10 or Mn(CO)5Br, were decomposed in a variety of surfactant systems. The resulting nanoparticles were only doped with manganese; pure stoichiometric phases were not isolated. Finally the functionalization of Fe2P split rods, T-shapes, and crosses with a gold shell was performed. Their optical properties were studied, and a redshift in the extinction maximum was seen as the shell thickness increased. This plasmon peak shift, as opposed to the trends seen in silica-Au core-shell structures as shell thickness increases, is attributed to the high permittivity of the Fe2P core.