| The original research described in this dissertation covers the development of nanomaterial syntheses directed by amphiphilic molecules. The focus is on two types of nanomaterials: one-dimensional gold nanostructures (nanorods and nano-bipyramids) and mesoporous metal oxides.;In the first part, large-aspect-ratio gold nanorods and nano-bipyramids of desired sizes were synthesized in high yields via a one-step seed-mediated process by using cetyltrialkylammonium bromide with different head groups (trimethylammonium, triethylammonium, tripropylammonium, and tributylammonium). The aspect ratios of the gold nanorods and bipyramids range from 2 to 70 and 2 to 6, respectively. The study indicates that the average aspect ratios of the Au nanostructures generally increase as the surfactant head group becomes larger. We also reported two approaches for changing the morphology of gold nanorods after growth. The first approach was achieved by a selective shortening of as-made gold nanorods via mild oxidation with oxygen. The second approach is based on a transverse overgrowth on as-made gold nanorods induced by the binding of more stable and larger molecules (glutathione/cysteine) onto their ends. During overgrowth, as-made nanorods underwent a gradual change from rods, peanuts, and truncated octahedra to faceted spheres.;In the second part, we have focused on mesoporous materials. By using similar amphiphilic molecules, we developed a simple one-phase route to the mesoporous silica fibers with diameters ranging from 50 to 300 nm and lengths up to millimeters, and similar mesoporous ribbons with 50 to 250 nm thick and 0.4 to 1.5 μm wide. The nanofibers were then used as templates to prepare gold nanoparticles along the fiber axis. The shape, orientation, and density of the gold nanoparticles embedded in the nanofibers can be controlled. These gold-nanoparticle-embedded nanofibers can be expected to find application in the areas of photonics and optoelectronics. We have further developed a method for generating mesoporous metal oxide submicrospheres by combining the acetic acid mediated sol-gel system (AcHE) together with the aerosol-assisted self-assembly approach. Mesoporous TiO2, ZrO2, and Al 2O3 spheres with highly crystalline frameworks and multi-component mesoporous CuO-TiO2, Al-Si-O, and BaTiO3 spheres have been chosen to demonstrate the generality of the approach. |
