| The physical properties of nanoparticles are influenced by their size and shape. However, preparation of nanoparticles by chemical methods generally yields a wide range of sizes and morphologies. Thus it is important to develop techniques for preventing nanoparticle agglomeration and to simultaneously control the size and shape of the nanoparticles produced. Stabilizers are widely used to prepare nanoparticles; most of my research focuses on two kinds of stabilizers: surfactants and dendrimers. Chapter 1 outlines an introduction to nanoscience, metal nanoparticles, dendrimers and surfactants.; Dendrimers, which were first discovered and synthesized by Donald Tomalia in the late 1970's are monodisperse macromolecules with a regular and highly branched three-dimensional structure, and have been extremely explored for the past decade. Chapter 2 summarizes the synthesis of dendrimer-stabilized Cu, Pt, Ag and Au nanoparticles. The size of resulting metal nanoparticles was measured by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Two mechanisms by which dendrimers stabilize the formation of metal nanoparticles were also discussed: templating and arrested precipitation. In chapter 3, the reaction of poly(amidoamine) dendrimers with terminal hydroxyl groups (PAMAM-OH) with K2PtCl4 was studied by several NMR methods. The location and time course of the platinum ion uptake by the dendrimers provides valuable insight into the formation of Pt0 nanoparticles made in the presence of dendrimers as stabilizers. In chapter 4, the adsorption of G4OH dendrimer and dendrimer-stabilized platinum nanoparticles onto alumina supports was investigated using in-situ attenuated total reflection infrared (ATR-IR) spectroscopy.; Besides dendrimers, surfactants are also used to control the growth of metal nanoparticles. Chapter 5 and chapter 6 describe a seed-mediated growth method to make gold nanoparticles in the presence of different cetyltrimethylammonium bromide (C16TAB) analogues. The surfactants, head groups and tail groups were varied to explore the surfactant's structural effect on Au nanoparticle growth. It was found that as the length of the surfactant chain increased, the resulting gold nanoparticles' aspect ratio increased. (Abstract shortened by UMI.)... |
