U. Ortiz-Méndez

Synthesis and Properties of Monometallic and Bimetallic Silver and Gold Nanoparticles

ABSTRACT Au, Ag monometallic, and Au-Ag bimetallic nanoparticles have been synthesized by two different methods, the first one was the polyol method and stabilized with poly(vinylpyrrolidone) (PVP), modifying the temperature of synthesis. Interesting structure changes were observed in the nanoparticles as the temperature was varied. The second method consisted of successive reduction of metal salts with ascorbic acid on premade seeds in the presence of a cationic surfactant, cetyltrimethylammonium bromide (CTAB). In the first method at low temperatures, no bimetallic nanoparticles were detected, but as the temperature increased bimetallic nanoparticles started to appear, commonly obtaining core-shell nanoparticles, always covered by the polymer. This originates the modification of the optical response of the system in the ultraviolet (UV)-visible region. An absorption peak centered at 520 nm at low temperatures was observed (100–110°C); at higher temperatures (130–170°C) there were nondetectable absorptio...

Iron-based Nanomaterials in the Catalysis

Available data on catalytic applications of the iron-containing nanomaterials are reviewed. Main synthesis methods of nZVI, nano-sized iron oxides and hydroxides, core-shell and alloy structures, ferrites, iron-containing supported forms, and composites are described. Supported structures include those coated and on the basis of polymers or inert inorganic materials (i.e., carbon, titania or silica). Description of catalytic processes includes the decomposition reactions (in particular photocatalytic processes), reactions of dehydrogenation, oxidation, alkylation, C–C coupling, among a series of other processes. Certain attention is paid to magnetic recovery of catalysts from reaction systems and their reuse up to several runs almost without loss of

Chemical Characterization of DC-Sputtered In2O3 Films with a Top SnO2 Layer

In2O3 thin films with a top layer of SnO2 were deposited onto glass substrates by DC reactive-magnetron sputtering. After deposition, In2O3/SnO2 samples were annealed in vacuum at 400oC. Structural, optical, and chemical composition was investigated by X-ray diffraction, UV-Vis spectroscopy and XPS, respectively. X-ray data showed that films grow polycrystalline, where indium oxide crystallized in cubic as the main phase, with a preferential growth at the [0002] direction and lattice parameter of 10.11 Å. Signals of rhombohedral phase were also detected. XPS depth profiles show that tin coexists in Sn2+ and Sn4+, while indium maintains the In2O3 stoichiometry. Binding energy of Sn4+ bound to oxygen was detected at 468 eV while In2+ bound to oxygen at 444.7 eV. Nor tertiary compounds were detected at the In2O3/SnO2 interface, neither In or Sn in metallic state.

Synthesis of Transparent Conductive Thin Films of In2O3 and SnO2 by DC Magnetron Sputtering

Study of optical and microestructural properties in In2O3 and SnO2 multilayer thin films synthesis by DC magnetron sputtering characterized with SEM, X-RD and four point probe resistivity where is possible appreciate an enhancement in conductivity.

Synthesis and optical properties of Au@Ag bimetallic nanoparticles

Synthesis of Au, Ag monometallic, and Au-Ag bimetallic nanoparticles have been synthesised by successive reduction of metal salts with ascorbic acid on prefabricated seeds in the presence of cetyltrimethylammonium bromide (C16H33)N(CH3)3Br (CTAB), as a cationic surfactant, is presented in this paper. This coverage method for the prefabricated seeds is uniform, although in some cases deviations from a spherical shape are observed with the formation of nanorods or nanoprisms. Results using high-resolution STEM-XEDS elemental mapping suggest that the actual distribution of the two metals within the multilayer spheres may involve partial alloying of the metals.