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Here we investigate the electrochemical behavior of Pd/C synthesized by reduction with ethylene glycol in the presence of polyvinylpyrrolidone (EG-PVP). EG-PVP produces nanoparticles (NPs) with a narrow size distribution, but some of them remain covered by impurities after the synthesis. After successive voltammetric cycles, NPs become cleaner, but some agglomeration and structural modification occur; these effects affect the electrochemical behavior of Pd/C in different ways, so we used CO as a probe to better understand the processes taking place. CO stripping shows that the general features of the multiple oxidation peaks change with the number of cycles. Possibly, CO and OH from different NPs react when the particles agglomerate, contributing to CO stripping changes. Finally, different active areas are found when the charges involved in CO oxidation and PdO reduction are compared. Such differences are rationalized in terms of a balance between the increase of sites which promote the oxidation of CO and the loss of area provoked by the growing of the particles. Fil: Martins, Cauê A.. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Fernández, Pablo Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Troiani, Horacio E.. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Física de Metales; Argentina Fil: Martins, María Elisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Arenillas de la Puente, Ana. Instituto Nacional del Carbón; España Fil: Camara, Giuseppe A.. Universidade Federal do Mato Grosso do Sul; Brasil

Uniform polycrystalline SnO2 microtubes formed by sintered nanoparticles (fixed to a surface or in free standing form) were obtained with the infiltration technique using SnCl4 as precursor and a porous polycarbonate (PC) film as template. The advantage of this synthesis method was based on its simplicity, reproducibility, low cost, and the possible applicability to other complex oxides. The morphology and crystal structure of SnO2 tubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The crystalline sizes of the nanoparticles assembled in the tube walls obtained at 600 °C were in the range of 5–7 nm, calculated from both the XRD and the TEM data. The length of the microtubes fixed to a silicon nitride surface ranged between 2 and 7 μm. Sensors fabricated with this material showed unusual sensitivity to ethanol at room temperature and fast reversible response, as compared to those obtained by the deposition of metallic tin film and further oxidation (Rheotaxial Growth and Thermal Oxidation method).

Oat (Avena sativa) biomass was studied as an alternative to recover Au(III) ions from aqueous solutions and for its capacity to reduce Au(III) to Au(0) forming Au nanoparticles. To study the binding trend of Au(III) to oat and the possible formation of Au nanoparticles, the biomass and a solution of Au(III) were reacted for a period of 1 h at pH values ranging from 2 to 6. The results demonstrated that Au(III) ions were bound to oat biomass in a pH-dependent manner, with the highest adsorption (about 80%) at pH 3. HRTEM studies showed that oat biomass reacted with Au(III) ions formed Au nanoparticles of fcc tetrahedral, decahedral, hexagonal, icosahedral multitwinned, irregular, and rod shape. To our knowledge, this is the second report about the production of nanorods as a product of the reaction of a Au(III) solution with a biological material. These studies also showed that the pH of the reaction influenced the nanoparticle size. The smaller nanoparticles and the higher occurrence of these were observed at pH values of 3 and 4, whereas the larger nanoparticles were observed at pH 2. Fil: Armendariz, Veronica. University of Texas at El Paso; Estados Unidos Fil: Herrera, Isaac. University of Texas at El Paso; Estados Unidos Fil: Peralta Videa, Jose R.. University of Texas at El Paso; Estados Unidos. Universidad Nacional Autónoma de México; México Fil: José Yacamán, Miguel. University of Texas at El Paso; Estados Unidos Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. University of Texas at Austin; Estados Unidos Fil: Santiago, Patricia. Universidad Nacional Autónoma de México; México Fil: Gardea Torresdey, Jorge L.. University of Texas at El Paso; Estados Unidos

Nanopowders of La0.75Sr0.25Cr0.5Mn0.5O3−δ (LSCM) perovskite-type oxide, potential electrode material for symmetrical solid oxide fuel cell (S-SOFC), have been successfully prepared by the solution combustion method employing glycine as complexing agent and fuel. Several glycine-to-nitrates molar ratios were investigated. A detailed morphological and structural characterization was performed, employing X-ray diffraction, N2 physisorption, and electron microscopy (scanning and transmission). The as-synthesized LSCM nanopowders consist of interconnected nanoparticles forming a sponge-like structure with typical meso- and macropores. For glycine-to-nitrates molar ratios above stoichiometric molar ratio, a high proportion of well-crystallized LSCM phase was obtained. An increase of glycine content in the initial synthesis gel, decreases the average nanoparticles size from ~20 to ~6 nm, narrows the distribution crystallite size, and increases the specific surface area of the LSCM nanopowders from ~14 to ~30 m2/g. The evolution of crystalline phases of the as-synthesized LSCM nanopowders after calcination at various temperatures was studied: pure-phase La0.75Sr0.25Cr0.5Mn0.5O3−δ perovskites with particle-size distribution between 100 and 300 nm, have been obtained after calcination at 1,000 °C for 6 h. The crystalline structural analyses showed that the LSCM nanocrystallites have trigonal/rhombohedral symmetry in the R-3c space group. These final LSCM nanopowders present microstructures with low densification and open porosity but probably with sufficient integrity to enable them to be used as efficient electrodes in S-SOFC.