J. J. S. Acuña

The catalytic evaluation of in situ grown Pd nanoparticles on the surface of Fe3O4@dextran particles in the p-nitrophenol reduction reaction

We report the catalytic activity evaluation of in situ grown Pd nanoparticles on the surface of superparamagnetic Fe3O4 particles coated with the natural polymer dextran, in the reduction of p-nitrophenol (Nip), in water, by sodium borohydride. The catalyst was fully characterized; its activity evaluated through kinetic studies and compared with recently reported catalysts using a new activity parameter. Applying a pseudo-monomolecular surface reaction approach, the reaction was also investigated by means of a theoretical adsorption model, which revealed that the reaction follows the Langmuir–Hinshelwood mechanism, where both molecules adsorb on the catalyst surface prior to undergoing a bimolecular reaction. Moreover, the catalyst could be reused five times without significant loss of Pd and with a high degree of Nip conversion.

Electrical Conductivity Studies of Polyaniline Nanotubes Doped with Different Sulfonic Acids

Self-assembled polyaniline (PANI) nanotubes were prepared in the presence of three different sulfonic acids as dopant, namely, p-toluenesulfonic acid, camphorsulfonic acid, and tetrakis(4-sulfonatophenyl)porphyrin, by oxidative polymerization using ammonium peroxydisulfate as the oxidant. The morphology of the PANI nanotubes was determined by SEM and TEM and the electrical conductivity was measured as a function of temperature. The PANI nanotubes were also characterized by FTIR, XRD, UV-Vis, and cyclic voltammetry. We have found that the dopants had a noteworthy effect on the electrical conductivity whithout significant changes in the morphology of the PANI nanotubes.

Magnetic Characterization of Co Doped Cu

In this work we have studied the magnetic properties of room temperature electrodeposited Cu2O layers doped with Co. These layers showed anhysteretic ferromagnetic behavior with Curie temperature of 550 K. Structural characterization indicated the incorporation of Co+2 ions to the Cu2O lattice. No evidences for the existence of superparamagnetic particles and contaminations were observed, respectively, from (zero field cooling) ZFC and (field cooling) FC curves and (electron paramagnetic resonance) EPR measurements.

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The hybrid structures composed of gold nanoparticles and carbon nanotubes were prepared using porous alumina membranes as templates. Carbon nanotubes were synthesized inside the pores of these templates by the non-catalytic decomposition of acetylene. The inner cavity of the supported tubes was used as nanoreactors to grow gold particles by impregnation with a gold salt, followed by a calcination-reduction process. The samples were characterized by transmission electron microscopy and X-ray energy dispersion spectroscopy techniques. The resulting hybrid products are mainly encapsulated gold nanoparticles with different shapes and dimensions depending on the concentration of the gold precursor and the impregnation procedure. In order to understand the electronic transport mechanisms in these nanostructures, their conductance was measured as a function of temperature. The samples exhibit a ‘non-metallic’ temperature dependence where the dominant electron transport mechanism is 1D hopping. Depending on the impregnation procedure, the inclusion of gold nanoparticles inside the CNTs can introduce significant changes in the structure of the tubes and the mechanisms for electronic transport. The electrical resistance of these hybrid structures was monitored under different gas atmospheres at ambient pressure. Using this hybrid nanostructures, small amounts of acetylene and hydrogen were detected with an increased sensibility compared with pristine carbon nanotubes. Although the sensitivity of these hybrid nanostructures is rather low compared to alternative sensing elements, their response is remarkably fast under changing gas atmospheres.