Revealing the interparticle magnetic interactions of iron oxide nanoparticles-carbon nanotubes hybrid materials

Spinel iron oxide nanoparticles capped with organic molecules have been successfully prepared and used to produce iron oxide nanoparticles-single wall carbon nanotubes hybrid materials, which were characterized by a number of experimental techniques. The nanoparticles in both samples have an average particle size of about 10 nm and acquire a chemical composition of the type Fe3-xO4, with 0<x<1/3. 57Fe Mössbauer spectroscopy and magnetization measurements suggest that the free capped nanoparticles experience stronger superparamagnetic effects with respect to the nanoparticles of the hybrid sample, which show stronger magnetic interparticle interactions. The mutual proximity of the magnetic nanoparticles of the hybrid sample is proposed to be the origin for this behaviour, which is triggered by their denser anchoring to the outer surface of the singe wall carbon nanotubes due to the reduced dimensions of the latter.

Controlled Synthesis of Carbon-Encapsulated Copper Nanostructures by Using Smectite Clays as Nanotemplates

Rhomboidal and spherical metallic-copper nanostructures were encapsulated within well-formed graphitic shells by using a simple chemical method that involved the catalytic decomposition of acetylene over a copper catalyst that was supported on different smectite clays surfaces by ion-exchange. These metallic-copper nanostructures could be separated from the inorganic support and remained stable for months. The choice of the clay support influenced both the shape and the size of the synthesized Cu nanostructures. The synthesized materials and the supported catalysts from which they were produced were studied in detail by TEM and SEM, powder X-ray diffraction, thermal analysis, as well as by Raman and X-ray photoelectron spectroscopy.Chemistry-a European Journa

Catalytic production of carbon nanotubes over Fe-Ni bimetallic catalysts supported on MgO

MgO supported bimetallic catalysts containing a combination of Fe and Ni metals in 1:1 ratio at varying loadings (from 1 to 50 wt.%) were prepared by a wet impregnation method. Carbon nanotubes were synthesized over the prepared catalysts by the catalytic decomposition of acetylene for different reaction conditions. The effect of reaction temperature, reaction time and metal loading to the yield, structural perfection and morphology of the synthesized carbon products was investigated using a combination of XRD, DTA/DTG, Raman spectroscopy and Scanning Electron Microscopy (SEM) techniques. The results revealed that both the selection of the growing conditions and the metal loading are critical for the nature of the synthesized carbon nanotubes and can assign their yield and their overall quality. The synthesized carbon nanotubes exhibit extended crystallinity while they were synthesized at high yields. (c) 2006 Elsevier B.V. All rights reserved.Diamond and Related Material

Synthesis and characterization of carbon nanotubes decorated with Pt and PtRu nanoparticles and assessment of their electrocatalytic performance

Novel hybrid electrocatalysts were developed based on the attachment of pre-formed capped Pt and PtRu nanoparticles (NPs) on the external surfaces of multi-walled carbon nanotubes (MWCNTs). MWCNTs chemically functionalized by both covalent and non-covalent chemical strategies were tested and evaluated as nanotemplates for the dispersion and stabilization of NPs. The suitable functionalized MWCNTs derivatives were then reacted with pre-formed capped Pt and PtRu NPs yielding the final hybrid materials. The intermediate products as well as the final hybrid materials were characterized in detail with a combination of experimental techniques including Raman spectroscopy, X-ray diffraction, scanning and transmission electron microscopy, while comparative studies regarding their electrocatalytic performance to the oxidation of methanol and ammonia, and to the reduction of hydrogen peroxide were made by performing cyclic voltammetry studies. The results revealed the uniform dispersion of very small NPs along the external surface of functionalized CNTs, while the most suitable electrocatalyst for each particular application is indicated. The chemical strategy followed for the surface functionalization of MWCNTs seems to greatly influence the catalytic activity of the resulting hybrids materials. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.International Journal of Hydrogen Energ

Synthesis and characterization of carbon nanotubes decorated with Pt and PtRu nanoparticles and assessment of their electrocatalytic performance

Novel hybrid electrocatalysts were developed based on the attachment of pre-formed capped Pt and PtRu nanoparticles (NPs) on the external surfaces of multi-walled carbon nanotubes (MWCNTs). MWCNTs chemically functionalized by both covalent and non-covalent chemical strategies were tested and evaluated as nanotemplates for the dispersion and stabilization of NPs. The suitable functionalized MWCNTs derivatives were then reacted with pre-formed capped Pt and PtRu NPs yielding the final hybrid materials. The intermediate products as well as the final hybrid materials were characterized in detail with a combination of experimental techniques including Raman spectroscopy, X-ray diffraction, scanning and transmission electron microscopy, while comparative studies regarding their electrocatalytic performance to the oxidation of methanol and ammonia, and to the reduction of hydrogen peroxide were made by performing cyclic voltammetry studies. The results revealed the uniform dispersion of very small NPs along the external surface of functionalized CNTs, while the most suitable electrocatalyst for each particular application is indicated. The chemical strategy followed for the surface functionalization of MWCNTs seems to greatly influence the catalytic activity of the resulting hybrids materials.International Journal of Hydrogen Energ

Modified Carbon Nanostructures As Catalysts For Oxygen Reduction Reaction

This work is oriented to take advantage of graphene and nanotubes features in electrocatalysis. At present, a main challenge in this context deals with obtaining inexpensive, energetically efficient and durable catalysts for oxygen reduction in Polymer Electrolyte Membrane Fuel Cells (PEMFC). Platinum and Pt-alloys are currently the best cathode catalysts for this reaction. However, since the metal is scarce and expensive, there is a strong effort to find alternative catalysts. Nitrogen-doped carbon catalysts, also containing iron and cobalt centres, appear to be good and promising platinum alternatives1. For outstanding electronic, mechanical and structural properties graphene oxide and nanotubes could be extremely interesting substitutes either as a catalyst itself or as catalyst support. In this work, we will present some preliminary electrochemical results on Oxygen Reduction Reaction about a series of graphene oxide intercalated with polyethyleneimine of different molecular weight2 and doped with iron, and iron doped nitrogen modified nanotubes, prepared using different nitrogen insertion methods. Physico-chemical characterisation will be also presented. 1 F. Jaouen, V. Goellner, M. Lefevre, J. Herranz, E. Proietti, J.P. Dodelet, Electrochim. Acta 87 (2013) 619. 2 T. Tsoufis, F. Katsaros, Z. Sideratou, B.J. Kooi, M.A. Karakassides, A. Siozios, Chem. A Eur. J., In Press, DOI: 10.1002/chem.201304599