Iron/cobalt-SBA-16 cubic mesoporous composites as catalysts for the production of multi-walled carbon nanotubes

A series of catalysts containing iron and cobalt nanoparticles supported on a highly ordered mesoporous cubic Im3m silica (SBA-16) were prepared by wet impregnation and used for the production of multi-walled carbon nanotubes (MWCNTs) by catalytic chemical vapor deposition (CCVD) of acetylene. The catalysts were characterized by low- and wide-angle X-ray diffraction, N2 physisorption analysis at 77 K and transmission electron microscopy to study the influence of different metal loading and impregnation time on the CCVD process. Quality and morphology of the MWCNTs was assessed by transmission and scanning electron microscopy, whereas thermal analysis was used to estimate the amount of CNTs produced. It was found that the nanocomposites are catalytically active with particular reference to samples with relatively high metal loading, and are stable under the conditions adopted for the CNT production by the CCVD process

Preparation and electrocatalytic activity of gold nanoparticles immobilized on the surface of 4-mercaptobenzoyl-functionalized multiwalled carbon nanotubes

Multiwalled carbon nanotubes (MWCNTs) were functionalized with 4-mercaptobenzoic acid in a polyphosphoric acid/phosphorus pentoxide medium to produce 4-mercaptobenzoyl-functionalized MWCNTs (MB-MWCNTs). Gold nanoparticles (GNPs), stabilized by trisodium citrate, were prepared from the in situ reduction of gold(III) chloride trihydrate by sodium borohydride in the presence of MB-MWCNTs dispersed in ethanol. The morphology of the resulting GNP/MB-MWCNT hybrid showed that GNPs were formed with an average diameter of 4.3 nm, and these were uniformly deposited on the surface of the MB-MWCNTs. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy studies revealed that the GNPs had a well-defined crystal structure. Cyclic voltammetry results showed a high electrocatalytic activity and electrochemical stability of the GNP/MB-MWCNT hybrid in both acidic and basic media.close7

The preparation of carbon nanotube/poly(ethylene oxide) composites using amphiphilic block copolymers

Polymer/multiwall carbon nanotube (MWCNT) composites were prepared by using amphiphilic block copolymers as dispersant. First, MWCNTs were wrapped with amphiphilic block copolymers in aqueous solution. Poly(ethylene oxide) was selected as the hydrophilic block because of its strong affinity with water while one of the following polymers: poly(ethylene), poly(butadiene), poly(styrene), poly(propylene oxide), or poly(thiophene) was used as the hydrophobic block of the copolymers. The dispersions were characterized by optical microscopy and transmission electron microscopy along with UV-Visible adsorption and dynamic light scattering. Based on the results, we could assess the effect on CNT dispersion quality of both, the molar mass of copolymers, the nature of the hydrophobic block and the length of hydrophilic block. The crystallization behavior of composites prepared from these dispersions was investigated. Results were related to the dispersion of the nanoparticles in the polymer matrix