Structural Study of Sulfur-Added Carbon Nanohorns.

In the past few decades, nanostructured carbons (NCs) have been investigated for their interesting properties, which are attractive for a wide range of applications in electronic devices, energy systems, sensors, and support materials. One approach to improving the properties of NCs is to dope them with various heteroatoms. This work describes the synthesis and study of sulfur-added carbon nanohorns (S-CNH). Synthesis of S-CNH was carried out by modified chemical vapor deposition (m-CVD) using toluene and thiophene as carbon and sulfur sources, respectively. Some parameters such as the temperature of synthesis and carrier gas flow rates were modified to determine their effect on the properties of S-CNH. High-resolution scanning and transmission electron microscopy analysis showed the presence of hollow horn-type carbon nanostructures with lengths between 1 to 3 µm and, diameters that are in the range of 50 to 200 nm. Two types of carbon layers were observed, with rough outer layers and smooth inner layers. The surface textural properties are attributed to the defects induced by the sulfur intercalated into the lattice or bonded with the carbon. The XRD patterns and X-ray microanalysis studies show that iron serves as the seed for carbon nanohorn growth and iron sulfide is formed during synthesis.

Water extractable arabinoxylan aerogels prepared by supercritical CO2 drying.

Water extractable arabinoxylan (WEAX) aerogels were prepared by extracting the solvent from the alcogels (WEAX hydrogels with an alcohol as the solvent) with carbon dioxide under supercritical conditions. WEAX aerogels were characterized using scanning electron microscopy and adsorption and desorption nitrogen isotherms. The micrographs indicate a heterogeneous porous network structure in WEAX aerogel. Adsorption/desorption nitrogen isotherms of this material were type IV, which confirm that this material possess a mesoporous structure. WEAX aerogels rehydration capability was evaluated and the water absorption mechanism was determined. The WEAX aerogels water absorption mechanism was non-Fickian (n = 0.54).

Arabinoxylan microspheres: structural and textural characteristics.

The aim of this research was to study the structural and textural characteristics of maize bran arabinoxylan (MBAX) microspheres. The laccase-induced cross-linking process was monitored by storage (G') and loss (G'') moduli changes in a 4% (w/v) MBAX solution. The G' and G'' values at the plateau region were 215 and 4 Pa, respectively. After gelation, the content of ferulic acid dimers decreased from 0.135 to 0.03 µg/mg MBAX, suggesting the formation of ferulated structures unreleased by mild alkaline hydrolysis. MBAX microspheres presented an average diameter of 531 µm and a swelling ratio value (q) of 18 g water/g MBAX. The structural parameters of MBAX microspheres were calculated from equilibrium swelling experiments, presenting an average mesh size of 52 nm. Microstructure and textural properties of dried MBAX microspheres were studied by scanning electron microscopy and nitrogen adsorption/desorption isotherms, respectively, showing a heterogeneous mesoporous and macroporous structure throughout the network.

A method to evaluate the tensile strength and stress-strain relationship of carbon nanofibers, carbon nanotubes, and C-chains.

A method is introduced to assess the tensile strength of carbon nanofibers, carbon nanotubes (CNTs), and linear chains of carbon atoms (C-chains) obtained from thin amorphous carbon films by electron irradiation. Transmission electron microscopy images show that the nanofibers undergo a radiation-induced necking process, characterized by CNT formation and often followed by the formation of a C-chain. Simulations of the necking process are carried out to determine the tensile stress supported by the nanofiber and CNT neck.

Noble-metal nanoparticles directly conjugated to globular proteins.

We report the synthesis of gold nanoparticles directly conjugated to bovine serum albumin protein by chemical reduction in aqueous solution. Transmission electron microscopy reveals that the gold nanoparticles are well dispersed with an average diameter less than 2 nm, and elemental analysis verifies the composition of the gold-protein conjugates. Infrared spectroscopy confirms that the polypeptide backbone is not cleaved during the conjugation process and that the side chain functional groups remain intact. Raman spectroscopy demonstrates that the disulfide bonds in the conjugated protein are broken and thus are available for interaction with the nanoparticle surface. This synthesis method is a new technique for directly attaching gold nanoparticles to macromolecular proteins.