Efficient anchorage of Pd nanoparticles on carbon nanotubes as a catalyst for hydrazine oxidation

Enzymatic degradation of aromatic hydrocarbon intermediates using a recombinant dioxygenase immobilized onto surfactant-activated carbon nanotube

This study examined the enzymatic decomposition of aromatic hydrocarbon intermediates (catechol, 4-chlorocatechol, and 3-methylcatechol) using a dioxygenase immobilized onto single-walled carbon nanotube (SWCNT). The surfaces of SWCNTs were activated with surfactants. The dioxygenase was obtained by recombinant technique: the corresponding gene was cloned from Arthrobacter chlorophenolicus A6, and the enzyme was overexpressed and purified subsequently. The enzyme immobilization yield was 62%, and the high level of enzyme activity was preserved (60-79%) after enzyme immobilization. Kinetic analyses showed that the substrate utilization rates and the catalytic efficiencies of the immobilized enzyme for all substrates (target aromatic hydrocarbon intermediates) tested were similar to those of the free enzyme, indicating that the loss of enzyme activity was minimal during enzyme immobilization. The immobilized enzyme was more stable than the free enzyme against abrupt changes in pH, temperature, and ionic strength. Moreover, it retained high enzyme activity even after repetitive use.

Carbon nanotube catalysts: recent advances in synthesis, characterization and applications

Carbon nanotubes are promising materials for various applications.

Fuel cell electrocatalyst using polybenzimidazole-modified carbon nanotubes as support materials

Toward the next generation fuel cell systems, the development of a novel electrocatalyst for the polymer electrolyte fuel cell (PEFC) is crucial to overcome the drawbacks of the present electrocatalyst. As a conductive supporting material for the catalyst, carbon nanotubes (CNTs) have emerged as a promising candidate, and many attempts have been carried out to introduce CNT, in place of carbon black. On the other hand, as a polymer electrolyte, polybenzimidazoles (PBIs) have been recognized as a powerful candidate due to the high proton conductivity above 100 °C under non-humid conditions. In 2008, we found that these two materials have a strong physical interaction and form a stable hybrid material, in which the PBIs uniformly wrap the surfaces of the CNTs. Furthermore, PBIs serve as effective binding sites for the formation of platinum (Pt) nanoparticles to fabricate a ternary composite (CNT/PBIs/Pt). In this review article, we summarize the fundamental properties of the CNT/PBIs/Pt and discuss their potential as a new electrocatalyst for the PEFC in comparison with the conventional ones. Furthermore, potential applications of CNT/PBIs including use of the materials for oxygen reduction catalysts and reinforcement of PBI films are summarized.

Adsorption of Triton X-series surfactants and its role in stabilizing multi-walled carbon nanotube suspensions

Surfactants can enhance the stabilization of carbon nanotubes (CNTs) in water through their adsorption, thus affecting the environmental behavior and application of CNTs. However, the quantitative relationship between adsorption and stabilization and the role of the surfactant structure in the surfactant-CNT interactions are largely unknown. Therefore, Triton X-series surfactants with a same hydrophobic functional group (4-(1,1,3,3-tetramethylbutyl)-phenyl) and different hydrophilic polyethoxyl chain lengths were selected to investigate their adsorption onto CNTs and their ability to stabilize CNT suspensions. Adsorption data were fitted well by Langmuir equation, indicating monolayer coverage on CNTs. Adsorption capacities of the surfactants increased with decreasing hydrophilic chain length: Triton-305<Triton-165<Triton-114<Triton-100. Electrostatic interaction and hydrogen bond could be excluded as the main mechanism because adsorption was not significantly affected by pH change. Hydrophobic and pi-pi interactions between the surfactants and CNTs were the dominant mechanism for their adsorption. CNT suspension data were well fitted to a nonlinear equation with a similar form to the Langmuir equation. Suspended CNT amounts in water were positively related to the adsorption capacities of the surfactants, but negatively with the hydrophilic fraction ratio of the X-series surfactants.