Dissociation of electrolytes in a nano-aqueous system within single-wall carbon nanotubes

Research on material incorporation within single-wall carbon nanotubes (SWNTs) through aqueous solutions of various electrolytes is performed for the purpose of providing a foundation for future application of SWNTs to, for example, drug delivery systems. We have determined that the optical spectra of SWNTs were significantly affected when SWNTs that had opened holes or removed caps were treated through immersion in an aqueous solution of electrolytes, followed by drying at room temperature; however, the spectra of SWNTs without opened holes or removed caps were not subjected to such treatment. We infer that when the sucked solutions remained inside the tubes, even after drying (the nano-aqueous system), the electrolyte was dissociated into ions, which was likely to change the electronic states of SWNTs. On the other hand, when the SWNTs were well-dried under vacuum, no remarkable changes in their optical spectra were observed.     

A note on the convergence of multiconfigurational many-body perturbation theory

The convergence of multiconfigurational many-body perturbation theory (MC MBPT ) is discussed in connection with the intruder state. Its convergence properties are first examined with a fictitious three-level system employing a Hermitian version of MC MBPT , which permits a general model space. It is then applied to the H₂—H₂ and N₂ systems. The results suggest that a more extensive model space is likely to embrace new intruder states and the space extension be executed with due caution.     

Creation of a mixed-valence state from one-dimensionally aligned TTF utilizing the self-assembling nature of a low molecular-weight gel

One-dimensional TTF assemblies have been obtained through the design of low molecular-weight gels, which show a characteristic absorption band at around 1750 nm upon I2 doping, assignable to a mixed-valence state of the TTF assemblies.     

Synthesis of poly[N‐isopropylacrylamide‐g‐poly(ethylene glycol)] with a reactive group at the poly(ethylene glycol) end and its thermosensitive self‐assembling character

Poly[N‐isopropylacrylamide‐g‐poly(ethylene glycol)]s with a reactive group at the poly(ethylene glycol) (PEG) end were synthesized by the radical copolymerization of N‐isopropylacrylamide with a PEG macromonomer having an acetal group at one end and a methacryloyl group at the other chain end. The temperature dependence of the aqueous solutions of the obtained graft copolymers was estimated by light scattering measurements. The intensity of the light scattering from aqueous polymer solutions increased with increasing temperature. In particular, at temperatures above 40°C, the intensity abruptly increased, indicating a phase separation of the graft copolymer due to the lower critical solution temperature (LCST) of the poly(N‐isopropylacrylamide) segment. No turbidity was observed even above the LCST, and this suggested a nanoscale self‐assembling structure of the graft copolymer. The dynamic light scattering measurements confirmed that the size of the aggregate was in the range of several tens of nanometers. The acetal group at the end of the PEG graft chain was easily converted to the aldehyde group by an acid treatment, which was analyzed by ¹H NMR. Such a temperature‐induced nanosphere possessing reactive PEG tethered chains on the surface is promising for new nanobased biomedical materials. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1457–1469, 2006     

The improved Kolbe-Schmitt reaction using supercritical carbon dioxide

A comparative analysis of the reactions between sodium phenoxide and CO₂ under the gaseous and supercritical conditions has demonstrated the preferential effect of supercritical conditions for promoting the reactivity of CO₂. A significant increase in product yield was obtained in supercritical CO₂ compared to reactions undertaken in gaseous CO₂.     

Tooth enamel proteins enamelin and amelogenin cooperate to regulate the growth morphology of octacalcium phosphate crystals

To examine the hypothetical cooperative role of enamelin and amelogenin in controlling the growth morphology of enamel crystals in the post-secretory stage, we applied a cation selective membrane system for the growth of octacalcium phosphate (OCP) in the truncated recombinant porcine amelogenin (rP148) with and without the 32kDa enamelin fragment. Enamelin alone inhibited the growth in the c-axis direction more than rP148, yielding OCP crystals with the smallest aspect ratio of all conditions tested. When enamelin was added to the amelogenin "gel-like matrix", the inhibitory action of the protein mixture on the growth of OCP in the c-axis direction was diminished, while that in the b-axis direction was increased. As a result, the length to width ratio (aspect ratio) of OCP crystal was markedly increased. Addition of enamelin to amelogenin enhanced the potential of amelogenin to stabilize the amorphous calcium phosphate (ACP) transient phase. The ratio of enamelin and amelogenin was crucial for stabilization of ACP and the growth of OCP crystals with larger aspect ratio. The cooperative regulatory action of enamelin and amelogenin was attained, presumably, through co-assembling of enamelin and amelogenin. These results have important implications in understanding the growth mechanism of enamel crystals with large aspect ratio.