A combination of hard and soft templating for the fabrication of silica hollow microcoils with nanostructured walls

Hollow silica microcoils have been prepared by using functionalized carbon microcoils as hard templates and surfactant or amphiphilic dye aggregates as soft templates. The obtained materials have been characterized by electron and optical microscopy, nitrogen sorption and small angle X-ray scattering. The obtained hollow microcoils resemble the original hard templates in shape and size. Moreover, they have mesoporous walls (pore size ≈ 3 nm) with some domains where pores are ordered in a hexagonal array, originated from surfactant micelles. The obtained silica microcoils also show preferential adsorption of cationic fluorescent dyes. A mechanism for the formation of silica microcoils is proposed

Surface-Enhanced Resonance Raman Scattering of Rhodamine 6G in Dispersions and on Films of Confeito-Like Au Nanoparticles

Surface-enhanced resonance Raman scattering (SERRS) of rhodamine 6G was measured on confeito-like Au nanoparticles (CAuNPs). The large CAuNPs (100 nm in diameter) in aqueous dispersion systems showed stronger enhancing effect (analytical enhancement factor: over 105) of SERRS than the small CAuNPs (50 nm in diameter), while the spherical Au nanoparticles (20 nm in diameter) displayed rather weak intensities. Especially, minor bands in 1400–1600 cm−1 were uniquely enhanced by the resonance effect of CAuNPs. The enhancement factors revealed a concentration dependence of the enhancing effect at low concentration of rhodamine 6G. This dependency was due to a large capacity of hot-spots on CAuNPs, which were formed without agglomeration. The surface-enhancing behaviour in the film systems was similar to that in the dispersions, although the large CAuNPs had lower enhancing effect in the films, and the small CAuNPs and the spherical Au nanoparticles were more effective in their films. These results suggest that the CAuNPs have an advantage in ultrasensitive devices both in dispersions and films, compared to the agglomerate of spherical Au nanoparticles

Massive-exfoliation of magnetic graphene from acceptor-type GIC by long-chain alkyl amine

Graphene can be prepared from a graphite intercalation compound (GIC) with acceptor-type intercalator, FeCl3. When the FeCl3-GIC is treated with primary amines at 90 degrees C for 6 h, the GIC expands to a few layers. The expansion is further facilitated, as the alkyl chain of primary amines becomes longer, while tertiary amines cannot penetrate inside the GIC because of their structural steric hindrance. The primary amine adsorbed in the GIC is oriented to form a bilayer by an indirect reactions among FeCl3-graphene-amine, and this process plays an important role in the expansion of the GIC, in contrast to the reaction of primary amines with donor-type GICs. Then the expanded-GIC is sonicated to exfoliate the graphene sheets. The obtained material exhibited a superparamagnetic property due to the remaining iron compounds. This approach using FeCl3-GIC and primary amine is preferable for the mass production of graphene because of the mild reaction conditions and the short treatment time for exfoliation from the chemically stable FeCl3-GIC. Moreover, the magnetization of graphene nano-composites could be useful for magnetic-recovery processes, electromagnetic heating, and the other applications

A Synthetic Approach to Diverse 3-Acyltetramic Acids via <i>O</i>- to <i>C</i>-Acyl Rearrangement and Application to the Total Synthesis of Penicillenol Series

For the efficient approach to medicinally important α-branched 3-acyltetramic acids, the key reaction of <i>O</i>- to <i>C</i>- acyl rearrangement using α-amino-acid-derived 4-<i>O</i>-acyltetramic acids was extensively examined in the presence of various metal salts. Use of CaCl₂ or NaI dramatically changed the results in the reaction efficiency and rapidly brought about the desired α-branched 3-acyltetramic acids in markedly improved yields. We also discuss an epimerization at C5 stereocenter under the rearrangement conditions as well as the tolerance for structural variation at C3 and C5. In addition to the preceding success in the total synthesis of new cytotoxic tetramic acid, penicillenol A₁, this methodology could be also applied to the first total synthesis of penicillenol A₂

Self-potential studies in volcanic areas(5) : Rishiri, Kusatsu-Shirane, and White Island

We performed self-potential (SP) profiling or mapping in three volcanic fields, Rishiri (northern Hokkaido), Kusatsu-Shirane (central Honshu) and White Island (northern New Zealand). The SP profile on the western flank of Rishiri volcano showed a remarkable high in the summit side, which is similar to many other active volcanoes. Assuming a negative ζ-potential, it is likely that Rishiri volcano has a large hydrothermal circulation system, and therefore still has enough thermal energy to maintain this circulation. Kusatsu-Shirane volcano inversely showed a decreasing trend toward the summit. It is a contradictive result to the previous knowledge that a volcano with remarkable hydrothermal system shows negative SP on the top. We suspect that the low pH of ground water in this area makes ζ-potential null or positive, resulting in the reversed surface SP profile to ordinary cases. This idea should be examined by laboratory experiments in the future. In the Main Crater of White Island volcano, we found some small-scale anomalous patches associated with fumaroles and steaming ground. The small variability of SP is probably attributed to the very low resistivity of the ground. 1

Highly concentrated emulsions - a fascinating route for the preparation of carbonaceous porous materials

Trabajo presentado al 3rd International NanoFormulation 2012, celebrado en Barcelona entre el 28 de mayo y el 1 de junio de 2012

First Total Synthesis of Epicoccarine A via <i>O</i>- to <i>C</i>-Acyl Rearrangement Strategy

The first total synthesis of antibacterial epicoccarine A isolated from a fungus <i>Epicoccum</i> sp. has been accomplished in 10 steps along with synthetic elaboration of its C5-epimer, highlighting the utility of <i>O</i>- to <i>C</i>-acyl rearrangement of a 4-<i>O</i>-acyltetramic acid derivative. Comparison of spectroscopic properties and specific optical rotations of the synthetic samples with those reported for authentic material has clearly indicated the unspecified absolute stereochemistry of this natural product to be 5<i>S</i>