Nanoscale Control of Polymer Assembly on a Synthetic Catalyst-Bilayer System.

The use of the interior of self-assembled membrane as a template for polymer synthesis and assembly has long attracted the interest of chemists. However, it is difficult to utilize a lipid membrane as a chemical reactor for controlled assembly for polymers because lipid membrane is easily destabilized by loading of extraneous molecules. We found that a several-nanometer-thick bilayer vesicle made by self-assembly of an organic fullerene amphiphile doped with a metathesis catalyst serves as a nanosized chemical reactor in water, where a polymer is synthesized and assembled, depending on the affinity of the growing polymer to the organic groups on the amphiphile. This catalyst-bilayer system can thus control supramolecular assembly of the ester-functionalized polymer product into different nanoscale structures: a nanoparticle made of a single polymer chain and a nanocapsule made of several tens of polymer chains.

Cooperative Self-Assembly of Gold Nanoparticles on the Hydrophobic Surface of Vesicles in Water.

Adsorption of gold nanoparticles (NPs) on a hydrophobic fullerene bilayer vesicle ca. 30 nm in diameter occurs through cooperation of vesicle/NP and NP/NP interactions to produce a NP-vesicle hybrid whose surface is uniformly covered with the NPs separated from each other by a few nm. The vesicle coverage by NPs makes the NP-vesicle hybrid unusually stable to withstand high temperature, chromatographic purification, and high salt concentration­conditions too harsh for ordinary self-assembled vesicles, such as lipid vesicles, to survive. The hybrid serves as a platform of chemical reactions; for example, gold-catalyzed reduction of an aromatic nitro group and deposition of gold atoms for in situ growth of the NPs from 3.5 to 7.2 nm in diameter. The robust vesicle structure can be destroyed by the heat produced in interparticle plasmon coupling absorption of a 532 nm laser irradiation.

Electron microscopic observation of selective excitation of conformational change of a single organic molecule.

Atomic resolution transmission electron microscopic observations at different electron acceleration voltages enabled us to observe visually the energy relaxation process of one conformer into another via rotation of various parts of the molecule. Cross-correlation analysis of sequential transmission electron microscopy (TEM) images or of the difference between experimental and simulated TEM images has been utilized for investigation of the conformational mobility and for structure identification of conformers.