Self-assembled graphitic nanotubes with one-handed helical arrays of a chiral amphiphilic molecular graphene.

Self-assembly of a Gemini-shaped, chiral amphiphilic hexa-peri-hexabenzocoronene having two chiral oxyalkylene side chains, along with two lipophilic side chains, yields graphitic nanotubes with one-handed helical chirality. The nanotubes are characterized by an extremely high aspect ratio of >1,000 and have a uniform diameter of 20 nm and a wall thickness of 3 nm. The nanotubes with right- and left-handed helical senses were obtained from the (S)- and (R)-enantiomers of the amphiphile, respectively, due to an efficient translation of point chirality into supramolecular helical chirality.

Controlled self-assembly triggered by olefin metathesis: cross-linked graphitic nanotubes from an amphiphilic hexa-peri-hexabenzocoronene.

Acyclic diene metathesis (ADMET) in CH2Cl2 of a Gemini-shaped nonionic hexabenzocoronene amphiphile (2), bearing triethylene glycol chains with terminal allylic functionalities, resulted in spontaneous formation of graphitic nanotubes with a cross-linked surface. Without ADMET, 2 did not self-assemble to form a tubular structure due to a high solubility in CH2Cl2. Although 2 formed nanotubes in THF, ADMET on the surface of the preformed nanotubes in THF proceeded only sluggishly and resulted in partial disruption of the tubular structure.

Ethanol vapor-mediated maturing for the enhancement of structural regularity of hexagonal mesoporous silica films.

Structural regularity of hexagonal mesoporous silica films is dramatically enhanced when allowed to stand for a few hours in an ethanol vapor-containing closed bottle before dryness.

Tetrafluoroborate salts as site-selective promoters for sol-gel synthesis of mesoporous silica.

Tetrafluoroborate ion (BF(4)(-)) serves as a powerful and better-behaved promoter than fluoride ion (F(-)) for hydrolytic condensation of alkoxysilanes, such as tetraethoxy orthosilicate, in aqueous media containing amphiphiles with onium ion headgroups as templates, affording thermally and hydrothermally stable mesoporous silica. According to (19)F NMR spectral profiles, BF(4)(-) is localized on a positive-charged micellar surface, thereby allowing a site-selective growth of the silica framework. The resulting porous silica has an ordered hexagonal structure with a well-developed and thick silicate wall.