Self-assembly of a hexagonal phase of wormlike micelles containing metal nanoclusters

Stable nanoclusters (approximately 2 nm in diameter) of copper, silver, gold, palladium, and ruthenium coated with hydrophobic coronas are easily trapped in self-assembled "soft crystal" hexagonal phase gels made of water and surfactants. The system's crystal structure and phase behavior are studied in detail. A partial phase diagram showing the hexagonal phase region for the water/SDS/toluene region is presented. High-energy X-ray scattering and cross-polarized optical microscopy experiments show that the clusters are tightly confined within the tubes. The thermal gel-fluid transitions of the hexagonal phase are investigated, and it is shown that the hexagonal phase can melt and recrystallize repeatedly. The melt/gel cycles enable easy trapping of various metal clusters in pre-prepared hexagonal phases. In contrast to spherical micelles, the hexagonal phase doped with metal clusters can grow without limit, basically up to the container walls (Ru-doped soft crystals grew to 0.5 mm over 2 months, forming wormlike tubes that are more than 50 microm long but only 7-10 nm in diameter).     

All-optical switching on a silicon chip

We present an experimental demonstration of fast all-optical switching on a silicon photonic integrated device by employing a strong light-confinement structure to enhance sensitivity to small changes in the refractive index. By use of a control light pulse with energy as low as 40 pJ, the optical transmission of the structure is modulated by more than 97% with a time response of 450 ps.     

Solvatochromism,halochromism, and preferential solvation of new dipolar guaiazulenyl 1,4-benzoquinone methides

The synthesis and the solvatochromic properties of five dyes, obtained by condensation of guaiazulene with 4-hydroxybenzaldehydes, are described. Crystal structures of a quinoid dye and a phenolic dye precursor are presented. The dyes are sensitive to the dipolarity-polarizability of the medium and to the hydrogen-bond donor ability of protic solvents. Their solvatochromism is discussed in terms of Kamlet-Taft's pi* and alpha scales, and their difference in behaviour is interpreted. Alkali and alkaline earth metal salts effect halochromism, with one exception due to extreme steric hindrance. Thus, this dye is capable of measuring solvent polarities without sensing the presence of electrolytes. Preferential solvation of the dyes in a series of binary solvent mixtures is explained quantitatively by solvent-exchange models.     

A Note on Maximal Inequality for Stochastic Convolutions

Using unitary dilations we give a very simple proof of the maximal inequality for a stochastic convolution

Alkanoylation of quinazoline by nucleophilic aromatic substitution: Combined experimental and computational study

A combined experimental and computational study on the key intermediates of NHC-catalyzed acylation reaction, Breslow intermediates (BIs), has been conducted in order to achieve a direct nucleophilic alkanoylation of N-heterocycles. Various BI precursors are alternatively prepared and used in the reaction with 4-chloroquinazoline. The present study reveals that the intermediates having benzimidazole moiety serve as acylating agents for the introduction of straight-chain alkanoyl groups. Natural bond orbital analysis indicates that the reactivity of intermediates partly correlates to the occupancy of the π_C-C bonds of the hydroxyl enamine moieties. The putative rate-determining step of the acylation reaction has been theoretically investigated. Several new 4-alkanoylquinazolines are synthesized using the BI precursors.