Simultaneous Laser-Induced Fluorescence Imaging of Unburnt and Reacting Areas in Combustion Fields Using a KrF Excimer Laser

Simultaneous two-dimensional imaging of an unburnt area and a reacting area was performed using laser-induced fluorescence. Acetone was added to fuel as a tracer, and OH radical was used as a marker of the reacting area. A narrow band tunable KrF excimer laser (248 nm) was employed to excite acetone and OH simultaneously. Two intensified CCD cameras with different wavelength filters were used to detect these two kinds of species respectively. Detecting 294-314 nm (A-X (3, 2), etc.) for OH and 335-410 nm for acetone, we obtained images of each species without interference of a signal from the other. The method was also successfully applied to flames in a pressurized combustion chamber under the pressure of 0.5 MPa.     

Development in fission track-thermal ionization mass spectrometry for particle analysis of safeguards environmental samples

An improved method of fission track (FT) sample preparation was developed, in which the detector of fission track and the layer containing particles are separated, in order to apply the FT-thermal ionization mass spectrometry (TIMS) for particle analysis of safeguards environmental samples. The developed FT sample enabled us to detect the particle of interest simply by observing the fission tracks. The process of particle identification was difficult due to the discrepancy between the position of the particles and fission tracks, which were observed in the conventional FT sample. The proposed method has significantly resolved this problem.     

Surface pre-melting and surface flattening of Bi nanofilms on Si(1 1 1)-7 × 7

We report on the in situ observation of temperature-driven drastic morphology evolution and surface pre-melting of the Bi(0 0 1) nanofilm deposited on the Si(1 1 1)-7 × 7 surface by use of spot-profile-analyzing low-energy electron diffraction (SPA-LEED). Surface step density of the single-crystalline, epitaxial Bi(0 0 1) film decreases above 350 K in a critical manner. On annealed Bi(0 0 1) films, we have detected surface pre-melting with a transition temperature of 350 K, which yields reversible diffraction intensity drop in addition to the harmonic Debye-Waller behavior. The observed surface flattening of the as-deposited film is driven by the increased amount of mobile adatoms created through the surface pre-melting.     

Berchemolide, a novel dimeric vanillic acid glucoside from Berchemia racemosa.

A new phenol glycoside named berchemolide was isolated together with (+)-catechin and (-)-epicatechin (as acetates), from the stems of Berchemia racemosa Sieb. et Zucc. (Rhamnaceae). The structure of berchemolide, having a dimeric dilactone structure with a 22-membered ring, was determined on the basis of spectral and chemical investigations. The conformation of berchemolide was calculated by MNDO (modified neglect of diatomic overlap).     

Structure of dioctadecyl l-glutamide-derived lipid self-assembled monolayers on Au(1 1 1) surface

An l-glutamic acid-derived lipid with a terminal thiol has been synthesized and its corresponding self-assembled structure on Au(1 1 1) surfaces described. The surface morphology of the lipid self-assembled monolayer (SAM) exhibits nano-order patterning, where the height of the monolayer (approximately 1.5 nm) could be interpreted as due to the monolayer structure estimated from molecular models. The molecular orientation in the monolayer is almost perpendicular to the Au(1 1 1) surface depending on the three-point hydrogen-bonding sites in the molecule.     

Mechanism of the Aerobic Homocoupling of Phenylboronic Acid on Au20−: A DFT Study

The mechanism of the gold nanocluster‐catalyzed aerobic homocoupling of arylboronic acids has been elucidated by means of DFT calculations with Au₂₀^? as a model cluster for the Au:[poly(N‐vinylpyrrolidin‐2‐one)] catalyst. We found that oxygen affects the adsorption of phenylboronic acid and, by lowering the energy barrier, a water molecule enhances dissociation of the C?B bond, which is probably the rate‐determining step. The key role of oxygen is in activating the surface of the gold cluster by generating Lewis acidic sites for adsorption and activation of the phenylboronic acid, leading to the formation of biphenyl through a superoxo‐like species. Moreover, the oxygen adsorbed on the Au nanocluster can act as an oxidant for phenylboronic acid, giving phenol as a byproduct. As shown by NBO analysis, the basic aqueous reaction medium facilitates the reductive elimination process by weakening the Au?C bond, thereby enhancing the formation of biphenyl. The coupling of phenyl and reductive elimination of biphenyl occur at the top or facet site with low‐energy‐barrier through spillover of phenyl group on Au NC. The present findings are useful for the interpretation or design of other coupling reactions with Au NC.     

Gold/Palladium Alloy for Carbon–Halogen Bond Activation: An Unprecedented Halide Dependence

New catalytic activity of gold/palladium alloy nanoclusters (NCs) for carbon–halogen bond activation is demonstrated. In the case of an aryl chloride, the inclusion of gold in a bimetallic catalyst is indispensable to achieve the coupling reactions. Gold has the unique effect of stabilizing palladium, such that Pd²⁺ leached from clusters by means of spillover of chloride during oxidative addition. The thus‐formed spillover intermediate further reacts heterogeneously in both Ullmann and Suzuki‐type coupling reactions through a new type of mechanism. In the case of an aryl bromide, Ullmann coupling occurs through the spillover of bromide, similar to that of aryl chloride. However, a significant fraction of palladium also leached, which diminished the Ullmann coupling activity of the aryl bromide and, as a result, the order of reactivity was ArCl>ArBr. With regard to the activation of the C?Br bond towards a Suzuki‐type reaction, the inclusion of a higher gold content in gold/palladium clusters stabilized palladium to prevent the leaching of Pd²⁺ from the clusters by means of spillover of bromide. The spillover intermediate reacts heterogeneously with PhB(OH)₂, palladium‐rich gold/palladium, or pure palladium clusters; the oxidative addition of ArBr favors the extraction of palladium from the clusters, yielding Pd²⁺ intermediates. The extracted intermediates react homogenously (Pd^2+/Pd⁰ catalysis) with PhB(OH)₂, which results in the higher selectivity of the cross‐coupling product. An initial step to observe such unprecedented halide dependency, together with the dynamic behavior of palladium on the surface of gold is the oxidative addition of Ar?X. A detailed insight into the first oxidative addition process was also examined by quantum chemical calculations.     

Fluorescence ‘turn-on’ detection of Cu ions with aggregation-induced emission-active tetraphenylethene based on click chemistry

A fluorometric sensor for detection of Cu²⁺ ions in aqueous solution with aggregation-induced emission-active tetraphenylethene based on click chemistry is reported. Upon addition of Cu²⁺, a reaction of azide-modified tetraphenylethene and diethylene glycol dipropiolate in the presence of sodium ascorbate proceeded to yield covalently cross-linked networks, resulting in a dramatic enhancement of fluorescence. This assay showed high selectivity for Cu²⁺ ions even in the presence of other metal ions in a mixture.     

Fluorometric sensing of biogenic amines with aggregation-induced emission-active tetraphenylethenes

A fluorometric sensor for detection and identification of biogenic amines with carboxylic acid modified tetraphenylethenes (TPEs) based on aggregation-induced emission (AIE) is reported. A mixture of the carboxylic acid substituted TPE and biogenic amines displayed a blue emission on aggregation, which serves as a "turn-on" fluorescent sensor for the amines, the degree of fluorescence enhancement being dependent on the amine. The chromic responses were utilized to distinguish the amines. A fluorometric sensor array of three TPEs with carboxylic acid groups was shown to identify accurately 10 different amines, including biogenic amines. The response patterns were systematically classified by using linear discriminant analysis (LDA) with 98% classification accuracy. Additional information on the concentration of histamine in a "tuna fish matrix" as an example was assessed by the further analysis of the fluorescence intensity, demonstrating a test for food freshness and quality.