Concise and diversity-oriented synthesis of novel scaffolds embedded with privileged benzopyran motif

A branching DOS strategy for an unbiased natural product-like library with embedded privileged benzopyran motif was established to provide complexity and diversity of resulting heterocycles with desired drug-likeness. The importance of skeletal diversity conducted on a privileged substructure was demonstrated through the biological evaluation of a small molecule library representing 22 unique core skeletons via in vitro cytotoxicity assay.     

Synthesis of thermally stable zirconia-based mesoporous materials via a facile post-treatment

A novel method of preparing thermally stable zirconia-based mesoporous materials was developed. The zirconia-based mesoporous materials of 2D-hexagonal structure were prepared using zirconium sulfate as the zirconium precursor and cetyltrimethylammonium (CTMA) as the pore-directing agent with the aid of salt in the synthesis solution to reduce the sulfate content in the final product and significantly improve the crystallographic ordering. Post-treatment of the mesoporous material with NaCl solution and lowering the ramping rate to less than 0.2 degrees C/min during the calcination process, however, were the key steps to hinder the growth of the dense zirconia phase and to retain the ordered mesostructure up to 600 degrees C. It was found that a portion of the surfactant (8.9-17.4 wt %) and sulfate ions (0.5-1.2 wt %) were removed during the post-treatment, which prevented the remaining sulfate groups from being reduced by the hydrogen-rich surfactant during the calcination process as confirmed by sulfur K-edge X-ray absorption near edge structure (XANES) and infrared spectroscopy. The maintenance of sulfur in the sulfate state seemed to be important in stabilizing the mesoporous structure of zirconia materials. The mesoporous zirconia materials after extraction with NaCl solution three times and calcination at 550-600 degrees C had the composition ZrO(2-x)(SO4)x with x = 0.10-0.27. The material possesses high surface area (approximately 200 m2/g), large pore volume (approximately 0.10 cm3/g), and wormlike mesopores. In comparison with the mesoporous zirconia materials stabilized by chemical treatment, the present route was simpler and more environmentally friendly and resulted in mesoporous zirconia materials of better thermal stability.     

Fabrication of nanorattles with passive shell

This investigation describes the formation of a metal nanorattle with a pure metal shell by varying experimental parameters. The galvanic replacement reaction between silver and chloroauric acid was adopted to prepare hollow metal nanoparticles. This approach is extended to produce nanorattles of Au cores and Au shells by starting with Au(core)Ag(shell) nanoparticles as templates. The effect of temperature on the nanostructure of the final product is also considered. The composition of the shell in nanorattles can be controlled by varying the reaction temperature (to form pure gold or gold-silver alloy, for example). X-ray absorption fine structure spectroscopy is conducted to elucidate the fine structure of these nanoparticles. Partial alloying between the Au core and the Ag shell is observed by extended X-ray absorption fine structure (EXAFS).     

New cavitand derivatives bearing four coumarin groups as fluorescent chemosensors for Cu and recognition of dicarboxylates utilizing Cu complex

New cavitand derivatives (1, 2) bearing four coumarin groups were synthesized, and the binding properties of these cavitands towards metal ions were examined through their fluorescent changes. Cavitand 1 effectively recognized the Cu²⁺ ions among the metal ions examined. The recognition of cavitand 1-Cu²⁺ with dicarboxlyates is also described.     

Influence of 4-cyano-4'-biphenylcarboxylic acid on the orientational ordering of cyanobiphenyl liquid crystals at chemically functionalized surfaces

We report two methods that involve tailoring of the chemical composition of the nematic liquid crystal 4-cyano-4'-pentylbiphenyl to achieve control over the orientational ordering of the liquid crystal on chemically functionalized surfaces. The first method involves the direct addition of 4-cyano-4'-biphenylcarboxylic acid to 4-cyano-4'-pentylbiphenyl. The second method involves exposure of 4-cyano-4'-pentylbiphenyl to ultraviolet light and photochemical generation of a range of products, including 4-cyano-4'-biphenylcarboxylic acid. The addition of the acid or exposure to ultraviolet light accelerated the rate at which the liquid crystal exhibited an orientational transition from planar to perpendicular (homeotropic) alignment on surfaces presenting ammonium groups. The appearance of the homeotropic orientation of the UV-treated 4-cyano-4'-pentylbiphenyl on ammonium-terminated surfaces was dependent on the thickness of the film of liquid crystal (13-50 mum), consistent with a dipolar coupling between the liquid crystal and the electric field associated with an electrical double layer generated at the ammonium surface. Although the addition of 4-cyano-4'-biphenylcarboxylic acid or UV treatment of the liquid crystal also promoted homeotropic orientations on surfaces presenting hydroxyl groups, the orientations of the UV-treated liquid crystal on the hydroxyl-terminated surface did not change with thickness of the film of liquid crystal in the manner observed on the ammonium-terminated surfaces. The latter result indicates that the mechanism leading to homeotropic anchoring on hydroxyl-terminated surfaces is distinct from that on ammonium-terminated surfaces. Measurements performed using polarization modulation infrared reflection-absorption spectroscopy suggest that hydrogen bonding between the 4-cyano-4'-biphenylcarboxylic acid and the hydroxyl-terminated surface is responsible for the homeotropic anchoring on the surface. Finally, the orientation of the liquid crystal on methyl-terminated surfaces was not influenced by the addition of 4-cyano-4'-biphenylcarboxylic acid nor UV treatment. These results illustrate how the chemical composition of liquid crystals can be manipulated to achieve control over their ordering on surfaces that possess chemical functionality relevant to the development of liquid crystal-based sensors and diagnostic tools. We illustrate the utility of this approach by using the tailored liquid crystal to amplify and optically transduce the presence of proteins arrayed on ammonium-terminated surfaces.     

Laser-induced mutual transposition of the core and the shell of a Au@Pt nanosphere

The mutual transposition of the core and the shell of a Au@Pt core-shell nanosphere has been obtained by employing picosecond laser pulses to excite the surface-plasmon resonances of platinum. The thermalized energy of the plasmon resonances makes the core metal of the gold melt earlier than the shell metal of platinum because of melting temperature differences and causes the gold to soak out of the core to the surface of the nanosphere. A new reversed core/shell Pt@Au core-shell nanosphere is formed with further irradiation.     

Biphasic tautomerization dynamics of excited 7-hydroxyquinoline in reverse micelles

The excited-state tautomerization dynamics of 7-hydroxyquinoline in the water pools of reverse micelles has been investigated by monitoring time-resolved fluorescence spectra and kinetics as well as static absorption and emission spectra with a variation of water content and isotopic fractionation. The normal and the tautomeric species are found to reside preferentially in the bound- and the free-water regions of the micelles, respectively. The excited-state tautomerization of the normal species in the bound-water layers is suggested to occur via two different channels, depending on rotamers at the moment of excitation. The cis tautomerizes via proton relay from the enol group to the imino group along a hydrogen-bonded water bridge, unusual in water but common in alcohols, whereas the trans tautomerizes via the stepwise individual acid-base reactions of two prototropic groups as found in bulk water. Proton relay can take place because water in the pools has substantially reduced polarity and disrupted hydrogen-bond networks compared with bulk water.     

Femtosecond laser bonding of glasses and ion migration in the interface

We report femtosecond laser bonding with strengths of a few MPa and the material mixing during the laser bonding process by using Sm³⁺- and Cr³⁺-doped glasses and 180 fs pulses at a repetition rate of 1 kHz from an amplified Ti:sapphire laser at a wavelength of 785 nm. By analyzing fluorescence spectra taken around the interface using a confocal scanning microscope we observed the migration of Sm ions from the upper Sm-doped glass to the lower Cr-doped glass and the reduction from Sm³⁺ to Sm²⁺ ions just above the interface for the borate-borate material system. However, in Sm-doped borate-borosilicate, the laser bonding did not produce any reduction and migration of Sm³⁺ ions.     

Eu-doped B2O3–ZnO–PbO glass phosphor powders with?spherical shape and fine size prepared by spray pyrolysis

Eu-doped B₂O₃–ZnO–PbO glass phosphor powders with spherical shape and fine size were directly prepared by spray pyrolysis. The glass phosphor powders prepared at a temperature of 1100°C had broad XRD peak at around 28°. One glass phosphor powder was formed from one droplet at the preparation temperature range from 900 to 1100°C. The mean size of the glass phosphor powders was 0.75 μm. The glass transition temperature (T _g ) of the glass phosphor powders prepared by spray pyrolysis was 378.5°C. The excitation spectrum of the glass phosphor powders prepared at the optimum preparation temperature of 1100°C had bands at 362, 381, 392, 463, 525, and 532 nm. The glass phosphor powders had emission spectra with bands at 579, 614, and 653 nm. The glass phosphor powders with doping concentration of Eu of 7 wt% had the maximum photoluminescence intensity. The glass phosphor layer formed from the glass phosphor powders had high transparencies above 90%.     

POD analysis on the sphere wake at a subcritical Reynolds number

Abstract  

Flow characteristics of turbulent wake behind a sphere at a subcritical flow regime were experimentally investigated. The particle image velocimetry measurements and proper orthogonal decomposition (POD) modal analysis were employed to get detailed flow information such as the wavy structure, swirling motion and coherent structures of the sphere wake. The variation of turbulent intensities of the radial and circumferential velocity components showed the swirling motion of sphere wake in the cross-sectional planes. The relative contribution of the POD mode 1, 2 and 3 in eigenvalues was 26, 11, and 8%, respectively. The general pattern of velocity fields for the POD mode 1 in the near-wake region of x/d = 0.7–1.4 is similar with that of time-averaged mean velocity fields. In addition, the sweeping flow in the region from x/d = 1.5 to x/d = 2.0 possesses wavy structure of the sphere wake. The experimental results of the present study would contribute to the fundamental understanding of the turbulent near-wake behind a sphere.