Photochemical reduction of uranyl ion with triethylamine

Uranyl ion is photochemically reduced to uranium(IV) in the presence of triethylamine and triethylamine is oxidized to secondary amine and acetaldehyde. On the basis of product analysis, temperature independent quantum yields for uranium(IV) formation and abnormal Stern-Volmer plots rule out the simple collisional photochemical annihilation of excited uranyl ion with triethylamine. Static annihilation has a significant contribution in addition to dynamic annihilation.     

Electrostatically mediated specific adsorption of small molecules in metallo-organic frameworks

We investigate the interaction of ethylene and ethane with a Cu-tricarboxylate complex and show that at low loadings the lighter molecule has a higher binding energy as a result of an increased interaction with the framework Cu and stronger hydrogen bonding with the basic framework oxygens. This leads to selective adsorption of ethylene by a factor of about 2 at low pressure, which is overcome by the stronger van der Waals interaction of ethane at high loadings, explaining recent literature data. The results suggest the possibility of separation of light hydrocarbons at low pressures or in trace amounts.     

Optimization of slitlike carbon nanopores for storage of hythane fuel at ambient temperatures

Carbons with slitlike pores can serve as effective host materials for storage of hythane fuel, a bridge between the petrol combustion and hydrogen fuel cells. We have used grand canonical Monte Carlo simulation for the modeling of the hydrogen and methane mixture storage at 293 K and pressure of methane and hydrogen mixture up to 2 MPa. We have found that these pores serve as efficient vessels for the storage of hythane fuel near ambient temperatures and low pressures. We find that, for carbons having optimized slitlike pores of size H congruent with 7 A (pore width that can accommodate one adsorbed methane layer), and bulk hydrogen mole fraction >or=0.9, the volumetric stored energy exceeds the 2010 target of 5.4 MJ dm(-3) established by the U.S. FreedomCAR Partnership. At the same condition, the content of hydrogen in slitlike carbon pores is approximately = 7% by energy. Thus, we have obtained the composition corresponding to hythane fuel in carbon nanospaces with greatly enhanced volumetric energy in comparison to the traditional compression method. We proposed the simple system with added extra container filled with pure free/adsorbed methane for adjusting the composition of the desorbed mixture as needed during delivery. Our simulation results indicate that light slit pore carbon nanomaterials with optimized parameters are suitable filling vessels for storage of hythane fuel. The proposed simple system consisting of main vessel with physisorbed hythane fuel, and an extra container filled with pure free/adsorbed methane will be particularly suitable for combustion of hythane fuel in buses and passenger cars near ambient temperatures and low pressures.     

Study of semiconductors using solid state nuclear track detectors

Uranium trace characterization of crystalline GeS, sputtered thin films of GeS and amorphous SiH on quartz substrates, and crystalline p-type Si using the technique of solid state nuclear track detectors is reported. Concentration and distribution of uranium in these materials studied are presented. Using uranium as microprobe, it is observed that uranium prefers to be in the cleavage planes of GeS crystals. There seems to be a link between uranium concentration and the thermally induced defects in Si.     

Structure and photoelectric behavior of amorphous semiconductors in the system PbSGeSGeS2

A study of the PbS-based vitreous semiconductors: (PbS)_x(GeS)_0.7?x(GeS)_0.3 has been made. The presence of Pb atoms is found to induce structural changes in the network. These semiconductors display chemical ordering which depends upon the relative concentration of the constituent atoms. This property influences the electronic behavior of the semiconductors. For x = 0.23 the composition exhibits different features in its electrical conductivity and photoconductivity, as compared with the other compositions.     

Effect of counterion substitution on the viscosity anomaly in AOT microemulsions

AOT-based water-in-oil microemulsions display an anomalous maximum in the viscosity with X, the water to surfactant ratio. Several explanations for this phenomenon have been offered. In this work, we investigate viscosity and droplet interactions in Ca(AOT)(2)/water/n-decane and KAOT/water/n-decane microemulsions and compare our results with the commonly studied NaAOT/water/oil system. The Ca(AOT)(2) system demonstrates a maximum in relative viscosity and droplet attraction near X=15, similar to the NaAOT system, although the maximum occurs at a higher value of X in the Ca(AOT)(2) system. By contrast, the viscosity and interparticle interactions in the KAOT system do not strongly depend on the amount of water in the system. We attribute the differences in behavior between the two systems to different hydration characteristics of the counterion, and we believe that our results are consistent with a previously proposed model that attributes interdroplet attractions to charge fluctuations and surfactant exchange. Our findings support the connection between the viscosity anomaly and interparticle interactions.     

Nanoparticle-reinforced associative network hydrogels

ABA triblock copolymers in solvents selective for the midblock are known to form associative micellar gels. We have modified the structure and rheology of ABA triblock copolymer gels comprising poly(lactide)-poly(ethylene oxide)-poly(lactide) (PLA-PEO-PLA) through addition of a clay nanoparticle, laponite. Addition of laponite particles resulted in additional junction points in the gel via adsorption of the PEO corona chains onto the clay surfaces. Rheological measurements showed that this strategy led to a significant enhancement of the gel elastic modulus with small amounts of nanoparticles. Further characterization using small-angle X-ray scattering and dynamic light scattering confirmed that nanoparticles increase the intermicellar attraction and result in aggregation of PLA-PEO-PLA micelles.     

Use of zirconium(IV) and antimony(III) for structural investigation of flavonoids

Summary The absorption spectra (in the visible and ultraviolet) of the complexes formed in absolute methanol between Zr⁴⁺, V⁴⁺, Y³⁺ and Sb³⁺ with 3-hydroxyflavone, apigenin, hesperidin, naringenin, morin, kaempferol, quercetin, rutin and myricetin have been studied. Zr⁴⁺ and Sb³⁺ form complexes that are stable in acid medium. The stoichiometry of the vairous Zr⁴⁺-flavonoid complexes formed in methanol and methanol/HClO₄ media has been determined by the molar ratio method. The preferred sites for complex formation of flavonoids with Zr⁴⁺ are postulated. Zr⁴⁺ forms chelates with the 3-hydroxy-4-keto and 5-hydroxy-4-keto systems simultaneously. Sb³⁺ forms complexes only with the 3,5-dihydroxy system in flavonoids. The results permit estimation of the relative order of chelating power of each type of binding site and are useful in elucidation of the structure of the flavonoids.

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Verwendung von Zirkonium(III) und Antimon(III) für die Erforschung der Flavonoide

Zusammenfassung Die Absorptions-Spektren (im sichtbaren und UV-Bereich) der in absolutem Methanol hergestellten Komplexe von Zr⁴⁺, V⁴⁺, Y³⁺ und Sb³⁺ mit 3-Hydroxyflavon, Apigenin, Hesperidin, Naringenin, Morin, Kaempferol, Quercetin, Rutin und Myricetin wurden untersucht. Zr⁴⁺ und Sb³⁺ bilden in saurem Milieu beständige Komplexe. Die Stöchiometrie der verschiedenen Zr⁴⁺-Flavonoid-Komplexe, die in Methanol bzw. Methanol/ HClO₄ hergestellt wurden, wurde durch Bestimmung der Molarverhältnisse ermittelt. Die für die Komplexbildung bevorzugten Stellen (im Molekül) wurden angegeben. Zr⁴⁺ bildet Chelate mit der 3-Hydroxy-4-keto- und mit der 5-Hydroxy~4-ketogruppe. Sb³⁺ bildet solche Komplexe nur mit der 3,5-Dihydroxy-4-keto-Gruppe in Flavonoiden. Die Untersuchungsergebnisse ermöglichen die Abschätzung der Komplexbildungsfähigkeit der verschiedenen Gruppierungen und sind für die Strukturaufklärung von Nutzen.