Effect of copper metal on the yield of Sc3N@C80 metallofullerenes

The yield of Sc3N@C80 metallofullerene and fullerene extract is dramatically increased via filling cored graphite rods with copper and Sc2O3 only; when compared to 100% Sc2O3 packed rods, improvements of factors of approximately 3 and approximately 5 have been achieved for Sc3N@C80 and fullerene extract produced, respectively, with the weight percent of Cu added to the rod affecting the type and amount of fullerene produced.     

Dynamic evolution in coarse-grained molecular dynamics simulations of polyethylene melts

We test a coarse-grained model assigned based on united atom simulations of C50 polyethylene to seven chain lengths ranging from C76 to C300. The prior model accurately reproduced static and dynamic properties. For the dynamics, the coarse-grained time evolution was scaled by a constant value [t=alphatCG] predictable based on the difference in intermolecular interactions. In this contribution, we show that both static and dynamic observables have continued accuracy when using the C50 coarse-grained force field for chains representing up to 300 united atoms. Pair distribution functions for the longer chain systems are unaltered, and the chain dimensions present the expected N0.5 scaling. To assess dynamic properties, we compare diffusion coefficients to experimental values and united atom simulations, assign the entanglement length using various methods, examine the applicability of the Rouse model as a function of N, and compare tube diameters extracted using a primitive path analysis to experimental values. These results show that the coarse-grained model accurately reproduces dynamic properties over a range of chain lengths, including systems that are entangled.     

Properties of Charmonium States in a Phenomenological Approach

We investigate the spectrum and decay rates of charmonium states within the framework of the non relativistic quark model by employing a Coulomb like potential from the perturbative one gluon exchange and the linear confining potential along with the potential derived from instanton vacuum to account for the hyperfine mass splitting of charmonium states in variational approach. We predict radiative E1, M1, two-photon, lepton and two-gluon decay rates of low lying charmonium states. An overall agreement is obtained with the experimental masses and decay widths.We have estimated the branching ratio of two gluons decaying into light hadrons.     

Structural and impedance properties of Ca3Nb2O8 ceramics

Polycrystalline sample of Ca₃Nb₂O₈ was prepared by a high-temperature solid-state reaction technique. X-ray diffraction (XRD) analysis confirms the formation of single-phase compound of hexagonal (rhombohedral) crystal structure at room temperature. Scanning electron micrograph of the material showed uniform grain distribution on the surface of the sample. Detailed studies of dielectric properties of the compound, studied in a wide frequency range (10²-10⁶ Hz) at different temperatures (25-500 °C), exhibit a dielectric anomaly suggesting phase transition of ferroelectric-paraelectric and structural type at 300 °C. Electrical properties of the material were analyzed using a complex impedance technique. The Nyquists plot showed the presence of bulk effect in the material in the studied temperature range. Studies of electrical conductivity over a wide temperature range suggest that the compound has negative temperature coefficient of resistance behavior.     

Rhodium(III) catalyzed oxidation of cyclic ketones by alkaline hexacyanoferrate(III)

The kinetics of the oxidation of 2-methyl cyclohexanone and cycloheptanone with Fe(CN)₆ ³⁻ catalyzed by RhCl₃ in alkaline medium was investigated at four temperatures. The rate follows direct proportionality with respect to lower concentrations of hexacyanoferrate(III) ion, but tends to become zero order at higher concentrations of the oxidant, while the reaction shows first-order kinetics with respect to hydroxide ion and cyclic ketone concentrations. The rate shows a peculiar nature with respect to RhCl₃ concentrations in that it increases with increase in catalyst at low catalyst concentrations but after reaching a maximum, further increase in concentration retards the rate. An increase in the ionic strength of the medium increases the rate, while increase in the Fe(CN)₆ ⁴⁻ concentration decreases the rate.     

Gold(I)-catalyzed sequential cycloisomerization/bis-addition of o-ethynylanilines: an efficient access to bis(indolyl)methanes and di(indolyl)indolin-2-ones

An efficient synthesis of bis(indolyl)methanes and di(indolyl)indolin-2-ones has been developed by a sequential approach involving gold(I)-catalyzed cycloisomerization/bis-addition of o-ethynylanilines with various aldehydes and isatins, respectively. This methodology opens clean and synthetically competitive alternative to the already established procedures of the synthesis of bis(indolyl)methanes and di(indolyl)indolin-2-ones.     

Ionic liquid-mediated sol–gel coatings for capillary microextraction

Ionic liquid (IL)-mediated sol–gel hybrid organic–inorganic materials present enormous potential for effective use in analytical microextraction. This opportunity, however, has not yet been explored. One obstacle to materializing this prospect arises from high viscosity of ILs significantly slowing down sol–gel reactions. In this work, we developed a method that overcomes this hurdle and provides IL-mediated advanced sol–gel materials for capillary microextraction (CME). We examined two different ILs: (a) a phosphonium-based IL, trihexyltetradecylphosphonium tetrafluoroborate, and (b) a pyridinium-based ionic liquid, N-butyl-4-methylpyridinium tetrafluoroborate. These ILs were evaluated in conjunction with two types of hydroxy-terminated polymers: (a) two Si–OH terminated polymers (PDMS and BMPO), and (b) two C–OH terminated polymers (PEG and polyTHF) that differ in their sol–gel reactivity. Scanning electron microscopy results demonstrate that ILs can serve as porogenic agents in sol–gel reactions. The IL-mediated sol–gel coatings prepared with silanol-terminated polymers provided up to 28 times higher extractions in off-line CME-GC compared to analogous sol–gel coatings prepared without any IL in the sol solution. Contrary to this, the IL-mediated sol–gel coatings prepared with C–OH terminated polymers provided lower extraction efficiencies compared to their IL-free counterparts. These observations were explained by (a) lower sol–gel reactivity of C–OH groups in PEG and polyTHF compared to Si–OH groups in PDMS and in hydrolyzed alkoxysilane precursors and (b) extremely high viscosity of ionic liquids. This study shows that IL-generated porous morphology alone is not enough to provide effective extraction media: careful choice of the organic polymer and the precursor with close sol–gel reactivity must be made to ensure effective chemical bonding of the organic polymer to the created sol–gel material to be able to provide the desired sorbent characteristics. Additionally, IL-mediated sol–gel PDMS coatings provided run-to-run RSD values of 4.2–5.0% and detection limits ranging from 3.2 ng/L to 17.4 ng/L. PDMS sol–gels prepared without ILs provided RSD values of 2.8–14.1%, and detection limits ranging from 4.9 ng/L to 487.0 ng/L.