Growth and characterization of Mn- and Co-doped ZnO nanowires

A flow injection chemiluminescence method is proposed for the determination of cobalt, based on the strong catalytic effect of Cobalt(II) (1,10-phenanthroline)₃ complex on the lucigenin-periodate reaction in alkaline medium. Under the optimum experimental conditions, the chemiluminescence signal responded linearly to the concentration of cobalt(II) in the 1.0 × 10⁻⁹–3.0 × 10⁻⁷ g mL⁻¹ range with a detection limit of 4.4 × 10⁻¹⁰ g mL⁻¹ cobalt(II). The relative standard deviation for the determination of 5.0 × 10⁻⁸ g mL⁻¹ of cobalt was 2.3% in eleven replicated measurements. The method was successfully applied to the determination of cobalt(II) in pharmaceutical preparations.     

Living free radical donor-acceptor copolymerization of styrene and N-cyclohexylmaleimide and the synthesis of poly[styrene-co-(N-cyclohexylmaleimide)]/polystyrene block copolymers

Styrene/N-cyclohexylmaleimide copolymers with small polydispersities and controlled molecular weights were synthesized by a free radical copolymerization using an iniferter system consisting of benzoyl peroxide and 2,2,6,6-tetramethylpiperidine-N-oxyl. Due to the interactions of the electropositive (styrene) and electronegative (N-cyclohexylmaleimide) monomers the brutto polymerization rates are higher than for other living polymerizations initiated with the same iniferter system. The prepared copolymers were used as macroiniferters for bulk polymerization of styrene.     

Low molecular weight organogelators derived from threefold symmetric tricarbamates

A group of new low molecular weight organogelators based on threefold symmetric tricarbamate were synthesized and characterized. The tricarbamates with long alkyl chains were able to gelate a wide range of polar and nonpolar organic solvents such as acetonitrile and cyclohexane, generally at concentrations lower than 20 g/L. The best organogel formation was obtained using a threefold symmetric tricarbamate in n-dodecane, in which a sufficiently transparent gel was formed at the critical gelation concentration 1 g/L. Intermolecular hydrogen bonding by the tricarbamate in a nonpolar solvent benzene-d₆ was indicated by ¹H NMR spectra. Its maximum UV absorption was 11 nm higher in chloroform than in n-dodecane, and this red shift indicated increased conjugation between the benzene core and the carbamate substituents, which confirmed a change in its conformation from nonpolar to polar solvent. The self-assembling behavior of the tricarbamate in dilute solutions was investigated by TEM. Fiber-like networks were observed in a large range of solution concentrations.     

The electric field gradient in Cd1−xMgx for 0⩽x⩽0.15 measured by perturbed angular correlations

The dependence of the electric field gradient q in Cd_1?xMg_x on the axial ratio of the hcp unit cell yields the coefficient (? ln q/? ln (c/a))_V=+6.2(1.0) at x=0 in fair agreement with a point charge calculation.     

Dynamical Phase Transition for a Quantum Particle Source

We analyze the time evolution describing a quantum source for non-interacting particles, either bosons or fermions. The growth behavior of the particle number (trace of the density matrix) is investigated, leading to spectral criteria for sublinear or linear growth in the fermionic case, but also establishing the possibility of exponential growth for bosons. We further study the local convergence of the density matrix in the long time limit and prove the semi-classical limit.     

Nuclear quadrupole interaction at133Ba (EC)133Cs in Eu1Ba2Cu3O7−°

We studied the nuclear quadrupole interaction (NQI) at¹³³Ba(EC)¹³³Cs in Eu₁Ba₂Cu₃O_7–6 by time differential perturbed angular correlation between 11 K and 300 K. No anomalies in the NQI parameters around T_c were detected. All Ba sites appear to be identical and the precession frequency is ω=80(2) Mrad/s (assuming axial symmetry), independent of temperature.     

Nuclear quadrupole interaction of119mHg in mercury(I) and mercury(II) halides

The nuclear quadrupole interactions of^199mHg in the mercury(I) and mercury(II) halides with Cl, Br, I were determined by time differential perturbed angular correlation. The quadrupole moment of theI=5/2 state in¹⁹⁹Hg was redetermined to beQ _5/2=0.674(77) b. The nuclear quadrupole interaction in both mercurous and mercuric halides scales with the electronegativity. Electric field gradients at mercury and halogen sites were calculated by a full-potential linearized augmented plane wave method (WIEN code) and were found in good agreement with experiment. In some cases a total energy minimization for internal parameters was carried out and found to be essential.