One Novel Cu(II)–Amino Acid Schiff Base Complex Derived from Salicylaldehyde and L-Serine: Identification of Unusual Monodentate 4,4′-Bipyridine

One novel copper(II) complex [Cu(L)(4,4′-bipy)](ClO₄) (1), (where L: tridentate Schiff base derived from salicylaldehyde and L-serine) has been synthesised and characterised by spectroscopic and electrochemical studies. The single-crystal structure of the complex was determined. The crystal structure features the presence of [Cu(L)(4,4′-bipy)]⁺ cations and ClO₄⁻ anions aggregated by hydrogen bonding. Here, 4,4′-bipyridine functions as a monodentate ligand, which appears to be an unusual phenomenon.     

Equilibrium glassy phase in a polydisperse hard-sphere system

The phase diagram of a polydisperse hard-sphere system is examined by numerical minimization of a discretized form of the Ramakrishnan-Yussouff free-energy functional. Crystalline and glassy local minima of the free energy are located and the phase diagram in the density-polydispersity plane is mapped out by comparing the free energies of different local minima. The crystalline phase disappears and the glass becomes the equilibrium phase beyond a "terminal" value of the polydispersity. A crystal-to-glass transition is also observed as the density is increased at high polydispersity. The phase diagram obtained in our study is qualitatively similar to that of hard spheres in a quenched random potential.     

Kinetics of Forward Extraction of V(IV) in V(IV)‐SO42−(H+, Na+)‐Cyanex 301–Kerosene System Using the Lewis Cell Technique

Kinetics of the extraction of V(IV) from acidic sulfate medium by Cyanex 301 dissolved in kerosene has been investigated using a constant interfacial area stirred cell with laminar flow (Lewis cell). Reaction orders with respect to different concentration terms, rate constant, activation energy, entropy change in activation, and the enthalpy change in activation have been measured at a phase circulation speed of 3 Hz. The rate equation at 293 K is F (kmol/m²s) = 10^?7.02 (1 + 0.025[V(IV)]^?1)^?1 (1 + 398[H⁺])^?1 (1 + 0.10 [HA]_o^?1)^?1 (1 +  3.16 [SO₄^2?]). Based on the experimental results, the mechanism of extraction has been proposed.     

Influence of Nonequilibrium LO Phonons on High-frequency Performance of One-dimensional Hot Electrons in Quantum Wires of Polar Semiconductors

Small-signal ac transport of degenerate one-dimensional hot electrons in quantum wires of GaAs and In_0.53Ga_0.47As is studied for lattice temperatures of 77 K and 300 K. The carrier energy loss via polar optic phonons and momentum losses via polar optic phonons, acoustic phonons and ionized impurities are included in the calculations. Alloy disorder scattering in momentum loss is additionally incorporated for (In,Ga)As. The consideration of nonequilibrium optical phonons or hot phonons is found to enhance the 3dB cut-off frequency (f_3dB) considerably, where the ac mobility falls to 0.707 of its low frequency value. f_3dB is generally higher for (In,Ga)As quantum wire than for GaAs.     

Enhanced frequency upconversion of Sm3+ ions by elliptical Au nanoparticles in dichroic Sm3+: Au-antimony glass nanocomposites

Dichroic Sm³⁺: Au-antimony glass nanocomposites are synthesized in a new reducing glass (dielectric) matrix (mol%) K₂O–B₂O₃–Sb₂O₃ (KBS) by a single-step melt-quench technique involving selective thermochemical reduction. X-ray diffraction (XRD) and selected area electron diffraction (SAED) results indicate that Au⁰ nanoparticles are grown along the (2 0 0) plane direction. The transmission electron microscopic (TEM) image reveals the elliptical Au⁰ nanoparticles having major axis range 12–17 nm. Dichroic behavior is due to elliptical shape of Au⁰ nanoparticles of aspect ratio ～1.2. Au⁰ NPs of concentration of 0.03 wt% (4.1 × 10¹⁸ atoms/cm³) drastically enhances the intensity (～7-folds) of electric dipole ⁴G_5/2 → ⁶H_9/2 red transition (636 nm) of Sm³⁺ ions and then attenuates with further increase in Au⁰ concentration. The magnetic dipole ⁴G_5/2 → ⁶H_5/2 green (566 nm) and ⁴G_5/2 → ⁶H_7/2 orange (602 nm) transitions remain almost unaffected by presence of nano Au⁰. Local field enhancement (LFE) induced by Au⁰ SPR and energy transfer (ET) from fluorescent Au⁰ → Sm³⁺ ions are found to be responsible for the enhancement while reverse ET from Sm³⁺ → Au⁰ and optical re-absorption due to Au⁰ SPR for attenuation.     

Effects of nano-YAG (Y3Al5O12) crystallization on the structure and photoluminescence properties of Nd3+-doped K2O–SiO2–Y2O3–Al2O3 glasses

Nd³⁺-doped precursor glass in the K₂O–SiO₂–Y₂O₃–Al₂O₃ (KSYA) system was prepared by the melt-quench technique. The transparent Y₃Al₅O₁₂ (YAG) glass–ceramics were derived from this glass by a controlled crystallization process at 750 °C for 5–100 h. The formation of YAG crystal phase, size and morphology with progress of heat-treatment was examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and Fourier transformed infrared reflectance spectroscopy (FT-IRRS). The crystallite sizes obtained from XRD are found to increase with heat-treatment time and vary in the range 25–40 nm. The measured photoluminescence spectra have exhibited emission transitions of ⁴F_3/2 → ⁴I_J (J = 9/2, 11/2 and 13/2) from Nd³⁺ ions upon excitation at 829 nm. It is observed that the photoluminescence intensity and excited state lifetime of Nd³⁺ ions decrease with increase in heat-treatment time. The present study indicates that the incorporation of Nd³⁺ ions into YAG crystal lattice enhance the fluorescence performance of the glass–ceramic nanocomposites.     

Radiation-pressure acceleration of ion beams from nanofoil targets: the leaky light-sail regime

A new ion radiation-pressure acceleration regime, the "leaky light sail," is proposed which uses sub-skin-depth nanometer foils irradiated by circularly polarized laser pulses. In the regime, the foil is partially transparent, continuously leaking electrons out along with the transmitted laser field. This feature can be exploited by a multispecies nanofoil configuration to stabilize the acceleration of the light ion component, supplementing the latter with an excess of electrons leaked from those associated with the heavy ions to avoid Coulomb explosion. It is shown by 2D particle-in-cell simulations that a monoenergetic proton beam with energy 18 MeV is produced by circularly polarized lasers at intensities of just 101? W/cm2. 100 MeV proton beams are obtained by increasing the intensities to 2 × 102? W/cm2.     

Kinetics and mechanism of the ligand substitution reaction of di-μ-hydroxobis(bipyridyl)dipalladium(II) ion with thiourea in aqueous solution

The kinetics of the interaction between thiourea and the title complex has been studied spectrophotometrically in aqueous medium as a function of nucleophile concentration, temperature and pH at constant ionic strength. The reaction is a two-step process in which the first step is ligand dependent, but the second step is ligand independent and is assigned to ring closure. The rate and activation parameters, conductivity studies and IR data were used to deduce a plausible mechanism.