Chemical Physics Letters (v.670, #C)

Contents (iii-vii).

The influence of pH value and composition on the microstructure, magnetic properties of Co-Fe-Al Heusler nanoparticles by F.J. Yang; J.J. Min; Z.W. Kang; S.Y. Tu; H.B. Chen; D.G. Liu; W.J. Li; X.Q. Chen; C.P. Yang (1-4).
Display OmittedCo-Fe-Al nanoparticles were synthesized by using a simple solution reduction method. The effects of pH value and atomic composition on the morphology, microstructure and magnetic properties of the prepared Co-Fe-Al nanoparticles were investigated. It was found that pure Co-Fe-Al phase with small particle size can be obtained at pH = 7.0 which have high saturation magnetization and low coercivity. Furthermore, the defects will increase with the increasing of Co composition in Co-Fe-Al nanoparticles which induce the deterioration of the B2 ordering, the abrupt decrease of magnetic moment and the abrupt increase of coercivity.
Keywords: Co-Fe-Al; Half-metallicity; Heusler alloy; Nanoparticles;

Formation of environmentally persistent free radicals (EPFRs) on ZnO at room temperature: Implications for the fundamental model of EPFR generation by Matthew C. Patterson; Mark F. DiTusa; Cheri A. McFerrin; R.L. Kurtz; Randall W. Hall; E.D. Poliakoff; P.T. Sprunger (5-10).
Display OmittedEnvironmentally persistent free radicals (EPFRs) have significant environmental and public health impacts. In this study, we demonstrate that EPFRs formed on ZnO nanoparticles provide two significant surprises. First, EPR spectroscopy shows that phenoxy radicals form readily on ZnO nanoparticles at room temperature, yielding EPR signals similar to those previously measured after 250 °C exposures. Vibrational spectroscopy supports the conclusion that phenoxy-derived species chemisorb to ZnO nanoparticles under both exposure temperatures. Second, DFT calculations indicate that electrons are transferred from ZnO to the adsorbed organic (oxidizing the Zn), the opposite direction proposed by previous descriptions of EPFR formation on metal oxides.

Power-law electrokinetic behavior as a direct probe of effective surface viscosity by Yuki Uematsu; Roland R. Netz; Douwe Jan Bonthuis (11-15).
Display OmittedAn exact solution to the Poisson-Boltzmann and Stokes equations is derived to describe the electric double layer with inhomogeneous dielectric and viscosity profiles in a lateral electric field. In the limit of strongly charged surfaces and low salinity, the electrokinetic flow magnitude follows a power law as a function of the surface charge density. Remarkably, the power-law exponent is determined by the interfacial dielectric constant and viscosity, the latter of which has eluded experimental determination. Our approach provides a novel method to extract the effective interfacial viscosity from standard electrokinetic experiments. We find good agreement between our theory and experimental data.
Keywords: Electrokinetics; Interfacial slip; Liquid-solid interface; Electric double layer;

Display OmittedThe magnetic behavior of the mixed spin-1 and spin-3/2 Ising system on a bilayer square lattice is studied using the Monte Carlo simulations for both ferromagnetic/ferromagnetic and antiferromagnetic/ferromagnetic interactions in the presence and absence of external magnetic, crystal field and for different values of exchange interactions. The thermal variations of the magnetizations are given. The magnetic hysteresis cycles are established. The magnetic coercive field and the remanent magnetization are deduced. The coercive magnetic field, remanent magnetization and the transition temperature were not affect by the size effect.
Keywords: Monte Carlo simulation; Magnetic materials; Hysteresis magnetic cycle;

Interaction of the cesium cation with meso-octamethylcalix[4]pyrrole: Experimental and theoretical study by Miroslav Polášek; Emanuel Makrlík; Jaroslav Kvíčala; Věra Křížová; Petr Vaňura (22-26).
Display OmittedBy using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the univalent cesium cation (Cs+) forms with meso-octamethylcalix[4]pyrrole (abbrev. 1) the cationic complex species 1 .Cs+. Further, applying quantum chemical DFT calculations, four different conformations of the resulting complex 1 .Cs+ were derived. It means that under the present experimental conditions, this ligand 1 can be considered as a macrocyclic receptor for the cesium cation.

Probing micro-environment of lipid droplets in a live breast cell: MCF7 and MCF10A by Catherine Ghosh; Somen Nandi; Kankan Bhattacharyya (27-31).
Display OmittedLocal environment of the lipid droplets inside the breast cancer cells, MCF7 and in non-malignant breast cells, MCF10A is monitored using time-resolved confocal microscopy. For this study, a coumarin-based dye C153 has been used. The local polarity and the solvation dynamics indicate that a cytoplasmic lipid droplet is less polar and displays slower solvation dynamics compared to the cytosol. Significant differences in terms of number of lipid droplets, polarity and solvation dynamics are observed between the cancer cell (MCF7) and its non-malignant cell (MCF10A).
Keywords: Breast cancer cells; Lipid droplets (LDs); Polarity; Solvation dynamics;

Experimental analysis of stabilizing effects of carbon nanotubes (CNTs) on thermal oxidation of poly(ethylene glycol)–CNT composites by Shogo Yamane; Seisuke Ata; Liang Chen; Hiroaki Sato; Takeo Yamada; Kenji Hata; Junji Mizukado (32-36).
Display OmittedIn this work, the thermal stabilization of poly(ethylene glycol) (PEG) by super-growth carbon nanotubes (SGCNTs) is studied by analyzing degraded compounds via high-resolution matrix-assisted laser diffusion ionization time-of-flight mass spectroscopy and IR techniques. SGCNTs successfully suppress the thermal oxidation of PEG, and the components of the degraded compounds change upon addition of SGCNTs to PEG. The SGCNTs quench mainly the RO radical generated by the initial chain scission of the C ― O bond of PEG, resulting in the suppression of the intermolecular proton abstraction.
Keywords: Thermal oxidation; Carbon nanotubes; Radical scavengers; Thermal stabilization; Poly(ethylene glycol);

Temperature dependent selectivity towards ethanol and acetone of Dy3+-doped In2O3 nanoparticles by Kanica Anand; Jasmeet Kaur; Ravi Chand Singh; Rengasamy Thangaraj (37-45).
Display OmittedIn this paper, the influence of Dy3+ doping on the sensor response (SR) and selectivity of In2O3 sensors for selective detection of ethanol and acetone has been studied. (0, 1, 5, 10%) Dy3+-doped In2O3 nanoparticles has been prepared employing a co-precipitation method and characterized by XRD, RAMAN, TEM, EDS and Photoluminescence studies. It has been observed that Dy3+ doping inhibits the nanoparticles growth and increases the lattice constant, structural disorder, activation energy, defect concentration and surface basicity. The highest SR for 10% Dy3+-doped In2O3 sensor has been ascribed to small size, high defects, high surface basicity and large lattice distortion.
Keywords: In2O3; Nanoparticles; Gas sensor; Selectivity; Dy-doping;

Controlled synthesis of β-NaGdF4 with nanosphere-, nanotube-, and nanorod-like morphology using solvents by Jiangyun Dai; Guoying Feng; Jiajia Yin; Chao Yang; Xianheng Yang; Hua Zhang; Hong Zhang; Shouhuan Zhou (46-51).
Display OmittedNaGdF4 nanocrystals with controlled shapes were synthesized in an ethylene glycol/deionized water hydrothermal reaction system. Through adjusting the solvent composition, the nanocrystals with nanosphere-, nanotube-, and nanorod-like morphology have been selectively synthesized. The change in the nucleation speed, the growth rates in different crystallographic direction and the aggregation driving forces induced different morphologies of the resulting nanocrystals. A possible mechanism of shape evolution depending on solvent composition was proposed. Photoluminescence spectra of NaGdF4:Nd3+ nanocrystals exhibited characteristic emission of Nd3+ using an excitation wavelength of 794 nm. Moreover, the nanotube-like nanocrystals exhibited the strongest fluorescence intensity and longest fluorescence decay time.
Keywords: Rare-earth-doped nanocrystals; Solvent composition; Morphology; Fluorescence;

Effect of vertical-strain-induced symmetry breaking on transport properties of zigzag graphene nanoribbons by Dongqing Zou; Wenkai Zhao; Changfeng Fang; Bin Cui; Desheng Liu (52-57).
Display OmittedUsing density functional theory combined with nonequilibrium Green’s function formalism, we investigate the transport properties of zigzag graphene nanoribbons (ZGNRs) under vertical strain. Our calculations show that localized state induced by vertical strain will inhibit the electronic transport of the systems at zero bias, but at nonzero bias, the localized state can enhance the electronic transport behavior if ZGNRs are symmetry with respect to the mid-plane between two edges. This is because the localized state produces an asymmetry electron density distribution which break the current suppression. These findings may be useful for the application of strain-induced ZGNR based molecular devices.

Display OmittedThe rotation dynamics of the spin probe TEMPO in glycerol from ESR is compared with the ortho-positronium (o-Ps) annihilation from PALS and interpreted using the relaxation dynamics from BDS. Rotation time scale within the slow motion regime exhibits two Arrhenius regions with the characteristic ESR temperature, T X1 τ, close to the characteristic PALS temperature, T b1 L, which is related to the secondary β process above T g. Next, a slow to fast motion regime transition at the characteristic ESR temperature, T c τ, close to the characteristic PALS temperature, T b2 L, followed by non-Arrhenius fast motion regime region is fully coupled with the primary α process.
Keywords: Molecular mobility; ESR; Free volume; PALS; Relaxation dynamics; BDS;

Nuclear quantum effects on adsorption of H2 and isotopologues on metal ions by Ievgeniia Savchenko; Bing Gu; Thomas Heine; Jacek Jakowski; Sophya Garashchuk (64-70).
Display OmittedThe nuclear quantum effects on the zero-point energy (ZPE), influencing adsorption of H2 and isotopologues on metal ions, are examined using normal mode analysis of ab initio electronic structure results for complexes with 17 metal cations. The lightest metallic nuclei, Li and Be, are found to be the most ‘quantum’. The largest selectivity in adsorption is predicted for Cu, Ni and Co ions. Analysis of the nuclear wavepacket dynamics on the ground state electronic potential energy surfaces (PES) performed for complexes of Li+ and Cu+2 with H2/D2/HD shows that the PES anharmonicity changes the ZPE by up to 9%.

Effect of ethanol on structures and interactions among globular proteins by Sarathi Kundu; V.K. Aswal; J. Kohlbrecher (71-76).
Fractal structure factor and two-Yukawa potential were used to explain interaction behaviours among proteins in presence of ethanol and NaCl.Display OmittedStructures and interactions among globular proteins BSA and lysozyme are explored by small angle neutron scattering (SANS) technique at pD ≈ 7.0 by varying ethanol concentration. Interaction behaviours are also obtained in presence of monovalent salt (NaCl). SANS analysis shows that for both lower and higher BSA concentrations and in presence of NaCl, combination of intermediate-range repulsion and weak long-range attraction is responsible for the effective interaction behaviours with the variation of ethanol concentration. For lysozyme, interaction nature is same as BSA in absence of NaCl but in presence of NaCl, fractal structure factor explains the interaction behaviours.
Keywords: Protein-protein interactions; BSA; Lysozyme; Ethanol; NaCl; Small angle neutron scattering;

Display OmittedAdsorption of insulin on polar and nonpolar surfaces of crystalline SiO2 (cristobalite and α -quartz) is studied using molecular dynamics simulation. Acceleration techniques are used in order to sample adsorption phase space efficiently and to identify realistic adsorption conformations. We find major differences between the polar and nonpolar surfaces. Electrostatic interactions govern the adsorption on polar surfaces and can be described by the alignment of the protein dipole with the surface dipole; hence spreading of the protein on the surface is irrelevant. On nonpolar surfaces, on the other hand, van-der-Waals interaction dominates, inducing surface spreading of the protein.
Keywords: Molecular dynamics; Protein adsorption; Insulin; Cristobalite; Quartz; Silica;

Change in hydrogen bonding structures of a hydrogel with dehydration by Ryo Naohara; Kentaro Narita; Tomoko Ikeda-Fukazawa (84-88).
Display OmittedTo investigate the mechanisms of structural changes in polymer network and water during dehydration, X-ray diffraction of poly-N,N-dimethylacrylamide (PDMAA) hydrogels was measured. The variation process in the individual structures of water and PDMAA were analyzed by decomposition of the diffraction patterns to separate the respective contributions. The results show that the short-range structures of PDMAA expand during dehydration, whereas the network structure as a whole shrinks. The average length of the hydrogen bonds between water molecules increases with the process. The present results provide a direct evidence of the structural changes of water and polymer in the hydrogel during dehydration.
Keywords: Hydrogel; Water; X-ray diffraction;

Display OmittedRoom temperature ferroelectric based on PMDI-DAP co-crystal (Tayi et al., 2012) was extensively investigated by means of abinitio DFT methodology. The study constitute geometry optimization, band structure calculations and potential energy surface scan of modeled polarization switching path of the mixed stack. Further, quantum chemical calculation of the charge-transport parameters of isolated molecular clusters are performed to rationalize the band structure results. We also comment on the viability of integrating the organic ferroelectric into non-volatile memory device in the light of calculated results.
Keywords: Organic ferroelectric; Charge transfer complex; DFT; Non-volatile memory;

Display OmittedThe rototranslational collision-induced absorption (CIA) of carbon dioxide CO2 and of carbon dioxide with inert gas mixtures CO2-He, CO2-Ar and CO2-Xe at different temperature are analyzed in terms of new isotropic intermolecular potentials and multipole-induced dipole function models, using quantum spectral lineshape computations. The irreducible spherical form for the induced operator of light absorption mechanisms was determined. The quality of the present potentials have been checked by comparing between calculated and experimental thermo-physical and transport properties over a wide temperature range. Quite a good agreement is observed for all carbon dioxide noble gas mixtures.
Keywords: CIA; Intermolecular potentials; CO2; CO2-inert gas mixtures;

Vibrational and structural relaxation of hydrated protons in Nafion membranes by Liyuan Liu; Stephan Lotze; Huib J. Bakker (102-108).
Display OmittedWe study the vibrational dynamics of the bending mode at 1730 cm−1 of proton hydration structures in Nafion membranes with polarization-resolved infrared (IR) pump-probe spectroscopy. The bending mode relaxes to an intermediate state with a time constant T1 of 170 ± 30 fs. Subsequently, the dissipated energy equilibrates with T eq of 1.5 ± 0.2 ps. The transient absorption signals show a long-living anisotropy, which indicates that for part of the excited proton hydration clusters the vibrational energy dissipation results in a local structural change, e.g. the breaking of a local hydrogen bond. This structural relaxation relaxes with a time constant of 38 ± 4 ps.