FMR and magnetization study of NiFe/Ag/CoNi trilayer film

The polycrystalline FeNi/Ag/CoNi asymmetric trilayer films were prepared by the UHV magnetron sputtering on silicon. In plane magnetization measurements showed double-step hysteresis loops. Magnetoresistancc (MR) measurements revealed giant magnetoresistance effect with magnitudes in 0. 15-0. 29% range at room temperature. The saturation magnetizations and the interaction between layers were studied by ferromagnetic resonance and revealed an undistinguishably weak interlayer coupling from out-of-plane geometry of measurements. The MR data are interpreted based on the incomplete domain alignment model for polycrystalline magnetic films. © 1998 IEEE

Luminescence tuning of MOFs via ligand to metal and metal to metal energy transfer by co-doping of 2∞[Gd2Cl6(bipy)3]*2bipy with europium and terbium

The series of anhydrous lanthanide chlorides LnCl3, Ln=Pr–Tb, and 4,4'-bipyridine (bipy) constitute isotypic MOFs of the formula 2∞[Ln2Cl6(bipy)3]*2bipy. The europium and terbium containing compounds both exhibit luminescence of the referring trivalent lanthanide ions, giving a red luminescence for Eu3+ and a green luminescence for Tb3+ triggered by an efficient antenna effect of the 4,4'-bipyridine linkers. Mixing of different lanthanides in one MOF structure was undertaken to investigate the potential of this MOF system for colour tuning of the luminescence. Based on the gadolinium containing compound, co-doping with different amounts of europium and terbium proves successful and yields solid solutions of the formula 2∞[Gd2-x-yEuxTbyCl6(bipy)3]*2bipy (1–8), 0≤x, y≤0.5. The series of MOFs exhibits the opportunity of tuning the emission colour in-between green and red. Depending on the atomic ratio Gd:Eu:Tb, the yellow region was covered for the first time for an oxygen/carboxylate-free MOF system. In addition to a ligand to metal energy transfer (LMET) from the lowest ligand-centered triplet state of 4,4'-bipyridine, a metal to metal energy transfer (MMET) between 4f-levels from Tb3+ to Eu3+ is as well vital for the emission colour. However, no involvement of Gd3+ in energy transfers is observed rendering it a suitable host lattice ion and connectivity centre for diluting the other two rare earth ions in the solid state. The materials retain their luminescence during activation of the MOFs for microporosity

4,4'-BIPYRIDYL - VIBRATIONAL ASSIGNMENTS AND FORCE-FIELD

A normal coordinate analysis of 4,4'-bipyridyl (4,4'-bipy) is carried out to establish consistent vibrational assignment and to determine a Urey-Bradley force field. The potential energy distribution of 4,4'-bipy is calculated which has provided certainty for the assignments. Additional information is obtained from the vibrational spectra of M (4,4'-bipy)Cl-2 complexes (where M = Zn, Cu or Cd) and calculated wave numbers of complexed 4,4'-bipy. Several vibrational modes of 4,4'-bipy in the IR and Raman spectra of the complexes are found to have upward shifts in frequency compared to those in the free molecule and the shifts are metal dependent. An explanation supported by the normal coordinate analysis is provided in terms of coupling with low frequency vibrations, particularly the M-N stretching frequencies

Supramolecular Nanostructure Formation of Coassembled Amyloid Inspired Peptides

Characterization of amyloid-like aggregates through converging approaches can yield deeper understanding of their complex self-assembly mechanisms and the nature of their strong mechanical stability, which may in turn contribute to the design of novel supramolecular peptide nano structures as functional materials. In this study, we investigated the coassembly kinetics of oppositely charged short amyloidinspired peptides (AlPs) into supramolecular nanostructures by using confocal fluorescence imaging of thioflavin T binding, turbidity assay and in situ small-angle X-ray scattering (SAXS) analysis. We showed that coassembly kinetics of the AIP nanostructures were consistent with nucleation-dependent amyloid-like aggregation, and aggregation behavior of the AlPs was affected by the initial monomer concentration and sonication. Moreover, SAXS analysis was performed to gain structural information on the size, shape, electron density, and internal organization of the coassembled AIP nanostructures. The scattering data of the coassembled AIP nanostructures were best fitted into to a combination of polydisperse core shell cylinder (PCSC) and decoupling flexible cylinder (FCPR) models, and the structural parameters were estimated based on the fitting results of the scattering data. The stability of the coassembled AIP nanostructures in both fiber organization and bulk viscoelastic properties was also revealed via temperature-dependent SAXS analysis and oscillatory rheology measurements, respectively.Wo

Qualitative Evaluation of Pyroelectric Mechanisms in Langmuir-blodgett films containing a cyclic polysiloxane substituted with aliphatic side chains using fourier transform infrared (FTIR) spectroscopy

Alternate layer Langmuir-Blodgett (LB) films containing cyclic polysiloxane substituted with aliphatic side chains alternated with monomeric eicosylamine have been shown to exhibit pyroelectric activity. The pyroelectric activity for 5, 11, 15, 21, 25 and 31 monolayer LB films, is recorded at 21 °C and shows highest activity for 5 monolayers with a pyroelectric coefficient of 0.5 μC m -2 K -1. The coefficient decreases as the thickness of the film increases from 5 to 15 monolayers, increases in the thickness range of 15-25 monolayers and decreases again for 31 monolayers film. Fourier transform infrared (FTIR) spectroscopy shows that proton transfer between the acid headgroups at the terminal end of the cyclic polysiloxane and the headgroups of the eicosylamine increases as the number of monolayer increases. However, the angle at which the molecular axis of the LB film tilts from the surface normal, α (as indicated by the overall ratio of symmetric stretching of CH 2 to CH 3, or asymmetric stretching of CH 2 to CH 3) increases as the number of monolayer increases from 5 to 15 layers and remains stable for 21-31 layers

FMR and magnetization study of NiFe/Ag/CoNi trilayer film

The polycrystalline FeNi/Ag/CoNi asymmetric trilayer films were prepared by the UHV magnetron sputtering on silicon. In plane magnetization measurements showed double-step hysteresis loops. Magnetoresistancc (MR) measurements revealed giant magnetoresistance effect with magnitudes in 0. 15-0. 29% range at room temperature. The saturation magnetizations and the interaction between layers were studied by ferromagnetic resonance and revealed an undistinguishably weak interlayer coupling from out-of-plane geometry of measurements. The MR data are interpreted based on the incomplete domain alignment model for polycrystalline magnetic films. © 1998 IEEE