Valéria Bugris

Water Types and Their Relaxation Behavior in Partially Rehydrated CaFe-Mixed Binary Oxide Obtained from CaFe-Layered Double Hydroxide in the 155–298 K Temperature Range

Heat-treated CaFe-layered double hydroxide samples were equilibrated under conditions of various relative humidities (11%, 43% and 75%). Measurements by FT-IR and dielectric relaxation spectroscopies revealed that partial to full reconstruction of the layered structure took place. Water types taking part in the reconstruction process were identified via dielectric relaxation measurements either at 298 K or on the flash-cooled (to 155 K) samples. The dynamics of water molecules at the various positions was also studied by this method, allowing the flash-cooled samples to warm up to 298 K.

Superoxide dismutase mimicking Cu(II)-mixed amino acid complexes covalently grafted onto silica gel--an FT-IR study.

AbstractOur recent work concerning the synthesis, characterisation and testing of bioinspired electron transfer catalysts is described in this contribution. The catalysts were various Cu(II) complexes having mixed C- or N-protected amino acids (l-histidine and l-tyrosine) as ligands covalently grafted onto surface-modified silica gel. The resulting materials were structurally characterised by FT-IR spectroscopy, and their superoxide dismutase activities were tested. The covalently anchored Cu(II) complexes displayed appreciable activities in the test reaction; thus, they may be considered as promising candidates as durable electron transfer catalysts approaching the efficiency of the enzyme mimicked. FigureAlthough the active site mimicking, covalently anchored Cu-mixed amino acid complexes are less effective catalysts than the superoxide dismutase enzyme, but they can work under harsh experimental conditions as well

Water-Induced Changes in the Charge-Transport Dynamics of Titanate Nanowires

The temperature dependence of dielectric processes in humid titanate nanowires was investigated via broadband dielectric spectroscopy under quasi-isosteric conditions in the temperature range of 150-350 K. It was found that the dynamic parameters obtained from low-temperature measurements cannot describe the dielectric behavior of the system above 273 K, implying changes in the dynamics of the corresponding dielectric processes. The calculated activation energies and pre-exponential factors counterintuitively increase linearly with the amount of adsorbed water, and a compensation effect was also found to apply to all contributions in the TiONW spectra.

Carbon nanotube-layered double hydroxide nanocomposites

Preparation of multiwalled carbon nanotube-layered double hydroxide (MWCNT-LDH) nano-composites by (i) the co-precipitation of LDH components and pristine or surface-treated MWCNT or (ii) the delamination of LDH and application of the layer-by-layer technique has been attempted. For MWCNT, two types of surface treatment were used, either the surface was hydroxylated and deprotonated or wrapped in a tenside (dodecylbenzenesulfonate, DBS). LDH was delaminated by N,N-dimethylformamide. The obtained materials were characterized by X-ray diffractometry (XRD), and by scanning and transmission electron microscopies (SEM and TEM). Element distribution was mapped with help of the X-ray energy dispersive spectroscopy (XEDS) available as an extension of the scanning electron microscope. MWCNT could not be sandwiched between the layers of LDH by any of the methods employed; however, tenside-treated bundles of MWCNT could be wrapped in LDH thus forming a nanocomposite.