Binding of erbium(III) and holmium(III) to native and chemically modified alfalfa biomass: a spectroscopic investigation

Traditional treatment methods used to clean-up heavy metal contamination of soils and waters are cost intensive whereas more cost effective methods need to be developed. The use of plant materials to remediate heavy contamination has been studied for the past two decades. This technique has shown much promise for many of the common heavy metal contaminants, but few studies have focused on the lanthanide series elements. By investigating the binding and interactions of the lanthanide elements to alfalfa biomass, a more complete understanding of the binding mechanisms and the interactions of heavy metals with biomaterials can be obtained. Different chemical functional groups on the alfalfa biomass, carboxyl, amino, sulfur, and ester groups, were modified to investigate the binding mechanisms of erbium(III) and holmium(III). Batch experiments were performed with native and chemically modified alfalfa biomass suggesting that the carboxyl groups play a major role in the binding of erbium(III) and holmium(III) to the alfalfa biomass. In addition, X-ray absorption spectroscopy (XAS) studies corroborated the data obtained from the batch experiments.     

Structural studies on ruthenium(II) complexes used in interphase catalysis for the hydrogenation of ketones

Structural studies were performed on catalytically active ruthenium(II) complexes used in interphases, by means of XAFS spectroscopy. The EXAFS investigations indicate that the complexes retain their structural integrity when they are embedded on polysiloxane matrices to form stationary phase materials. The AXAFS studies reveal that the variations in the catalytic activity of the complexes with different ligands can be correlated to the differences in the electronic structure around the active ruthenium center. The EXAFS investigations show that, in asymmetric transfer hydrogenation reactions catalysed by ruthenium(II) complexes, the co‐catalyst plays a crucial role not only in enhancing the catalytic activity, but also in determining the structure of the intermediate species. Copyright © 2007 John Wiley & Sons, Ltd.     

EXAFS study of liposome-encapsulated cisplatin

The anticancer agent cisplatin encapsulated in sterically stabilized liposomes is studied with extended X-ray absorption fine structure (EXAFS) method. Analysis of local atomic structure around Pt atoms clearly indicates that the liposome-encapsulated drug is chemically stable and does not hydrolyze. Cisplatin forms a supersaturated solution in the liposome interior at a concentration about eight-fold above its aqueous solubility.     

Sonochemically synthesized core-shell structured Au–Pd nanoparticles supported on γ-Fe2O3 particles

A sample of Au–Pd bimetallic nanoparticles supported on γ-Fe₂O₃ was synthesized in a sonochemically one-pot process. The structural analyses of the synthesized sample were performed by the techniques of X-ray Absorption Fine Structure (XAFS), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and UV–vis spectrometry. Results indicated that the synthesized sample formed a core-shell structure in which a gold core was surrounded by a thin palladium shell. The reaction rate constant for the hydrogenation of cyclohexene of the present sample showed higher value than that of Pd nanoparticles supported on γ-Fe₂O₃ and core-shell structured Au–Pd nanoparticles supported on SiO₂. The present sample is a promising catalyst material which has a high catalytic activity.     

Chemical Reactivity of Tetrasulfur Tetranitride: Synthesis,Physical Properties,and Structural Characterization of the Amorphous Phase Cu7S4N4

Tetrasulfur tetranitride, S₄N₄, reacts with elemental Cu within inert solvents to a black‐blue material of approximate composition Cu₇S₄N₄ which is totally amorphous to X‐rays and which cannot be made crystalline by either thermal treatment or electron radiation. Cu₇S₄N₄ explodes if heated above 234 °C or when subjected to mechanical shock to eventually yield copper(I) sulfide; this together with the characteristic infrared spectrum of Cu₇S₄N₄ indicates the presence of molecular S₄N₄ units inside the amorphous phase. The metastable nature of Cu₇S₄N₄ is also mirrored by electron microscopy which furthermore allows the structural characterization of its degradation products. Based on experimental EXAFS data offering characteristic Cu—N and Cu—S distances, a theoretical crystalline approximant of Cu₇S₄N₄ was suggested and structurally optimized by density‐functional total‐energy calculations including periodic boundary conditions. This model incorporates a central S₄N₄ unit bonded to three shells of Cu atoms of different functionalities; in addition, a partial rupture of the S₄N₄ unit is likely to allow for a lowering of the total energy of the metastable phase. The latter observation supports the impossibility to make Cu₇S₄N₄ crystallize using ₄N₄ crystallize using whatever kind of measures.     

Distorted icosahedral Ni5Nb3Zr5 clusters in the as-quenched and hydrogenated amorphous (Ni0.6Nb0.4)0.65Zr0.35 alloys

Local structures of the hydrogenated (Ni_0.6Nb_0.4)_1-xZr_x (x = 0.3-0.4) amorphous alloys attract much attention for the sake of their epoch-making electronic transport behaviors. We investigated the local structures by XAFS for the as-quenched (Ni_0.6Nb_0.4)_0.65Zr_0.35 and hydrogenated [(Ni_0.6Nb_0.4)_0.65Zr_0.35]_0.922H_0.078 amorphous alloys, in which ballistic conductivity has been observed. XAFS results of the Ni K-edge are analyzed based on the structure model deduced by the first principle calculation. The analysis suggests that highly distorted icosahedral Ni₅Nb₃Zr₅ cluster, which has a centered-Ni and a surrounding Nb triangle, is a main structural unit of (Ni_0.6Nb_0.4)_0.65Zr_0.35 and the [(Ni_0.6Nb_0.4)_0.65Zr_0.35]_0.922H_0.078 amorphous alloys. This distorted icosahedral Ni₅Nb₃Zr₅ cluster can be associated with the occurrence of the singular electronic transport behaviors of the hydrogenated (Ni_0.6Nb_0.4)_0.65Zr_0.35 alloy.