Stability analysis of zinc oxide-nanoencapsulated conjugated linoleic acid and gamma-linolenic acid.

Conjugated linoleic acid (CLA) and gamma-linolenic acid (GLA) were encapsulated with hydrated zinc oxide nanoparticles in an effort to improve their time and thermal stability. Encapsulated and nonencapsulated CLA and GLA were stored at 20, 30, 40, and 50 degrees C for 49 d. At various time points, encapsulated CLA and GLA were extracted, methylated, and analyzed using GC-FID. Both encapsulated CLA and control CLA were stable when stored at 20, 30, and 40 degrees C for up to 49 d. However, control CLA was 100% degraded after 28 d at 50 degrees C, whereas encapsulated CLA was stable at 50 degrees C for 49 d. Similarly, both encapsulated GLA and control GLA were stable when stored at 20 degrees C for 49 d, but nonencapsulated GLA was 92% degraded after 49 d at 30 degrees C; encapsulated GLA was stable at 30 degrees C. Therefore, nanoencapsulation improves the time and temperature stability of CLA and GLA.

Co K-edge XAS study on a new cobalt-doped-SiO2 pillared clay.

New Co-doped-SiO2-sol pillared montmorillonite has been synthesized by interlayer hydrolysis and condensation of tetraethylorthosilicate (TEOS) in the presence of Co2+ ion using an organic template. The Co K-edge XANES and EXAFS analyses for the CoO-SiO2-PILC (before and after calcination) and for the references such as CoO and Co(OH)2 were performed in order to obtain electronic and local structural information of cobalt species, which may act as a catalytic active site for the selective reduction of NO(x), hydrodesulfurization, and Fischer-Tropsch reaction. According to the XANES spectra, the divalent cobalt ion is stabilized in an octahedral symmetry. The EXAFS result shows a significant change in local symmetry around cobalt ion upon calcination. The EXAFS fitting result before calcination shows that the cobalt species is in the form of hydroxide, with a small number of (Co-Co) pairs compared to the bulk Co(OH)2. After calcining at 550 degrees C, the first nearest neighbours were fitted to six oxygen atoms with two different distances, and the second and the third neighbours were fitted to two Si and one Co atoms. It is, therefore, reasonable to suggest a structure model, where the cobalt species on the SiO2 sol exists as a nano cluster of Co(OH)2 before calcination but transforms to a nanosized cobalt oxide covalently bound to the surface of SiO2 pillar after calcination.

4d Electronic structure analysis of ruthenium in the perovskite oxides by Ru K- and L-edge XAS.

The 4d electronic structure of ruthenium in the perovskite oxides, La2MRuIVO6 (M = Zn, Mg, and Li) and Ba2YRuVO6, has been investigated by the Ru K-and L-edge XANES and EXAFS analyses. Such X-ray absorption spectroscopic results clarify that the RuIV (d4) and RuV (d3) ions are stabilized in nearly regular Oh site. Comparing the Ru L-edge XANES spectra of perovskites containing isovalent ruthenium, it has been found that the t2g state is mainly influenced by A site cation, whereas the eg is mainly affected by neighboring B site cation. The experimental EXAFS spectra in the range of R < or = approximately 4.5 A are well reproduced by ab-initio calculation based on crystallographic data, which supports the long-range structure presented by Rietveld refinement.

Local structure analysis of Ti species stabilized in ion exchangeable layer solids by x-ray absorption spectroscopy.

Nano-sized titanium dioxides are incorporated into the interlayer spaces of ion-exchangeable layered perovskites, H(1-x)Ca2(x)La(x)Nb3O10 (x=0.0-0.75), by replacing the interlayer protons with positively charged TiO2 nano-sol particles or basic titanium glycolate complex (titanatrane). Powder X-ray diffraction analysis. UV-Vis absorption spectroscopy, thermogravimetric analysis, and N2 adsorption-desorption isotherm measurements show that quantum sized TiO2 particles are stabilized in between perovskite lattices to form micropores (S(BET) = 37-110 m2/g). X-ray absorption spectroscopy at the Ti K-edge was used for investigating the local environment around Ti atoms constituting the interlayer pillars. According to the XANES spectra, the 'as-pillared' Ti species have the same local environments with those of precursory species, which subsequently converted into TiO2 clusters with rutile and anatase-like local structures when TiO2 nano-sol particles and titanatrane are used as pillaring species. respectively. It is also found that the local environment of TiO2 remains almost constant irrespective of the layer charge density, while the TiO2 pillar content and the microporosity increase with the latter.

In situ XAFS study at the Zr K-edge for SiO2/ZrO2 nano-sol.

The structural characterisation of SiO2/ZrO2 nano-sol particles, prepared by mixing SiO2 sol and aqueous solution of ZrOCl2 8H2O, has been carried out by in-situ XAS measurement at the Zr K-edge during condensation reaction. The detailed XANES features at the Zr K-edge of the mixed sol of SiO2/ZrO2 are compared with those of other references such as ZrO2, ZrOCl2 8H2O. BaZrO3, and ZrSiO4, and it becomes obvious that the Zr4+ ions are stabilised in an octahedral symmetry. The EXAFS result also indicates that each Zr atom is coordinated with six oxygen ones as the first nearest neighbour, where two oxygen atoms are from the linkage of (Si-O-Zr) at short distance, and four ones are from water molecules at long distance. As the condensation reaction proceeds, it is found that the number of oxygen atoms due to the formation of (Si-O-Zr) bond at short distance and the second neighbour of silicon atoms increase simultaneously. From the above EXAFS and XANES results, the structural and gelating models could be proposed, which is based on the octahedrally coordinated but distorted zirconium species attaching on the SiO2 sol surface.

O K and Cu LIII edge study of itinerant holes in I2-, Hgl2- and HgBr2- intercalated BSCCO(2212) single crystals.

Intercalation effect on BSCCO (2212) system, although it increases the interlayer distance and the c-axis remarkably, produces only a small change in the transition temperature. Thus, amongst other things, intercalation provides an effective method to investigate the influence of the interblock coupling. Electrons are transferred from the host Cu-O2 layers to the guest molecules I2, HgBr2, HgI2 leading to evolution of the Tc. For this we have made high resolution XANES study on the O K and Cu L3 edges to estimate the density of the doping holes. We attempt on basis of our and earlier results the evolution of Tc in these as also the much larger decrease produced in Tc for I2-intercalation for which the increase in basal spacing is the smallest of the three halides.

Polarization-dependent XANES study of Bi2Sr2Ca(1-x)Pr(x)Cu2O8-delta insulating single crystal.

Pr doping has been extensively studied in cuprate superconductors to understand the mechanism of quenching of superconductivity in cuprate perovskites. Experience has revealed that it acts differently in different cuprate perovskites. We have made high resolution polarization XANES measurements on a Pr-doped single crystal within the ab-plane on the Cu K and Pr L III absorption edges to ascertain the valence state of Pr cation and thereby try learning how it is quenching superconductivity in the present case. Our results show that besides the Pr quenching holes the possibility of its localizing some holes through hybridization with O 2p and Cu 3d cannot be ruled out.