| 1. |
|
|
| 2. |
- Clausén, Maria, et al.
(författare)
-
Characterisation of gallium(III)-acetate complexes in aqueous solution: A potentiometric, EXAFS, IR and molecular orbital modelling study
- 2002
-
Ingår i: Journal of Chemical Society Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1472-7773 .- 1364-5447. ; , s. 2559-64
-
Tidskriftsartikel (refereegranskat)abstract
- The aqueous gallium(III)-acetate system was studied in 0.6 M Na(Cl) at 25 °C using a multi-technique approach, including potentiometry, IR spectroscopy, EXAFS spectroscopy and molecular orbital calculations. The potentiometric data were satisfactorily explained by a model which includes one mononuclear and one binuclear complex. The corresponding equilibrium constants defined according to the reactionsGa3++ HAc GaAc2++ H+2Ga3++ HAc + 2H2O Ga2(OH)2Ac3++ 3H+are log –1,1,1=–2.08 ± 0.09 and log –3,2,1=–5.65 ± 0.06, respectively. The latter complex has a stoichiometry identical to that previously identified in the aluminium(III)-acetate system. Also in agreement with this system, the IR and EXAFS data strongly indicates that this complex consists of two edge-sharing Ga octahedra bridged with an acetate ion, and should be formulated [Ga2(µ-OH)2(µ-O2CCH3)]3+. This interpretation is further supported by the molcular orbital calculations.
|
|
| 3. |
- Shchukarev, Andrey, et al.
(författare)
-
XPS study of living tree : Per Persson
- 2002
-
Ingår i: Surface and Interface Analysis. - : Wiley. - 0142-2421 .- 1096-9918. ; 34:1, s. 284-8
-
Tidskriftsartikel (refereegranskat)abstract
- X-ray photoelectron spectroscopy (XPS) was used to study the distribution of elements and main wood components (cellulose and lignin) within the wood and at the bark/wood interface of a living hybrid aspen stem. The hybrid aspen was grown upright in a greenhouse and then tilted at 45° to induce tension wood formation and upright bending of the stem. The wood between the pith and the bark on the upper side of the tilted stem was analysed. Changes in the middle lamella/S1 layer chemical composition, which corresponded to the transition from normal wood produced during upright stem growth to tension wood produced upon stem tilting, were observed. Such changes were related to the lower lignin and higher cellulose/hemicellulose contents in the tension wood. A non-uniform radial distribution of nitrogen (amino acids, proteins) within the stem was also noted. At the bark/wood interface the presence of inorganic elements (Ca, K and P) and a significant increase in nitrogen were found. The opposite wood side of the tree was enriched in lignin and fatty acids. It was shown that application of XPS imaging to a very rough surface of wood split allows the inhomogeneous lateral lignin distribution to be visualized. Copyright © 2002 John Wiley & Sons, Ltd.
|
|
| 4. |
- Sheals, Julia, et al.
(författare)
-
Adsorption of Glyphosate on Goethite: Molecular Characterization of Surface Complexes
- 2002
-
Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 36:14, s. 3090-5
-
Tidskriftsartikel (refereegranskat)abstract
- As a component of herbicides, the fate of glyphosate (PMG) in the environment is of significant interest. The nature of PMG adsorption on mineral surfaces plays a significant role in the degradation of PMG. The adsorption of PMG on goethite (-FeOOH) has been studied as a function of pH and PMG concentration. Adsorption was investigated with batch experiments, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). The N 1s line in XPS spectra showed deprotonation of the amine group of PMG (NH2+) with increasing pH. IR analyses showed no evidence for the interaction of PMG's carboxylate group with the goethite surface, while the phosphonate group formed inner-sphere complexes. There is evidence for intramolecular hydrogen bonding between NH2+ and both the carboxylate and the phosphonate groups at low pH. Intramolecular hydrogen bonding is lost when the amine group is deprotonated, and the trend in intramolecular hydrogen bonding between NH2+ and phosphonate shows that PMG adsorbs via predominantly monodentate complexation. A minor quantity of bidentate complexes is thought to form both at near-neutral pH and when the surface concentration of PMG is low. While the phosphonate group of PMG binds directly, the carboxylate group remains relatively "free" from complexation with goethite, leaving it subject to degradation and/or complexation with metal ions present in the environment.
|
|
