| 1. |
- Rusanova, Daniela, et al.
(author)
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Copper(I) O,O '-dialkyldithiophosphate clusters : EXAFS, NMR and X-ray diffraction studies
- 2007
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In: Journal of coordination chemistry (Print). - : Informa UK Limited. - 0095-8972 .- 1029-0389. ; 60:5, s. 517-525
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Journal article (peer-reviewed)abstract
- Copper K- edge EXAFS data for six polycrystalline cubic cluster compounds, {Cu-8[ S2P(OR)(2)](6)(mu(8)- S)} with R= Et, Pr-n, Pr-i, Bu-n, Bu-i and Am-i, show that the architecture of their Cu-8(S2P)(2)S cores is fairly rigid and independent of both length and branching of the alkyl chain, and that the structure of the cluster is maintained in acetone solution. Solid- state P-31 CP-MAS and static Cu-65 NMR data for {Cu-8[S2P(O-n Pr)(2)] 6(mu(8)- S)} and {Cu-8[S2P(OEt)(2)](6) mu(8)- S)} show similarities in the icosahedral O,O'- dialkyldithiophosphate shells and in the `cubic' copper cores in these cluster compounds. The crystal structure of {Cu-8[S2P(O-n Pr)(2)](6) (mu(8)- S)} was resolved using single- crystal X- ray diffraction.
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| 2. |
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| 3. |
- Fredriksson, Andreas, et al.
(author)
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Kinetics of collector adsorption on mineral surfaces
- 2006
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In: Minerals Engineering. - : Elsevier BV. - 0892-6875 .- 1872-9444. ; 19:6-8, s. 784-789
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Journal article (peer-reviewed)abstract
- In the present study infrared attenuated total reflection (IR-ATR) was used to monitor the rate of in situ adsorption of heptyl xanthate on a layer of zinc sulphide synthesized on a germanium ATR crystal. The zinc sulphide surface was characterized using X-ray photoelectron spectroscopy (XPS). The absorbance of heptyl xanthate measured increased with increasing bulk concentration of the adsorbate up to an equilibrium plateau value corresponding to a fractional coverage of the surface sites of the substrate. For the adsorption from solutions of concentrations between 10−3 and 10−5 M, the rate of adsorption increased with increasing bulk concentration. At higher concentrations the measured absorbance should be corrected for the absorbance due to the concentration of xanthate in bulk solution. The present work provides a discussion of this correction. Assuming the adsorption stage to be rate-controlling and proportional both to the concentration of the adsorbing species in solution and unreacted surface area, a rate law governing this type of transient adsorption kinetics was derived. By means of absorbance data for the concentrations 0.1 and 0.01 mM, the rate constant of adsorption was calculated. From the initial part of a Langmuir adsorption isotherm, the absorbance at monolayer coverage and the equilibrium constant of adsorption could be estimated.
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| 4. |
- Ivanov, Alexander V., et al.
(author)
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Polycrystalline and surface O,O′-dialkyldithiophosphate zinc(II) complexes : preparation, 31P CP/MAS NMR and single-crystal X-ray diffraction studies
- 2001
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In: Inorganica Chimica Acta. - 0020-1693 .- 1873-3255. ; 315:1, s. 26-35
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Journal article (peer-reviewed)abstract
- Dithiophosphate zinc(II) complexes with eight different O,O′-dialkyldithiophosphate ligands have been prepared in solid/liquid states and as surface complexes on a synthetic sphalerite, and studied by means of 31P NMR spectroscopy. All 31P resonances, corresponding to dithiophosphate ligands with different structural functions (i.e. terminal chelating or bridging between two metal atoms in bi- and tetranuclear complexes), have been assigned on the basis of comparative analyses of chemical shift data for solid complexes, their melts and chloroform solutions at various concentrations. The bridging coordination of O,O′-dialkyldithiophosphate ligands by the two neighbouring zinc(II) atoms was established in the case of zinc(II) complexes formed at the surface of the synthetic sphalerite. In addition, novel molecular and crystal structures of the binuclear O,O′-di-cyclo-hexyldithiophosphate zinc(II) complex have been resolved by single-crystal X-ray diffraction data analysis, and useful correlations with 31P NMR data for this complex were obtained.
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| 5. |
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| 6. |
- Lidström-Larsson, Margareta, et al.
(author)
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Xanthate adsorbed on ZnS studied by polarized FTIR-ATR spectroscopy
- 2000
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In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 16:21, s. 8129-8133
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Journal article (peer-reviewed)abstract
- The structure and orientation of heptylxanthate adsorbed on a ZnS surface have been studied by the FTIR-ATR technique. By using polarized light and the dichroic ratio, we found the average tilt angle to be approximately 44 degrees. The adsorbed layer studied was prepared by self-assembly from solution or by spraying the solution onto the surfaces of the ATR crystal for a short time and then rinsing with water. From the spectra we can conclude that there is a mixture of adsorbed heptylxanthate and formed diheptyldixanthogen on the ZnS surface. A bridging coordination of the adsorbed heptylxanthate is proposed.
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| 7. |
- Mohammed-Ziegler, Ildikó, et al.
(author)
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Mechanism of the adsorption process of pinosylvin and some polyhydroxybenzenes onto the structure of lignin
- 2004
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In: Vibrational Spectroscopy. - : Elsevier BV. - 0924-2031 .- 1873-3697. ; 36:1, s. 65-72
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Journal article (peer-reviewed)abstract
- The lignin Induline AT was used as model substrate to observe the adsorption of pinosylvin, trans-stilbene, pyrocatechol, resorcinol, hydroquinone, pyrogallol and phloroglucinol. Prior to adsorption the adsorbates were dissolved in diethylether. Infrared spectra of adsorbed compounds were recorded using the diffuse reflectance infrared Fourier transform (DRIFTS) technique. Far IR spectra of the adsorbed pinosylvin and polyhydroxybenzenes were used to facilitate the interpretation on the mechanism of adsorption. Vibrational analysis by quantum chemical calculations, available for most of the polyhydroxybenzenes, were utilized. The interaction between adsorbed species and lignin was found to be mainly mediated through the formation of hydrogen bonds.
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| 8. |
- Mohammed-Ziegler, Ildiko, et al.
(author)
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Surface free energy of natural and surface-modified tropical and European wood species
- 2004
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In: Journal of Adhesion Science and Technology. - : Informa UK Limited. - 0169-4243 .- 1568-5616. ; 18:6, s. 687-713
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Journal article (peer-reviewed)abstract
- To describe the wetting properties of various wood types from a practical point of view, the surface free energy of six tropical (guava, almond, teak, cloves, mango and neem) and six European wood species (English oak, Norway maple, hazel, ash, alder and Scots pine) were calculated using contact angles by the sessile-drop method. In order to provide water-repellent characteristics to the samples, they were silanized by a less used silylating reagent (using chloroform solution of trimethylsilyl N,N-dimethylcarbamate) and the results were compared with the effect of two commonly used reagents (chloroform solutions of chlorotrimethylsilane and octadecyltrichlorosilane). Since the Lifshitz-van der Waals/acid-base model is widely used in studies of biological surfaces, the energetics of the resultant wood surfaces were quantitatively described in terms of this model. For the mainly hydrophobic wood samples, anomalous surface behaviour (i.e. extremely high water contact angles (130-145°) and in certain cases unreasonably low surface free energy values) was found. Since the Lifshitz-van der Waals/acid-base model did not yield numerical results in some cases and the calculated surface free energies depended on the test liquid triplet used, the limitations in the applicability of this model are also discussed. For comparison, we analyzed our data also in terms of the Chang model.
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| 9. |
- Mohammed-Ziegler, Ildiko, et al.
(author)
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Wettability and spectroscopic characterization of silylated wood samples
- 2006
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In: Polymers for Advanced Technologies. - : Wiley. - 1042-7147 .- 1099-1581. ; 17:11-12, s. 932-939
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Journal article (peer-reviewed)abstract
- Surfaces of three European wood species (namely, English oak, Hungarian oak, and Scots pine) and two tropical wood species (namely, teak and cloves) were silylated with dichlorodimethylsilane (DDS), dichlorodiphenylsilane (DPS) and octadecyltrichlorosilane (OTS) in the first step, and with chlorotrimethylsilane (CTMS) as a monofunctional reagent in a second step. Attenuated total reflection-Fourier transform infrared (ATR-FT-IR) and electron spectroscopy for chemical analysis (ESCA) measurements were performed in order to characterize the surface composition of the treated samples. The progress of surface modification was also monitored by contact angle measurements of different test liquids (water, formamide and diiodomethane). The water contact angles were found to be in the range of 80� to 145�. The most hydrophobic surface was obtained by two-step silylation by OTS and CTMS (water contact angles were between 131� and 140�). Interestingly, the hydrophobicity of DDS-treated samples showed a significant decrease after additional silylation by CTMS. The surface free energy values were evaluated in terms of the Lifshitz-van der Waals/acid-base theory. The results obtained by the surface analytical methods (i.e. FT-IR and ESCA measurements) were compared with the contact angle data. These results suggest that in the case of DDS-treated samples, CTMS molecules substitute partly the DDS molecules, thus only physisorption of the silylating agents is supposed at room temperature.
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| 10. |
- Bo, Qi-Bing, et al.
(author)
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A new family of 3D 3d-4f heterometallic frameworks comprising 1D inorganic lanthanide ladders and organic Cu-bipyridine chains
- 2008
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In: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033 .- 1466-8033. ; 10:2, s. 232-238
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Journal article (peer-reviewed)abstract
- A new family of the 3D heterometallic coordination polymers [{Ln2(SO4)2(H2O)2(pydc)2Cu2 (bpy)2·2(H2O)}]n (Ln = Sm ( 1), Eu ( 2), Gd ( 3), Tb ( 4) and Dy ( 5); pydc = 2,6-pyridine-dicarboxylate anion; bpy= 4,4-bipyridine) have successfully been synthesized under solvothermal conditions (H2O/ethanol). All the coordination polymers obtained were characterized by elemental analysis, FT-IR analysis, differential thermal analysis/thermogravimetry (DTA/TG), fluorescent spectra and single crystal X-ray diffraction analysis. The most intriguing structural feature is that all the compounds exhibit 3D frameworks with 1D inorganic lanthanide ladders and organic CuI-bipyridine chains, which represent two types of 3d/4f coordination polymers (form I: Ln = Sm and Eu; form II: Ln = Gd, Tb and Dy) as the result of a so-called gadolinium break effect. Additionally, compounds 2 and 4 showed the characteristic emission spectra of the EuIII and TbIII ions, respectively, and appeared to have good fluorescence properties, while 1, 3 and 5 emitted fluorescence resembling CuI complexes. To our knowledge, the investigation of the
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