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Schoonheydt R.A.,Center for Surface Chemistry and Catalysis
Chemical Society Reviews | Year: 2010

This critical review article discusses the characterization of heterogeneous catalysts by UV-VIS-NIR spectroscopy and microscopy with special emphasis on transition metal ion containing catalysts. A review is given of the transitions, that can be observed in the UV-VIS-NIR region and the peculiarities of catalytic solids that have to be taken into account. This is followed by a short discussion of the techniques that have been developed over the years: diffuse reflectance spectroscopy, UV-VIS microscopy, in situ or operando spectroscopy, the combination of UV-VIS spectroscopy with other spectroscopic techniques, with chemometrics and with quantum chemistry. In the third part of this paper four successes of UV-VIS-NIR spectroscopy and microscopy are discussed; (1) coordination of transition metal ions to surface oxygens; (2) quantitative determination of the oxidation states of transition metal ions; (3) characterization of active sites and (4) study of the distribution of transition metal ions and carbocations in catalytic bodies, particles and crystals (104 references). © 2010 The Royal Society of Chemistry. Source


Heylen S.,Center for Surface Chemistry and Catalysis | Martens J.A.,Center for Surface Chemistry and Catalysis
Angewandte Chemie - International Edition | Year: 2010

Toxic CO concentrations can be detected by a very clear induced color change of the dirhodium complex 1 (see scheme) upon binding of CO, as reported by Esteban et al. Other atmospheric compounds such as H2O, CO 2, O2, CH4, SO2, NOx, and volatile organic compounds do not interfere with the CO sensing. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Miao S.,Center for Surface Chemistry and Catalysis | Leeman H.,Center for Surface Chemistry and Catalysis | De Feyter S.,Celestijnenlaan | Schoonheydt R.A.,Center for Surface Chemistry and Catalysis
Chemistry - A European Journal | Year: 2010

The Langmuir-Blodgett (L- B) technique has been employed for the construction of hybrid films consisting of three components: surfactant, clay, and lysozyme (Lys). The surfactants are octadecylammonium chloride (ODAH) and octadecyl ester of rhodamine B (RhB18). The clays include saponite and laponite. Surface pressure versus area isotherms indicate that lysozyme is adsorbed by the surfactant- clay L-B film at the air-water interface without phase transition. The UV-visible spectra of the hybrid film ODAH- saponite-Lys show that the amount of immobilized lysozyme in the hybrid film is (1.3±0.2) ngmm-2. The average surface area (Ω) per molecule of lysozyme is approximately 18.2 nm2 in the saponite layer. For the multilayer film (ODAH-saponite-Lys)n, the average amount of lysozyme per layer is (1.0± 0.1) ngmm-2. The amount of lysozyme found in the hybrid films of ODAH-laponite- Lys is at the detection limit of about 0.4 ngmm-2. Attenuated total reflectance (ATR) FTIR spectra give evidence for clay layers, ODAH, lysozyme, and water in the hybrid film. The octadecylammonium cations are partially oxidized to the corresponding carbamate. A weak 1620 cm-1 band of lysozyme in the hybrid films is reminiscent of the presence of lysozyme aggregates. AFM reveals evidence of randomly oriented saponite layers of various sizes and shapes. Individual lysozyme molecules are not resolved, but aggregates of about 20 nm in diameter are clearly seen. Some aggregates are in contact with the clay mineral layers, others are not. These aggregates are aligned in films deposited at a surface pressure of 20 mNm-1. © 2010 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim. Source


Feyand M.,University of Kiel | Mugnaioli E.,Johannes Gutenberg University Mainz | Vermoortele F.,Center for Surface Chemistry and Catalysis | Bueken B.,Center for Surface Chemistry and Catalysis | And 5 more authors.
Angewandte Chemie - International Edition | Year: 2012

A combined approach: A permanent highly porous bismuth-containing metal-organic framework (CAU-7) has been synthesized and its structure determined by a combination of electron diffraction, Rietveld refinement, and DFT calculations. The compound is catalytically active in the hydroxymethylation of furan (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Miao S.,Center for Surface Chemistry and Catalysis | Leeman H.,Center for Surface Chemistry and Catalysis | De Feyter S.,Celestijnenlaan | Schoonheydt R.A.,Center for Surface Chemistry and Catalysis
Journal of Materials Chemistry | Year: 2010

Water-soluble protein monolayers have been prepared by spreading protein (lysozyme (Lys) and bovine serum albumin (BSA)) aqueous solutions over water and diluted clay (saponite) dispersions in a Langmuir-Blodgett (LB) trough. LB films of protein and hybrid protein-clay were prepared by vertical upstroke deposition at a desired surface pressure. Surface pressure-time (π-t) curves and surface pressure-area isotherms (π-A) indicate that the equilibrium time between the injection and compression plays an important role in forming a protein monolayer. Atomic force microscopy (AFM) suggests that heterogeneous films, consisting of regions of protein clusters and regions of saponite layers covered with protein clusters, are obtained. Both lysozyme and BSA accumulate particularly well at the edges of the saponite layers. The main difference is that the positively charged lysozyme is much more efficient in attracting negatively charged saponite layers at the air-water interface. The amount of lysozyme immobilized (nS) is 0.2-0.4 ng mm-2 for the water-lysozyme film and 0.5-0.6 ng mm-2 for the saponite-lysozyme film, as determined using UV-Vis spectroscopy. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) confirmed the presence of clay and proteins in the hybrid LB films. No significant change in the position of amide I or II bands was observed, suggesting little or no conformational changes upon immobilization of the proteins. © 2010 The Royal Society of Chemistry. Source

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