Medium well done : Second-generation protic ionic liquids (PILs) and deep eutectic solvents (DESs) have emerged in the last decade as environmentally attractive reaction media for biocatalytic processes. These solvents are of particular interest as reaction media for biocatalytic conversions of substrates that have limited solubility in common organic solvents, such as carbohydrates, nucleosides, steroids, and polysaccharides. Chem. Eur. J. DOI: 10.1002/chem.201601940

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2006

Small ZnS particles, prepared at room temperature in an alcoholic medium using a zinc salt and thioacetamide as sulphur source, have been characterised using a suite of techniques which includes XRD, TEM and Zn K-edge EXAFS. The investigation suggests that aggregates of small sphalerite particles (cubic lattice), with average size of 3.5 nm and well-defined morphology are obtained and the particle size appears not to change with increase in the reaction time from 2 to 24 h. Zn K-edge EXAFS experiments were performed at 10 K, in order to reduce thermal disorder and the refinement of the EXAFS data resulted in very small second shell coordination numbers with respect to the bulk samples. The result is in good agreement with SEM and XRD data about the presence of nanosized particles, having a large number of surface atoms with low second shell coordination number.

High surface area graphitic carbons are of great interest in emerging applications including catalysis and energy storage because of the well-developed crystalline structure, high electronic conductivity and thermal stability, and satisfactory oxidation resistance at low temperature. We have developed the synthesis of porous graphitic carbon with a large and accessible surface area via synthesis of carboxyl-containing polymer particles, followed by ion exchange and pyrolysis at low temperature (850 degrees C). The evolution of the graphitic structure together with mesoporosity is temperature dependent, as revealed from the results of X-ray diffraction, transmission electron microscopy, and nitrogen sorption measurement. Specifically, the development of mesoporosity resulting from continuously catalyzed carbonization by the in situ formed cobalt nanoparticles can be clearly recognized. Further nitric acid oxidation leads to an increase of the pore volume due to the removal of cobalt nanoparticles and opening of closed pore entrances. Moreover, the use of silica as the isolating shell facilitates the formation of high surface area graphitic carbon. Magnetization measurements show that the graphitic carbon/cobalt composites exhibit ferromagnetic properties, and the cobalt nanoparticles are stable under air for more than 10 months without degradation of their magnetic properties.

By using laser-induced heating, we prepared Au-Ag nanoalloys via three different procedures: (i) mixture of Au nanoparticles and Ag+ ions irradiated by a 532 nm laser, (ii) mixture of Au and Ag nanoparticles irradiated by a 532 nm laser, and (iii) mixture of An and Ag nanoparticles irradiated by a 355 nm laser. Procedure i is advantageous for the production of spherical alloy nanoparticles; in procedures ii and iii, nanoalloys with a sintered structure have been obtained. The morphology of the obtained nanoalloys depends not only on the laser wavelength but also on the concentration of nanoparticles in the initial mixture. When the total concentration of Ag and Au nanoparticles in the mixture is increased, large-scale interlinked networks have been observed upon laser irradiation. It is expected that this selective heating strategy can be extended to prepare other bi- or multi-metallic nanoalloys.

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The first wet-chemical synthesis of a 13-atom platinum cluster is achieved via the decomposition of dimethyl(1,5-cyclooctadiene)platinum(II) in the presence of trialkylaluminium. Copyright © 2005 John Wiley & Sons, Ltd.

FTIR spectroscopy in transmission mode combined with a focal plane array (FPA) detector was employed for parallel characterization of Pt-containing zeolites ZSM-5 and Y. The different Pt species in the zeolite were investigated using the chemisorption of carbon monoxide. With the new transmission setup, 8-fold degree of parallelization was achieved. This significantly lowered the total time required for collection of the desired information from a set of samples. The optical setup based on FPA-IR detection provides data of high reliability. For the discussion of the individual IR band assignment, TEM analysis data are included to corroborate the conclusions.

We reported an evidence for C-C bond cleavage by milder oxidizing agent H2O2 in a mesoporous CMK-5 type carbon at room temperature.

In this study, we present a synthetic pathway for the fabrication of self-supporting zeolite monoliths consisting of crystallized nanoparticles. A resorcinol-formaldehyde-based organic aerogel is used as a template, and silicalite-1 is used as the zeolite example. The silicalite-1 monoliths obtained consist of individual well-defined zeolite nanocrystals with sizes of 30-40 nm. The monoliths exhibit a high mechanical stability and have hierarchical porosity, with micropores within the zeolite particles, a mesopore system formed by the packing of the nanoparticles, and a macropore system on the monolith level. Such monolithic zeolites show high selectivity typically above 80% to epsilon-caprolactam combined with a high rate of reaction of 0.46 g(caprolactame)/(g(catalyst).h) in the Beckmann rearrangement of cyclohexanone oxime.

Simultaneous impregnation of activated carbon with a base metal oxide precursor and a noble metal precursor with subsequent combustion of the activated carbon leads in one step to supported metal particles on very high surface area support oxides having specific surface areas of several hundred square metres per gram. For some of the noble metals (Rh, Fit) it is possible to synthesize supported particles in the size range of one to a few nanometers via this route.

In this study, a degradable, hierarchically porous silica/apatite composite material is developed from a simple low-temperature synthesis. Mesoporosity is induced in the silica portion by the use of supramolecular templating. The template is further removed by calcination. Firstly, hydroxyapatite is synthesized through a sol–gel method at near room temperature conditions. After the mineralization process, the crystal surface is coated with a mesoporous silica matrix using the templates already present in the bulk solution. The material is characterized by XRD, N2-sorption, FT–IR, SEM/EDS, and TEM. The coating layer is distributed fairly homogeneously over the apatite surface and the coating thickness is easily adjustable and dependent on the amount of added silica precursor. The hybrid material is shown to efficiently induce calcium phosphate formation under in vitro conditions and simultaneously work as a carrier system for drugs.

Journal Article Pt/C Catalysts for the Oxygen Reduction Reaction: Correlation of Carbon Support Morphology and Catalytic Activity Get access B Tesche, B Tesche Max-Planck-Institut für Kohlenforschung Search for other works by this author on: Oxford Academic Google Scholar H Schulenburg, H Schulenburg Max-Planck-Institut für Kohlenforschung Search for other works by this author on: Oxford Academic Google Scholar B Spliethoff, B Spliethoff Max-Planck-Institut für Kohlenforschung Search for other works by this author on: Oxford Academic Google Scholar M T Reetz M T Reetz Max-Planck-Institut für Kohlenforschung Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 11, Issue S02, 1 August 2005, Pages 1522–1523, https://doi.org/10.1017/S143192760550148X Published: 01 August 2005

The fabrication of carbon-shell protected cobalt nanoparticles and hollow graphitic shells has been achieved via a pyrolysis process by using monodispersed cobalt nanoparticles as a template. These materials are mesoporous and highly stable under strong acidic and basic conditions.

In this work, we present a detailed study concerning the evaluation of the metal-support interaction in high activity gold catalysts for CO oxidation. Using the colloidal deposition method, model catalysts were prepared, which allow the isolation of the effect of the support on the catalytic activity. Prefabricated gold particles were thus deposited on different support materials. Since the deposition process did not change the particle sizes of the gold particles, only the influence of the support could be studied. TiO2, Al2O3, ZrO2, and ZnO were used as support materials. Catalytic tests and high resolution transmission electron microscopy clearly show that the support contributes to the activity. However, our results are not in line with the distinction between active and passive supports based on the semiconducting properties of the oxidic material. The most active catalysts were obtained with TiO2 and Al2O3, while ZnO and ZrO2 gave substantially less active catalysts. Furthermore, the effect of other important parameters on the catalytic activity (i.e., particles size distribution, calcination temperature, and aging time for a Au/TiO2 catalyst) has also been studied. Using this preparation route, the catalysts show high-temperature stability, size dependent activity, and a very good long-term stability.

Ordered, mesoporous cobalt oxide was synthesized via a nanocasting pathway from organically modified large-pore Ia3d silica. A replica structure could be obtained,,which shows weak magnetic ordering at low temperatures due to the small size of the individual Co(3)O(4) domains forming the mesostructure.

In context of investigations of doped sodium alanate as a hydrogen storage material, an investigation combining a TEM-EDX study and XAFS measurements has been carried out on doped sodium alanate, using titanium tetrabutylate (Ti(OBun)(4)), colloidal titanium nanoparticles (Ti*) or TiCl3 as doping agents. It was found that the dehydrogenated wet-chemically Ti(OBun)(4) doped NaAlH4 consists of a crystalline Al and an amorphous NaH phase. The striking result of EDX analyses is that in each case the Ti-dopant is found to be present only in the Al phase. On the other hand, dehydrogenated NaAlH4 doped with Ti* or TiCl3 via ball milling is an amorphous material, with diffuse boundaries between Al and NaH phases and a highly uniform distribution of titanium in the Al-phase. Both the use of the ball milling doping method and of Ti* nanoparticles as dopants, are probable reasons for the outstanding kinetics of the Ti* doped material (B. Bogdanovic, M. Felderhoff, S. Kaskel, A. Pommerin, K. Schlichte and F. Schuth, Adv. Mater., 2003, 15, 1012; M. Fichtner, O. Fuhr, O. Kircher and J. Rothe, Nanotechnology, 2003, 14, 778). The course of hydrogen dis- and recharging reactions is discussed in light of the present TEM-EDX and the preceding XRD investigations of storage materials. Ti-EXAFS and XANES spectra of Ti-doped NaAlH4 after the doping, after several, and after 100 de- and rehydrogenation cycles are very close to each other. Apparently, after the Ti-doping, a zerovalent Ti species is formed which remains almost unchanged in the course of the cycle test. The XAFS spectra indicate that Ti is largely atomically dispersed in the Al phase, i.e. forms an Al-Ti alloy, thus confirming the earlier hypothesis (V.P. Balema, J.W. Wiench, K.W.M. Dennis, M. Pruski and V.K. Pecharsky, J. Alloys Compd., 2001, 329, 108; E.H. Majzoub and K.J. Gross, J. Alloys Compd., 2003, 356-357, 363) on this matter.

Nanocast silica (NCS-1) was synthesized by a casting process by employing the mesoporous carbon CMK-3 (the replica of SBA-15) as a template, tetraethoxysilane (TEOS) as the silica source, and hydrochloric acid (HCl) as the catalyst. The ordered carbon template was removed by employing different methods, such as calcination, thermal treatment followed by calcination, and controlled combustion. According to XRD and TEM characterization, NCS-1 exhibits an ordered structure with hexagonal symmetry and retains the morphology of the original SBA-15 used for the synthesis of CMK-3 over two replication steps on the nanometer scale. This demonstrates the well-connected porosity in CMK-3 type carbon, which can be used as a mold to synthesize mesostructured materials. The nitrogen adsorption isotherms generally show type IV shape, indicating mesoporous characteristics. The structure of NCS-1 is strongly influenced by variables of the nanocasting process, such as the loading amount of silica, hydrolysis temperature, and carbon removal methods. The surface area, pore size, and pore volume of NCS-1 can be tuned to a certain range by varying these parameters.

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