Thermolysis of Fe(CO)(5) and Co-2(CO)(8), dissolved in tetrahydronaphthalene, in the presence of aluminum trialkyl leads to uniform-sized Fe or Fe-Co nanoparticles, respectively. Subsequent treatment with very dilute oxygen forms a shell which protects the metallic or alloyed core of the particles against further oxidation. With the help of surfactants, for instance oleic acid or cashew nut shell liquid, the particles can be peptized in organic solvents like toluene or kerosene, resulting in magnetic fluids with extraordinary magnetic properties. The saturation of magnetization, M., of the fluids was determined by specific magnetization. The sizes and structure of the particles were investigated by transmission electron microscopy, and Moessbauer analysis showed that the core of the particles was metallic or alloyed, respectively. The particle surface termination was studied by X-ray photoelectron spectroscopy and Auger electron spectroscopy. Copyright (c) 2005 John Wiley & Sons, Ltd.

Superior enantioselectivity in the dihydroxylation of trans-stilbene catalysed by anchored triosmium carbonyl species without using a chiral modifier is observed inside sterically congested MCM-41 channels; this effect is more pronounced through the introduction of surface Al sites into the silicate.

Carbon encapsulated magnetic FeNi nanoparticle was synthesized via decompositions of methane and benzene using transmission electron spectroscopy (TEM). It was found that the performance of the encapsulation can be improved when the temperature of the carbon deposition is raised to 850 °C. The results suggests that the encapsulation process using benzene is more superior to methane at the same temperature with the weight retention a factor of 2-3 higher. The catalytic decomposition of benzene appears to be a better gaseous carbon source regarding the production graphitic encapsulated FeNi particles.

A macroscopic quantity of quasi-spherical fullerene-like shells (see Figure) that encapsulate iron nanoparticles containing radioisotope Tc-99m are prepared for the first time. The nanocomposite is acid-non-leachable, retaining radioactivity at an extremely high level. This method will enable rigorous studies of what are currently theoretical descriptions of nanometer-scale medicinal delivery vehicles for diagnostic and therapeutic purposes.

A macroscopic quantity of quasi‐spherical fullerene‐like shells (see Figure) that encapsulate iron nanoparticles containing radioisotope 99mTc are prepared for the first time. The nanocomposite is acid‐non‐leachable, retaining radioactivity at an extremely high level. This method will enable rigorous studies of what are currently theoretical descriptions of nanometer‐scale medicinal delivery vehicles for diagnostic and therapeutic purposes.

The best of both worlds: The synthesis of carbon-encapsulated iron-based magnetic nanoparticles is described. With such small catalysts that have macroscopic magnetic properties, the advantages of homogeneous or colloidal and heterogeneous catalysts can be combined.

The work presented in this paper describes a method for the preparation of supported metal catalysts on carbon matrix. Manganese used as metal catalyst was loaded onto an ion exchange resin and this precursor was calcined over a wide range of temperature between 600 and 900degreesC. The final materials consist of discrete (typically 0.5-0.8 mm diameter) spherical particles of manganese-loaded carbon. Electron microscopy was performed, which demonstrated that the structural integrity of the particles is maintained after calcination. Textural characterisation evidenced a correlation between the temperature of calcination, the specific surface area and the density of the calcined materials. The chemical moieties present, as found by XRD analysis, have been established and the catalytic activity of the material for oxidation reactions has been tested.The catalytic activity of the calcined materials was examined in the case of the oxidation of trans-stilbene to trans-stilbene oxide for different calcination temperatures. trans-Stilbene oxide and benzaldeyde were found to be the major products of the oxidation reaction. Conversions of >50%, at all pyrolysis temperatures, were achieved at 55 degreesC in 144 h. (C) 2003 Elsevier Science B.V. All rights reserved.

Metal organic chemical vapour deposition technique (MOCVD) has been used to immobilise Os species onto the internal porous structure of MCM-41. Evidence suggests that volatile Os3(CO)12 cluster reacts with surface silanol groups of the MCM-41 via an oxidative addition reaction to yield a trinuclear HOs3(CO)10(OSi) surface species. After heat treatment in air or at their very low surface coverage, these triangular sites break up to partially oxidised mononuclear surface species. In the presence of tert-butyl hydroperoxide (TBHP) as an oxidant, we demonstrate that the mononuclear species form extremely active species that catalyse the oxidation of trans-stilbene selectively to the corresponding epoxide. By carefully controlling the parameters of the MOCVD method (loading and calcination temperature), we report a new class of optimised MCM-41 porous heterogeneous catalysts carrying isolated but active Os sites for the selective oxidation of trans-stilbene in liquid phase. The reaction selectivity of the solid supported Os is apparently higher than the soluble homogeneous Os3(CO)12 cluster. It is envisaged that our solid supported catalysts not only facilitate separation from products but also offer an excellent utilisation of Os for catalysis.

Immobilised Os species prepared via chemical vapour deposition (CVD) of Os3(CO)12 onto MCM-41 are active and selective catalysts for the dihydroxylation of trans-stilbene in acetone and water, using N-methylmorpholine N-oxide as the oxidant. A detailed temperature programmed decomposition study of the solids enables to identify the active sites as Osx(CO)y surface species. The initial loading of the MCM-41 with the trinuclear precursor, as well as the temperature of the post-synthesis oxidising treatment, are found to have a significant impact on the structure/geometry of the resulting surface species, and thus their catalytic properties. We show how it is also affected by the confined environment of the MCM-41 mesopores and especially the curvature of the 30Å diameter channels. Finally, a careful study of the catalytic properties of the materials together with a study of the reactivity of the reaction products under similar conditions enable to suggest a mechanism involving the reaction of the oxidant with the osmium carbonyl surface species to form the catalytically active Os-oxo sites, and the formation of an osmoate-type species (through adsorption of the alkene onto the Os-oxo site) which subsequently reacts with the solvent to produce the diol.

Molecular organic chemical vapour deposition (MOCVD) is employed to implant various gaseous manganese precursors onto mesoporous MCM-41 silica. After heat treatment in air these samples show significantly higher catalytic activity than Mn/MCM-41 samples prepared by a conventional impregnation method for trans-stilbene epoxidation to trans-stilbene oxide using tert-butylhydroperoxide (TBHP) as an oxidant. In contrast, the same MOCVD samples gave much poorer activity than the impregnation samples in diphenylmethane oxidation reaction using air as the oxidant. Catalyst characterisation (infrared, temperature programmed reduction, EXAFS, etc.) indicates that discrete entities of Mn species (Mn-oxo and/or bridging Mn-oxygen structures, etc.) are formed on the surface of the MCM-41 by the MOCVD technique. This is attributed to initial reactions of gaseous organo-manganese complexes with surface silanol groups, followed by their oxidation in air during the heat treatment. On the other hand, in the wet impregnation samples, bulk Mn oxide phases are deposited onto the MCM-41 structure. It is thus believed that the discrete supported manganese-oxygen species of high electrophilicity are the active sites for the oxygen transfer reaction in the trans-stilbene oxidation. However, the nucleophilic lattice oxygen of the bulk Mn oxide phases prepared by the wet impregnation is responsible for the effective hydrogen abstraction in the diphenylmethane oxidation. It is also evident that the catalytic activity of the MOCVD samples depends crucially on the type of precursors used. Thus, the result clearly suggests that active and ultraselective Mn-oxygen catalytic sites for a particular oxidation reaction may be tailored through the use of different chemical precursors using the MOCVD technique.

Deposition of tin-oxygen species on mesoporous silica (MCM-41) was achieved via chemical reaction of SnEt4 vapour with surface silanol groups followed by heat treatment in air. Evidence suggested that highly reactive tin-oxygen overlayers were formed on the internal surface of the MCM-41 silica. These tin-oxygen modified silicas, after H2 pre-treatment, showed excellent activity in catalysing reduction of crotonaldehyde to crotyl alcohol using propan-2-ol as the hydrogen transfer agent (acetone was formed as the by-product). It was also found that the catalytic activity per gram of tin increased dramatically as the tin loading decreased. The increase in the specific activity with the decrease in tin loading was attributed to the improved dispersion of the tin-oxygen overlayers.

A novel MCM-41-supported Mn(III) complex with the nitrogen donor ligand 1,11-bis(2-pyridyl)-2,6,10-triazaundec-1,10-diene [MCM-41–Mn(NNNN)] shows significantly higher catalytic activity in the oxidation of cyclohexene than its Schiff base analogue [MCM-41–Mn(NNOO)] at the same surface coverage. Extended X-ray adsorption fine structure analysis indicated that at high surface coverage isolated anchored Mn complexes are maintained in the former case whereas the latter gives phenoxy-bridged oligomers on the surface of the mesoporous silica support.