Surface Of Silica Coated Magnetite Nanoparticles Research Articles

Magnetic nanoparticles-supported dioxomolybdenum(VI) complex: An effective reusable heterogeneous nanocatalyst for the green selective sulfoxidation

A dioxomolybdenum(VI) complex with the tridentate ONO Schiff base ligand was derived from the condensation reaction of 3-ethoxysalicylaldehyde with isonicotinohydrazide and then was immobilized on the surface of silica-coated magnetite nanoparticles. The resultant organic–inorganic hybrid material was characterized by infrared spectroscopy, scanning electron microscope, energy-dispersive X-ray spectroscopy, transmission electron microscopy, vibrating sample magnetometry, and X-ray powder diffraction. The catalytic performance of the synthesized nanocatalyst was tested for the selective sulfoxidation of the different sulfides by using H2O2 as a safe oxidizing agent in ethanol as a green solvent under reflux conditions. The heterogeneous catalyst was recovered magnetically and reused at least five times without a notable decrease in its activity.

Magnetite Nanoparticles Immobilized Pectinase: Preparation, Characterization and Application for the Fruit Juices Clarification

AbstractIn this work, pectinase was immobilized on the surface of silica‐coated magnetite nanoparticles via covalent attachment. The magnetite‐immobilized enzyme was characterized by Fourier transform infrared spectroscopy, X‐ray powder diffraction, scanning electron microscopy and vibrating sample magnetometery techniques. Response Surface Methodology using Minitab Software was applied for statistical designing of operating conditions in order to immobilize pectinase on magnetic nanoparticles. The optimal conditions were obtained at 30 °C and pH 5.5 with 42.97 μl pectinase for 2 h. The immobilization yield was 50.6% at optimized conditions. Compared to the free pectinase, the immobilized pectinase was found to exhibit enhanced enzyme activity, better tolerance to the variation of pH and temperature, and improved storage stability. Both free and immobilized samples reduced the viscosity of apple juice from 1.12 to 0.88 and 0.92 mm2s−1, respectively, after 30 min at their optimum temperature. Furthermore, the immobilized enzyme could be reused six consecutive cycles and the efficiency loss in viscosity reduction was found to be only 8.16%.

Heterogenization of a molybdenum Schiff base complex as a magnetic nanocatalyst: An eco-friendly, efficient, selective and recyclable nanocatalyst for the oxidation of alkenes

Abstract A Schiff base ligand derived from 5-bromo-2-hydroxybenzaldehyde and 2,2′-dimethylpropylenediamine (H2L) and its corresponding dioxomolybdenum(VI) complex (Mo(O)2L) has been synthesized and characterized by spectroscopic methods. The adsorption of Mo(O)2L on the surface of silica-coated magnetite nanoparticles via hydrogen bonding led to the formation of (α-Fe2O3)–MCM-41–Mo(O)2L as a heterogeneous catalyst. FT-IR and atomic absorption spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize and investigate the new nanocatalyst. A practical catalytic method for the efficient and highly selective oxidation of a wide range of olefins with hydrogen peroxide and tert-butyl hydroperoxide in ethanol over the prepared molybdenum nanocatalyst was investigated. Under reflux conditions, the oxidation of cyclooctene with tert-butyl hydroperoxide or hydrogen peroxide led to the formation of epoxide as the sole product. The catalyst was reused at least six times without a significant decrease in catalytic activity or selectivity, and without detectable leaching of the catalyst.