Fe 3 O 4 /HPW) was prepared by linking amino-functionalized Fe 3 O 4 nanoparticles (Fe 3 O 4 -NH 2 ) on the graphene oxide (GO), and then grafting 12tungstophosphoric acid (H 3 PW 12 O 40 ) on the graphene oxide-magnetite hybrid (GO-Fe 3 O 4 -NH 2 ). The obtained GO/Fe 3 O 4 /HPW nanocomposite was well characterized with different techniques such as FT-IR, TEM, SEM, XRD, EDX, TGA-DTA, AGFM, ICP and BET measurements. The used techniques showed that the graphene oxide layers were well prepared and the various stages of preparation of the GO/Fe 3 O 4 /HPW nanocomposites successfully completed. This new nanocomposite displayed excellent performance as a heterogeneous catalyst in the oxidation of alcohols with H 2 O 2 . The as-prepared GO/Fe 3 O 4 / HPW catalyst was more stable and recyclable at least five times without significantly reducing its catalytic activity.

No abstract

Heterogeneous magnetic nanocatalyst, Fe3O4@SiO2–Ligand–Cu (II) MNPs, reveals high catalytic performance within the synthesis of propargylamines using the multicomponent coupling reaction of aldehydes, phenylacetylene and secondary amines in water as a solvent. The substantial feature of this organic–inorganic hybrid magnetic nanocatalyst is the capability of straightforward separation of the reaction mixture by an external magnet which was retrieved ten times without significant loss of catalytic activity. This methodology has other advantages such as subordination to the principles of green chemistry and avoiding the use of expensive and harmful organic solvents. To study the stability and actual structure of birhodanine derivative–copper (II) complex, DFT calculations were also performed.

W 18 O 68 (HOSn IV OH) 3 ]$20H 2 O (1) is used as a homo-and heterogeneous catalyst for Knoevenagel condensations. New Fe 3 O 4 @SiO 2 @CH 2 (CH 2 ) 2 NH 3 + -[P 2 W 18 O 68 (HOSn IV OH) 3 ] 11À nanocatalyst was fabricated through electrostatic grafting of (1) on aminemodified silica-coated magnetic nanoparticles. The new magnetically recoverable nanocatalyst wascharacterized using infrared spectroscopy (IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffractometry (XRD), energy-dispersive X-ray analysis (EDX) and alternating gradient force magnetometry (AGFM). The results indicate that the particles are mostly spherical in shape and have an average size of approximately <30 nm. The catalytic activity of the catalyst was investigated in the selective oxidation of sulfides to sulfoxides and oxidative amination of aldehydes in an aqueous medium. The catalyst was reused at least five times without significant decrease in catalytic activities, and the structure of the catalyst remained unchanged after recycling.