In recent past, magnetic catalyst has gained much attention because it can be easily separated from the reaction mixture. Herein we report a facile synthesis of magnetic carbon dot supported MnO 2 nanoparticles for the oxidative transformation of organic compounds. In the actual synthesis, initially Fe 3 O 4 nanoparticles were prepared by microwave assisted method and carbon dots were prepared instantaneously from glucose by simple incineration under closed condition. The synthesized carbon dots were coated over iron oxide nanoparticles via sonochemical deposition method. Further, magnetic carbon dot supported MnO 2 nanocomposite was synthesized by conventional homogeneous precipitation using potassium permanganate. The synthesized nanocomposite material was characterized using FT-IR, SEM, TEM, XRD and VSM techniques. The catalytic efficiency of the nanomaterial was successfully demonstrated for the oxidation of benzyl alcohols to benzaldehydes. The advantages of this method include, controlled oxidation of alcohols to aldehydes with broad substrate scope, the use of molecular oxygen as a green oxidant and beyond that a facile magnetic separation of the catalyst material. Moreover, the catalyst can be recycled for 5 times without much loss in its efficiency.

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Among phenolic pollutants, 4‐nitrophenol is a common organic pollutant readily discharged in water bodies. It causes an adverse effect on the lives of human beings and aquatic species. Therefore, it is essential to remove this pollutant from water resources. Herein, we report an eco‐friendly approach for the synthesis of silica‐coated magnetite material decorated with ultra‐fine silver nanoparticles, as a magnetically recyclable catalyst for the detoxification of 4‐nitrophenol. This synthetic strategy employs only ultrasound waves throughout the preparation of catalyst material. Further, no stabilizer was added in any of the steps involved in synthesis. Initially, iron oxide nanoparticles were synthesized from ferrous sulphate heptahydrate precursor and coated with silica matrix. Subsequently, silver nanoparticles were deposited over it. Silver was chosen among the noble metal nanoparticles, as it is abundantly available and economical and exhibits good catalytic properties. This catalyst material was well characterized using HRTEM, XRD, VSM and FTIR techniques. HRTEM studies revealed that Ag nanoparticles of size between 2 and 5 nm were dispersed over the silica‐coated magnetite. The significant merits of this approach are usage of ultrasound waves, stabilizer‐free and reduced time consumption in the synthesis of catalyst. Furthermore, a facile magnetic separation of catalyst using bar magnet is noteworthy to this method. The catalyst was successfully recycled for eight times without any significant loss in the activity. This can be a promising catalyst for the treatment of wastewater contaminated with 4‐nitrophenol.

Recently the magnetic nanoparticle earns more attention in the field of catalysis for their enhanced loading capacity and magnetic recylability. In this study, we intended to focus the synthesis of polymer coated iron oxide nanoparticle as support for the immobilization of metal nanoparticles. The typical synthetic statergy involves the synthesis of 1,4-diaminobutane functionalized superparamagnetic Fe 3 O 4 nanoparticle, followed by epoxyamine polymer coating on amine functionalised Fe 3 O 4 using 1,4 diaminobutane and epichlorohydrin monomers through one pot method. Further, ultrafine Pt nanoparticle was immobilised onto poly (epoxyamine) coated Fe 3 O 4 . These materials were characterized using FT-IR, XRD, VSM, EDS, SEM HRTEM etc. The semiheterogenous catalytic efficiency of the material was examined in aqueous phase reduction of p-nitrophenol. The catalyst was reused up to 5 times without loss of activity. Graphic abstractKeywords Magnetite · Poly (epoxy amine) · Nanocomposite · Platinum nanoparticle · Immobilization · p-nitrophenol

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