Green synthesis of Cu/Fe3O4nanocomposite using Calendula extract and evaluation of its catalytic activity for chemoselective oxidation of sulfides to sulfoxides with aqueous hydrogen peroxide

Abstract

Plant mediated biogenic synthesizednanoparticles have beenquite familiar as next generation prospective catalysts. In this work, we have demonstrated copper nanoparticles (Cu NP) immobilized magnetic Fe3O4 nanoparticles using Calendula extract as a reducing and stabilizing agent. The plant extract phytochemicals initially are adorned as a protective shell over the core ferrite NPs and further reduces the incoming Cu ions following a green pathway.The physicochemical characterizations of the nanocomposite was carried out through Fourier transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM), inductively coupled plasma-optical emission spectroscopy (ICP-OES) and X-ray diffraction (XRD) study.The as synthesized material was used as a competent and magnetically isolable catalyst in the controlled and selective oxidation of different organic sulfides to sulfoxides using hydrogen peroxide as the green oxidant at room temperature. A wide spectrum of aromatic, aliphatic and heterocyclic sulfides were oxidized to their corresponding sulfoxides with excellent yields without any over oxidized product to sulfones.Due to superparamagentic character, the materialwas easily magnetically decantable and reused for 8 consecutive times with retention of its catalytic activity.