Bimetallic Ag–Cu alloy nanoparticles were obtained via a simple co-reduction method, which exhibited significantly improved activity for the synthesis of β-enaminones and β-enaminoesters compared with their monometallic counterparts.

A facile, efficient and environmentally-friendly protocol for the synthesis of xanthenes by graphene oxide based nanocomposite (GO-CuFe2O4) has been developed by one-pot condensation route. The nanocomposite was designed by decorating copper ferrite nanoparticles on graphene oxide (GO) surface via a solution combustion route without the use of template. The as-synthesized GO-CuFe2O4 composite was comprehensively characterized by XRD, FTIR, Raman, SEM, EDX, HRTEM with EDS mapping, XPS, N2 adsorption-desorption and ICP-OES techniques. This nanocomposite was then used in an operationally simple, cost effective, efficient and environmentally benign synthesis of 14H-dibenzo xanthene under solvent free condition. The present approach offers several advantages such as short reaction times, high yields, easy purification, a cleaner reaction, ease of recovery and reusability of the catalyst by a magnetic field. Based upon various controlled reaction results, a possible mechanism for xanthene synthesis over GO-CuFe2O4 catalyst was proposed. The superior catalytic activity of the GO-CuFe2O4 nanocomposite can be attributed to the synergistic interaction between GO and CuFe2O4 nanoparticles, high surface area and presence of small sized CuFe2O4 NPs. This versatile GO-CuFe2O4 nanocomposite synthesized via combustion method holds great promise for applications in wide range of industrially important catalytic reactions.

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A graphene oxide (GO)-SnO 2 -based nanocomposite was synthesized by decorating the graphene oxide surface with SnO 2 nanoparticles via a solvothermal process. The nanocomposite was characterized using Fourier transform infrared spectra (FTIR), FT-Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field-emission Scanning electron microscopy (FE-SEM), Energy dispersive X-ray spectroscopy (EDS), Transmission electron microscopy (TEM) and N 2 adsorption/ desorption study. The FE-SEM and TEM images demonstrate the uniform distribution of the SnO 2 nanoparticles on the GO surface and high-resolution transmission electron microscopy (HRTEM) confirms an average particle size of 8-12 nm. The GO-SnO 2 nanocomposite has been found to be an extremely efficient catalyst for the synthesis of b-enaminones and b-enaminoesters in methanol solvent and also, in solventless conditions. The GO-SnO 2 nanocomposites exhibited synergistically more superior catalytic efficiency compared to pure graphene oxide and SnO 2 nanoparticles. The reaction conditions were optimized by changing different parameters such as catalyst, solvent, catalyst loading, and temperature. It has been found that the catalyst gave higher activity under solventless conditions than methanol. The GO-SnO 2 composite was recycled for up to four cycles with minimal loss in activity. Fig. 3 (a) XPS survey spectra of GO-SnO 2 nanocomposite, (b) Sn 3d core level XPS spectra of GO-SnO 2 nanocomposite, (c) C 1s XPS spectra of GO and (d) C 1s XPS spectra GO-SnO 2 nanocomposite. 39196 | RSC Adv., 2015, 5, 39193-39204 This journal is