▎ 摘　　要

The present study reports an efficient, surfactant-free, novel and facile green method for the immobilization of Cu NPs on the surface of the graphene oxide/manganese dioxide (GO/MnO2) nanocomposite using Cuscuta reflexa leaf extract. In fact the phytochemical content of the plant extract are responsible to biosynthesis of Cu nanoparticles (NPs) and their stabilization by functionalizing the surface of graphene. The Cu NPs were characterized by Fourier transformed infrared spectroscopy (FT-IR) and UV-visible spectroscopy. MnO2 NPs and GO/MnO2 nanocomposite were prepared by using a simple one-step hydrothermal method without using any toxic solvent. The synthesized GO/MnO2 and Cu/GO/MnO2 nanocomposites were characterized using X-ray diffraction analysis (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM) images, Brunauer-Emmett-Teller (BET), Thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), energy-dispersive X-ray spectroscopy (EDS), elemental mapping and FT-IR spectroscopy. The synthesized Cu/GO/MnO2 nanocomposite was then successfully used as a reusable catalyst for the reduction of 2,4-dinitrophenilhydrazine (2,4-DNPH), 4-nitrophenol (4-NP), Rhodamine B (RhB), Congo red (CR), methyl orange (MO) and methylene blue (MB) using NaBH4 in water at ambient temperature. This method is clean and environmentally friendly without using any toxic reducing agents. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.