Sodium thiosulfate-assisted synthesis of NiS_2 nanostructure by using nickel(II)-Salen precursor: optical and magnetic properties

摘要

A NiS_2 nanostructure with a protective layer of Ni~(2+0 and SO_4~(2-) ions around it has been successfully synthesized using the Ni(II)-Salen (Salen = N,N'-bis(salicylidene)ethylenediamine) complex via a simple solvothermal approach in the presence of anhydrous sodium thiosulfate (Na_2S_2O_3) as sulfur source and stabilizer. Unexpectedly, no one kind of pure nickel sulfide nanostructure was prepared using the Ni(II)- Salophen complex or some of the simple mono and bidentate Ni(II) complexes as starting materials and the obtained products were a mixture of nickel sulfides. In the photoluminescence spectrum of the prepared NiS_2, two peaks were evident at 400 and 420 nm with emission maxima, and one broad peak with emission minima was located at 800 nm. The as-synthesized NiS_2 nanostructure displays a weak ferromagnetic behaviour at room temperature, which has small remanent magnetization and saturation magnetization compared to bulk NiS_2. These changes might be attributed to the existence of a protective layer of nickel and sulfate ions around the NiS_2 nanostructures that was confirmed by Energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) and Raman spectroscopy. The prepared nanostructure has been characterized structurally, electrochemically, optically and magnetically by available methods like X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy, Fourier transform infrared and Raman spectroscopy, Cyclic voltammetry (CV), Photoluminescence (PL) spectroscopy and vibrating sample magnetometer (VSM).