From polymer-metal complex framework to 3D architectures: growth, characterization and formation mechanism of micrometer-sized alpha-NiS

A complex-ion reaction route under solvothermal conditions was investigated for the preparation of micrometer-sized NiAs-type alpha-NiS with complex architectures, on the basis of the strategy that the framework structure of PEG-NiCl2 complex could provide orientation for the growth of 3D NiAs-type alpha-NiS crystals. The as-prepared NiS powders with flower-like architectures were characterized by X-ray diffraction pattern (XRD), field emission scanning electron microscopy (FE-SEM), ultraviolet, visible light (UV-Vis) and photoluminescence (PL) spectra. Fourier transform infrared absorption (FT-IR) spectra as functions of temperature were recorded to investigate the coordinative chemical effect in the PEG-NiCl2 complex. When PEG-6000 was substituted with poly(vinyl alcohol) (PVA) or poly(vinyl pyrrolidone) (PVP), two other complex architectures (i.e. tennis-ball shaped or urchin-like) were produced. On the basis of a series of supplementary experiments and the result of FT-IR spectra, it was found that both the framework structure of the polymer-metal complex and the functional groups on the polymers had a considerable effect on the final architectures of alpha-NiS crystals.