Shape controlled growth of pyrite FeS2 crystallites via a polymer-assisted hydrothermal route

Well-defined pyrite FeS2 microcubes and micro-octahedra with high-yield and good uniformity were successfully synthesized by a convenient and simple polymer-assisted hydrothermal method. Employing S as sulfur source and FeCl2 center dot 4H(2)O as the precursor in the presence of polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA), cube-shaped and octahedron-shaped pyrite FeS2 crystallites were successfully obtained by simply adjusting the NaOH concentration, and the size of the product can be readily tuned by varying the reaction parameters. The effects of various NaOH concentrations and the polymer dosage on the morphology evolution process were investigated systematically. The phase composition, morphology, structure, and properties of the as-obtained products were studied by X-ray diffraction, field emission scanning electron microscopy, (high-resolution) transmission electron microscopy, Fourier transform-infrared spectroscopy, X-ray photoelectron spectrometry, and UV-Vis spectrometry. It was found that besides the capping effect of the polymer reagents, the "synergistic effect" or "cooperative effect" between the PVA and the PVP also played a crucial role in directing the growth of the FeS2 crystallites. The possible formation mechanism of the FeS2 phase and morphology was tentatively proposed based on a series of contrast experiments. Moreover, the optical properties were also preliminarily studied. This method can be easily controlled and is expected to be extendable to the fabrication of other metal chalcogenides with controlled shape and structure.