Controlled Synthesis,Characterization And Properties Of Nanpatructured Metal Sulfides And Multimetal Phosphates

As one of the most complicated metal chalcogenides (variations on phases and stoichiometric compositions), cobalt sulfides are of particular interest as a result of their unique catalytic, electrical, optical and magnetic properties and their potential applications for hydrodesulfurization and hydrodearomatization in many industrial fields. Synthesis of cobalt sulfide nanocrystals with well-defined shapes and investigate their formation mechanism to control their sizes, morphologies and properties has become one of the central subjects because of the affinitive relationship between the shape and the property. The preparation of cobalt sulfide has made a great progress, but their shape controlled synthesis is not solved. Therefore, simple, cost-effective and practical synthesis of cobalt sulfides with novel morphology is a challenging subject for fundamental research.Materials with NASICON structure are considered usable as solid electrolytes in lithium batteries due to their relatively high ionic conductivity and the negligible electronic conductivity. The previous reports indicate that MSn2(PO4)3 with NASICON structure can be prepared by solid-state reactions and hydrothermal method. However, as far as we know, there is still no report for the synthesis of nanostructured NaSn₂(PO₄)₃. Herein, we report the preparation and electrochemical properties of NaSn₂(PO₄)₃ nanocubes in reverse micelles under solvothermal conditions. The details are summarized as follows:1. The preparation of exquisite hierarchical worm-like Co_1-xS microtubes by a one-pot complex-surfactant-assisted hydrothermal method is successfully achieved for the first time. The hierarchical structures of the microtube wall are assembled by numerous interleaving hexagonal nanoplates. The experimental results indicated that the"soft template"of surfactant CTAB and the complexant of en both played important roles for the formation of hierarchical Co_1-xS microtubes. A possible formation mechanism in the growth processes is proposed. Additionally, the electrochemical and magnetic properties of Co_1-xS microtubes were studied systematically.2. Uniform single-crystalline CoS₂ nano-octahedrons have been prepared in high yield by the assisted of caping agent poly(vinyl pyrrolidone) (PVP) and complexing agent (en) through a facile and simple hydrothermal process. The octahedral ]structures exhibit a high geometric symmetry with smooth surfaces and the mean edge length is ¹20 nm. Contrast experiments indicate that the capping agent (PVP), the complexing agent (sodium citrate) and the reaction temperature play important roles for the formation of octahedral CoS₂ nanostructures. A possible formation mechanism was proposed based on the evolution of this morphology as a function of hydrothermal time. The magnetic study indicates that the CoS₂ nano-octahedrons are ferromagnetic at low temperature.3. Nanocubes of NaSn₂(PO₄)₃ have been successfully synthesized in reverse micelles under solvothermal conditions for the first time. The synthesized products were systematically studied by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). It is found that both reaction time and temperature have significant effects on the morphology of the products. Such a microemulsion-based solvothermal approach may be extended to fabricate complex architectures of other materials.