Preparation Of Nanocrystailine Metal Sulfides Via Reduction Method

Nanocrystalline metal sulfides shows particular characterizations, such assurface effect, small size effect, quantum size effect, quantum tunnel effect, etc.because of their special structures, which leads to their different physical andchemical properties from bulk materials in optics, electrics, magnetics and so on.Therefore they have become one of the research hotspots in the fields ofnanoscience in recent years.Three kinds of metal sulfides nanocrystals: manganese sulfide, zinc sulfideand lead sulfide, were prepared via the route of gas-solid phase reduction of thesulfates. Besides, the structures and properties of the as-prepared samples werecharacterized by X-ray powder diffraction (XRD), transmission electronmicroscopy (TEM), field emission scanning electron microscopy (FESEM),electronic diffraction (ED) and energy dispersive X-ray spectra (EDS). Meanwhile,the possible mechanism of the reduction was also discussed. The main contentswere as follows:(1) α-manganese sulfide nanocrystals were prepared using manganese sulfateas raw material. The result shows that the optimal reaction temperature for thepreparation of α-MnS nanocrystals was600°C, while the reaction time was6h.The single crystal sample with fine crystallinity and purity can be indexed to thecubic face. And the Mn to S ratio of the sample is in accordance with stoichiometricratio of MnS. The formation mechanism of α-MnS nanocrystals was discussed aswell.(2) Zinc sulfide nanocrystals were prepared using zinc sulfate as raw material.The result shows that the optimal reaction temperature for the preparation of ZnSnanocrystals was400°C, while the reaction time was9h. The sample can beindexed to face-centered cubic system, with fine crystallinity and purity. And thesample presents flakes, which consists of a number of tiny particles, with someother particles on the surface of the flakes. The formation mechanism of ZnSnanocrystals was discussed and proved through the analysis of the by-product in theend of the chapter.(3) Lead sulfide nanocrystals were prepared using lead sulfate as raw material. The result shows that the optimal reaction temperature for the preparation of PbSnanocrystals was400°C, while the reaction time was12h. The sample with finecrystallinity and purity can be indexed to face-centered cubic system. And thesample presents flakes, which consists of many nanoparticles, with some other tinyparticles on the surface of the flakes as well. The formation mechanism of PbSnanocrystals was discussed and proved through the analysis of intermediateproducts and by-product in the end.