Synthesis And Characterization Of Nanocrystal Iron-sulfur Compound Functional Materials

Iron pyrite (FeS2) is significantly more attractive in both cost and availability than all other compounds for its comparable band gap energy (Eg=0.95eV), and absorption coefficient of105cm-lfor energies greater than1.1eV are also very attractive. In addition, pyrite is composed of very abundant, cheap and nontoxic element.In this thesis, we prepared purity pyrite FeS2using DMSO as solvent at a low temperature in one step using solvothermal method. Many influencing factors such as surfactant and its concentration, maintained time to the morphology of pyrite FeS2were studied. With the same preparated conditions at different filling fraction (60%,70%), we obtained pyrite FeS2with different morphology. The pressure can influence the temperature contrast at top and bottom of the autoclaveand play a role at delivering solute.Polyvinylpyrrolidone (PVP) is essential for the formation of octahedral crystals and reducing particle size. That means the surfactant significantly affected the shape of the final products. When polyvinyl alcohol (PVA) and polyethyleneglycol (PEG) used as surfactants, we could not get the pure pyrite FeS2. That may be because much more hydroxyl group will lead to ferrous iron oxidizing to ferric.Phase pure, highly crystalline cubic pyrite FeS2nanocrystals (NCs) were successfully prepared using a trioc tylphosphine oxide (TOPO) assisted hot-injection method. The different size cubic pyrite FeS2with oleylamine as solvent and different sulfur source (sublimed sulfur, thioacetamide, L-cysteine hydrochloride monohydrate) under the TOPO as a surfactant. One can see TOPO had a significant role to prevent aggression of cubic FeS2. It also control the crystal growth orientation of cubic FeS2. In addition, the greigite Fe3S4nanoplates were obtained by hot-injection method with ferrous iron (ferric nitrate, Iron (â…¢) acetylacetonate) as ferrous source and sublimed sulfur as sulfur source. These nanoplates mainly existed in the triangular flake morphology. And the efflorescent nanoplate greigite composed was synthesized firstly when ferrous chloride as ferrous iron and thio urea as sulfur source.