Controllable Synthesis And Property Research Of Functional Metal Sulfide Nanomaterials

As a kind of functional inorganic materials, metal sulfide nanomaterials present some interesting properties, such as excellent optical, electrical, magnetic, catalytic, etc. So they have wide application prospects in semiconductor, biomedical, photoluminescence devices, solar cells, infrared detectors, optical fiber communications, pigments, lubricants, and so on. In this work, magnetic iron sulfide, luminescent zinc sulfide and battery materials of tin sulfide are investigated. Most of the developed synthetic routes of metal sulfide nanomaterials have been various problems. This work of the dissertation has explored a single-source precursor method （decomposing single source molecular precursors in high boiling point organic solvents） to prepare metal sulfide nanomaterials. In this method, thermal decomposition process and solvent composition are controlled to achieve controlling the crystal nucleation and growth process, and further access to obtain high yield, uniform size adjustable, controlling the morphology of metal sulfides. This work also discusses the related reaction mechanism. The main works achieved are summed up as following:1. Cubic phase Fe₃S₄ nanoparticles and monoclinic phase Fe₇S₈ were prepared in the mixture solvents of oleic acid and oleylamine and 1-octadecane by pyrolyzing Fe（Ddtc）₃ and Fe（Ddtc）₂（Phen） precursors, respectively. Both of Fe₃S₄ and Fe₇S₈ are pure-phase and single crystal, and have the strong paramagnetism magnetic which Fe₃S₄ nanoparticles relatively stronger. Two kinds of SSPs, Fe（Ddtc）₃ and Fe（Ddtc）₂（Phen）, were utilized in the present study. The results manifested that the different sorts of precursors resulted in different iron sulfide compounds, in terms of the chemical composition, shape and crystalline structures. We speculated that Phen group decomposed from the precursor played as the chelating ligand to strongly coordinate to the iron faces. In the reaction system of Fe（Ddtc）₂（Phen）, when we change the mixture solvents （add oleic acid ）, we found that Fe₇S₈ nanoplates gradually transformed into amorphous FeSX nanobelts with increasing of precursor concentration. We suggest that the as-observed two dimensional growth modes for the FeSx naoribbons were attributed to the templating direction of micellar structures formed by self-assembly of capping ligands.2. We successfully synthesized of ultrathin single crystal ZnS nanowires with the diameter of 4.4 nm via the thermolysis of a single-source precursor of Zn（Ddtc）₂ in oleylamine solvent at 300℃. Bohr diameter of ZnS is 4.8 nm. The obtained ZnS nanowires exhibit good optical properties. We observed nanowires begin to break by increasing of precursor concentration, and formed ZnS elongated nanoparticles finally. Moreover, the morphology of the ZnS products can be easily turned to monodispersed ZnS nanoparticles with diameter of 9.5 nm by adding oleic acid in the oleylamine solution. We suggested that there are two important factors responding for its formation:①formation of ordered mesostructure between Zn（Ddtc）₂ and oleylamine,②the selective adsorption of oleylamine onto （100） crystal planes （Figure 1b） and inhibits the growth of （100）. When oleic acid was mixed with oleylamine in the reaction, the relative chemical environment for the configuration of the nuclei was changed. We suspected that oleic acid tends to cap the ZnS nuclei and passivate the surface of products during the reaction, which renders monodispersed stable ZnS nanoparticles.3. We successfully synthesized ultralarge single crystal SnS rectangular nanosheets （7000 nm×3000 nm×20 nm） from the pyrolysis of single source precursor of Sn（Ddtc）₂（Phen） in the mixture of oleylamine and 1-octadecane. The ultralarge orthorhombic SnS nanosheets exhibit fascinating electrochemical properties with a capacity of 350 mAh/g around 1.2 V and an appealing cycling reversibility. In addition, uniform SnS2 hexagonal nanoplates were obtained by easily tuning the reaction conditions. In the present research, we found that the surfactants constituent （oleic acid / oleylamine）, precursor concentration and reaction temperature played important roles in determining the morphology and chemical composition of the final products:①Oleic acid favors the formation of nanoparticles, whereas oleylamine facilitates the growth of two dimensional nanostructures by specifically binding to a certain crystal facet.②SnS2 was formed at lower temperature and SnS was formed at higher temperature.③Excess amount of oleylamine gives an even stronger reductive environment.