The Synthesis And Application Of Molybdenum Disulfide And Its Composites

The development of 2D materials has attracted great attention recently for the discovery of graphene, while the transition metal dichalcogenide（TMDs） have attracted more attention due to their superior optical and electrical properties. MoS₂ has been explored depthly. Hence, the optical properties of MoS₂ and its complex has been investigated intensely in this paper. Firstly, MoS₂ quantum dots were prepared to study their fluorescence properties, and eventually applied to biological imaging. Secondly, MoS₂ composites with more morphologies were synthesized, and their photocatalytic properties under visible light were investigated, aiming to find catalysts with high catalytic activity. Therefore, this thesis carrys out the following four-part work on preparing and exploring the optical properties of MoS₂ and its composites:Firstly, according to the weak amine reduction method, Mo S₂ quantum dots were synthesized in colloidal solution using oleylamine as reducing agent. And their tunable photoluminescence was achieved by changing the molar of oleylamine or reaction time. With the help of amphiphilic compounds, the resultant MoS₂ quantum dots could be transferred from organic to aqueous phase. MoS₂ quantum dots in aqueous solution have many advantages, such as good dispersion, low toxicity and photoluminescent properties, which make them promising materials for application in biological fields. In addition, this method was aslo used in the preparation of fluorescent carbon dots（CDs）, then dual emission temperature-sensitive sensor was constructed with gold nanoclusters, which was expected to be applied to temperature measurement of cells.Secondly, MoS₂/CdS nanocomposites with flowerlike morphology were prepared by one-pot hydrothermal method. The specific surface area of nanocomposites was significantly increased in the presence of MoS₂ nanosheets. The experimental results indicated that the asprepared products showed a flowerlike nanostructure with size at 800 nm（the molar ratio of MoS₂ to CdS is 5: 1）. Very importantly, as-prepared flowerlike MoS₂/CdS heterostructures exhibited excellent performance in adsorption and photocatalytic activity for degrading methylene blue under visible light than pure CdS or pure MoS₂. It took 1 hour to degrade as high as 87.2% of methylene blue（MB） with 15 mg as-prepared catalyst. The flowerlike MoS₂/CdS without any irregularly aggregation contribute to the largest surface area and most efficient catalytic activity.Thirdly, the TiO₂/MoS₂ core-shell structure was prepared by solvothermal method, and the shell thickness of composite could be controlled through adjusting the relatively amount of TiO₂ seeds and precursor of MoS₂. Yolk-shell structure and hollow structure of TiO₂/MoS₂ composite were obtained by targeted etching. In summary, the structure TiO₂/MoS₂ was transited from shell structure to yolk-shell structure and hollow structure. An increase the proportion of TiO₂/MoS₂ heterojunction as a highly active part of photocatalytic would improve visible light catalytic activity. Under visible light, it took 3.5 hours to degrade rhodamine B（RhB） or 2 hours to degrade MB completely with 10 mg as-prepared catalyst, while only 60.1% MB was degraded by anatase TiO₂ under the same condition.Finally, under our previously work, magnetic Fe₃O₄ particle has been introduced, ―sugar coated haws on a stick‖ structure and core-shell structure of Fe₃O₄/TiO₂ composite was prepared via adjusting the hydrolysis rate of the titanium source. Further coated with MoS₂, ―sugar coated haws on a stick‖ structure and three-layer core-shell structure of Fe₃O₄/TiO₂ /MoS₂ composite was prepared through solvothermal method. MoS₂ was filled in the mesoporous of TiO₂ core, forming heterojunction on the furface and near-surface of TiO₂ under solvothermal conditions. Under visible light, it took 2.5 hours to degrade RhB or 2 hours to degrade MB completely with 15 mg as-prepared catalyst. The effective magnetic reycle of the catalyst was achieved while high visible light catalytic activity was ensured simultaneously.