Study On Preparation And Properties Of Transition Metal Sulfides Coated With Boron Nitride

Transition metal disulfide has been paid attention by many researchers because of its excellent graphene-like properties,and its adjustable band gap just makes up for the lack of band gap of graphene,which seriously limits its application in optical and electronic devices.The optical properties of transition metal disulfide two-dimensional layered materials are seriously layer-dependent.At present,mechanical stripping method is used to prepare monolayer transition metal disulfides,which is simple and easy to operate,but the area of the exfoliated nanosheets are small and the structure is uncontrollable.In order to achieve the best application performance under extreme conditions,researchers are committed to the study of transition metal disulfide nanocomposites,Therefore,the transition metal disulfides coated with BN(MoS₂-BN,WS₂-BN)were studied and analyzed systematically in this paper.In this paper,MoS₂ was prepared by one-step hydrothermal method.The effects of process conditions such as type and concentration of surfactant,precursor,reaction temperature and time on the growth of molybdenum disulfide were studied systematically,and its morphology and photoluminescence properties were analyzed.The MoS₂ prepared by this method has high purity and good crystallinity.With the change of process conditions,MoS₂ nanostructures with different morphologies such as sphere-like,flower-like and rod-like were prepared.The luminescence peaks of MoS₂ nanostructures with different morphologies are all about 500 nm.The size of nano-spherical MoS₂ is uniform,the size is small,and the luminescence intensity is the strongest.MoS₂ nanospheres and BN precursors were nitrided at high temperature in NH₃atmosphere to prepare MoS₂-BN composites.MoS₂ particles were coated by BN sheets.The oxidation temperature of MoS₂ nanospheres is increased from 225?to 715?by BN coating and show a strong red emission band centered on 678 nm at room temperature.Needle-like and flake-like WS₂ were prepared by one-step liquid phase reduction method.The effects of various factors on the growth of WS₂ were discussed from three aspects:surfactants,reducing agents and precursors.WS₂ can also be obtained by high temperature calcination method.In the high temperature calcination method,the WS₂precursor was firstly prepared by hydrothermal method,and then calcined at high temperature in a vacuum furnace to obtain WS₂.With the change of calcination temperature,rod-shaped and columnar WS₂ were prepared.The luminescence peaks positions of WS₂with different morphologies are between 500 nm and 525 nm,and the acicular WS₂luminescence intensity is stronger.WS₂-BN composites were prepared by uniform mixing of WS₂precursors and BN precursors and calcined at high temperature in N₂ atmosphere.The effects of different process conditions on the products were studied,such as reaction temperature and time,molar ratio of nitrogen to boron and so on.Under the optimum reaction conditions,a series of WS₂-BN complexes were prepared by changing boron source and nitrogen source.The WS₂-BN complex has a single fluorescence signal with high intensity and its optical properties are of great significance for expanding its applications in green and near-infrared light-emitting devices.