Preparation And Application Of Molybdenum Disulfide Based Nanocomposites

The discovery and application of graphene nanomaterials have opened up people's interest in two-dimensional materials.Among these two-dimensional layered nanomaterials molybdenum disulfide?MoS₂?is a typical layered transition metal sulfide,the atoms in the layer are connected by covalent bond,and there is weak van der Waals force between molecular layers.This unique structural characteristic can be widely used in optical devices,electronic devices,and electrochemical sources,sensor,catalysis,solid super lubricant,solid secondary lithium battery and other fields.At present,various forms of molybdenum disulfide nanostructures have been prepared by vapor synthesis,electrochemical deposition,thermal decomposition,sonochemical synthesis and hydrothermal method.In addition,the application of molybdenum disulfide nanosheet is limited by its own size and composition defects,it has size effects and edge effects,which produce photoluminescence,it can be used as an ideal optical probe to detect metal ions,biomolecules,small molecules,biomarkers and imaging.Based on the background,this topic introduces the synthesis method,performance characterization and application of MoS₂ QDs and composite materials.Firstly,MoS₂ QDs were prepared to study their applications in the detection of hydroquinone,and eventually applied to biological imaging.Secondly,molybdenum disulfide composite was prepared,and their photocatalytic properties under visible light were syudied.Therefore,the research results on the preparation and properties of molybdenum disulfide and its composites are as follows:In this paper,water-soluble and highly stable blue fluorescent MoS₂ QDs are synthesized by one step hydrothermal method using sodium molybdate?NaMoO₄·2H₂O?as the molybdenum source and L-cysteine as the sulfur source.The morphology and size can be clearly observed by transmission electron microscopy,and the size of the quantum dots are counted,the size range is between 1-7nm,and the average size is about 3.5nm,and the dispersion is relatively uniform.From the fluorescence dependent spectrum of MoS₂QDs,it can be observed that the emission peak of MoS₂ QDs exhibited a red shift with the increase of excitation wavelength.Among them,L-cysteine is not only a sulfur source,but also can be used as a surface passivating agent to provide amino and carboxyl functional groups for the synthesized MoS₂ QDs,making the synthesized molybdenum disulfide quantum dots have good water solubility and stability.In addition,the relationship between the concentration of hydroquinone and the degree of fluorescence quenching of quantum dots was studied.The concentration of hydroquinone is 0-20?M.The concentration of hydroquinone is 0-20?M.the concentration of hydroquinone is proportional to the quenching of quantum dots,and the fitting curve is given.Finally,the synthesized MoS₂QDs had good biocompatibility and low toxicity by the MTT experiments in HeLa cells and could be used as a probe for biological imaging in cells.The above results show that MoS₂ QDs can be used as an alternative to traditional fluorescent probes in environmental monitoring,bioanalysis,disease diagnosis and treatment.The core-shell structure of Ppy@MoS₂ was prepared by hydrothermal-oxidative polymerization methods.Using pyrrole as raw material,polyvinyl alcohol?PVP?as protective agent,Fe³⁺as catalyst,by oxidative polymerization synthesized polypyrrole?Ppy?nanoparticles,and Ppy as a template added sodium molybdate as Mo source,thiourea as sulfur source,hydroxylamine hydrochloride as reducing agent,F127 as surfactant synthesized core-shell structure of Ppy@MoS₂ by hydrothermal method?average diameter of 80nm?.The characteristics of Ppy@MoS₂ nanocomposite have been successfully synthesized verified by XRD,SEM,XPS and FT-IR.The photocatalytic ability of the prepared Ppy@MoS₂ nanocomposite was verified by degradation of dye MB solution.The Ppy@MoS₂ nanocomposite had achieved the degradation rate to 99.3%under irradiation for 60 min,while the degradation rate of pure MoS₂ and Ppy were merely56%and 37%,In addition,the synergistic effect between Ppy and MoS₂ is beneficial to inhibit the recombination of photocharges and improving photocatalytic activity.However,the photocatalytic activity of Ppy@MoS₂ nanocomposite was still not less than 99.3%after five times of recycling.Through the above study,the prepared Ppy@MoS₂nanocomposites not only have high catalytic activity,but also have high stability performance.