Preparation And Optical Properties Of Transition Metal Chalcogenide Quantum Dots

In 2004,Novoselov et al.successfully stripped a thin layer of single-layer graphite,graphene.The enthusiasm of researchers for layered materials has been raised around the world.However,since graphene has no electron band gap,the application of graphene is limited.The transition metal-dichalcogenide(TMDC)material with similar structure shows a limited band gap,and its unique electronic and optical properties have become the current research hotspots.The TMDC quantum dots,due to their size in the nanometer range,are affected by the quantum size effect and exhibit novel physical and electronic optics characteristics,becoming a new class of nanomaterials.Recent studies have shown the broad application prospects of TMDC quantum dots in energy,biology,medical,sensing and catalysis.In this master’s thesis,we optimized the method for preparing transition metal chalcogenide quantum dots,and successfully prepared WS2 quantum dots with uniform size distribution and crystal phase structure by liquid phase laser ablation and liquid phase ultrasonication.And WSe2 quantum dots,and based on this enhanced their fluorescence intensity,in addition to the first use of WSe2 quantum dots for laser gain media,and achieve laser emission.The main research contents of this thesis are as follows:The first part:an overview of the structural properties of TMDC materials and the definition of quantum dots,summarizes the preparation methods and applications of transition metal chalcogenide quantum dots,and further elaborates the research content and ideas of this paper.The second part:introduces the experimental process and results of this paper.The WS2 quantum dots with absolute ethanol as solvent and the WSe2 quantum dots with polyethylene glycol 400(PEG400)as solvent are prepared by liquid laser ablation.Transmission electron microscopy characterized the morphology of some of the samples,indicating that the quantum dots we prepared have the characteristics of a crystalline phase structure.The WSe2 quantum dots prepared by liquid phase sonication were prepared by PEG400 as solvent.The morphology of WSe2 quantum dots with PEG400 as solvent was characterized by transmission electron microscopy(TEM).The results show that the quantum dots prepared by us have a crystal phase structure.characteristic.The third part:Analyzed the fluorescence characteristics of the prepared quantum dots,and found a way to enhance the fluorescence characteristics of quantum dots by comparison.On the basis of this,by designing different types of laser microcavities(Fabri-Perot laser cavity,whispering gallery modes microcavity)with such quantum dots as laser gain media,the transition metal chalcogenide quantum dots are realized.Laser emission,the feasibility of applying such materials to laser working materials was confirmed in experiments.