Study On Surface Chemical Modification And Application Of Molybdenum Disulfide

Since the successful development of exfoliating graphene technology,research on ultra-thin two-dimensional nanomaterials in the field of physics and chemistry has increased significantly.The unprecedented nature exhibited by this unique type of nanomaterial has been applied in a variety of fields.Among them,single-layer transition metal dichalcogenides?TMDs?have a sheet-like structure similar to graphene and have received significant attention.As a new class of two-dimensional layered materials in the large family of two-dimensional atomic crystals,TMDs rely on their unique band structure?single layer has direct band gap?and unusual physical properties such as spintronic properties,valleys valence characteristics,edge metal states,etc.,make it have a very broad potential application in the fields of optpelectronic devices,energy storage devices and electrocatalysis.Monolayer molybdenum disulfide?MoS2?is a semiconductor material with direct band gap of¹.9 eV,which has been researched on nano physical and electronics devices.Controlling the preparation of high-quality,large-area and thin-layer MoS2 is the key prerequisite for realizing the research of its novel physical properties and exploring the broad application prospects.In this paper,large area thin-layer MoS2were prepared by mechanical exfoliation and chemical vapor deposition?CVD?.Furthermore,the prepared MoS2 was chemically etched by sodium hypochlorite?NaClO?solution to obtain regular etching patterns on the edges and basal plane.The chemically activated MoS2?ca-MoS2?was obtained by defect engineering and chemical etching,and applied to the catalyst for electrochemical hyderogen evolution reaction and biosensor,which exhibit improved electrochemical properties and sensing characterication on the basic of original sample.The main conclusions are obtained as follows.?1?Explore the etching effect of NaClO on MoS2.NaClO was subject to anisotropic chemical etching of thin layer MoS2 obtained by mechanical exfoliated and CVD growth,respectively.The concentration of etchant is adjusted,and the lower the concentration,the more stable etching effect,and a stable etching process can be obtained with 0.03 mol L^-1 NaClO solution.Atomic force microscopy?AFM?,scanning electron microscopy?SEM?,Raman and other technologies to characterize the structure and morphology of MoS2 at different reaction times,the study found that the chemical etching of non-defective MoS2 occurred first at the edge of the sample and most of the etching angle was 120°;for MoS2 samples with natural defect sites,the etching phenomenon first occurs at the defect sites,where forms triangle etching pits.?2?Chemically activated MoS2 was studied for hydrogen evolution reaction.Defect sites were fabricated on the MoS2 basal plane by the treatment of oxygen plasma?O2 plasma?defect process,which was then chemically etched with diluted NaClO and applied to electrocatalytic hydrogen evolution reaction?HER?.The electrochemical properties of the chemically activated MoS2 powder was measured by electrochemical three-electrode system using a glassy carbon electrode loaded with sample as the working electrode,a carbon rod as the auxiliary and Ag/AgCl electrode as the reference electrode.In this experiment,the effects of different O2 plasma and etch time on the HER efficiency of MoS2 were investigated.Under optimized conditions,MoS2 powder with O2 plasma for 10 min and chemical etching for 5 minutes obtained the balance point of the largest active sites.The smallest overpotential was 0.34 V when the current density was 0.5 mA cm^-2.?3?An electrochemical biosensor based on MoS2 was studied.Chemically activated MoS2 used as linker between glassy carbon electrode and linearized Microcystin-LR?Lineared MC-LR?,and the MoS2 sample was linked to the algal toxin.The other end of Lineraed MC-LR is chemically bond with gold nanoparticles?AuNPs?through a protein crosslinker 3,3-dithiodipropionate bis?N-succinimide??DTSP?to amplify the current signal.Special degrading enzyme can cleave linear algal toxins at specific sites,and the entire sensor system releases AuNPs and reduces electron transport in the electrolyte.