The Catalytic Activities Of Transition Metal Dichalcogenides And Their Application

All life activities in nature require the participation of enzymes.Due to their high specificity,mild reaction conditions and high catalytic efficiency,enzymes have been widely applied in many fields.However,purification of enzymes is difficult and expensive,which limits their application,so it is great attention to develop enzyme mimetics.The rapid development of nanotechnology and nanomaterials in the field of catalysis promotes the research of enzyme mimetics.In recent years,the layer two-dimensional metal materials similar to graphene,especially transition metal dichalcogenides(TMDCs)have greatly attracted the research interest of the scientists.In this thesis,TMDCs(such as MoS2,WS2)nanosheets were found to possess the peroxidase-like catalytic activity and on these bases the colorimetric sensors for H2O2,glucose,PO43-,cholesterol were developed.The thesis can be divided into four chapters.In the first chapter,the progress of transition metal dichalcogenides was introduced.In the second chapter,WS2 nanosheets were found to possess peroxidase-like catalytic activity,which can catalyze the chromogenic reaction of TMB-H2O2 to generate blue products.The catalytic activity of WS2 nanosheets is strongly dependent on temperature,pH and reaction time,the corresponding optimal conditions are 60 ?,pH 6.9 and 30 min,respectively.Steady-state dynamics analyses show that the catalytic behavior of WS2 nanosheets follows the typical Michaelis-Menten behavior and the ping-pong mechanism.The apparent Km value of WS2 nanosheets with TMB as the substrate is 1.83 mM and the apparent Km value with H2O2 as the substrate is 0.24 mM.Based on the dependency of catalytic activity of WS2 nanosheets on the concentration of hydrogen peroxide,cheap,simple,highly selective and sensitive colorimetric methods for hydrogen peroxide and glucose were proposed.The linear range for H2O2 is ranged from 10 ?M to 100 ?M with a limit of detection 1.2 ?M.The linear range for glucose is ranged from 5 ?M to 300?M with a limit of detection 2.9?M.In the third chapter,molybdenum disulfide(MoS2)nanosheets were also found to possess peroxidase-like catalytic activity to catalyze the TMB-H2O2 chromogenic reaction.On addition of phosphate,the catalytic activity of MoS2 nanosheets was decreased.Therefore,a simple and low-cost colorimetric sensor for the detection of phosphate in the beverage Coca-Cola was developed on the basis of peroxidase-like catalytic activity of MoS2 nanosheets and the coordinating ability of phosphate to Mo ions of MoS2 nanosheets.The linear range for the detection of phosphate was ranged from 2 ?M to 40 ?M with a limit of detection of 0.79 ?M.In the fourth chapter,cholesterol can be oxidased to cholest-4-en-3-one and hydrogen peroxide by cholesterol oxidase in the presence of oxygen.The concentration of hydrogen peroxide is directly proportional to the concentration of the cholesterol.On this base a rapid,simple and low-cost colorimetric sensor for the detection of cholesterol was proposed.The linear range for cholesterol is ranged from 2 ?M to 200 ?M with a limit detection of 0.76 ?M.