Fluorescence Properties Of Molybdenum Disulfide Quantum Dots And Sensing Of Copper Ions

Molybdenum disulfide quantum dots have a small size effect and a boundary effect due to their size of less than 10 nm,thereby generating photo luminescence,and can be applied in the fields of bioimaging,fluorescence detection,photocatalysis,and photovoltaic devices.At present,the mechanism and precise control of molybdenum disulfide quantum dots fluorescence are few and are in the phase of exploration.In this dissertation,starting from the preparation of molybdenum disulfide QDs,the peak position,intensity and fluorescence quantum efficiency of fluorescence were adjusted by changing the synthesis conditions,and the application of molybdenum disulfide QDs in the detection of copper ions was studied.This article mainly carried out the following work:(1)Molybdenum disulfide quantum dots are synthesized by bottom-up method using sodium molybdate as molybdenum source and L-cysteine as sulfur source.The morphology and structure of the quantum dots are characterized.It is proved that our synthetic material is MoS2 QDs,and the size of the quantum dots is counted,the size distribution is between 1-4.5nm,and the average size is about 2.5nm.(2)Photoluminescence of molybdenum disulfide QDs was explored.The emission peak position of MoS2 QDs will be red-shifted with the increase of excitation wavelength and have an excitation wavelength dependence.Moreover,under short-time UV illumination,the fluorescence intensity hardly attenuates,providing a reliable basis for subsequent fluorescence sensing applications.(3)The effects of different experimental conditions on the fluorescence properties and quantum efficiency of molybdenum disulfide(QDs)quantum dots were investigated.The molybdenum sulfur source ratio,hydrothermal time,hydrothermal temperature and the pH of the reaction system were changed to optimize the synthesis conditions,and the fluorescence quantum efficiency of molybdenum disulfide was improved.The maximum fluorescence quantum efficiency reached 37%.(4)A method for detecting copper ions using molybdenum disulfide quantum dots was proposed.The relationship between the concentration of copper ions introduced and the degree of fluorescence quenching of quantum dots was studied.Copper ions were in the range of 0-1 ?m.The concentration of copper ions was proportional to the degree of fluorescence quenching,and a fitting curve was given.The calculated limit of detection is 0.098 ?m,which is more sensitive to copper ions than the 0.226?m detection limit of copper ions detected by graphene.Moreover,the detection process has no dependency on PH.The selectivity of the fluorescence intensity of molybdenum disulfide(QDs)quantum dots was also studied in the experiment.The presence of other ions will not interfere with the experiment.