Preparation Of Fluorescent Molybdenum Disulfide Nanomaterials And Their Application For Detection Of Some Ions In Environmental Samples

In this paper,fluorescent molybdenum disulfide nanosheets were hydrothermally prepared by using sodium molybdate and thiourea as the precursors materials.The fluorescent molybdenum disulfide nanomaterials were used as a fluorescent probe or nanozyme,and were combined with the spectroscopy and chemometrics methods for analysis of environmentally common ions(Pb²⁺,S2-,Fe²⁺).The proposed methods in the thesis were environmental-friendly,easy to operate,high selective,high sensitive and can be applied in the real sample.The main contents of this paper are as follows:Chapter one: It describes the synthesis method of the molybdenum disulfide nanosheets among two-dimensional transition metal dichalcogenide nanomaterials,as well as their physicochemical properties and their applications in analytical measurements.It also briefly describes the analytical objects and novelties,and gives some prospects of fluorescent molybdenum disulfide nanosheets in other areas.Chapter two: Fluorescent molybdenum disulfide nanosheets were hydrothermally synthesized by using sodium molybdate and thiourea as the starting materials.To analyze the morphology structure and chemical properties,some analytical characterization techniques like transmission electronmicroscopy,X-ray photoelectron spectroscopy,X-ray diffraction,scanning electron microscopy,UV-vis spectroscopy,and Fourier transform infrared spectroscopy,were performed.The optimum excitation and emission wavelengths of the fluorescent molybdenum disulfide nanosheets were located at 250 nm and 405 nm,respectively.Lead ion-doping into the fluorescent molybdenum disulfide nanosheets could result in the increase the fluorescence?FL?intensity,and the subsequent addition of sulfide ions into the lead-doped molybdenum disulfide nanosheets could remarkably quench the FL.On the basis of the principal,we designed a label-free FL “turn on-off” nanosensor for the detection of Pb²⁺ and S2-.Chapter three: We demonstrated that the fluorescent molybdenum disulfide nanosheets possessed the peroxidase-like activity,and could catalyze the oxidation of peroxidase substrate,o-phenylenediamine?OPD?,in the presence of hydrogen peroxide?H2O2?to produce a yellow products 2,3-diaminophenazine?DAPN?.Further addition of Fe²⁺ into the nanosheets led to the enhanced catalytic activity.The observation was exploited to develop a label-free colorimetric nanozyme sensor for detection of Fe²⁺.At the same time,the multivariate curve resolution-alternating least squares?MCR-ALS?was used to analyze the kinetic-spectral data during the reaction.It was found that the catalytic activity of Fe²⁺-enhanced molybdenum disulfide nanosheets was attributed to the increase in the reaction rate constant.Chapter four: The fluorescent molybdenum disulfide nanosheets can catalyze the oxidation of hydrogen peroxide with o-phenylenediamine to produce the yellow product 2,3-diaminophenazine with strong fluorescence.On the basis of the fluorescence properties of the product,we constructed a fluorescence catalytic sensor for Fe²⁺detection.At the same time,an advanced chemometrics model based on parallel factor analysis?PARAFAC?was used to eliminate background interferents in real lake water samples to achieve Fe²⁺ detection in the lake in the presence of unknown background interfering substances.The novelties in this thesis can be summarized as:?1?the fluorescent molybdenum disulfide nanosheets was used to build several highly sensitive and selective sensors for analysis of environmentally ions.?2?chemometrics tools were applied for treatment of data collected from the fluorescent molybdenum disulfide-based sensor,and the extracted results could be employed to explain the possible mechanism of the sensor response process,or to improve the performance of the sensor in the real samples.