The Preparation And Optical Properties Of Molybdenum Disulfide Quantum Dots And Their Composites

Molybdenum disulphide?MoS₂?,as a typical kind of TMDs nanomaterials exhibited many unique properties and have been widely used in electrocatalysis,hydrogen production,and optoelectronic devices.Due to the excellent edge and quantum confinement effects,MoS₂quantum dots?MoS₂ QDs?enhanced or got some new properties,when the size of MoS₂reducing less than 20 nm.At present,the preparation methods and optical properties of MoS₂QDs have been studied extensively.However,most of the synthetic methods of MoS₂ QDs currently have low water-solubility,low quantum efficiency,low biocompatibility and so on.Based on the background,this paper would be divided into as the following three parts work,introduced the synthesis methods,performance characterization,and application of MoS₂QDs and composite materials.?1?We synthesized the blue fluorescent MoS₂ QDs through the bottom-up hydrothermal step by using sodium molybdate?Na₂MoO₄·2H₂O?and glutathione?GSH?as Mo and S sources,the prepared MoS₂ QDs shown high water-soluble,stability,and quantum efficiency.Moreover,we also characterized the size,surface structure,and luminescent properties of as-prepared MoS₂ QDs.Here,GSH was not only a source of sulfur,but also worked as a surface passivation agent for the prepared MoS₂ QDs providing amino functional groups,which made MoS₂ QDs have high water solubility and stability.This method also successfully synthesized WS₂ quantum dot?WS₂ QDs?.We found that the fluorescence intensity of MoS₂QDs decreased with the increasing concentration of H₂O₂,so the MoS₂ QDs can be used as a detection platform of H₂O₂ concentration.Moreover,as a result of that the glucose oxidase?GOx?selectively oxidize glucose to produce H₂O₂,the MoS₂ QDs could be used as a sensitive and selective glucose quantitative detection sensor.The fluorescence intensity of MoS₂ QDs shown an ideal linear correlation for glucose in the range of 0-500?M,and had the detection limit of 5.16?M.In addition,we have also successfully applied this method to detect glucose concentration in fetal bovine serum.The above results shown the synthesized MoS₂ QDs have the potential for the detection of glucose concentration in diabetes research and clinical diagnosis.?2?We synthesized the functional C ys-MoS₂ QDs by using L-cysteine?Cys?as the surface modifier on the basis of MoS₂ QDs.In the presence of C ys,MoS₂ QDs introduced carboxyl and amino group which made the C ys-MoS₂ QDs have good biocompatibility,water solubility and stability.Significantly,because of the efficient chelation enhanced fluorescence?CHEF?and electron radiation features,the C ys-MoS₂ QDs could be used as the“turn-on”type of Al³⁺and the“turn-off”type of Fe³⁺fluorescence dual mode sensor.We also successfully applied the sensing system in tap water and lake water to detect Al³⁺and Fe³⁺simultaneously,and had good linear dependence relation.Finally,the synthesized C ys-MoS₂QDs shown good biocompatibility and low toxicity by the MTT experiment in He La cells and could be applied in cell imaging in organisms.The all above results demonstrated that the functional Cys-MoS₂ QDs could be used as a substitute of traditional fluorescent probes in biomarkers and sensing.?3?By a simple heating reflux used MoS₂ QDs and polyvinyl alcohol?PVA?,we prepared the MoS₂ QDs-PVA composite membrane inspired by the synthesis of fluorescent carbon?CDs?and poly?methyl methacrylate??PMMA?polymer compound,which had optical properties,transparent and collapsible.The MoS₂ QDs acted as the functional filler and made the composite membrane have the similar optical properties of MoS₂ QDs.The PVA as the polymer matrix gave the composite membrane a certain mechanical properties,so that the functional MoS₂ QDs-PVA composite membrane was flexible and could be folded into any shape.The experiment results shown the MoS₂ QDs-PVA composite membrane had better mechanical stability,extensibility?more than 600%strain and 38 MPa tensile stress?,high thermal stability and storage stability.More importantly,we found that the MoS₂QDs-PVA membrane possessed the fluorescence response to p H based on the fluorescence quenching of MoS₂ QDs solution to p H,so we applied the MoS₂ QDs-PVA composite film as“p H test paper”to test the value of p H on the bacterial culture solution.The successful application of MoS₂ QDs-PVA as the“pH test paper”shown that the MoS₂ QDs-PVA visual detection of pH had broad application prospects in the food safety and other important areas.We believed the synthesis of functional fluorescent MoS₂ QDs-PVA composite membrane would laid the foundation of TMDs materials in optoelectronic devices,such as light-emitting LED devices,as well as provided certain theoretical basis for the synthesis of a variety of fluorescent,transparent and folding light-emitting polymer composite membrane.