Gas Sensor And Microdroplet Sensor Based On Monolayer Molybdenum Disulfide

Because of its excellent optical and electrical properties,two-dimensional materials have aroused the research enthusiasm as soon as they were discovered.Single layer molybdenum disulfide（MoS₂）is a direct band gap two-dimensional crystal.Its excellent physical and electrical properties and excellent band gap width can effectively make up for the shortcomings of graphene in the field of nano electronic devices,and it is widely used in catalysis,transistors,optoelectronic devices,integrated circuits and other fields.Therefore,it is essential to obtain high quality,large size monolayer MoS₂.Based on the realization of high quality and large size single layer MoS₂,this paper deeply studies the influence of environmental dielectric shielding effect on the photoemission spectrum of monolayer MoS₂,and proposes a reasonable droplet identification and evaporation sensing detection technology,which provides a new development direction for the research and development of droplet evaporation sensors in the future.In addition,PET flexible gas sensor is constructed to study the application of single layer MoS₂ in gas sensing.1 The preparation of high quality and large area monolayer MoS₂ was studied.By comparing the advantages and disadvantages of various preparation methods,combined with the existing conditions in the laboratory,this paper chooses the chemical vapor deposition（CVD）method to achieve the synthesis of single layer MoS₂.Through the optimization of various conditions in the synthesis process,a large area of single layer MoS₂ can be efficiently obtained,the size of up to tens of microns.Through the salt-assisted optimization process,a single crystal of MoS₂ with smooth,clean surface and stable performance was obtained,which provided the material basis for the subsequent research and application of single layer molybdenum disulfide.2 Based on the photoluminescence characteristics of single layer MoS₂,an optical evaporation sensor is realized through the dielectric shielding effect of microdroplet.The dielectric constant of microdroplet is related to emission intensity,maximum half-peak width of exciton,photon energy and intensity ratio of exciton,and can be used to identify the type of liquid of microdroplet.In addition,the refractive index has a significant effect on the PL intensity collected during the evaporation of volatile organic compound（VOC）microdroplets.Based on the above findings,a theoretical model of microdroplet evaporation sensor based on dielectric shielding effect is proposed in this paper,and verified by using the finite-difference time-domain method and the finite element method.Finally,a non-contact,high-precision and miniaturized fluorescence probe microdroplet identification and evaporation monitoring technology was developed.3 We constructed a PET based gas sensor for a single layer of molybdenum disulfide electroplated electrode by UV litho writing,and constructed a test platform for the gas sensor.By applying periodic bending strain to the sensor in the ambient air atmosphere at normal temperature,the open-circuit voltage signal could be observed in the external circuit to test its flexible characteristics and piezoelectric effect.In addition,the influence of light on gas sensing is studied by measuring the resistance of digital source meter,and the ultraviolet enhanced gas sensitive characteristics of single layer MoS₂ gas sensor are explored.A gas sensor with high selectivity and flexible light enhanced is proposed.