Preparation And Humidity Sensing Properties Of Molybdenum Disulfide And Its Composites

As a typical representative of two-dimensional materials,MoS₂ were widely used in optoelectronic devices,new energy storage and functional sensing devices and other fields.As one of the functional sensing devices,humidity sensor were widely used in environmental monitoring,industrial production,weather monitoring,food and drug storage areas.Therefore,the research on humidity sensor is particularly important.In this paper,ZnO quantum dots?QDs?,SnO₂ QDs,MoS₂ nanosheets,MoS₂@ZnO QDs nanocomposites and MoS₂@SnO₂ QDs nanocomposites were prepared by chemical method and hydrothermal method.The humidity sensor were fabricated by using the above materials as the moisture-sensitive material,and the humidity-sensitive performance of the corresponding humidity sensor was analyzed.The main research contents include the following two parts.1?ZnO QDs were prepared by chemical method.MoS₂@ZnO QDs nanocomposite structures were prepared by two-step method,that is,as chemical method combined with hydrothermal method.The surface morphology,crystal structure and material composition of the prepared materials were characterized by XRD,SEM,EDS and TEM.The results show that the ZnO material is a typical quantum dot structure and the particle size distribution is concentrated.The MoS₂ material has obvious lamellar structure,MoS₂@ZnO QDs is a composite structure and rich in pores.MoS₂ and MoS₂@ZnO QDs humidity sensors were fabricated by using the above materials.The humidity sensitivity of MoS₂ and MoS₂ @ ZnO QDs humidity sensors was tested by intelligent humidity test system.The results show that the optimum operating frequency is 100 Hz in the frequency range of 10 Hz 100 kHz.At room temperature and the operating frequency of 100 Hz and within the relative humidity?RH?range of 11% 95%,the change of impedance value for the MoS₂@ ZnO QDs humidity sensor is approximately four orders of magnitude larger than that of the MoS₂ asenosr.In response time,the MoS₂@ZnO QDs humidity sensor is significantly shorter comparing with that of the pure MoS₂ humidity sensor,from47 s to 1 s,and the recovery time is shortened from 65 s to 20 s.Compared to pure MoS₂ humidity sensor,the MoS₂@ZnO QDs humidity sensor achieves ultra-fast response and faster recovery.We can found that the humidity sensing improvement of MoS₂@ZnO QDs composite can be explained by the introduction of quantum dot structure.2?The SnO₂ QDs were prepared by hydrothermal method.The MoS₂@ SnO₂ QDs nanocomposites were prepared by two-step hydrothermal method.The surface morphology and crystal structure of the prepared materials were characterized by XRD,SEM and TEM.The results show that the SnO₂ material is a typical quantum dot structure,while the MoS₂@SnO₂ QDs is a composite structure,and it is rich in pores.MoS₂@SnO₂ QDs humidity sensor was fabricated by using the above materials.The humidity sensitivity of MoS₂@SnO₂ QDs humidity sensor was tested by intelligent humidity test system.The results show that the optimum operating frequency is 100 Hz in the frequency range of 10 Hz 100 kHz.At room temperature,the impedance change of MoS₂@SnO₂ QDs humidity sensor is close to 5 in the range of 11% 95% RH at the operating frequency of 100 Hz.The MoS₂@SnO₂ QDs humidity sensor is significantly shorter in response time of the pure MoS₂ humidity sensor,from 47 s to 4 s,and the recovery time is improved from 65 s to 30 s.Compared to pure MoS₂ humidity sensor,the MoS₂@SnO₂ QDs humidity sensor achieves ultra-fast response and faster recovery.We summarize humidity mechanism of the MoS₂@SnO₂ QDs humidity sensing composite.