The Gas Sensing Properties Of Two-dimensional MoS₂/SnS₂

Gas sensors are closely related to people's production and life.They play a very im-portant role in the detection of various toxic and harmful gases,and the monitoring of the quality of food and living environment and so on.Therefore,high performance gas sensors have became the center for studies of home and abroad in recent years.In our work,we have prepared few-layer MoS₂ nanosheets,SnS₂ nanoparticles and MoS₂/SnS₂ nanocompo-sites by mechanical exfoliation method,hydrothermal method,etc.In order to study the gas sensing properties of the three sensitive materials,we make the corresponding gas sensors and analyze their gas-sensitive working mechanism.The main research contents are sum-marized as the following three parts:1.The few-layer MoS₂ nanosheets are synthesized by mechanical exfoliation method.The morphologies,molecular structure and the gas sensor surface are characterized by field-emission scanning electron microscopy?FE-SEM?,transmission electron microscopy?TEM?,Raman spectra,atomic force microscope?AFM?,biological microscope.The cor-responding gas sensor is fabricated to investigate its gas sensing properties at room temper-ature.The few-layer MoS2 nanosheets exhibit high response against NO2 at room tempera-ture and the quick and complete recovery behaviors?the recovery time of 2 s,the recovery rate greater than 97%?.Based on density-functional theory?DFT?,the calculation shows that the excellent performances at room temperature are mainly attributed to a weak van der Waals interactions,that is to say,the physical adsorption is the main factor for the adsorp-tion of NO₂ on MoS₂ surface.The high response of the gas sensor to NO₂ gas is attributed to size effect from extremely thin thickness of few-layer MoS2 nanosheets,and the electrons of all over the sensing channels?including the bridging contact and the few-layer MoS₂nanosheets itself?can be affected by the adsorbed NO₂.2.First of all,the SnS₂ nanoparticles are successfully synthesized by the hydrothermal method.The crystal structure and surface morphologies of SnS₂ nanoparticles are charac-terized by X-ray diffraction?XRD?,FE-SEM and TEM.The corresponding gas sensor is fabricated to investigate its NO2-sensing performance at room temperature.The SnS2 nano-particles exhibit good stability and complete recovery characteristics for NO₂ room temper-ature detection.At the whole NO₂ gas concentration,the recovery rate is greater than 98%.NO₂ gas molecules can completely desorb due to their low adsorption energy.Then,we successfully synthesized MoS₂/SnS₂ nanocomposites by the mechanical ex-foliation method combining with hydrothermal method.The surface morphologies and crystal structure of MoS₂/SnS₂ nanocomposites are characterized by FE-SEM and Rama spectra.The few-layer MoS₂ nanosheets,SnS₂ nanoparticles and MoS₂/SnS₂ nanocompo-sites are fabricated into gas sensors to investigate their gas sensing properties.The results show as follows:The response value of the MoS₂/SnS₂ nanocomposites gas sensor is about6 for 5 ppm NO₂ room temperature detection,3 times of the SnS₂ nanoparticles gas sensor.The response and recovery times of the MoS₂/SnS₂ nanocomposites gas sensor are 28 s and3 s,and the recovery time is greatly shorter than that of SnS₂ nanoparticles gas sensor?30 s?.In addition,the stability of MoS₂/SnS₂ nanocomposites gas sensor is stronger than that of the MoS₂ gas sensor.Therefore,the enhanced gas sensing properties of MoS₂/SnS₂ nano-composites are ascribed to the advantages between MoS₂ and SnS₂.