| In the context of the emergence of"intelligent"society,both for the implementation of Air Pollution Prevention and Control Action Plan based on the concept of sustainable development and the Internet of Things technology represented by smart home and intelligent production,an urgent demand for low-power and high-performance gas sensors is desired.However,the current commercial sensors used for NO2 and other gas detection still have some problems,such as high operating temperature and low sensitivity.Therefore,it is urgent to develop advance gas sensing materials to prepare high performance NO2 sensors with room temperature and high sensitivity.Among the gas sensing materials,two-dimensional metal sulfide materials are widely used in NO2 sensing research,due to their unique properties,such as large specific surface area and super surface activity.Among them,Sn S2,as an emerging two-dimensional metal sulfide material with a greater electronegativity and stronger gas adsorption ability,has become one of the hotspot materials for the preparing of high-performance NO2 sensor.However,the research on NO2 sensing of Sn S2 is still in its infancy,and there are still some key issues that need to be resolved.For example,Sn S2 is difficult to achieve NO2 sensing at room temperature due to its poor electrical conductivity;the structure-activity relationship between the modified structure of Sn S2 and its gas-sensing properties is still ambiguous.Therefore,in order to solve the above problems,this dissertation used defect engineering,heterogeneous structure construction and other structural improvement strategies to rationally modify the Sn S2 material,relized the room-temperature sensing of NO2,and analyzed its gas sensing mechanism to clarify the structure-activity relationship between the modified structure of Sn S2 and its gas-sensing properties.The four parts of the research work are as follows:First,with the help of defect engineering,the electronic structure of the material is adjusted by the synergy of S vacancy and the expanded-interlayer.The room-temperature sensing of NO2 based on Sn S2 material is realized.This study opens a new avenue for designing room-temperature operating NO2 sensors based on Sn S2materials.By adding Al(NO3)3·9H2O during the synthesis of Sn S2 materials with ethylene glycol as solvent,both S vacancy and the expanded-interlayer were introduced into Sn S2 material with the substitution doping of Al atoms and the intercalation of ethylene glycol.Due to the existence of defects such as S vacancies and expanded-interlayers,the prepared material has better conductivity than the pristine Sn S2.Moreover,according to the in-situ test based on NAP-XPS,the XPS peak position of this material moved significantly during the adsorption of NO2,revealing the strong interaction between the material and NO2 molecules.Therefore,the sensor based on this material can realize NO2 sensing at room temperature and has a sensitivity of 173%toward 1 ppm NO2.Meanwhile,the corresponding performance comparison experiments and theoretical calculation analysis show that the presence of S vacancies and the expanded-interlayers play a major role in the realization of NO2 sensing at room temperature.Secondly,based on the understanding of heterostructure,Sn S2/Sn S heterojunction with an accumulation layer was constructed.The prepared material based on Sn S2/Sn S heterojunction had better conductivity than the pristine Sn S2,and could relize high-sensitivity NO2 sensing at room temperature.This research provides a new route for the reasonable construction of heterojunction.Through the embellishing Sn S nanoparticles on Sn S2 microflowers by a one-step solvothermal method,Sn S2/Sn S heterojunction material with an electron accumulation layer was prepared.Due to the proper band structure of Sn S2 and Sn S,electrons were transferred from Sn S to Sn S2,which caused the accumulation of electrons on the side of Sn S2,thereby improving the conductivity of the material and enhancing the adsorption of NO2.Therefore,Sn S2/Sn S sensor capable of detecting NO2 at room temperature was obtained.In addition,the obtained Sn S2/Sn S sensor exhibited a high sensitivity of 237%to 1 ppm NO2 and a short response/recovery time(311/748 s).Furthermore,based on the previous part of the research,from the perspective of the optimization of heterojunction interface,a 2D/2D g-C3N4/Sn S2 heterojunction was constructed to further improve the room-temperature NO2 sensing performance,and the enhancement of 2D/2D heterojunction on the NO2 sensing performance was studied.By using a solvothermal synthesis method,the 2D g-C3N4 were decorated on the leaves of Sn S2 microflowers,and result in the preparation of g-C3N4/Sn S2materials with 2D/2D heterojunctions.Taking advantage of the larger junction area of the 2D/2D heterojunction,a large number of electron transmission channels were established,which not only promoted the transfer of electrons from g-C3N4 to Sn S2,and finally improved the electrical properties of the material,but also improved the adsorption ability of the material.Therefore,the constructed 2D/2D g-C3N4/Sn S2material can not only detect NO2 at room temperature,but also exhibited extremely high sensitivity(503%)and short recovery time(166 s)to 1 ppm NO2.Finally,a room-temperature NO2 sensor with high sensitivity and rapid response/recovery was prepared based on Sn S2 by taking advantage of the synergistic effect of heterostructure and illumination assistance for improving the response and recovery characteristics of the material.Through a one-step solvothermal synthesis method,Sn S2/Ti O2 heterojunction was prepared,and its gas-sensing performance under the assistance of 525 nm light was tested.The results shown that,due to the synergistic effect of heterojunction and illumination assistance,the sensor can relize the high-sensitivity(526%to 1 ppm NO2)and fast response/recovery(43/102 s)NO2sensing at room temperature.In addition,the flexible sensor prepared based on this material had a relatively stable sensitivity value in four different bending modes,indicating the application potential in portable and wearable devices. |
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