| With the development and progress of the human society,the environmental pollution has been an increasing issue.In particular,the air pollution closely related to breathing and survival of human has seriously affected our health and life.Therefore,it is great important and urgent to test toxic gases and improve the air environment.Gas sensors can be used to detect and quantify toxic gases and organic volatiles,and play an are essential role in many different areas,such as emissions control,military and public safety,industrial and agricultural production,environmental monitoring and medical diagnostics.Such functionalized materials as metal oxide,conductive polymer and carbon nanotubes(of CNTs)have been explored in the research and exploration of gas sensors.However,it should be acknowleged that there are they still have problems such as high reaction temperature,low sensitivity,and long response time recovery in sensor applications.Therefore,there is an urgent need to develop a new gas sensing technology with high sensitivity,low operating temperature,and fast response recovery time.Multi-dimensional nanomaterials,especially two-dimensional and three-dimensional nanomaterials,have received extensive attention in sensor applications due to their multiple active sites,rapid electron mass transfer capability,and large surface-to-volume ratio.In this thesis,the two-dimensional and three-dimensional layered nanomaterials based on Mo,Zn have been synthesized and modified by doping and compounding methods,and the sensor performance has been investigated as well.Mainly includes the following:1.Two-dimensional MoSe2 nanosheets with multiple atomic layer was prepared by solution-phase method quickly and easily,XRD,TEM,HTEM and XPS were used to characterize the composition and structure of the ultrathin nanosheet.The real-time response of NH3 show that the flower-like ultra-thin MoSe2 nanosheet is a typical p-type sensor materials,and the real-time detection of NH3 can be realized at room temperature,by the way its minimum detection concentration can reach 10 ppm.Finally,the experiments showed that the two-dimensional flower-like MoSe2 nanosheets have high selectivity fast response recovery and strong repeatability.This proves that MoSe2 has a promising application as a room temperature gas sensitive material.2.In this thesis,we successfully synthesized a novel hierarchical oxygen-doped MoSe2 hierarchical nanosheet(MHS)through Solid-phase synthesis method and studied its sensing properties.A series of characterization methods were used to further verify the successful doping of oxygen,and it was also proved that the MHS retained its original morphology and structure after doping.In addition,it was found that the MHS could realize real-time detection of trace TMA and the detection range was from 10 ppb-500 ppm.By the way,the sample also own the advantages of low working temperature(room temperature),low detection conditions(in the air),high selectivity and strong stability.In conclusion this work opens up a new direction for the rational design of high-performance gas sensors under a normal temperature air environment.3.A novel synthesis method was reported,in this methed the MoSe2-SnO2 nanocomposite was obtained through regulating the relative proportion of MoSe2 and SnO2,and the sensing properties of NO2 at room temperature were investigated.The structure indicates that the MoSe2-SnO2 nanocomposite can be explore for the detection of the low concentration of NO2 in air at room temperature.The detection limit was calculated to be 5 ppb with the good selectivity and stability for NO2.The results of this study indicate that the doping of materials can effectively control the gas sensing properties of MoSe2 nanosheets in the application field of sensors,4.Flower-like hierarchical structures with the porous single-crystalline ZnO nanosheets(FHPSCZNs)were synthesized based on a one-pot wet-chemical method followed by an annealing treatment,which combined the advantages between flower-like hierarchical structure and porous single-crystalline structure.XRD,SEM and HRTEM were used to characterize the synthesized FHPSCZN samples.The sensing properties of the FHPSCZN sensor were also investigated by comparing with ZnO powder sensor,which exhibited higher response and shorter response and recovery times.The sensing mechanism of the FHPSCZN sensor has been further analyzed from the aspects of electronic transport and gas diffusion.In summary this paper develops a method to detect metal oxide gas sensor with low response recovery time.5.Ag nanoparticles were successfully decorated onto ultra-thin poroussingle-crystalline(UTPSC)ZnO nanosheets via a solvent reduction method.The as-prepared products were characterized by scan-ning electron microscopy(SEM),transmission electron microscopy(TEM),energy dispersive spectrum(EDS),X-ray diffraction(XRD),X-ray photoelectron spectrometry(XPS)and photoluminescence(PL)measurements.It can be found that the UTPSC ZnO nanosheets with a few micrometers in length and 8-10 nm in thickness were uniformly coated with Ag nanoparticles.The as-prepared products combined the advantages of porous structure,single-crystalline,ultra-thin thickness and Ag decoration,which definitely resulted in a dramatically sensing performance in ethanol detection.The lowest detection concentration was 1 ppb,which is the lowest detection limit to our knowledge.It is expected that the Ag-decorated UTPSC ZnO nanosheets may provide a new pathway to develop advanced nanomaterials for the application of trace gas detection. |
PDF Full Text Request