| Two-dimensional layered nanomaterials such as graphene and two-dimensional chalcogenides have shown excellent performance in fields such as electronic devices,photonic devices,photocatalysts,photoelectric sensors,and solar cells.As two typical materials in two-dimensional chalcogenides,The band gaps of MoS2 and Bi2S3 are between visible and infrared light and have potential application in photoelectric device and photoelectric chemistry fields.In this thesis,our work focuses on the preparation and optoelectronic properties of MoS2 and Bi2S3 and the main contribution can be divided into four parts as following:（1）The development,preparation methods,and photoelectric properties of two-dimensional layered nanomaterials have been summarized.We introduce both the zero-bandgap graphene and the adjustable bandgap two-dimensional layered chalcogenides.Then we focuses on the MoS2 and Bi2S3 layered materials,which includes both their structures and optoelectronic properties.（2）Two dimensional MoS2 nanosheets have been obtained by liquid phase exfoliation method.Transmission electron microscopy,atomic force microscope images showed the obtained nanosheets are 2-4 layers structures.Scanning electron microscope and Raman spectra proved MoS2 films prepared by filtration method have good quality and stacking structure,which lays the foundation for the application of MoS2 photoelectrode.（3）We have efficiently exfoliated layered Bi2S3 from bulk precursor based on enthalpy of mixing theory.It was found that 10%（volume ratio）deionized water in 90%isopropyl alcohol is the best solvent for the exfoliation of layered Bi2S3.These results are consistent with the absorbance spectra.Transmission electron microscopy,atomic force microscope images prove that the obtained Bi2S3 nanosheets had 1–3 quintiple layers.Bi2S3 films demonstrated sensitive photoelectric response with the rise and decay response of photocurrent on the microsecond scale under the visible light excitation,which are consistent with the density of state and partial density of state of bulk and one-quintuple layer Bi2S3 calculated by first-principle calculation.This suggests a strong light-substance interaction occurs from the microscopic point of view.The results suggest that Bi2S3 has the potential applications in photoelectric detection and solar energy conversion devices.（4）High quality MoS2 can be synthesised by vapor phase deposition method,but the relevant chemical mechanism is more complicated.We chose MoO2 as precursors,which has high evaporation temperature and more conducive for in situ growth of MoS2.First,as-prepared rhomboidal MoO2 crystals have large sizes and high crystallinity,the size lengths of which can exceed 200μm and thickness ranges between 20–100 nm.Then,we have proposed a depositing mechanism based on disproportionation and physical vapor deposition was proposed to explain the MoO2 deposition process which is supported by experiment.Finally,uniform MoS2 films can grow on surfaces in suitable sulfuration process.The fine crystallinity,low evaporation rate and conductive property of these Mo O2crystals make them potential alternative substrate for growth of 2D chalcogenides MoX2（X=S,Se,Te）and MoO2/MoS2（X=S,Se,Te）heterostructures. |
