Shape Controlled Synthesis? Assemble And Characterizations Of Transition Metal Chalcogenides Nanocrystals

Nowadays,the controlled synthesis and tailoring of the morphologies in chalcogenide transition metal nanocrystals?NCs?and heterostructures?such as zero dimensional nanocrystals,two dimensional nanosheets?are the research hotspots due to their attractive application in the new photocatalytic materials and electrode materials of new energy battery?such as supercatacitor?.Since the photocatalytic and electrochemical performances of the nanocrystals are strongly dependent on their sizes,morphologies,constituents and assembly,therefore,synthesis of nanocrystals with morphologies preciously controlled and further studying the relationship of“micro-nano structures-performance”are the main scientific issues in our research.In this paper,we use the CdS_xSe_1-x?x=0¹?,Ni₃S₄ and their heterogeneous or homogeneous self-assembly sturctures as research objects.On the basis of the controllable preparation of zero-dimensional nanocrystals and two-dimensional nanosheets,large scale self-assembly was realized based on liquid phase method.The morphologies,constituents,and optical properties of the as prepared samples were characterized.In addition,their photoelectrochemical,hydrogenation and electrochemical performences were further studied.1.Monodispersed CdS_xSe_1-x NCs with tetrahedral morphology and different S/Se ratios were prepared based on high temperature organic phase method by controlling the amount of S and Se precursors.The diameter of the as-prepared CdS_xSe_1-x NCs is about 5 nm.The morphologis of the NCs were confirmed by TEM and the optical properties were verified through UV-Vis-NIR absorption spectra and fluorescence spectroscopy.Typically,CdS NCs were characterized via HRTEM,STEM and XRD.Photocurrent response was employed to characterize the properties of the CdS_xSe_1-x NCs.As it indicates,the photocurrent response of CdS_xSe_1-x NCs film enhanced gradually with the increasing of the Se.2.Au/CdS_xSe_1-x heterostructures have been studied well.With the evolution of composition in CdS_xSe_1-x nanocrystals,the specific growth of Au nanocrystals with different sizes grown on anisotropic nanocrystals were realized.Because of the close contact between the Au and the CdS_xSe_1-x NCs,and efficient electron transfer from CdS_xSe_1-x to Au in Au/CdS_xSe_1-x HNCs,the enhanced photocurrent have been realized compared with CdS_xSe_1-x without Au decorating.Also,the as-prepared Au/CdS_xSe_1-x anisotropic heterogeneous NCs exhibited enhanced photocatalytic hydrogen evolution compared with CdS_xSe_1-x NCs.3.Three-dimensionally micro-and nano-sized spheres were prepared through the emulsion-based bottom-up self-assembly method based on monodisperse CdS_xSe_1-x nanocrystals?NCs?with tailoring compositions.UV-Vis absorption and IPCE measurements revealed the enhanced light harvesting and incident photon to current efficiency of the assembled CdS_x Se_1-x spheres compared with their constituting NCs.The quenching of photoluminescence after the assembly of CdS_xSe_1-x-x NCs may demonstrate the likely suppressed electron-hole recombination.The above findings were coincided with the remarkably improved H₂ evolution activities observed for the well-assembled CdS_xSe_1-x nanospheres in photocatalytic water splitting,indicating the importance of the alternative strategy to design advanced semiconductor photocatalysts based on architectural engineering.4.Three-dimensional?3D?Ni₃S₄ nanosheet frames,Ni₃S₄ nanosheets,nanorods,Ni₃S₂nanocubes are synthesized via a facile solvothermal method.Compared with flat Ni₃S₄ sheets,3D Ni₃S₄ nanosheet frames show a high specific surface area,high stability,and higer supercapacitor performance.In addition,these 3D Ni₃S₄ nanosheet frames show enhanced cycling stability.We change the oleic acid?OA?to oleylamine while keep other conditions the same,the Ni₃S₄ nanorods with preferable super-capacitor performance can be obtained.By substantial increasing the ratio of n-dodecanethiol?DDT?to OA,the Ni₃S₂ nanocubes with entirely different crystal form,sizes and morphologies can be obtained.