The emission wavelength of the CdS/ZnSe NSs can be changed from 568 to 589 nm for a fixed core radius. Because of a large offset of band edges at the core/shell interface, fabricated nanocrystals (NCs) exhibited a relatively low spectral overlap between emission and absorption profiles, with associated Stokes shifts of up to 70nm. | Nguyễn Xuân Ca và Đtg Tạp chí KHOA HỌC & CÔNG NGHỆ 96(08): 45 - 48 SYNTHESIS AND CHARACTERIZATION OF TYPE-II CdS/ZnSe CORE/SHELL NANOSTRUCTURES Nguyen Xuan Ca1*, Nguyen Trung Kien1, Vu Thi Kim Lien2, Nguyen Xuan Nghia3 1 3 College of Science – TNU, 2 College of Education – TNU Institute of Materials Science, Vietnam Academy of Science and Technology SUMMARY High-quality type-II CdS/ZnSe core/shell nanostructures (NSs) were synthesized by chemical method. Our synthesis involves fabrication CdS core particles that are subsequently overcoated with a layer of ZnSe in the noncoordinating solvent. An efficient spatial separation of electrons and holes between the core and the shell was observed by heterostructures. The emission wavelength of the CdS/ZnSe NSs can be changed from 568 to 589 nm for a fixed core radius. Because of a large offset of band edges at the core/shell interface, fabricated nanocrystals (NCs) exhibited a relatively low spectral overlap between emission and absorption profiles, with associated Stokes shifts of up to 70nm. Key word: spatial separations, nanostructures, semiconductor, reorganization energy. INTRODUCTION* Colloidal heterostructure semiconductor NCs were synthesized from multiple materials with different properties into a single nanoscale object, where the spatial localization of carriers can be precisely controlled by anipulating shapes and sizes of individual components [1,2]. Recently, considerable progress was made in the synthesis of type- II heterostructure NCs [3], that tends to spatially separate photoexcited electrons and holes in different parts of a composite NCs. These core/shell NCs are made of two semiconductor materials which both the conduction and valence bands of component lie lower in energy than the corresponding bands of the other component. As a result, one carrier is mostly confined to the core, while the other is mostly confined to the shell. The type-II NCs are expected to have many new properties that are
