Synthesis, Characterization And Properties Of The One-dimensional ZnSe Nanocrystals And Its Mn Doped Counterpatrs

ZnSe nanocrystals have been extensively used for decades to do some detection,catalysis and luminescence, due to its low toxicity, wide band gap and strong quantumconfinement effect. One-dimensional nanocrystals are always the good candidates inconstruction of nano-optoelectronic device, according to its transportation of carriers at theminimum dimension. Transition metals in doped semiconductor nanocrystals have someimpacts on band configuration, carriers transportion and some other physical properties ofhost materials. Combinations of these two or three features will lead us to the functional andpractical materials which meet the needs to be conformed to the present. Otherwise, the facile,enviroment friendly and economical synthesis strategies of the mutil-functional materials arethe indispensible components for the extensive applications.Ultrathin ZnSe nanorods in the cubic phase have been synthesized by the reaction ofselenium and zinc oleate in oleylamine for30min at240. These nanorods showed anaverage diameter of2.4nm, which is much smaller than the Bohr size of bulk ZnSe. Thus,they exhibited a remarkable quantum size effect in terms of their optical properties. TEM,HRTEM, XRD and XPS were used to confirme the structure and composition of the products.The formation of the ultrathin nanorods could be attributed to the oriented attachmentmechanism, which was supported by the structure of the nanorods and the controlexperiments. The ultrathin nanorods were transferred into an aqueous solution by ligandexchange. The performance of these nanorods as a catalyst was examined, using thephotodecoloration of methyl orange as a model reaction. The ascorbic acid was used as thehole scavenger to remove the photogenerated holes and oxidizing species on the catalystsurface. It was found that the ultrathin nanorods possessed better photocatalytic activities thanconventional ones and titanium dioxide (P25). The excellent photocatalytic performance wasattributed to the strong quantum confinement effect and the large specfic surface area ofultrathin nanorods.The one-dimensional Mn-doped ZnSeS nanocrystals are synthesized through a facileone-pot reaction under mild experiment conditions. These ZnSeS nanocrystals with adiameter of2-4nm are in a structure of cubic phase. EPR spectra and PL spectra confirm thesubstitute tetrahedral sites of Mn2+ions in the host nanocrystals, based on the correspondinghyperfine splitting constant and emission band. The temporal evolution of UV-Vis absorptionspectra and PL spectra indicates the growth-doping mechanism for the formation of the dopednanocrystals. Surface coating of these nanocrystals with a shell further increases the quantum yield up to35%.And the dual-function role of1-dodecanethiol is confirmed in the formationof the elongated Mn-doped ZnSeS nanocrystals.Considering the unique function of1-dodecanethiol presented in the synthesis of theanisotropic Mn doped ZnSeS nanoparticles, several control experiments were conducted. Theresults confirmed the effect of1-dodecanethiol on ZnSeS growth and doping, proved that theintroduction of sufficient1-dodecanethiol can suppress the generation of ZnO effectively.Proposed reaction pathway and structures of the precursors were analysed under the view ofinorganic chemistry. DFT calculation showed that the total energy of thiol-metal compoundswere lower than amine-metal compounds.