Single-source Precursor Prepared By The Oxide And Sulfide Nanomaterials

Nanomaterials can exhibit unique physical and chemical property arising from their small size effect, quantum size effect, surface effect and macroscopic quantum tunneling effect, and thus they are expected to have many potential applications in electronics, catalysis, sensors, energy storage, solar cells, and nanodevices etc. It is generally accepted that the preparation of nanomaterials is fundamental to the development of nano-science and nano-technology. In recent decade, much attention has been paid to the preparation of nanomaterials with controllable size and shape, and a great progress has been achieved. In this paper, the basic concept, preparation methods, properties and development trends for nanomaterials were first reviewed. Then, a single-source method for nanomaterial preparation was investigated under microwave and solvothermal conditions and a variety of nanomaterials including ZnO, ZnS, PbS, NiS and Sb_2-xBi_xS₃ with various shape and size were successfully synthesized and characterized by XRD, SEM, FESEM, TEM, HRTEM and SAED etc. The optical properties of them were also studied.1. Using Zn(acac)₂·H₂O (acac = acetylacetonate) as a single-source precursor,the flower-, rod-, sheet- and spindle-like ZnO nanostructures have been synthesized via microwave method by adjusting the reaction time, surfactant and solvent. A possible formation mechanism for these ZnO nanostructures was proposed. The UV-Vis absorption spectrum and photoluminescence spectrum of these ZnO nanostructures were investigated.2. Hexagonal phase ZnS nanocrystals with the size of ⁵ nm were synthesizedby microwave thermolysis of a single-source molecular precursor of zinc diethyldithiocarbamate [Zn(DDTC)₂](DDTC=diethyldithiocarbamate) in ethylene glycol at low temperature. A strong blue emission band centered at about 426 nm was observed in the photoluminescence spectrum, which could be associated with the sulfur vacancy and interstitial sulfur lattice defects.3. PbS crystals with flower-, sheet-, cube-like morphology have been synthesized via microwave method by adjusting the reaction time, surfactant and solvent by microwave thermolysis of a single-source molecular precursor of lead diethyldithiocarbamate (Pb(DDTC)₂·5H₂O). The reaction mechanism together with the role of ethylenediamine was discussed. A strong blue-shifted absorption band centered at about 260 nm was observed in the UV-Vis absorption spectrum of the flower-like PbS crystals, which could be attributed to the quantum confinement possibly occurs near the tip of the PbS petals.4. The urchin-like nanostructures of NiS were successfully prepared usingnickel diethyldithiocarbamate (Ni(DDTC)₂) as a single-source precursor via a solvothermal treatment in presence of SDS as surfactant. The urchin-like pattern has a diameter of about 15 nm with acicular crystallites radiating from the center core. The average diameters of nanoneedles are about 20 nm. A possible formation mechanism for the NiS nanostructures was proposed. We found that both the solvent and the surfactant played important roles in the formation of urchin-like NiS.5. The flower-like nanostructures of Sb_2-xBi_xS₃(x=0.4, 1) were successfullyprepared using a mixed precursor of Sb(DDTC)₃ and Bi(DDTC)₃ at various ratios via a solvothermal process at 180℃. The flower-like architectures, with an average diameter of ⁴μm, were composed of single-crystalline nanorods with orthorhombic structures. The optical absorption properties of the Sb_2-xBi_xS₃ nanostructures were investigated by UV-Visible spectroscopy, and the results indicate that the Sb_2-xBi_xS₃compounds are semiconducting with direct band gaps of 3.0 and 3.2 eV for x=0.4 and 1.0, respectively. On the basis of the experimental results, a possible growth mechanism for the flower-like Sb_2-xBi_xS₃ nanostractures is suggested.