Synthesis And Mechanism Of Surfactant-assisted Nano-materials Control

With the development of nanotechnology, the synthesis of novel and high quality inorganic nanomaterials with unique chemical and physical property has become a major interdisciplinary reseach area in recent years. In this thesis, we selected several kinds of inorganic materials, including chromate salts, tungstate salts, sulfide lead, and metals such as silver, copper, and palladium. Various morphologies such as nanorods, hollow nanospheres, dendrites, star-shaped nanocubes, and metallic core-shell nanostructures, have been successfully synthesized via surfactant-assist process. The formation mechanisms were proposed and their optical properties were investigated. In Chapter 1, we briefly introduced the history and recent work in the field of nanotechnology. Some kinds of methods for th synthesis of nanomaterials, such as aqueous-phase, nonaqueous-phase, hydrothermal / solvothermal methods, and templated method, have been introduced clearly. The role and application of the surfactant in the synthesis of nanomaterials were also illustrated in this chapter.As one of the semiconductor compounds, PbS is an important Ï€-Ï€ semiconductor material with a narrow band gap energy (0.41 ev) and large excition Bohr radius (18 nm). In Chapter 2, well-defined single-crystalline PbS nano- and microstructures including dendrites, multipods, truncated nanocubes, and nanocubes were synthesized in high yield by a simple solution route. Novel star-shaped PbS dendrites with six symmetric arms along the <100> direction, each of which shows one trunk (long axis) and four branches (short axes), have been achieved using Pb(AC)2 and thioacetamide(TAA) as precursors, under the molar ratio Pb(AC)₂/TAA=2/1, at initial reaction temperature 80℃, refluxing for 30 min at 100℃, in presence of cetyltrimethylammonium bromine (CTAB). The "nanorods" in each branch are parallel to each other in the same plane, and are perpendicular to the trunk. The truncated nanocubes mainly bounded by {100} plane were prepared under the different Pb(AC)2/TAA molar ratio, at initial reaction temperature 40℃, refluxing for12 h at 100 ℃. Based on the systematic studies on their shape evolution, a possible...