Synthesis Of The Low-dimensional Nanostructured Materials

The studies of nanomaterials started in the early 1980's and have now become one of the hottest worldwide research fields. Nanostructured materials have many special mechanical, optical, electrical, magnetic, thermotic and chemical properties which differ from the corresponding bulk material due to their size effect, surface effect and quantum effect, thereby making them attractive for many new applications in many industry as well as high-tech fields. Preparation of the nanomaterials plays a key role in nanoscience research. Various methods have been used for the preparation of nanostructured materials. However, different intriguing questions remain unanswered even now, it is still a challenging research area to prepare novel functional nanostructured materials with interesting and useful properties, it is even important to explore novel methods for synthesis of nanomaterials with controllable size and shape and to understand the mechanism and rule of the growth process of nanomaterials for further application.In this paper, focusing on the preparation of nanostructured materials, some basic questions of nanomaterials have been researched and the results can be summarized as follows:(1) A novel laser-solid-liquid ablation technique has been developed to synthesize Ag2Se nanoparticles from silver nitrate and selenium powder in a mixed solvent of 2-propanol and ethylenediamine. The XRD analysis indicated that the products were the single phase of silver selenide. The TEM images revealed that that as-prepared Ag2Se grains were homogeneous and spherical, and their average size was about 30 nm. A mechanism was proposed base on the experiment results. The synthesis Ag2Se shows that the technique is efficient in preparing the nanoparticles. The technique can certainly be applied to synthesize the nanoparticles of other binary components, which are difficult to be obtained by other conventional methods.(2) Nano-structured selenium products with different shapes have been synthesized from selenium powders in a heated quartz tube by laser ablation. By well controlling the substrate temperature and reaction time, pure selenium nanorods with uniform lateral dimensions can be selectively and bulky produced ranging from 20 nm to several hundred nanometers, and the length of selenium nanorods can be up to tens of micron. The selenium nanorods synthesized by the proposed method are free from any catalyst or template, which is benefit to the further use.(3) Uniform a-TeO2 nanorods is successfully synthesized from tellurium for the first time via a laser assisted growth route in the hot air. By carefully controlling the experiment conditions, large amount of a-TeOa nanorods with a relatively straight morphology and a uniform diameter of 20-100 nm can be routinely achieved. HRTEM and ED results show that the nanorods synthesized are single-crystalline. A mechanism of the vapor-liquid-solid (VLS) following the chemical oxidation in the air was proposed for the growth of a-TeC>2 nanorods, in which the low melting point tellurium served as a liquid-forming agent. This method requires no metal catalysts and/or templates as usually needed in other methods. The air is used as reactant and no inert gas is needed. It could be of great interest to extend this method to the synthesis of one-dimensional nanostructures of other oxides.(4) Comb-like ZnO nanorod array has been successfully obtained via a laser assisted chemical deposition in 800癈. The comb trunks are 500-lOOOnm in width and several micrometers in length, and the nanorods are 50-100nm in width and 500-2000nm in length. Both the comb trunks and the nanorods were characterized as hexagonal wurtzite structured ZnO. The special shaped ZnO nanostructured materials may have potential use in fabricating new types of nanoelectronic, optoelectronic devices. By varying the experiment conditions, other ZnO nanostructured materials, such as nanoparticals and nanowires can also be obtained.(5) Uniform silver nanowires of diameter 20-50nm...