Template Synthesis Of The1D Functional Nanomaterials

1D nanomaterials have received increasing interest because of their unique optical, thermal, electrical, magnetic and photoelectric properties for potential applications in many areas. Some1D nanomaterials with a large aspect ratio can be used as excellent energy conversion materials, and some of them can be assembled into to functional devices based on the of transport electrons, photons and phonons. Then many1D nanomaterials also can be used as template to synthesize other1D nanomaterials. Chalcogens and chacogenides are kinds of very important materials, and most of these materials have excellent properties in thermoelectric and photoelectric fields. Our group has reported a sucsessful synthesis of ultrathin uniform tellurium nanowires before. We also used the Te nanowires as templates to prepare other1D nanomaterials via a hydrothermal or solvothermal procedure, such as tellurides, CNFs, etc. However, due to the low yield of Te nanowires, it is hard to use these materials to fabricate practical functional devices, although these1D tellurides nanomaterials have outstanding properties in fields of photoelectric, thermoelectric, optical, etc. In this dissertation, we will focus on how to pruduce ultrathin Te nanowires in a large scale and then we will demonstrate the syntheses of other functional tellurides and hybrid nanomaterials by using the Te nanowires as templates. The results are shown below:1. We first demonstrate a sub-kilogram-scale synthesis of ultrathin tellurium nanowires. Through a one-pot scale-up hydrothermal method, we could obtain as many as150g ultrathin Te nanowires with a diameter of7-9nm, which looked like almost the same as the original ones. Based on the previous work, firstly, we modified the concentration of NaiTeO3the experimental results validated that the concentration could be expanded to10times larger with no negative effects on the quality of the products. Secondly, we tuned the concentraion of the PVP which acted as the soft template to find out the suitable concentration of PVP to form uniform Te nanowires. Finally, the volume of the reaction vessel had been gradually enlarged in order to get more products in one-pot reaction. We found that the reaction time should be prolonged as the volume of the vessel becoming larger. In addition, in order to confirm the highly chemical activity of the up-scale synthesized TeNWs and their ability for large-scale templating syntheses, Ag2Te and Cu2Te nanowires and carbonaceous nanofiber (CNFs) have been successfully prepared. According to the experimental results, it can be concluded that the up-scale synthesized TeNWs have the same chemical activity as the previous reported TeNWs.2. Highly uniform Bi2Te3nanowires with a length of tens of micrometres and a diameter of15-17nm can be synthesized through a simple and fast solution process by using ultrathin Te nanowires as sacrificial templates and its thermoelectric properties were researched. As a hot thermoelectric material which shows a high ZT around room temperature, Bi2Te3is very valuable for researches. Here, we used heating mantle as heat source to promote the solution reaction. Compared with hydrothermal process, this method is much more facil and efficiency and the products have better single crystal crystallinity. One important factor in this process is that the TEG was used as the solvent, which has a higher boiling point and better stability. In addition, according to the time dependent experiments, it can be concluded that Kirkendall effect and Ostwald process are all involved in this template-directed synthesis process. Compared with other Bi2Te3nanostructures and bulk Bi2Te3materials, the thermal conductivity of Bi2Te3nanowire pellet decreased evidently but its resistivity increased greatly. There are two reasons for this result. On is that residue of surfactant molecules in this process would adsorb on the surface the nanowires. The other reason is the limitation of the precessing method which would damage the structure of the nanowires.3. We sucessfully synthesized uniform TexSey alloy nanowires and TexSey@Se core-shell nanowires with high quality by using the Te nanowires as templates. In the presence of the Te nanowires, Se atoms would naturally attach to the surface of the Te nanowire and then nucleated and grew. Because the crystal structure of Se is similar to Te, the Se atoms could come into the orginal nanostructures and replace part of Te atoms, and form corresponding superfine TexSey alloy nanowire. At the same time, the TexSey@Se nanowires with different diameters could be synthesized successfully by the same method through changing the concentration of the Na2SeSO3. Similarly, these samples could be synthesized in a large scale on the basis of the up-scale synthesis of the as-template Te nanowires. Compared with Te nanowire, TexSey@Se nanowires have better photoconductivity but larger resistant, which even could be modified by controlling the ratio of the Se in the TexSey@Se nanowires. The TexSey alloy nanowires and TexSey@Se core-shell nanowires can also be used as excellent templates to synthsize a series of hybrid1D nanomaterials.