The Studies of Surface Chemistry of Carbon Nanotubes and Synthesis of Fullerene Nanowires
- The Studies of Surface Chemistry of Carbon Nanotubes and Synthesis of Fullerene Nanowires
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- Current science is focusing to smaller nano-electronic devices. To correspond to these trends, zero-dimensional (0D), one-dimensional (1D) structures and other semiconductors with different shape have been synthesized and we expect these nanostructures to offer high performance in electronics via varied approaches. Moreover, 1D nanostructures such as wires, rods, belts and tubes have became intensive research owing to their unique applications in mesoscopic physics and fabrication of nanoscale devices.
Carbon is one of the outstanding elements in the universe and can form various structures through the hybridization between sp2 and sp3. The major types of 1D carbon nanostructures are mainly composed of carbon nanotubes and fullerene nanowires with their pi-conjugated system. Nevertheless 1D carbon nanostructures have been applied in a number of fields due to their characteristics, chemical approaches on them have been required to lead their potential capability for versatile and practical applications. Therefore, in this thesis, from the synthesis to electrical and structural characterization of carbon nanotubes and fullerene nanowires will be briefly introduced with unique device performance.
Carbon nanotubes are one of the most intensively explored nanostructures. The hybrid structures of carbon nanotube and nanoparticles can be applied in areas as diverse as catalyst, hydrogen storage, fuel cell and sensing. The introduction of transition metals (Ru, Cu, Zn, Sn) on single walled carbon nanotubes (SWNTs) was feasible owing to the functionalization of 2,2
6,2'-terpyridine (Terpy) on SWNTs via non-covalent interaction. Electron transfer phenomenon upon the functionalization of Terpy on SWNTs and the reaction of Ru(III) with Terpy-SWNT were also studied by measuring the conductance changes using SWNT-field effect transistor (SWNT-FET) devices as well as X-ray photoelectron spectroscopy (XPS) (section 2.2 in PART 2).
The other ideal approach to obtain uniform electrical and optical properties in the SWNTs is the separating method of metallic and semiconducting nanotubes from as-grown nanotubes and it is essential for nano-electronic devices applications. While conventional hydrosilylation reaction on alkene and alkyne is required of Lewis acid catalyst or photon or thermal energies, the hydrosilylation reaction on SWNTs occurs by triethylsilane (Et3SiH), resulting in silencing of metallic SWNTs from the mixtures. The successful covalent bond formation was monitored by using AFM-correlated NanoRaman spectroscopy showing dramatic changes in D/G ratio. The spontaneity of hydrosilylation reaction is originated from the highly strained circumference structure of SWNT. The hydrosilylation reaction was attempted to network-type SWNTs-FET devices to increase their on/off ratios of current. The hydrosilylation reaction will be a efficient and promising chemical route to selectively control specific electrical properties as well as chemical doping of SWNTs (section 3.2 in PART 3).
Since fullerenes(C60) are among the most important novel materials in the carbon family, 1D C60 has also attracted much attention together with carbon nanotubes. Generally, this kind of structure can be obtained by a solution growth method. In part 4, we report that ultrathin C60 nanowires, with a diameter of less 50 nm and face centered cubic (fcc) crystal structure after annealing, were grown from a oversaturated triethylsilane (TriES) solution. Also, the C60 in m-xylene was observed similar with a diameter of less 100 nm. These phenomena is caused by low solubility of C60 in TriES and m-xylene at oversaturated concentration. Because the solubility of C60 is lower in TriES than in m-xylene, the nanowire size obtained from TriES solution was smaller than for nanowires grown from m-xylene. This facile route for the synthesis and high yield of C60 nanowires are going to have an advantage for potential applications in nanometer scale devices (PART 4)
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