Study of precise on structural control of carbon nanotubes

对于单壁碳纳米管（SWCNTs）在晶体基板上的CVD生长，以铁蛋白为生长催化剂，探讨了其在蓝宝石基板上的自定向生长机理。我们在特殊设计的衬底上的生长行为分析表明，定向生长是由尖端生长机制引起的。这一结论得到了蓝宝石衬底上swcnts生长的原位SEM观察的证实。利用拉曼光谱原位观察CVD生长过程，研究了SWCNTs的手性分辨生长动力学。首次清晰检测到生长SWCNTs的径向呼吸模式的拉曼信号。我们对生长动力学的详细分析阐明了swcnts手性、催化剂直径和生长时间之间的相关性。SWCNTs在特高压相容气源MBE系统中以酒精作为碳原料，在非常清洁的条件下生长。利用原位x射线光电子能谱对生长的SWCNTs的化学状态进行了表征。从光谱分析中，我们发现Co催化剂颗粒即使在CVD生长后仍保持“金属态”，这与普通的VLS生长机制相反，而Fe催化剂在较高温度下CVD生长后部分形成氧化物，这解释了为什么Fe催化剂的SWCNTs产率比Co催化剂低。由铁蛋白衍生的颗粒（煅烧后直径为3-5 nm）通过蒸发制备了非常细的金属纳米颗粒（直径小于2 nm）。SWCNTs直径与催化剂颗粒之间的相关性提示了SWCNTs直径控制的可能性。SWCNTs是由新型催化剂材料合成的，这些材料被认为没有催化活性，如硅、锗、SiC的半导体纳米颗粒和金、银、铜的贵金属纳米颗粒。基于这些现象，我们提出了一种新的生长机制，为手性控制开辟了可能。少

For the CVD growth of single-walled carbon nanotubes(SWCNTs) on crystalline substrates, the mechanism of self-directional growth on sapphire substrates was explored by using ferritins as growth catalysts. Our analysis of growth behavior on the specially designed substrates indicates that the directional growth is caused by the tip-growth mechanism. This conclusion was confirmed by in-situ SEM observation of the SWCNT growth on sapphire substrates. Chirality-resolved growth kinetics of SWCNTs was investigated by in situ observation of the CVD growth process using Raman spectroscopy. The Raman signals of radial breathing modes from growing SWCNTs were clearly detected for the first time. Our detailed analysis of the growth kinetics clarified the correlation among SWCNT chirality, catalyst diameter and growth duration.SWCNTs were grown under very clean conditions in a UHV-compatible gas-source MBE system using alcohol as carbon feedstock. The chemical states of grown SWCNTs were character … More ized by in-situ X-ray photoelectron spectroscopy. From the analysis of the spectra, we found that Co catalyst particles maintain "metallic states" even after CVD growth, contrary to the ordinary VLS growth mechanism, and that Fe catalysts partially form oxides after CVD growth at higher temperature, which explains the very low yield of SWCNTs for Fe catalyst compared with Co catalyst.Very fine metal nanoparticles(diameter of less than 2 nm) were prepared by evaporation of particles(diameter of 3-5 nm, just after calcination) derived from ferritin. The possibility of SWCNT diameter control is suggested by the correlation between diameters of SWCNTs and the catalyst particles. SWCNTs were synthesized from novel catalyst materials, which have been considered to have no catalytic activity, such as semiconductor nanoparticles of Si, Ge, SiC, and noble metal nanoparticles of gold, silver, copper. On basis of these phenomena, we proposed a new growth mechanism that will open up the possibility of chirality control. Less