Ago Hiroki, Imamura Shingo, Okazaki Toshiya, Saito Takeshi, Yumura Motoo, Tsuji Masaharu
Institute for Materials Chemistry and Engineering, Kyushu University, Kasuga 816-8580, Kyushu, Japan.
J Phys Chem B. 2005 May 26;109(20):10035-41. doi: 10.1021/jp050307q.
Single-walled carbon nanotubes (SWNTs) with a narrow diameter distribution are synthesized by thermal chemical vapor deposition (CVD) of methane over Fe/MgO catalyst on the basis of parametric study considering Fe loading, reaction temperature and time, methane concentration, and structure of a support material. We found that the porous MgO support gives the SWNTs with a narrow diameter distribution with the mean diameter and standard deviation of 0.93 and 0.06 nm, respectively, only when the Fe loading and reaction temperature are relatively low. The higher Fe loading and/or the higher reaction temperature enlarged the nanotube diameter, forming double-walled carbon nanotubes (DWNTs) in addition to SWNTs. This result indicates that only the diameter of Fe nanoparticles determines the growth of either SWNTs or DWNTs on the MgO support. The fluorescence and absorption spectra of the nanotube dispersion in D(2)O solution with sodium dodecyl sulfate (SDS) were studied to identify their chirality distribution. The fluorescence of the uniform-diameter SWNTs indicates the formation of the near armchair structures. On the other hand, the SWNTs synthesized over the catalyst with a high Fe loading, 3 wt %, showed a wide chirality distribution including the near zigzag structure. The synthesis of the SWNTs with a narrow diameter distribution could be applied to the selection of SWNTs with a specific chirality based on postsynthesis separation.
基于对铁负载量、反应温度和时间、甲烷浓度以及载体材料结构的参数研究，通过甲烷在Fe/MgO催化剂上的热化学气相沉积（CVD）合成了具有窄直径分布的单壁碳纳米管（SWNTs）。我们发现，只有当铁负载量和反应温度相对较低时，多孔MgO载体才能提供平均直径和标准偏差分别为0.93和0.06 nm的窄直径分布的SWNTs。较高的铁负载量和/或较高的反应温度会使纳米管直径增大，除了SWNTs之外还会形成双壁碳纳米管（DWNTs）。这一结果表明，只有铁纳米颗粒的直径决定了MgO载体上SWNTs或DWNTs的生长。研究了在含有十二烷基硫酸钠（SDS）的D(2)O溶液中纳米管分散体的荧光和吸收光谱，以确定它们的手性分布。直径均匀的SWNTs的荧光表明形成了近扶手椅结构。另一方面，在铁负载量为3 wt%的催化剂上合成的SWNTs显示出包括近锯齿结构在内的广泛手性分布。具有窄直径分布的SWNTs的合成可应用于基于合成后分离的特定手性SWNTs的选择。
