title: Carbon atoms in ethanol do not contribute equally to formation of single-walled carbon nanotubes.
abstract: We propose a unique experimental technique in which isotopically labeled ethanol, e.g., 12CH3-13CH2-OH, is used to trace the carbon atoms during the formation of single-walled carbon nanotubes (SWNTs) by chemical vapor deposition (CVD). The proportion of 13C is determined from Raman spectra of the obtained SWNTs, yielding the respective contribution of ethanol's two different carbon atoms to SWNT formation. Surprisingly, the carbon away from the hydroxyl group is preferably incorporated into the SWNT structure, and this preference is significantly affected by growth temperature, presence of secondary catalyst metal species such as Mo, and even by the substrate material. These experiments provide solid evidence confirming that the active carbon source is not limited to products of gas-phase decomposition such as ethylene and acetylene, but ethanol itself is arriving at and reacting with the metal catalyst particles. Furthermore, even the substrate or other catalytically inactive species directly influences the formation of SWNTs, possibly by changing the local environment around the catalyst or even the reaction pathway of SWNT formation. These unexpected effects, which are inaccessible by conventional techniques, paint a clearer picture regarding the decomposition and bond breaking process of the ethanol precursor during the entire CVD process and how this might influence the quality of the obtained SWNTs.
authors: State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275, China. xiangr2@mail.sysu.edu.cn
authors: Rong
authors: R
authors: Xiang
authors: Bo
authors: B
authors: Hou
authors: Erik
authors: E
authors: Einarsson
authors: Pei
authors: P
authors: Zhao
authors: Sivasankaran
authors: S
authors: Harish
authors: Kenichi
authors: K
authors: Morimoto
authors: Yuhei
authors: Y
authors: Miyauchi
authors: Shohei
authors: S
authors: Chiashi
authors: Zikang
authors: Z
authors: Tang
authors: Shigeo
authors: S
authors: Maruyama
mesh_terms: D003460:Crystallization / Q000379:methods*; D000431:Ethanol / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D013499:Surface Properties
chemical_list: D046911:Macromolecular Substances; D037742:Nanotubes, Carbon; D000431:Ethanol