The Infinite Possible Growth Ambients that Support Single-Wall Carbon Nanotube Forest Growth

Abstract

We report the virtually infinite possible carbon feedstocks which support the highly efficient growth of single-wall carbon nanotubes (SWCNTs) using on the water-assisted chemical vapor deposition method. Our results demonstrate that diverse varieties of carbon feedstocks, in the form of hydrocarbons, spanning saturated rings (e.g. trans-deca-hydronaphthalene), saturated chains (e.g. propane), unsaturated rings (e.g. dicyclopentadiene), and unsaturated chains (e.g. ethylene) could be used as a carbon feedstocks with SWCNT forests with heights exceeding 100 ums. Further, we found that all the resultant SWCNTs possessed similar average diameter indicating that the diameter was mainly determined by the catalyst rather than the carbon feedstock within this synthetic system. A demonstration of the generality was the synthesis of a carbon nanotube forest from a highly unorthodox combination of gases where trans-decahydronaphthalene acted as the carbon feedstock and benzaldehyde acted as the growth enhancer.T he development of scientific research and industrial applications for carbon nanotubes (CNTs) has been primarily limited by its synthesis, and as a result, immense research, encompassing the control of the structure and underlying growth mechanism, has been invested over the past two decades to improve growth control, e.g. efficiency 1-8 , crystallinity 9-13 , and chirality 14,15 . Apt examples include the water-assisted chemical vapor deposition (CVD) method to improve growth efficiency 2 , floating catalyst CVD method to improve crystallinity 11 , and catalyst gas pretreatments for metallic selective growth 14,15 .Post-synthetic techniques have also been developed to improve the purity or selectivity of the CNTs. For example, density gradient ultracentrifugation combined with the appropriate surfactant enables effective individualization of single-wall carbon nanotube (SWCNT) for the separation of metallic versus semiconducting SWCNTs as well as the enrichment of a single-chirality, (6,5) 16 . In addition, numerous post-synthetic processes have been developed for the purification of CNTs ranging from chemical oxidation, such as gas phase, liquid phase, and electrochemical oxidation, to physical-based purification, such as filtration, centrifugation, functionalization, and high temperatures annealing and combinations [17][18][19] .In the synthesis of CNTs by the CVD process, numerous carbon feedstocks have been applied, often in the form of hydrocarbons, such as methane 20,21 , acetylene 20,29,30 , and ethylene 2,20 and even anthracene 21 . Further, each synthetic method, i.e. thermal CVD, plasma-enhanced CVD, floating catalyst CVD, laser ablation, seemed to show preferences on the carbon feedstock [22][23][24] . For example, in plasma-enhanced CVD, methane or other low molecular-weight carbon feedstocks are preferred 22 , while for floating catalyst CVD, which is carried out at higher temperatures, cyclic aromatic hydrocarbons, e.g. toluene, xylene, and benzene are most commonly used due to their high decomposi...

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