260039 Selective Synthesis of (9,8) Single Walled Carbon Nanotubes Using CoSO4/SiO2 Catalyst

Tuesday, October 30, 2012: 10:10 AM
311 (Convention Center )
Yuan Chen, Hong Wang and Li Wei, School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore, Singapore

A new chirality selective catalyst (CoSO4/SiO2) has been developed for single walled carbon nanotube (SWCNT) synthesis. The CoSO4/SiO2 catalyst is prepared by dispersing cobalt (II) sulphate heptahydrate on high surface area porous silica using an incipient wetness impregnation method. Photoluminescence, absorption and Raman spectroscopy results show the CoSO4/SiO2 catalyst has high selectivity toward (9,8) nanotubes. The chirality selectivity of the catalysis can be tuned by varying catalyst reduction conditions. At an optimal reduction condition, when the catalyst is reduced under H2 up to 540 oC, photoluminescence results show the (9,8) nanotubes count for 51.7 % of all semiconducting SWCNTs. Theoretical study shows that the diameter of structurally stable metal nanoparticles is scattered, other than continual. The Co147 cluster is the most stable cluster in its diameter range. The selectivity toward the (9,8) nanotube is credited to large Co nanoparticles with diameter comparable with that of (9,8) nanotubes. Forming such large Co nanoparticles is because of the lower reduction temperature (470 oC) of Co species in the CoSO4/SiO2 catalyst. We also found that sulfur compounds resulting from reducing SO42- ions play a critical role in stabilize such large Co nanoparticles. This research opens up routes toward highly selective growth of SWCNTs.

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