Modulating oxygen vacancy concentration for selective growth of semiconducting single-walled carbon nanotubes with narrow diameters

Semiconducting single-walled carbon nanotubes(s-SWCNTs)with narrow diameters are promising for future applications in many fields,especially in nanoelectronics and optoelectronics.In this study,the oxygen vacancy concentration modulating strategy was utilized for growing narrow diameters s-SWCNTs by the chemical vapor deposition(CVD)method.The Fe_(0.01)Mg_(0.99)O solid solution based catalyst was syn-thesized to anchor the Fe particles and inhibit aggregation for growing SWCNTs with uniform diameters.CeO_(2)was introduced into the catalyst to provide oxygen vacancies through H_(2)prereduction.These oxygen vacancies could form an oxidative environment during the growth of SWCNTs,and the chemically active metallic carbon nanotube caps are selectively etched away under this environment.The Fe/Ce molar ratio and H2 prereduction time were optimized to modulate the oxygen vacancy concentration.Ultimately,us-ing the Fe_(0.01)Mg_(0.99)O/CeO_(2)(3)catalyst with 10 min of H_(2)prereduction time,high purity s-SWCNTs with diameters ranging from 1.41 to 1.71 nm and a content of 95.1%were obtained with high selectivity and carbon yield(1.33 wt%).The mechanism behind this phenomenon was elucidated through experimental characterizations and first-principle simulations,further expanding the understanding of the growth of s-SWCNTs through the modulation of oxygen vacancy concentration.