Hydrogen storage of capped single-walled carbon nanotube via transition-metal doping Z. Y. Tian, Y. T. Liu, W. W. Wu, L. N. Jiang and S. L. Dong EPL, 104 3 (2013) 36002 Published online: 29 November 2013 DOI: 10.1209/0295-5075/104/36002