Crown oxygen-doping graphene with embedded main-group metal atoms Liyuan Wu, Qian Wang, Chuanghua Yang, Ruge Quhe, Pengfei Guan and Pengfei Lu Eur. Phys. J. B, 91 2 (2018) 46 Published online: 19 February 2018 DOI: 10.1140/epjb/e2018-80396-2