▎ 摘　　要

Metallofullerene ions of M@C-2n(+) (M = Ca, Sr, Ba, 2n = 50-230) were generated by laser ablation of graphene and corresponding metal salts using a commercial MALDI source without any modification. Large monometallofullerene ions up to Ba@C-272(+), and di-metallofullerene ions were observed in the mass spectra. The endohedral structures are confirmed by on resonance collisionally activated dissociation experiments on the selected ions. Although the distributions of the endohedral metallofullerene (EMF) ions for three alkaline earth metals are similar, the productivities decrease with the size of the metal atoms. Comparing with previously applied sources for EMF ions, this method is characterized by the direct usage of a commercial MALDI source, rapid and simple sample preparation, and the generation of large-sized EMF ions. (C) 2014 Elsevier B.V. All rights reserved.