▎ 摘　　要

RationaleThe yield of endohedral metallofullerene (EMF) ions is greatly related to the encaged metal atoms. For alkali metals, the generation of corresponding large-sized monometallofullerene ions by traditional methods is still difficult. The aim of this work is to study the generation and the distribution of alkali-metallofullerene ions by the method of laser ablation with graphene as the precursor. MethodsThe experiment was performed with a Fourier transform ion cyclotron (FTICR) mass spectrometer. Mass spectra were obtained by laser ablation of the mixtures of graphene and KCl, RbCl or CsCl in the positive ion mode. Collision-induced dissociation (CID) experiments were also performed for some selected ions. ResultsEMF ions of M@C2n+(M=K, Rb, Cs, 2n=80-220) can be generated by using graphene as the precursor. Other EMF ions with smaller sizes, including M@C60+, were also observed under the optimized experimental conditions. CID experiments of some selected ions confirmed their endohedral structures. ConclusionsMetallofullerene ions of MC2n+(M=K, Rb, Cs, 2n=80-220) were generated by laser ablation of graphene and corresponding metal salts. Compared with previous results of alkaline earth metals, the yields of EMF ions are generally lower. However, for large-sized EMF ions, the relative intensities of EMF ions to their corresponding fullerene ions generally increase with the increase in cluster sizes, which is opposite to the trend observed for alkaline earth metals. Copyright (c) 2015 John Wiley & Sons, Ltd.