Generation of endohedral metallofullerene ions of Ca1-4C2n+ (44 ≤ 2n ≤ 132) by laser ablation of natural graphite sheets without pretreatment

Abstract

The selection of precursor is essential for the generation of various endohedral metallofullerenes (EMFs) in the laser ablation mass spectrometry experiments. Herein, natural graphite sheets without any pretreatment were applied in the laser ablation experiments with a Fourier transform ion cyclotron resonance (FT ICR) mass spectrometer. EMF ions of ${{\text{Ca}}_{1-4}@C}_{2n}^{+}\left(44\le 2n\le 132\right)$ were identified in the mass spectrum. Although the distributions of the mono- and di- EMF ions are somewhat similar to those previously observed with the precursor of graphene/CaCl₂, the tri-EMF ions of ${\text{Ca}}_3@C_{2n}^{+}$ (2n = 92–132) and tetra-EMF ions of ${\text{Ca}}_4@C_{2n}^{+}$ (2n = 110–124) were also observed, which have not been reported before. The presence of these Ca-related impurities not only indicates that laser ablation mass spectrometry can be an effective means of identifying natural graphite but also suggests that well-designed doping can provide a long-lasting and enduring pathway for the generation of new EMFs.