Generation of M@C(2n)+ (M = K, Rb, Cs, 2n = 80-220) by laser ablation of graphene.
BACKGROUND
The 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.


METHODS
The 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.


RESULTS
EMF ions of M@C(2n)+ (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.


CONCLUSIONS
Metallofullerene ions of M@C(2n)+ (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 I(M@C(2n)+)/ I(C(2n)+) generally increase with the increase in cluster sizes, which is opposite to the trend observed for alkaline earth metals.
State Key Laboratory and Institute of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering, Nankai University, Tianjin, 300071, China.
Xiaodi
X
Bao
State Key Laboratory and Institute of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering, Nankai University, Tianjin, 300071, China.
Xianglei
X
Kong