Gaussian16W software and the pm6D3 semi-empirical method were used to analysis the structure and the vibration of GO. 
Gaussian16W
Gaussian16W software and the pm6D3 semi-empirical method were used to analysis the structure and the vibration of GO. 
pm6D3 semi-empirical method
The B3LYP function and basis set DEF2SVP was used to calculate the single point energy. 
B3LYP function