Production of monolayer, trilayer, and multi-layer graphene sheets by a re-expansion and exfoliation method

Mass graphene sheets were obtained by a re-expansion and exfoliation method which uses the commercially available graphite intercalation compounds as the starting materials. The as-prepared samples have been characterized by scanning electronic microscopy, transmission electron microscope, atomic force microscope, Fourier transform infrared spectrometer spectroscopies, and Raman microscope. Using high resolution transmission electron microscopy on 60 samples, it was shown that the final samples exhibit 8 % monolayer, 19 % bilayer, and 77 % less than or equal to five layers, and the sheets are largely free of defects and chemical functional groups after thermal reduction.