UV-visible absorption spectra for various GO dispersions were collected with a Jasco V-670 spectrophotometer using a 10 mm quartz cell. The microstructure of the GO samples on a gold
substrate was investigated by a eld emission scanning electron microscopy (FE-SEM, JEOL JSM-6700F). Atomic force microscopy (AFM) images of GO-1 and GO-3 were obtained using an AFM-Nano Wizard in tapping mode with a Si tip on the Si/SiO2 substrate. X-ray photoelectron spectroscopy (XPS) analysis was performed on a theta probe ESCA VG Scientic (2002) using monochromatic AlKa as the exciting source. The peak positions of the XPS were adjusted carefully with respect to the Au 4f peak because of the insulating character of GO. Finally, the XPS spectra were deconvoluted by using the Voigt tting function aer a Shirley background subtraction procedure. Gas chromatography (GC) analyses were performed on a GC-FID-CHINA CHROMATOGRAPHY 9800 system (glass column Porapak Q (80–100 mesh), inj. temp. 110 C, FID temp. 150 C and oven temp. 130 C). GC-MS analyses were performed on a GC (HP 6890)/MS (HP 5973) system (column-Agilent DB-624, inj. temp. 250 C and oven temp. 40 C).