According to Claramunt and coworkers, the chemical and thermal reductions are creating defects which alter "the physical and chemical properties of graphene-based materials. Then, taking into account the important role of defects in the properties of these materials, it becomes necessary to develop an accurate methodology to study them. Raman spectroscopy … has been widely used to study graphite and graphene" . The researchers describe the spectra in the following manner. The Raman peaks in crystalline graphene are G (∼1585 cm -1 ) and 2D bands (∼2700 cm -1 ), that is first-and second-order Raman modes. The peaks change their width in the spectrum of GO. "These changes were attributed to high defect concentration related to the oxidation and are accompanied by the appearance of an intense peak centered at∼1350 cm -1 , called the D band. The D band is related to the A1g breathing mode, and it is observed because graphite oxidation and the subsequent reduction of GO seriously alter the basal plane structure of graphene" .