Probing structural variations of graphene oxide and reduced graphene oxide using methylene blue adsorption method

Abstract

Recently, graphene oxide (GO) and reduced graphene oxide (rGO) have drawn significant attention in the development of gas sensors and nanocomposites. However, random distribution of oxygen functionalities in GO and rGO limits the use of these materials in the above application. In this study, methylene blue (MB) adsorption onto GO, synthesized under different oxidative conditions, and onto corresponding rGO was looked into in detail as both have high affinity towards MB. Our results show the amounts of MB adsorbed onto all GOs are the same irrespective of the time of oxidation. However, significant changes were observed in the amount of MB adsorbed on the corresponding rGOs that have been thermally reduced. Further, the FT-IR spectroscopic data show a blue shift for C=C stretching vibrations of MB adsorbed onto GO, whereas a red shift is observed for the bands assigned to stretching vibrations of C–N and CH3 bending upon adsorption on rGO. The above observations suggest complex structural geometry of GO and rGO, especially with respect to the spatial distribution of oxygen functionalities and their propagation during synthesis that influence MB adsorption, and its orientation. Thus, the information provided will be important in controllable synthesis of both GO and rGO with large surface area for the above applications as well as in applications such as water purification and photocatalysis.