Thickness-dependent azobenzene doping in mono- and few-layer graphene

Doping effects on exfoliated graphenes induced by methyl orange (MO) have been studied by spatially resolved Raman spectroscopy. When the MO molecules were adsorbed on the top of graphenes, the charge transfer between them caused two outcomes simultaneously. One is the strong chemical doping in graphenes and the other is the enhanced Raman signals of MO molecules. Our finding provides a potential approach for manipulating the electronic properties of graphenes and investigating the vibrational properties of molecules. Moreover, the thickness-dependent doping effects in graphenes are unambiguous distinguished by Raman imaging. The possible origin was discussed and designated to the different band structures of graphenes and the screening effect.