Fig. 2

Correlation of the scattering and optical conductivity of graphene. a Potential dependence of relative scattering change of a gold nanostar (red), neighboring graphene (blue), and the optical conductivity of the graphene (black). Insets show the band structures of graphene at corresponding potentials. b Correlation of the relative scattering change and the optical conductivity (red and blue), and the theoretical correlation of graphene’s carrier density and relative scattering change (black line). c Introduction of excess charges doping in the graphene layer with hydroxyl and hydroxonium ions. Insets show the corresponding energy diagrams. d Potential dependence of relative scattering change of gold nanostars with different surface condition: from negative (top) to positive (bottom) charge