In a first time, we show experimentally that grafting SLG with halogenophenyl moieties induces optical transparencies at two specific energies: 1250 and 1600 cm-1 , in close similarity to the bands that can also be observed in carbon nanotubes as Fano resonances.  Unlike bands caused by the absorption of light by vibrational modes, these antiresonances show a decrease of the absorbance, an optical transparency effect. Moreover, we show that the amplitude of the transparencies can be modulated by changing the charge carrier density through doping, and by the defect density through controlled grafting.
In as second time, we will present a theory based on quantum mechanics to calculate the optical conductivity of grafted SLG.  The model puts into play phonon modes with momenta different from Γ that can be addressed through scattering on defects. Numerical simulations reproduce the experimental data with good agreement. The theory also captures the dependence of the signal on charge carrier density and defect density.
Our findings bring a new understanding for the physics behind the infrared activity of nanostructures, while opening new capabilities for tailoring the optical spectrum of nanomaterials.
 Horng et al. (2011) Phys Rev B 83:165113
 Low & Avouris (2014) ACS Nano 8:1086
 Kuzmenko et al. (2009) Phys Rev Lett 103:116804
 Rousseau et al. (2014) arXiv preprint arxiv:1407.8141
 Lapointe et al. (2012) Phys Rev Lett 109:097402