Variable Angle Spectroscopic Ellipsometry Characterization of Graphene Oxide in Methanol Films

It has been widely established that solvents modify the functional groups on the graphene oxide (GO) basal plane and, thus, modify its reactivity. Despite the increasing interest in GO films, a less studied aspect is the influence of methanol on the refractive index of GO films. Herein, the Variable Angle Spectroscopic Ellipsometry (VASE) technique has been used to characterize the optical response of GO in methanol films (0.4 mg/mL) dip-coated on glass substrates. The ellipsometric data have been modeled using a Lorentz oscillator model. We have found that the energy of the oscillator at similar to 3.9 eV for GO in water shifts to similar to 4.2 eV for GO in methanol films.