EXTENDED ANALYSIS OF THE UV–VIS ABSORPTION SPECTRUM OF GRAPHENE OXIDE. URBACH ENERGY, TAUC MODEL AMBIGUITY AND sp2 DOMAIN SIZE

Аннотация

The ultraviolet–visible absorption spectra of graphene oxide synthesized by the Hummers
method are analysed, yielding optical parameters not published previously. The Urbach energy is
determined for the first time and equals 0.91 ± 0.01 eV, the exponential region spans 2.00–3.45 eV and is
concentration-independent. A model comparison rules out a light-scattering artefact. The steepness
parameter σ = kT/EU equals 0.028. Three methods of locating the n→π* shoulder differ by up to 20 nm. The
sp² domain size is evaluated independently from optical and Raman data. The values obtained are proposed
as baseline parameters for GO/Fe₃O₄ magneto-optical systems.