Identifying the fluorescence of graphene oxide

Treatment of graphene oxide (GO) with sodium hydroxide separates the material into two components: a colourless, but highly fluorescent, oxidative debris and a darker non-fluorescent material containing the graphene-like sheets. The as-produced GO shows a weak, broad photo-luminescence while the oxidative debris fluoresces more intensely, blue-shifted relative to the as-produced GO, with a dispersive emission profile shifting to lower wavelength as the excitation wavelength is decreased. Such excitation wavelength dependent photoluminescence is characteristic of ensembles of nanometre-sized carbon based fluorophores. By contrast, analysis of the fluorescence as a function of excitation wavelength for as-produced graphene oxide shows a single non-dispersive peak, consistent with broadening of the emission from a single species rather than an ensemble of quantum dots within the graphene sheet.