Femtosecond pump-probe spectroscopy of graphene oxide in water

Transient absorption properties of aqueous graphene oxide (GO) have been studied by use of femtosecond pump-probe spectroscopy. Excited state absorption and photobleaching are observed in the wide spectral range. The observed fast three lifetime components are attributed to the absorption of upper excited states and localized states, which is confirmed by both laser induced absorption and transmission kinetics. The longest time component is assigned to the lowest excited state of GO, which mainly originates from the sp2 domains. With the increase of the excitation power, two-quantum absorption occurs, which results in an additional rise-time component of the observed transients.