The pH Dependence of Ultrafast Charge Dynamics in Graphene Oxide Dispersions

TL;DR

This study investigates how pH influences ultrafast charge dynamics in graphene oxide dispersions using transient absorption spectroscopy, revealing protonation effects on excited state processes within sub-picosecond timescales.

Contribution

It provides new insights into the pH-dependent charge transfer mechanisms in graphene oxide at ultrafast timescales.

Findings

Protonation occurs within ~1.5 ps at pH < 9.3.

Excited state protonation affects recombination dynamics.

A broad absorption peak at 530 nm indicates protonation-related excited states.

Abstract

The pH dependence of emission from graphene oxide is believed to be due to the protonation of surface functional groups. In this study we use transient absorption spectroscopy to study the sub-picosecond charge dynamics in graphene oxide over a range of pH values, observing dynamics consistent with an excited state protonation step for pH < 9.3. The timescale of this process is ~ 1.5 ps, and a corresponding change in recombination dynamics follows. A broad photo-induced absorption peak centred at 530 nm associated with excited state protonation is also observed.