Spectral Migration of Fluorescence in Graphene Oxide Aqueous Dispersions: Evidence for Excited-State Proton Transfer.
Aqueous dispersions of graphene oxide (GO) exhibit strong pH-dependent fluorescence in the visible that originates, in part, from the oxygenated functionalities present. Here we examine the spectral migration on nanosecond time-scales of the pH dependent features in the fluorescence spectra. We show, from time-resolved emission spectra (TRES) constructed from the wavelength dependent fluorescence decay curves, that the migration is associated with excited state proton transfer. Both 'intramolecular' and 'intermolecular' transfer involving the quasi-molecular oxygenated aromatic fragments are observed. As a prerequisite to the time-resolved measurements, we have correlated the changes in the steady state fluorescence spectra with the sequence of dissociation events that occur in GO dispersions at different values of pH.
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India.
Bharathi
B
Konkena
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India.
Sukumaran
S
Vasudevan
excited state proton transfer; fluorescence decay; graphene oxide; steady-state fluorescence; time-resolved emission spectroscopy (TRES)