The timedependent fluorescence quenching of GQDs@GSH in the presence of Fe3+ occurred due to chelation. The fluorescence restoration of GQDs@GSH–Fe3+ in the presence of ATP was also observed. The formation and the release of the ATP–Fe3+ complex from GQDs@GSH was relatively slow and needed almost 15 min to reach equilibrium. Using this interesting strategy, amethod was developed for sensitive quantification of ATP in the range 25–250 μM