||Designing artificial nanomaterials capable of selectively detecting target molecules without using antibodies is of great interest in biosensing and nanomedicine. Here, we have demonstrated the chemical modulation of graphene oxide (GO) with a variety of amino acids and metal ions (GO-AA-MI) to control its fluorescence response to neurotransmitters. GO was functionalized with six amino acids on which eight metal ions were chelated. The functionalized GO (GO-AA-MI) exhibited unique and selective fluorescence responses to several neurotransmitters, including dopamine. Particularly, the GO-D-Fe hybrid was able to selectively detect dopamine at nanomolar concentrations through its fluorescence quenching. Moreover, it was successfully applied to detection of dopamine secreted from living PC12 cells.