||Designing nanomaterials capable of selectively detecting target molecules without using antibodies is of great interest in biosensing and nanomedicine. Here, we demonstrate the chemical modulation of graphene oxide (GO) fluorescence with a combination of amino acids and metal ions, leading to GO-organometallic complex (GO-AA-MI) nanostructure to impart them the fluorescence response selectivity to catecholamine to neurotransmitters. To this end, GO was functionalized with six amino acids, followed by chelation of eight different metal ions. The functionalized GO-AA-MI exhibited unique and selective fluorescence responses to several neurotransmitters, including dopamine. Particularly, the GO-Y-Fe hybrid was able to selectively detect dopamine at nanomolar concentrations through its fluorescence quenching. Finally, the GO-Y-Fe hybrid sensor successfully applied to detection of dopamine secreted from living PC12 cells.