Graphene oxide (GO) nanosheets can be functionalized with reactive pentafluorophenyl ester via esterification of the carboxylic groups. The resulting reactive GO nanosheets provide a versatile platform for grafting of amino-containing polymers or biomolecules via ester–amine coupling. Coupling of poly[(9,9-dioctylfluorene)-alt-(4-amino-phenylcarbazole)] (PFCz-NH2), amino-terminated hyperbranched polyglycerol (HPG-NH2), and lysozyme (Lyz) was illustrated. The Al/GO-g-PFCz/ITO sandwich thin-film device exhibits bistable electrical switching and rewritable memory effects. The GO-g-Lyz nanohybrids exhibit high bactericidal efficacy against S. aureus and E. coli, while the GO-g-HPG nanohybrids exhibit reduced cytotoxicity toward 3T3 fibroblasts.