A　simple　graphene　quantum　dots　(GQDs)-based　fluorescence　sensing　system　was　developed　for　rapid,　sensitive　and　low-cost　detection　of　ascorbic　acid　(AA)　in　the　presence　of　copper　ions.　Due　to　the　efficient　electron-transfer　between　GQDs　and　Cu2+　ions,　the　fluorescence　of　GQDs　was　greatly　quenched　by　Cu2+　ions.　Upon　addition　of　ascorbic　acid,　Cu2+　was　reduced　to　Cu+　and　the　interaction　of　Cu2+-GQDs　was　destroyed,　which　inhibit　the　quenching　and　thus　leading　to　fluorescence　recovery　of　GQDs.　The　detection　process　is　ultrafast　and　can　be　completed　within　5　min.　The　linear　response　range　of　AA　was　obtained　from　0.3　mu　M　to　10　mu　M.　The　detection　limit　was　as　low　as　94　nM,　which　was　comparable　to　or　even　better　than　other　reported　assays.　In　addition,　this　sensing　system　also　showed　good　selectivity　for　detecting　AA　in　the　presence　of　different　physiological　molecules　and　inorganic　ions.　Finally,　the　proposed　sensing　system　was　successfully　applied　to　assay　AA　in　real　samples　with　satisfactory　results.　(C)　2015　Elsevier　B.V.　All　rights　reserved.