Single-layer　graphene　quantum　dots　(SGQDs)　were　refluxed　with　hydrazine　(N2H4)　to　prepare　hydrazide-modified　SGQDs　(HM-SGQDs).　Compared　with　SGQDs,　partial　oxygen-containing　groups　have　been　removed　from　HM-SGQDs.　At　the　same　time,　a　lot　of　hydrazide　groups　have　been　introduced　into　HM-SGQDs.　The　introduced　hydrazide　groups　provide　HM-SGQDs　with　a　new　kind　of　surface　state,　and　give　HM-SGQDs　unique　photoluminescence　(PL)　properties　such　as　blue-shifted　PL　emission　and　a　relatively　high　PL　quantum　yield.　More　importantly,　the　hydrazide-modification　made　HM-SGQDs　have　abundant　luminol-like　units.　Accordingly,　HM-SGQDs　exhibit　unique　and　excellent　chemiluminescence　(CL)　and　anodic　electrochemiluminescence　(ECL).　The　hydrazide　groups　of　HM-SGQDs　can　be　chemically　oxidized　by　the　dissolved　oxygen　(O2)　in　alkaline　solutions,　producing　a　strong　CL　signal.　The　CL　intensity　is　mainly　dependent　on　the　pH　value　and　the　concentration　of　O2,　implying　the　potential　applications　of　HM-SGQDs　in　pH　and　O2sensors.　The　hydrazide　groups　of　HM-SGQDs　can　also　be　electrochemically　oxidized　in　alkaline　solutions,　producing　a　strong　anodic　ECL　signal.　The　ECL　intensity　can　be　enhanced　sensitively　by　hydrogen　peroxide　(H2O2).　The　enhanced　ECL　intensity　is　proportional　to　the　concentration　of　H2O2in　a　wide　range　of　3　μM　to　500　μM.　The　detection　limit　of　H2O2was　calculated　to　be　about　0.7　μM.　The　results　suggest　the　great　potential　applications　of　HM-SGQDs　in　the　sensors　of　H2O2and　bio-molecules　that　are　able　to　produce　H2O2in　the　presence　of　enzymes.　This　journal　is　©　the　Partner　Organisations　2014.