A　highly　sensitive　electrochemiluminescent　detection　method　for　lead　ions　(Pb(II))　was　fabricated　based　on　the　distance-dependent　quenching　of　the　electrochemiluminescence　from　CdSe　quantum　dots　by　nanocomposites　of　graphene　and　gold　nanoparticles.　Graphene/gold　nanoparticles　were　electrochemically　deposited　onto　a　glassy　carbon　electrode　through　the　constant　potential　method.　Thiol-labeled　DNA　was　then　assembled　on　the　surface　of　the　electrode　via　gold-sulfur　bonding,　following　which　the　amino-labeled　terminal　of　the　DNA　was　linked　to　carboxylated　CdSe　quantum　dots　by　the　formation　of　amide　bonds.　The　27-base　aptamer　was　designed　with　two　different　domains:　the　immobilization　and　detection　sequences.　The　immobilization　sequence　was　paired　with　12　complementary　bases　and　immobilized　on　the　gold　electrode;　the　single-stranded　detection　sequence,　rich　in　G　bases,　formed　a　G-quadruplex　(G4)　structure　in　the　presence　of　Pb2+.　The　formation　of　G4　shortens　the　distance　between　the　CdSe　quantum　dots　and　the　Au　electrode,　which　decreases　the　electrochemiluminescent　intensity　in　a　linear　fashion,　proportional　to　the　concentration　of　Pb(II).　The　linear　range　of　the　sensor　was　10(-10)　to　10(-8)　mol/L　(R　=　0.9819)　with　a　detection　limit　of　10(-10)　mol/L.　This　sensor　detected　Pb(II)　in　real　water　samples　with　satisfactory　results.　(C)　2015　Elsevier　B.V.　All　rights　reserved.