▎ 摘　　要

Lead is one of the toxic heavy metal ions which seriously threatens the environment and human health, even at ultra-trace level. Here, an innovative fluorescent sensor based on DNAzymes coupling with multi-cycle strand displacement amplification (M-SDA) and nano-graphene oxide (GO) was established for the first time to ultra-sensitively detect lead, which is the first attempt to combine biological nucleic acid amplification technology with GO to detect heavy metal ions. There are several advantages. Firstly, the high selectivity of DNAzymes endow the proposed sensor outstanding specificity. Secondly, the introduction of M-SDA let the proposed sensor own the high potential for ultra-sensitive detection of Pb2+. Compared with traditional SDA, the amplification efficiency of M-SDA is greatly enhanced due its intermediate products are able to induce another SDA. Thirdly, the using of GO in fluorescence ion sensor is simple and fast. Under the optimal experimental conditions, the proposed sensor exhibited a good linear from 0.01 nM to 850 nM (R-2=0.99714) with the detection limit as low as 6.7 pM. Additionally, the proposed sensor could be applied to detect the real samples with good accuracy and reliability.