▎ 摘　　要

Recently, more and more attentions have been paid to the sensitive and selective determination of uranyl ion (UO22+) in environmental water due to its high toxicity and radiotoxicity. The accurate and sensitive determination of UO22+ has been readily performed in the well-equipped laboratories; however, it is still a challenging task for the on-site analysis of UO22+. To address this issue, in the present work, a novel and smart nanosystem based on DNAzyme and graphene oxide (GO) is proposed for the turn-on fluorescent sensing of UO22+ by combining the excellent selectivity of DNAzyme toward UO22+, the super fluorescence quenching ability of GO, and the unique affinity of GO toward DNAs with different structures. The proposed DNAzyme/GO nanosystem displays outstanding analytical performance in terms of wide dynamic response range (0.1-40 nM), low limit of detection (25 pM) and good selectivity over other metal ions. Furthermore, this nanosystem is successfully applied for the UO22+ detection in water samples with satisfactory results, demonstrating its great potential in the environmental monitoring.