▎ 摘　　要

A novel disposable and portable electrochemical aptasensor based on reduced graphene oxide (RGO) was constructed for the detection of mercury (II) (Hg2+) using methylene blue (MB) as the signal tag and exonuclease III-induced cyclic reaction as signal amplification strategy. RGO was utilized as a carrier to immobilize MB-DNA, and screen-printed electrode (SPE) was used as the substrate electrode. The whole reaction was carried out in a homogeneous system, and finally, the target was detected directly in the solution using SPE, which did not require multiple fixation steps and simplified the experimental process. Under the optimized conditions, the developed electrochemical aptasensor had a wide linear range of 0.01-300 nmol L-1 with a low detection limit of 0.009 nmol L-1 and was successfully used for the determination of Hg2+ in tap water samples. Furthermore, the aptasensor exhibited good stability and high selectivity. It had good application prospects in the detection of harmful substances in food.