A turn-on fluorescent sensor for Hg2+ detection based on graphene oxide and DNA aptamers

Herein, a facile and effective turn-on fluorescent sensor for Hg2+ detection was proposed, which is based on graphene oxide (GO) and DNA aptamers. In this assay, GO played a role as a nanoquencher to quench the fluorescence of acridine orange (AO). DNA aptamers (P2 and H-G4) acted as the molecular recognition probes, which could react with Hg2+ specifically and result in the formation of thymine-Hg2+-thymine (T-Hg2+-T) structures and a G-quadruplex. The G-quadruplex could absorb AO from the GO surface, leading to the fluorescence recovery of AO. Based on this recovery of the fluorescence signal, the target Hg2+ (0.5-50 nM) could be detected quantitatively, and the limit of detection (LOD) is 0.17 nM. This novel strategy will have great potential to monitor Hg2+ in the environment.