Highly sensitive, selective, and rapid fluorescence Hg2+ sensor based on DNA duplexes of poly(dT) and graphene oxide

Coupling T base with Hg2+ to form stable T-Hg2+-T complexes represents a new direction in detection of Hg2+. Here a graphene oxide (GO)-based fluorescence Hg2+ analysis using DNA duplexes of poly(dT) that allows rapid, sensitive, and selective detection is first reported. The Hg2+-induced T-15-(Hg2+)(n)-T-15 duplexes make T-15 unable to hybridize with its complementary A(15) labelled with 6'-carboxyfluorescein (FAM-A(15)), which has low fluorescence in the presence of GO. On the contrary, when T-15 hybridizes with FAM-A(15) to form double-stranded DNA because of the absence of Hg2+, the fluorescence largely remains in the presence of GO. A linear range from 10 nM to 2.0 mu M (R-2 = 0.9963) and a detection limit of 0.5 nM for Hg2+ were obtained under optimal experimental conditions. Other metal ions, such as Al3+, Ag+, Ca2+, Ba2+, Mg2+, Zn2+, Mn2+, Co2+, Pb2+, Ni2+, Cu2+, Cd2+, Cr3+, Fe2+, and Fe3+, had no significant effect on Hg2+ detection. Moreover, the sensing system was used for the determination of Hg2+ in river water samples with satisfactory results.