This work describes an aptamer based method for highly sensitive determination of Hg(II). A Hg(II)-binding ssDNA aptamer was linked to silica-coated magnetic nanoparticles (magNPs). Then, a conjugate composed of graphene and CdS quantum dots (GrCdS) was linked to the complementary ssDNA. On mixing the two components, a duplex of type magNP-dsNNA-Gr/CdS is generated. If Hg(II) is added, it wills capturing the aptamer, and this leads to the release of Gr/CdS because of the formation of a stablethymine-Hg2+-thyminelink.Externalmagneticforceisusedtoremovetheremainingcomplex.Thereleasedgraphene-CdSis decomposedbyHNO3 andinjectedinto agraphite furnace AAS.The detectableamount of Cd is proportional totheconcentration of Hg(II) in the sample. Under the optimal conditions, the method has a linear response in the 2.50 aM to 0.25 nM Hg(II) concentrationrange,andthedetectionlimitisaslowas7.6aM(atS/N=3).IthashighselectivityforHg(II)overothermetalions.
