Fluorescent aptamer-functionalized graphene oxide biosensor for label-free detection of mercury(II)

Label-free fluorescent detection of Hg2+ has been realized via quenching of fluorescence of graphene oxide (GO). The water-soluble GO sheets, which are functionalized with single-stranded DNA aptamer, exhibit strong fluorescence emission at 600nm under the excitation of 488nm in the absence of Hg2+ ions. When Hg2+ ions appear in the aqueous solution, Hg2+ ions are sandwiched between the hairpin-shaped double-stranded DNA due to the formation of the thymine–Hg2+–thymine complex, which holds the Hg2+ ions in proximity to the surface of GO sheets. As a result, the fluorescence emission of GO is quenched. The present GO-based sensor shows a limit of detection as low as 0.92nM and excellent selectivity toward Hg2+ over a wide range of metal ions. The present work indicates that GO is a promising fluorescent probe for detection of metal ions and biomolecules. ► An aptamer-functionalized graphene oxide shows strong fluorescence. ► The quenching of fluorescence of graphene oxide is due to the charge transfer from graphene oxide to Hg(II) ions. ► The label-free sensor fluorescent shows a limit of detection of 0.92nM and excellent selectivity toward Hg(II) ions.