Aptamer-mediated N/Ce-doped carbon dots as a fluorescent and resonance Rayleigh scattering dual mode probe for arsenic(III)

Carbon dots doped with N/Ce, N/Eu and N/Tb were prepared by a microwave based hydrothermal technique. The fluorescence of the N/Ce co-doped carbon dots (CD_N/Ce) is strongest. They have excitation/emission maxima at 340/441 nm. CD_N/Ce was characterized by scanning electron microscopy, infrared and fluorescence spectroscopy. On addition of the nucleic acid aptamer (Apt) against arsenic(III) in pH 7 solution, the blue fluorescence of the doped carbon dots is partially quenched due to electrostatic interaction. On addition of As(III), it will bind to the aptamer, and the carbon dots are released. Hence, fluorescence becomes gradually restored. In addition, the resonance Rayleigh scattering signal (measured at 340 nm) is reduced. This dual-mode assay works in the 0.5–5.8 μg·L⁻¹ As(III) concentration range and has a 0.2 μg·L⁻¹ detection limit.

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