Dual detection of Malation and Hg (II) by fluorescence switching of graphene quantum dots
2018
Roushani, Mahmoud | Kohzadi, Sahar | Haghjoo, Sarah | Azadbakht, Azadeh
The present study investigates sensitive and selective “off–on” method to analyze and detect mercury ions (Hg²⁺) and Malation pesticide using graphene quantum dots (GQDs) as a new fluorescent (FL) probe. When GQDs are present, Hg²⁺ cations are capable of being coordinated on the GQD surface by their negatively charged surface. The process of absorption occurs using electrostatic interactions. Hence, the FL of the GQDs would be remarkably quenched (turn-off) at 463 nm for 1 μM Hg²⁺ as a result of FL charge transfer. Nevertheless, when 40 μM of Malation is added to the GQDs-Hg²⁺ solution, the FL of the GQDs enhances significantly at 463 nm (turn-on), since Hg²⁺ is combined with SR- group in the Malation rather than with the GQDs in the aqueous solution. Instead of the weak electrostatic interaction, a strong metal-thiol bond interaction is formed between Hg²⁺ and Malation and an enhancement in the FL of GQDs is observed. Finally, acceptable linearity for Hg²⁺ and Malation detection is obtained in the concentration ranges of 1–10 μM and 10–80 for Hg²⁺ and linear range of 80–120 μM for Malation with an LOD of 0.5 μM and R² = 0.99.
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