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Determination of Hg2+ and Cu2+ ions by dual-emissive Ag/Au nanocluster/carbon dots nanohybrids: Switching the selectivity by pH adjustment

Babaee, Elaheh, Barati, Ali, Gholivand, Mohammad Bagher, Taherpour, Avat (Arman), Zolfaghar, Narges, Shamsipur, Mojtaba
Journal of hazardous materials 2019 v.367 pp. 437-446
carbon quantum dots, chelating agents, color, copper, fluorescence, gold, mercury, metal ions, mineral water, nanogold, nanohybrids, pH, silver
An innovative dual-emissive ratiometric nanohybrid probe comprised of red-emitting a (Ag/Au)@insulin nanoclusters (NCs) and blue-emitting carbon dots (CDs) was designed for sensitive and selective ratiometric determination of Hg2+ and Cu2+ ions.The fluorescence intensity of CDs (λex = 340 nm; λem = 420 nm) was unaffected in the presence of the metal ions tested, whereas the red emitting NCs (λex = 340 nm; λem = 640 nm) was strongly quenched by both Cu2+ and Hg2+ ions. Interestingly, the selectivity of the probe toward these two ions was simply switched by controlling the pH of probe solution without using any chelating agent. The probe selectively responded to Hg2+ ions at acidic condition (pH = 4.0), Cu2+ ions at basic condition (pH = 10.0), and Hg2+-Cu2+ mixtures at pHs within this range. The respective detection limitsfor determination of Cu2+ and Hg2+ ions at their specific pH conditions were estimated as 5 nM and 7 nM, over linear ranges of 20–600 nM and 20–2000 nM, respectively. The fabricated ratiometric probe also showed distinguished fluorescence color changes to visual detection of these ions. Finally, the probe was successfully applied to determination of Hg2+ and Cu2+ ions in tap and mineral water samples.