Nitrogen and sulfur co-doped photoluminescent carbon dots for highly selective and sensitive detection of Ag + and Hg 2+ ions in aqueous media: Applications in bioimaging and real sample analysis.

In this study, we report the synthesis of photoluminescent (PL) nitrogen (N) and sulfur (S) co-doped carbon dots (NS-CDs) from nitazoxanide and 3-mercaptopropionic acid as a precursors via a one-pot hydrothermal methods. N and S co-doped materials allows more active sites in the CDs surface resulting in an enhancement of their PL properties. NS-CDs show bright blue PL, excellent optical properties, good water solubility, and a high quantum yield (QY) of 32.1%. The as-prepared NS-CDs were confirmed by UV-Visible, photoluminescence, FTIR, XRD and TEM analysis. An optimized excitation at 345 nm, the NS-CDs exhibited strong PL emission at 423 nm with an average size of 3.53 ± 0.25 nm. Under optimized conditions, the NS-CDs PL probe shows high selectivity with Ag ⁺ /Hg ²⁺ ions detected, while other cations no significant changes the PL signal. The PL intensity of NS-CDs linearly quenching and enhancement with Ag ⁺ and Hg ²⁺ ions from 0 to 50 × 10 ^-6  M, with the detection limit of 2.15 × 10 ^-6  M and 6.77 × 10 ^-7  M (S/N = 3). More interestingly, as-synthesized NS-CDs shows a strong binding to Ag ⁺ /Hg ²⁺ ions with the PL quenching and enhancement to precise and quantitative detection of Ag ⁺ /Hg ²⁺ ions in living cells. The proposed system was effectively utilized for the sensing of Ag ⁺ /Hg ²⁺ ions in real samples resulting in high sensitivity and good recoveries (98.4-109.7%).
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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