Kayani 2025 — Ratiometric fluorescence probe for Hg2+ detection in water
This paper reports the development of a dual-emission carbon dot (CD) ratiometric fluorescence probe combining green-emitting CDs (g-CDs, synthesized from 2,3-dihydroxyquinoxaline) and red-emitting CDs (r-CDs, from cellulose in phosphoric acid) for selective detection of Hg2+ in water. The sensor operates by quenching green fluorescence at 520 nm in the presence of Hg2+ while the red emission at 600 nm serves as an internal reference. Real sample validation was conducted on tap and bottled water with recovery values of 96.8–105.7% (RSD 1.1–2.5%, n=3). The method is applied to environmental water matrices only; no food matrix application is reported.
Key numbers
- LOD (fluorimetric): 60 nM (water matrix)
- LOD (smartphone visual): 26.68 mM (visual colorimetric mode, smartphone-based)
- Linear range: 2–16 µM Hg2+
- R2 = 0.9966 (linear range)
- Particle size: g-CDs ~1.1 nm; r-CDs ~1.2 nm
- Excitation wavelength: 400 nm
- Selectivity: negligible interference from Co2+, Zn2+, Cr3+, Ni2+, Mg2+, Mn2+, Fe2+, Cd2+, Cu2+, glucose, ascorbic acid, and several amino acids tested at 100 µM (10× Hg2+ concentration)
- Tap water recovery: 96.84–100.27%; bottled water recovery: 101–105.72%
Methods (brief)
Ratiometric fluorescence spectroscopy using dual-emission carbon dot nanocomposite; smartphone RGB image analysis (Color Grab app, 365 nm UV lamp) as a portable visual alternative; ICP-MS, AAS, and electrochemistry cited as conventional comparators in the introduction.
Implications
Certification: Limited direct relevance; this probe is designed for environmental water monitoring, not food matrices. Water-based Hg detection methods may be relevant for irrigation water or processing water quality assurance. Courses: Useful as a case study for low-cost, portable heavy metal detection methods and greenness assessment frameworks (AGREE, BAGI, RAPI metrics demonstrated). App: Not applicable; no food concentration data reported.