Overview
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.
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Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.
| Commit | Date | Change | Description |
|---|---|---|---|
| a8052bb | 2026-08-09 | major | 6 sections added; narrative text revised |