Overview
This methods paper describes the synthesis and validation of a dual-emission ratiometric fluorescent sensor (GQDs@AuNCs) constructed from nitrogen-doped graphene quantum dots (N-GQDs) and glutathione-stabilized gold nanoclusters (G-AuNCs) for simultaneous detection of Al3+ and Cu2+ in food matrices. The sensor was validated by spiked-recovery experiments in fried dough twists, deep-fried dough sticks (Chinese fried bread), scallops, and razor clams (Sinonovacula constricta) purchased in Shenyang, China. The paper does not report ambient (unspiked) Al3+ or Cu2+ concentrations in these food samples; it demonstrates method accuracy via recovery rates.
Key numbers
Detection parameters for Al3+: linear range 0.5–500 µM, LOD 0.66 µM (= approximately 17.8 µg/L or ~17.8 ppb in solution); linear range for Cu2+: 1–200 µM, LOD 0.44 µM (= approximately 28 µg/L in solution). R² = 0.9992 (Al3+), R² = 0.9973 (Cu2+).
Spiked recovery (Al3+) in food matrices: deep-fried dough sticks 99.44%–101.03%; fried dough twists 97.05%–100.48%. Spiked recovery (Cu2+): scallops 96.9%–102.96%; Sinonovacula constricta 90.04%–102.02%. Spiking concentrations: 10 µM, 50 µM, 100 µM.
No endogenous (ambient) Al or Cu concentrations in the food samples are reported. The study does not provide a baseline measurement of Al in the fried dough products; recoveries were calculated from the spiked increment only.
Methods
G-AuNCs synthesised by reducing HAuCl4 with glutathione (GSH) at 80 °C for 24 h. N-GQDs prepared by hydrothermal treatment of graphene oxide (GO) with ammonia at 160 °C. GQDs@AuNCs formed by electrostatic self-assembly. Detection principle: Al3+ produces aggregation-induced emission (AIE) enhancement of G-AuNCs at 528 nm; Cu2+ causes fluorescence quenching of G-AuNCs via charge transfer. N-GQDs emission at 412 nm remains stable as internal reference. Sample preparation: 0.5 g food digested in concentrated HNO3 + 30% H2O2 by microwave (20 min), diluted to 50 mL. Al3+ and Cu2+ standard solutions added at three concentrations. Fluorescence spectrophotometer detection.
Food matrix scope is limited to Chinese fried dough products and shellfish. Selectivity against common interfering ions (Fe3+, K+, Na+, Ca2+, Mn2+, Zn2+, Ba2+, Mg2+) confirmed.
Implications
Certification: This paper provides no ambient Al concentration data usable for contamination profiling. It is a methods-validation study and contributes primarily to understanding of detection technology for Al in high-starch fried foods and shellfish. The fried dough product category is relevant to Al accumulation because alum-based leavening agents (potassium aluminum sulfate, ammonium aluminum sulfate) are used in Chinese fried dough products and are a known source of dietary Al exposure.
Courses: Demonstrates portable fluorescence sensing as an emerging alternative to ICP-OES and AAS for food Al monitoring. Useful for discussion of rapid in-field testing technologies.
App: No ambient concentration data; does not contribute to contamination_profile values.
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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 |