Fluorescent carbon quantum dots from Syzygium aromaticum as a selective sensor for Fe3+ and Cd2+ detection in aqueous solution

Fluorescent carbon quantum dots (SA-CQDs) from Syzygium aromaticum were synthesized via carbonization-assisted ultrasonication, exhibiting an average size of 3.314 nm and strong blue fluorescence at 440 nm (excitation: 350 nm) with a quantum yield of 12.61 %. FTIR and UV–vis confirmed oxygen-containing functional groups, enhancing metal ion interactions. SA-CQDs showed selective fluorescence quenching for Fe 3+ (89.7 %) and Cd 2+ (84.8 %). Sensitivity analysis revealed linearity (R 2 = 0.988 for Fe 3+ , R 2 = 0.994 for Cd 2+ ) with detection limits of 0.515 μM and 0.403 μM, respectively. High recovery rates (95.10–100.23 %) in real water samples confirmed reliability for water quality monitoring. • SA-CQDs selectively detect Fe 3+ and Cd 2+ with strong fluorescence quenching. • High sensitivity with low detection limits of 0.515 μM (Fe 3+ ) and 0.403 μM (Cd 2+ ). • Stable fluorescence in real water samples with high recovery and low RSD values. • Cost-effective sensor for heavy metal detection in aqueous environments.