A Facile Synthetic Approach toward Obtaining N-Doped Carbon Quantum Dots from Citric Acid and Amino Acids, and Their Application in Selective Detection of Fe(III) Ions

This work reports the preparation of amino acid-functionalized CQDs from citric acid by facile hydrothermal synthesis. The prepared N-doped exhibited excellent optical, physical, and chemical properties, differences were observed among six different acids used as nitrogen dopants (Leu, Trp, Lys, Arg, Ala, His). Compared to blank sample (without addition acids), have shown significantly higher quantum yield, also demonstrating potential in metal ion sensing. highest yield 36.45%, with a peak excitation/emission 340/406 nm, was achieved using Leu (CQD@Leu), treated at temperature 180 °C during 9 h. samples investigated toward selectivity (Ca2+, Cu2+, Fe3+, K+, Hg2+, Mg2+, Al3+, Mn2+, Na+), CQD@Leu showed selective sensitive response upon Fe3+ ions. Therefore, selected for further investigation detection model system real well water samples. A developed described logistic function good coefficient determination R2 = 0.9982, while linear range determined concentration 0.3 mol dm−3 30 dm−3, limit LOD 1.77 ± 0.01 quantification LOQ 5.89 0.04 dm−3. Furthermore, results vitro cytotoxicity test (MTT) normal tumor cell lines (MRC-5, HeLa, NCI-H358, CaCo-2) clearly demonstrate biocompatibility CQD@Leu.