Development of a ratiometric N-CDs/RhB fluorescent probe for selective and sensitive detection of arginine and...

Arginine (Arg) and ascorbic acid (AA) are essential nutrients that significantly impact human health. In this research, we introduced a novel N-CDs/RhB ratiometric fluorescent probe for sensitive detection of Arg and AA. The probe was constructed through simple physical mixing of rhodamine B (RhB) and nitrogen-doped carbon dots (N-CDs), leveraging fluorescence resonance energy transfer (FRET) between N-CDs and RhB. The optimal excitation wavelength for N-CDs was determined to be 440 nm, with fluorescence emission at 510 nm, while RhB exhibited excitation and emission peaks at 557 nm and 572 nm, respectively. The N-CDs/RhB probe demonstrated excellent stability across various pH values and salt concentrations, and under UV light exposure, allowing reliable performance under diverse conditions. The probe exhibited high selectivity and anti-interference properties, with no significant response to other amino acids or food additives. Its response to Arg and AA was characterized by an "on-off-on" mechanism, with fluorescence quenching upon the addition of Arg due to electrostatic adsorption and static quenching, and fluorescence recovery upon the addition of AA through a redox reaction that weakened the guanidinium-carboxylate bridge interaction. The probe demonstrated linear detection ranges of 0.7-60 µM for Arg and 7.7-220 µM for AA, with detection limits of 0.21 µM and 2.32 µM, respectively. Real-world testing in functional beverages further confirmed the practical applicability of the probe, with recovery rates for Arg and AA ranging from 97.44% to 100.83%. These results highlight the potential of the N-CDs/RhB ratiometric fluorescent probe for real-time, precise sequential detection of Arg and AA in complex samples.