N, S-doped carbon dots/chiral ionic liquid composites for enhanced electrochemical recognition of tryptophan enantiomers.

Rapid detection of tryptophan (Trp) enantiomers has been a research hotspot in pharmaceuticals, life sciences, and related fields. Herein, N, S-doped carbon dots (N, S-CDs) and chiral ionic liquid (CIL) were used to functionalize the glassy carbon electrode (GCE), constructing a simple electrochemical sensor (N, S-CDs/CIL/GCE) for the efficient recognition of Trp enantiomers. CIL not only provides a chiral microenvironment but also synergistically amplifies electrochemical signals through electrostatic interactions with N, S-CDs, while enhancing interfacial electron transfer efficiency. Differential pulse voltammetry (DPV) analysis indicates that with an 8.0 μL loading volume and pH 6.0, the N, S-CDs/CIL/GCE achieves the maximum enantiomeric selectivity coefficient (IL/ID = 2.12) for L-Trp versus D-Trp. Moreover, it exhibits excellent stability and shows high selectivity toward Trp enantiomers even in the presence of common interfering substances, with detection limits of 0.035 mM and 0.084 mM for L-Trp and D-Trp, respectively (1.5 to 3.5 mM). Mechanistic investigations suggest that the DPV signal difference may stem from the stereoselectivity of N, S-CDs/CIL toward tryptophan isomers, as its affinity for L-Trp is higher than for D-Trp. Furthermore, the N, S-CDs/CIL/GCE exhibits significant potential for distinguishing amino acid isomers in non-racemic mixtures. This study offers new insights into the development of chiral compound sensors and bioanalytical strategies.