Silver Ion–Regulated Luminescence of Chiral Au-Cysteine Nanoflowers for Highly Effective Enantioselective Recognition of Glutamine

Abstract

Rapid and highly effective enantioselective recognition of amino acid enantiomers remains a significant challenge in luminescent sensing. Herein, we develop a silver ion–regulated luminescent sensing platform based on chiral Au-d-Cysteine nanoflowers (Au-d-Cys NFs) for the recognition of glutamine enantiomers. Ag+ coordinates with the amino and carboxyl groups of the ligand, enhancing and modulating ligand-to-metal charge transfer (LMCT) emission of Aud-Cys NFs, while inducing an emission blue shift from 575 to 545 nm. On this basis, the system exhibits distinctly different luminescence responses toward d-Glutamine (d-Gln) and l-Glutamine (l-Gln). d-Gln efficiently quenches the luminescence, whereas l-Gln induces only minimal changes, enabling a high enantioselective discrimination factor of up to 22.25 and allowing quantitative analysis of enantiomeric excess. The recognition process is rapid, reaching completion within 5 min, and permits intuitive visual discrimination under ultraviolet illumination. Mechanistic studies reveal that Ag+-mediated coordination modulation enhances the system’s sensitivity to differential enantiomer interactions, which is critical for achieving efficient recognition. This work establishes a coordination-regulated chiral luminescent sensing strategy and provides a new analytical approach for the design of enantioselective sensing systems.