Highly Chiroptical Detection with Gold–Silver Bimetallic Nanoclusters Circularly Polarized Luminescence Based on G-quartet Nanofiber Self-assembly

Circularly polarized luminescence (CPL) as an intriguing luminescence phenomenon has attracted significant research interests for their chiroptical application, and CPL-active materials have been extensively explored in recent years. Herein, a highly chiroptical sensor was fabricated by the coassembly of G-quartet nanofiber and gold–silver bimetallic nanoclusters. In this, the adenosine 5′-monophosphate (AMP) templated gold–silver bimetallic nanoclusters (AuAg NCs) exhibited an enhanced fluorescence (λex = 356 nm, λem = 475 nm), a 9.42% quantum yield, and a 3.8 μs decay time compared with AMP stabilized Au NCs. In addition, a helical G-quartet-based nanofiber structure (g-fiber) was formed based on the self-assembly of guanosine 5′-monophosphate (GMP). The g-fiber was employed as chiral template for CPL emission by decorating AuAg NCs. Most interesting, the opposite CPL emission was regulated by K+ ion. The dissymmetry factor (glum) of this CPL-active material was up to 10–2. Furthermore, a CPL sensor based on the CPL emission has been developed for l-cysteine detection due to the quenching effect on AuAg NCs. The limit of detection (LOD) was as low as 95.7 nM, ranging from 0.1 to 8 μmol L–1, which was comparable with other analytical methods and materials. Our design presents a new horizon for nanoclusters and provides an entirely new approach for bioassay application.