Surface-Defect-Involved Chemiluminescence Boosted by Gold–Silver Bimetallic Nanoclusters for Bioanalysis

Chemiluminescence (CL) as a powerful analytical tool has garnered increasing interest. However, traditional molecular-based CL luminophores suffer from low emission efficiency due to limited total CL photons emitted per luminophore, driving efforts to explore amplified strategies or novel probes to boost the emission. Although metal nanoclusters (NCs) as luminescent nanoprobes have been extensively studied for electrochemiluminescence and photoluminescence (PL) owing to their intriguing luminescent properties, the CL performance using metal NCs as emitters is often ignored. Herein, based on the synergistic effect within the bimetallic NCs, a series of glutathione-coated Au-Ag bimetallic NCs (GSH-AuAg NCs) were optimized by adjusting precursor ratios and achieved the maximum CL response at a Au:Ag molar ratio of 5:1. To our surprise, CL emission with GSH-AuAg NCs as emitters was triggered with oxidant reagents such as KMnO4, and bimetallic NCs display boosted CL emission (ca. 6.2-fold) compared to monometallic NCs owing to the synergistic effect on enhancing the emission efficiency. Surface-defect-involved CL was revealed by collecting the CL spectra with a maximum emission wavelength of around 750 nm and an obvious red shift of 140 nm compared to PL spectra. The mechanism reveals the KMnO4-injected hole into the valence band through redox reactions with GSH ligands, leading to CL emission by efficient radiative charge recombination with pre-existing electron. A sensing platform based on the GSH-AuAg NCs/oxidant system was constructed for sensing H2O2 and glucose, demonstrating the potential of GSH-AuAg NCs as CL emitters in analytical applications.