Surficial Au-S Bond Energy Repetitively Exciting Gold Nanoparticles for Enhanced Chemiluminescence Photons per Luminophore and Automatic Single-Molecule Immunoassay.

Nanoparticles (NPs) are alternative chemiluminescence (CL) luminophores to molecular luminophores and are strongly anticipated to extend molecular luminophore-tagged commercial CL immunoassays (CLIA) with wavebands beyond the eye-visible region and sensitivity beyond the pg/mL level. Herein, a surficial bond-involved repetitive excitation strategy for near-infrared CL with enhanced photons per luminophore is proposed by exploiting l-methionine (l-Met)-capped gold NPs (AuNPs) as luminophores. The surficial Au-S bonds of l-Met@AuNPs can be involved in the procedure of NP core excitation via oxidation, and bring out defect-involved CL around 830 nm. Because there are plenty of Au-S bonds on every AuNP core, l-Met@AuNPs can be repetitively excited over a hundred times and give off greatly enhanced CL photons per luminophore than all molecular CL luminophores. CL of l-Met@AuNPs/(NH4)2S2O8 can directly enable automatic near-infrared CLIA for myoglobin (MYO) determination on in vitro diagnostic instruments, with a limit of detection of 10 fg/mL (S/N = 3), which significantly surpasses the threshold of molecular luminophores. This Au-S bond-triggered AuNP CL strategy not only offers an alternative to molecular CL strategies with improved sensitivity and to II-VI NP CL strategies with fewer toxic concerns, but also indicates that exploiting the surficial bond energy of NPs could be an alternative to designing NPs with unique morphology, structure, and composition in the CL domain.