Enhanced Electrochemiluminescence of Zn ²⁺ Aggregation-Induced Dual Stabilizers Capped Au Nanoclusters and Its Immunosensing Applications

Screening a novel electrochemiluminescence (ECL) system with enhanced ECL efficiency is crucial to ECL evolution. Aggregation-induced short-chain Au nanoclusters (AuNCs) are an intriguing strategy to tune their ECL properties. However, achieving superior ECL efficiency involving an aggregation-induced strategy of long-chain stabilizer-capped AuNCs in aqueous phase remains a formidable challenge. Herein, the high ECL efficiency of AuNCs was synthesized from Zn²⁺-mediated aggregation-induced AuNCs involved in short/long chain ligands including d-penicillamine/11-mercaptoundecanoic acid (d-DPA/MUA) as dual stabilizers and <i>tert</i>-butylamine borane as reductant (Zn²⁺-d-DPA/MUA@AuNCs). Specifically, the formation of aggregation-induced superstructures resulted in nearly complete quenching of vibrations and dipole moments of the -CH₂- moieties in MUA, which was attributed to the conformational contraction of the overall structure and constrained intramolecular motion. Moreover, with the addition of Zn²⁺ into the d-DPA/MUA@AuNCs, the morphology of spheroidal assembled structure grew up, the carrier concentration of the AuNCs increased, the electron-hole recombination at the interface was promoted, and thus the carrier separation efficiency decreased. This was beneficial to the enhanced NIR (beyond 800 nm) ECL around 9-fold compared with Zn-free AuNCs. Zn²⁺-d-DPA/MUA@AuNCs were utilized as a probe for the detection of prostate-specific antigen (PSA) in the linear concentration range 5-800 ng/mL with a limit of detection of 1 ng/mL (S/N = 3) with ECL image and wavelength-based intensity dual mode.