Co-Reactant Engineering for Au Nanocluster Electrochemiluminescence.

Co-reactants are essential in co-reactant-based electrochemiluminescence (ECL) systems because they generate reactive intermediates that can oxidize or reduce ECL luminophores, thereby driving ECL emission. In the context of ECL, gold nanoclusters (Au NCs) have emerged as innovative luminophores, owing to their tunable electronic structures and excellent biocompatibility. However, their efficiency in ECL applications is often compromised by challenges such as limited excited-state generation and non-radiative losses. To tackle these practical challenges, advanced co-reactant engineering strategies have been developed to improve the performance of Au NCs in ECL systems. This review begins with a brief overview of the mechanisms of ECL. Subsequently, a systematic overview of various co-reactant engineering strategies is presented, including: (1) using innovative co-reactants to replace traditional ones due to their lower toxicity and better biocompatibility; (2) applying co-reaction accelerators to reduce the onset potential and improve the production of reactive intermediates from co-reactants; (3) combining co-reactants with luminophores or creating integrated nanostructure assemblies of co-reactants, co-reaction accelerators, and luminophores to achieve shorter electron transfer paths and reduced energy loss for stable high-intensity ECL emission; (4) utilizing host-guest strategies that encapsulate co-reactants within cavities to stabilize radical intermediates and minimize environmental quenching. This review provides a comprehensive overview of recent developments in co-reactant engineering for Au NCs-based ECL systems, thereby encouraging further exploration and understanding of these systems and expanding their potential applications.