Hierarchically Organized Particles with Chirality-Regulating Assembly Restrictions for Enhanced Electrochemiluminescence

Electrochemiluminescence (ECL) efficiency depends on charge transfer between emitters and coreactants, but random collisions often make this transfer uncontrolled. Herein, we demonstrate that chirality-directed assembly could modulate the morphology of hierarchically organized particles (Au-Cys HOPs), generating an intense local electric field that accelerates electron transfer and enhances ECL. Using L/d-cysteine (Cys) as chiral ligands, we synthesize Au-Cys HOPs from polydisperse gold thiolate nanoplatelets, yielding radially organized twisted spikes. These spiky architectures exhibit a stronger built-in electric field (BIEF) than spherical Au-TGA particles (synthesized with achiral thioglycolic acid), facilitating rapid electron transfer and significantly improved ECL. In contrast, kayak-shaped Au-dl-Cys HOPs synthesized with racemic dl-Cys exhibit a smooth morphology devoid of spiky features, whereas Au-TGA particles entirely lack hierarchical organization. Thus, the Au-Cys HOPs exhibit strong anodic ECL emission with high efficiency (25.52%) with on-electrode preoxidation of radical ions (using TPrA as a coreactant), surpassing Au-dl-Cys HOPs and Au-TGA particles by 3.6- and 170.1-fold, respectively. An efficient ECL sensing platform is constructed using Au-Cys HOPs for achieving enantioselective recognition of tryptophan (Trp) isomers (Id-Trp/Il-Trp = 2.29), with a detection limit of 0.16 nM for l-Trp. This work demonstrates chirality's critical role in nanostructure design for efficient ECL and chiral sensing applications.