Ligand‐induced Assembly of Copper Nanoclusters with Enhanced Electrochemical Excitation and Radiative Transition for Electrochemiluminescence**

Abstract Copper nanoclusters (CuNCs) are emerging electrochemiluminescence (ECL) emitters with unique molecule‐like electronic structures, high abundance, and low cost. However, the synthesis of CuNCs with high ECL efficiency and stability in a scalable manner remains challenging. Here, we report a facile gram‐scale approach for preparing self‐assembled CuNCs (CuNCs Assy ) induced by ligands with exceptionally boosted anodic ECL and stability. Compared to the disordered aggregates that are inactive in ECL, the CuNCs Assy shows a record anodic ECL efficiency for CuNCs (10 %, wavelength‐corrected, relative to Ru(bpy) 3 Cl 2 /tripropylamine). Mechanism studies revealed the unusual dual functions of ligands in simultaneously facilitating electrochemical excitation and radiative transition. Moreover, the assembly addressed the limitation of poor stability of conventional CuNCs. As a proof of concept, an ECL biosensor for alkaline phosphatase detection was successfully constructed with an ultralow limit of detection of 8.1×10 −6 U/L.