<p> A highly efficient electrochemiluminescence (ECL) aptasensor has been developed for the detection of contact pestizide diazinon (DZN) residues in vegetables. The sensor utilized tris(2,2’-bipyridine)ruthenium(II) as a luminescent probe and synthetic silver-copper nanoclusters (PEI-Ag/CuNCs) on a polyethyleneimine (PEI) scaffold. The film-forming properties of PEI improved the structural and operational stability of the sensor. The amine-rich PEI acted as an efficient ECL co-reactant for the Ru(bpy)₃²⁺ luminophore, which was pre-immobilized in a chitosan film. The embedded Ag/Cu nanoclusters served as a linkage platform for the aptamer. This integrated design simplified the sensor assembly process. Integrated with an indium tin oxide (ITO) electrode and smartphone-based readout, this visual and intelligent ECL aptasensor achieved a wide detection range from 1.0 to 10⁶ pg mL^− 1 and a low limit of detection of 0.3 pg mL^− 1. The sensor exhibited high specificity against common interfering pesticides and achieved satisfactory recoveries ranging from 91.48% to 113.20% in spiked vegetable extracts, demonstrating its practical applicability. This work provides a simple, sensitive and portable approach to the detection of pesticide residues such as DZN and highlights the potential of ECL technology in food safety applications.</p> Graphical Abstract <p></p>