Flower-like tailored carbon nitride oligomer as an excellent aggregation-induced electrochemiluminescence emitter for sensitive immunoassay of neuron-specific enolase via dual quenching by bimetallic phenolic networks

The adjustment of the electrochemiluminescence (ECL) of polymeric carbon nitride (C₃N₄) is essential for its application in sensitive immunoassays. However, such modification through aggregation-induced emission (AIE) has not yet been reported. Herein, aggregation-induced ECL in C₃N₄ oligomer (CNO) was induced through the introduction of a rotatable imine moiety, with the resulting material exhibiting excellent performance in the targeted immunodetection of neuron-specific enolase. Phenyl-modified CNO was synthesized through one-step pyrolysis at a reduced temperature. The rotatable benzene ring and triazine group formed a dynamic structure, which exhibited strong aggregation in water-doped solvents. compared to unmodified graphitic C₃N₄, CNO demonstrated higher intrinsic ECL efficiency and more readily accessible ECL signals. AIE inducing polymerization was conducted via nanoprecipitation, and the resulting CNO micro-flowers were employed as a sensing platform. A CNO-based sensor was prepared by combining CNO micro-flowers with copper-based bimetallic phenolic network nanoparticles as a quencher. Sensitive signal quenching was achieved owing to the electron transfer of Cu²⁺ and antioxidation properties of polyphenolic structures. The prepared sandwich-type immunosensor for neuron-specific enolase showed a limit of detection of 0.12 pg/mL in the detection range of 0.001-100 ng/mL. This study presents an effective strategy for the ECL signal amplification of C₃N₄, which is conducive to fundamental research in ECL and the application of the proposed sensor in the early diagnosis of diseases.