Intra-Unit Charge Transfer Synergized with Multivalent Reversible Redox Cycle for Electrochemiluminescence Aptasensing of Streptomycin

The synergistic integration of high-performance electrochemiluminescence (ECL) emitters and sensing strategies is crucial for the development of ultrasensitive detection platforms. In this study, a competitive aptasensor based on a zirconium-copper (Zr-Cu) crystal framework self-enhanced ECL emitter was constructed for the precise analysis of streptomycin (STR). The ECL performance was optimized through the synergistic interplay of bimetallic sites within the crystal framework. The ECL enhancement was attributed to a synergistic mechanism: an efficient intraunit charge transfer (IUCT) from the electron-donating Cu-ligand unit to the electron-accepting Zr-oxo cluster, coupled with the rigid framework of Zr-nodes that minimized nonradiative energy loss. Furthermore, the introduction of europium-doped cerium dioxide (CeO₂-Eu) as an enhancer, featuring multivalent reversible redox ion pairs (Ce^4+/3+-Eu^3+/2+), provided an additional amplification pathway for the ECL emission. A competitive aptasensor constructed based on the synergistic effect enabled the highly sensitive detection of STR, with a linear range of 0.001-150 nM and a limit of detection as low as 0.42 pM. This research contributed a novel strategy for designing efficient ECL materials.