Target-triggered dual suppression of self-enhanced ECL sensor for sensitive detection of l-Cysteine

l-Cysteine (L-Cys), one kind of aminothiol, ubiquitously exists in proteins and plays important roles in the food industry and biological processes. Herein, an electrochemiluminescence (ECL) sensor was constructed for the sensitive detection of L-Cys. As an ECL emitter, europium-porphyrin coordination polymer (Eu-PCP) was synthesized and subsequently modified with copper benzene-1,4-dicarboxylate (CuBDC) as a coreaction accelerator, which achieved high self-enhanced ECL responses. CuBDC on Eu-PCP was decomposed by the introduced L-Cys due to the coordination between Cu²⁺ and L-Cys, resulting in the decrease of ECL signal. Besides, L-Cys could consume the co-reactant of K₂S₂O₈ to reduce the production of free radical SO₄^•-, further decrease ECL signal. Thus, this L-Cys coordination-driven decomposition of coreaction accelerator and consumption of co-reactant strategy was employed to doubly suppress the ECL signal for detecting L-Cys without additional recognition and amplification elements. The constructed ECL sensor exhibited a linear range of 1.0 × 10^-10-5.0 × 10^-5 mol/L with a limit of detection of 2.0 × 10^-11 mol/L. This work has opened up new prospects for developing novel ECL sensing strategies in food safety monitoring and disease diagnosis.