A dual-mode electrochemical and electrochemiluminescent sensor based on hydrogen-bonded organic frameworks for highly sensitive detection of mercury and zinc ions

In this study, we constructed a dual-mode electrochemical-electrochemiluminescent (EC-ECL) sensor based on a hydrogen-bonded organic framework (RuHOFs) with Ru(dcbpy)₃²⁺) as the primary emitter and [2,2′-bipyridine]-5,5′-diamine (DAP) as the secondary ligand. This sensor enables efficient and sensitive detection of heavy metal ions (HMIs), mercury ions (Hg²⁺) and zinc ions (Zn²⁺). RuHOFs possess a high specific surface area and a stable hydrogen-bond network, offering ideal N,N′-bipyridine chelating sites for effective recognition of metal ions, significantly enhancing the stability of both EC and ECL signals. The results showed that the sensor produced only a rising ECL signal with a limit of detection (LOD) of 13 pM (1 μM∼10 pM) after interacting with Zn²⁺, and upon binding with Hg²⁺, a declining ECL signal and an amplification of the DPV signal were detected, the LOD of its ECL and EC reached 0.55 pM (0.1 μM∼1 pM) and 0.26 nM (1 μM∼5 nM), respectively. Moreover, by growing RuHOFs on the surface of carbon fibers, a RuHOFs-modified carbon fiber microelectrode (CFM) electrochemical sensor was prepared, achieving a significant enhancement in sensitivity for Hg²⁺ detection, with an LOD of 0.09 nM (0.05 μM ∼ 0.1 nM), and meanwhile, the sensor was effectively utilized for the electrochemical detection of Hg²⁺ in rat blood. The synthesis of RuHOFs presents new potential for the construction of EC-ECL sensing platforms, and new research ideas and prospective applications in the areas of environmental monitoring and biosensing.