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The robust and strong electrochemiluminescence (ECL) emission of organic emitters in an aqueous solution is crucial for expanding their applications in early diagnosis. Herein, a Zn porphyrin-based metal–organic framework ((Zn)porphMOF) was facilely obtained by chelating Zn(II)meso-tetra (4-sulfonatophenyl) porphine (Zn-TSPP) with Zn ions, showing substantially enhanced ECL radiation with K2S2O8 as the coreactant via the "reduction-oxidation" route in aqueous media. In contrast with Zn-TSPP, (Zn)porphMOF displayed 22-fold increase in the ECL intensity because of the agglomeration effect. By virtue of the dramatic confinement towards the energy and electron transfer of ascorbic acid (AA) during the ECL process, an ultrasensitive biosensor was developed with a wide linear range (3.77 to 26.4 μM) and ultra-low detection limit of 0.29 μM at 3 times of the signal-to-noise ratio (3S/N). This work offers a feasible avenue to harvest the steady and boosted ECL responses of organic molecules in aqueous media, also greatly expanding the MOF applications in bioanalysis. [ABSTRACT FROM AUTHOR]

• ZnPPIX-Pd NCs work as an ECL emitter with high ECL intensity and lower excitation potential. • The ECL was irradiated from single oxygen via electrocatalytic reduction of ZnPPIX-Pd NCs. • A fast and ultrasensitive ECL sensor was constructed for Zn2+ detection based on "signal on" mode. Zinc ions (Zn2+) act as a transcription factor in eukaryotic cells for mediating protein-protein interactions in human healthy. The simple and sensitive detection of Zn2+ is the crucial mission in analytical field. This work demonstrated a novel and fast Zn2+ detection strategy based on "signal on" mode with electrochemiluminescence (ECL) luminophore, in which singlet oxygen was generated via electrocatalytic reduction of zinc proto-porphyrin IX grafted onto Pd nanocubes (ZnPPIX-Pd NCs). In protocol, Pd NCs were synthetized under hydrothermal conditions and aminated through thermal oxidative polymerization of 3-aminopropyltriethoxysilane (APTES), followed by further linking with PPIX via amide reaction. The resulting PPIX-Pd NCs effectively captured Zn2+ in chelation and monitored by Fourier transform infrared (FTIR) spectroscopy and ultraviolet-visible (UV-vis) absorption spectroscopy. By virtue of the metal resonance responses of Pd NCs, an intense monochromic, potential shuffling and enhanced ECL irradiation shows up for the hybrid nanocomposite with H 2 O 2 as the coreactant. To this end, an ultrasensitive method based on the nanocomposite with a "signal-on" model was developed for Zn2+ detection with a low detection limit down to 0.38 nM (based on a S / N = 3), excellent precision and high stability. The ECL strategy reveals the potential application in molecular diagnosis and offers a new avenue for bioassay of structural Zn(II) proteins and zinc finger-binding nucleotides. [ABSTRACT FROM AUTHOR]