Hierarchical CoZn-MOF-Supported Ag Nanocatalyst for Chemiluminescence Assay

Various supported metal catalysts have been developed to immobilize and stabilize metal species with small sizes and high dispersity. A hierarchical branch-like metal–organic frameworks (MOF) with nanosized branches and empty space between its building units facilitates the accession of substrates to metal active sites and the loading of nanoparticles, which make it an ideal carrier for developing supported metal nanocatalysts due to its high catalytic activity and load capacity. Herein, a Ag nanoparticle-loaded hierarchical CoZn-MOF (AgCZM) with enhanced peroxidase (POD)-like activity was prepared for the sensitive chemiluminescence (CL) assay. To prepare AgCZM, a pine-needle-cluster-like CoZn-MOF with POD-like activity was synthesized first via a one-pot solvothermal method. Then, the high-loaded CoZn-MOF-supported Ag nanoparticle catalyst for boosting its activity was synthesized by simply mixing CoZn-MOF and AgNO3 in polyvinylpyrrolidone (PVP) aqueous solution without using strong reducing agents, thereby enabling CoZn-MOF to retain its hierarchical structure. Further, the reactive oxygen species (ROS) generated during AgCZM-based and CoZn-MOF-based catalytic decomposition of H2O2 were verified and compared via scavenger experiments and electron paramagnetic resonance (EPR) tests, and the possible AgCZM-based luminol CL mechanism was explored. To validate the feasibility of the AgCZM-based CL assay, a CL system consisting of luminol, H2O2, and AgCZM was fabricated for dopamine (DA) detection with a negative response signal. The proposed AgCZM-based CL assay exhibited good linearities at low (5–125 nM) and high (0.625–1.75 μM) DA concentrations with detection limits of 3.91 and 73.87 nM, respectively.