Layer Growth Inhibiting Strategy for Superior-Loading Atomic Metal Sites on Ultrathin Layered Double Hydroxides as the Efficient Chemiluminescence Probes

Owing to the remarkable catalytic attributes, single-atom catalysts (SACs) have exhibited promising application prospects as the substitutes of natural enzymes. However, the low loading amount of atomic sites on typical SACs (no more than 5 wt %) significantly restricts their increased capability. Hereby, a layer growth inhibitor protocol was attempted to optimize anchoring isolated Co atoms efficiently on ultrathin monolayer layered double hydroxides (LDHs). Superior to the conventional multiple-layer LDHs, the synthesized monolayer LDHs (7.29 nm-thick) served as the emerging support for dispersing substantial active sites and featured a dramatic loading content of 32.5 wt %. Through X-ray absorption spectroscopy, the atomically dispersed active centers on Co SACs were verified as Co-N₄ moieties. The results of radical scavenger experiments and electron paramagnetic resonance spectroscopy showed that Co SACs were favorable to the high yield of reactive oxygen species originating from the decomposition of H₂O₂. Therefore, Co SACs functioned as a sensitive enhancer to drastically boost the luminol-H₂O₂ chemiluminescence intensity by ∼4713-fold, which excelled drastically over these previously reported SACs. Furthermore, Co SACs were adopted as chemiluminescent probes for the quantitation of chlorothalonil, wherein a low detection limit of 49 pg mL^-1 (3σ) was achieved. Additionally, the successful application in recovery trials demonstrated the favorable feasibility of Co SACs. The facile layer growth inhibitor protocol affords SACs with improved loading properties and even superior catalytic performances for sensitive luminescent bioassays.