Co single‐atom catalysts (SACs) with good aqueous solubility and abundant labelling functional groups were prepared in Co/Fe bimetallic metal‐organic frameworks by a facile solvothermal method without high‐temperature calcination. In contrast to traditional chemiluminescence (CL) catalysts, Co SACs accelerated decomposition of H2O2 to produce a large amount of singlet oxygen (1O2) rather than superoxide (O2.−) and hydroxyl radical (OH.). They were found to dramatically enhance the CL emission of the luminol‐H2O2 reaction by 1349 times, and, therefore, were employed as very sensitive signal probes for conducting CL immunoassay of cardiac troponin I. The detection limit of the target analyte was as low as 3.3 pg mL−1. It is the first time that employment of SACs for boosting CL reactions has been validated. The Co SACs can also be employed to trace other biorecognition events with high sensitivity.

Superior to traditional nanoscale catalysts, single-atom site catalysts (SASCs) show such merits as maximal catalysis efficiency and outstanding catalytic activity for the construction of analytical methodological platforms. Hereby, an in situ etching strategy was designed to prepare yolk-shell Co SASCs derived from ZIF-8@SiO2 nanoparticles. On the basis of direct chemical interactions between precursors and supports, the Co element with isolated atomic dispersion was anchored on ZIF-8@SiO2 nanoparticles. The Co SASCs possess high Fenton-like activity and thus can catalyze the decomposition of H2O2 to produce massive superoxide radical anions instead of singlet oxygen and hydroxyl radicals. With the activity for producing superoxide radical anion, Co SASCs can greatly improve the chemiluminescent (CL) response of a luminol system by 3133.7 times. Furthermore, the SASCs with active sites of Co–O5 moieties were utilized as the CL probes for establishment of an immunoassay method for sensitive detection of mycotoxins by adopting aflatoxin B1 as a mode analyte. The quantitation range is 10–1000 pg/mL, and the limit of detection is 0.44 pg/mL (3σ) for aflatoxin B1. The proof-of-principle work elucidates the practicability of direct chemical interactions between precursors and supports for forming SASCs with ultrahigh CL response, which can be extended to the exploitation of more sorts of SASCs for tracing biological binding events.

Nanosized metal–organic frameworks (MOFs) NH2-MIL-53­(Al) were synthesized from 2-aminoterephthalic acid (NH2·H2BDC) and AlCl3 by a facile hydrothermal method. The synthesized MOFs displayed good stability and a uniform particle size in a netural medium and were hydrolyzed in alkaline medium to release a large amount of fluorescent ligand NH2·H2BDC. Therefore, they can act as large-capability nanovehicles to load signal molecules for investigating various biorecognition events. In this work, based on the alkaline hydrolysis behavior of MOFs NH2-MIL-53­(Al), a sensitive immunoassay method was developed for the detection of aflatoxin B1 (AFB1) by employing them as fluorescent signal probes. With a competitive immunoassay mode on microplate, AFB1 can be detected within a linear range of 0.05–25 ng mL–1. The method was successfully employed to detect AFB1 spiked in Job tears, Polygala tenuifolia and with acceptable recovery values of 83.00–114.00%. The detection results for moldy Fructus xanthii displayed an acceptable agreement with those from the high-performance liquid chromatography method, with relative errors of −14.21 to 3.49%. With the merits of high sensitivity, facile manipulation, and ideal reliability, the approach can also be extended to other areas such as aptasensor and receptor-binding assay.

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A facile, one-step doping protocol was adopted to synthesize Co single atomic site catalysts (SASCs) in UiO-66 metal–organic frameworks. In view of highly uniform active sites of Co–O6 moieties, the SASCs specifically contribute to catalyzing the generation of a large amount of singlet oxygen instead of superoxide or hydroxyl radicals, which endows Co SASCs with a the remarkable enhancement effect (∼3775 times) on luminol chemiluminescent (CL) emission. Interestingly, monolayer titanium carbide MXenes can drastically quench the CL signal of the Co SASC-boosted luminol reaction by ∼94.6% as highly efficient luminescent absorbents. Furthermore, the emitter–quencher pair of Co SASCs and titanium carbide MXenes was successfully adopted to develop an immunoassay method for cardiac troponin I (cTnI) on an immunochromatographic test strip platform. With a sandwich immunoreaction mode, a titanium carbide MXene-labeled cTnI tracer antibody was captured on the test line of a test strip, which significantly inhibited the CL response of the Co SACs-boosted luminol system. The dynamic range for quantitating cTnI is 1.0–100 pg mL–1, with a detection limit of 0.33 pg mL–1 (3σ). The test strip was successfully used to detect cTnI in human serum samples collected from cardiopathy patients. This proof-of-principle work manifests both the CL enhancement of SASCs and the quenching behavior of MXenes, which shows the thrilling prospects of combinational usage of the two functionalized nanomaterials for tracking biological recognition events.