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Constructing hollow mesoporous nanostructures for dispersing catalytically active sites has attracted growing interest. Here, for the first time, Co 3 O 4 hollow nanocages (Co 3 O 4 HNCs) derived from ZIF-67 were prepared for loading iron nanoparticles (FeNPs), resulting in FeNPs@Co 3 O 4 hollow nanocages (FeNPs@Co 3 O 4 HNCs). FeNPs@Co 3 O 4 HNCs were characterized by SEM, TEM, XRD, XPS and FT-IR. The FeNPs@Co 3 O 4 HNCs composites could catalyze the oxidation of TMB into blue product by H 2 O 2 , showing better peroxidase-like activity than FeNPs and Co 3 O 4 HNCs. Notably, kinetic studies indicated that FeNPs@Co 3 O 4 HNCs behaved an excellent affinity to H 2 O 2 with K m value of 0.019 mM, which was 195 times lower than that of HRP. On this basis, a facile colorimetric biosensing method was established to detect glucose. The linear range was 0.5–30 μM, and the limit of detection was 0.05 μM. The proposed sensor was successfully used to determine glucose in human serum samples. The highly catalytic performance of FeNPs@Co 3 O 4 HNCs is attributed to its porous hollow structure, which is beneficial for dispersion of in situ formed FeNPs and for reducing the agglomeration. Further, the FeNPs@Co 3 O 4 HNCs catalysts with porous character provide an essential way to expose active sites as far as possible to the substrate and increase the catalytic active sites. [ABSTRACT FROM AUTHOR]

Encapsulating metal nanoparticles (NPs) into carbon materials is a promising strategy for the fabrication of nanozymes with high activity. Here, for the first time, the proof-of-concept is demonstrated by fabricating CoNPs embedded in NH 2 -MIL-88(Fe) MOFs-derived magnetic carbon (MC) through in situ reduction of cobalt precursors by NaBH 4 . The obtained CoNPs/MC was characterized by TEM, SEM, XPS, XRD, Raman spectrum, and FT-IR. The CoNPs/MC exhibits much higher peroxidase-like activity than pure CoNPs and magnetic carbon. The high peroxidase-like activity of the CoNPs/MC is attributed to the decomposition of H 2 O 2 to generate OH and O 2 − radicals, resulting in TMB color reaction. Also, CoNPs/MC is robust in a wide range of pH and temperature, indicating a promising peroxidase-like candidate. On this basis, a colorimetric assay was developed by combining glucose oxidase with CoNPs/MC for glucose biosensing. The linear range for glucose detection is from 0.25 to 30 μM with a lower detection limit of 156 nM. The CoNPs/MC-based colorimetric method has been successfully used to assay the content of glucose in real biological samples such as human serums. Our work reveals the high potential of encapsulating metal NPs into carbon materials for the fabrication of nanozymes with stable and high activity. [ABSTRACT FROM AUTHOR]

MoS 2 -MIL-101(Fe) was prepared and investigated for colorimetric analysis of H 2 O 2 and glucose with high selectivity based on a superior peroxidase-like activity. • MoS 2 -MIL-101(Fe) was developed and explored as nanozyme for the first time. • Synergistic interaction in MoS 2 -MIL-101(Fe) leads to superior catalytic activity. • Strong affinity of MoS 2 -MIL-101(Fe) for H 2 O 2 due to the low K m of 0.008 mM. • MoS 2 -MIL-101(Fe) could be used for highly sensitive H 2 O 2 and glucose detection. A novel nanostructure MoS 2 nanoflowers anchoring iron(III)-based metal-organic framework MIL-101(Fe) [Fe 3 O(H 2 O) 2 Cl(O 2 C–C 6 H 4 −CO 2) 3 ], named MoS 2 -MIL-101(Fe), was prepared by growing MIL-101(Fe) crystals with as-prepared MoS 2. Then, MoS 2 -MIL-101(Fe) was characterized through SEM, TEM, BET, XRD, DLS, and XPS. MoS 2 -MIL-101(Fe) possesses synergetic peroxidase-mimicking activity over individual MIL-101(Fe) and MoS 2 , which can catalyze the oxidation of TMB by H 2 O 2 with a much stronger Vis-absorption. MIL-101(Fe) has a high porosity and large specific surface area for MoS 2 to absorb H 2 O 2 and TMB. Hydrophilic MIL-101(Fe) could prevent the aggregation of hydrophobic MoS 2 in aqueous solution, which is beneficial for catalysis. In addition, anchored MoS 2 brings mesopore and abundant exposed active units to the MIL-101(Fe) surface. The synergetic effects result in a highly enhanced catalytic performance. The Michaelis constant (0.008 mmol/L) of MoS 2 -MIL-101(Fe) for H 2 O 2 is 462 times lower than that of HRP, showing its strong affinity with H 2 O 2. On the basis, a sensitive method for H 2 O 2 detection was proposed with a linear range of 0.01−20 μmol/L and a detection limit of 10 nmol/L. Considering H 2 O 2 as product in the reaction of glucose catalyzed by glucose oxidase, a sensitive and selective method for glucose detection was proposed. The method can be used in blood glucose detection with good accuracy. [ABSTRACT FROM AUTHOR]