Abstract
MoS2 quantum dots (QDs) functionalized g-C3N4 nanosheets (MoS2@CNNS) were prepared through a protonation-assisted ion exchange method, which were developed as a highly efficient biomimetic catalyst. Structural analysis revealed that uniformly-dispersed MoS2 QDs with controllable size and different loading amount grew in-situ on the surface of CNNS, forming close-contact MoS2@CNNS nanostructures and exhibiting distinct surface properties. Compared to MoS2 QDs and CNNS, the MoS2@CNNS nanocomposites exhibited a more than four times stronger peroxidase-like catalytic activity, which could catalyze the oxidation of 3,3’,5,5’-tetramethylbenzidine (TMB) in the presence of H2O2 to generate a blue oxide. Among the MoS2@CNNS nanocomposites, MoS2@CNNS(30) was verified to present the best intrinsic peroxidase-like performance, which could be attributed to the more negative potential and larger specific surface area. A simple, rapid and ultrasensitive system for colorimetric detection of H2O2 was thus successfully established based on MoS2@CNNS, displaying nice selectivity, reusability, and stability. The detection limit of H2O2 could reach as low as 0.02 μM. Furthermore, the kinetic and active species trapping experiments indicated the peroxidase-like catalytic mechanism of MoS2@CNNS. This work develops a novel, rapid, and ultrasensitive approach for visual assay of H2O2, which has a potential application prospect on clinical diagnosis and biomedical analysis.
Highlights
Over past decades, enzyme mimetics have caused extensive concern due to their favorable superiorities against harsh conditions compared to natural enzymes, such as low cost, easy preparation and storage, better stability and reusability, and nice practicability [1,2,3]
As for the MoS2@C3N4 nanosheets (CNNS) composites (Figure 1b), all the characteristic diffraction peaks can be well indexed to the graphite-like structure of CNNS (JCPDS No 87-1526) and hexagonal phase MoS2 (JCPDS Card No 37-1492), indicating that MoS2 quantum dots (QDs) were successfully formed on the surface of CNNS through the aid of ion-exchange process
With increasing the loading amount of MoS2 QDs, the relative intensity of corresponding (100) and (110) diffraction peaks of MoS2 strengthened gradually, while the characteristic peaks of MoS2 were still relatively weak and broad in the composites owing to the size effect of quantum dots
Summary
Enzyme mimetics have caused extensive concern due to their favorable superiorities against harsh conditions compared to natural enzymes, such as low cost, easy preparation and storage, better stability and reusability, and nice practicability [1,2,3]. Thereafter, many kinds of nanomaterials have been exploited as peroxidase mimetics, and have exhibited good peroxidase-like properties, such as magnetic nanomaterials (CoFe2O4 [12] and FeVO4 [13]), carbon nanomaterials (carbon nanotubes [14], carbon dots [15], graphene oxides [16], and C3N4 [17]), noble metal nanomaterials (gold, silver and platinum) [18] and their alloys (AgVO3 nanobelts [19], FeSe-Pt@SiO2 nanospheres [20], Fe3O4-Pt nanocomposites [21], and Fe3O4-Au nanohybrids [22]), and other nanomaterials (BiOI nanoflowers [23], CeVO4 nanorods [24] and MoS2 nanoflakes [25]) Despite this progress, there is still an urgent demand to pursue novel nanomaterials with highly-efficient and stable peroxidase-like activities to overcome their inherent disadvantages, including the loss of noble metals, environmental pollution, difficulty in separation, and recyclability. The MoS2 QDs were obtained by collecting the top part of the dispersion
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