Artificial self-propelled micro/nano-motors have emerged as a promising hot spot in the fields of water-body remediation and environmental protection. Herein, we report a novel multifunctional micromotors with dual enzyme-like activities for simultaneous colorimetric determination and removal of environmental contaminants. Thanks to the tubular morphology inherited from kapok fibers, these bovine serum albumin-functionalized NiCo 2 O 4 @MnO 2 /C (BSA-NiCo 2 O 4 @MnO 2 /C) micromotors with dual oxidase/peroxidase-like activity can move forward quickly in aqueous solutions via a bubble recoil mechanism, which can not only enhance the colorimetric sensing performance, but also improve the removal efficiency toward Cu 2+ ion by enhancing the mass transfer both in the detection and catalytic degradation systems. Moreover, the unique 3D hierarchical architecture assembled by core-shell NiCo 2 O 4 @MnO 2 nanosheets and C microtubes can provide more accessible reactive sites and thus dramatically facilitate such detection process. In combination with the autonomous motility, intrinsic oxidase/peroxidase-like activities and precisely tuned hierarchical architecture, these automatic micromachines not only are able to detect Cu 2+ selectively and sensitively with the limit of detection of 2.0 nM, but also quickly remove Cu 2+ from wastewater with maximal adsorption capacity of 161.8 mg g −1 . Furthermore, these micromotors exhibit excellent catalytic activity for the degradation of tetracycline hydrochloride. This multifunctional mobile platform will provide a new and promising strategy for the simultaneous detection and decontamination of poisonous metal ions and other pollutants in aqueous samples.
Bionics-inspired streptococcus-like NiCo2O4 coated needle-like MnO2 architecture has been synthesized successfully, denoted as NiCo2O4-MnO2, and the nonenzymatic electrochemical sensor based on NiCo2O4-MnO2 exhibits highly sensitive determination toward glucose. MnO2 nanowires are regarded as effective nucleation sites, which allows uniformly growing of NiCo2O4 as electrocatalytic centers on its surface by a hydrothermal method. The rational combination of streptococcus-like NiCo2O4 and needle-like MnO2 can effectively prevent the aggregation of nanomaterials due to the formation of 3D network, promote the electron transportation, and provide more electrocatalytic sites. The attractive nanostructure and composition were better confirmed by scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy, etc. The strong coupling of NiCo2O4-MnO2 inspires the synergistic effect, showing a low detection limit of 0.036 μM (S/N = 3) for glucose in 0.1 M NaOH, a high sensitivity of 2887.57 μAmM−1cm−2 and a wide response range (from 1 to 7100 μM). Moreover, the novel sensor exhibited high stability and good reproducibility. The sensor was highly selective to glucose in the presence of commonly interfering species like dopamine, uric acid, ascorbic acid, sodium chloride, fructose, galactose and mannose, and successfully applied to sensing glucose concentration in human serum samples.
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