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[Display omitted] Although it is well-accepted that iron oxide nanoparticles are considered as artificial enzymes when their surface is hydrophilic, the enzyme-like properties of iron oxide nanoparticles with hydrophobic surface coating is unexplored. This work demonstrates that hydrophobic iron oxide nanocrystals coated with a layer of oleic acid could serve as artificial enzymes when their surface is covered by a layer of ionic surfactant. Furthermore, the co-assembly of iron oxide nanocrystals and porous organic cages could modulate their enzyme-like activities. Co-assembly of iron oxide (Fe 3 O 4) nanocrystals with different size and porous organic cages (POCs) was performed by an emulsion-confined strategy to achieve hybridized Fe 3 O 4 /POCs co-assemblies. The peroxidase-mimic activity of these co-assemblies were assessed in the presence of 3, 3′, 5, 5′-Tetramethylbenzidine (TMB) and hydrogen peroxide. Finally, these co-assemblies were applied as sensors to detect glucose and hydrogen peroxide. Co-assembly of Fe 3 O 4 nanocrystals and POCs resulted in the self-assembly of Fe 3 O 4 nanoparticles into two-dimensional nanoparticle superlattices on the eight (1 1 1) facets of the octahedral POCs colloidal crystals. The unique oil-in-water (O/W) emulsion confined assembly method switches the Fe 3 O 4 nanoparticles and POC crystals from hydrophobic to hydrophilic because of the strong hydrophobic interactions. Importantly, these co-assemblies dispersed in water showed strong peroxidase-mimic activity in water despite that their surface is covered by a bilayer of aliphatic chains. Furthermore, the intrinsic enzymatic activity of the co-assemblies is highly dependent on the size of the nanocrystals, and a higher catalytic activity is achieved from a larger sized Fe 3 O 4 nanocrystal. [ABSTRACT FROM AUTHOR]

In peroxides-based advanced oxidation technologies (AOPs) using Fe-based catalysts, the low efficiency of Fe-ions cycling hinders their industrial applications. Recently, MoS 2 has been validated to be a promising co-catalyst that can effectively promote the dynamic cycling of Fe-ions during the reaction. However, the activities of the reported MoS 2 -loaded Fe-based catalysts still decreased significantly after 3–5 cycling reactions, so it is necessary to develop a catalyst with high activity and stability. A series of MoS 2 @Fe 3 O 4 - x (MF- x) catalysts were successfully constructed to trigger peroxymonosulfate (PMS) to eliminate the refractory organics. Ultrathin MoS 2 nanosheets (∼ 5.7 nm) were uniformly and firmly coated on the surface of Fe 3 O 4 nanoparticles via Fe–S bridging interaction. Pure MoS 2 made little contribution to the climbazole (CBZ) degradation. Compared to the Fe 3 O 4 /PMS system, the adsorption and degradation efficiencies of the CBZ by MF- x /PMS system were improved by 7.5 and 4 times, respectively. The FeII/FeIII and MoIV/MoVI redox cycles on the MF- x surface could interact and work in synergy during the catalytic activation of PMS to degrade pollutants. MF-0.23 was an effective and stable catalyst for application over a wide pH range (2.0–9.8). Moreover, it efficiently dealt with other representative refractory contaminants with different pKa values, such as fluconazole (FZ), phenol, and rhodamine B (RhB). The primary active free radicals in MF-0.23/PMS system were detected to be O 2 •– and SO 4 •–. Specifically, the generated O 2 •– not only participated in the degradation of contaminants but also contributed to the MoIV regeneration. With outstanding catalytic activity, broad applicability, excellent reusability, and long-term stability, the MoS 2 nanosheet-wrapped Fe 3 O 4 nanocrystals should be an ideal heterogeneous catalyst for PMS-based AOPs. [Display omitted] • MoS 2 nanosheet-wrapped Fe 3 O 4 nanocrystals were successfully fabricated. • MF- x showed effective and stable activity in treating refractory contaminants. • MoIV in MoS 2 can effectively promote the FeII/FeIII cycle. • O 2 •– and SO 4 •− were the predominant active oxygen species in the reaction system. • MF- x has excellent potential to be used in environmental remediation. [ABSTRACT FROM AUTHOR]

The well-dispersive and superparamagnetic Fe3O4-nanocrystals (Fe3O4-NCs) which could significantly enhance the anodic electrochemiluminescence (ECL) behavior of luminol, were synthesized in this study. Compared to ZnS, ZnSe, CdS and CdTe nanoparticles, the strongest anodic ECL signals were obtained at +1.6 V on the Fe3O4-NCs coated glassy carbon electrode. The ECL spectra revealed that the strong ECL resonance energy transfer occurred between luminol and Fe3O4-NCs. Furthermore, under the optimized ECL experimental conditions, such as the amount of Fe3O4-NCs, the concentration of luminol and the pH of supporting electrolyte, BPA exhibited a stronger distinct ECL quenching effect than its structural analogs and a highly selective and sensitive ECL sensor for the determination of bisphenol A (BPA) was developed based on the Fe3O4-NCs. A good linear relationship was found between the ECL intensity and the increased BPA concentration within 0.01–5.0 mg/L, with a correlation coefficient of 0.9972. The detection limit was 0.66 × 10−3 mg/L. Good recoveries between 96.0% and 105.0% with a relative standard deviation of less than 4.8% were obtained in real water samples. The proposed ECL sensor can be successfully employed to BPA detection in environmental aqueous samples. [ABSTRACT FROM AUTHOR]