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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 solvent assisted room temperature one pot in situ multiple oxidation reduction reaction between nitropeptide solution in ammonium hydroxide and FeCl2 leads to the formation of Fe3O4 nanocrystals stabilized by the resultant dipeptide. The Pd embedded dipeptide stabilized supramolecular nanocrystals exhibit excellent catalytic activity, magnetic recovery and reusability up to three cycles for Suzuki-Miyaura cross-coupling reaction without significant loss of catalytic performance in aqueous media. [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.

• A novel MIP-Fe 3 O 4 -NCs with specific recognition sites to BPA was fabricated. • The MIP-Fe 3 O 4 -NCs/GCE could promote the cathodic ECL of luminol and specifically rebind BPA. • The ECL quenching property of MIP-Fe 3 O 4 -NCs was the electron transfer hindrance after BPA adding. • The MIECL sensor for BPA determination in seawater and fish samples were developed. A highly selective molecularly imprinted electrochemiluminescence (MIECL) sensor based on molecularly imprinted Fe 3 O 4 nanocrystals (MIP-Fe 3 O 4 /NCs) and luminol was developed for bisphenol A (BPA) determination. MIP-Fe 3 O 4 -NCs were synthesized and immobilized on the glassy carbon electrode (GCE) surface to fabricate the electrogenerated chemiluminescence (ECL) system. The GCE modified with MIP-Fe 3 O 4 -NCs could greatly promote the cathodic ECL of luminol. After incubation with the BPA solution, the imprinting sites on the surface of MIP-Fe 3 O 4 -NCs could specifically rebind BPA, resulting in selective and sensitive ECL quenching by hindering electron transfer capability. Under optimal conditions, the relative ECL intensities were proportional to the logarithm of BPA concentration ranging from 0.002 μg/L to 5.0 × 103 μg/L at a limit of detection of 2.0 × 10−4 μg/L. Satisfactory recoveries of 93.5 %–98.3 % were obtained in fish and seawater samples at a relative standard deviation of <6.1 %. The proposed MIECL sensor displayed good selectivity, high sensitivity, and excellent accuracy and precision. The results demonstrated the potential application of the MIECL sensor for BPA analysis in actual samples and for pollutant analysis. [ABSTRACT FROM AUTHOR]

• Nonviral gene vector with folate/magnetism targeting based on hyperbranched polymer. • FA-PEG-HPEI as nanoreactors to prepare superparamagnetic Fe 3 O 4 nanocrystals. • Fe 3 O 4 /FA-PEG-HPEI have higher luciferase expression level than HPEI. A new strategy for in situ preparation of non-viral gene vectors with folate/magnetism dual targeting based on hyperbranched polymers has been described. Folate-PEG-grafted-hyperbranched poly(ethylenimine)s (FA-PEG-HPEI) were synthesized and used as nanoreactors to prepare monodisperse Fe 3 O 4 nanocrystals (NCs). The FA-PEG-HPEI had FA targeting groups, low cytotoxicity and ideal gene transfection performance, while Fe 3 O 4 NCs had superparamagnetic property, thus the resulting Fe 3 O 4 /FA-PEG-HPEI nanocomposites integrated the properties of FA-PEG-HPEI and Fe 3 O 4 NCs together. As expected, the Fe 3 O 4 /FA-PEG-HPEI nanocomposites as non-viral gene vectors with folate/magnetism dual targeting had improved luciferase expression level in HEK 293T and Hela cells under a magnetic gradient field. The luciferase expression level mediated by Fe 3 O 4 /FA-PEG-HPEI nanocomposites in HEK 293T and Hela cells under a magnetic gradient field were 21 and 29 fold of that of standard HPEI transfection, respectively. [ABSTRACT FROM AUTHOR]

• The Fe 3 O 4 nanocrystals are well-distributed between Ti 3 C 2 interlayers. • The 2D confinement effects stabilize the hybrids with high exposure of active sites. • The Fe 3 O 4 @Ti 3 C 2 hybrids possess a rapid and stable charge/discharge capability. Balancing energy density and charging rate has been identified as a great challenge for Li-ion batteries (LIBs), which mainly hinges on developing high-performance electrode materials. Herein, we have developed novel Fe 3 O 4 @Ti 3 C 2 hybrids, in which the Fe 3 O 4 nanocrystals are well-anchored between Ti 3 C 2 interlayers with the assistance of the synergistic effects of 2D physical confinement and Ti O Fe covalent bonds. Such structural design can address the dispersion and volume change of nanocrystals during continuous charge/discharge with the enhancement of structural stability and the exposure of abundant active sites for each component. Meantime, the charge polarization caused by the Ti O Fe covalent bonds greatly accelerates the lithiation reaction kinetics and electrons transfer. These advantages endow the Fe 3 O 4 @Ti 3 C 2 hybrids with a very high specific capacity of 1172 mAh g−1 and a rapid charging capability of 366 mAh g−1 in 66 s. A 90% capacity retention can be maintained even through 1000 cycles at 5 A g−1. More impressively, we can also achieve a free-standing electrode by a simple vacuum filtering, exhibiting a high areal capacity of 4.2 mAh cm−2 at 4.4 mg cm−2 almost without sacrificing gravimetric capacity. The present 2D confined strategy provides a new notion to construct satisfactory electrodes for energy storage. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR)-based nanomaterials that provide efficient tumor ablation for cancer therapy have been reported. However, the issues of biocompatibility of metals or ions in inorganic nanoparticles systems such as copper and gold nanoparticles are still a matter of concern. In this study, we developed a facile and ligand-assisted co-precipitation method to synthesize biocompatible iron oxide (IO) nanocrystals with NIR absorption that provided T2-weighted magnetic resonance (MR) images and photothermal ablation characteristics suitable for cancer theranostics. Our results showed that 150-nm particles can be synthesized and optimized by using different amounts of ligand. NIR-IO nanocrystals of this size showed high photothermal conversion efficiency (21.2%) and T2-weighted MR contrast (transverse relaxivity value approximately 141 S-1 mM-1). The NIR-IO nanocrystals showed no cytotoxicity in HT-29 colorectal cancer cells without irradiation, whereas the viability of cells that received NIR-IO nanocrystals decreased significantly after 808-nm laser irradiation. The mechanism of cell death may involve alterations in protein secondary structure and membrane permeability. For in vivo studies, 4-fold enhanced tumor accumulation was significantly observed of NIR-IO nanocrystals with a magnetic field (MF) application, resulting in a 3-fold higher T2-weighted MR signal than that produced by a commercial T2-weighted MR contrast agent (Resovist®) and excellent photothermal efficacy (approximately 53 °C) for cancer treatment. The innovative NIR-IO nanocrystals showed excellent biocompatibility and have great potential as a theranostic agent against cancer., Competing Interests: Competing Interests: The authors have declared that no competing interest exists.

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]

A protease-activated ratiometric fluorescent probe based on fluorescence resonance energy transfer between a pH-sensitive fluorescent dye and biocompatible Fe3O4 nanocrystals was constructed. A peptide substrate of MMP-9 served as a linker between the particle quencher and the chromophore that was covalently attached to the antitumor antibody. The optical response of the probe to activated MMP-9 and gastric cell line SGC7901 tumor cells was investigated, followed by in vivo tumor imaging. Based on the ratiometric pH response to the tumor microenvironment, the resulting probe was successfully used to image the pH of subcutaneous tumor xenografts.