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We report a facile fabrication of a host-metal-guest coordination-bonding system in a mesostructured Fe3O4/chitosan nanoparticle that can act as a pH-responsive drug-delivery system. The mesostructured Fe3O4/chitosan was synthesized by a solvothermal approach with iron(III) chloride hexahydrate as a precursor, ethylene glycol as a reducing agent, ammonium acetate as a porogen, and chitosan as a surface-modification agent. Subsequently, doxorubicin (DOX), acting as a model drug (guest), was loaded onto the mesostructured Fe3O4/chitosan nanoparticles, with chitosan acting as a host molecule to form the NH2-Zn(II)-DOX coordination architecture. The release of DOX can be achieved through the cleavage of coordination bonds that are sensitive to variations in external pH under weakly acidic conditions. The pH-responsive nature of the nanoparticles was confirmed by in vitro releases and cell assay tests. Furthermore, the relaxation efficiency of the nanoparticles as high-performance magnetic resonance imaging contrast agents was also investigated. Experimental results confirm that the synthesized mesostructured Fe3O4/chitosan is a smart nanovehicle for drug delivery owing to both its pH-responsive nature and relaxation efficiency., (Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The design of low-cost, short time, mass preparation and high-efficiency of electrocatalysts for hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and zinc air batteries are highly challenging. Herein, we design a bifunctional chrysanthemum-like electrocatalysts (Cu(OH) 2 @CoMoO 4 ·0.9H 2 O/CF) for highly efficient electrochemical water splitting by a simple and highly controllable two-step method in a few hours. This unique hierarchical electrocatalyst has porous structure and short diffusion paths, which can promote charge transfer, ion and water diffusion, and rapidly release hydrogen and oxygen bubbles. The obtained Cu(OH) 2 @CoMoO 4 ·0.9H 2 O/CF composite exhibits low overpotentials of 57 mV at −10 mA cm−2 toward the HER, which is superior to most of the previously reported CoMoO 4 -based electrocatalysts. And the Cu(OH) 2 @CoMoO 4 ·0.9H 2 O/CF exhibits excellent performance of 355 mV at 100 mA cm−2 toward the OER. Benefiting from the unique hierarchical heterostructure and the coupling effect between the inner and outer layers, the Cu(OH) 2 @CoMoO 4 ·0.9H 2 O/CF catalysts were endowed with high activity for water splitting. [Display omitted] [ABSTRACT FROM AUTHOR]

Fe 3 O 4 @CeO 2 yolk–shell nanocomposites (NCs) were synthesized by growing CeO 2 onto Fe 3 O 4 hollow nanoparticles (NPs) as an artificial peroxidase for the purpose of elevated activity. The resultant NCs exhibited strong magnetic response with narrow size distribution and high surface area. Owing to the individual peroxidase-like catalytic activity of CeO 2 onto Fe 3 O 4 nanoparticles (NPs), Fe 3 O 4 @CeO 2 NCs was investigated to achieve synergistic catalytic activity. As a result, the as-prepared Fe 3 O 4 @CeO 2 NCs exhibited impressive peroxidase-like catalysis activity for 3, 3′, 5, 5′-tetramethylbenzidine (TMB). Moreover, comparing with natural enzymes, hollow Fe 3 O 4 NPs and CeO 2 NPs, the Fe 3 O 4 @CeO 2 NCs displayed a lower Michaelis constant ( K m ) value or stronger affinity to H 2 O 2 and TMB. A limit of detection of 8.5 µmol/L for H 2 O 2 and 21 µmol/L for glucose was attained with acceptable stability and reproducibility. The activation mechanism was also studies using competitive radical tests and Electron spin resonance (ESR) analysis. [ABSTRACT FROM AUTHOR]

We report a facile fabrication of a host-metal-guest coordination-bonding system in a mesostructured Fe3O4/chitosan nanoparticle that can act as a pH-responsive drug-delivery system. The mesostructured Fe3O4/chitosan was synthesized by a solvothermal approach with iron(III) chloride hexahydrate as a precursor, ethylene glycol as a reducing agent, ammonium acetate as a porogen, and chitosan as a surface-modification agent. Subsequently, doxorubicin (DOX), acting as a model drug (guest), was loaded onto the mesostructured Fe3O4/chitosan nanoparticles, with chitosan acting as a host molecule to form the NH2ZnIIDOX coordination architecture. The release of DOX can be achieved through the cleavage of coordination bonds that are sensitive to variations in external pH under weakly acidic conditions. The pH-responsive nature of the nanoparticles was confirmed by in vitro releases and cell assay tests. Furthermore, the relaxation efficiency of the nanoparticles as high-performance magnetic resonance imaging contrast agents was also investigated. Experimental results confirm that the synthesized mesostructured Fe3O4/chitosan is a smart nanovehicle for drug delivery owing to both its pH-responsive nature and relaxation efficiency. [ABSTRACT FROM AUTHOR]

A simple preparation process for the monodispersed pH-sensitive core-shell magnetic microspheres was carried out consisting of chitosan self-assembled on magnetic iron oxide nanoparticles. Meanwhile, glucoamylase was immobilized as a model enzyme on this carrier of FeO/CS microspheres by ionic adsorption. The morphology, inner structure, and high magnetic sensitivity of the resulting magnetic chitosan microspheres were studied, respectively, with a field emission scanning electron microscope (SEM), transmission electron microscope (TEM), FT-IR spectroscopy, thermogravimetric analysis (TGA), and a vibrating sample magnetometer (VSM). Subsequently, the properties of glucoamylase immobilized on the regenerated supports were also investigated by determining storage stability, pH stability, reusability, magnetic response, and regeneration of supports. The results from characterization and determination remarkably indicated that the immobilized glucoamylase obtained presents excellent storage stability, pH stability, reusability, magnetic response, and regeneration of supports. Therefore, this kind of magnetic FeO/CS microspheres with perfect monodispersity should be an ideal support for enzyme immobilization. [ABSTRACT FROM AUTHOR]

Designing ultrahigh energy density and mass-loading of electrocatalysts for hydrogen evolution is highly desirable but remains a great challenge. Herein, a 3D high-rise architectural structure consisting of dense Ni(OH) 2 nanoparticles on CuMoO 4 nanocube heterostructure arrays on Ni foam (Ni(OH) 2 /CuMoO 4 /NF) is developed via a hydrothermal reaction, calcination and electrodeposition method. Benefitting from the optimized electronic configuration, hierarchical high-rise architecture, and large specific surface area and mesoporous, the Ni(OH) 2 /CuMoO 4 /NF exhibits superior hydrogen evolution reaction (HER) activity in 1.0 M KOH solution. Ni(OH) 2 /CuMoO 4 /NF only requires low overpotential of 70 mV achieving a current density of 10 mA cm−2 with a low Tafel slope of 80 mV dec−1, and superior long-term stability toward HER. This work provides a new structural design to high-rise architectural structures for efficient catalytic application. [Display omitted] • A highly topological nickel hydroxide doped copper molybdate oxide composite was synthesized. • The high-topology structure with a heterogeneous interface enhances the conductivity. • The typical structure and proper components contribute to the electrochemical activity. [ABSTRACT FROM AUTHOR]

Developing earth-abundant, low-cost, high-efficiency electrocatalysts for hydrogen evolution reaction (HER) by structure design is still a grand challenge. Herein, we fabricated Ni nanoparticles encapsulated by carbon loaded in two-dimensional carbon nanosheets (2D Ni@C@SU) using a molten salt (NaCl)-assisted pyrolysis method. Because of the large specific surface area (262.35 m²/g) and high electrical conductivity, the prepared 2D Ni@C@SU-0.75 electrocatalyst exhibits excellent HER electrocatalytic activity with the overpotential of −105 mV at −10 mA cm−2 and −367 mV at −200 mA cm−2, which is close to the commercial benchmark Pt/C (η 200 = −339 mV). Besides, the catalyst displays incredible durability in the electrocatalytic HER. This research indicates that the green solid-state synthetic strategy provides a new window for designing new Ni-based composite catalysts for electrocatalytic HER. [Display omitted] • Catalysts were prepared by a facile one-step synthesis. • The synthesis process is green and solvent-free. • Ni@C@SU-0.75 catalyzes hydrogen evolution reaction with -105 mV at 10 mA/cm2, and exhibited a good stability. • The 2D nanosheets encapsulated structure can increase the active sites and promote proton/electron transport. [ABSTRACT FROM AUTHOR]