Fe 3 O 4 microsphere is a good candidate as support for catalyst because of its unique magnetic property and large surface area. Coating Fe 3 O 4 microspheres with other materials can protect them from being dissolved in acid solution or add functional groups on their surface to adsorb catalyst. In this paper, a carbon layer was coated onto Fe 3 O 4 microspheres by hydrothermal treatment using polyethylene glycol as the connecting agents between glucose and Fe 3 O 4 spheres. Through tuning the added amounts of reactants, the thickness of the carbon layer could be well-controlled. Because of the abundant reductive groups on the surface of carbon layer, noble metal ions could be easily adsorbed and in situ reduced to nanoparticles (6-12 nm). The prepared catalyst not only had unique antiacid and magnetic properties, but also exhibited a higher catalytic activity toward the reduction of methyl orange than commercially used Pd/C catalyst.

The design and fabrication of a robust nanoporous membrane in large scale is still a challenge and is of fundamental importance for practical applications. Here, a robust three/two-dimensional polymer/graphene oxide heterogeneous nanoporous membrane is constructed in large scale via the self-assembly approach by chemically designing a robust charge-density-tunable nanoporous ionomer with uniform pore size. To obtain a nanoporous polymer that maintains high mechanical strength and promotes multifunctionality, we designed a series of amphiphilic copolymers by introducing a positively charged pyridine moiety into the engineered polymer polyphenylsulfone. The multiphysical-chemical properties of the membrane enable it to work as a nanogate switch with synergy between wettability and surface charge change in response to pH. Then we systematically studied the transmembrane ionic transport properties of this two-/three-dimensional porous system. By adjusting the charge density of the copolymer via chemical copolymerization through a controlled design route, the rectifying ratio of this asymmetric membrane could be amplified 4 times. Furthermore, we equipped a concentration-gradient-driven energy harvesting device with this charge-density-tunable nanoporous membrane, and a maximum power of ≈0.76 W m was obtained. We expect this methodology for construction of a charge-density-tunable heterogeneous membrane by chemical design will shed light on the material design, and this membrane may further be used in energy devices, biosensors, and smart gating nanofluidic devices.

Heterogeneous membranes composed of asymmetric structures or compositions have enormous potential in sensors, molecular sieves, and energy devices due to their unique ion transport properties such as ionic current rectification and ion selectivity. So far, heterogeneous membranes with 1D nanopores have been extensively studied. However, asymmetric structures with 3D micro-/nanoscale pore networks have never been investigated. Here, a simple and versatile approach to low-costly fabricate hydrogel/conducting polymer asymmetric heterogeneous membranes with electro-/pH-responsive 3D micro-/nanoscale ion channels is introduced. Due to the asymmetric heterojunctions between positively charged nanoporous polypyrrole (PPy) and negatively charged microscale porous hydrogel poly (acrylamide-co-acrylic acid) (P(AAm-co-AA)), the membrane can rectify ion transmembrane transport in response to both electro- and pH-stimuli. Numerical simulations based on coupled Poisson and Nernst-Plank equations are carried out to explain the ionic rectification mechanisms for the membranes. The membranes are not dependent on elaborately fabricated 1D ion channel substrates and hence can be facilely prepared in a low-cost and large-area way. The hybridization of hydrogel and conducting polymer offers a novel strategy for constructing low-cost, large-area and multifunctional membranes, expanding the tunable ionic rectification properties into macroscopic membranes with micro-/nanoscale pores, which would stimulate practical applications of the membranes.

CuS-graphene nanosheet (GNS) composites with well-defined morphology have been successfully fabricated via a simple one-pot hydrothermal route by using thioacetamide (TAA) as both the sulfur source and reducing agent. The as-prepared CuS-GNS composites with an appropriate content of graphene exhibited an even higher peroxidase-like catalytic activity than pristine CuS nanoparticles in acetate buffer solution (pH = 4.0), which provided a facile method for the colorimetric detection of hydrogen peroxide (H2O2). It was calculated that H2O2 could be detected as low as 1.2 μM (S/N = 3) with a wide linear range from 2.0 to 20.0 μM (R(2) = 0.992), indicating that the as-prepared catalyst as an artificial peroxidase is promising for application in biosensors and environmental monitoring.

With an accurate control of the dispersity and size of the palladium nanoparticles (Pd NPs), carbon spheres/Pd NPs composite was prepared without any extra reducing agents. In order to fully understand the formation mechanism and find out the best condition for the fabrication of carbon/Pd composite spheres, the effects of temperature, reaction time, pH value, and the weight ratio of PdCl(2) to carbon spheres on the morphology of the final products were investigated. A superior product with small (d = 7.66 nm, sigma = 1.94 nm), homogeneously distributed Pd crystals was obtained at pH 7 and a reaction temperature of 70 degrees C in ethanol. The Pd NPs decorated carbon sphere was used as support for electroactive polyaniline (PANI) in our work because it could enhance their sensing properties which were afforded by catalytic Pd NPs and hydrophilic carbon spheres. The sensor based on carbon/Pd/PANI exhibited a high sensitivity of 656.0693 mA M(-1) cm(-2) and a detection limit of 5.48 microM toward the reduction of H(2)O(2). In addition, the carbon/Pd/PANI sensor also showed good selectivity between H(2)O(2) and ascorbic acid.

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