Synthesis of novel chitosan/sodium hyaluronate/iridium hydrogel nanocomposite for wound healing application.

A novel chitosan/sodium hyaluronate/iridium (CHI/SH/Ir) hydrogel nanocomposite with a unique microstructure containing vertically aligned pores is fabricated via an electrophoresis technique. The formation of orderly vertical pores in CHI/SH/Ir hydrogel nanocomposite is due to the confinement of hydrogen bubbles produced from the water electrolysis during electrophoresis that limits their lateral movement and coalescence. In a wet state, the diameter for the vertical pores is 600-700 µm. With a thickness of 500 µm, the CHI/SH/Ir hydrogel nanocomposite exhibits a porosity of 76.7 % and a water uptake of 350 %. Its tensile strength is almost doubled to 8.7 MPa, as compared to that of counterpart without the addition of iridium. In CHI/SH/Ir hydrogel nanocomposite, the iridium nanoparticles are homogeneously distributed with an average size of 3 nm. The CHI/SH/Ir electrophoresis suspension exhibits a negligible cytotoxicity. In cell migration test using the human keratinocytes HaCaT cells, the CHI/SH/Ir hydrogel nanocomposite reveals a relative migration of 122.15 ± 9.02 % (p < 0.001) as compared to the blank sample. The presence of vertically aligned pores with the use of SH and iridium nanoparticles indicates a promising opportunity in wound healing application.

Facile Synthesis of Co3O4@CoO@Co Gradient Core@Shell Nanoparticles and Their Applications for Oxygen Evolution and Reduction in Alkaline Electrolytes.

We demonstrate a facile fabrication scheme for Co3O4@CoO@Co (gradient core@shell) nanoparticles on graphene and explore their electrocatalytic potentials for an oxygen evolution reaction (OER) and an oxygen reduction reaction (ORR) in alkaline electrolytes. The synthetic approach begins with the preparation of Co3O4 nanoparticles via a hydrothermal process, which is followed by a controlled hydrogen reduction treatment to render nanoparticles with radial constituents of Co3O4/CoO/Co (inside/outside). X-ray diffraction patterns confirm the formation of crystalline Co3O4 nanoparticles, and their gradual transformation to cubic CoO and fcc Co on the surface. Images from transmission electron microscope reveal a core@shell microstructure. These Co3O4@CoO@Co nanoparticles show impressive activities and durability for OER. For ORR electrocatalysis, the Co3O4@CoO@Co nanoparticles are subjected to a galvanic displacement reaction in which the surface Co atoms undergo oxidative dissolution for the reduction of Pt ions from the electrolyte to form Co3O4@Pt nanoparticles. With commercial Pt/C as a benchmark, we determine the ORR activities in sequence of Pt/C > Co3O4@Pt > Co3O4. Measurements from a rotation disk electrode at various rotation speeds indicate a 4-electron transfer path for Co3O4@Pt. In addition, the specific activity of Co3O4@Pt is more than two times greater than that of Pt/C.

Synthesis of IrO2 decorated core-shell PS@PPyNH2 microspheres for bio-interface application.

In this paper, an effective approach is demonstrated for the fabrication of IrO2-decorated polystyrene@functionalized polypyrrole (core@shell; PS@PPyNH2) microspheres. The synthesis begins with the preparation of monodispersive PS microspheres with a diameter of 490 nm, by a process of emulsifier-free emulsion polymerization, followed by a copolymerization process involving pyrrole and PyNH2 monomers in a PS microsphere aqueous suspension, to produce uniform PS@PPyNH2 microspheres with a diameter of 536 nm. The loading of 2 nm IrO2 nanoparticles onto the PS@PPyNH2 microspheres can be easily adjusted by tuning the pH value of the IrO2 colloidal solution and the PS@PPyNH2 suspension. At pH 4, we successfully obtain IrO2-decorated PS@PPyNH2 microspheres via electrostatic attraction and hydrogen bonding simultaneously between the negatively-charged IrO2 nanoparticles and the positively-charged PS@PPyNH2 microspheres. These IrO2-decorated PS@PPyNH2 microspheres exhibit a characteristic cyclic voltammetric profile, similar to that of an IrO2 thin film. The charge storage capacity is 5.19 mA cm-2, a value almost five times greater than that of PS@PPyNH2 microspheres. In addition, these IrO2-decorated PS@PPyNH2 microspheres exhibit excellent cell viability and biocompatibility.