Yanqiu Zhu

Efficient route to large arrays of CNx nanofibers by pyrolysis of ferrocene/melamine mixtures

We report a high-yield route to two-dimensional arrays (<400×400 μm2) of aligned C49Nx (x ⩽ 1) nanofibers (<100 nm o.d.; <60 μm length), by pyrolyzing mixtures of ferrocene and melamine at 950–1050 °C under an Ar flow. The fibers exhibit unusual interlinked stacked-cone morphologies, ascribed to the presence of nitrogen. High-resolution electron energy-loss spectroscopy of the individual fibers reveals a 2% nitrogen content with ionization energies mainly at ∼400.9 eV, corresponding to N bonded to three C atoms within a hexagonal framework. The nanofibers may be useful for the economic fabrication of field emission sources and robust composites.

Zeolitic imidazolate framework materials: recent progress in synthesis and applications

Zeolitic imidazolate frameworks (ZIFs) represent a new and special class of metal organic frameworks comprised of imidazolate linkers and metal ions, with structures similar to conventional aluminosilicate zeolites. Their intrinsic porous characteristics, abundant functionalities as well as exceptional thermal and chemical stabilities have led to a wide range of potential applications for various ZIF materials. Explosive research activities ranging from synthesis approaches to attractive applications of ZIFs have emerged in this rapidly developing field in the past 5 years. In this review, the development and recent progress towards different synthesis strategies to generate both powder and membrane/film-based ZIF materials are analysed and summarised. Their attractive and potential applications in gas separation, catalysis, sensing and electronic devices, and drug delivery in the past years are discussed and reviewed. In addition, the prospects and potential new development of ZIF materials are presented.

Nanocarbon production by arc discharge in water

Abstract Carbon nanostructures (onions, nanotubes and encapsulates) were generated by arc discharge in water between pure and catalyst-doped graphite electrodes. These structures were of fine quality and crystalline morphology, similar to those formed in He arc plasma. Emission spectroscopy was performed to assess the plasma components (H, O, C and C2) and temperature values. C2 radicals were determined quantitatively, between 1015 and 1016 cm−2 depending on graphite anode composition.The temperature was between 4000 and 6500 K.

Ideal Three‐Dimensional Electrode Structures for Electrochemical Energy Storage

Three-dimensional electrodes offer great advantages, such as enhanced ion and electron transport, increased material loading per unit substrate area, and improved mechanical stability upon repeated charge-discharge. The origin of these advantages is discussed and the criteria for ideal 3D electrode structure are outlined. One of the common features of ideal 3D electrodes is the use of a 3D carbon- or metal-based porous framework as the structural backbone and current collector. The synthesis methods of these 3D frameworks and their composites with redox-active materials are summarized, including transition metal oxides and conducting polymers. The structural characteristics and electrochemical performances are also reviewed. Synthesis of composite 3D electrodes is divided into two types - template-assisted and template-free methods - depending on whether a pre-made template is required. The advantages and drawbacks of both strategies are discussed.

Tungsten oxide tree-like structures

Abstract An interesting micrometer scale tree-like structure has been generated by heating a W foil, partly covered by a SiO 2 plate, in an Ar atmosphere at ca. 1600°C. Upon sonication, the trees are broken into nanoneedles (ca. 5–50 nm wide and 20–200 nm long) and planar polyhedral nanoparticles (ca. 10–50 nm cross-section). Structural analysis, using ED, EDX, XRD, and HRTEM, showed that: (1) the trees consist of well-crystallised WO x phases ( x =0–3); (2) the nanoneedles are composed mainly of monoclinic W 18 O 49 phases; and (3) the nanoparticles consist primarily of WO 3 . The tree growth is thought to arise from the intrinsic crystalline feature of WO x , the planar defect or the shear structure of which is responsible for the breakdown of the trees.

Synthesis and biocompatibility of porous nano-hydroxyapatite/collagen/alginate composite

Porous nano-hydroxyapatite/collagen/alginate (nHAC/Alginate) composite containing nHAC and Ca-crosslinked alginate is synthesized biomimetically. This composite shows a significant improvement in mechanical properties over nHAC material. Mechanical test results show that the compressive modulus and yield strength of this composite are in direct proportion to the percentage of Ca-crosslinked alginate in the composite. Primary biocompatibility experiments in vitro including fibroblasts and osteoblasts co-culture with nHAC/alginate composite indicated the high biocompatibility of this composite. Therefore the composite can be a promising candidate of scaffold material for bone tissue engineering.

Porous carbon-based materials for hydrogen storage: advancement and challenges

The development of highly efficient hydrogen storage materials is one of the main challenges that must be tackled in a widely expected hydrogen economy. Physisorption in porous materials with high surface areas and chemisorption in hydrides are the two main options for solid state hydrogen storage, and both options possess their inherent advantages and drawbacks. In this work, recent progress towards porous carbon-based materials for hydrogen storage is analyzed and reviewed. The hydrogen storage performance of plain porous carbons, metal-supported porous carbons and porous carbons confined hydrides is summarized. Some strategies for effectively controlling the hydrogen storage capacity and tuning the hydrogen adsorption enthalpy for porous carbon materials via appropriate manipulation of surface area, pore volume and pore size are discussed in detail. The new development of porous carbon-based materials for hydrogen storage is particularly emphasized.

Selective Co-catalysed growth of novel MgO fishbone fractal nanostructures

Abstract Novel MgO fishbone- or fern-like nanostructures, and Al 2 O 3 fibre networks, have been generated for the first time from an Al 2 O 3 matrix containing MgO and SiO 2 . The significance of the selective Co-catalysed growth of the elegant three-dimensional fractal fishbones is discussed. We have adopted the vapour–liquid–solid (V–L–S) and nucleation–aggregation (N–A) mechanisms, which take effect equally during the heating process, to account for the formation of these uniquely stacked fractal structures.

Osteoblasts Adherence and Migration through Three-dimensional Porous Mineralized Collagen Based Composite: nHAC/PLA

Osteoblast cells were separated from the neonatal rat calvaria and co-cultured on a novel mineralized hydroxyapatite/collagen/poly(lactic acid) composite scaffold. By using this static cell culture, a three-dimensional osteoblasts/composite bone-like was constructed in vitro. The culture process was observed by scanning electron microscopy, fluorescence microscopy, confocal laser scanning microscopy, and histological analysis. Cells were observed to spread and proliferate throughout the inner-pores of the scaffold material. After a 12-day culture, the cells had grown into the interior scaffold about 200–400 μm depth of the composite by histological section observation. This mobile behavior of osteoblasts appeared to be similar to the composition and hierarchical structure of bone tissue. The adherence and migration of osteoblast cells in this three-dimensional composite is clinically important for large bone defect repair based on tissue engineering.

Cobalt sulfide/N,S codoped porous carbon core-shell nanocomposites as superior bifunctional electrocatalysts for oxygen reduction and evolution reactions.

Exploring highly-efficient and low-cost bifunctional electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reactions (OER) in the renewable energy area has gained momentum but still remains a significant challenge. Here we present a simple but efficient method that utilizes ZIF-67 as the precursor and template for the one-step generation of homogeneous dispersed cobalt sulfide/N,S-codoped porous carbon nanocomposites as high-performance electrocatalysts. Due to the favourable molecular-like structural features and uniform dispersed active sites in the precursor, the resulting nanocomposites, possessing a unique core-shell structure, high porosity, homogeneous dispersion of active components together with N and S-doping effects, not only show excellent electrocatalytic activity towards ORR with the high onset potential (around -0.04 V vs.-0.02 V for the benchmark Pt/C catalyst) and four-electron pathway and OER with a small overpotential of 0.47 V for 10 mA cm(-2) current density, but also exhibit superior stability (92%) to the commercial Pt/C catalyst (74%) in ORR and promising OER stability (80%) with good methanol tolerance. Our findings suggest that the transition metal sulfide-porous carbon nanocomposites derived from the one-step simultaneous sulfurization and carbonization of zeolitic imidazolate frameworks are excellent alternative bifunctional electrocatalysts towards ORR and OER in the next generation of energy storage and conversion technologies.