Mechanical Reinforcement of Continuous Flow Spun Polyelectrolyte Complex Fibers

A simple continuous flow wet-spinning method to achieve mechanical reinforcement of the two oppositely charged biopolymers chitosan and gellan gum is described. The mechanical properties of these biopolymers are influenced by the order of addition. Using a facile method for mechanical reinforcement of gellan gum/chitosan fibers resulted in increases in Young's modulus, tensile strength, and toughness. Spinning gellan gum into chitosan resulted in the strongest fibers. We show that our fibers can provide a mechanical alternative for bio-fibers without the need of cross-linking. It is demonstrated that the fibers become ionically conducting in the presence of water vapor.

Biotemplated fabrication of a novel hierarchical porous C/LiFePO4/C composite for Li-ion batteries

Hierarchical porous composites are a potentially attractive material for high-rate cathode. This work presents a facile sol-gel process for the fabrication of a hierarchical porous C/LiFePO4/bio-C composite by using artemia cyst shells as natural biological carbon templates. The C/LiFePO4/bio-C composite exhibits a superior electrochemical performance with discharge capacities of 105 mA h g-1, 93 mA h g-1 and 80 mA h g-1 at 5 C, 10 C and 20 C, respectively. Remarkably, it produces a high discharge capacity of 69.1 mA h g-1 and no fading after 50 cycles even at a high current density of 6800 mA g-1. This journal is

Synthesis of single-crystalline LiFePO4 with rhombus-like morphology

In this investigation, carbon-coated LiFePO4 cathode materials were synthesized with a facile hydrothermal method. The structure and electrochemical properties of the materials were investigated by X-ray diffraction (XRD), Roman, transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS), and electrochemical impedance spectroscopy (EIS). By adjusting the mixing concentration of starting materials, a single-crystalline LiFePO4 with an anisotropic rhombus morphology (Space Group: Pmnb No. 62) were successfully synthesized. In addition, the carbon coated on the surface of LiFePO4 material prepared has a lower ID/IG (0.80), which indicates an optimized carbon structure with an increased amount of sp2-type carbon. Electrochemical performance test shows that the carbon-coated LiFePO4 cathode materials have an initial discharge capacity of 146 mAh g−1 at 0.2C.

High N-content holey few-layered graphene electrocatalysts: Scalable solvent-less production

Few layered nitrogen doped graphene (NG) attracts great interest in energy storage and conversion applications due to its electronic and catalytic properties. However, its bulk production cannot be envisioned by the current synthetic methods. Here we report a facile, solvent-less, low cost and high yield process for the synthesis of NG. Mechanochemical solid-state exfoliation allows scalable synthesis of holey and crumple nitrogen-doped few-layered graphene from graphite with controlled high concentration N doping and a high surface area through ball-milling. By adjusting the ratio of starting materials, the nitrogen content can be modulated from 4.87 to 17.83 at.%. Furthermore, the types of nitrogen-containing species in few-layered graphene can also be controlled. The resultant NG exhibits superior oxygen reduction reaction performance and more reliable stability than commercial Pt/C catalysts. This journal is

Graphene oxide decorated diatom silica particles as new nano-hybrids: Towards smart natural drug microcarriers

Herein, we demonstrate the fabrication of a novel nano-hybrid material based on diatom silica microparticles from diatomaceous earth (DE) and graphene oxide (GO). Two different approaches for the fabrication of nano-hybrids were used, including covalent coupling of GO sheets onto the diatom surface and electrostatic attachment. Covalent attachment was carried out through a facile amine coupling strategy via activation of carboxyl groups on GO, followed by covalent attachment to amine terminal groups of 3-aminopropyl-triethoxysilane (APTES) functionalized DE particles. Electrostatic attachment of GO (i.e. negatively charged) was carried out on positively charged APTES functionalized DE particles. The GO decorated DE nano-hybrids prepared with both the fabrication processes were extensively characterized by SEM, TEM, FTIR, and Raman spectroscopy to confirm the new chemical composition and structure. The application of the GO-DE nano-hybrid as a smart pH sensitive micro-drug carrier at pH 7.4 and pH 3.5 was demonstrated using a model drug, indomethacin (IMC). Finally, the drug release data were fitted to zero-order and Korsmeyer-Peppas models to understand the mechanism of drug release. This journal is © The Royal Society of Chemistry.

Achieving outstanding mechanical performance in reinforced elastomeric composite fibers using large sheets of graphene oxide

A simple fiber spinning method used to fabricate elastomeric composite fibers with outstanding mechanical performance is demonstrated. By taking advantage of the large size of as-prepared graphene oxide sheets (in the order of tens of micrometers) and their liquid crystalline behavior, elastomeric composite fibers with outstanding low strain properties have been fabricated without compromising their high strain properties. For example, the modulus and yield stress of the parent elastomer improved by 80- and 40-fold, respectively, while maintaining the high extensibility of ∼400% strain inherent to the parent elastomer. This outstanding mechanical performance was shown to be dependent upon the GO sheet size. Insights into how both the GO sheet size dimension and dispersion parameters influence the mechanical behavior at various applied strains are discussed.

Single step preparation of meso-porous and reduced graphene oxide by gamma-ray irradiation in gaseous phase

A facile and highly efficient route to produce simultaneously porous and reduced graphene oxide by gamma ray irradiation in hydrogen is here demonstrated. Narrowly distributed nano-scale pores (average size of ∼3 nm and surface density >44,900 pore μm-2) were generated across 10 μm thick graphene oxide bucky-papers at a total irradiation dose of 500 kGy. The graphene oxide sheet reduction was confirmed to occur homogeneously across the structures by Fourier transform infrared spectroscopy and Raman analysis. This one-step, catalyst-free, high penetration and through-put technique, offers great promises potential for the mass production of reduced graphene oxide from cheap graphene oxide. © 2013 Elsevier Ltd. All rights reserved.

Study on LiFe1 − xSmxPO4/C used as cathode materials for lithium-ion batteries with low Sm component

LiFe1 − xSmxPO4/C cathode materials were synthesized though a facile hydrothermal method. Compared with high-temperature solid-phase sintering, the method can allow for the fabrication of low Sm content (2 %), a scarce and expensive rare earth element, while the presence of an optimized carbon coating with large amount of sp2-type carbon sharply increases the material’s electrochemical performance. The high-rate dischargeability at 5 C, as well as the exchange current density, can be increased by 21 and 86 %, respectively, which were attributed to the fine size and the large cell parameter a/c as much. It should be pointed out that the a/c value will be increased for the LiFePO4 Sm-doped papered by both of the two methods, while the mechanism is different: The value c is increased for the front and the value a is decreased for the latter, respectively.

Large-scale production of h-In2O3/carbon nanocomposites with enhanced lithium storage properties

h-In2O3/carbon nanocomposites were obtained via a facile ball milling process from a mixture of h-In2O3 nanoparticles and Super P carbon. Compared to pure h-In2O3 nanoparticles, the nanocomposites exhibited an initial discharge capacity of 1360 mAh g-1, a stable reversible capacity of 867 mAh g-1 after 100 cycles as well as a high coulombic efficiency of 99%. The superior lithium-ion battery performance can be attributed to the specific structure of h-In2O3 and the uniform and continuous nano-carbon coating layers. The nano-carbon coating could protect the inner active materials from fragmentation and increase the electronic conductivity. This study not only provides a promising electrode material for high-performance lithium-ion batteries, but also further demonstrates a straightforward, effective and environmental friendly process for synthesizing nanocomposites. © 2014 Elsevier Ltd.

Oxygen-doped boron nitride nanosheets with excellent performance in hydrogen storage

Hydrogen is considered one of the best energy sources. However, the lack of effective, stable, and safe storage materials has severely prevented its practical application. Strong effort has been made to try new nanostructured materials as new storage materials. In this study, oxygen-doped boron nitride (BN) nanosheets with 2-6 atomic layers, synthesized by a facile sol-gel method, show a storage capacity of 5.7wt% under 5MPa at room temperature, which is the highest hydrogen storage ever reported for any BN materials. Importantly, 89% of the stored hydrogen can be released when the hydrogen pressure is reduced to ambient conditions. Furthermore, the BN nanosheets exhibit an excellent storage cycling stability due to the stable two-dimensional nanostructure. The first principles calculations reveal that the high hydrogen storage mainly origins from the oxygen-doping of the BN nanosheets with increased adsorption energies of H2 on BN by 20-80% over pure BN sheets at the different coverage. © 2014 Elsevier Ltd.

Tunable dual-stimuli response of a microgel composite consisting of reduced graphene oxide nanoparticles and poly(N-isopropylacrylamide) hydrogel microspheres

A type of photo- and thermo-responsive composite microsphere composed of reduced graphene oxide nanoparticles and poly(N-isopropylacrylamide) (rGO@pNIPAM) is successfully fabricated by a facile solution mixing method. Due to the high optical absorbance and thermal conduction of rGO, the composite microspheres are endowed with the new property of photo-response, in addition to the intrinsic thermally sensitive property of pNIPAM. This new ability undoubtedly enlarges the scope of applications of the microgel spheres. Furthermore, through controlling the rGO content in the composite, the photo- and thermo-sensitivity of the composite can be effectively modulated. That is, with a lower rGO content (≤32% by weight), the composite microspheres perform only thermally induced changes, such as volume contraction (by ∼45% in diameter) and drug release, when crossing the lower critical solution temperature of pNIPAM. With a higher rGO content (∼47.5%), both temperature and light irradiation can trigger changes in the composite. However, when the rGO content is increased to around 64.5%, the thermo-responsivity of the composite disappears, and the spheres exhibit only photo-induced drug release. With a further increase in rGO content, the environmentally responsive ability of the microspheres vanishes. This journal is © the Partner Organisations 2014.

High-performance multifunctional graphene yarns: toward wearable all-carbon energy storage textiles

The successful commercialization of smart wearable garments is hindered by the lack of fully integrated carbon-based energy storage devices into smart wearables. Since electrodes are the active components that determine the performance of energy storage systems, it is important to rationally design and engineer hierarchical architectures atboth the nano- and macroscale that can enjoy all of the necessary requirements for a perfect electrode. Here we demonstrate a large-scale flexible fabrication of highly porous high-performance multifunctional graphene oxide (GO) and rGO fibers and yarns by taking advantage of the intrinsic soft self-assembly behavior of ultralarge graphene oxide liquid crystalline dispersions. The produced yarns, which are the only practical form of these architectures for real-life device applications, were found to be mechanically robust (Young's modulus in excess of 29 GPa) and exhibited high native electrical conductivity (2508 ± 632 S m(-1)) and exceptionally high specific surface area (2605 m(2) g(-1) before reduction and 2210 m(2) g(-1) after reduction). Furthermore, the highly porous nature of these architectures enabled us to translate the superior electrochemical properties of individual graphene sheets into practical everyday use devices with complex geometrical architectures. The as-prepared final architectures exhibited an open network structure with a continuous ion transport network, resulting in unrivaled charge storage capacity (409 F g(-1) at 1 A g(-1)) and rate capability (56 F g(-1) at 100 A g(-1)) while maintaining their strong flexible nature.

Highly crumpled boron nitride nanosheets as adsorbents: scalable solvent-less production

Boron nitride nanosheets (BNNSs), so-called “white graphene”, have recently received increasing attention, both theoretically and experimentally. Although many synthetic procedures have been proposed for the synthesis of BNNSs, finding a simple, solvent-less, catalyst-free, and large-scale production route is still a challenge. Here, a facile, solvent-less, low cost, and high yield process is developed, in which mechanical solid-state exfoliation allows scalable production of crumple BNNSs from commercial BN powders with a high surface area. Importantly, these BNNSs show unprecedentedly high adsorption of proteins described by various adsorption isotherms and kinetics models. In addition, the saturated BNNSs exhibit excellent recyclability, and maintain a high sorption capacity even after five cycles through simply regeneration process of heating in air. This easy recyclability route further demonstrates the great potential of BNNSs for water cleaning application.

A superamphiphobic coating with an ammonia-triggered transition to superhydrophilic and superoleophobic for oil-water separation

Superhydrophilic and superoleophobic materials are very attractive for efficient and cost-effective oil-water separation, but also very challenging to prepare. Reported herein is a new superamphiphobic coating that turns superhydrophilic and superoleophobic upon ammonia exposure. The coating is prepared from a mixture of silica nanoparticles and heptadecafluorononanoic acid-modified TiO2 sol by a facile dip-coating method. Commonly used materials, including polyester fabric and polyurethane sponge, modified with this coating show unusual capabilities for controllable filtration of an oil-water mixture and selective removal of water from bulk oil. We anticipate that this novel coating may lead to the development of advanced oil-water separation techniques.