A mean-field phase diagram for conformationally symmetric diblock melts using the standard Gaussian polymer model is presented. Our calculation, which traverses the weak- to strong-segregation regimes, is free of traditional approximations. Regions of stability are determined for disordered (DIS) melts and for ordered structures including lamellae (L), hexagonally packed cylinders (H), body-centered cubic spheres (QIm3m), close-packed spheres (CPS), and the bicontinuous cubic network with Ia3d symmetry (QIa3d). The CPS phase exists in narrow regions along the order−disorder transition for χN ≥ 17.67. Results suggest that the QIa3d phase is not stable above χN ∼ 60. Along the L/QIa3d phase boundaries, a hexagonally perforated lamellar (HPL) phase is found to be nearly stable. Our results for the bicontinuous Pn3m cubic (QPn3m) phase, known as the OBDD, indicate that it is an unstable structure in diblock melts. Earlier approximation schemes used to examine mean-field behavior are reviewed, and compa...

Unifying Weak- and Strong-Segregation Block Copolymer Theories

As one important component of sulfur cathodes, the carbon host plays a key role in the electrochemical performance of lithium-sulfur (Li-S) batteries. In this paper, a mesoporous nitrogen-doped carbon (MPNC)-sulfur nanocomposite is reported as a novel cathode for advanced Li-S batteries. The nitrogen doping in the MPNC material can effectively promote chemical adsorption between sulfur atoms and oxygen functional groups on the carbon, as verifi ed by X-ray absorption near edge structure spectroscopy, and the mechanism by which nitrogen enables the behavior is further revealed by density functional theory calculations. Based on the advantages of the porous structure and nitrogen doping, the MPNC-sulfur cathodes show excellent cycling stability (95% retention within 100 cycles) at a high current density of 0.7 mAh cm −2 with a high sulfur loading (4.2 mg S cm −2 ) and a sulfur content (70 wt%). A high areal capacity (≈3.3 mAh cm −2 ) is demonstrated by using the novel cathode, which is crucial for the practical application of Li-S batteries. It is believed that the important role of nitrogen doping promoted chemical adsorption can be extended for development of other high performance carbon-sulfur composite cathodes for Li-S batteries.

Nitrogen-Doped Mesoporous Carbon Promoted Chemical Adsorption of Sulfur and Fabrication of High-Areal-Capacity Sulfur Cathode with Exceptional Cycling Stability for Lithium-Sulfur Batteries

Bio-integrated wearable systems can measure a broad range of biophysical, biochemical, and environmental signals to provide critical insights into overall health status and to quantify human performance. Recent advances in material science, chemical analysis techniques, device designs, and assembly methods form the foundations for a uniquely differentiated type of wearable technology, characterized by noninvasive, intimate integration with the soft, curved, time-dynamic surfaces of the body. This review summarizes the latest advances in this emerging field of “bio-integrated” technologies in a comprehensive manner that connects fundamental developments in chemistry, material science, and engineering with sensing technologies that have the potential for widespread deployment and societal benefit in human health care. An introduction to the chemistries and materials for the active components of these systems contextualizes essential design considerations for sensors and associated platforms that appear in f...

Bio-Integrated Wearable Systems: A Comprehensive Review

Correction for ‘Review of electrical energy storage technologies, materials and systems: challenges and prospects for large-scale grid storage’ by Turgut M. Gur, Energy Environ. Sci., 2018, DOI: 10.1039/c8ee01419a.

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Correction: Review of electrical energy storage technologies, materials and systems: challenges and prospects for large-scale grid storage

Metal-halide perovskites have rapidly emerged as one of the most promising materials of the 21st century, with many exciting properties and great potential for a broad range of applications, from photovoltaics to optoelectronics and photocatalysis. The ease with which metal-halide perovskites can be synthesized in the form of brightly luminescent colloidal nanocrystals, as well as their tunable and intriguing optical and electronic properties, has attracted researchers from different disciplines of science and technology. In the last few years, there has been a significant progress in the shape-controlled synthesis of perovskite nanocrystals and understanding of their properties and applications. In this comprehensive review, researchers having expertise in different fields (chemistry, physics, and device engineering) of metal-halide perovskite nanocrystals have joined together to provide a state of the art overview and future prospects of metal-halide perovskite nanocrystal research.

State of the Art and Prospects for Halide Perovskite Nanocrystals.

Ultra-long cycle life, low-cost room temperature sodium-sulfur batteries enabled by highly doped (N,S) nanoporous carbons

Superstretchable, Self‐Healing Polymeric Elastomers with Tunable Properties

A nanoporous nitrogen doped carbon matrix was prepared by carbonization of metal–organic framework zeolitic imidazolate framework (ZIF-8) precursors. The doped carbon matrix was melt-infiltrated with sulfur to form a carbonized ZIF-8/S composite. The composite material exhibited good performance as the cathode for room-temperature sodium–sulfur battery (Na–S) systems. A reversible specific capacity of around 1000 mA h g−1 could be achieved at a rate of 0.1C; and a reversible specific capacity of 500 mA h g−1 was obtained at a rate of 0.2C after 250 cycles. The good performance of the Na–S battery could be attributed to the synergistic effect from the nanoporosity of the carbon matrix and the high nitrogen-doping content (ca. ∼18 at%). These attributes enhanced the entrapment of the sulfur molecules inside the carbon matrices.

A nitrogen doped carbonized metal–organic framework for high stability room temperature sodium–sulfur batteries

A binary Ni/Co metal organic framework (Ni–Co-MOF) with a hollow-sphere structure that is decorated with cone-shaped protrusions was prepared via a facile solvothermal reaction. Carbonization and sulfurization of the Ni–Co-MOF produced a Ni3S2/Co9S8/N-doped carbon composite that retained the hierarchical structure. The final composite material presents exceptional electrochemical performance when used as an anode in sodium-ion batteries. A reversible specific capacity of 419.9 mA h g−1 at a current density of 0.1 A g−1 was achieved after 100 cycles, with an exceptional capacity retention of 98.6%. Furthermore, superior rate capability was also demonstrated: an average capacity of 323.2 mA h g−1 at a current density of 2 A g−1 can be achieved. This exceptional performance can be attributed to the unique nano-architecture derived from the MOF precursor, as the resultant material possesses an ideal profile for an excellent anode material: ultrafine Ni3S2 and Co9S8 particles (∼7 nm), a hollow, porous structure, and an ultrathin N-doped carbon coating.

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A binary metal organic framework derived hierarchical hollow Ni3S2/Co9S8/N-doped carbon composite with superior sodium storage performance

One challenge associated with the utilization of block copolymers in nanotechnology is the difficulties associated with alignment and orientation of the self-assembled nanostructure on macroscopic length scales. Here we demonstrate a simple method to generate unidirectional alignment of the cylindrical domains of polystyrene-block-polyisoprene-block-polystyrene, SIS, based on a modification of the commonly utilized solvent vapor annealing (SVA) process. In this modification, cross-linked poly(dimethylsiloxane) (PDMS) is physically adhered to the SIS film during SVA; differential swelling of the PDMS and SIS produces a shear force to align the ordered domains of SIS in the areas covered by PDMS. This method is termed solvent vapor annealing with soft shear (SVA-SS). The alignment direction can be readily controlled by the shape and placement of the PDMS with the alignment angle equal to the diagonal across the rectangular PDMS pad due to a propagating deswelling front from directional drying of the PDMS by...

Zhe Qiang

Papers

Ultra-long cycle life, low-cost room temperature sodium-sulfur batteries enabled by highly doped (N,S) nanoporous carbons

Superstretchable, Self‐Healing Polymeric Elastomers with Tunable Properties

A nitrogen doped carbonized metal–organic framework for high stability room temperature sodium–sulfur batteries

A binary metal organic framework derived hierarchical hollow Ni3S2/Co9S8/N-doped carbon composite with superior sodium storage performance

Unidirectional Alignment of Block Copolymer Films Induced by Expansion of a Permeable Elastomer during Solvent Vapor Annealing