46 research outputs found

    Sulfur-doped Nanographenes Containing Multiple Subhelicenes

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    In this work, we describe the synthesis and characterization of three novel sulfur-doped nanographenes (NGs) (1–3) containing multiple subhelicenes, including carbo[4]helicenes, thieno[4]helicenes, carbo[5]helicenes, and thieno[5]helicenes. Density functional theory calculations reveal that the helicene substructures in 1–3 possess dihedral angles from 15° to 34°. The optical energy gaps of 1–3 are estimated to be 2.67, 2.45, and 2.30 eV, respectively. These three sulfur-doped NGs show enlarged energy gaps compared to those of their pristine carbon analogues

    A two-dimensional hybrid with molybdenum disulfide nanocrystals strongly coupled on nitrogen-enriched graphene via mild temperature pyrolysis for high performance lithium storage

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    A novel 2D hybrid with MoS₂ nanocrystals strongly coupled on nitrogen-enriched graphene (MoS₂/NGg-C₃N₄) is realized by mild temperature pyrolysis (550 °C) of a self-assembled precursor (MoS₃/g-C₃N₄–Hâș/GO). With rich active sites, the boosted electronic conductivity and the coupled structure, MoS₂/NGg₋C₃N₄ achieves superior lithium storage performance

    Single Diamond Structured Titania Scaffold

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    Single diamond (SD) network, discovered in beetles and weevils skeletons, is the holy grail in photonic materials with widest complete bandgap to date. Such structure influences the propagation of electromagnetic waves in defined frequency and is significant in photonic crystals, light-harvesting applications, optical waveguides, laser resonators, etc. However, efforts until now have not allowed a start-to-finish understanding on the production process of the unbalanced single network scaffold in natural organisms and the thermodynamical instability of SD makes it extremely difficult to be obtained by self-assembly compared to the energetically favored bicontinuous double diamond and other easily formed lattices, thus the artificial fabrication of such photonic structure in practical synthesis has last-long as a formidable challenge. Herein, we report the unprecedented bottom-up fabrication of SD titania scaffold through a one-pot co-folding scenario employing a simple diblock copolymer poly(ethylene oxide)-block-polystyrene (PEO45-b-PS241) as template and titanium diisopropoxide bis(acetylacetonate) as inorganic precursor in a mixed solvent, in which the inorganic species selectively organized in one of the skeleton enclosed by diamond minimal surface of the polymer matrix in a simultaneous assembling process. Electron crystallography investigations exhibited the tetrahedral-connected SD frameworks with space group Fd-3m in polycrystalline anatase form. Photonic bandgap calculation shows that the structure reveals a complete bandgap of 11.54 % with the dielectric contrast of titania (6.25). This work provides a straightforward solution to the complex synthesis puzzle and offers a new reference for biological relevant materials, next-generation optical devices, etc

    Nitrogen-enriched hierarchically porous carbon materials fabricated by graphene aerogel templated Schiff-base chemistry for high performance electrochemical capacitors

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    This article presents a facile and effective approach for synthesizing three-dimensional (3D) graphenecoupled Schiff-base hierarchically porous polymers (GS-HPPs). The method involves the polymerization of melamine and 1,4-phthalaldehyde, yielding Schiff-base porous polymers on the interconnected macroporous frameworks of 3D graphene aerogels. The as-synthesized GS-HPPs possess hierarchically porous structures containing macro-/meso-/micropores, along with large specific surface areas up to 776 mÂČ g⁻Âč and high nitrogen contents up to 36.8 wt%. Consequently, 3D nitrogen-enriched hierarchically porous carbon (N-HPC) materials with macro-/meso-/micropores were obtained by the pyrolysis of the GS-HPPs at a high temperature of 800 °C under a nitrogen atmosphere. With a hierarchically porous structure, good thermal stability and a high nitrogen-doping content up to 7.2 wt%, the N-HPC samples show a high specific capacitance of 335 F g⁻Âč at 0.1 A g⁻Âč in 6 M KOH, a good capacitance retention with increasing current density, and an outstanding cycling stability. The superior electrochemical performance means that the N-HPC materials have great potential as electrode materials for supercapacitors

    Facile template-free synthesis of vertically aligned polypyrrole nanosheets on nickel foams for flexible all-solid-state asymmetric supercapacitors

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    This paper reports a novel and remarkably facile approach towards vertically aligned nanosheets on three-dimensional (3D) Ni foams. Conducting polypyrrole (PPy) sheets were grown on Ni foam through the volatilization of the environmentally friendly solvent from an ethanol–water solution of pyrrole (Py), followed by the polymerization of the coated Py in ammonium persulfate (APS) solution. The PPy-decorated Ni foams and commercial activated carbon (AC) modified Ni foams were employed as the two electrodes for the assembly of flexible all-solid-state asymmetric supercapacitors. The sheet-like structure of PPy and the macroporous feature of the Ni foam, which render large electrode–electrolyte interfaces, resulted in good capacitive performance of the supercapacitors. Moreover, a high energy density of ca. 14 Wh kg−1 and a high power density of 6.2 kW kg−1 were achieved for the all-solid-state asymmetric supercapacitors due to the wide cell voltage window

    Patterning two-dimensional free-standing surfaces with mesoporous conducting polymers

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    The ability to pattern functional moieties with well-defined architectures is highly important in material science, nanotechnology and bioengineering. Although two-dimensional surfaces can serve as attractive platforms, direct patterning them in solution with regular arrays remains a major challenge. Here we develop a versatile route to pattern two-dimensional free-standing surfaces in a controlled manner assisted by monomicelle close-packing assembly of block copolymers, which is unambiguously revealed by direct visual observation. This strategy allows for bottom-up patterning of polypyrrole and polyaniline with adjustable mesopores on various functional free-standing surfaces, including two-dimensional graphene, molybdenum sulfide, titania nanosheets and even on one-dimensional carbon nanotubes. As exemplified by graphene oxide-based mesoporous polypyrrole nanosheets, the unique sandwich structure with adjustable pore sizes (5-20 nm) and thickness (35-45 nm) as well as enlarged specific surface area (85 m(2) g(-1)) provides excellent specific capacitance and rate performance for supercapacitors. Therefore, this approach will shed light on developing solution-based soft patterning of given interfaces towards bespoke functions

    Morphological Control in Aggregates of Amphiphilic Cylindrical Metal–Polymer “Brushes”

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    Controlled self-assembly of gold nanorods (AuNRs) into nanostructures of various morphologies has attracted considerable interest because it provides a high degree of freedom in tailoring the properties of the nanostructures by the coupling of the optical and electronic properties of the individual AuNRs. This paper presents a new strategy for making AuNR aggregates of tunable morphologies. In this approach, the surface of AuNRs is chemically coated with an amphiphilic diblock copolymer. The coating gives the AuNRs a cylindrical brush structure. By varying the nature of the common solvent or the interparticle electrostatic repulsion, the self-assembly of the amphiphilic cylindrical AuNR–polymer “brushes” can produce water-soluble aggregates of controllable morphologies, including single-rod ellipsoidal micelles, curved circular lamellae, and nanospheres. The AuNRs in the various aggregates generate different surface plasmon resonance (SPR) absorption patterns, with the longitudinal SPR band in the near-infrared spectral window shifting as the aggregate morphology changes
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