46 research outputs found
Sulfur-doped Nanographenes Containing Multiple Subhelicenes
In this work, we describe the synthesis and characterization of three novel sulfur-doped nanographenes (NGs) (1â3) 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 1â3 possess dihedral angles from 15° to 34°. The optical energy gaps of 1â3 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
A novel 2D hybrid with MoSâ nanocrystals strongly coupled on nitrogen-enriched graphene (MoSâ/NGg-CâNâ) is realized by mild temperature pyrolysis (550 °C) of a self-assembled precursor (MoSâ/g-CâNââHâș/GO). With rich active sites, the boosted electronic conductivity and the coupled structure, MoSâ/NGgâCâNâ achieves superior lithium storage performance
Single Diamond Structured Titania Scaffold
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
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 gâ»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 gâ»Âč at 0.1 A gâ»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
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 ethanolâwater 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 electrodeâelectrolyte interfaces, resulted in good capacitive performance of the supercapacitors. Moreover, a high energy density of ca. 14 Wh kgâ1 and a high power density of 6.2 kW kgâ1 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
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 (5-20ânm) and thickness (35-45ânm) as well as enlarged specific surface area (85âm(2)âg(-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 MetalâPolymer âBrushesâ
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 AuNRâpolymer
âbrushesâ 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