A novel magnetic composition of the high surface area particles with amide chemical functionality, Sephacryl S‐200, is reported enabling the preparative‐scale (1 L, ≈5–10 mg) separation of metallic and semiconducting single‐walled carbon nanotubes (SWNT) from completely unpurified and uncentrifuged nanotube stocks. Sephacryl S‐200 has previously been utilized in separating semiconducting SWNT (s‐SWNT) on the laboratory scale. Significantly, use of these magnetic derivative particles in absorptive separation of SWNT allows the unprecedented and industrially scalable purification of both metallic SWNT (m‐SWNT) as well as s‐SWNT directly from uncentrifuged, ultrasonicated surfactant‐based SWNT solutions by simple and scalable magnetic separation. These particles also allowed for the systematic study on the effect of SWNT–polymer interaction time on the resulting SWNT “payloads.” Ultimately, high ‐purity m‐SWNT and s‐SWNT products are independently achieved by controlling the SWNT–polymer interaction time and relative concentrations, as well as SWNT sonication conditions. Furthermore, by controlling these factors, single‐chirality (6,5) s‐SWNT can be isolated with 92% purity directly from unpurified stocks. Thermogravimetric analysis indicates a total process SWNT yield of 1.2% and 1.7% for m‐SWNT and s‐SWNT, respectively. These results demonstrate the potential for a preparative method for separating carbon nanotubes based on electronic properties. 相似文献
The exploration of high‐energy and stable cathode materials is highly desirable and challenging for the development of advanced Zn‐based batteries. In this work, a facile pyrolysis method is reported to synthetize Ni3S2/carbon nanocomposite as high‐performance cathode by employing ion exchange resin as a precursor. Attributing to the abundant active sites and enhanced conductivity from well binding between Ni3S2 and carbon, a markedly high capacity of 234.3 mA h g?1 is obtained for this Ni3S2/carbon at a high current density of 6.9 A g?1. Moreover, a Zn‐based battery is demonstrated by using the Ni3S2/carbon as a cathode and Zn plate as an anode, which delivers a maximum power density of 58.6 kW kg?1, together with a peak energy density of 356 W h kg?1 and 93.7% capacity retention after 5000 charging–discharging cycles. This simple synthetic strategy to achieve robust Ni‐based composite electrodes may open up new opportunities to design other transition metal–based electrodes for energy storage applications. 相似文献
Multi scale hierarchical structures underpin mechanical, optical, and wettability behavior in nature. Here we present a novel approach which can be used to mimic the natural hierarchical patterns in a quick and easy maskless fabrication. By using two‐beam interference lithography with angle‐multiplexed exposures and scanning, we have successfully printed large‐area complex structures having a cascading resolution and 3D surface profiles. By precisely controlling the exposure dose we have demonstrated a capability to create different 3D textured surfaces having comparable aspect ratio with period spanning from 4 μm to 300 nm (more than one order of magnitude) and the height spanning from 0.9 μm to 40 nm, respectively. Up to three levels of biomimetic hierarchical structures were obtained that show several natural phenomena: superhydrophobicity, iridescence, directionality of reflectivity, and polarization at different colors.
A 3D HSQC-HSQMBC experiment is proposed for increasing the separation of proton–carbon long-range correlation cross peaks, the lack of which is occasionally seen in corresponding 2D experiments. It is aimed at complex molecules with many protonated carbons exhibiting a narrow spread of 13C chemical shifts e.g., complex carbohydrates. It does not yield long-range correlation of quaternary carbons. An extra indirectly detected 1H dimension of this experiment provides additional separation of long-range correlation cross peaks by utilising the chemical shifts of protons directly attached to 13C. Evolution of single-quantum coherences throughout the entire pulse sequence ensures that the cross peaks are inphase pure absorption singlets in both indirectly detected dimensions, thus maximising the resolution and sensitivity of the experiment. Partial signal cancellation can be expected due to the antiphase character of peaks in the directly detected dimension. The intensity of cross peaks depends on the length of a single long-range evolution interval and values of both active and passive long-range coupling constants of each carbon. The 3D HSQC-HSQMBC experiment provided high quality long-range correlation spectra of a 2 mg pentasaccharide sample in 27 h. The technique can also be used for measurement of long-range heteronuclear coupling constants from pure antiphase multiplets in the directly detected dimension. 相似文献
An efficient electrocatalyst for oxygen evolution has been prepared via the deposition of iron–nickel layered double‐hydroxide (FeNi‐LDH) nanosheets on 3D carbon network as the building scaffold in a one‐step hydrothermal process. It is found that upon the assembling of FeNi‐LDH nanosheets with graphene into the 3D cross‐linked hybrid, the FeNi‐LDH/graphene hybrid features a well‐improved catalytic activity towards the oxygen evolution reaction (OER) with a good stability during the long‐term cycling experiment. Moreover, the hybrid catalyst is also active in the oxygen reduction reaction (ORR), qualifying it as a new type of bifunctional catalyst that can work in metal–air batteries. 相似文献
ABSTRACTThe thermal compression behaviour of Al–Zn–Mg alloy was studied on a thermal simulator machine at the temperature range of 380–540°C and strain rate range of 0.01–10?s?1. The constitutive equation and 3D processing map of the alloys were established. The microstructure characteristics of the alloy were studied by metallographic observation, electron back-scatter diffraction (EBSD) analysis and transmission electron microscopy (TEM) microstructure analysis. The results show that the peak stress of high-temperature deformation of alloy decreases with the increase of deformation temperature and increases with the increase of strain rate. The dynamic recovery of the alloy occurs at the temperature range of 380–460°C and the strain rate range of 0.01–0.1?s?1. The dynamic recrystallization of the alloy occurs at the temperature range of 460–500°C and the strain rate range of 0.01–0.1?s?1. The alloy maintains fine and uniform recrystallized grains at a temperature range of 460–480°C and a strain rate range of 0.01–0.1?s?1, which is suitable for hot working. 相似文献
True three‐dimensionally (3D) integrated biochips are crucial for realizing high performance biochemical analysis and cell engineering, which remain ultimate challenges. In this paper, a new method termed hybrid femtosecond laser microfabrication which consists of successive subtractive (femtosecond laser‐assisted wet etching of glass) and additive (two‐photon polymerization of polymer) 3D microprocessing was proposed for realizing 3D “ship‐in‐a‐bottle” microchip. Such novel microchips were fabricated by integrating various 3D polymer micro/nanostructures into flexible 3D glass microfluidic channels. The high quality of microchips was ensured by quantitatively investigating the experimental processes containing “line‐to‐line” scanning mode, improved annealing temperature (645°C), increased prebaking time (18 h for 1mm‐length channel), optimal laser power (1.9 times larger than that on the surface) and longer developing time (6 times larger). The ship‐in‐a‐bottle biochips show high capabilities to provide simultaneous filtering and mixing with 87% efficiency in a shorter distance and on‐chip synthesis of ZnO microflower particles. 相似文献
The facile hydrothermal synthesis of polyethyleneimine (PEI)‐coated iron oxide (Fe3O4) nanoparticles (NPs) doped with Gd(OH)3 (Fe3O4‐Gd(OH)3‐PEI NPs) for dual mode T1‐ and T2‐weighted magnetic resonance (MR) imaging applications is reported. In this approach, Fe3O4‐Gd(OH)3‐PEI NPs are synthesized via a hydrothermal method in the presence of branched PEI and Gd(III) ions. The PEI coating onto the particle surfaces enables further modification of poly(ethylene glycol) (PEG) in order to render the particles with good water dispersibility and improved biocompatibility. The formed Fe3O4‐Gd(OH)3‐PEI‐PEG NPs have a Gd/Fe molar ratio of 0.25:1 and a mean particle size of 14.4 nm and display a relatively high r2 (151.37 × 10?3m ?1 s?1) and r1 (5.63 × 10?3m ?1 s?1) relaxivity, affording their uses as a unique contrast agent for T1‐ and T2‐weighted MR imaging of rat livers after mesenteric vein injection of the particles and the mouse liver after intravenous injection of the particles, respectively. The developed Fe3O4‐Gd(OH)3‐PEI‐PEG NPs may hold great promise to be used as a contrast agent for dual mode T1‐ and T2‐weighted self‐confirmation MR imaging of different biological systems. 相似文献
Electrocatalysts for the oxygen reduction reaction (ORR) present some of the most challenging vulnerability issues reducing ORR performance and shortening their practical lifetime. Fuel crossover resistance, selective activity, and catalytic stability of ORR catalysts are still to be addressed. Here, a facile and in situ template‐free synthesis of Pt‐containing mesoporous nitrogen‐doped carbon composites (Pt‐m‐N‐C) is designed and specifically developed to overcome its drawback as an electrocatalyst for ORR, while its high activity is sustained. The as‐prepared Pt‐m‐N‐C catalyst exhibits high electrocatalytic activity, dominant four‐electron oxygen reduction pathway, superior stability, fuel crossover resistance, and selective activity to a commercial Pt/C catalyst in 0.1 m KOH aqueous solution. Such excellent performance benefits from in situ covalent incorporation of Pt nanoparticles with optimal size into N‐doped carbon support, dense active catalytic sites on surface, excellent electrical contacts between the catalytic sites and the electron‐conducting host, and a favorable mesoporous structure for the stabilization of the Pt nanoparticles by pore confinement and diffusion of oxygen molecules. 相似文献