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How defects between layers of porous membranes affect their gas separation performance is still a problem. Here, we design three bilayer porous graphene membranes with different and representative defect torsion angles to regulate gas separation. We find from first-principles density functional theory calculations that the selectivity of the H 2 /CH 4 mixture can be varied by several orders of magnitude, of about 107:1 (E barrier/CH4 : 0.24, 0.18, 0.24 eV), 1019:1 (E barrier/CH4 : 0.49, 0.37, 0.47 eV) and 1012:1 (E barrier/CH4 : 0.42, 0.15, 0.45 eV), when going through the models of bi-H pore10 -20 x , bi-H pore10 -20 y and bi-H pore10 -47 y. Every barrier curve of gas penetration features three peaks. Additionally, molecular dynamics simulations show that the bilayer porous graphene membrane with a defect torsion angle of 20° along the x / y -axis possesses high H 2 /CH 4 separation ratio (up to 56–58:1) at room temperature after 5000 ps. The defect torsion angle of bilayer porous graphene improves the selectivity exponentially by regulating the three high penetration energy barriers of CH 4 , while the three energy barriers of H 2 are all very low. This work provides a new strategy to achieve highly selective separation of mixture by porous 2D-materials via regulating defect torsion angle between layers. [Display omitted] • The defect torsion angle is a powerful knob for regulating gas separation. • The potential energy curve for defect torsion angle model features three peaks. • Bi-H pore10 -20 y shows a high separation selectivity of 1019:1 for H 2 over CH 4. [ABSTRACT FROM AUTHOR]

Fe 2 O 3 wrapped by few layered graphene nanosheets composites (Fe 2 O 3 -FLG) have been synthesized via a facile and massive one-step P-milling method, which is effective in reducing the particle size of Fe 2 O 3 and exfoliating the graphite into FLG. The composite shows good electrochemical performance due to the tight wrapping of FLG nanosheets, which is beneficial to electric conductivity and integrity of the electrode. The sample treated under 20 h retains a reversible capacity of 758 mAh g −1 at 200 mA g −1 after 300 cycles, which equals to 88% of its theoretic capacity. With the superior electrochemical performance, Fe 2 O 3 -FLG composites prepared via the P-milling method could be promising as anode materials for high performance lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: Graphene, a novel class of carbon nanostructures, has great promise for use as sorbent materials because of its ultrahigh specific surface area. A new method using a column packed with graphene as sorbent was developed for the preconcentration of trace amounts of lead (Pb) using dithizone as chelating reagent prior to its determination by flame atomic absorption spectrometry. Some effective parameters on the extraction and complex formation were selected and optimized. Under optimum conditions, the calibration graph was linear in the concentration range of 10.0–600.0μgL−1 with a detection limit of 0.61μgL−1. The relative standard deviation for ten replicate measurements of 20.0 and 400.0μgL−1 of Pb were 3.56 and 3.25%, respectively. Comparative studies showed that graphene is superior to other adsorbents including C18 silica, graphitic carbon, and single- and multi-walled carbon nanotubes for the extraction of Pb. The proposed method was successfully applied in the analysis of environmental water and vegetable samples. Good spiked recoveries over the range of 95.3–100.4% were obtained. This work not only proposes a useful method for sample preconcentration, but also reveals the great potential of graphene as an excellent sorbent material in analytical processes. [Copyright &y& Elsevier]

A new sensitive and simple method was developed for the preconcentration of trace amounts of cobalt (Co) using 1-(2-pyridylazo)-2-naphthol (PAN) as chelating reagent prior to its determination by flame atomic absorption spectrometry. The proposed method is based on the utilization of a column packed with graphene as sorbent. Several effective parameters on the extraction and complex formation were selected and optimized. Under optimum conditions, the calibration graph was linear in the concentration range of 5.0–240.0 μg L −1 with a detection limit of 0.36 μg L −1 . The relative standard deviation for ten replicate measurements of 20.0 and 100.0 μg L −1 of Co were 3.45 and 3.18%, respectively. Comparative studies showed that graphene is superior to other adsorbents including C18 silica, graphitic carbon, and single- and multi-walled carbon nanotubes for the extraction of Co. The proposed method was successfully applied in the analysis of four real environmental water samples. Good spiked recoveries over the range of 95.8–102.6% were obtained. [ABSTRACT FROM AUTHOR]

In order to enhance the cycleability and electronic conductivity of Si-based anodes, we fabricated a hierarchical micro-nano structured silicon/graphene nanosheets (Si/GNs) hybrid by discharge plasma-assisted milling (P-milling) using Si nanoparticles and expanded graphite (EG) as starting materials. Owing to the synergistic effect of rapid plasma heating and ball mill grinding with Si nanoparticles as nanomiller, the graphene nanosheets was exfoliated efficiently from the loose structured EG, which tightly wrapped and connected the Si nanoparticles to form microsized composite agglomerates. This high powder tap density Si/GNs hybrid exhibited a high reversible capacity of 942 mAh g −1 (857 mAh cm −3 ) at the current density of 0.2 Ag −1 , with 88% capacity retention after 100 cycles. The charge capacity remained super stable more than 350 times when the electrode was cycled with a fixed lithiation capacity of 1000 mAh g −1 at a current density of 0.2 Ag −1 between 0.01 and 1.5 V (vs. Li/Li + ). This superior cycle performance was attributed to the microsized GNs matrix which facilitated the electronic conductivity and the Li + diffusion in the hybrid, and effectively accommodated the volume change of Si nanoparticles during Li + alloying and dealloying processes. [ABSTRACT FROM AUTHOR]