There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

We developed two-step solution-phase reactions to form hybrid materials of Mn3O4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Mn3O4 nanoparticles grown selectively on RGO sheets over free particle growth in solution allowed for the electrically insulating Mn3O4 nanoparticles wired up to a current collector through the underlying conducting graphene network. The Mn3O4 nanoparticles formed on RGO show a high specific capacity up to ~900mAh/g near its theoretical capacity with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn3O4 nanoparticles grown atop. The Mn3O4/RGO hybrid could be a promising candidate material for high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for design and synthesis of battery electrodes based on highly insulating materials.

Mn3O4-Graphene Hybrid as a High Capacity Anode Material for Lithium Ion Batteries

In view of the climate changes caused by the continuously rising levels of atmospheric CO2 , advanced technologies associated with CO2 conversion are highly desirable. In recent decades, electrochemical reduction of CO2 has been extensively studied since it can reduce CO2 to value-added chemicals and fuels. Considering the sluggish reaction kinetics of the CO2 molecule, efficient and robust electrocatalysts are required to promote this conversion reaction. Here, recent progress and opportunities in inorganic heterogeneous electrocatalysts for CO2 reduction are discussed, from the viewpoint of both experimental and computational aspects. Based on elemental composition, the inorganic catalysts presented here are classified into four groups: metals, transition-metal oxides, transition-metal chalcogenides, and carbon-based materials. However, despite encouraging accomplishments made in this area, substantial advances in CO2 electrolysis are still needed to meet the criteria for practical applications. Therefore, in the last part, several promising strategies, including surface engineering, chemical modification, nanostructured catalysts, and composite materials, are proposed to facilitate the future development of CO2 electroreduction.

Recent Advances in Inorganic Heterogeneous Electrocatalysts for Reduction of Carbon Dioxide

Recent advancements in supercapacitor technology

Copper sulfide–reduced graphene oxide nanocomposites were synthesized hydrothermally from copper nitrate and thiourea as precursor materials In the hydrothermal route, rGO is formed by the reduction of GO with simultaneous formation of CuS–rGO nanocomposites The CuS–rGO nanocomposites was investigated using powder XRD, FE-SEM, HR-TEM, DRS UV-vis spectroscopy, photoluminescence (PL) measurements, infra-red spectroscopy and photoelectron spectroscopy (XPS) DRS UV-vis measurements of CuS–rGO nanocomposites feature a strong absorption in the range 400–800 nm, which suggests that they have photocatalysis applications Three different composites were prepared with different loadings of rGO to study the effect of loading on methylene blue (MB) dye degradation The photocatalytic properties of the composites were tested in a visible light photoreactor chamber The CuS–rGO nanocomposites were found to exhibit high photocatalytic activities with a maximum efficiency of 9927% after 60 min in a visible source These interesting and enhanced catalytic properties of CuS–rGO-x nanocomposite was further tested for organic contaminant and textile effluents collected from two different sites situated in the Thirupur textile industries, India Results showed the CuS–rGO-x nanocomposite is an efficient photocatalyst

A template-free facile approach for the synthesis of CuS–rGO nanocomposites towards enhanced photocatalytic reduction of organic contaminants and textile effluents

Ta4C3 MXene as supercapacitor electrodes

Magnetic cobalt and nickel ferrites (CoFe2O4 & NiFe2O4) with graphene nanocomposites (CoFe2O4–G & NiFe2O4–G) were synthesized via a solvothermal process and used as an adsorbent for the removal of lead (Pb(II)) and cadmium (Cd(II)) ions from aqueous solution. The as-prepared materials were characterized by field emission-scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), a Brunauer–Emmett–Teller (BET) surface area analyzer, transmission electron microscopy (TEM) and VSM analysis. To probe the nature of the adsorbent, various experiments were investigated like contact time, adsorbent dose, solution pH and temperature were optimized. The isotherm model fitting studies demonstrated that the data fitted the Langmuir isotherm model well. The highest adsorption equilibrium for Pb(II) is 142.8 and 111.1 mg g−1 at pH of 5 and 310 K for CoFe2O4–G & NiFe2O4–G; while for Cd(II) it was 105.26 and 74.62 mg g−1 at pH of 7 and 310 K. The results show that such type of materials could be used for the removal of heavy metal ions from water for environmental applications.

CoFe2O4 and NiFe2O4@graphene adsorbents for heavy metal ions – kinetic and thermodynamic analysis

Porous CoFe2O4 nanoclusters with different concentrations of graphene based composites were synthesized by a simple solvothermal process. The electrochemical properties of prepared CoFe2O4–reduced graphene oxide (rGO) composites were evaluated using polyvinylidene fluoride and Na-alginate as binder materials. The CoFe2O4 + 20% rGO composite with alginate exhibited a high stable capacity of 1040 mA h g−1 at 0.1 C (91 mA g−1) rate with excellent rate capability. The observed enhancement in electrochemical properties of the CoFe2O4 + 20% rGO composite with alginate is due to the high stability and good transportation network while charging–discharging.

Enhanced properties of porous CoFe2O4–reduced graphene oxide composites with alginate binders for Li-ion battery applications

The present study reports the use of one-dimensional carbon wrapped VO2(M) nanofiber (VO2(M)/C) as a cost-effective counter electrode for dye-sensitized solar cells (DSSCs); where M denotes monoclinic crystal system. Uniform short length nanofiber was synthesised by a sol-gel based simple and versatile electrospinning and post carbonization technique. The investigation of nanostructure and morphological analysis were performed by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and transmission electron microscope (TEM) with EDAX. The electrochemical response was comprehensively characterized by cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization. The electrochemical analysis of the VO2(M)/C nanofiber counter electrode exhibits significant electrocatalytic activity towards the reduction of triiodide and low charge transfer resistance at the electrode-electrolyte interface. The DSSCs fabricated with carbon-wrapped VO2(M) nanofiber CE showed high power conversion efficiency of 6.53% under standard test condition of simulated 1SUN illumination at AM1.5 G, which was comparable to the 7.39% observed for conventional thermally decomposed Pt CE based DSSC under same test conditions. This result encourages the next step of modification and use of low-cost VO2(M) as an alternate counter electrode for DSSCs to achieve a substantial efficiency for future energy demand.

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Andrews Nirmala Grace

Papers

A template-free facile approach for the synthesis of CuS–rGO nanocomposites towards enhanced photocatalytic reduction of organic contaminants and textile effluents

Ta4C3 MXene as supercapacitor electrodes

CoFe2O4 and NiFe2O4@graphene adsorbents for heavy metal ions – kinetic and thermodynamic analysis

Enhanced properties of porous CoFe2O4–reduced graphene oxide composites with alginate binders for Li-ion battery applications

Pt-free, low-cost and efficient counter electrode with carbon wrapped VO 2 (M) nanofiber for dye-sensitized solar cells