One step NaBH4 reduction of Pt-Ru-Ni catalysts on different types of carbon supports for direct ethanol fuel cells: Synthesis and characterization

The ternary catalyst Pt₇₅Ru₅Ni₂₀ was conducted on various types of carbon supports including functionalized Vulcan XC-72R (f-CB), functionalized multi-walled carbon nanotubes (f-MWCNT), and mesoporous carbon (PC-Zn-succinic) by sodium borohydride chemical reduction method to improve the ethanol electrooxidation reaction (EOR) for direct ethanol fuel cell (DEFC). It was found that the particle size of the metals on f-MWCNT was 5.20 nm with good particle dispersion. The alloy formation of ternary catalyst was confirmed by XRD and more clearly described by SEM element mapping, which was relevant to the efficiency of the catalysts. Moreover, the mechanism of ethanol electrooxidation reaction based on the surface reaction was more understanding. The activity and stability for ethanol electrooxidation reaction (EOR) were investigated using cyclic voltammetry and chronoamperometry, respectively. The highest activity and stability for EOR were observed from Pt₇₅Ru₅Ni₂₀/f-MWCNT due to a good metal-carbon interaction. Ru and Ni presented in Pt-Ru-Ni alloy improved the activity and stability of ternary catalysts for EOR. Moreover, the reduction of Pt content in ternary catalyst led to the catalyst cost deduction in DEFC.     

Effect of acidity on the formation of silica–chitosan hybrid materials and thermal conductive property

In this study, the formation of silica–chitosan hybrid materials via sol–gel process under pH values of 2–6 were investigated using N₂ sorption analysis, scanning electron microscopy, transmission electron microscopy, thermal analysis and zeta potential analyzer. The hierarchical structure consisting of meso- and macropore was formed when pH value was higher than 2. Mesopores were formed as the interparticle channels of silica nanoparticles aggregates, whereas macropores were the void between the aggregates (clusters). The clusters size was decreased with increasing the pH value, resulting in the increase of the macroporosity. The thermal conductivity of the products was controlled in the range of 0.06 and 0.13 W m⁻¹ K⁻¹ by varying the product porosity between 88 and 69% (pH 6 and pH 2, respectively).     

Effect of pH and chitosan concentration on precipitation and morphology of hierarchical porous silica

Understanding the interaction between chitosan molecules and sodium silicate is one of the principal objectives for the development of new environmentally benign strategies for the synthesis of low-cost porous silica with hierarchical structure. In this work, we have explored two essential factors simultaneously: chitosan/silica ratios (0.1, 0.4, 0.8 and 1.6) and pH values of the mixture (3, 5 and 6). The obtained silica–chitosan composite and the calcined products were investigated by using thermal gravimetric analysis, N₂-physisorption, scanning electron microscopy, and transmission electron microscopy. Rapid precipitation of silica–chitosan composite occurred because of the initial pH values of the chitosan and sodium silicate solutions. The amount of precipitating silica–chitosan composite was increased with increasing pH value of the mixture and chitosan/silica ratios but it did not change with the decrease of pH value of the mixture. The as-synthesized products prepared at pH 3 and 6 showed macroscopic two-solid phases (consisting of silica-rich phase and chitosan-rich phase), while those prepared at pH 5 displayed liquid and solid phases. At pH 3, a unimodal porous structure was found for the calcined products obtained from the silica-rich phase while a hierarchical structure was found for those obtained from the chitosan-rich phase; meanwhile, a hierarchical structure occurred for all calcined products prepared at pH 6. Different hierarchical structures of the silica products could be obtained by changing pH value of the mixture and chitosan/silica ratios.     

Photoinactivation of Sindbis Virus Infectivity Without Inhibition of Membrane Fusion

Photoinactivation of enveloped viruses is commonly associated with damage to fusion proteins and inhibition of membrane fusion capacity. Here we show that photobleaching of Sindbis virus labeled with the membrane localized dye, R18 (octadecyl rhodamine B) causes a dramatic loss of infectivity without observable changes in low-pH triggered membrane fusion to liposomes. Sindbis labeled with DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate) also maintains low-pH triggered membrane fusion capacity, but in contrast to R18, extensive photobleaching of DiI-labeled virus has little effect on infectivity. Electrophoretic gel analysis suggests no cross-linking of viral fusion proteins following photobleaching of dye-labeled Sindbis. These observations have implications for live-cell, single particle tracking studies of dye-labeled Sindbis virus. Our observations suggest that R18 and DiI have different propensities for spontaneous flip-flop in lipid bilayers.     

Size control of nanostructured silica using chitosan template and fractal geometry: effect of chitosan/silica ratio and aging temperature

The uses of low cost, renewable, environmentally friendly chitosan biopolymer as the structural template to control the size of silica particles in the range of nanometer scales are attractive for their practical industrial applications. In this paper, the nanostructured silica was synthesized using sodium silicate as the silica source and chitosan as the template under mild conditions. Effects of chitosan/silica ratio and aging temperature on the formation and the control of nanostructured silica was investigated by using thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), N₂-sorption measurement, and transmission electron microscopy (TEM). It was found that the silica products were composed of the aggregates of primary silica nanoparticles and nanostructured silica units. At low aging temperature, the size of nanostructured silica was decreased when increasing the chitosan/silica ratio from 0.1 to 0.4. In contrast, the reverse trend was observed at the chitosan/silica ratio of higher than 0.4. The increase of aging temperature led to the formation of larger primary silica nanoparticles and nanostructured silica, and also promoted the formation of silica/chitosan composites. The fractal dimension calculated using modified FHH method found the linear correlation at two different regimes which might reflect the aggregates of silica products at different length scales.     

Production of energetic electrons during magnetic reconnection

The production of energetic electrons during magnetic reconnection is explored with full particle simulations and analytic analysis. Density cavities generated along separatrices bounding growing magnetic islands support parallel electric fields that act as plasma accelerators. Electrons because of their low mass are fast enough to make multiple passes through these acceleration cavities and are therefore capable of reaching relativistic energies.