Weak mismatch epitaxy and structural Feedback in graphene growth on copper foil

Graphene growth by low-pressure chemical vapor deposition on low cost copper foils shows great promise for large scale applications. It is known that the local crystallography of the foil influences the graphene growth rate. Here we find an epitaxial relationship between graphene and copper foil. Interfacial restructuring between graphene and copper drives the formation of (n10) facets on what is otherwise a mostly Cu(100) surface, and the facets in turn influence the graphene orientations from the onset of growth. Angle resolved photoemission shows that the electronic structure of the graphene is decoupled from the copper indicating a weak interaction between them. Despite this, two preferred orientations of graphene are found, ±8° from the Cu[010] direction, creating a non-uniform distribution of graphene grain boundary misorientation angles. Comparison with the model system of graphene growth on single crystal Cu(110) indicates that this orientational alignment is due to mismatch epitaxy. Despite the differences in symmetry the orientation of the graphene is defined by that of the copper. We expect these observations to not only have importance for controlling and understanding the growth process for graphene on copper, but also to have wider implications for the growth of two-dimensional materials on low cost metal substrates.      

Multiply Methyl-Branched Fatty Acids and Diacids in the Polar Lipids of a Microaerophilic Subsurface Microbial Community

A previously unreported series of di- and tri-methylated fatty acids, as well as saturated and monounsaturated diacids were identified in polar lipids isolated from environmental subsurface sediment samples. Mechanisms are proposed for their formation, but their origin and role in cell membranes remains unknown.     

Torsion fatigue response of self-healing poly(dimethylsiloxane) elastomers

Incorporating self-healing functionality in a polysiloxane elastomer successfully retards the growth of fatigue cracks under torsional fatigue loading. The fully in situ self-healing material consists of a microencapsulated vinyl-terminated poly(dimethylsiloxane) resin containing platinum catalyst compounds and a microencapsulated initiator (methylhydrosiloxane), embedded in a poly(dimethylsiloxane) elastomer matrix. A torsion fatigue test protocol is adopted to assess the self-healing performance of two different elastomeric matrices. Significant recovery of torsional stiffness occurs after approximately 5 h, the time required to achieve a measurable degree of cure of the healing agents. Total fatigue crack growth in a self-healing specimen is reduced by 24% in comparison to relevant controls. The retardation of growing fatigue cracks is attributed, in part, to a sliding-crack-closure mechanism, where polymerized healing agent shields the crack tip from the applied far-field stress.     

Effect of Electrode Microstructure on the Sensitivity and Response Time of Potentiometric NOX Sensors

Nanometric La₂CuO₄ was synthesized with the Pechini method, co-precipitation, and two variations of the auto-ignition technique for fabricating NO _X sensor electrodes. The auto-ignition technique produced the most phase-pure powder with the smallest particle size and the largest specific surface area. The sensor electrodes were subjected to various thermal treatments resulting in a variety of electrode grain sizes and distributions. The response times of the sensors were exponentially dependent on electrode grain size. Sensors with fine-grained electrodes were able to produce a steady-state and consistent voltage at lower temperatures; improving their response sensitivity. Sensors fabricated with powders synthesized through the auto-ignition route responded quickly, sensitively, and reproducibility to NO.     

Oxidative stability of sunflower oil bodies

This study investigates the oxidative stability of sunflower oil body suspensions (10 wt‐% lipid). Two washed suspensions of oil bodies were evaluated over 8 days at three temperatures (5, 25 and 45 °C) against three comparable sunflower oil emulsions stabilized with dodecyltrimethylammonium bromide (DTAB), polyoxyethylene‐sorbitan monolaurate (Tween 20) and sodium dodecyl sulfate (SDS) (17 mM). The development of oxidation was monitored by measuring the presence of lipid hydroperoxides and the formation of hexanal. Lipid hydroperoxide concentrations in the DTAB, SDS and Tween 20 emulsions were consistently higher than in the oil body suspensions; furthermore, hexanal formation was not detected in the oil body emulsions, whereas hexanal was present in the headspace of the formulated emulsions. The reasons for the extended resistance to oxidation of the oil body suspensions are hypothesized to be due to the presence of residual seed proteins in the continuous phase and the presence of a strongly stabilized lipid‐water interface.