Oak Ridge National Laboratory

About: Oak Ridge National Laboratory is a facility organization based out in Oak Ridge, Tennessee, United States. It is known for research contribution in the topics: Neutron & Ion. The organization has 31868 authors who have published 73724 publications receiving 2633689 citations. The organization is also known as: ORNL.

Water desalination using nanoporous single-layer graphene

Abstract: An oxygen plasma etching process can be used to create a nanoporous graphene layer that can efficiently desalinate water.

Nanoscale nickel oxide/nickel heterostructures for active hydrogen evolution electrocatalysis

Abstract: There is ongoing research into new electrocatalysts for hydrogen production from water splitting. Here, the authors report the electrocatalytic performance of nickel/nickel oxide heterostructures on carbon nanotubes, and are able to assemble a water electrolyzer operated by a single-cell 1.5 V battery.

Optical generation of excitonic valley coherence in monolayer WSe2

Abstract: As a consequence of degeneracies arising from crystal symmetries, it is possible for electron states at band-edges ('valleys') to have additional spin-like quantum numbers. An important question is whether coherent manipulation can be performed on such valley pseudospins, analogous to that implemented using true spin, in the quest for quantum technologies. Here, we show that valley coherence can be generated and detected. Because excitons in a single valley emit circularly polarized photons, linear polarization can only be generated through recombination of an exciton in a coherent superposition of the two valley states. Using monolayer semiconductor WSe2 devices, we first establish the circularly polarized optical selection rules for addressing individual valley excitons and trions. We then demonstrate coherence between valley excitons through the observation of linearly polarized luminescence, whose orientation coincides with that of the linearly polarized excitation, for any given polarization angle. In contrast, the corresponding photoluminescence from trions is not observed to be linearly polarized, consistent with the expectation that the emitted photon polarization is entangled with valley pseudospin. The ability to address coherence, in addition to valley polarization, is a step forward towards achieving quantum manipulation of the valley index necessary for coherent valleytronics.

The development and current status of perennial rhizomatous grasses as energy crops in the US and Europe

Abstract: Perennial grasses display many beneficial attributes as energy crops, and there has been increasing interest in their use in the US and Europe since the mid-1980s. In the US, the Herbaceous Energy Crops Research Program (HECP), funded by the US Department of Energy (DOE), was established in 1984. After evaluating 35 potential herbaceous crops of which 18 were perennial grasses it was concluded that switchgrass (Panicum virgatum) was the native perennial grass which showed the greatest potential. In 1991, the DOE's Bioenergy Feedstock Development Program (BFDP), which evolved from the HECP, decided to focus research on a “model” crop system and to concentrate research resources on switchgrass, in order to rapidly attain its maximal output as a biomass crop. In Europe, about 20 perennial grasses have been tested and four perennial rhizomatous grasses (PRG), namely miscanthus (Miscanthus spp.), reed canarygrass (Phalaris arundinacea), giant reed (Arundo donax) and switchgrass (Panicum virgatum) were chosen for more extensive research programs. Reed canarygrass and giant reed are grasses with the C3 photosynthetic pathway, and are native to Europe. Miscanthus, which originated in Southeast Asia, and switchgrass, native to North America, are both C4 grasses. These four grasses differ in their ecological/climatic demands, their yield potentials, biomass characteristics and crop management requirements. Efficient production of bioenergy from such perennial grasses requires the choice of the most appropriate grass species for the given ecological/climatic conditions. In temperate and warm regions, C4 grasses outyield C3 grasses due to their more efficient photosynthetic pathway. However, the further north perennial grasses are planted, the more likely cool season grasses are to yield more than warm season grasses. Low winter temperatures and short vegetation periods are major limits to the growth of C4 grasses in northern Europe. With increasing temperatures towards central and southern Europe, the productivity of C4 grasses and therefore their biomass yields and competitiveness increase. Since breeding of and research on perennial rhizomatous grasses (PRG) is comparatively recent, there is still a significant need for further development. Some of the given limitations, like insufficient biomass quality or the need for adaption to certain ecological/climatic zones, may be overcome by breeding varieties especially for biomass production. Furthermore, sure and cost-effective establishment methods for some of the grasses, and effective crop production and harvest methods, have yet to be developed. This review summarizes the experience with selecting perennial grasses for bioenergy production in both the US and Europe, and gives an overview of the characteristics and requirements of the four most investigated perennial rhizomatous grasses; switchgrass, miscanthus, reed canarygrass and giant reed.