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Metallic non-metals

Continue reading “Water transformed into shiny, golden metal” »

Nitrogen-vacancy (NV) center in diamond is a promising quantum sensor with remarkably versatile sensing capabilities. While scanning NV magnetometry is well-established, NV electrometry has been so far limited to bulk diamonds. Here we demonstrate imaging external alternating (AC) and direct (DC) electric fields with a single NV at the apex of a diamond scanning tip under ambient conditions. A strong electric field screening effect is observed at low frequencies. We quantitatively measure its frequency dependence and overcome this screening by mechanically oscillating the tip for imaging DC fields. Our scanning NV electrometry achieved an AC E-field sensitivity of 26‰mV‰Î¼m ˆ’1‰Hz ˆ’1/2, a DC E-field gradient sensitivity of 2‰V‰Î¼m ˆ’2‰Hz ˆ’1/2, and sub-100‰nm resolution limited by the NV-sample distance. Our work represents an important step toward building a scanning-probe-based multimodal quantum sensing platform.

A research group led by Prof. WU Kaifeng from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS), in collaboration with Dr. Peter C. Sercel from the Center for Hybrid Organic Inorganic Semiconductors for Energy, recently reported the utilization of lattice distortion in lead halide perovskite quantum dots (QDs) to control their exciton fine structure.

The study was published in Nature Materials (“Lattice distortion inducing exciton splitting and coherent quantum beating in CsPbI 3 perovskite quantum dots”).

Lattice distortion of perovskite quantum dots induces coherent quantum beating. (Image: DICP)

Assistant Professor Ariel Furst and her colleagues are looking to DNA to help guide the process.

Carbon dioxide (CO₂) is a major contributor to climate change and a significant product of many human activities, notably industrial manufacturing. A major goal in the energy field has been to chemically convert emitted CO₂ into valuable chemicals or fuels. But while CO₂ is available in abundance, it has not yet been widely used to generate value-added products. Why not?

The reason is that CO₂ molecules are highly stable and therefore not prone to being chemically converted to a different form.

Continue reading “Turning carbon dioxide into valuable products” »

A relatively new kind of semiconductor, layered atop a mirror-like structure, can mimic the way that leaves move energy from the sun over relatively long distances before using it to fuel chemical reactions. The approach may one day improve the efficiency of solar cells.

“Energy transport is one of the crucial steps for solar energy harvesting and conversion in solar cells,” said Bin Liu, a postdoctoral researcher in electrical and computer engineering and first author of the study in the journal Optica.

“We created a structure that can support hybrid light-matter mixture states, enabling efficient and exceptionally long-range energy transport.”

Hydrogen (H 2) is currently discussed as an ideal energy carrier in a world requiring renewable energies. Hydrogen has the highest gravimetric energy density of all chemical fuels (141 MJ/kg), which is three times higher than gasoline (46 MJ/kg). However, its low volumetric density restricts its widespread use in transportation applications —as current storage options require a lot of space.

At ambient temperature, hydrogen is a gas, and one kilogram of hydrogen occupies a volume of 12,000 liters (12 cubic meters). In fuel-cell vehicles, hydrogen is stored under a very high pressure of 700 times the atmospheric pressure, which reduces the volume to 25 liters per kilogram of H 2.

Liquid hydrogen shows a higher density resulting in 14 liters per kilogram, but it requires extremely low temperatures since the boiling point of hydrogen is minus 253 °C.

With gas prices soaring and food costs pinching family budgets, an interdisciplinary team of researchers at WPI is looking at ways to use food waste to make a renewable and more affordable fuel replacement for oil-based diesel. The work, led by Chemical Engineering Professor Michael Timko, is detailed in a new paper in the journal iScience.

“By creating a biodiesel through this method, we’ve shown that we can bring the price of gas down to $1.10 per gallon, and potentially even lower,” said Timko.

The Environmental Protection Agency estimates that, in 2018 in the United States, about 81% of household food—about 20 tons—ended up in landfills or combustion facilities. Food waste is also a major contributor to climate change: once it’s placed in landfills, it emits methane, a greenhouse gas.

Squeaky, cloudy or spherical—electron orbitals show where and how electrons move around atomic nuclei and molecules. In modern chemistry and physics, they have proven to be a useful model for quantum mechanical description and prediction of chemical reactions. Only if the orbitals match in space and energy can they be combined—this is what happens when two substances react with each other chemically. In addition, there is another condition that must be met, as researchers at Forschungszentrum Jülich and the University of Graz have now discovered: The course of chemical reactions also appears to be dependent on the orbital distribution in momentum space. The results were published in the journal Nature Communications.

Chemical reactions are ultimately nothing more than the formation and breakdown of electron bonds, which can also be described as orbitals. The so-called molecular orbital theory thus makes it possible to predict the path of chemical reactions. Chemists Kenichi Fukui and Roald Hoffmann received the Nobel Prize in 1981 for greatly simplifying the method, which led to its widespread use and application.

“Usually, the energy and location of electrons are analyzed. However, using the photoemission tomography method, we looked at the momentum distribution of the orbitals,” explains Dr. Serguei Soubatch. Together with his colleagues at the Peter Grünberg Institute (PGI-3) in Jülich and the University of Graz in Austria, he adsorbed various types of molecules on metal surfaces in a series of experiments and mapped the measured momentum in the so-called momentum space.

Now, as a new generation of nuclear reactor designers develop advanced molten salt reactor concepts as an alternative for providing reliable, sustainable, carbon-free power, the need for radiation chemistry has never been greater.

To meet that need, Idaho National Laboratory’s Center for Radiation Chemistry Research has developed a capability that supports the nuclear energy industry by researching radiation-induced effects in advanced reactors, fuels, coolants, materials and fuel recycling technologies while also training the next generation of radiation chemists.