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chemistry (3)

Boiling Superconductivity...

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Under pressure: calculated structure of lithium magnesium hydride. Lithium atoms appear in green, magnesium in blue and hydrogen in red. (Courtesy: Ying Sun et al/Phys. Rev. Lett.)

 

Topics: Chemistry, Materials Science, Nanotechnology, Superconductors


A material that remains a superconductor when heated to the boiling point of water has been predicted by physicists in China. Hanyu Liu, Yanming Ma and colleagues at Jilin University have calculated that lithium magnesium hydride will superconduct at temperatures as high as 473 K (200 °C).

The catch is that the hydrogen-rich material must be crushed at 250 GPa, which is on par with pressures at the center of the Earth. While such a pressure could be achieved in the lab, it would be very difficult to perform an experiment to verify the prediction. The team’s research could, however, lead to the discovery of more practical high-temperature superconductors.

Superconductors are materials that, when cooled below a critical temperature, will conduct electricity with zero resistance. Most superconductors need to be chilled to very low temperatures, so the holy grail of superconductivity research is to find a substance that will superconduct at room temperature. This would result in lossless electricity transmission and boost technologies that rely on the generation or detection of magnetic fields.

 

Superconductivity at the boiling temperature of water is possible, say physicists
Hamish Johnston, Physics World

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Nanocones...

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A carbon nanocone includes nitrogen atoms around the periphery to improve the material’s solubility. Carbon atoms are shown in gray; hydrogen in white; nitrogen in blue; and oxygen in red.

 

Topics: Applied Physics, Chemistry, Graphene, Nanotechnology


Graphene, buckyballs, and carbon nanotubes now have a new family member, the nanocone, adding to the types of all-carbon nanostructures with remarkable electronic and optical characteristics and bringing its own promising properties. (J. Am. Chem. Soc., 2019, DOI: 10.1021/jacs.9b06617) Such molecules could be useful for developing efficient organic solar cells or as sensor molecules.

Organic chemist Frank Würthner and postdoctoral researcher Kazutaka Shoyama of the University of Würzburg came up with the method for synthesizing the nanocones, which are 1.68 nm in diameter and 0.432 nm tall. A five-atom ring of carbons forms the cone’s tip. The team used a cross-coupling annulation cascade to add hexagons around the edges of the ring until the molecule grew to 80 carbons. The team added five nitrogen atoms around the periphery of the cone, increasing the crystal’s solubility.

 

Nanocones extend the graphene toolbox, Neil Savage, Chemical & Engineering News

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Cyclocarbon...

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From left to right, precursor molecule C24O6, intermediates C22O4 and C20O2 and the final product cyclo [18]carbon C18 created on surface by dissociating CO masking groups using atom manipulation. The bottom row shows atomic force microscopy (AFM) data using a CO functionalized tip. Credit: IBM Research

 

Topics: Applied Physics, Atomic Force Microscopy, Chemistry, Nanotechnology, Research


A team of researchers from Oxford University and IBM Research has for the first time successfully synthesized the ring-shaped multi-carbon compound cyclocarbon. In their paper published in the journal Science, the group describes the process they used and what they learned about the bonds that hold a cyclocarbon together.

Carbon is one of the most abundant elements, and has been found to exist in many forms, including diamonds and graphene. The researchers with this new effort note that much research has been conducted into the more familiar forms (allotropes) how they are bonded. They further note that less well-known types of carbon have not received nearly as much attention. One of these, called cyclocarbon, has even been the topic of debate. Are the two-neighbor forms bonded by the same length bonds, or are there alternating bonds of shorter and longer lengths? The answer to this question has been difficult to find due to the high reactivity of such forms. The researchers with this new effort set themselves the task of finding the answer once and for all.

The team's approach involved creating a precursor molecule and then whittling it down to the desired form. To that end, they used atomic force microscopy to create linear lines of carbon atoms atop a copper substrate that was covered with salt to prevent the carbon atoms from bonding with the subsurface. They then joined the lines of atoms to form the carbon oxide precursor C24O6, a triangle-shaped form. Next, the team applied high voltage through the AFM to shear off one of the corners of the triangle, resulting in a C22O4 form. They then did the same with the other two corners. The result was a C18 ring—an 18-atom cyclocarbon. After creating the ring, the researchers found that the bonds holding it together were the alternating long- and short-type bonds that had been previously suggested.

 

Ring-shaped multi-carbon compound cyclocarbon synthesized, Bob Yirka , Phys.org

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