Materials chemistry

Scientists create fifth form of carbon

Scientists create fifth form of carbon

Magnetic carbon 'nanofoam' could find medical applications.

Researchers have created a new form of carbon: a spongy solid that is extremely lightweight and, unusually, attracted to magnets. The foam could one day help treat cancer and enhance brain scans, say the inventors.

Scientists create fifth form of carbon, Giles, Jim , news@nature, 3/2004, (2004)

Ig Nobel Prize for chemistry 2009

The 2009 chemistry prize goes to Javier Morales, Miguel Apátiga, and Victor M. Castaño (Universidad Nacional Autónoma de México) for creating diamonds from liquid — specifically from tequila.

Abstract from "Growth of Diamond Films from Tequila," Javier Morales, Miguel Apatiga and Victor M. Castano, 2008, arXiv:0806.1485. Diamond thin films were growth using Tequila as precursor by Pulsed Liquid Injection Chemical Vapor Deposition (PLI-CVD) onto both silicon (100) and stainless steel 304 at 850 C. The diamond films were characterized by Scanning Electron Microscopy (SEM) and Raman spectroscopy. The spherical crystallites (100 to 400 nm) show the characteristic 1332 cm-1 Raman band of diamond.

Hydrogen oxygen alloy

Researchers at the Carnegie Institution of Washington (Washington DC, USA) have managed to make a remarkable alloy of hydrogen and oxygen from water! They used X-rays to dissociate water at high pressure to form a solid mixture, that is, an alloy, of molecular oxygen (O2) and molecular hydrogen (H2).

The researchers placed some water under an extremely high pressure, about 170,000 atmospheres (17 Gigapascals), using a diamond anvil and then beamed high-energy X-rays at the water. Nearly all the water molecules split and reformed as a solid alloy of O2 and H2. The X-rays are key to cleaving the O—H bonds in water. Without it, the water remains as a high-pressure form of ice known as ice VII. Ice VII is one of at least 15 kinds of ice that exist under various high pressure and variable temperature conditions.

Russell Hemley of the Carnegie Institution of Washington said "we managed to hit on just the right level of X-ray energy input. Any higher, and the radiation tends to pass right through the sample. Any lower, and the radiation is largely absorbed by the diamonds in our pressure apparatus."

The researchers subjected the alloy to a range of pressures and temperatures, and also bombardment with X-ray and laser radiation. Provided the alloy is kept at about 10,000 times atmospheric pressure at sea level (1 Gigapascal), it withstands the treatment. Although clearly a crystalline solid, more experiments are needed to determine the alloy's precise crystal structure.

"The new radiation chemistry at high pressure was surprising," said Wendy Mao of the Los Alamos National Laboratory in the USA. "The new alloy containing the incompatible oxygen and hydrogen molecules will be a highly energetic material." An explosive alloy!

Flexible nanomembranes

Workers at The University of Wisconsin-Madison in the USA have managed to release thin membranes of semiconductors from a substrate and transfer them to new surfaces. The freed membranes which are just tens of nanometers thick retain all the properties of silicon in wafer form but the nanomembranes are flexible. By varying the thicknesses of the silicon and silicon-germanium layers composing them, membrane shapes are possible ranging from flat to curved to tubular.

Potential applications include flexible electronic devices, faster transistors, nano-size photonic crystals that steer light, and lightweight sensors for detecting toxins in the environment or biological events in cells.

The scientists made a three-layer nanomembrane composed of a thin silicon-germanium layer sandwiched between two silicon layers of similar thinness. The membrane sat upon a silicon dioxide layer in a silicon-on-insulator substrate. The nanomembranes may be etched away from the oxide layer with hydrofluoric acid.

Although the Wisconsin team grew their nanomembranes on silicon-on-insulator substrates, the method should apply to many substances beyond semiconductors, such as ferroelectric and piezoelectric materials. The key requirement is a layer, like an oxide, that can be removed to free the nanomembranes.1

NanoFoam

Nature reports that a new form of carbon was created when physicists at the Australian National University in bombarded a carbon target with a laser. As the carbon reached temperatures of around 10000 °C, it formed an intersecting web of carbon tubes called a 'nanofoam'. This is said to be a fifth form of carbon known after graphite, diamond, buckminsterfullerenes (buckyballs), and nanotubes. The foam is attracted to magnets. This may lead to new uses.1

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