Chemistry news, articles, and more

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

Osmium tetroxide bomb

The BBC report that UK and US intelligence agents foiled a chemical bomb plot in the UK. Apparently the plot was involves detonating a combination of explosive and osmium tetraoxide, [OsO4].

The target is thought to be in crowded areas, possibly within a confined area, perhaps in London. The plotters apparently did not obtain any of the tetroxide, perhaps because it costs around UK pounds 100 per gram!

Not totally clear why osmium tetroxide was chosen. Certainly it is unpleasant, corrosive, toxic, irritant, volatile, and a stain. It reacts with alkenes - hence the staining properties, and must be handled properly in the lab.

Superconductivity in diamond

Workers in Russia and Los Alamos, USA report in Nature1 superconductivity in boron-doped diamond synthesized at high pressure (nearly 100,000 atmospheres) and temperature (2500-2800 K). Electrical resistivity, magnetic susceptibility, specific heat and field-dependent resistance measurements show that boron-doped diamond (carbon) is a bulk, type-II superconductor below the superconducting transition temperature Tc 4 K.

Boron has one less electron than carbon and, because of its small atomic radius, is relatively easily incorporated into diamond. The boron acts as a charge acceptor and the resulting diamond is effectively hole-doped.

Drink milk!

Virginia Tech (USA) researchers found that calcium intake among US adolescents has remained constant, if inadequate, since the 1970s and does not appear to be linked to soft drink consumption. Milk consumption among adolescent girls is low, with this group falling far below recommended dietary levels of calcium consumption. So drink some milk!

Conclusion: carbonated soft drink consumption among adolescent girls is modest and does not appear to be linked to decreased calcium intake. The analyses in this paper show that creative effective, efficient, and targeted policies should be considered to help adolescent girls increase calcium intake. Making low-fat milk products, flavored milks, calcium-fortified beverages and foods more attractive and available will help encourage girls to consume more of this important mineral. When adequate calcium intake is not achieved through foods, health professionals should consider recommending calcium supplements.

Self-cleaning titania nanotube hydrogen sensors

The Science Blog reports that researchers at Penn State in the USA are developing self-cleaning titania nanotube hydrogen sensors. The hydrogen sensors are titania nanotubes coated with a discontinuous layer of palladium. Hydrogen sensors are widely used in the chemical, petroleum and semiconductor industries. They are also used as diagnostic tools to monitor certain types of bacterial infections.

"The photocatalytic properties of titania nanotubes are so large - a factor of 100 times greater than any other form of titania - that sensor contaminants are efficiently removed with exposure to ultraviolet light, so that the sensors effectively recover or retain their original hydrogen sensitivity in real world application"

"By doping the titania nanotubes with trace amounts of different metals such as tin, gold, silver, copper, niobium and others, a wide variety of chemical sensors can be made. This doping does not alter the photocatalytic properties of the titania nanotubes" says Dr. Craig A. Grimes, associate professor of Electrical Engineering and Materials Science and Engineering.1

Carbon nanotube emits light

The U.S. Department of Energy's Brookhaven National Laboratory reports that scientists at the US Brookhaven National Laboratory and the IBM T.J. Watson Research Center caused an individual carbon nanotube to emit light for the first time. This may have significance for many of the proposed applications for carbon nanotubes including in electronics and photonics.

The light emission is the result of a process called "electron-hole recombination." By running an electric current through a carbon nanotube - a long, hollow cylindrical molecule that is only one and a half nanometers (a billionth of a meter) in diameter - negatively charged electrons in the nanotube molecule combine with positively charged "holes," which are locations in the molecule where electrons are missing. When an electron fills a hole, it emits a photon - a tiny burst of light.

"We produced infrared light by applying voltages to a specific type of nanotube such that many electrons and holes end up in the nanotube, where they combine. This makes the nanotube the world's smallest electrically-controllable light emitter," said James Misewich, a materials scientist at Brookhaven. "It's an exciting result, and my colleagues and I plan to continue studying the effect to determine the mechanisms behind it. For example, we hope to understand how to make the nanotubes emit other types of light, such as visible light, and how to increase the efficiency of the emission." Carbon nanotubes do not yet have any mainstream practical applications, but researchers are investigating ways to use them in flat-panel displays, such as televisions and computer monitors, or as reinforcements in building materials, due to their exceptional mechanical strength. Misewich also suggested that, if additional research leads to an increased efficiency of nanotube light emission, the nanotubes could possibly be used in lighting applications.

Tags:

Water on Mars

A NASA press release claims that the Opportunity rover "has demonstrated some rocks on Mars probably formed as deposits at the bottom of a body of gently flowing saltwater." "Bedding patterns in some finely layered rocks indicate the sand-sized grains of sediment that eventually bonded together were shaped into ripples by water at least five centimeters (two inches) deep, possibly much deeper, and flowing at a speed of 10 to 50 centimeters (four to 20 inches) per second," said Dr. John Grotzinger, rover science-team member from the Massachusetts Institute of Technology, Cambridge, Mass.

Special interests threat to ozone layer?

The BBC report that special interests in a number of developed countries wish to to be allowed to continue using a bromine containing gas, methyl bromide, for various purposes such as crop fumigation. Methyl bromide is known to destroy ozone, O3, (an allotrope of oxygen, O2) and this is being debated at an international meeting in Canada. The Montreal Protocol does allow continued use of ozone-destroying gases for purposes agreed to be "critical", but is this really critical?

Illegal uranium mining?

The BBC are reporting possible illegal mining of uranium at a mine in the Democratic Republic of Congo. The government states the mine was shut but a BBC correspondent cliams 6,000 illegal miners work the Shinkolobwe mine. The International Atomic Energy Agency is said to be very concerned. The BBC state the uranium is processed nearby and delivered illegally to the world market via Zambia.

New elements 113 (ununtrium) and 115 (ununpentium)

It is claimed that recent experimental results involving the bomabardment of americium-243 with calcium-48 ions are consistent with the formation in the laboratory of a few atoms of elements 113 and 115. In experiments conducted at the JINR U400 cyclotron with the Dubna gas-filled separator between July 14 and Aug. 10, 2003, atomic decay patterns were observed that are said to confirm the existence of element 115 and element 113. In these decay chains, element 113 is produced via the alpha decay of element 115.1

The news has been picked up in a number of online sources including Nature2 and elsewhere.

WebElements: the periodic table on the WWW [http://www.webelements.com/]

Copyright 1993-2011 Mark Winter [The University of Sheffield and WebElements Ltd, UK]. All rights reserved.