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
- 1. Elastically relaxed free-standing strained-silicon nanomembranes,
, Nature Materials, 5/2006, Volume 5, Issue 5, p.388 - 393, (2006)
Can you make your name, or any other word come to that, from element symbols? Find out using this script: Viren.org
The BBC is airing some "periodic tales" on Radio 4. Familiar Radio 4 voices introduce elements from the Periodic Table and the unique roles they play in human existence - with a little help from the irreverent Tom Lehrer. Listen to these ten elements:
- Krypton: Heidli Nicklaus on the Superman element, krypton
- Helium: Brian Perkins dramatises the effects of Helium
- Silver: Trevor Harrison (Eddie Grundy in the Archers) finds some unusual properties of Silver
- Cobalt: Hedli Nicklaus (Cathy Perks) takes on the goblin element of cobalt
- Selenium: Carole Boyd (The Archers' Linda Snell) unearths selenium
- Oxygen: Brian Perkins bravely dramatises the effects of oxygen
- Arsenic: Charlotte Green takes on the deadly history of arsenic
- Mercury: Carole Boyd (Linda Snell) reflects on mercury, the poisonous liquid metal
- Iodine: Charlotte Green on the discovery of iodine's essential place in brain development
- Nickel: Trevor Harrison reveals that the space station Mir is largely made of nickel
[[Note added Dec 2009: sadly these recordings no longer exist on the BBC site. I did offer to host them here but no luck]]
Nobel laureate Richard Smalley, the Rice University professor who helped discover buckyballs (buckminsterfullerene, C60, the football (soccer) ball shaped form of carbon, died at the age of 62. Richard Smalley shared the 1996 Nobel Prize in chemistry with Sir Harold Kroto (Sussex) and Robert Curl (also Rice) for the identification of the new form of carbon known as buckminsterfullerene because of its similarity to Buckminster Fuller's geodesic domes. The Richard E. Smalley Institute for Nanoscale Science and Technology continues to champion the efforts of Smalley through research, educational and community programs, corporate partnerships, and government relations.
Lands, rivers and methane springs: latest images of Titan. Titan's atmosphere is mostly nitrogen but there is also methane and many other organic compounds.
This Cassini-Huygens article ponders the abundance of methane on Titan. Titan's atmosphere is mostly nitrogen but there are also methane and many other organic compounds. On Earth, life refreshes the methane supply as it is a by-product of metabolism. This is not likely to be the source of methane on Titan but if, as on Earth, sunlight is continuously destroying methane, how is methane getting into Titan's atmosphere?
Scientists at NASA's Johnson Space Center in Houston have shipped pieces of the Genesis polished aluminium collector to researchers at Washington University in St. Louis, marking the first distribution of a Genesis scientific sample from JSC since the science canister arrived there Oct. 4, 2004. The sample, the first to be allocated for Genesis early science analysis, may hold important evidence about the overall composition of the sun.
While much of the solar wind is hydrogen, it is hoped that Genesis captured samples of many elements in the periodic table. An analysis of these elements will help to determine the sun's composition in detail. Several important Genesis science objectives will be investigated as part of the Early Science Return, including studies of noble gas isotopes in bulk solar wind and nitrogen isotopes.
GoElemental! is an interactive open-air project in the city of Bath in the UK based around the periodic table of elements 6pm - 9pm, from the 17-19th December 2004. It is at St Michael's Square, opposite the Little Theatre Cinema, Bath, BA1 1SP, UK.
The work takes the format of a three-day interactive animation, to be projected onto a wall opposite the Little Cinema in St Michael's Square. Using their mobile phones, the audience will be able to text an element's name to a number provided at the show to find out where that element is used and what it does. On receiving the request, the projection will change and show a humorous or exciting animation of their chosen element.
GoElemental intends to whet people's curiosity about the scientific chemical elements, and introduce them to their everyday uses in an accessible and fun way. The idea behind the project is to spark a sense of wonder about the world around us.
GoElemental has been developed by Kerry Bradshaw, an MA student at Bath Spa University college, in collaboration with James Grierson from the Science department at Oxford Community school, and Peter Bradshaw, based in San Francisco, USA.
IUPAC have made a provisional recommendation about the name for element 111. To quote: "A joint IUPAC-IUPAP Working Party (JWP) has confirmed the discovery of element number 111 and this by the collaboration of Hofmann et al. from the Gesellschaft für Schwerionenforschung mbH (GSI) in Darmstadt, Germany. In accord with IUPAC procedures, the discoverers have proposed a name and symbol for the element. The Inorganic Chemistry Division Committee now recommends this proposal for acceptance. The proposed name is roentgenium with symbol Rg.
This proposal lies within the long established tradition of naming elements to honour famous scientists. Wilhelm Conrad Röntgen discovered X-rays in 1895."
I've taken the liberty of reproducing a CHMED-L post from Eric Scerri about hydrogen's position in the periodic table.
The position of hydrogen in the periodic system is a much debated topic. Authors have suggested groups I, VII and even IV over the years. Others opt from removing H from the main body of the table, along with He. The official journal of IUPAC, called Chemistry International, has been running some articles and comments on this issue.