Tuesday, May 20, 2008

"NANOTECH: makes radioactive sensors obsolete"

"Green" smoke-alarm ionizers using field-emission from nanotubes instead of radioactive isotopes could eliminate a source of dirty-bomb material, according to Applied Nanotech Inc. (Austin, Texas) and Sionex Corp. (Bedford, Mass.) which have funding from Homeland Security to produce a small, safe, high-performance sensor using electron field emission from carbon nanotube arrays instead the ionizing alpha rays from radioactive isotopes. Many American households have as much as a milligram of radioactive americium-241 in the various smoke alarms and other gas-phase detectors found there. About a fifth of a gram of americium is used to ionize the air inside a smoke detector. But just one gram of americium is dangerous for people to handle; dekagrams to hectograms are enough for "dirty" bombs, and kilograms could be used to make a nuclear bomb. Instead of seeding our land-fills with radioactive materials like nickel-63 and americium-241, which have half-lives of 100 and 432 years, respectively, the Applied Nanotech and Sionix joint-development effort aims to provide a safe, inexpensive, high-performance alternative method of ionizing samples by using carbon nanotube emitters integrated into air-flow passages ahead of a differential mobility spectrometer. Applied Nanotech and Sionex claim to have proven in principle that carbon nanotube emitters can perform all the necessary ionization and identification steps without the use of radioactive materials.