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nanotimes News in Brief
Working in collaboration with the RhineMain Poly- technic, materials scientists at the TU Darmstadt, Germany, have developed an extremely sensitive explosives sensor that is capable of detecting even slight traces of the high-explosive chemical compound pentaerythritol tetranitrate (PETN). Terrorists had employed PETN in several attacks on commercial aircraft.
Explaining the new type of explosive detector’s operation, Dipl.-Ing. Mario Boehme stated that, “If a PETN-molecule enters the sensor’s nanotube, the nitro groups characteristic of PETN adhere to its surface and change its electrical conductivity, and that change may be detected by electronic instru- mentation.”
11-11/12 :: November/December 2011
team of scientists from the Vienna University of Technology (Austria) and the University of Calcut- ta (India) investigated this phenomenon – and the new effect could be explained in computer simu- lations. In a crossover from large crystals to smaller crystals, the distribution of the electrons changes, and so does their energy. This, in turn, changes the electrical and magnetic properties of the crystal. “The phenomenon of quantum entanglement plays a very important role here”, says Professor Karsten Held. “We cannot think of the electrons as classical particles, moving independently of each other, on well-separated paths. The electrons can only be described collectively.”
Researchers from Austria and India have now discovered that some materials show very unusual behavior, when they are studied in the form of tiny crystals. This could now lead to new materials with tailor-made electronic and magnetic properties.
Material properties such as electrical conductivity, magnetic properties or the melting point do not de- pend on an object’s size and shape. “In India, ho- wever, an experiment recently showed that special manganese oxides – so called manganites – exhibit completely different properties, when their size is reduced to tiny grains”, Karsten Held explains. A
By changing their size, the properties of the manga- nite-crystals can now be harnessed. Larger crystals are insulators, and they are not magnetic. Tiny cry- stal pieces on the other hand turn out to be metallic ferromagnets.
“When data is read from a hard-drive with a rea- ding head, a transition between a conducting and a non-conducting state is used”, Karsten Held ex-