Carbon nanotubes get nosy.They won't fetch the newspaper, but carbon-nanotube sensors might someday sniff out explosives with the same skill as our canine companions. Researchers have demonstrated that individual nanotubes, decorated with DNA DNA: see nucleic acid. DNA or deoxyribonucleic acid One of two types of nucleic acid (the other is RNA); a complex organic compound found in all living cells and many viruses. It is the chemical substance of genes. , can rapidly detect several gases. Carbon nanotubes make good sensors because their single layer of carbon atoms is available to interact with other molecules. When gas molecules come in contact with the nanotube A carbon molecule that resembles a cylinder made out of chicken wire one to two nanometers in diameter by any number of millimeters in length. Accidentally discovered by a Japanese researcher at NEC in 1990 while making Buckyballs, they have potential use in many applications. , they can pick up or donate electrons, which changes the charge on the nanotube. This, in turn, changes the amount of current that a nanotube can carry. But not all gases will interact with carbon, says A.T. Charlie Johnson, a physicist at the University of Pennsylvania (body, education) University of Pennsylvania - The home of ENIAC and Machiavelli. http://upenn.edu/. Address: Philadelphia, PA, USA. in Philadelphia. So, he and his colleagues adorned a·dorn tr.v. a·dorned, a·dorn·ing, a·dorns 1. To lend beauty to: "the pale mimosas that adorned the favorite promenade" Ronald Firbank. 2. some nanotubes with a layer of single-stranded DNA, which binds to more kinds of molecules than naked carbon does. The captured molecules can then interact with the nanotube. The modified tubes detected five gases, two of which bare tubes can't sense: the explosive dinitrotoluene and a derivative of the poison sarin sarin (zärēn`), volatile liquid used as a nerve gas. It boils at 147°C; but evaporates quickly at room temperature; its vapor is colorless and odorless. . The sensors, described in the September Nano Letters, picked up the scents in less than 10 seconds. Once a gas was removed, the sensors returned to their baseline current within 30 seconds. The team is now working to identify enough DNA sequences to create "a library of different strands that are sensitive to different odors Odors anosmia Medicine. the absence of the sense of smell; olfactory anesthesia. Also called anosphrasia. — anosmic, adj. halitosis bad breath; an unpleasant odor emanating from the mouth. ," Johnson says. Eventually, he notes, it may be possible to create an "electronic nose" by arraying a plethora of DNA-tailored carbon nanotubes on a microchip--an approximation of sensory cells in an animal's nose.--A.C. |
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