Sep 21 2010
Researchers at the Tel Aviv University are focusing on developing various processes for the identification and evaluation of explosives in order to prevent terror attacks and to determine the presence of hazardous materials in military systems.
The scientists at Tel Aviv University under the guidance of Fernando Patolsky are advancing an innovative sensor chip, which is capable of inspecting trinitrotoluene (TNT) and other major explosive materials, with high-performance. The Israel-based Tel Aviv’s scientists explained in Angewandte Chemie journal that their sensor works well when compared to sniffer dogs and various other conventional explosive identification methods.
The non-volatile nature of the explosives including TNT makes their detection a major issue. The prevailing air sample validation methodologies consumes more time, needs big equipments in large quantities, tedious sample preparation processes and specialists in the relevant field for performing the operations are highly expensive. According to Patolsky an easy, rapid and inexpensive tool which can execute reliable and sensitive operations in the specific area, is required.
The researchers designed the senors employing the standards of a nanosized field-effect transistor, which can be activated using an electric field. The central portion of the device is embedded with silicon semiconductor nanowires. These are inturn covered by a silicon compound containing molecular layer with amino (NH2) groups in it. The explosive TNT particles attach to these NH2 molecules, forming charge-transfer compounds. The attachment is mediated by the sharing of electrons from the electron-dense amino particles to the electron-deficient TNT molecules. This sort of change charge re-arrangement on the nanowire surface balances the electric field, resulting in a sudden change in the nanowire conductivity that can be calculated easily.
To enhance the signal-to-noise proportion and sensitiveness, the researchers fabricated the chips with a sequence of nearly 200 independent sensing units. Patolsky stated that by doing so they could validate the samples in both the liquid and gas states without the necessity of any sample preparation in the early stages. He remarked that they were able to measure the concentrations of even less than 0.1 ppt (parts per trillion) which is in the order of one TNT molecule per another ten quadrillion molecules. The sensor can be re-stored rapidly by simply washing it and the technique is implemented only for TNT molecules since other molecules of the same kind may not quickly regenerate by washing and is selective for TNT; other related molecules do not respond in the identical manner.
Patolsky said that they are recently developing a chip with a large sequence of chemically remodeled nanosensors, having various other binding capacities for the identification of an entire series of explosive materials.
Source: http://www.tau.ac.il