jueves, 24 de abril de 2008

Chemical Sensors and Nanotechnology


A single-walled carbon nanotube (SW-CNT) is a nano scale tube formed by a cylindricalshell of single atomic layer of carbon atoms. Nanotubes have diameter of a few nm andlength up to 100μm so that they form extremely thin wires. The atomic structure of SWCNTcan be formed by wrapping a stripe of single atomic layer of graphite sheet along acertain direction, and this direction determines the diameter and chirality of thenanotubes. Experimental and theoretical studies have found that these nano-meter sizedCNTs have novel electronic properties, which can be metallic or semiconducting,depending on their radius or chiralities. Nanotubes can be used as electronic wirebetween two metal electrodes as shown in Fig. 1, and the conductance between theelectrodes can be measured as a function of the gate bias voltage. Since the nanotubeelectronic property is a strong function of its atomic structure, mechanical deformations or chemical doping can induce strong changes in conductance. Such changes canbe easily detected by electron current signals, and these properties make CNTs extremelysmall sensors sensitive to their chemical and mechanical environments. In this paper, wepresent our theoretical and experimental studies on the subject of using SW-CNT aschemical and mechanical sensors.


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